Sleep Deprivation (Cont'd)

Although sleep deprivation does not seem to damage the body, sleep may be required for normal brain functioning. Hand-eye coordination slows down and the subject is likely to be unable to concentrate after losing substantial amounts of sleep. However, sleep deprivation studies of humans propose that although the brain may need slow-wave sleep in order to recover from the day's activities, the rest of the body does not-experiments have shown that bodily exercise has little effect on sleep, but mental exercise seems to increase the demand for slow-wave sleep. During stage 4 sleep, the metabolic activity of the brain decreases to about 75% of the waking level. Thus, stage 4 sleep appears to give the brain a chance to rest. In fact, people are inert to all but intense stimuli during slow-wave sleep and, if awakened, act groggy and confused as if their cerebral cortex has been shut down and has not yet resumed its functioning. These observations suggest that during stage 4 sleep the brain is, indeed, resting.