Sparing and recovery of spatial alternation performance after entorhinal cortex lesions in rats

Groups of adult rats were first trained on a spatial alternation task and then subjected to unilateral entorhinal cortex lesions, unilateral entorhinal cortex lesions followed by dorsal psalterium transections, or bilateral entorhinal cortex lesions. After this surgery, the rats were then tested for retention of spatial alternation. Neither unilateral lesions alone nor unilateral lesions followed by dorsal psalterium transections resulted in long-term spatial performance deficits; however, animals with bilateral lesions exhibited severe impairments from which they eventually recovered. The results from animals with bilateral entorhinal damage indicate that extensive postoperative training may facilitate the recovery of spatial alternation performance. Histological analyses indicated that the crossed entorhinal projection proliferated in the dentate gyrus after unilateral entorhinal lesions and such anomalous growth occurred independently of any changes in alternation performance.