Perturbation of a prehension movement in Parkinson's disease.

Movement kinematics of the transport and manipulation components of a double-step prehension task were studied in eight Parkinson patients and eight control subjects. The aims were to (a) assess the effects of a spatial perturbation upon the movement for the two groups and (b) add data to the controversy about the damage/preservation of predictive behaviour in Parkinson patients. The results showed: (a) Both groups are able to preprogram a movement. (b) In both groups, the perturbation results in an anticipation of all kinematic parameters, both of the transport and manipulation components. (c) Parkinson patients, when adopting a predictive behavior, show a delay between the beginning of the two components, and thus activate them in sequence rather than simultaneously. This delay is significantly reduced by the perturbation, indicating that Parkinson patients, when using a responsive behavior, can recouple the two motor components.