Environmental influence on outcome after experiment brain infarction.

After permanent ligation of the middle cerebral artery the motor function of rats housed in an enriched environment, i.e. cages with opportunities for various activities but not forcing the rats to do any particular task, is significantly better than in rats housed in individual cages. Rats kept in an enriched environment before and after MCA ligation improved sooner and slightly more than those placed in the enriched environment after ischemia but with no lasting significant difference except for climbing. Preliminary studies suggest that social stimulation is more important than physical activity. Rats with fetal neocortical grafts implanted into the infarct cavity performed better if exposed to enriched environment than grafted control rats housed in standard laboratory cages with 5 rats in each cage. However, they did not perform better than non-grafted rats housed in the same enriched environment. The infarct size did not differ between rats housed in an enriched environment and control rats. There was no correlation between infarct size and performance in rats exposed to an enriched environment. The improved motor function suggest that a rich environment may stimulate mechanisms that enhance brain plasticity.