Role of various brain areas in recovery from partial cerebellar lesions in the adult rat

Several experiments were performed to assess: (1) the effects of partial cerebellar lesions on gross locomotion, balance, and posture in the rat; (2) the rate and degree to which deficits are compensated; and (3) the location of brain systems responsible for recovery. On our tests, lesions of the lateral cerebellar cortex produce no motor or postural deficits. As in other species, unilateral lesions of the vermal cortex produce ipsilateral limb extension, while hemicerebellectomies and lesions of the entire fastigial nucleus, or only its rostral part, produce contralateral limb extension. Lesions of the caudal fastigial nucleus alone produce symptoms similar to a vermal cortex lesion. Animals with medial cortex lesions had recovered by 10–15 days postoperatively, while those with fastigial nucleus lesions or hemicerebellectomies showed complete recovery by 30–35 days. Those animals which suffered gliosis or chromatolysis within the lateral vestibular nucleus showed more persistent symptoms. Finally, secondary-lesion experiments suggest that circuits through the contralateral fastigial nucleus, rather than the motor cortex, are primarily responsible for recovery after unilateral cerebellectomy in the adult rat.