Dyscoordination of pinch and lift forces during grasp in patients with cerebellar lesions.

Effects of cerebellar lesions on the production of isometric pinch force and the coordination of pinch and lift force were examined. Twenty-one patients, mostly with degenerative cerebellar disorders, and ten healthy controls lifted an instrumented test object using the precision grip of thumb and index finger. The load of the object could be varied to study the adaptation of pinch force generation. The results were: (1) Cerebellar patients were able to adapt their pinch force levels to the different object loads. (2) Patients showed a longer latency between the onset of pinch force and onset of life force than controls. The level of pinch force at the start of lift force was elevated. (3) Patients were able to use sensorimotor memory about object load to adapt force output based on previous experience through repetitive testing, but they were significantly less efficient than healthy controls. (4) The temporal profile of pinch force rate of change featured an irregular pattern characteristic for a lack of sufficient anticipatory parameterization.