If you have seen the recent Hollywood blockbuster Inception, a movie that does to dreaming what The Matrix did for virtual reality, you may have been holding your breath as Ariadne, an architecture student, folded the streets of Paris over herself like a blanket. This stunning sequence, an homage to M. C. Escher, is testimony to the bizarre nature of dreams. Watching it made the neuroscientist in me reflect on what dreams are and how they relate to the brain.
The first question is easy to answer. Dreams are vivid, sensorimotor hallucinations with a narrative structure. We experience them consciously—seeing, hearing and touching within environments that appear completely real (though curiously, we do not smell in our dreams). Nor are we mere passive observers: we speak, fight, love and run.
Dream consciousness is not the same as wakeful consciousness. We are for the most part unable to introspect—to wonder about our uncanny ability to fly or to meet somebody long dead. Only rarely do we control our dreams; rather things happen, and we go along for the ride.
Everyone dreams, including dogs, cats and other mammals. But sleep lab data reveal that people consistently underreport how often and how much. The reason is that dreams are ephemeral. Memory for dreams is very limited and largely restricted to the period before awakening. The only way to remember a dream is to immediately recall it on waking and then write it down or describe it to another person. Only then does its content become encoded in memory.
Although we often have trouble remembering dreams, our dreaming selves have full access to our pasts. In dreams we recall earlier episodes from our lives, and we often experience intense feelings of sadness, fear, anxiety or joy. Perhaps it was this heightened emotionality that led Sigmund Freud to speculate that dreams serve as wish fulfillment. Regardless, the answer to my second question—how and why does the brain manufacture dreams?—remains a fundamental mystery. But psychologists and brain scientists have recently renewed their interest in this everyday surreal activity.
Perchance to Dream
In 1953 Nathaniel Kleitman of the University of Chicago and his graduate student Eugene Aserinsky discovered that slumber, which had been considered a single continuous period of downtime, contains recurring periods in which the sleeper’s eyes move about, heartbeat and breathing become irregular, most voluntary muscles are paralyzed and brain activity (as measured by electroencephalography) is heightened. These fast, low-voltage brain waves resemble the ones that occur during wakefulness. This state became known as rapid eye movement (REM) sleep, to distinguish it from deep sleep.
When people are woken from REM sleep, they usually report vivid dreams. Such reports do not occur when people are roused from non-REM sleep. Thus arose the close association between REM sleep and the oneiric state. For many years experts associated dream consciousness with the distinct physiology of the brain during REM sleep.
But in the past several decades that understanding has begun to slowly shift. When people who are woken from deep sleep are asked “What was passing through your mind just before you woke up?” rather than the more biased “Have you been dreaming?” a more nuanced picture emerges.
In the early phases of deep sleep, and during short daytime naps, which consist of pure non-REM sleep, people report vivid hallucinations that are shorter, more static and more thoughtlike than the dreams that occur during REM sleep. These visions are typically more like snapshots than narratives and do not include a self. Yet a minority of non-REM dream reports are indistinguishable from REM dreams. It is also notable that sleepwalking and nightmares occur in deep, not REM, sleep. Thus, scientists have had to revise the belief that the REM state is an external manifestation of the subjective dream state.
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Add CommentI seem to be at odds with your report as I remember most of my dreams, I don't write them down or tell anyone what they are. If I think about a past dream, it links to another past dream and so on. It is like watching short vignettes, or a slide show. My dreams are always very vivid, this may be a result of the REM sleep disorder that I have. The more stressful my day has been the more vivid my dreams will be that night and I am more likely to act them out.
Reply | Report Abuse | Link to thisWalksoftly you are remembering the the dreams you remember,there are probably just as many that you forget.As for the article,lucid dreaming which I do often is barely mentioned,my trigger for such dreams is flying.This because I know I can't,it is then that I have complete control taking it where I may.I just wish the experience could last longer.sometimes it's a few seconds other's last for several minutes,either way it's exciting every time.I don't know if it's a REM disorder that allows this,but would like to here from others that can do the same.
Reply | Report Abuse | Link to thisWalksoftly you are remembering the the dreams you remember,there are probably just as many that you forget.As for the article,lucid dreaming which I do often is barely mentioned,my trigger for such dreams is flying.This because I know I can't,it is then that I have complete control taking it where I may.I just wish the experience could last longer.sometimes it's a few seconds other's last for several minutes,either way it's exciting every time.I don't know if it's a REM disorder that allows this,but would like to here from others that can do the same.
