Every day we experience profound changes in mental and physical condition as body and brain alternate between states of high activity during the waking day and recuperation, rest, and repair during night time sleep. In human and other mammals the primary body clock is located in the suprachiasmatic nuclei. The circadian pacemaker located in the suprachiasmatic nucleus of the hypothalamus regulates the timing and consolidation of sleep. There are many the circadian sleep-wake cycle disorder and the growing use of activity-based monitoring(actigraphy) in sleep disorder has enriched and challenged traditional sleep-monitoring technique. Actigraphy provides useful measures of sleep-wake schedule and sleep quality.
