Spontaneous eye-blinking and stereotyped behavior in older persons with mental retardation.

Previous research indicates that abnormal stereotyped movements are associated with central dopamine dysfunction and that eye-blink rate is a noninvasive, in vivo measure of dopamine function. We measured the spontaneous eye-blinking and stereotyped behavior of older adults with severe/profound mental retardation living in a state mental retardation facility. Analyses revealed that the mean eye-blink rate of the residents that engaged in stereotypy was significantly lower than the rate for residents who did not exhibit stereotypy. Moreover, the stereotypy group also demonstrated greater variability in interblink intervals. These results provide further empirical support for the involvement of dopamine in stereotyped behavior and are consistent with an emerging motor control model of stereotypy.