Temporal dissociation of the prehension pattern in Parkinson's disease.

This study assesses the reach to grasp movement of eight Parkinson and eight control subjects. The reach was of either 15, 27.5 or 40 cm. The grasp was either of a small (0.7 cm) or a large diameter (8 cm) dowel. When comparing Parkinson to control subjects, no differences were found in the regulation of movement parameters according to changes in object distance or size. However, for Parkinson's disease patients the onset of the manipulation component was delayed with respect to the onset of the transport component. It is proposed that this reflects a deficit in the simultaneous or sequential implementation of different segments of a complex movement.