Reply | Report Abuse | Link to thisI disagree with your conclusion that REM sleep has been disassociated with dream processes. The destruction of the pons most likely simply inhibits the physical activity of rapid eye movement during dreaming. This simply indicates that REM does not cause dreaming but rather that dreaming produces REM activity.
Reply | Report Abuse | Link to thisAs I understand, the pons conducts signals between major functional regions of the brain. It seems most likely that the destruction of the pons simply prevents the transmission of signals (from functional regions performing processes that we perceive as dreams) to the eye muscles.
It should be concluded from this that rapid dream processes produce signals that control eye movements.
In managing computer databases, new data is often stored very quickly in order to keep pace with arrival rates and data acquisition requirements. It's common practice to reorganize and optimize the storage of the recently acquired data at a later time, when demands are less stringent.
Reply | Report Abuse | Link to thisIn fact, database management software often requires that database access be shut down during this process, which can further encode data to reduce total storage requirements and to build relationships and indexes to the data to optimize retrieval performance and enhance functionality.
These methods employed to manage 'short term' and 'long term' memories may likely also be employed by the brain. The most appropriate time to perform these 'offline' tasks would be during sleep.
The manipulation of memories during certain periods of sleep likely accounts for the visual effects during dreaming and its normal correspondence with rapid eye movement, indicating that it is the process of memory recollection and alteration that stimulates the visual system.
It is likely the reencoding of memories (which may include constructing pointers to shared common features to reduce neuronal allocation requirements) and their indexing or association with other memories that likely contribute to the perception of surrealistic experiences while dreaming. The rapid eye movement may indicate that these processes occur at relatively high speeds, unencumbered by other physical events.
That destruction of the pons inhibits REM but does not inhibit dreaming is clear indication that dreaming produces REM.
Reply | Report Abuse | Link to thisI think there is overwhelming evidence that dreaming normally occurs during REM.
I do realize that I don't remember every dream, the point I was making is that I remember so many. The author states "The only way to remember a dream is to immediately recall it on waking and then write it down or describe it to another person. Only then does its content become encoded in memory." I have never met anyone else that remembers dreams the way I do.
Reply | Report Abuse | Link to thisOn another note I have always wondered what the dreams of people who have been blind since birth are like?
Perhaps it is my scientific background, but most of my dreams seem to be "thought experiments" for social situations. I find myself in either an unpleasant or wished-for situation and try things out as to how to deal with it. There have been innumerable times when I have woken up from a dream and my firth thought was "that sure wouldn't work". What I think most interesting is how my unconscious mind seems to be able to come up with good guesses as to how others would react to my own imagined behavior, much better than my waking mind can.
Reply | Report Abuse | Link to thisIts interesting that we don't smell things during sleep.
Reply | Report Abuse | Link to thisIs this because the olfactory bulb is the perspective from which dreams are 'seen'. I suggest that in our evolutionary history, before the advent of complex spoken language, much of our conscious process was mediated through and integrated with our sense of smell which is centered in the olfactory bulb. Thus this region has historically and geographically (being at the brain center) had many connections with other parts of the brain and is well situated to interface emotive with motor centers and the forebrain.
However with the advent of language perhaps conscious process is mediated through the rostral anterior cingulate.
So perhaps sleep corresponds to the activation of an ancient conscious process which is not so activated by language but rather by instinct. Thus the narratives or plot may not so be driven by a linguistic (kind of logical) drive but more by animal emotions.
Such animal emotions might be less related to a sense of self which is given support and structure through language.
This might explain that dreams deal with inter-personal relations at a more animalistic, perhaps more empathetic level.
Indeed perhaps dreams reinforce our empathetic neural process which might not be so active in our waking consciousness.
So perhaps the thought itself that we are social animals is given vent and support in dreams.
Infact why shouldn't it be that we do not realize we have dreamed because that 'language' of our dreams is unrecognizable to our waking self which is conducted through a conscious (or waking )language.
Maybe the language of dreams are emotions which subserve and structure our waking without us realising it consciously (because our waking consciousness is a different language to the one we dream in)
Though my dreams at times depend on my stress level, This occurs variably. Contrary to most dream research papers, the amount of stress at a high degree does not risk a greater chance of dreaming. This is pertainigng to only me, however. If I do have a dream, they are completely random, nothing to do with my day.However, various objects and people and places are incorporated in my dream, from previous days mostly.
Reply | Report Abuse | Link to thisInteresting article, this line:
Reply | Report Abuse | Link to this"Dreams are of great interest to the student of the mind-body problem, because they bear witness that the brain alone is sufficient to generate consciousness."
