Articles

WHAT IS SLEEP: A NORMAL SLEEP PATTERN

The main difficulty in conducting research on human sleep consists in the sleeper's own inability to provide information about the results of his sleep, so the researcher must use external observation and measurement to the extent possible without disturbing the subject's sleep. If the researcher wakes up the subject, the subject is no longer a sleeper. In fact, the researcher is then at odds with the subject's sleep-wakefulness pattern. The researcher is at the mercy of his own observations concerning sleep. Only since the establishment of well-equipped sleep laboratories and the refinement of the EEG for making brain wave measurements comparable to measurements made by the EKG o the muscular contractions of the heart has it been possible to obtain information about the activities of the brain even during sleep and to develop new insights into the problem.

Rapid eye movement (REM)

Measurements and comparison of brain waves among waking and sleeping persons disclose various patterns, making it possible to distinguish several levels or phases

of the depth of sleep that are repeated approximately every two hours during nocturnal sleep. Parallel to these EEG changes, periodically recurring rapid eye movements (abbreviated to REM) can be observed. There are also periodically recurring changes in various vegetative reactions that have an effect on breathing, heartbeat, blood pressure, body temperature, and body movements. The most important results of all these investigations can be approximately summarized as follows:

The depth of sleep changes periodically. During waves of deep sleep in which the body is for the most part calm, there is a buildup of still more important phases of relative disquiet and lively bodily reactions that are repeated approximately every two hours. The first portion of the slowly increasing depth of sleep with its associated EEG findings is called the "synchronic sleep phase," or "orthodox sleep." It is followed by a significantly contrasting "asynchronic sleep phase," or

"paradox sleep," which is called REM sleep because of the strikingly rapid eye movements that occur during it. This asynchronic sleep phase is of critical importance for our health. It is essential to many psychic and physical (psychophysical) processes. We evidently dream during this phase. Just how necessary dream phases are for the well-being of our organism has been shown by experiments in which subjects were deprived of their REM periods. This can be accomplished quite easily by waking up the subject at the start of the rapid eye movements. After being repeatedly deprived of the REM phase, the subject became irritated, discontent, aggressive or even depressed and, if permitted, started to dream with increasing frequency. He seemed to fight for his REM phases, and seemed to want to make up for them and to supplement them. Hence it is known that the body does not accept a shortage of REM phases without protest. It makes up for a deficit of REM periods by having more REM periods. French literature therefore mentions a particular form of sleep disturbance characterized by shortened REM phases, using the term "unsuccessful" or "missed" REM periods. Both terms stress the special importance of REM period s.

The pattern of brain wave trackings shows that the periodicity of deep sleep phases steadily becomes smoother during the course of the night. In other words, the separate deep sleep phases become increasingly calm. The REM phases do just the opposite. During the course of the night their periodicity increases. They occur more frequently and for longer periods. All subjects tested confirm that dreaming takes place during the REM periods. Subjects were able to recall their dreams immediately upon arousal after the completion of an REM phase.

The course of normal sleep can be described as follows: it begins with a first stage, a kind of sleepiness, a condition in which contact with the environment is diminished but which can easily be penetrated by arousal stimuli. As fatigue increases, there is a stage of light sleep. Although EEG tracings show that the brain is already involved during this period with real sleep, it can still be reached by external stimuli. But these stimuli no longer result in waking up the subject, i.e., sensory stimuli are still registered and dealt with by the appropriate sense organ but do not reach the consciousness for evaluation. The subsequent transition to deep sleep is smooth, and the sleeper cannot easily be awakened from this phase. In fact, not all sleepers reach this phase to the same extent; the phase also varies in duration, but it is a part of normal sleep. This rhythm is repeated approximately five or six-times within one night. The pattern of the curve becomes increasingly smooth

while, as already described, the dream phases occurring at intervals in between become longer, more frequent, and more intensive.

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