Environment, social interaction, and physical activity as determinants of functional outcome after cerebral infarction in the rat.

Rats housed in an enriched environment allowing both social interaction and physical activity improve more than rats housed in standard laboratory cages after focal brain ischemia. To determine the relative importance of social and physical activity, rats that sustained ligation of the middle cerebral artery were kept in an enriched environment with opportunities for various activities (group A), housed together in the same size of cage as group A but with no activity-stimulating equipment (group B), or housed in individual cages with a running wheel (group C). There was no significant difference in infarct size between the groups. Limb placement, climbing, balance on an inclined plane, and ability to traverse a beam and a rotating pole were repeatedly tested 2-13 weeks after the operation. During the entire postoperative period, group A performed significantly better than group C in all tests and better than group B on the rotating pole. With time they also performed significantly better than group B in limb placement, climbing, and on the inclined plane. Group B performed significantly better than group C on the inclined plane and in climbing at all times, and by 13 weeks also in the limb placement test and on the beam. Thus, social interaction was superior to wheel-running but an enriched environment allowing free physical activity combined with social interaction resulted in the best performance.