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It is strange to consider that sleep may be in some way essential for learning because sleep appears, to the normal eye, to be one of the few times when a person clearly could not be learning anything. Other times when learning seems impossible is when a person is unconscious, in a coma or dead. However, it seems that there is a great deal of evidence that sleep has to have evolutionary advantages and that most of those advantages turn out to be essential to all kinds of learning.
“It is a common experience that a problem difficult at night is resolved in the morning after the committee of sleep has worked on it.” John Steinbeck “Even a soul submerged in sleep is hard at work and helps make something of the world.” Heraclitus
The brain is in a constant state of tension between cells and chemicals that try to put you to sleep, and cells and chemicals that try to keep you awake. The longer you sleep the more likely these cells and chemicals will swing toward making you wake up. On the other hand the longer you stay awake the more these cells and chemicals will get stronger in trying to put you to sleep. From an evolutionary point of view sleep seems to have so many disadvantages that it seems unlikely that any advantage it may provide could be so great. In his book "Brain Rules" John Medina puts it like this: "Sleep makes us exquisitely vulnerable to predators. Indeed, deliberately going off to dreamland unprotected in the middle of a bunch of hostile hunters (such as leopards, our evolutionary roommates in eastern Africa) seems like a behavior dreamed up by our worst enemies. There must be something terribly important we need to accomplish during sleep if we are willing to take such risks in order to get it. Exactly what is so darned important?"
Lack of sleep is a severe disadvantage. When considering how sleep might be an evolutionary advantage we should all be aware that lack of sleep impairs all kinds of human abilities. Loss of sleep hurts attention, executive function, working memory, mood, quantitative skills, logical reasoning, and even motor dexterity. Sleep loss or sleep deprivation causes every part of our bodies and minds to falter and degrades all abilities and bodily functions. In his book "Why We Sleep" Matthew Walker puts it like this: "[These are] ...the many and varied ways in which insufficient sleep proves ruinous to all major physiological systems of the human body: cardiovascular, metabolic, immune, reproductive."
THE ADVANTAGE OF THREAT SIMULATION THEORY. Antti Revonsuo devised a Theory that would make sleep a very necessary part of our bodily survival strategies and a very strong and necessary brain mechanism that would make complete evolutionary sense. The following is an excerpt from Wicapedia: Revonsuo's threat simulation theory claims that much or all of dream experience is "specialized in the simulation of threatening events", for the evolutionary purpose of rehearsing fight or flight situations to better prepare for such instances in waking life (similar to a "fire drill"). According to Revonsuo, empirical research supports this theory by showing the recurrence of threatening situations in dreaming: of all of the emotions experienced in dreaming, "fear [is] the most common and anger the next most common". An otherwise supportive 2009 review of threat simulation theory stated that "The main weakness of the theory is that there is no direct evidence of the effect of dream rehearsal (or the lack of it) on performance or on survival rates across generations of ancestral humans", and also notes it is not clear why some threat simulations end without a reaction from the dreamer. The review finds that "Overall, the available new evidence and the new direct tests of the predictions of (threat simulation theory) yield strong support for the theory. A mass of evidence indicates that threat simulation is a function of dreaming, an evolved psychological adaptation selected for during the evolutionary history of our species. On current evidence, the strengths of the theory seem to outweigh its weaknesses." According to a 2017 study in Sleep, an analysis of the statistical content of intelligible sleep-talking found that 24 percent contained negative content, 22 percent had "nasty" language, about 10 percent contained a variation of the word "no", and 10 percent contained profanity. 2.5 percent of the intelligible words were a variation of the word "fuck", which comprised only 0.003 percent of spoken words when awake. The study authors judged the findings as being consistent with threat simulation theory. Cross-cultural surveys find that the most typical dream theme is that of being chased or attacked. Other common negative themes include falling, drowning, being lost, being trapped, being naked or otherwise inappropriately dressed in public, being accidentally injured/ill/dying, being in a human-made or natural disaster, poor performance (such as difficulty taking a test), and having trouble with transportation. Some themes are positive, such as sex, flying, or finding money, but these are less common than dreaming about threats. Revonsuo outlines six “empirically testable” propositions (Revonsuo, 2000) to illustrate his "threat simulation" theory.
Proposition 1 Dream experience embodies an “organized and selective simulation of the perceptual world.” Sensory modalities are fully integrated into perceptual dream experience, and the “active dream self” has a body image similar to that of the waking self in the “visuo-spatial world.” Dreams are composed of interactions that mimic archetypical wake-state experiences and situations with people and objects. Revonsuo states that dreams are the result of an “active and organized process rather than a passive by-product of disorganized activation.” The predicable organization of dreams renders them as more than “random noise”; rather, he views their function as a “selective simulation of the world.”
Proposition 2 Representations of daily life experiences are absent while dreaming. Dreamers experience a “selective simulation of the world” biased towards threatening situations. The high proportion of negative emotions experienced while dreaming correlates to the need for “adaptive responses that increase the ability to respond appropriately in adaptively important situations” (Revonsuo, 2000). The misfortunes and aggression experienced in a dream state may act as a simulation that prepares the dreamer in the case that a similar situation may occur in the awake state. Evidence lies in the activation during REM sleep across regions that are necessary for the production of these emotionally charged experiences.
Proposition 3 Real waking life experiences that are traumatic to the individual causes the dream-production system to create dream content that simulates responses to threats as a mechanism to "mark situations critical for physical survival and reproductive success." Revonsuo writes that "what from a psychological point of view is a 'traumatic experience' is, from a biological point of view, an instance of threat perception and threat-avoidance behavior."
Proposition 4 The threatening dream content, while not an accurate depiction of one's real-time experience, seems incredibly realistic and is therefore effective and productive practice for threat-avoidance responses. He postulates that there is proof of this proposition in that dreamed action is consistent with real motor behavior and that "dreaming about an action is an identical process for cortical motor areas as actually carrying out the same action."
Proposition 5 The perceptual and motor skills simulated in dreams will increase the efficiency of an individual's performance of those skills even if the dreams are not explicitly remembered. Studies have shown that the implicit learning of skills that are important for human performance can be learned and actualized without any conscious memory of having learned them. Furthermore, Revonsuo writes that "REM sleep physiology appears to selectively support implicit, procedural learning."
Proposition 6 The threat-simulation system "was selected for during our evolutionary history," implying that it was not innate but rather came to be in response to the multitude of threats experienced by human ancestral populations. These populations lived in a "more or less constant post-traumatic state" and the dreaming brain constructed the threat-simulation technique as an evolutionary tool, resulting in improved threat-avoidance skills and, thus, a higher probability of survival.
WHY ELSE MIGHT SLEEP PROVIDE AN EVOLUTIONARY ADVANTAGE? Almost all diseases and aberrant bodily functions are improved by sufficient sleep. With sufficient sleep there is less chance of cardiac arrests and less chance of any heart problem such as atherosclerosis. Normal sleep greatly lowers the chance of high blood pressure. With enough sleep there is far less chance of stroke and kidney failure. Lack of sleep effects both blood sugar and insulin levels causing them to be unregulated or irregularly regulated leading to such diseases as the various form of diabetes.
Obviously then, lack of sleep leads automatically to much greater weight gain and eventual obesity. Lack of sleep has also been found to correlate significantly with infertility. Sleep deprivation also correlates significantly with all disease and virus risk especially with all the common ones we all catch such as flus and the common cold. Also sleep deprivation also seems to increase the chances of all forms of cancer. Lastly and perhaps most importantly sleep deprivation seems to greatly shorten life expectancy.
Matthew Walker in his book "Why we sleep" explains that sleep is more than a pillar of good health. He says: "Sleep is more than a pillar; it is the foundation on which the other health bastions sit. Take away the bedrock of sleep, or weaken it just a little and careful eating or physical exercise become less than effective..."
After much scientific investigation over many years the most likely explanation of the main importance of sleep is not that it provides rest for the brain, which is amazingly active during most of our sleep cycle, but rather that it is somehow essential to learning. It is initially rather counter intuitive to be told that sleep is essential for learning, but there is some strong circumstantial and practical evidence. Thus we should not be surprised to learn that lack of sleep impairs the ability to learn, which it indeed does. Studies show that lack of sleep impairs cognitive skill. The loss of a single night's sleep can cause a 30 percent loss in overall cognitive skill, with a subsequent drop in performance. If this loss of sleep is increased to two nights and impairment of 60 percent of cognitive skill can result. But the question is what is all that brain activity that happens while we sleep? What are our brains doing that is so important? John Medina tells a funny story that provides a clue: "Consider the following true story of a successfully married, incredibly detail-oriented accountant. Even though dead asleep, he regularly gives financial reports to his wife all night long. Many of these reports come from the day's activities. (Incidentally, if his wife wakes him up - which is often, because his financial broadcasts are loud - the accountant becomes amorous and wants to have sex.) Are we all organizing our previous experiences while we sleep? Could this not also explain all the other data we have been discussing, but also finally give us a reason why we sleep?" NREM SLEEP AND THE RAT BRAIN. John Medina then goes on to explain about what happened to a rat that had been learning how to navigate mazes with 500 electrodes implanted in its brain. The rat fell asleep. This provided a unique opportunity for researchers to discover what goes on in a rat brain when it goes to sleep after just learning a new maze route. What they recorded was a pattern very similar to the pattern they recorded while the rat was awake and running through the maze. John Medina tells the story: "When the rat goes to sleep, it begins to replay the maze pattern sequence. The animal's brain replays what it learned while it slumbers, reminiscent of our accountant. Always executing the pattern in a specific stage of sleep, the rat repeats it over and over again - and much faster than during the day. The rate is so furious, the sequence is replayed thousands of times. If a nasty graduate student decides to wake up the rat during this stage, called slow wave sleep, something equally extraordinary is observed. The rat has trouble remembering the maze the next day. Quite literally, the rat seems to be consolidating the day's learning the night after that learning occurred, and an interruption of that sleep disrupts the learning cycle.
This naturally caused researchers to ask whether the same was true for humans. The answer? Not only do we do such processing, but we appear to do it in a far more complex fashion. Like the rat, humans appear to replay certain daily learning experiences at night, during the slow-wave phase. But unlike the rat, more emotionally charged memories appear to replay at a different stage of the sleep cycle. These findings represent a bombshell of an idea. Is it possible that the reason we need to sleep is simply to shut off the exterior world for a while, allowing us to divert more attentional resources to our cognitive interiors? Is it possible that the reason we need to sleep is so that we can learn?" It is now fairly well confirmed that replaying or recalling of memories of the previous day occurs during the slow wave period of sleep and that we experience them as a type of occurrence that could be classified as a dream. Although the scientific evidence for consolidation of memories is fairly recent the idea of sleep or dreaming being integral to memory consolidation is not new. The earliest known human record of such claims was in the writings of the Roman rhetorician Quintillian (AD 35-100), who stated: "It is a curious fact, of which the reason is not obvious, that the interval of a single night will greatly increase the strength of the memory... Whatever the cause, things that could not be recalled on the spot are easily coordinated the next day, and time itself, which is generally accounted one of the causes of forgetfulness, actually serves to strengthen the memory." People vary in how much sleep they need and when they prefer to get it, but the biological drive for an afternoon nap is universal and it is now well accepted that it can improve learning and all brain functions quite a bit. This sounds all well and good but unfortunately brain damaged people who lack the ability to sleep in the slow-wave phase nonetheless have normal and even improved memories as do people who have REM sleep suppressed by antidepressant medication. It may well be that while sleeping and dreaming may not be absolutely essential for memory it can still be possible that they are important for memory. Our bodies may simply be able to find other ways of reinforcing memories. We may have redundancy systems or be able to form new ways of consolidating memories when normal ones are not working.
