Climbing fiber afferent modulation during a visually guided, multi-joint arm movement in the monkey

During a visually guided, multi-joint volutary arm movement Purkinje cell simple and complex spike activity was recorded from the ipsilateral hemisphere and intermediate zone of the cerebellum in the rhesus monkey. The task consisted of moving a manipulandum over a horizontal video screen. Manipulandum (hand position) was represented by a cursor on the screen, the animal required to place the manipulandum within displayed start and target boxes. Purkinje cell complex spike discharge was examined using two paradigms. In the first the animal moved the manipulandum from a start box to a target box. In the second the animal was required to modify an ongoing movement and place the cursor within a repositioned target box. A majority of the cells (44/74) exhibited a statistically significant increase in the probability of complex spike discharge at various times during the movement. The increase was observed when the movement trajectory was redirected (36/44) and/or during the initial portion of the movement (27/44). These results suggest the climbing fiber afferent system is routinely involved in the execution of multi-joint movements especially when the movement is redirected. Possibilities include that climbing fiber afferent input is required when the motor state changes and/or during errors in motor performance.