Last night, while you slept, you went into the REM state and dreamed. More than likely, you won't remember any of your dreams because, for a very good reason, we actually evolved not to. However, all normal, healthy humans go into the REM state and dream every night — and most mammals show evidence of this brain pattern too.
The REM (Rapid Eye Movement) state was discovered in 1953 by Aserinsky and Kleitman . They noticed that when subjects were woken from sleep during the phase of sleep that was characterised by "rapid, jerky, and binocularly symmetrical eye movements" they recalled the most vivid and elaborate dreams. When subjects were awoken from non REM sleep however, significantly fewer dreams were reported and the reports were less intense and more like memories of dreams. And so, the REM state was named, and has been associated with dreaming ever since.
Early brain monitoring devices were used to find that the electroencephalogram (EEG) recordings of the brain were very different in these periods of sleep than others. In fact, the REM state EEG graphs are almost identical to recordings taken when subjects were awake, as the results indicated that PGO spikes (termed "spikes" because of how they appear on EEG recordings) were occurring during the REM state. PGO spikes are bursts of electric energy fired from neurons from pons (P) in the brainstem, through the geniculate (G) body and to the occipital cortex (O). In waking life, these PGO spikes make up the orientation response, that is, the instinctual response to threat that can incite decisions for flight or fight before the animal has time to "think".
What is the REM state?
With the dawn of the information technology age in the 1960s, the new metaphor of the computer was seized upon to explain many processes, including dreaming. Because, during REM sleep, the brain is disconnected from sensory input from the outside world by the inhibition of major muscles scientifically termed the anti-gravity muscles (we are all temporarily paralysed during REM sleep), it could be compared to an off-line computer. It was suggested that the myriad of ‘programs’ contained by the brain could be being updated during the off-line time of REM sleep; and that dreaming was somehow related to this. In other words, REM sleep is for programming the brain. This proposal had the advantage of seeing the REM state as an active one with specific purposes. The computer metaphor prompted scientists to consider REM sleep in the fetus and newborn as a time when the ‘software’ of the brain is programmed, an idea crucially picked up and developed by the French scientist Michel Jouvet.
It was Jouvet who made the discovery of the inhibition of anti-gravity muscles (our major muscles) during REM sleep. He suggested that REM sleep, which he calls paradoxical sleep, might have the role of programming the central nervous system to maintain or organise instinctive behaviour. He argued that the programming of instinctive behaviour on a continuous basis, rather than a once and for all basis during early development, would enable a more efficient expression of instinctive behaviour. Since the original programming must interact with the animal’s experience in the real world, then REM sleep might allow either the original programming to be reasserted (nature over environment) or the effects of the experience to modify the programming (environment over nature).
It was Jouvet’s work that put in place some of the essential building blocks for understanding the function of the REM state.
What is the REM state for?
The REM state is the mechanism that connects us with reality; it is constantly running in the background, searching out at lightning speed the codes needed to match metaphorically to whatever is meaningful in the environment, and thus creating our perception of reality. It is a reality generator, accessing the templates that are the basis of meaning. (This is easily seen when people access memories that evoke strong emotions: rapid eye movements occur even when their eyes are open. We have much evidence of this on film.) It is active when we dream but also when we daydream. It is seen when people go into focussed states of attention (trance) and when strong instincts are aroused. It is associated with hallucinations and hearing voices.
In the dream state, when REM is at its most obviously active and sensory information from the outside world is ‘shut off’, the templates searching for their completion scan the brain and make metaphorical images from whatever they call up from memory. The dream contains these images and, while we are in it, becomes the reality we are conscious of. This is why the reality in dreams so often feels profoundly richer than waking reality – each particular metaphorical dream image can contain multiple levels of meaning, (see this dream example) because the job of the dream is to deactivate emotional arousals and it can do that with several streams of arousals through the same image at the same time.
Our waking reality is quite different – it is dramatically toned down. It has to be because, if we always saw multiple levels of meaning in everything, we wouldn’t be able to make sense of, or operate within, our environment. We would end up totally confused and in a psychotic state. To deal with this problem, the neocortex of the brain, the rational part of our awake mind, inhibits multi-meaning.
1] Aserinsky, E. & Kleitman, N. (1953) Regularly occurring periods of eye mobility and concomitant phenomena during sleep. Science, 18, 273-274
2] Dement, W. (1967) Studies on the effects of REM deprivation in humans and in animals. In Kety, S. S., Ewarts, E. V. & Williams, H. L. (Ed's), Sleep and Altered States of Consciousness, Proceedings of the Association for Research in Nervous and Mental Disease, 45, 456-468
3] Vogel, G.W. (1979) A motivational function of REM sleep. In Drucker-Colin, R., Shkurovich, M. & Sterman, M. B. (Eds) The function of Sleep. Academic Press, 233-250