NREM SLEEP Slow wave Non Rapid Eye Movement dreams. Sleep research has discovered that during slow wave sleep we have dream like states. However, whether we dream or not in NREM sleep may depend on our understanding of what dreaming is. We are familiar with dreams from REM sleep because we often remember them after waking during one. They seem to be a full sensory experience as we might experience when awake, and for the most part we cannot tell the difference between REM dreams and waking experience while we are dreaming. Rehearsal in NREM sleep, is it replay or recall? However, NREM dreams (for the most part) seem quite different. NREM dreams, as discovered by integrating subjects who have been awakened from the NREM dream state, seem to be more like thinking than experiencing. Thinking of course often involves recall, and this recall (for the most part) is not like actually experiencing the event in question. The replaying of memories that were imprinted from events that occurred the previous day may not actually occur during NREM sleep. Instead we appear to be simply recalling these events in much the same way we do while awake. However, looking back to our mice it seems that some form of rehearsal that consolidates memories is going on despite the fact that full replay is unlikely. If experiences were replayed just as they were experienced initially the person dreaming would be thrashing about trying to repeat the actions involved in these experiences. This does not happen however. We know that during REM sleep action schemas are activated and experienced but that during REM sleep we are paralyzed so we do not thrash about. However during slow wave sleep we are not paralyzed so these action schemas cannot be active. This seems to indicate that if memories are replayed during slow wave sleep then the activity schemas are not replayed as part of these memories. It seems we may have very little actual experience in these dream like NREM states and therefore very little memory of such experiences if we are awakened while in NREM sleep. Of course there are aberrant states which normally take place in slow wave or NREM part of the sleep cycle when humans do thrash about. These are variously known as sleep walking and sleep talking. As most humans do not experience sleep walking and talking they must be considered aberrations and not part of some evolutionary advantage. On the other hand reliving memories of previous experiences while awake does seem to occur sometimes and when they happen the memory is greatly consolidated. So there is a remote possibility that something similar sometimes occurs during NREM sleep. In her book "The Secret World of Sleep" Penelope Lewis points out that that some of the evidence that has been gathered about sleepwalkers actually supports the idea of rehearsal while in NREM sleep. She says: "A recent study of sleepwalking patients illustrated this [rehearsal] by showing that sleepwalkers, who are much freer in their movements during sleep than other people, often reenact things they did right before sleep, providing direct evidence for the off-line replay [rehearsal] of newly acquired information." The two functions of NREM dreams. The evidence gathered about these dream like occurrences and process seem to point toward there being two possible functions for slow wave (NREM) dream like states. One possible function seems to be the strengthening (reinforcing) of memories (by recalling the memory in our NREM sleep). At the same time during this phase of sleep a pruning of synapses takes place. So it is likely that the memories of the previous day that are not recalled (or replayed), or at least parts of them, are simply deleted. Thus during this period of sleep memories could be said to accessed by the brain and divided into two groups important memories and unimportant memories. The important memories are then recalled while we sleep and the unimportant memories are deleted. Of course it is more likely that this process does not occur over a single night. It might take several nights for the various synapses in a memory to shrivel up. The memory may not be deleted instantly but rather loose more and more potential to be recovered over several nights until it finally looses any potential to be recalled. Other synapses than the ones from the previous day may also be pruned away during this process. Sorting out which memories to delete and which to consolidate? How do our brains decide which memories should be suppressed or discarded and which should be consolidated? It turns out that there are several ways in which our brains seem to do this. We can make a conscious decision that a particular memory is important and your brain will take that into account while you sleep. Someone like your boss or your teacher may indicate that particular memories are important and you brain will take that into account also. However, the main way our brains decide this has to do with attention and focus and how they work to ensure our survival. It turns out that strong emotions can tag memories as important and thus likely to be consolidated while weak emotions tag memories as unimportant and unlikely to be consolidated. But there is a wrinkle to this. Strong emotions like fear hate and anger, in particular, also focus attention to such an extent that they suppress or ignore many of the mundane elements of an experience and thus streamline the memory of that experience. The Weapon focus effect. This is referred to as 'The Weapon Focus Effect' and is related to time dilation. It has to do with the allocation of resources used in mental processing. When we perceive that we are in danger and flight or fight is activated our brains tend to focus narrowly in on a small set of incoming sensory data and simply not process the rest of the incoming sensory data. (We focus on a weapon to the exclusion of anything else.) Because the brain is thus using far less of its processing resources it is able to process the small amount of data very fast. In other words our thinking speeds up and time seems to slow down. This obviously provides an evolutionary advantage where fast thinking and movement may save our lives. In this way strong emotions both make memories more likely to be consolidated but also can eliminate important elements of the experience. Conversely less strong emotions can thus be more inclusive while also being less likely to be consolidated. Sleep seems to double down on this. Penelope Lewis in her book "The Secret World of Sleep" explains it as follows: "After people sleep they not only remember the car crash better, they are also less likely to recognize the background street. It looks as though sleep while working to cement memories that are really important, may also need to pare down the less important ones, clearing space and resources for what matters." Reconsolidation. So why should replay or recall of memories tend to consolidate those memories? It does and it does not. When we recall a memory it is now believed that the memory becomes flexible and labile. In other words when we recall the memory from storage it becomes possible to change it or weaken it or delete it. If we then store away the memory again we are not so much consolidating it but rather reconsolidating it. This is important because we do not always want to consolidate a memory. Sometimes the memory we had previously learned was simply wrong and needs to be deleted. Sometimes a memory in storage turns out to be wrong and there is a better memory available to overwrite it and replace it. Sometimes the memory simply needs to be updated. It is not so much wrong as incomplete and new elements need to be added to it. I seems that by becoming labile a memory becomes so changeable that it can be deleted, overwritten or updated and not just consolidated. Recall while we sleep would work the same way but to greater extent. Some synapses are pruned away during NREM sleep leading to deleted memories. Some synapses are also strengthened during NREM sleep which could explain both overwriting and updating. It is well established that when a neuron is activated myelin builds up on its axon which makes the connection both stronger and quicker which would explain how recalling a memory might lead to it becoming more permanent. However, there may well be another way in which a memory might be both strengthened and changed. Maybe past memories also become labile and flexible when new memories are recalled, if the new memory contains elements also occurring in an old memory. Those parts of the new memory that also existed in an old memory would thus be further consolidated by being activated again. Or possibly only those elements occurring in both the old memories and the new may be recalled at all. The memories may have some elements strengthened while other elements in them are not strengthened. Or perhaps only those elements common to to both the old memory and the new memory may be recalled at all. It is also possible that synapses are striped away leaving only those elements that were common to both old and new memories. Information Overlap to Abstract. Penelope Lewis and Simon Durant developed a model as a possible explanation of how replaying memories during slow wave sleep, in combination with downscaling of synapses could function in unison called 'Information Overlap to Abstract'. In her book "The Secret World of Sleep" Lewis presents it as follows: "If more than one memory is replayed at the same time, the neurons associated with areas of shared replay or "overlap," will be more strongly activated than the other neurons... This means, for instance, if you replay memories of two or three different birthday partys, all of which involved cake, presents and balloons, but each of which was held at a different place and with a different set of guests, then responses in the neurons which code for cake, presents, and balloons will be stronger than responses associated with locations of individual parties or the people who attended them. Furthermore, based on the general principle that neurons which fire together wire together..., the linkages between neural representations of cake, presents and balloons will also become stronger than other linkages associated with these memories, such as between a specific birthday and her presents or other people who were at her party... All this strengthening is important because it means that when synapses are subsequently downscaled these representations of overlap may be the only thing that is retained. In fact, as multiple memories are replayed across a night, the more often a specific representation (say a birthday cake) or pair of representations (say, both cake and presents) is triggered, the more likely that specific aspect of a memory is to be retained." This process above may well be an explanation for the formation of concepts. Concepts would be formed by the elimination of information in memory that is not specific to all iterations of the concept. In the case above it would gradually form the concept of a birthday party. It also would as Penelope Lewis believes explain the formation of new semantic knowledge. She continues: "The realization that birthday parties are associated with cake, presents, and balloons is an example of the development of new semantic knowledge. Semantic knowledge is the general knowledge about the world and how things in it relate to each other. Classic examples of semantic knowledge are the knowledge that the sky is blue, that Paris is the capital of France, and for that matter that birthday parties normally include cake, presents, and balloons." Slow waves and electric potential. During this phase of sleep what we measure as slow waves is actually slow increases and decreases in potential occurring throughout the brain. It is likely that these slow changes ensure that complete memory patterns fire and not just bits of those patterns. This rise and fall of potential may also explain how memories are chosen to be recalled during NREM sleep. Memories that have already been rehearsed or replayed while we were awake would require less potential to be activated while we are asleep. Likewise memories that have greater emotion attached would also require less potential to be activated. Thus the potential may simply never get high enough to activate some memories. In his book "The Chemistry of Conscious States" J. Allen Hobson calls the above type of possible dream function 'consolidation' as in consolidating memories and consolidating knowledge out of data or information. Experimental findings about NREM sleep. In his book "Why We Sleep" Matthew Walker ran a number of experiments that relate learning to NREM sleep. He explains that during NREM sleep the brain is still active. NREM sleep seems to function to enhance memory of both facts and actions. Much has been discovered about this in sleep studies.
The function of sleeping before learning. In his book "Why We Sleep" Matthew Walker indicates there may be many things happening during slow wave or NREM sleep that both improve individual memories and also generally improve our ability to remember things we have experienced or recall bits of information we have previously been exposed to. Walker ran many experiments over the years many based on the his belief that the hippocampus is the site of short term memory and that the cortex is the site of long term memory. Now while this site does not hold that it is likely that memories are kept in storage areas there is no doubt that these two areas are very significantly concerned with memory. Regardless, Walker's experiments are well conducted and of obviously great importance. His first significant finding in the area sleep's effect on memory was dealing with the possibility of short term memory being a finite storage that might be improved by being emptied during sleep with memories being transfered to a less finite storage of long term memory. This experiment is reported in his book "Why We Sleep" as follows: "How then does the brain deal with this memory capacity challenge? Some years ago my research team wondered if sleep helped solve this storage problem by way of a file-transfer mechanism. We examined whether sleep shifted recently acquired memories to a more permanent long term storage location in the brain, thereby freeing up our short term memory stores so that we awake with a refreshed ability for new learning. We began testing this theory using daytime naps. We recruited a group of healthy young adults and randomly divided them into a nap group and a no-nap group. At noon all the participants underwent a rigorous session of learning (one hundred face-name pairs) intended to tax the hippocampus, their short term memory storage site. As expected both groups performed at comparable levels. Soon after the nap group took a ninety-minute siesta in the sleep laboratory with electrodes placed on their heads to measure sleep. The no-nap stayed awake in the laboratory and performed menial activities, such as such as browsing the Internet or played board games. Later that day, at 6 p.m., all participants performed another round of of intensive learning where they tried to cram yet another set of new facts into their short term storage reservoirs (another one hundred face name pairs). Our question was simple: Does the learning capacity of the human brain decline with continued time awake across the day and if so can sleep reverse this situation effect and thus restore learning ability? Those who were awake throughout the day became progressively worse at learning even though their ability to concentrate remained stable (determined by separate attention and response tests). In contrast, those who napped did markedly better, and actually improved in their capacity to memorize facts. The difference between the two at six p.m. was not small: a 20 percent learning advantage for those who slept. Having observed that sleep restores the brains capacity for learning, making room for new memories, we went in search of exactly what it was about sleep that transacted the restoration of benefit. Analyzing the electrical brainwaves of those in the nap group brought our answer. The memory refreshment was related to lighter stage 2 NREM sleep, and specifically the short, powerful bursts called sleep spindles... The more sleep spindles an individual obtained during the nap the greater the restoration of their learning when they woke up." [In other words a direct one to one correlation existed between the amount of sleep spindles and the improvement in learning ability of each subject.] A different interpretation of the experiment. This above is a beautiful well conducted experiment but this site holds that there may be a better way of interpreting the experiment's results. This site holds that it is more likely that memories are not kept in a single place like the hippocampus but rather each memory is more likely to be a vast network or web of connections scattered across many brain areas. So, rather that reducing the significance of this experiment this site holds that the experiment works even better if in the experiment memories are not moved from the hippocampus to the cortex but rather they are part of a path reconstruction involving the accessing of those memories. Although the experiment set out to find if memories were moved from the hippocampus to the cortex the findings of the experiment do not conclusively prove that such a movement of memory took place. Rather they prove that the memories are accessed through different pathways after NREM sleep. In her book "The Secret World of Sleep" Penelope Lewis an analogy gives some idea how the above might be possible: "The analogy [of memory recall] with music is actually quite useful, especially if you think of the cortex as a piano keyboard with different keys representing different sensory inputs. The keys are all there to be played all the time, but they only have noticeable impact when they are pressed, and only a few are pressed at any given time. If we think of the memory of running on the beach as a beautiful piece of music, a standard view of memory would suggest the score for this music is initially stored in the hippocampus which triggers to all of the piano keys (areas of the neocortex) in the correct order and with the correct timing to to produce the music." Elsewhere on this site the idea is presented that memories are created by neurons in the hippocampus connecting to all the areas active in the cortex at any one time. Similarly those same neurons could activate the same areas of the cortex that were active at the time of memory storage to recall a memory. They would do this by means of the many neurons that link the hippocampus to every part of the cortex. Thus what could be stored in the hippocampus would not be memories as such but rather small programs to play memories. The memories are actually anywhere until they are played when they exist momentarily in the cortex.
