Relatively brief environmental enrichment aids recovery of learning capacity and alters brain measures after postweaning brain lesions in rats.

Enriched postlesion experience aided in overcoming effects of simultaneous bilateral cerebral lesions made at 30 days of age in one experiment with inbred Fischer rats and in a second experiment with the Berkeley S1 strain. The lesions were directed to the occipital cortex, but in most cases there was also some impairment of the hippocampus. For 60 days after operations, half of the rats lived in small individual cages and half lived in groups in large enriched-environment cages. They were then pretrained and tested on the standard 12 Hebb-Williams problems. Daily injections of methamphetamine (vs. saline) during the period of differential experience in the first experiment produced no effect on the behavioral scores. The second experiment included groups that received only 2 hr/day of enriched experience, and they benefited as much as groups that remained in the enriched environment 24 hr/day. The results of both experiments demonstrated significant beneficial effects of environment when bilateral lesions were made at a later age and when the periods of enriched experience were shorter than had previously been tested. Two additional experiments revealed significant effects of both lesions and environment on weight and RNA/DNA of brain regions.