Involvement of the cerebellum in the initiation of fast ballistic movement in the monkey.

Monkeys were trained to perform a fast ballistic flexion or extension of the elbow in response to a sound cue. The reaction time was about 250 msec in the normal monkey and remained so after deafferentation of the operant arm. In a cerebellectomized animal, the reaction time was consistently longer, being, on the average, 400 msec. This was associated with an equal retardation in the onset of neural changes in the motor cortex. These results are interpreted as evidence for the involvement of the cerebellum in the initiation of some fast ballistic movements.