REMEMBERING & NREM SLEEP. The function of sleeping after learning. Which provides memory enhancement sleeping or waking? In 1924 two German scientists John Jenkins and Karl Dallenbach showed conclusively for the first time that that humans remembered far more after sleeping than they did if they remained awake: Walker refers to the study as follows: "Their study participants first learned a list of verbal facts Thereafter, the researchers tracked how quickly the participants forgot those memories over an eight hour interval, either spent awake or across a night of sleep. Time spent asleep helped cement the newly learned chunks of information, preventing them from fading away, an equivalent time spent awake was deeply hazardous to recently acquired memories resulting in an accelerated trajectory of forgetting." These experimental results have been replicated may times with a memory retention benefit of between 20 and 40 percent as compared to the same time spent awake. Sleep greatly out performs staying awake. During what stage of sleep is memory enhanced NREM or REM? In the 1950's the first experiments were carried out to discover when and in what stages of sleep this memory improvement was taking place. Walker describes the study as follows. "After having learned lists of facts, researchers allowed participants the opportunity to sleep only for the first half of the night. In this way, both experimental groups obtained the same total amount of sleep (albeit short), yet the former group's was rich in deep NREM, and the latter was dominated instead by REM... For fact based, textbook-like memory, the result was clear. It was early night sleep rich in deep NREM that won out in terms of providing superior memory retention savings relative to to late-night, REM-rich sleep. Investigations in the early 2000s, arrived at a similar conclusion using a different approach. Having learned a list of facts before bed, participants were allowed to sleep a full eight hours, recorded with electrodes placed on the head. The next morning the participants performed a memory test. When the researchers correlated the intervening sleep stages with the number of facts retained the following morning, deep NREM sleep carried the vote: the more deep NREM sleep, the more information an individual remembered the next day. Indeed, if you were a participant in such a study, and the only information I had was the amount of deep NREM sleep you had obtained that night, I could predict with high accuracy how much you would remember in the upcoming memory test upon awakening, even before you took it. That's how deterministic the link between sleep and memory consolidation can be. [Factual memory enhancement occurs in NREM sleep.]
Using MRI scans we have since looked deep into the brains of of participants to see where those memories are being retrieved from before sleep and after sleep. It turns out that those information packets were being recalled from very different locations within the brain at the two different times. Before having slept, participants were fetching memories from the short term storage site of the hippocampus..." This statement seems to contradict some of what this site holds to be true. However, here Walker is interpreting areas that are lit up on MRIs and could merely be showing a lack of activity in the hippocampus after a good night's sleep and the threads from the hippocampus to the cortex lighting up before and during sleep. He goes on to say: "But things were very different by the next morning. The memories had moved. After a full night of sleep participants were now receiving that same information from the neocortex..." The neocortex is the area of the brain just below the cortex and it connects various parts of the cortex together. This site holds that the connections in the neocortex make up memories in the same way as in the hippocampus. However the connections from the hippocampus to the cortex preexist and the ones in the neocortex have to be developed by the emergence of new synapses. This may sometimes happen overnight as seems to be the case here or it may sometimes take a long while as with very complicated memories connecting parts of the brain that are very far apart. Walker continues: "Sleep is constantly modifying the information architecture of the brain at night. Even daytime naps as short as twenty minutes can offer a memory consolidation advantage, so long as they contain enough NREM sleep."
Walker has looked at many many sleep studies young kid participants, adolescent participants, midlife participants, and 40-60 year old participants and all their memories improved with deep NREM sleep. Walker continues like this: "At every stage of human life, the relationship between NREM sleep and memory solidification is therefore observed. It's not just humans either. Studies in chimpanzees, bonobos, and orangutans have demonstrated that all three groups are better able to remember where food items have been placed in their environments after they sleep. Descend down the plylogenetic chain to cats, rats, and even insects, and the memory-maintaining benefits of NREM sleep remains on powerful display." Walker created many other experiments with much longer and more varied sequences and obtained a similar result each time. Walker goes on to enlighten us about further findings in the same experiments above: "Perhaps more remarkable as we analyzed the sleep-spindle bursts of activity we observed a strikingly reliable loop of electrical current pulsing throughout the brain that repeated every 100 to 200 milliseconds. The pulses kept weaving a path back and forth between the hippocampus with its short-term limited storage space, and the far larger long-term storage site of the cortex." What if the the loop of current traveling between the hippocampus and the cortex was merely an indication that the memory in question was being activated by means of links connected to the hippocampus. Further suppose that after a goodnight of NREM sleep the same memory was activated by means of connections in the cortex. It would not be necessary for the memory to move at all. The only thing that would need to change would be the way in which the memory was activated. Suppose during the night a path of synapses through the cortex, that already connected the memory in question, was somehow made more likely than the connection though the hippocampus. This may seem like a lot of 'what ifs' and 'supposition' and but it would free up pathways to and from the hippocampus to the cortex to be freed up to form new memories that are separate from the existing ones. Why would the brain need two ways of reaching a memory? This is likely for the same reason that computers often have a number of different ways of doing the same thing. Redundancy in any system is always a plus. But the experiments by Walker and his team were of huge importance because they proved conclusively that something happens during NREM sleep that enables participants to form new memories that can be easily recalled, at least in the short term. As Walker concludes: "Participants awoke with a refreshed capacity to absorb new information..." Matthew Walker then goes on to discuss another similar experiment his team performed later. They tested elderly people counting the number of spindles that occurred while they slept and then gave them similar learning experiences to those in the experiment above and then tested their retention to see if there was a correlation between the spindles and their ability to learn. Again this turned out to be the case. A lack of spindles before trying to memorize led to a proportional inability to recall. Matthew Walker sums up a whole range of experiments like these as follows: "If you were a participant in such a study and the only information that I had was the amount of deep NREM sleep you had obtained that night, I could predict with high accuracy how much you would remember in the upcoming memory test upon awakening, even before you took it. That's how deterministic the link between sleep and memory consolidation can be." Matthew Walker continues then indicating that before having slept the greatest amount of MRI recorded activity was taking place in the the subjects hippocampus while after NREM sleep the MRI recorded activity took place mostly in cortex areas. Walker concludes that this means that memories are being moved from the hippocampus (short term memory) to the cortex (long term memory). However it is just as possible that the memories did not move at all but rather what changed was the manner in which they were accessed. SELECTIVE FORGETTING & NREM SLEEP. The function of initiating selective forgetting. In his book "Why We Sleep" Matthew Walker set about creating an experiment to determine if humans had any kind of conscious control over the process of embedding some memories in a more accessible and more permanent form while deleting or making other memories less accessible. He describes this experiment as follows: "We designed an experiment that again used daytime naps. At midday, our research subjects studied a long list of words presented on the screen, however, a large green "R" or a large red "F" was displayed, indicating to the participant that they should remember the prior word (R) or forget the prior word (F). It is not dissimilar to being in a class and, after being told a fact, the teacher impresses upon you that it is especially important to remember that information for the exam, or instead that they made an error and the fact was incorrect, or the fact will not be tested on the exam, so you don't need to worry about remembering it for the test. We were effectively doing the same thing for each word right after learning, tagging it with the label 'to be remembered' or 'to be forgotten.'
Half of the participants were then allowed a ninety-minute afternoon nap, while the other half remained awake. At 6 p.m. we tested everyone's memory for all the words. We told participants that regardless of the tag previously associated with a word - to be remembered or to be forgotten - they should try to recall as many words as possible. Our question was this: Does sleep improve the retention of all words equally or does sleep obey the waking command only to remember some items while forgetting others, based on the tags we had connected to each?
The results were clear. Sleep powerfully, yet very selectively, boosted the retention of those words previously tagged for 'remembering' yet actively avoided the strengthening of those memories tagged for 'forgetting.' Participants who did not sleep showed no such impressive parsing and differential saving of the memories. ...sleep does not offer a general, nonspecific (and hence verbose) preservation of all the information you learn during the day. Instead, sleep is able to offer a far more discerning hand in memory improvement: one that preferentially picks and chooses what information is to ,and is not , ultimately strengthened. Sleep accomplishes this by using meaningful tags that have been hung on those memories during initial learning, or potentially identified during sleep itself. Numerous studies have shown a similarly intelligent form of of sleep-dependent memory selections memory selection across both daytime naps and a full night of sleep. When we analyzed the sleep records of those individuals who napped, we gained another insight. Contrary to Francis Crick's prediction, it was not REM sleep that was sifting through the list of prior words, separating out those that should be retained and those that should be removed. Rather, it was NREM sleep, and especially the very quickest of the sleep spindles that helped bend apart the curves of of remembering and forgetting."
Walker and his team performed many other experiments. A good number of such experiments produced results that showed that specific memories could be made more likely to be remembered by inducing replay of those specific memories during NREM sleep. GENERAL RECALL IMPROVEMENT BY MEANS OF ELECTRICAL BRAIN STIMULATION IN NREM SLEEP. Electrical stimulation. Just as a computer hard drive often has some files that have become corrupted and inaccessible, the human brain also has memories that become partially damaged or inaccessible. In a brain this means that either the pathways to the memory or the pathways that make up the memory have withered through disuse or have been physically damaged. This is nothing new for the brain as most recall seems to require the brain to reconstruct memories from the clues left behind. It is also well known from memory studies that recalling memories just before they are to be forgotten or when these connections are weakening will cause the memory to be revitalized as the connections are reinforced, consolidated and or rebuilt. It is likely then that during NREM dreams that memories are recalled in a similar manner with synapses being both strengthened and or reconstructed.
Since sleep is expressed in patterns of electrical brain wave activity it occurred to some researchers that it might be possible to increase the amount of recall the brain was doing by flooding the brain with small electrically charged pulses that are synchronized with the slow waves of deep NREM sleep. Walker describes the study as follows: "In 2006 a research team in Germany recruited a group of healthy young adults for a pioneering study in which they applied electrodes pads onto the head, front and back. Rather than recording the electrical brainwaves being emitted from the brain during sleep the scientists did the opposite: inserted small amounts of electrical voltage. They patiently waited until each participant had entered into the deepest stages of NREM sleep and, at that point, switched on the brain stimulator, pulsing in rhythmic time with the slow waves. The electrical pulsations were so small that participants did not feel them, nor did they wake up. But they had a measurable impact on sleep.
Both the size of the slow brainwaves and the number of sleep spindles riding on top of the the deep brainwaves were increased by the stimulation, relative to a control group of subjects who did not receive stimulation during sleep. Before being put to bed, all the participants had learned a list of new facts. They were tested the next morning after sleep. By boosting the electrical quality of deep-sleep brainwave activity, the researchers almost doubled the number of facts that individuals were able to recall the following day, relative to those participants who received no stimulation." GENERAL RECALL IMPROVEMENT BY MEANS OF OTHER BRAIN STIMULATION IN NREM SLEEP. Sound stimulation. Walker goes on to describe a number of other methods of stimulation that have been stimulate these same deep-sleep brainwaves as follows: "One technology involves quiet auditory tones being played over speakers next to the sleeper. Like a metronome in rhythmic stride with the individual slow waves, the tick-tock tones are precisely synchronized with the individual's sleeping brainwaves to help entrain their rhythm and produce deeper sleep.
