Recovery of a motor skill in rats with different forelimb preferences after lesioning of the caudate nucleus: the role of intense training.

The aim of the present work was to study the effects of training on the restoration of a lateralized motor skill (a food-procuring forelimb movement) in Wistar rats (n = 83) after lesioning of the caudate nucleus in conditions of infrequent testing and intensive retraining. On the basis of the training results, the rats were divided into those preferring the right (right-handers) or left (left-handers) limb. Testing was followed by lesioning of the head of the caudate nucleus on the side contralateral to the preferred paw. Animals with identical initial preferences were then divided into two groups: an infrequently tested group in which recovery of the skill was tested once weekly for five months, and an intensive retraining group, in which experiments were performed 3-4 times weekly, again for five months. After surgery, animals had to perform the food-procuring skill only with the "impaired" paw. Differences in the recovery of the skill were seen in animals with different limb preferences both in conditions of spontaneous recovery and in those recovering with training. Overall, animals with lesions of the left caudate nucleus (right-handers) showed better recovery than animals with lesions of the right caudate nucleus (left-handers) in both spontaneous recovery and in recovery with training. These findings suggest that the central neural mechanisms of recovery of a lateralized motor skill after unilateral lesioning of the caudate nucleus are different after lesions to the right and left hemispheres.