Summary

Brain plasticity refers to the potential for the brain to change physically, chemically or physiologically to adapt to environmental change and to compensate for brain perturbations such as injury. Although there is a tendency to perceive plasticity as a singular change in which synapses are added or subtracted, experience-dependent change in the nervous system is much more complex and it is clear that experience modulates plasticity in unpredictable ways. Thus, the same experience can have different effects at different ages, in the two sexes, in the two hemispheres and in different cortical layers and regions. Many of these differential changes present a paradox in that they are not predictable a priori. The challenge is to understand how plastic changes occur, which ultimately will be at the level of gene expression, so that the rules governing brain plasticity can be written.

Introduction

Behavioural neuroscience has been guided throughout the twentieth century by the principle of localization of function. One underlying assumption has been that there are continuously adaptive responses to the experiences that challenge the cerebral cortex – processes referred to as plasticity. For example, if we learn a motor skill such as playing the piano, there are correlated changes in the organization of the motor representations of the fingers in the cerebral cortex. Indeed, it is likely that the increasing dexterity of the fingers as the piano-playing skill improves occurs because of the changed motor representation.