Age, experience, injury, and the changing brain

The fundamental concept in the emerging field of rehabilitation and brain plasticity is that although there is much constancy in brain function and organization across our lifetime, there is remarkable variability as well. This variability reflects the brain's capacity to alter its structure and function in reaction to environmental diversity as well as to perturbations including injury throughout the lifespan. Although the term brain plasticity is now widely used, it is not easily defined and is used to refer to changes at many levels in the nervous system ranging from molecular events, such as changes in gene expression, to behavior (e.g., Shaw & McEachern (Eds.) [2001]. Toward a Theory of Neuroplasticity. Philadelphia, USA: Psychology Press). The focus of our work has been to correlate changes in behavior, neuronal morphology, and the organization of motor maps after cortical injury throughout the lifespan. In this article, we review evidence we have collected from a rat model of normal development and the effects of brain injury, and comment on the general principals that may apply to human stroke and amblyopia.