Environmental enrichment following brain damage: an aid to recovery or compensation?

Postoperative environmental enrichment (EC) in rats with brain lesions has been hailed as a potential agent of recovery of function following brain damage. However, most such claims are based on examining the effects of EC on acquisition of a new task following brain injury. Elsewhere we have argued that since this paradigm fails to establish a preoperative behavioural baseline against which to compare subsequent performance it may demonstrate compensation but cannot provide evidence of recovery. The present study directly addresses this issue by examining the effects of postoperative EC both on performance of a preoperatively acquired water maze escape response as well as on de novo acquisition of such a response in rats with bilateral occipital and sham lesions. In terms of swim times postoperative EC was found to significantly improve the performance of subjects which had not been preoperatively trained but not the performance of those subjects which had. However, in terms of a trials to criterion measure postoperative EC benefitted animals in both the preoperative and postoperative training conditions. The results, therefore, support the view that what has been observed in most previous studies is EC-induced compensation rather than recovery and also help to define the conditions under which this occurs. However, they also argue for further investigation of the hypothesis that postoperative EC may enhance recovery of lesion-impaired performance consistency.