MOTION IMAGERY IN PARKINSONS-DISEASE

Patients with Parkinson's disease fail to fully profit from advance in formation about a target's movement in tracking tasks, possibly indica ting deficient anticipation of the target's movement. Time estimation has been claimed to be deficient in Parkinson's disease. On the backgr ound of these studies, we tested the hypothesis that motion imagery is impaired in Parkinson's disease. Eleven non-demented patients with Pa rkinson's disease and nine age-matched controls participated in experi ments testing their ability to anticipate trajectories of moving point s (prediction whether two moving points would crash or not) and to est imate the time needed for completion of an invisible target's movement (a point moving around a circle). In addition, mirror drawing, a task involving motor learning and adjustment of movement to incongruent vi sual feedback, was tested. The Parkinson's disease patients, who faile d to improve on mirror drawing, were not impaired on the imagery tasks : they estimated movement time and predicted trajectories with equal p recision as the controls, Motion imagery thus appears to be intact in Parkinson's disease. However; Parkinson's disease patients did not acc elerate their predictions of trajectories with practice as fast as the controls, a deficit which may be interpreted in terms of the fronto-s triatal dysfunction repeatedly demonstrated in Parkinson's disease.