Object release in patients with Parkinson's disease.

Fingerstrip forces were examined in eight subjects with Parkinson's disease (PD) both OFF and ON medication and eight age-matched control subjects during the replacement and release of an instrumented object on a table. While the employed grip forces were similar in the PD subjects and controls, four PD subjects had greater than 25% increases in their grip forces ON compared to OFF medication. The PD subjects also had a greater reduction in their grip forces prior to table contact. However, the rate and duration of isometric force decrease following table contact were similar to the controls', and the forces were scaled according to the object's weight. This suggests that most aspects of object release are not greatly disrupted, and emphasizes the specificity of impairment in PD.