Describe and evaluate research into the stages of sleep

AS and A Level Psychology

Jenna Fudge - -

Psychology – Charlotte Mottram

Describe and evaluate research into the stages of sleep

To talk about a concept, we must first be clear on its definition. Psychologists describe sleep as an altered state of consciousness. It is a resting state in which an individual becomes relatively quiescent and relatively unaware of the environment. During sleep, which is in part a period of rest and relaxation, most physiological functions such as body temperature, blood pressure, and rate of breathing and heartbeat decrease. The amount of sleep needed depends on both the individual and the environment.

With the invention of the “Electroencephalogram” or an “EEG” as it is more commonly known has made it possible to monitor the brain's electrical activity. The EEG picks up and records electrical activity through electrodes attached to the scalp. The reading of a waking person is clearly different than that of a sleeping person.

The EEG pattern of our brain during waking periods is very rapid, irregular and low on voltage. This means that many neurons are firing at different intervals and at different times, with different strengths too. This type of irregular electrical activity in the brain during wakefulness is called beta waves or beta activity.

When we are relaxed, sitting in the sofa watching T.V. without any mental arousal, the EEG records a waveform called alpha waves or alpha activity, slower than beta waves. These two waves (alpha and beta) represent the irregular firing pattern of large areas of the brain. Brain activity is desynchronised while in alpha and beta activity.

Sleep on the other hand is not a random process; instead, it is a very organized one. Through EEG readings Sleep has been separated into five stages. Stage 1-4 (non-REM sleep) followed finally by REM sleep. Once REM sleep is achieved, the cycle reverses itself and goes back though stages IV, III, II and again to III, IV and REM. Throughout the night, this cycle occurs at 90 to 100 minute intervals.

The difference in EEG patterns that occur during sleep has made it possible to divide sleep into the five different stages:

Stage One

This is when we are first beginning to fall asleep. At this stage we start to see a reduction in the frequency of alpha waves. These are then replaced by low voltage slow theta waves accompanied by slow rolling eye movements. The heart rate begins to slow and the muscles begin to relax, and at this stage it is very easy to be woken up. This state is similar to deep relaxation, so we not even aware that we are falling asleep. Stage one counts for more or less 5% our total sleep during the night and within 5 to 10 minutes, we enter stage 2.

Stage Two

In stage two, we still get theta waves and what are also called K complexes and sleep spindles. Sleep spindles are sudden and intense bursts of electrical activity that last for a second or two. K complexes are also sudden and sharp waves of a longer frequency, these are often but not always triggered by noises. They naturally occur at a rate of one per minute. Some researchers believe that sleep spindles and K complexes help us disconnect from the outside world (noises, etc). This stage lasts only for a few minutes.

Stage Three

After about a total of fifteen minutes, we are ready to enter stage 3. Our bodies and minds are relaxed and our heartbeat and respiration are slow and regular. When we enter Stage 3, our brain activity becomes synchronized. This means that big groups of cells are firing at about the same time. This unified activity in the brain is represented in the EEG recordings by large waves called delta waves. Delta waves are the slowest and strongest waves that our brain produces. Stage 3 is made up of about 20-50% delta waves.

Stage ...

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Stage Three

After about a total of fifteen minutes, we are ready to enter stage 3. Our bodies and minds are relaxed and our heartbeat and respiration are slow and regular. When we enter Stage 3, our brain activity becomes synchronized. This means that big groups of cells are firing at about the same time. This unified activity in the brain is represented in the EEG recordings by large waves called delta waves. Delta waves are the slowest and strongest waves that our brain produces. Stage 3 is made up of about 20-50% delta waves.

Stage Four or “Slow Wave Sleep”

Stage 4 is all delta activity. It is extremely difficult now to wake someone up from the 4th stage of sleep. However, if awakened the person seem confused and disorientated. During stage 3 and 4, growth hormone is secreted by the pineal gland. This hormone encourages bone and muscle growth in children, while in adults it is involved in tissue repair. This is one reason why slow wave sleep has restorative effects. Other hormonal activities, like the secretion of prolactin and gonadotropin occur in these stages, making slow wave sleep a phase of rest and healing.

