Bilateral contributions to motor recovery in the monkey following lesions of the deep cerebellar nuclei.

A unilateral lesion of the deep cerebellar nuclei in monkeys produced a transient inability to perform a reaching task with the limb ipsilateral to the lesion. The deficit recovered within 2 weeks following a time course having a initial rapid and a subsequent slower phase. After a second lesion of the cerebellar nuclei on the opposite side, the animals developed a bilateral deficit. Recovery occurred bilaterally after this second stage but following the slower rate observed after the first lesion. From these experiments we conclude that the initial, more rapid phase of the recovery after a unilateral cerebellar lesion depends upon intact contralateral cerebellar circuitry and that the slower rate of recovery was mediated by other parts of the motor system.