Relative to a control group that slept but had no synchronous auditory chimes at night, the auditory stimulation increased the power of the slow brainwaves and returned an impressive 40 percent memory enhancement the next morning.
Walker goes on to warn people not to try to do this at home as safe technologies are not available and it is easy to cause yourself damage trying to synchronize brainwave with either electrical pulses or sound pulses.
It may well be that even without individual slow waves becoming synchronized with a sound that simply paying a piece of music on a loop all night after studying with that piece of music playing may also produce good recall the next day as seems to be the case with odors in the experiment below. Odor simulation. Other research suggests that memory reactivation can be biased by external cues presented during NREM sleep that had been present during prior encoding. The researchers, used odor cues to trigger memory reactivation processes during sleep in humans. Participants were asked to encode locations of picture pairs shown on a computer screen (similar to the game concentration), while they smelled the scent of roses. During subsequent slow wave sleep participants were re-exposed to this odor or an odorless alternative. Those participants who had smelled the odor during learning and during slow wave sleep showed increased recall of the card locations at retrieval compared to the alternative condition. Memory was not improved if participants received the odor only during sleep but not during prior encoding, and odor re-exposure was also not effective during wakefulness and post-learning REM sleep. Movement or rocking simulation. Following experiments on mice yet another type of stimulation was tried to influence these deep-sleep brainwaves and so increase memory retention or recall as Walker summarizes here: "[A]...Swiss research team recently suspended a bedframe on ropes from the sealing of a sleep laboratory... Affixed to one side of the suspended bed was a rotating pulley. It allowed the researchers to sway the bed from side to side a controlled speeds. Volunteers then took a nap in the bed as researchers recorded their sleeping brainwaves. In half the participants, the researchers gently rocked the bed once they entered NREM sleep. In the other half of the subjects the bed remained static, offering a control condition. Slow rocking increased the depth of deep sleep, boosted the quality of slow brainwaves, and more than doubled the number of sleep spindles. It is not known whether these sway induced sleep changes enhance memory, since the researchers did not perform any such tests with their participants. Nevertheless the findings offer a scientific explanation for the ancient practice of rocking a child back and forth in one's arms, or in a crib, inducing deep sleep."
Of mice and men. The other experiment was described at another site as follows: "The second study in mice by other researchers is the first to explore whether rocking promotes sleep in other species. And, indeed, it did. The researchers used commercial reciprocating shakers to rock the cages of mice as they slept.
While the best rocking frequency for mice was found to be four times faster than in people, the researchers' studies show that rocking reduced the time it took to fall asleep and increased sleep time in mice as it does in humans. However, the mice did not show evidence of sleeping more deeply." SPECIFIC RECALL IMPROVEMENT BY MEANS OF SENSORY BRAIN STIMULATION IN NREM SLEEP. Clearly Walker had shown that memories could be improved by various types of external simulation during sleep but these all improved memories as a whole address the idea that people might like to control which memories are forgotten and which are remembered. Of sounds and specific items to recall. and Just suppose you could decide what items you wished to be able to recall and be able to place your order before you go to sleep. Next morning you would awake to find you can recall the items you specified and not any other items on a list that where you learned the ones specified. An experiment has been performed that indicates it may be possible to move memory research in that direction. Walker explains as follows: "Before going to sleep, we show participants pictures of objects at different spacial locations on a computer screen, such as a cat in the lower right side, or a bell in the upper center, or a kettle near the top right of the screen. As a participant you have to remember not only the individual items you have been shown, but also their spacial location on the screen. You will be shown a hundred of these items. After sleep, picture objects will again appear on the screen, now in the center, some of which you have seen before, some you have not. You have to decide if you remember the picture object or not, and if you do you must move that picture object to the spacial location on the screen where it originally appeared using a mouse.
But here is the intriguing twist. As you were originally learning the images before sleep, each time an object was presented on the screen a corresponding sound was played. For example, you would hear 'meow' when the cat picture was shown, or ding-a-ling when the bell was shown. All picture objects are paired, or 'auditory-tagged,' with a semantically matching sound. When you are asleep and in NREM sleep specifically, an experimenter will will replay half of the previously tagged sounds (fifty of the total hundred) to you sleeping brain at low volume using speakers either side of the bed. As if helping guide the brain in a targeted search-and-retrieve effort, we can trigger the selective reactivation of corresponding individual memories, prioritizing them for sleep strengthening, relative to those that were not reactivated during NREM sleep.
When you are tested the following morning, you will have a quite remarkable bias in your recollection, remembering far more of the items that we reactivated during sleep using the sound cues than those not reactivated. Note that all one hundred of the original memory items passed through sleep. However using sound cuing, we avoid indiscriminate enhancement of all that you have learned. Analogous to looping your favorite song in a repeating playlist at night, we cherry pick specific slices of your autobiographical past and preferentially strengthen them by using the individualized sound cues during sleep." It seems clear that what is happening is the sound cues are causing the sleeping NREM deep-sleep brains to recall specific memories. As we well know memories recalled automatically direct our brains to prioritize memories for placement in long term memory. The likelihood of recall is then greatly increased. It seems possible that almost any sound could be associated with the pictures in the above experiment and the experiment would still produce positive results. This is using the same principle as as Pavlov in his classical conditioning only it triggers the memory during NREM sleep instead of while the subject is awake. Obviously though, the use of sounds that are already linked to or associated with the pictures guaranteed that the experiment would work well. One
can imagine whole study sessions at schools and colleges having
specific music played while they are studying a specific topic and the
giving each student a copy of the music to take home that night so they
can replay the music quietly while they are in NREM sleep. This could
produce startling exam results at exam time especially if the music was
played during NREM sleep the night before the exam.
Overnight improvement. On awakening, I could just do it. Walker tells the story of being approached by a pianist who's remarks set him on a path to creating experiments to study this possibility. Walker relates the those remarks as follows: "He said he was intrigued by my description of sleep as an active brain state, one in which we may renew and even strengthen those things we have previously learned. Then came a comment that would leave me reeling and trigger a major focus of my research for years to come. 'As a pianist' he said 'I have an experience that seems too frequent to be chance. I will be practicing a particular piece, even late into the evening, and I cannot seem to master it. Often, I make the same mistake at the same place in a particular movement. I go to bed frustrated. But when I wake up the next morning and sit back down at the piano, I can just play perfectly.'" Walker was faced with the idea that perhaps practice alone was not sufficient to create improvement in a skill. Perhaps improvement was only possible with a combination of practice plus sleep. Gradually Walker envisioned and created a number of experiments that would eventually seem to confirm all the pianist's intuitions. The first experiment of this sort is explained by Walker as follows:
"I took a large group of right handed individuals and had them learn to type a number sequence on a keyboard with their left hand, such as 4-1-3-2-4 as quickly and as accurately as possible. Like learning a piano scale, subjects practiced the motor skill sequence over and over again, for a total of twelve minutes, taking short breaks throughout. Unsurprisingly, the participants improved in their performance across the the training session; practice after all, is supposed to make perfect. We then tested the participants twelve hours later. Half of the participants had learned the sequence in the morning and were tested later that evening after remaining awake across the day. The other half of the subjects learned the sequence in the evening and we retested them the next morning after a similar twelve hour delay, but one that contained a full eight-hour night of sleep. Those who remained awake across the day showed no evidence of a significant improvement in performance. However, fitting with the pianist's original description, those who were tested after the same delay of twelve hours, but spanned a night of sleep, showed a striking 20 percent jump in performance speed and a near 35 percent improvement in accuracy. Importantly, those participants who learned the motor skill in the morning - and who showed no improvement that evening - did go on to show an identical bump in performance when retested after a further twelve hours, now after they, too, had had a full night's sleep. In other words, your brain will continue to improve skill memories in the absence of further practice." It seems that while some improvement was possible with practice alone a far greater improvement was obtainable with the addition of a good night's sleep. Not only that but fluidity and accuracy were also improved with sleep. Walker goes on to say: "Their typing post sleep, was now fluid and unbroken. Gone was the staccato performance, replaced by seamless automaticity which is the ultimate goal of learning..." Skills are both created and improved by sleep. In other words the pianist's intuitions were completely born out. What seems to be happening is that while we are sleeping in a NREM state our brains are carefully weaving together disparate uncoordinated action elements into a fully coordinated smooth flowing skill. Or an already acquired skill is being woven together with newly learned action elements to create a far improved skill that is even better coordinated.
Skill learning and & NREM sleep. In his book "Why We Sleep" Matthew Walker goes on to show that not only can fact learning be improved by the intervention of NREM sleep but also that habits, skills and the smooth flow of automatic actions are also created and improved by NREM sleep. Ultimately Matthew Walker tested many of the subjects of the experiments dealing with motor skill enhancement (explained above) to find out what was happening in the subject's brains while they slept. He explains what he found: "My final discovery, in what spanned almost a decade of research, identified the type of sleep responsible for the overnight motor-skill enhancement, carrying with it societal and medical lessons. The increases in speed and accuracy, underpinned by efficient automaticity, were directly related to the amount of stage 2 NREM, especially in the last two hours of an eight-hour night of sleep (e.g., from five to seven a.m., should you have fallen asleep at eleven p.m.). Indeed it was the number of those wonderful sleep spindles in the last two hours of the late morning - the time of night with the richest spindle burst of brain wave activity - that were linked with the off line memory boost." "More striking was the fact that the increase of those spindles after learning was detected only in regions of the scalp that sit above the motor cortex (just in front of the crown of your head), and not in any other areas. The greater the local increase in sleep spindles over the part of the brain we had forced to learn the motor skill exclusively, the better the performance on awakening... Perhaps more relevant to the modern world is the time-of-night effect we discovered. Those last two hours of sleep are precisely the window that many of us feel it is okay to cut short to get a jump start on the day." REM SLEEP
Rapid Eye Movement dreams. The father of dream research was want to say: "Dreaming permits each and every one of us to be quietly and safely insane every night of our lives." He said this of course because the main dreams that we remember, although they sometimes seem to be logical while we are experiencing them, are actually very illogical, with transitions and connections that appear to be completely random. This site holds to the idea that perhaps we need to be crazy every night. If repetition is so important, why do we spend so much time dreaming illogical dreams while we are asleep? As expressed elsewhere this site is unconvinced that repetition alone is the way in which memories are consolidated. Paralysis. Another feature of REM dreams is the fact that during such dreams we become paralyzed. While in other stages of sleep we can toss and turn and move about. But during REM sleep we are paralyzed, and for good reason. We are in a highly emotional state (intense emotions, especially of fear, rise and fall chaotically), we are hallucinating (in that we are seeing hearing things that are not in the real world) and we are just plain crazy. On top of that, during this sleep stage all the schemas or action programs become available to run. If we were not paralyzed we would be running, jumping, dancing, fighting and doing god knows what. In his book "The Chemistry of Conscious States" J. Allen Hobson explain it like this: "The motor programs in the brain are never more active than during REM sleep! As our dreams make clear, REM sleep entails a frenzy of action - we run, we drive, we fly, we swim. There is no rest in REM sleep for the central programs that move us about by day. On the contrary, they are souped up and we assume for good reason: to prevent their decay from disuse, to rehearse for their future actions when called on during waking, and to embed themselves in a rich matrix of meaning.
Sometimes an aberration occurs where people wake from REM sleep, but remain paralyzed for a while, unable to move. This experience may be accompanied by residual dream elements, delusions involving people or things to be feared. This also may be accompanied by returning feelings of panic and dread. It seems likely that one function of this type of dreaming might be the the strengthening of these action programs by running many of them without any movement taking place, spinning our wheels (so to speak) while we sleep. This is what Revonsuo's threat simulation theory is all about. Think about it. Many of our dreams concern the fight or flight response. Keeping programs concerned with fight or flight in good working order would have important evolutionary consequences.
