The cerebellum improves the precision of antisaccades by a latency-duration trade-off

The cerebellum adapts motor responses by controlling the gain of a movement, preserving its accuracy and by learning from endpoint errors. Adaptive behavior likely acts not only in the motor but also in the sensory, behavioral, and cognitive domains, thus supporting a role of cerebellum in monitoring complex brain performances. Here, we analyzed the relationship between saccade latency, duration and endpoint error of antisaccades in a group of 10 idiopathic cerebellar atrophy (ICA) patients compared to controls. The latency distribution was decomposed in a decision time and a residual time. Both groups showed a trade-off between duration and decision time, with a peak of entropy within the range of this trade-off where the information flow was maximized. In cerebellar patients, greater reductions of duration as the time of decision increased, were associated with a lower probability for a saccade to fall near the target, with a constant low entropy outside the optimal time window. We suggest a modulation of saccade duration, depending on the latency-related decision time (accumulation of sensory and motor evidences in favor of a goal-directed movement), normally adopted to perform efficient trajectories in goal-directed saccades. This process is impaired in cerebellar patients suggesting a role for the cerebellum in monitoring voluntary motor performance by controlling the movement onset until the ambiguity of planning is resolved.