Impaired temporal prediction and eye-hand coordination in patients with cerebellar lesions.

This study investigated the effect of cerebellar lesions on temporal prediction and coordination in eye and hand movements. Nine patients with cerebellar lesions were compared to controls while they made saccades with and without simultaneous pointing movements towards a target that was either temporally predictable or non-predictable. The direction and amplitude of the target step was always predictable. Patients made much more early and late saccades than controls, but an equal amount of visually triggered saccades. This suggests that inappropriate saccades could be suppressed during the preparation of a goal-directed saccade. Hand movement frequency did not differ between both groups. Thus, cerebellar lesions can induce inappropriate saccades more easily than inappropriate hand movements. Controls, but not patients, generated visually triggered saccades of shorter latencies when the target was temporally predictable. Thus, the patients could not use information about target timing to synchronise visually triggered saccades with the target. They could, however, use this information to improve the suppression of inappropriate saccades. Regarding coordination, patients showed impairments in synchronising saccades with hand movements. Nevertheless, hand movements led to an enhancement of anticipatory saccades in patients as in controls. Moreover, hand movements and temporal predictability affected saccadic accuracy in both groups similarly. These results suggest that cerebellar lesions do not generally prevent access to temporal information on the rhythm of a target sequence or the timing of a planned hand movement. More specifically, the cerebellum seems to be crucial for synchronizing saccades with such learned or planned temporal events.