Temporal control of a bimanual task in patients with cerebellar dysfunction

The objective of the study was to investigate whether temporal control duri ng: a goal-directed bimanual action is disturbed in cerebellar patients. Th e task nas to open a dr,sn er with one hand and to reach and grasp a small abject: with the other hand. Interlimb coupling was determined at start and end positions. Cerebellar patients as compared to normal subjects showed a n increased offset For initiating the hand movements which denotes the invo lvement of the cerebellum for organizing the components underlying the bima nual task. The reduced simultaneity was caused by a delayed movement onset of the grasping (non-leading) hand as compared to the pulling hand. Lack of vision increased the degree of desynchronization for the patients at the s tart position, indicating that they depended on external cues for organizin g the temporal coordinates of the combined motion pattern. At the goal, the magnitude of temporal offset was similar/smaller than at movement onset wh ich can be related to feedforward mechanisms that are used to anticipate th e limbs' end positions. These results confirm the role of the cerebellum Fo r planning the temporal ordering of movement sequences into a synergic acti on. (C) 2000 Elsevier Science Ltd. AU rights reserved.