I believe that the consciousness generates the brain instead. Our dreams are the key to seeing the reality of the collective state of dreaming we seem to be existing in when we are awake.
Miles Harman
Author, When Dreams End
www.whendreamsend.com
There are some dreams I had many ago which I still remember today, because they are so vivid and, moreover, premonitory. I wish I could solve this puzzle.
Reply | Report Abuse | Link to thisI like that idea - that really we are dreaming when we are awake - but our body feeds into those dreams - so to guide them.
Reply | Report Abuse | Link to thisI've just had a thought. The olfactory bulb, is divided into two distinct structures.
Reply | Report Abuse | Link to thisPerhaps consciousness originated here. One part being conscious of stimuli and one not. One part integrating extensively throughout the brain and the other producing more local effects.Perhaps the cells in the conscious part are indeed tuned achieve to a particular type of computation. I wonder if there are particlar chemical and electrical potentials between these two structures that separate the conscious and unconscious worlds?
Peter REynolds
Reflectogenesis@hotmail.co.uk
Is the case that consciousness originated in the olfactory bulb where and when it had both neural and specific organic structural correlates? This later being achieved, rather than in one specific location and in one structure or group of structures, but by some dynamic delocalised interaction within the brain or indeed becoming delocalised to involved the whole brain perhaps even body?
Reply | Report Abuse | Link to thisreflectogenesis@hotmail.co.uk
One might think of consciousness then as originating in some specific electronic structure subtending molecular and thence on the next level some structural unit.
Reply | Report Abuse | Link to thisWith evolution this hierarchical effect becoming more delocalised - so to make it more robust and damage tolerant - so that it can be thought of as a 'field' which might encompass electrochemical and electrical fields which are able to rapidly mediate the state of the organism in response to specific local stimuli.
refelectogenesis@hotmail.co.uk
The bizarreness and vividness of dreams are distinct from normal experience and therefore unlikely to be “retrofitted.” Indeed, people with memory deficits do not report fewer dreams.
Reply | Report Abuse | Link to thisThe fact that people with memory deficits don't report fewer dreams doesn't support your claim. It might actually be used to support the notion that dreams ARE indeed confabulated.
Surely you can't confabulate an experience. The experience is real. It must be the narrative that makes the experience real. So the narrative is real as well.
Reply | Report Abuse | Link to thisSometimes I dream that I am asleep dreaming about myself being asleep dreaming. When I awake in my dream I awake in my dream and I awake in my dream.
Reply | Report Abuse | Link to thisBut then sometimes in my dream I awake thinking that I'm dreaming but then I realise in my dream that I am only dreaming.
Reply | Report Abuse | Link to thisNot quite sure how that works out under those circumastances.
If I realise when I am dreaming that I am dreaming that I am dreaming.
In fact if I was dreaming that I was dreaming that I was dreaming. What would happen if in my dream I dreamt that I had awoken from my dream and at the same time realized I was dreaming that I was dreaming that I was awaking from a dream? If I awoke at this point would I have been dreaming? Surely it couldn't have been a dream - otherwise why would I have awoken at this point?
Reply | Report Abuse | Link to thisIs this a paradox that proves dreams are mot dreams?
Peter Reynolds
reflectogenesis@hotmail.co.uk
We really dream all the time, even while wide awake and here is why;
Reply | Report Abuse | Link to thisWhile falling to sleep for a few seconds in the middle of a sitting meditation (I practice awareness of breathing)I suddenly found myself in the middle of a dream that seemed to have been going on before I became aware of it; I was in the middle of a discussion of a point with three others in front of a white board. I realized, immediately after coming back to awareness that I must have peeped in on something that was happening in my mind before I became aware of it. This happens to me every time I fall to sleep during a meditation session.
Because of such incidents I am convinced that we dream all the time but we are not aware of doing so because our attention is taken by our waking state consciousness. But when we sleep, and when ordinary consciousness disappears there is more chance for our attention to turn to what has been going on all the time; our ever present dreaming.
This is analogous to sensory inputs to which we are unaware (unless we deliberately take our attention to them)but to which our brains still respond intelligently though unconsciously.
The fact that we are dreaming all the time may explain why our moods may change without apparent reasons; something must have happened in our bellow consciousness dreaming that caused the change in the mood.
If what I am saying is true then this should influence the direction in which we are looking in order to answer the questions; Why do we dream, and what do dreams mean?
Jabr Alnoaimi
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Quote... "Dream consciousness is not the same as wakeful consciousness."
Reply | Report Abuse | Link to thisWaking consciousness is objective awareness, Dream consciousness is subjective awareness.