TASK-DEPENDENT DEFICITS DURING OBJECT RELEASE IN PARKINSONS-DISEASE

The present study examined fingertip forces during the replacement and release of an instrumented object on a table in eight subjects with P arkinson's disease (PD) both off and on medication and eight age-match ed control subjects. Subjects performed the task at (1) their preferre d speeds and (2) as fast as possible. During performance of the task a t preferred speed, the duration of object replacement, the rate, and d uration of force decrease following table contact for PD subjects were similar to that observed in the control subjects and were unaffected by medication. In contrast, the rates were significantly lower and dur ations longer in the PD subjects when the task was performed as fast a s possible irrespective of medication. A similar result was obtained w hen subjects were asked to release their pinch force from predefined f orce levels while the object was fixed to the table surface. These res ults emphasize the importance of considering task requirements in orde r to delineate the specific task parameters associated with the moveme nt impairments in Parkinson's disease. (C) 1998 Academic Press.