Early stage REM dreams. During the early stages of REM sleep we also appear to have dreams that more closely resemble the replaying of experiences or memories from the previous day and other fairly recent memories. These mixed bits of replays are woven into dreams that tend to be longer in duration than slow wave recall, and like all dreams make little rational sense. This site holds that these dreams occurring early REM sleep may be a another type of memory consolidation or reinforcement. This site has always held that the main way in which memories are consolidated is through elaboration. In other words it is not the repetition itself that enables consolidation of memories, but rather the new connections that are included during the iteration, that makes the difference. While we are awake we imprint sensory information as memories but we are not immediately able to comprehend or understand such information completely. Initially the information connects with only a limited amount of the other data stored already in our minds. The dreams that occur in this early stage of REM sleep may be our brains consolidating memories in a manner that is far superior to mere replay. We may be making connections to the memory from all the other similar or logically connectible information in our brains. These numerous extra connections would make memories both more understandable and more easily accessed. In this way we may be building a mental map of what we need to understand or learn and indeed solve problems.
Stitching information into our map of knowledge in our sleep. While we sleep and during the early stages of REM sleep our brains may well be integrating new information with the old information building a structure that fits it all together. What research has shown clearly is that after sleep information is not only better remembered but better understood or comprehended and more able to be put to use solving our trickiest problems. This is consistent with our brains constructing mental maps or maps of reality. In her book "The Secret World of Sleep" sleep researcher Penelope Lewis puts it like this: "The answer appears to be that sleep does a lot more than strengthen individual memories. It is also involved in the complex process of integrating new information with old and abstracting out general principals or rules which describe a corpus of events and help us to make informed predictions about the future." "Taken together these studies demonstrate that sleep is important for combining information from multiple sources. It helps us to extract statistical regularities, pull out general principles, integrate new information with older knowledge structures and piece together a larger picture from a set of interrelated fragments." In his book "The Chemistry of Conscious States" J. Allen Hobson suggests that there may be three different ways in which both early and latter stages of REM sleep may use dreaming to integrate new information with older information in our minds, and in doing so turn it into knowledge: [Distribution, Hyperassociation and Proceeduralization.] I call these additional memory processes distribution, hyperassociation and proceduralization." [Knowledge permanence and stability.] "The representation of the memory in neuronal networks could be made more secure by its simultaneous distribution to other networks." [Knowledge versatility and understanding.] "It could be made more versatile by linking it in hyperassociative fashion to every network with which it shares formal features (such as axles with long things, hard things, strong things)." [Knowledge
usefulness and
interconnectedness.] "It could be made more useful if
it were
linked to procedures that it served (such as weight bearing, prying). "Dreaming has several features that could enhance all...of these functions... For the memory redistribution function, REM sleep provides a massive, widespread activation with intense reiterative stimulation of all the cortical circuits of the brain. For the hyperassociative function, REM sleep provides the coactivation of newly sensitized circuits and all those circuits previously endowed with the multiple interconnections necessary for category overinclusiveness. For the proceduralization function, REM sleep provides automatic running of motor programs that give the data access to existing action files." Constructing a map of reality in our sleep. J. Allen Hobson goes on to speculate as to how this might all fit together as follows: "When we find ourselves in a new place, we at once begin to develop orientational schemas. We build up our brain-mind maps by incorporating the results of exploring the environment and moving through it, while at the same time sniffing it, hearing it, and feeling its textures. This leads us to an important question that is tougher than it looks: How can we most efficiently and effectively assure the orientational experience we perceive gets built into our system? In addition, how can we be sure that if a built in procedure isn't used, it doesn't get lost? One way would be to have a state (waking) in which we are exposed to new information and another state (REM sleep) in which the new data is integrated with the whole set of existing programs in the system. For that to happen, we would need to run the system automatically for a considerable length of time each day (say one and a half hours, the usual grand total of REM sleep for a night); we would want to run it fast (say six procedures a second, the usual rate of PGO wave signals); we would want to run it with the clutch disengaged (so the system does not have to output); and we would want to run it in an altered chemical climate (to favor a set of molecular operations that differs from that in waking, to encode long-term memory). That's a tall order. But it's all done reliably, efficiently and unconsciously in REM sleep, mother of all procedures. We are performing mental gymnastics, using motor programs to train our brain each time we dream... These startling dream enactments...are so full of meanings... that REM sleep must be preparing us for almost any possible waking eventuality. The programs are all there. Life's events call them forth. And most of the time, they otherwise stay put." Latter stage REM dreams. However, we may also require completely illogical connections to memories, or in other words random connections. Penelope Lewis says: "Dreams occur at all stages of sleep, but they seem to become increasingly fragmented as the night progresses. ...REM dreams that occur late in the night are typically much more bizarre and disjointed." [This sort of illogical elaboration, like logical elaboration, would provide more pathways though which each memory could be accessed.] If a need for random connections could be established it would explain illogical dreams, it would explain their illogical nature and it would be consistent with the above research on the replaying of previous experiences for the purpose of consolidating learning. It is possible we have both kinds of nightly experiences. It would be possible to have nightly replays of waking experiences with perhaps random connections thrown in, or the waking experiences could be chopped up and reconnected randomly to produce chaotic dream like experiences. In this way recent waking experiences could be activated in concert with other random waking experiences to form new connections between clumps of knowledge at random. The random chaos of dreams and creation. The question then would be why would the brain need random connections? The answer might be quite simple. One possibility is, that for every part of the brain to be connected, it may require that some of the connections are illogical. Another more likely possibility is that all creative activity, including problem solving, hunches and incite, need random or chaotic connections to function. Without dreams it may be impossible to be original and creative. In his book "Where Good Ideas Come From" Steven Johnson puts it like this: "There is nothing mystical about the role of dreams in scientific discovery. While dream activity remains a fertile domain for research, we know that during REM sleep acetylcholine-releasing cells in the brain stem fire indiscriminately, sending surges of electricity billowing across the brain. Memories and associations are triggered in a chaotic, semirandom fashion, creating the hallucinatory quality of dreams. Most of those new neuronal connections are meaningless, but every now and then the dreaming brain stumbles across a valuable link that has escaped waking consciousness. In this sense, Freud had it backward with his notion of dreamwork: the dream is not somehow unveiling a repressed truth. Instead, it is exploring, trying to find new truths by experimenting with novel combinations of neurons." In her book "The Secret World of Sleep" sleep researcher Penelope Lewis shows that random brain stem firings cannot fully explain dreams because most dreams, especially those occurring earlier in the night, tend to have logical threads running through them, and are sometimes persistent in reoccurring. Nevertheless, it may well be, that random brain stem firing is responsible for the chaotic nature of REM dreams occurring later in the night. In any case Lewis agrees that the chaotic structure of latter dreaming may well determine creativity. She explains it this way: "Although we don't quite understand how dreams achieve this type of innovative recombination of material, it seems clear that the sleeping brain is somehow freed of constraints and can thus create whole sequences of free associations. This is not only useful for creativity, it is also thought to facilitate insight and problem solving. It may even be critical for the integration of newly acquired memories with more remote ones... In fact, this facilitated lateral thinking could, in itself, be the true purpose of dreams. It is certainly valuable enough to have evolved through natural selection." These random connections could be understood to produce occasional errors in thought that in turn produce crazy ideas from which we can mine useful novel ideas. Without these chaotic dreams thoughts may get stuck in ruts with no escape route. Experimental findings about REM sleep. In his book "Why We Sleep" Matthew Walker also ran a number of experiments that relate learning to REM sleep. For a start he explains that during REM sleep the brain is very active. He points out that MRI studies show four sections of the brain are particularly active during REM sleep as follows: "(1) the visuospacial regions at the back of the brain, which enable complex visual perception... (2) the motor cortex, which instigates movement... (3) the hippocampus and surrounding regions...which support autobiographical memory... (4) the deep emotional centers of the brain - the amygdala and the cingulate cortex, a ribbon of tissue that sits above the amygdala and lines the inner surface of your brain - both of which help to generate and process emotions..."
REM DREAMS DECODED. This information is consistent with dreams that are visual, active, biographical, and highly emotional but not inconsistent with dreams that are illogical and randomly chaotic. As should have also been expected certain other brain areas were found during REM sleep to be disconnected and suppressed. Walker explains: "What came as a surprise, however, was the pronounced deactivation of other brain regions - specifically, circumscribed regions of the far left and far right sides of the prefrontal cortex. ...these neural territories had become markedly suppressed in activity during the otherwise highly active state of REM sleep... This region...manages rational thought and logical decision making... [and] otherwise maintains your cognitive capacity for ordered logical thought..."
From these findings Walker and his staff were able to predict some of the general content of dreams which they were then able to check by waking and asking the subjects what they were dreaming about. By the extent of activity in each of the four areas they were able to predict how emotional the dreams were, how much activity was involved, how connected or chaotic it was, and much visual information was being processed. THE CONTENT OF DREAMS. It is important to note that the content of dreams has long been thought difficult or impossible to predict from brain scans that were taken during the dreaming. However, it may well be possible to predict rudimentary elements in dreams from brain scans. This allows researchers to have some idea of what the dream content of a dreamer may be without having to resort to waking the dreamer and asking them. "In 2013, a research team in Japan led by Dr. Yukiyasu Kamitani at the Advanced Telecommunications Research Institute International in Kyoto, found an ingenious way to address the question. They essentially cracked the code of an individual's dream for the very first time and, in doing so, led us to an ethically uncomfortable place. Individuals in the experiment consented to the study - an important fact as we shall see. The results remain preliminary, since they were obtained in just three individuals. But they were highly significant. Also the researchers focused on the short dreams we frequently have just at the moment when we are falling asleep, rather than the dreams of REM sleep, though the method will soon be applied to REM sleep.
The scientists placed each participant into an MRI scanner numerous times over the course of several days. Every time the participant fell asleep, the researchers would wait for a short while as they recorded the brain activity, and then wake the person up and obtain a dream report. They would let the person fall back to sleep, and repeat the procedure. The researchers continued to do this until they had gathered hundreds of dream reports and corresponding snapshots of brain activity from their participants. An example of of one of the dream reports was: 'I saw a big bronze statue...on a small hill, and below the hill there were houses, streets, and trees.' Kamitani and his team then distilled all the dream reports down into twenty core content categories that were most frequent in the dreams of these individuals, such as books, cars, furniture, computers, men, women,and food.
The scientists were able to
predict with significant accuracy the content of participant's dreams
at any one moment in time using just the MRI scans, operating
completely blind to the dream reports of the participants. Using the
template data from the MRI images , they could tell if you were
dreaming of a man or a woman, a dog or a bed, flowers or a knife.
There has been some expectation that researchers should find daytime experiences being reexperienced during REM sleep as a kind of reinforcement of those experiences. This turns out not to be the case. While it seems that very short elements of such experience occur during NREM sleep very little repetition of waking experience occurs during REM sleep. In his book "Why We Sleep" Matthew Walker goes on to document the findings of Robert Stickgold who undertook to discover if a significant amount of REM dream content concerned replay of previous waking autobiographical experiences. He describes Stickgold's experiment as follows: "For two weeks straight, he had twenty-nine healthy young adults keep a detailed log of daytime activities, the events they engaged in (going to work, meeting specific friends, meals they ate, sports they played, etc.) and their current emotional concerns. In addition he had them keep dream journals, asking them to write down any recalled dreams that they had when they awoke up each morning. He then had external judges systematically compare the reports of the participants' waking activities with their dream reports, focusing on the degree of similarity of well-defined features such as locations, actions, objects, characters, themes, and emotions. Of a total of 299 dream reports that Stickgold collected from these individuals across fourteen days, a clear rerun of prior waking life events - day residue - was found in just 1 or 2 percent... But Stickgold did find a strong and predictive daytime signal in the static of nighttime dream reports: emotions. Between 35 and 55 percent of emotional themes and concerns that participants were having while they were awake during the day powerfully and unambiguously resurfaced in the dreams they were having at night." Basically it was clear that NREM dreams were where actions and facts were selected for storage or deletion (by being recalled or not), while REM dreams were where emotions were explored. While it is possible that these highly emotional dreams perform functions like preparing us for unknown situations and solving problems this was not what Walker and his team decided to investigate initially. The
functions of REM sleep and
dreams.
