Ultradian laterality cycle in stereotyped behavior of a severely mentally retarded patient

The stereotyped behavior of a severely mentally handicapped woman was recorded on video tape continuously during daytime. Stereotyped hand waving activity was determined separately for the right and left hands using consecutive time-sample intervals of 5 minutes. The study included 10 consecutive days and nights. During the nights EEG and eye movements were recorded polygraphically in order to score the sleep stages. Right and left-handed stereotyped activities were found to be modulated periodically with intervals of about 2 hours (ultradian cycles). During the morning and the early afternoon periodicities of both right-and left-handed activities occurred predominantly in bilateral synchrony. By contrast, rhythmic variations of both activities developed a counter-phase course during the late afternoon and evening. Specific phase relationships between the ultradian periods of stereotyped hand activities and the sleep cycle were found. These findings suggest that sleep cycle can be triggered by phases of enhanced stereotyped activity, either of left or right hand. By contrast, sleep seemed to have a synchronizing effect on ultradian cycles in stereotyped activities of both hands. Since stereotyped hand waving can be considered as manifestations of motor arousal levels of the related cerebral hemisphere, the observed periodicities can be viewed as mediated by oscillations in the bilateral brainstem arousal system. A model interpreting the main findings is proposed.