The Basic Rest — Activity Cycle
The basic rest-activity cycle (BRAC) is a physiological periodicity in the functioning of the nervous system of homoiotheraml animals. First detected as a variation in the concomitants of sleep in infants, it involves an alternation of EEG patterns, with a high-voltage slow activity (HVSA) during the rest phase and a low-voltage fast activity (LCFA) during the activity phase. The latter is accompanied by certain somatic and visceral manifestations-changes in heart rate and in respiration movements (REMs), and relaxation of other muscle groups. In human infants, the BRAC is completed in 55–60 minutes, progressively increasing to 85–90 minutes in adult man.