Experience-dependent plasticity in the developing brain

The extent to which individual experiences can shape our cognitive and emotional behaviour has been an issue of intense debate and study for centuries, and the topic takes on different forms depending on the field of study. Any form of behaviour will depend on the existence of functional connections in the brain, linking inputs and outputs. If these connections are damaged, or in any way silenced or suppressed, the related behaviour will be impaired, or modified accordingly. A large part of ontogenesis is devoted to the formation of such connections within and between different brain structures. Whereas the initial formation of connections is largely determined by chemical guidance factors and thus genetically specified, the ensuing neuronal circuits remain ‘plastic’ or modifiable for a prolonged period and, in some cases, throughout life. In this paper, I define notions of plasticity from a neurobiological perspective. I use the example of experience-dependent plasticity in multisensory convergence and integration in the brain, in order to illustrate the extent and limitations of the role of experience in sculpting neuronal circuits. I then describe briefly the various mechanisms that are thought to underlie experience-dependent changes in brain circuits during early development. D 2002 Elsevier Science B.V. All rights reserved