Brain damage, behavior, rehabilitation, recovery, and brain plasticity

This paper focuses on roles of behavior, both in response to debilitation and in response to therapeutic intervention, in brain and behavioral recovery from brain damage. Recent evidence suggests that the brain damaged animal's behavior may often play a greater role in the recovery process than has been evident in previous work. In many cases, what may initially appear to be “spontaneous” brain adaptations to damage may be mediated by behavioral attempts to compensate for the effects of damage. This is seen in changes in the use of forelimbs following unilateral damage of the adult rat sensorimotor forelimb cortex, which have been shown to be essential to the dendritic growth and synaptogenesis that occurs in the contralateral hemisphere. In other cases, behavioral training can allocate new tissue to the functions targeted by training. In the case of global damage resulting from neonatal alchohol exposure, a therapeutic motor training intervention that “forces” the subject's involvement appears more effective than previous interventions that merely allowed the subjects to passively engage in activity. Properties of the brain damage also affect the recovery process (e.g., sensitizing both damaged and undamaged brain regions to the effects of behavioral compensation). While this paper emphasizes plastic mechanisms associated with active learning, we also review the evidence that mere physical exercise may stimulate protective mechanisms that contribute to both recovery from damage and successful aging. Exercise may protect the brain by regulating trophic and angiogenic processes across the life span, and, because of this, excercise may deserve greater attention in integrated treatment approaches in Parkinson's disease. MRDD Research Reviews 1998;4:231–237, 1998. © 1998 Wiley-Liss, Inc.