PSYC 211 - Chapter 9


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CHAPTER 9: SLEEP AND BIOLOGICAL RHYTHMS A PHYSIOLOGICAL AND BEHAVIORAL DESCRIPTION OF SLEEP Sleep is a behaviour. Stages of Sleep The best research on sleep is conducted in a sleep laboratory. The sleeper is prepared for electrophysiological measurements by having electrodes attached to the scalp that can monitor the electroencephalogram (EEG) , to the chin to monitor muscle activity, recorded as the electromyogram (EMG) , and around the eyes to monitor eye movements recorded as the electro-oculogram (EOG) During wakefulness the EEG of a normal person shows 2 patterns of activity: 1. Alpha activity o Consists of regular, medium frequency waves of 8-12 Hz. Activity produced when a person is resting, not engaged in strenuous activity. o Occurs most often when eyes are closed. 2. Beta activity o Consists of irregular, mostly low amplitude waves of 13-30 Hz. o Shows desynchrony: Desynchronized activity occurs when a person is alert and attentive or is thinking actively. Examination of a typical nights sleep Lights are turned off Stage 1 -The subject becomes drowsy and enters stage 1 sleep marked by theta activity (3.5-7.5 Hz). -Stage 1 is a transition between sleep and wakefulness. About 10 min. later Stage 2 The EEG during this stage is irregular. It contains periods of: -Theta activity - Sleep spindles : short busts of waves of 12-14 Hz that occur between 2 and 5 times a minute during stages 1-4 sleep. Some researchers believe that it is involved in keeping a person awake. - K complexes : sudden, sharp wave forms only found in stage 2. The subject is sleeping soundly at this point, but if awakened might not recall having slept. About 15 min. later Stage 3 Stage 3 is signalled by the presence of high amplitude delta activity (less than 3.5 Hz). Stage 3 contains 20-50% delta activity. Stage 4 The distinction between stage 3 and stage 4 is not clear. Stage 3 contains 20-50% delta activity. Stage 4 contains more than 50%. - Stage 4 is the deepest stage of sleep. Only loud noises will cause a person to awaken. When awakened the person is groggy. - The person will not recall dreams when awakened from slow-wave sleep (stages 3-4) 90 min. after the REM - The EEG becomes mostly desynchronized. 1
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beginning of sleep and about 45 min. after the onset of stage 4. sleep - The eyes are rapidly darting back and forth beneath the subjects closed eye lids. - The EMG becomes silent and there is a profound loss in muscle tone. In fact, the body becomes paralyzed during REM sleep. -REM = Rapid Eye Movements - The person might not react to noises but is easily aroused by meaningful stimuli (the person’s name). The awakened person is alert and attentive. - Storylike progression of events in dreams. Stages 1-4 are called
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This note was uploaded on 02/13/2011 for the course PSYC 211 taught by Professor Yogitachudasama during the Winter '09 term at McGill.

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