“REM” Sleep (Rapid Eye Movement)

Once stage four is complete, the person will then cycle back through stages 3 and then 2 before finally reaching REM sleep. At this point our muscles are very relaxed; in fact, we become paralysed. We are mostly disconnected from the outside world, but we might wake up to something meaningful like our names being called out, or loud sounds. A single REM cycle lasts about 20 to 30 minutes in a healthy person in his/her twenties. As REM sleep occurs during every ninety-minute interval after we fall asleep; this means that in an 8 hour sleep we will experience four or five REM sleep stages and every time we enter REM, we stay slightly longer in it.

When sleepers in REM stage are awakened unlike in stage 4 of NREM, usually they seem alert and can react normally. If the sleeper was awakened during slow wave sleep, it takes a few instants to wake up and react. This might be due to the presence of alpha and beta waves in REM sleep and delta activity in slow wave sleep. Remember that alpha and beta are brain waves are also present when we are awake, not only in REM. This is why some researchers believe that REM sleep is an evolutionary adaptation to wake up and be fully alert to a potential emergency in the middle of sleep.

Sleep as I have stated is an altered state of consciousness. To discover the functions and importance of sleep it is necessary to look at sleep deprivation studies when people go without sleep such as randy Gardener and Peter Tripp.

Randy Gardener was a 17-year-old boy who stayed a wake for 264 hours and 12 minutes to create a new world record. For the last 90 hours hew as studied by Dement, Gulevich and Johnson. He had blurred vision, incoherent speech and a mild degree of paranoia but no psychosis and a combination of perceptual and cognitive faults. For instance, he began to mistake objects for people. He also felt that some people were labelling him as stupid because of his impaired cognitive abilities. After he had finished and broke the record he slept for 14 hours and 40 minutes, then on subsequent nights he returned to his usual 8 hours per night. It was noted that Randy Gardener recovered almost 70% of stage 4 sleep and 50% of REM sleep, which suggests that these stages of sleep are of special importance.

The case study of Peter Tripp was somewhat different. Peter Tripp participated in a wakeathon for 200 hours for charity in 1959. After the third day his behaviour started to change, he became aggressive and abusive to close friends. The first physical change, was his sudden drop in body temperature, he also began hallucinating. Interestingly, the psychotic behaviour occurred in 90-minute cycles corresponding to when Tripp would ordinarily have been in REM sleep. It is thought that he was actually experiencing REM sleep whilst awake. On the final day he was certainly in an altered stated of consciousness, he wasn’t asleep or awake. Dr Louis West reported that Tripp "confided that people thought he was Peter Tripp, when really he wasn't, he was an impostor, he was someone else pretending to be Peter Tripp". This delusion wasn't the only one experienced by Tripp - he was convinced that a doctor who came to examine him was an undertaker who intended to bury him alive, and he also reported both auditory and visual hallucinations. As a result of this wakeathon he lost his job, wife and sense of identity, indeed he was permanently damaged. It is from this study and many other studies of people who have experienced detrimental effects after a period of sleep deprivation.

Question: “How is it possible that someone can ignore and go against a natural bodily rhythm for this amount of time? Would the body not have some kind of safety procedure that would keep itself from harm?”

Fatal familial insomnia is an inherited disorder characterized by the slow withdrawal of slow wave sleep until it disappears. There are only small bouts of REM sleep without paralysis when the patient sleeps. The symptoms include confusion, loss of control over the endocrine system and autonomic nervous system activities, insomnia, decreased attention and diminished memory. The disorder is fatal when advanced and it shows how important sleep really is.

So why is it then that sleep is so essential, what purpose does it serve? Why is it then that the deprivation of sleep had such a drastic and detrimental impact on these two men? There have been many theories to explain why sleep is such a necessity. The most well known of which include: The Restoration theory, The Evolutionary Theory, The Neuro-Chemical Theory, The Conservation Theory and The Memory Consolidation Theory.

Oswald believes the purpose of sleep is to restore the body and brain physiologically after the exertions of the day, and that it helps to restore psychological functions. Oswald 1966 who was concerned with physical restoration states that sleep restores depleted energy reserves, eliminates waste products from the muscles and repairs cells. Support for the physiological restoration theory comes from the case study of Peter Tripp where by restorations were prevented, this is clear to see as he had no, or very little energy just after two days without sleep.