While thinking about the old adage "Time heals all wounds." Walker wondered if this might only be true if sleep was involved. He wondered if REM sleep might be performing overnight therapy to allow the dreamer to be able to deal with harsh emotions. Maybe REM dreams replayed emotions so they remained in memory as knowledge but without the experiencing of toxic, traumatic emotions. Firstly he may have discovered or maybe it was all ready well known that (as he explains): "Concentrations of a key stress-related chemical called noradrenaline are completely shut off within your brain when you enter this dreaming sleep state. In fact REM sleep is the only time during the twenty-four hour period when your brain is completely devoid of this anxiety-triggering molecule. Noradrenaline, also known as as norepinephrine, is the brain equivalent of to a body chemical you already know and have felt the effects of: adrenaline (epinephrine)." Walker then goes on to speculate what this lack of noradrenaline might mean: "I therefore wondered whether the brain during REM sleep was reprocessing upsetting memory experiences and themes in this neurochemically calm (low noradrenaline), 'safe' dreaming brain environment. Is the REM-sleep dreaming state a perfectly designed soothing balm - one that removes the emotional sharp edges of our emotional lives? It seemed so from everything neurobiology and neurophysiology was telling us (me). If so we should awake feeling better about distressing events of the day(s) prior.
This was the theory of overnight therapy. It postulated that the process of REM-sleep dreaming accomplishes two critical goals: (1) sleeping to remember the details of those valuable, salient experiences, integrating them with existing knowledge and putting them into autobiographical perspective, yet (2) sleeping to forget, or dissolve, the visceral, painful emotional charge that had previously been wrapped around those memories."
The idea was that just as the emotional intensity of memories does in fact subside as time goes bye. (You can (as you know) accurately relive memories without experiencing the intense visceral emotions, the toxic pain and mental anguish originally embedded in them.) There had to be a reason why it happens and a process that explained how it happens. Walker goes on: "The theory argued that we have REM-sleep dreaming to thank for this palliative dissolving of emotion from experience. Through its therapeutic work at night, REM sleep performed the elegant trick of divorcing the bitter emotional rind from the information rich fruit. We can therefore learn and usefully recall salient life events without being crippled by the emotional baggage that those painful experiences originally carried." So Walker and his team designed an experiment to test this theory and discover its viability: "We recruited a collection of healthy young adults and randomly assigned them to two groups. Each group viewed a set of emotional images while in an MRI scanner as we measured their emotional brain reactivity. During these two exposure sessions separated by twelve hours, participants also rated how emotional they felt in response to each image. Importantly, however, half the participants viewed the images in the morning and again in the evening, being awake between the two viewings. The other half of the participants viewed the images in the evening and again the next morning after a full night of sleep. In this way we could measure what their brains were objectively telling us using the MRI scans, and in addition, what the participants themselves were subjectively feeling about the relived experiences, having had a night of seep in between or not.
Those who slept in between the two sessions reported a significant decrease in how emotional they were feeling in response to seeing those images again. In addition, results of the MRI scans showed a large and significant reduction in reactivity in the amygdala, that emotional center of the brain that creates painful feelings. Moreover, there was a reengagement of the rational prefrontal cortex of the brain after sleep that was helping maintain a dampening brake influence on emotional reactions. In contrast, those who remained awake across the day without the chance to sleep and digest those experiences showed no such dissolving of emotional reactivity over time. Their deep emotional brain reactions were just as strong and negative, if not more so, at the second viewing compared to the first, and they reported a similar powerful reexperiencing of painful feelings to boot. Since we had recorded the sleep of of each participant during the intervening night between the two test sessions, we could answer a follow-up question: Is there something about the type or quality of sleep that an individual experiences that predict how successful sleep is at accomplishing the next-day emotional resolution?
As the theory predicted, it was the dreaming state of REM-sleep - and specific patterns of electrical activity that reflected the drop in stress related brain chemistry during the dream state - that determined the success of overnight therapy from one individual to the next. It was not, therefor, time per se that healed all wounds, but instead it was time spent in dream sleep that was providing emotional convalescence. To sleep, perchance to heal." Walker had proved his theory, in that clearly REM sleep provided some benefit in lowering toxic emotional experiences in relived memories while retaining the useful knowledge in those memories. But how could depression and PTSD be explained or how did they fit with this theory?
"Cartwright demonstrated that it was only those patients who were expressly dreaming about the painful experiences around the time of the events [that caused the depression] who went on to gain clinical resolution from their despair, mentally recovering a year later as clinically determined by having no identifiable depression. Those who were dreaming, but not dreaming of the painful experience itself, could not get past the event, still being dragged down by a strong undercurrent of depression that remained.
Cartwright had shown that it was not enough to have REM sleep, or even generic dreaming, when it comes to resolving our emotional past. Her patients required REM sleep with dreaming, but dreaming of a very specific kind: that which expressly involved dreaming about emotional themes and sentiments of the walking trauma. It was only that content specific form of dreaming that was able to accomplish clinical remission and offer emotional closure in these patients, allowing them to move forward into a new emotional future, and not be enslaved by a traumatic past." PTSD and the theory of overnight therapy. Walker started conjecturing possibilities about PTSD: "I wondered whether the REM-sleep overnight therapy mechanism we had discovered in healthy individuals had broken down in people suffering from PTSD, thereby failing to help them deal with their trauma memories effectively... Most compelling to me, however, were the repetitive nightmares reported in PTSD patients - a symptom so reliable that it forms part of the list of features required for diagnosis of the condition.
If the brain cannot divorce the emotion from memory across the first night following the trauma experience, the theory suggests that a repeat attempt of emotional memory stripping will occur on the second night, as the strength of the 'emotional tag' associated with the memory remains too high. If the process fails a second time, the same attempt will continue to repeat the next night, and the next night, like a broken record. This was precisely what appeared to be happening with the recurring nightmares of the trauma experience in PTSD patients.
A testable prediction emerged: If I could lower the levels of noradrenaline in the brains of PTSD patients during sleep, thereby reinstating the right chemical conditions for sleep to do its trauma therapy work, then I should be able to restore healthier quality REM sleep. With that restored REM-sleep should come an improvement in the clinical symptoms of PTSD, and further, a decrease in the frequency of painful repetitive nightmares. It was a scientific theory in search of clinical evidence."
"At the conference Raskind presented recent findings that were perplexing to him. In his PTSD clinic, Raskind had been treating his war veteran patients with a drug called prazosin to manage their high blood pressure. While the drug was somewhat effective in lowering blood pressure in the body Raskind found it had a far more powerful yet entirely unexpected benefit within the brain: it alleviated the reoccurring nightmares in his PTSD patients. After only a few weeks of treatment, his patients would return to the clinic and, with puzzled amazement, say things like, 'Doc its the strangest thing, my dreams don't have those flashbacks nightmares any more. I feel better, less scared to fall asleep at night.'"
It turns out that the drug Prazosin, which Raskind was prescribing simply to lower blood pressure, also had the fortuitous side effect of suppressing noradrenaline in the brain. Raskind had delightfully and inadvertently conducted the experiment I was trying to conceive of myself. He had created precisely the neurochemical condition - a lowering of the abnormally high concentrations of stress-related noradrenaline - within the brain during REM sleep that had been absent for so long in in these PTSD patients."
Reading body language and facial expressions. During our waking daytime experience we take in sensory data or information. It seems that during the night while we sleep this information is somehow connected to what we already know and in being so connected becomes what we call knowledge. This knowledge is critical in being able to predict what to do in various scenarios. The most important part of this knowledge is being able to predict other humans or as it is sometimes called "theory of mind". Walker and his colleagues began to wonder if REM sleep might play a part in the function of this theory of mind. One of the first types of learning they tested was our ability to read facial expressions and determine human intentions. Our ability to predict outcomes and the probabilities of likely future events dealing with many types of dangers is contingent on our ability to correctly interpret various emotional expressions in other humans and animals. Here is what Walker and his team did: "Participants came to my laboratory and had a full night of sleep.The following morning we showed them many pictures of a specific individuals face. However no two pictures were the same. Instead the facial expression of that one individual varied across the images in a gradient, shifting from friendly (with a slight smile, calming eye aperture, and approachable look) to increasingly stern and threatening (pursed lips, a furrowed brow, and a menacing look in the eyes). Each image of this individual was subtly different from those on either side of it on the emotional gradient, and across tens of pictures, the full range of intent was expressed, from very prosocial (friendly) to strongly antisocial (unfriendly).
Participants viewed the faces in a random fashion while we scanned their brains in an MRI machine, and they rated how approachable or threatening the images were. The MRI scans allowed us to measure how their brains were interpreting and accurately parsing the threatening facial expressions from the friendly ones after having had a full night of sleep. All the participants repeated the same experiment, but this time we deprived them of sleep, including the critical stage of REM. Half the participants went through the sleep deprivation session first, followed by the sleep session second, and vice versa. In each session, a different individual was featured in the pictures, so there was no memory or repetition effects.
Having had a full night of sleep, which contained REM sleep, participants demonstrated a beautifully precise tuning curve of emotional face recognition, rather like a stretched out V shape. When navigating the cornucopia of facial expressions we showed them inside the MRI scanner, their brains had no problem deftly separating one emotion from another across the delicately changing gradient, and the accuracy of their own ratings proved this to be similarly true. It was effortless to disambiguate friendly and approachable signals from those intimating even minor threat as the emotional tide changed toward the foreboding. Confirming the importance of the dream state, the better the quality of REM sleep form one individual to the next across that rested night, the more precise the tuning within the emotional decoding networks of the brain the next day. Through this platinum-grade nocturnal service, better REM-sleep quality at night provided superior comprehension of the social world the next day." Unlike many of the other experiments Walker presents in his book, this one does not pin down how REM sleep might might function to help decode waking experiences and the experiment does not prove that it does. It does, however prove that a lack of REM sleep will definitely cause this function to deteriorate. Walker continues: "But when those same participants were deprived of sleep, including the essential influence of REM sleep, they could no longer distinguish one emotion from another with accuracy. The tuning V of the brain had been rudely pulled all the way up from the base and flattened into a horizontal line, as if the brain was in a state of generalized hypersensitivity without the ability to map gradations of emotional signals from the outside world. Gone was the precise ability to read giveaway clues in another's face. The brain's emotional navigation system had lost its true magnetic north of directionality and sensitivity: a compass that otherwise guides us toward numerous evolutionary advantages. With the absence of such emotional acuity, normally gifted by by the re-tuning skills of REM sleep at night, the sleep-deprived participants slipped into a default of fear bias, believing even gentle - or somewhat friendly looking faces were menacing. The outside world had become a more threatening and adverse place when the brain lacked REM - untruthfully so. Reality and perceived reality were no longer the same in the 'eyes' of the sleepless brain. By removing REM sleep we had quite literally, removed participants' levelheaded ability to read the social world around them." Walker does not try to speculate why REM sleep would be able to help us interpret emotional signaling. However, Hobsen's ideas on the possibility of REM dreams integrating new information to become more permanent and stable, more variable and understandable, more useful and interconnected, could offer such an explanation. Unfortunately Walkers experiments do not try to implicate such functions or test these ideas. This site is well aware that many brain and bodily functions deteriorate if we do not get enough sleep. The brain may simply function badly in general if we do not get enough REM sleep.
