The Influence of Biological Rhythms on Sleep-Wake Regulation

The timing of major night-time sleep is governed in a large part by the endogeneous circadian pacemaker. Under conditions of normal daily life, such dependence is reflected in the tendency for major nocturnal sleep to be initiated five to six hours prior to the temperature minimum and terminated shortly after the minimum. For most people, this corresponds roughly to sleep onset times of between 11 pm and midnight, and wake-up times of between about 6 am to 7 am. Because most humans exhibit similar timing in sleep-wake behavior, societal demands have evolved to accommodate such biological timetables. For a small…