Neuronal Activity Related to the Visual Representation of Arm Movements in the Lateral Cerebellar Cortex

Abstract

Testing the hypothesis that the lateral cerebellum forms a sensory representation of arm movements, we investigated cortical neuronal activity in two monkeys performing visually guided step-tracking movements with a manipulandum. A virtual target and cursor image were viewed co-planar with the manipulandum. In the normal task, manipulandum and cursor moved in the same direction; in the mirror task, the cursor was left-right reversed. In one monkey, 70- and 200-ms time delays were introduced on cursor movement. Significant task-related activity was recorded in 31 cells in one animal and 142 cells in the second: 10.2% increased activity before arm movements onset, 77.1% during arm movement, and 12.7% after the new position was reached. To test for neural representation of the visual outcome of movement, firing rate modulation was compared in normal and mirror step-tracking. Most task-related neurons (68%) showed no significant directional modulation. Of 70 directionally sensitive cells, almost one-half (n = 34, 48%) modulated firing with a consistent cursor movement direction, many fewer responding to the manipulandum direction (n = 9, 13%). For those "cursor-related" cells tested with delayed cursor movement, increased activity onset was time-locked to arm movement and not cursor movement, but activation duration was extended by an amount similar to the applied delay. Hence, activity returned to baseline about when the delayed cursor reached the target. We conclude that many cells in the lateral cerebellar cortex signaled the direction of cursor movement during active step-tracking. Such a predictive representation of the arm movement could be used in the guidance of visuo-motor actions.

The Role of the Monkey Dorsal Pontine Nuclei in Goal-Directed Eye and Hand Movements

“…The latency of burst onset times of HMR neurons in the DPN lies between the time range of possible cortical input structures like area 7a where 61% of the HMR neurons precede the movement onset by Ͼ200 ms (Battaglia-Mayer et al, 2007) and motor cortex output that precedes movement initiation by 70 -130 ms (Kakei et al, 1999). On the other hand, it leads those in lobules V and VI of the cerebellum where many neurons fire during movements (Liu et al, 2003), in full accordance with their role as intermediate stages in a pathway linking cerebral cortex and the cerebellum. The difference in burst onset time relative to movement onset between the SR and HMR neurons in the DPN is reminiscent of the differences in the time required to start an eye compared with a hand movement.…”

Delayed Visual Feedback Affects Both Manual Tracking and Grip Force Control When Transporting a Handheld Object

“…This idea of multiple predictors is reminiscent of a previous proposal by Miall et al (1993) who suggested that the brain predicts separately the visual and somatosensory consequences of actions. Neurophysiological support for this hypothesis was later provided by Liu et al (2003) who showed that in the cerebellum, distinct neurons code for the visual and somatosensory consequences of limb motion.…”

Position, Direction of Movement, and Speed Tuning of Cerebellar Purkinje Cells during Circular Manual Tracking in Monkey

“…Furthermore, modulation during the cue period cannot account for the modulation during the track period. Both findings suggest that arm movement is the predominant determinant of the simple spike firing for Purkinje cells recorded in this location (Coltz et al, 1999;Liu et al, 2003). However, the modest cue period modulation suggests that Purkinje cells may be participating in preparatory or predictive activity (Marple-Horvat and Stein, 1990;Liu et al, 2003).…”