In his book "Why We Sleep" Matthew Walker set out to show that REM dreaming enables creativity in a number of different ways. He suggests that these dreams enable creativity in several similar but distinct ways that serve very different creative functions. One function creates new and unique ideas by squishing bits of unrelated memory together while another solves problems by mixing random memory elements with the problem to see if any of it produces some possible hint of a solution. Or dreams may place the problem in various unconnected but similar or metaphorically compatible contexts. Creative ideas dreamed in REM sleep. While it would be impossible to create a study to show that sleeping and dreaming produce creative ideas and invent new creative works, there is, however, a great deal of anecdotal evidence to suggest that this is indeed the case. There is much evidence of people going to sleep and when awakening remember something from a dream that is a totally unique or novel idea. Perhaps the most famous dreamed idea was the periodic table of elements. Mendeleev after pondering the chemical properties of various elements for many days finally wakened from a dream with the solution mostly intact. He explains as follows: "I saw in a dream a table where all the elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper. Only in one place did a correction latter seem necessary." Matthew Walker tells the story of Otto Loewi: "Loewi dreamed of a cleaver experiment on two frogs' hearts that would ultimately reveal how nerve cells communicate with each other using chemicals (neurotransmitters) released across tiny gaps that separate them (synapses) rather than direct electrical signaling that could happen if they were physically touching each other. So profound was this dream that it won Loewi a Nobel Prize." Walker gives many other examples especially from artists and musicians. He explains Paul McCartney credits both 'Yesterday' and 'Let It Be' as songs that came to him in dreams and that Keith Richards recounts how 'Satisfaction' came to him in a dream. Also Penelope Lewis in her book "The Secret World of Sleep" has this to say about it: "This process has lead to the creation of many works of literature, art and science, such as Mary Shelly's Frankenstein the molecular formula of benzene, and the invention of the lightbulb. An especially good demonstration of somnolent creativity comes from a study of 35 musicians who not only hear more music in their dreams than the normal man-on-the-street but also reported that much of this (28 percent) was music they had never heard in waking life. They had created new music in their dreams." This of course is all circumstantial evidence that what is happening in dreams is functionally to enable creativity but there a massive profusion of it attested to by many of the greatest scientists, artist and thinkers that humanity has produced. For more examples see this site's page on social creativity.
The other possibility is more like problem solving where a person goes to sleep with a number of facts that seem incompatible or contradictory, but on awakening has an intuition or an idea that just pops into their head, that some how brings all those facts into a new theory that is completely internally consistent. It suddenly explains any seeming contradictions and smooths all the facts into being completely compatible.
This is often called a eureka moment which is widely considered to be the sudden gaining new knowledge out of nowhere. In reality this creative insight usually happens over a long period of time. Each day we gather new information and each night as we dream and that information is integrated into an ever expanding personal knowledge. The eureka moment itself is simply the last piece of the puzzle falling into place and forming an entirely new theory. This theory has been growing in the unconscious for some time and as it is completed it all becomes conscious. This often takes the form of old knowledge and new information where the new information is in conflict or dissonant with the older knowledge. The resolution of this conflict or dissonance could be carried out by the formation of random new connections and the strengthening of already existing connections to produce new correlations and synthesis which ultimately become new solutions, creative ideas and theories. Brain processes that may induce REM dreaming and resulting creativity. There is the evidence (as explained by Steven Johnsson above) that during the REM state the whole brain is bombarded by waves of random electrical pulses radiating from the lowest part of the brain the brainstem. In her book "The Secret World of Sleep" Penelope Lewis describes two theories of how dreams may be generated in the brain and result in creativity. The first theory, the activation-synthesis model. The first is a theory by Allan Hobson and Bob McCarly called the activation-synthesis model. She explains this theory as follows: "This draws on knowledge to propose that dreams are generated in precisely the way described... [neurons firing in the various areas of the brain that deal with vision, hearing, (any sensory areas) and the movement area.] It turns out that chaotic firing of neurons in the brainstem is a core characteristic of REM sleep. Because these brainstem neurons communicate with the neocortex, their chaotic firing could trigger responses in the primary sensory and motor areas. The activation-synthesis model proposes that brain may combine and synthesize these neocortical responses to create a story." The following is from Wikapedia: "Neural activity during REM sleep seems to originate in the brain stem, especially the pontine tegmentum and locus coeruleus. REM sleep is punctuated and immediately preceded by PGO (ponto-geniculo-occipital) waves, bursts of electrical activity originating in the brain stem. (PGO waves have long been measured directly in cats but not in humans because of constraints on experimentation; however comparable effects have been observed in humans during "phasic" events which occur during REM sleep, and the existence of similar PGO waves is thus inferred.) These waves occur in clusters about every 6 seconds for 1–2 minutes during the transition from deep to paradoxical sleep. They exhibit their highest amplitude upon moving into the visual cortex and are a cause of the "rapid eye movements" in paradoxical sleep. Other muscles may also contract under the influence of these waves." Penelope Lewis in her book "The Secret World of Sleep" gives some further hints about what is known, from various studies, to be happening in the brain during PGO waves and REM sleep. She says: "Even though they [various neocortical areas] combine together to make up a complete memory, these various neocortial areas may not be directly interlinked. Instead the hippocampus keeps track of such connections and forms the appropriate linkages, at least while the memory is relatively fresh. However, communications between the neocortex and the hippocampus is disrupted during sleep so this process is disrupted. During REM sleep, both the hippocampus and those parts of the neocortex which are involved in a current dream are strongly active - but they don't appear to be in communication. Instead, responses in the neocortex occur independently, without hippocampal input, so they must relate to memory fragments rather than linked multi sensory representations. Essentially, when memories that have been stored in the neocortex are accessed or activated during REM, they remain fragmentary instead of drawing in other aspects of the same memory to form a complete episodic replay."If we examine Hobson's later ideas in relation to these random pulses we can guess that the random elements being randomly inserted into REM dreams by these pulses might be the very process of creation that brings about knowledge stability, knowledge understanding, and knowledge usefulness. [Knowledge permanence and stability.] By strengthening all existing connections these brain pulses during REM sleep could stabilize the new information by integrating it into the old knowledge and making it less likely to be forgotten. [Knowledge versatility and understanding.] By also making new connections or reinforcing old but weak connections all the old knowledge the brain pulses during REM sleep could integrate the new information with that old knowledge with which it shared formal features thus making new knowledge that is both understandable and versatile. [Knowledge usefulness and interconnectedness.] By forging random, procedural, metaphorical, or analogous connections between the new information and all the old knowledge during REM sleep the brain could actually be creating entirely new knowledge that could be solutions to problems that need solving, solutions to problems that could emerge in the future or be entirely new theories about the world. In other words this could produce creativity of every sort. The second theory, the brain mechanisms of dreaming. The second theory is by Mark Solms called the brain mechanisms of dreaming. Lewis explains this theory as follows: "His [Solms] work suggests that the brain's reward system, which originates in the midbrain and connects through the ventromedial prefrontal cortex as it projects upward to the rest of the brain, provides the basis for dreams. Lesions to the ventromedial prefrontal region dramatically disrupt this system." [People with such lesions lose the ability to dream.] Although Solms has shown that this ventromedial forebrain area of the brain is clearly essential for the creation of dreams his theory does not explain the more chaotic elements and the sudden random transitions in dreams. So this site holds that it is likely that both theories are correct and do not have to conflict with one another. The PGO waves from the brainstem could create disjunctions while the ventromedial forebrain fights to place some order and narrative sequence between those disjunctions. The following is an excerpt from Wikapedia: "A mounting body of evidence suggests that dreaming and REM sleep are dissociable states, and that dreaming is controlled by forebrain mechanisms. Recent neuropsychological, radiological, and pharmacological findings suggest that the cholinergic brain stem mechanisms that control the REM state can only generate the psychological phenomena of dreaming through the mediation of a second, probably dopaminergic, forebrain mechanism."
Memory melding in the furnace of dreams. Each night during REM sleep our brains create new small ideas by fusing new information, gained during our awake time, with previous knowledge in storage. Sometimes these ideas come to us as intuitions the next day or some time later. Often, however, they do not surface as intuitions for a long while. Instead, they sit quietly in our unconscious minds being stitched together into a quilt like greater whole each night during REM sleep. Eventually when they are fully formed they appear, as if from nowhere, as a big idea creative insight.
How do we know that any of the above could be true? The problem with finding out what is happening in the brain when it is asleep is the fact that it is asleep. We cannot report what is going on because we would have to be awake to do so. Walker explains that his colleague Robert Stickgold designed a solution to this problem albeit an indirect and imperfect one. Here is what they did: "I [previously] described the phenomenon of sleep inertia - the carryover of the prior sleeping brain state into wakefulness in the minutes after waking up. We wondered whether we could turn this brief window of sleep inertia to our experimental advantage - not by waking subjects up in the morning and testing them, but rather by waking individuals from different stages of NREM sleep and REM sleep throughout the night. By restricting the length of whatever cognitive test we performed to just ninety seconds, we felt we could wake individuals and very quickly test them in this transitional sleep phase. In doing so, we could perhaps capture some of the functional properties of the sleep stage from which the participant was woken, like capturing the vapors of an evaporating substance and analyzing those vapors to draw conclusions about the properties of the substance itself. It worked. We developed an anagram task in which the letters of real words were scrambled. Each word was composed of five letters and the anagram puzzles had only one correct solution (e.g., 'OSEOG' = 'GOOSE'). Participants would see the scrambled words one at a time on the screen for just a few seconds, and they were asked to speak the solution, if they had one, before the time ran out and the next anagram word puzzle appeared on the screen. Each test session lasted only ninety seconds, and we recorded how many problems the participants correctly solved within this brief inertia period. We would then let the participants fall back asleep. The subject had the task described to them before going to bed in the sleep laboratory with electrodes placed on the head and face so that I could measure the their sleep unfolding in real time on the monitor next door. The participants also performed a number of trials before getting into bed, allowing them to get familiar with the task and how it worked. After falling asleep, I then woke the subjects up four time throughout the night, twice from NREM sleep and early and late in the night, twice from REM sleep, also early and late in the night. Upon awakening from NREM sleep, participants did not appear to be especially creative, solving few of the anagram puzzles. But it was a different story when I woke them from REM sleep from the dreaming phase. Overall, problem solving abilities rocketed up, with participants solving 15 to 35 percent more puzzles when emerging from REM sleep compared with awakening from NREM sleep or during daytime waking performance! Moreover, the way in which participants were solving the problems after exiting from REM sleep was different from how they solved both when emerging from NREM sleep and while awake during the day. The solutions simply 'popped out' following the awakenings from REM sleep, one subject told me, though at the time, they did not know they had been in REM sleep just prior. Solutions seemed more effortless when the brain was being bathed by the afterglow of dream sleep. Based on response times, solutions arrived more instantaneously following a REM sleep awakening, relative to the slower, deliberative solutions that came when the same individual was exiting NREM sleep or when they were awake during the day." So we finally have some empirical evidence that links creativity with REM sleep and dreams. But this is just the beginning. Robert Stickgold examined the way in which our stores of related concepts (semantic knowledge) are linked together by associations and wondered whether these paths we usually use in searching our memories might be bypassed or disrupted by the dreaming process to form or prioritize more random or distant links (creative ones). He designed another experiment to test this idea: "Using a standard computer test, Stickgold measured how these associative networks of information operated following NREM sleep and REM sleep awakenings, and during standard performance during the waking day. When you wake the brain from NREM or measure performance during the day, the operating principles of the brain are closely and logically connected, just as pictured..."
This tree represents the normal close connections between concepts that grow out like untangled threads. Walker continues: "However, wake the brain up from REM sleep and the operating algorithm was completely different. Gone is the hierarchy of logical associative connection. The REM sleep dreaming brain was utterly uninterested in bland, commonsense links - the one-step-to-the-next associations. Instead, the REM sleep brain was shortcutting the obvious links and favoring very distantly related concepts. The logic guards had left the REM-sleep dreaming brain. Wonderfully eclectic lunatics were now running the associative memory asylum. [Waking] From the REM-sleep dreaming state, almost anything goes - and the more bizarre the better the results suggested." The results seemed to insist that during REM sleep connections were being made or reinforced that were no longer being constrained by logic, similarity or being obvious. On the contrary, in the REM dreaming state the brain become actively biased toward seeking out the most distant, non obvious links in networks and between the concepts in those networks. Matthew Walker had clearly shown there was empirical evidence that REM dreaming was strengthening the most distant links in brains and in doing so was initiating creativity.
But Walker wanted to prove that if a waking brain was fed the various elements of a problem and then entered a REM dream state, the novel connections prioritized by the REM state should provide suitable solutions on being wakened. This conjecture was made testable by a study designed by a colleague Jeffery Ellenbogen. He used simple premises like A>B and B>C the idea was to test if the relationship between A and C could be derived i.e. = A>C: "...we taught participants lots of these individual premises that were nested in a large chain of interconnections. Then we gave them tests that assessed not just their knowledge of these individual pairs, but also assessed whether they knew how these items connected together in the associative chain. Only those who had slept and obtained late-morning REM sleep, rich in dreaming, showed evidence of linking the memory elements together (A>B>C>D>E>F, etc.), making them capable of the most distant associative leaps (e.g., B>E). The very same benefit was found after daytime naps of sixty to ninety minutes that also included REM sleep."
