BLINK RATE AS AN INDEX OF DOPAMINE FUNCTION IN ADULTS WITH MENTAL-RETARDATION AND REPETITIVE BEHAVIOR DISORDERS

Direct observation of blink rate was used as a noninvasive, in vivo es timate of dopamine function in adults with mental retardation and repe titive behavior disorders. Blink rate as measured in groups of stereot ypy, compulsion, and control subjects was highly stable. Subjects with stereotypies had significantly lower blink rates than did control sub jects. Although blink rates for compulsive subjects were not significa ntly different from those of control subjects, a subgroup of compulsiv e subjects with comorbid stereotypic behaviors displayed significantly lower blink rates. Significant inverse correlations were found for bl ink rate and severity of repetitive behavior disorder and for blink ra te and ratings of motor slowness. These findings support the hypothesi s that stereotyped behavior among adults with mental retardation is me diated by hypodopaminergic function.