Basic rest activity cycle and stereotyped behavior of a mentally defective child.

Stereotyped acts of a mentally defective girl, 6 1/2 years old, were observed from 6 a.m. til 8 p.m. during 16 days. Alternating phases of more or less frequent hand waving showed intervals of about 1 1/2 hours. Sleep stages were also determined by polygraphic recordings during 10 nights. As statistically proved the mean peak-to-peak interval of stereotyped activity at days corresponded with the mean REM-to-REM period of consecutive nights. This suggests, that the stereotyped hand waving of this child was driven by the BASIC REST ACTIVITY CYCLE (BRAC) already described by Kleitman. 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. Thereby half periods found in phase with REM-stages approximatly corresponded to maxima of stereotyped activity. It will be discussed that the BRAC triggers motor and sensory mechanisms characterizing both the phases of enhanced stereotyped activity at day and REM stages at night.