Question

Given a description of the sleep stages, EGG patterns, dream states, and behavioral correlates seen in an average night of human sleep.

Answer 1

STAGES OF SLEEP AND EEG PATTERN RAPID EYE MOVEMENT SLEEP
During REM sleep, electroencephalogram (EEG) shows irregular waves with high frequency and low amplitude. These waves are desynchronized waves.
NON-RAPID EYE MOVEMENT SLEEP
The NREM sleep is divided into four stages, based on the EEG pattern. During the stage of wakefulness, i.e. while lying down with closed eyes and relaxed mind, the alpha waves of EEG appear. When the person proceeds to drowsy state, the alpha waves diminish .
Stage I: Stage of Drowsiness
Alpha waves are diminished and abolished. EEG shows only low voltage fluctuations and infrequent delta waves.
Stage II: Stage of Light Sleep
Stage II is characterized by spindle bursts at a fre- quency of 14 per second, superimposed by low voltage delta waves.   
Stage III: Stage of Medium Sleep
During this stage, the spindle bursts disappear. Fre- quency of delta waves decreases to 1 or 2 per second and amplitude increases to about 100 μV.
State IV: Stage of Deep Sleep
Delta waves become more prominent with low frequency and high amplitude.

Brain is not inactive during sleep. There is a character- istic cycle of brain wave activity during sleep with irregular intervals of dreams. Electrical activity in the brain varies with stages of sleep.   
Rapid eye movement sleep is the type of sleep associated with rapid conjugate movements of the eyeballs, which occurs frequently. Though the eyeballs move, the sleep is deep. So, it is also called paradoxical sleep. It occupies about 20% to 30% of sleep- ing period. Functionally, REM sleep is very important because, it plays an important role in consolidation of memory. Dreams occur during this period.

NON-RAPID EYE MOVEMENT SLEEP – NREM OR NON-REM SLEEP
Non-rapid eye movement (NREM) sleep is the type of sleep without the movements of eyeballs. It is also called slow-wave sleep. Dreams do not occur in this type of sleep and it occupies about 70% to 80% of total sleep- ing period. Non-REM sleep is followed by REM sleep.