Functional and cellular effects of environmental enrichment after experimental brain infarcts

Our genes interact with environmental stimuli throughout our lives. The attitude and reaction to an acute cerebral trauma or stroke, as well as the pre-lesion life event and activities, can influence functional outcome. Although difficult to separate in adult human beings, genetic and environmental factors can be selectively evaluated in animal studies. Post-ischemic housing in an enriched environment, i.e. larger cages which allow both social interaction and various activities improves functional outcome, modifies gene activation, and increases dendrite branching and number of dendritic spines in pyramidal neurons in layers II-III in the contra-lateral cortex. Furthermore, it alters lesion-induced progenitor cell differentiation and interacts with neocortical transplantation, drug treatment and training. It is proposed that the interaction between environment and specific treatment needs more clinical attention, and that a general stimulating and positive environment is the optimal base for specific interventions in neurological rehabilitation.