Further support is provided by Shapiro et al, who found that people who had completed the ultra marathon (57 miles) slept for an hour and a half longer than they normally did for several nights following the race. Shapiro also found that stage 4 sleep occupied a greater proportion of their sleep, which supports what Oswald stated about NREM sleep, this being that “NREM sleep restores bodily processes which have deteriorated during the day.

However, Ryback and Lewis provide evidence against the physiological restoration theory as they found that healthy individuals who spent six weeks resting in bed showed no changes in their sleeping patterns which is inconsistent with this theory whereby we need to sleep to restore depleted stores. Horne and Minard also provide evidence against the physiological restoration theory by showing that participants who were engaged in various physical activities, although went to sleep faster; they found no increase in the amount of time actually spent asleep.

The Neurochemical theory suggests that we have NREM sleep (and therefore produce seratonin) in order to be able to go into REM sleep, and we need REM sleep to deal with adenosine to provide the brain with the energy for the next day. This might mean that sleep is all about homeostasis – balancing the levels of neurochemicals in our cells. The psychological restoration suggests that sleep helps us to recover from the psychological as well as physiological exertions of the day. Support for this theory comes from Kales et al 1974, who showed that insomniacs suffer far more psychological problems than healthy people. However the research is inconclusive and still continues.

An alternative theory, which has been proposed to explain the functions of sleep, comes from Meddis and is commonly known as the evolutionary theory. Meddis 1975 proposed that the sleep behaviour shown by any species depends on the need to adapt to environmental threats and dangers. He also said that sleep could therefore serve the function of keeping animals fairly immobile (as we are actually paralysed during REM) and less conspicuous from predators during periods of time when they cannot engage in feeding due to poor night vision, or indeed in any other kinds of behaviour. From this we could expect to see those species most at risk from predation sleeping more of the time than the actual predators. However this does not appear to be the case; Lloyd et al 1984 showed that lions that have no predators sleeping when and wherever they could. The evolutionary theory claims that it can explain these anonymities in terms of the animal’s needs and its adaptation to its environment. Therefore the main criticism of this theory is that it is non falsifiable. An important argument against the view that sleep serves an important adaptive function comes from studies in which animals do actually sleep, when they would be better off without it. Pilleri 1979 reported the case of the Indus dolphin, which due to muddy waters became blind, as good visibility was unnecessary. This dolphin still sleeps despite the potential dangers from passing river traffic and debris. I f sleep served a purely adaptive purpose then surely it would have been eliminated as was vision. Horne however suggested that sleep may perform different functions in different species or different sizes of animals, if this is the case, then to look for a global explanation of sleep would seem pointless.

Memory Consolidation theory: This suggests that REM sleep stimulates neural tissue and consolidates information in memory. This theory assumes that information is not fully processed during the day because the “waking brain” is too distracted with incoming and outgoing messages that the outside world creates for information to pass into the long term memory store. Perhaps then that the side affects Gardener and Tripp suffered was due to a kind of “information overload”, by which their brains where not allowed to fully process the events of the day. In laboratory experiments, it has been shown that rats will spend longer in the REM stage of sleep after having been trained in a maze. However could this not also be attributed to the restoration theory as well? Perhaps the reason why they have spent longer than they normally would in REM is because of the extra exertion they would have experienced? Also to contradict this theory, studies with people have shown that sleep deprivation has had little effect on learning. Winston 1997 suggests that the large amount of time that babies spend in REM sleep reflects the fact that so much of their experience is new, and therefore there is a greater need to process this information in the absence of previous experience.

The conservation theory proposes that the main purpose of sleep is to conserve energy during times when (in animals) tasks like feeding and searching for a mate become impossible during the hours of darkness. Sleep therefore in humans represents a form of hibernation, and this follows from the fact that the body temperature, heart rate and therefore metabolism as well all decrease during sleep. It is also true that when food is in short supply that animals will send to sleep more. However, as with the example of lions before who eat very nutritious meals do tend to sleep for long periods, sometimes as much as 12-14 during the day.

Another theory – the Oculomotor System Maintenance theory suggests that REM’s sleep function is solely to keep the eye muscles toned up, to do this, about once every 90 minutes during REM sleep are eyes are given some exercise to keep them in trim. However this of course does not even begin to explain why people who are deprived of sleep suffer such severe side affects.