Associative plasticity in striatal transplants.

Striatal lesions disrupt both motor and cognitive performance in rats, many aspects of which can be restored by striatal transplants. Because the normal striatum is involved in the formation and maintenance of motor habits, it has been hypothesized that grafted animals may require explicit retraining to relearn previously established habits that have been disrupted by the lesions. We have used a lateralized-discrimination task to reproduce this "learning to use the transplant" effect, combined with a transfer-of-training paradigm to demonstrate that recovery requires relearning specific lateralized stimulus-response associations and cannot be explained simply by a generalized training-dependent improvement in motor skill. These results have clear implications for developing appropriate strategies for the rehabilitation of Huntington's disease patients participating in clinical transplantation programs.