Additional Somatosensory Information Does Not Improve Cerebellar Adaptation During Catching

Objective: People with cerebellar damage are impaired in their ability to adapt anticipatory muscle activity during catching. We asked whether prior or on-line information about ball weight and drop height could improve the impaired adaptation of people with cerebellar damage.

Methods: Cerebellar and control subjects caught a series of balls of different weights under two conditions. The first condition provided subjects with information about ball weight prior to the series of trials. The second condition provided subjects with information about ball weight, drop height, and time of ball release during the series of trials. Subjects had to maintain their hand within a vertical spatial 'window' during the catch. We measured 3-dimensional position and electromyography (EMG) from the catching arm.

Results: With prior information, controls required a few trials to adapt to a new ball weight. Cerebellar subjects were slow, or unable, to adapt. With on-line information, controls were able to catch the ball within the window immediately, showing that they did not require practice to make this adjustment. Cerebellar subjects remained slow or unable to adapt to the changed ball weight even with on-line information.

Conclusions: These results suggest that other, intact central nervous system structures cannot compensate for the role of the cerebellum in generating and adjusting anticipatory muscle activity across multiple joints.