REM Sleep & Remembering Dreams
(…Continued From REM Sleep & Remembering Dreams Pt 1)
Now let us take a look at the mechanics behind REM sleep. Early ideas about sleep inclined to a ‘passive’ theory that sleep occurs to prevent fatigue or is caused by a lack of sensory stimulation. To support that notion, certain experiments showed that if incoming nerves in the mid-brain were severed, the organism remained virtually in constant sleep.
Some theories propounded that the brain was actively inhibiting consciousness in order to achieve sleep, and some experiments showed that cats could be put to sleep by electrical stimulation of a part of the brain.
It gradually became accepted that the reticular formation in the brain stimulates the cortex of consciousness. There seems to be an inherent rhythmic sleep-wake cycle, but wakefulness is aided by external sensory stimulation.
Several factors assist in maintaining wakefulness by stimulating the reticular formation, such as a decrease in blood oxygen level, excess of carbon dioxide or excessive warmth. The cortex itself is capable of exerting a strong effect on wakefulness – worries or excitement can keep us awake.
When the electrophysiological monitoring of people during sleep began, the distinct states of slow-wave sleep, (SWS), and REM became known. Research has shown that the two sleep states are governed by the ebb and flow of neuro-transmitter substances at the base of the brain.
It is fascinating, in a sleep laboratory, to observe that inevitable alternation, in a roughly 90 minute cycle. Typically, the subject is ‘wired up’ with sensors called electrodes, that are stuck by tape or glue to the body to detect electrical signals accompanying muscular or nervous activity.
Two electrodes on measured positions, (for consistency between laboratories), of a few millionths of a volt are used. Four other electrodes, placed above and below the outer edge of each eye record eye-movements, (EOG), in any direction, and two others on the jaw measure muscular tonus, (EMG).
Those measures provide enough information for a standardised evaluation of sleep state, but often other measures, such as respiration and body temperature, are also recorded. The data formerly appeared on chart paper emerging from the recording instrument – termed a polygraph – but it is more likely nowadays to be stored in a computer and displayed on a screen.
SWS has been arbitrarily divided into four stages, according to the amount of slow waves of a certain amplitude that are present. At sleep onset, in stage one, the eyes begin to roll slightly in many subjects and the waking alpha rhythm, (about ten cycles per second), of the EEG disappears. In stage two, there are sudden ‘k-complexes’ in the EEG in response to external or internal stimuli. Stage three exhibits definite large slow waves and if over half the record consists of such a pattern, stage four is registered. After perhaps 20 minutes or so of stage four sleep, the sequence is reversed, to perhaps stage two, and then REM sleep suddenly makes an entry.
The EEG of REM sleep is active – showing saw-toothed waves. The EMG trace is very narrow, reflecting the amazing bodily paralysis which afflicts the subject for the duration. REM sleep is associated with dreaming. Occasionally, the eyes shift about – in ‘REM bursts’. The movements seem to be a mixture of both involuntary and scanning actions.
Another feature of REM sleep is of penile erections in males – and clitoral erections in females. All men are conscious of the connection between erections and dreaming and it may have been that link which led Freud to assume the sexual nature of dreams. However, it is unwise to assume anything whatsoever in science, and experiments have shown that if subjects are woken repeatedly from REM sleep, the erection cycle gets out of phase with the REM cycle. Thus the two phenomena are linked, but there is not necessarily any cause and effect between them.
Each REM period increases in length during the night, and the amount of SWS correspondingly decreases, so that the first half of the night consists mostly of SWS and the second half predominantly REM.
More recent theories about sleep and dreaming have stressed the evolutionary background and have tried to explain either SWS or REM sleep, but no one idea is fully accepted. Generally, it has been hypothesised that SWS keeps us still and out of harm during darkness and that bodily growth and repair can occur at that time.
REM sleep is seen by some, looking at the computer analogy, as a time when memories are updated and filed, and redundant information discarded – not true! (see common misconceptions).
A few decades ago, it was thought that to be deprived of REM sleep would result in mental disturbance – it was an erroneous belief. It is understood now that some drugs, such as certain anti-depressants, completely abolish REM sleep – and yet there are no noticeable deleterious effects in users.
The surprising conclusion is that REM sleep does not seem to be necessary in adults.
However, it may be very important to the developing foetus. This is conjectured from the fact that sleep of a new born baby is about 50% REM. That type of sleep, then, may be significant in programming or even providing some kind of genetically coded imagery to the foetus. Not many psychologists believe now that the mind of a new born baby is a complete tabular rasa or blank state.
A person who is deprived of sleep will, on eventually resting, experience non-dreaming SWS in preference to dreaming sleep, (REM), so dreaming is a bit of a luxury to those short on sleep.
Interestingly, the 90 minute SWS/REM ‘ultradian’ cycle has been seen to persist into day-time activities, for instance when observing oral activity.
The greatest myth about dreams is that they are over ‘in a flash’. It is surprising how many people today accept that idea as true. It stems from the Frenchman, Maury, who reported having had a long and involved dream which culminated in his execution by guillotine. At the moment the blade fell, he was woken by part of the bed collapsing on his neck. He reasoned that the whole dream construction must have occurred in that moment.
It sounds a plausible notion, but we know that expectation certainly affects dreams and it may have been that his bed often collapsed and perhaps gave warning creeks. The facts of that case cannot now be known. As there was no counter evidence that dreams occurred in ‘real time’, Maury’s theory stayed around and gained considerable ground.
However, Dr Hearne was the first person to show that dreams do actually take as long as they appear to do. In his sleep-laboratory, studies of lucid dreams, where subjects signalled information from within the dream by making coded eye movements, Dr Hearne found that the estimated passages of time between signals corresponded to the actual measured durations in the polygraphic chart record.
FURTHER INFORMATION ON DRUGS
There are different effects alcohol can have on sleep. In addition, it is interesting for the analyst to note that, in small quantities, it acts as a stimulant, but in larger doses, it has the opposite effect – that of being a depressant. Tobacco is also a stimulant and smokers tend to fall asleep after a longer period than non-smokers.
Barbiturates used to be prescribed for insomnia. They were very powerful and suppressed REM sleep. The body then adapted by tolerance so that the baseline level of REM sleep recovered. However, if the user stopped taking the drug, a massive ‘REM rebound’ effect would occur, for several weeks, during which vivid nightmares might result.
DREAM FORGETTING AND RECALL
The reason for rapid evaporation of dream memories is probably to prevent confusing dreams with reality. The memories do not seem to be actually erased – because something the following day can trigger the recall of an entire dream. It is more a case of them being filed away somewhere marked ‘Not normally to be accessed’. Of course, those seeking self-insight and self development from their own dreams have to overcome that obstacle.
Recall is best immediately after the dream. The brain is very active in REM and the thought-processes can function on waking. However, waking from SWS can be quite different – especially from stage four sleep. Often the individual woken from that condition is disoriented, and ‘sleep-drunk’.
DO WE DREAM IN COLOUR?
Finally, let us briefly consider the big differences between individuals as regards colour in dreams. In general surveys on dreams, colour is usually referred to in about a third of cases. If, however, subjects in the sleep lab are asked to report any colours in dreams on being woken from REM sleep, nearly three-quarters can recall colours. The content of the dream seems to be remembered in preference to any colour factors.
Authors Details: David F. Melbourne Web Site
David F. Melbourne, who lives on a remote Scottish island, has been studying dreams for 25 years and is known all over the world for his accurate dream interpretations. Apart from the general public, he has analysed dreams for celebrities and famous authors, all of whom have admitted a high degree of accuracy.