Basic Rest Activity Cycle and Stereotyped Behavior of a Mentally Defective Child

Abstract

Stereotyped acts of a mentally defective girl, 6 1/2 yr old, were observed from 6 a.m.-8 p.m. during 16 days. Alternating phases of more or less frequent hand waving showed intervals of about 1 1/2 h. Sleep stages were also determined by polygraphic recordings during 10 nights. The mean peak-to-peak interval of stereotyped activity during the day corresponded with the mean REM[rapid eye movement]-to-REM period of consecutive nights. The stereotyped hand waving of this child was driven by the basic rest activity cycle (BRAC). The mean periodicity of sleep cycles was represented by model rhythms adapted to the scored sleep stages. If the model rhythms of all 10 nights were extended backward to the preceding days, they paralleled the stereotyped activity. Half periods found in phase with REM-stages approximately corresponded to maxima of stereotyped activity. The BRAC triggered motor and sensory mechanisms characterizing both the phases of enhanced stereotyped activity at day and REM stages at night.