Clearly the dreaming REM sleep state was building connections between distantly related informational elements. As Walker says: "Our participants went to bed with disparate pieces of the jigsaw puzzle and woke up with the puzzle complete." This is the difference between the retention of individual facts (informational knowledge) and knowing what they all mean when fitted together (integrated knowledge) (a mental map) or (cognitive structure).
But what about the deriving of real insight where the brain creates overarching knowledge and super-ordinate concepts out of sets of information. This inspired insight is most frequently observed in infants abstracting complex grammatical rules in a language they must learn. It is most noticeable when they get it wrong as when in English there are exceptions that do not follow the rules.
It turns out that a study could be devised that could test if this creative insight is in fact generated during REM dreaming causing both insight in dreams that are remembered and more invisible insight that simply pops out following REM dreaming on awakening. The study in question was designed by Dr. Ullrtich Wagner of Germany and consisted of participants working through hundreds of miserably laborious number-string problems. Waker's description of the study is presented here again from his book "Why We Sleep": "You will be told that you can work through these problems using specific rules that are provided at the start of the experiment. Sneakily what researchers do not tell you about is the existence of a hidden rule, or shortcut that, common across all the problems. If you figure out this embedded cheat, you can solve many more problems in a far shorter time. I'll return to this shortcut in just a minute. After having had participants perform hundreds of these problems, they were to return twelve hours later and once again work through hundreds more of these mind-numbing problems. However, at the end of this second test session the researchers asked whether the subjects had cottoned on to the hidden rule. Some of the participants spent the twelve-hour time delay awake across the day while for others, that time window included a full eight-hour night of sleep. After time spent awake across the day, despite the chance to consciously deliberate on the problems as much as they desired, a rather paltry 20 percent of participants were able to extract the embedded shortcut. Things were very different for those participants who had obtained a full night sleep - one dressed with late with late-morning REM-rich slumber. Almost 60 percent returned and had the 'ah-ha!' moment of spotting the hidden cheat - which is a three fold difference in creative insight afforded by sleep!"
As Walker points out it is little wonder that we are never told to stay awake and work on a problem. Instead we are told to "sleep on it". This is not only true for English but also some similar saying occurs in most other languages.
Revelations from REM dreams. Clearly, when we are in REM sleep our brains are skillfully positioning our recent biographical experiences (new information) within the various contexts of our past accomplishments and experiences, and so building a rich amalgam of new knowledge. This new knowledge is exemplified by how that new information is related to those past experiences, making them thus more understandable. It seems as if our brains are taking these new biological experiences and probing how they intersect with past knowledge to relate together to produce solutions, to both existing problems, and problems that do not at present exist.
Solutions and understanding. Therefore it seems that part of the function of REM dreams is to make new information understandable by connecting it to old knowledge, and making old knowledge more understandable by connecting it to the new information. In addition REM dreams are miraculously creating solutions to current problems and squirreling away possible answers to problems that might or might not eventuate in the future. In his book "Why We Sleep" Matthew Walker explains it as follows: "REM sleep, and the act of dreaming, takes that which we have learned in one experience setting and seeks to apply it to others stored in memory."
Speculations on how REM dreams function. We can only guess how the brain might perform such miraculous feats but the most obvious is that it simply tries to fit new information into random past remembered contexts and awaits whatever connections might be generated and thus whether new knowledge is generated. Or the brain might be selective, selectively trying contexts that are very distantly related and stem from similarity, analogy or metaphor. These include all the various types of relations between concepts or ideas such as familial, genealogical, mathematical, functional or procedural relationships. This site's guess is that probably both of these are true.
Creation from REM dreams. We can also see that totally new knowledge that refutes or contradicts existing knowledge could also be generated in this manner. Such knew knowledge could include new speculation, new conjecture and totally new theories not to mention totally new combinations of forms that create totally new works of art, music, and craftsmanship.
The content of each dream matters. It might seem obvious that the content of each dream has a function and a purpose but scientists need to prove it. After all in the past people believed that dreams predicted the future. Not surprisingly Walker wanted to prove, beyond a shadow of a doubt, that it was the content of those dreams that was making the difference and not just the dream state itself that was causing the creativity. He explains how this was managed: "Though such a claim has long been made, it took the advent of of virtual reality for us to prove as much... Enter my collaborator Robert Stickgold, who designed a clever experiment in which participants explored a computerized virtual reality maze. During the initial learning session, he would start participants off from different random locations within the virtual maze and ask them to navigate their way out through exploratory trial and error. To aid their learning Stickgold placed unique objects, such as a Christmas tree, to act as orientation or anchor points at specific locations within the virtual maze.
Almost a hundred research participants explored the maze during the first learning session. Thereafter, half of them took a ninety minute nap, while the other half remained awake and watched video, all monitored with electrodes placed on their heads and face.
Throughout the ninety minute epoch, Stickgold would occasionally wake the napping individuals and ask them about the content of any dream they were having, or for the group that remained awake, ask them to report any particular thoughts that were going through their minds at the time. Following the ninety-minute period, and after another hour or so to overcome sleep inertia in those who had napped, everyone was dropped back into the virtual maze and tested once more to see if their performance was any better than during the initial learning. It should come as no surprise by now that those participants who took a nap showed superior memory performance on the maze task. They could locate the navigation clues with ease, finding their way around and out of the maze faster than those who had not slept. The novel result, however, was the difference that dreaming made. Participants who slept and reported dreaming elements of the maze and themes around experiences clearly related to to it, showed almost ten times more improvement in their task performance upon awakening than those who who slept just as much, and also dreamed, but did not dream of maze-related experiences. As in his earlier studies, Stickgold found that the dreams of these super-navigators were not a precise replay of the initial learning experience while awake. For example, one of the participant's dream report stated: 'I was thinking about the maze and kinda having people as checkpoints, I guess and then that led me to think about when I went on this trip a few years ago and we went to see these bat caves, and they're kind of like maze like.' There were no bats in Stickgold's virtual maze, nor were there any other people or checkpoints. Clearly the dreaming brain was not simply recapitulating or re-creating exactly what happened to them in the maze. Rather the dream algorithm was cherry picking salient fragments of the prior learning experience, and then attempting to place those new experiences within the back catalogue of preexisting knowledge." As Walker explains, when we are in REM sleep our brains picks salient fragments of past experience and melds them together with our recent biographical experiences (new information) to form new ideas or knowledge. Alternatively, during REM sleep, our brains may drop this new information within various contexts of our past accomplishments and experiences, to test if it can work in those various contexts and thus produce original creative ideas. In this way new information is either accommodated or assimilated into the cognitive structure thus, forming as it does, better understanding of stored knowledge, solutions to existing or non existing problems, and original, unique creations. These are all forms of new knowledge that seem to just suddenly emerge in our minds. Controlling your dreams.
Lucidity has several meanings but most often it is used to describe gaining volitional control of what an individual is dreaming and the ability to manipulate that experience. For instance an individual might decide to fly or even solve a problem. Although claims of such abilities have been around for a while they do not go back far in our history.
This being the case and having little idea as to how such a phenomenon as lucidity might be tested led to much skepticism as to whether this could be possible or was just stories people told. However as Walker explains: "Four years ago, an ingenious experiment removed all such doubt. Scientists placed lucid dreamers in an MRI scanner. While awake, these participants first clenched their left and right hand, over and over. Researchers took snapshots of the brain activity, allowing them to define the precise brain areas controlling each hand of each individual.
The participants were allowed to fall asleep in the MRI scanner entering REM sleep where they could dream. During REM sleep, however, all voluntary muscles are paralyzed, preventing the dreamer from acting out ongoing mental experience. Yet, the muscles that control the eyes are spared from this paralysis, and give this stage of sleep its frenetic name. Lucid dreamers were able to take advantage of this ocular freedom, communicating with the researchers through eye movements. Pre-defined eye movements would therefore inform the researchers of the nature of the lucid dream (e.g.,the participant made three deliberate leftward eye movements when they gained lucid dream control, two rightward eye movements before clenching their right hand etc)...
When participants signaled the beginning of the lucid dream state, the scientists began taking MRI pictures of the brain activity. Soon after, the sleeping participants signaled their intent to dream about moving their left hand, then their right, alternating over and over, just as they did when awake. Their hands were not physically moving - they could not, due to the REM-sleep paralysis. But they were moving in the dream.
At least that was the subjective claim from the participants upon awakening. The results of the MRI scans objectively proved they were not lying. The same regions of the brain that were active during physical right and left voluntary hand movements observed while the individuals were awake similarly lit up in corresponding ways during times when the lucid participants signaled they were clenching their hands while dreaming. There could be no question. Scientists had gained objective proof that lucid dreamers can control when and what they dream while they are dreaming." Walker is quite aware this sounds improbable but as he says the proof is indisputable. "Non-lucid dreamers find it difficult to believe that such deliberate eye movements are possible while someone is asleep, but watch a lucid dreamer do it a number of times and it is impossible to deny."
Life long learning, and the functions of sleeping and dreaming. As stated above sleep and dreaming help us with various processes of learning. NREM sleep is where new information is classified as important or unimportant. It is where that information is consolidated and reinforced if it is classified as important, and deleted, or left to wither, if it is classified as unimportant. REM sleep prepares us for the unknown, and enables us to be the human problem solvers and theorists that gradually uncover the secrets of the universe. But perhaps in doing all this sleep and dreaming also enable us to desire to learn this that and the other and to enjoy each type of learning. These joys and desires are contingent on two things. Firstly the enjoyment of learning and the desire to learn is contingent on how well we learn anything. There is a joy in knowing and expanding our understanding of the patterns of the universe. But this can only exist if we have learned those things well. Sleep and dreaming ensure that we are able to learn things well. Secondly the enjoyment of learning and the desire to learn is contingent on and how useful, what we have learned, is in our lives. The joy of being able to help ourselves through life's journey with what we know is made more enjoyable and desirable by being useful to us. Sleep and dreaming also help to make what we learn useful to us on a continuing basis. It makes sense then that we should come to desire to learn and enjoy learning. If we get enough sleep we will will both enjoy learning and desire to learn so much we will want to continuously learn and thus continue to learn all the days of our lives. |
Does sleep provide an
evolutionary
advantage? 
Dreams
or dream like states. 
If sleep is when our
brains are busy doing something that is essential to our survival then
dreams are where these evolutionary advantages must take place.
Everybody is familiar with the idea that dreams happen during REM
sleep. However, dream like occurrences actually seem to happen in all
stages of sleep. Simply put different types of dream like states seem
to happen at different stages of sleep. There are two main types of
sleep REM sleep
and NREM sleep or slow wave sleep. It seems that during NREM sleep we
have experiences that could be called dreams but which are very
different from most of the dreams we tend to remember. For a start they
tend to be very short and they seem to consist mostly of thinking about
and
the recalling of
experiences from the previous waking period and connecting them
together.
FACT
LEARNING ENHANCEMENT DURING NREM SLEEP.
MOTOR
SKILL LEARNING ENHANCEMENT
DURING NREM SLEEP.
REM SLEEP AS REPLAY OF
EMOTIONAL
THEMES. 
REM
SLEEP AS OVERNIGHT THERAPY. 
Depression
and the theory of overnight therapy.
A
new drug to improve PTSD.
REM
SLEEP TO DECODE WAKING EXPERIENCES. 
CREATIVE
INCUBATION VIA REM SLEEP AND DREAMS. 
Intuition
following REM sleep.
SOLVING
SIMPLE PROBLEMS FOLLOWING REM SLEEP. 
PROOF
OF REAL INSIGHT BEING GENERATED BY REM SLEEP. 
WHAT WE DREAM ABOUT
MATTERS. 
LUCIDITY. 
Needs Interest Method Reality Keys How to Help Creative Genius Future What is Wrong Theories Plus
Karl Popper Self Control Body Control Knowing Maria Montessori Brain Plasticity Memory