30 - Functional Brain Reorganization and Recovery after Injury to White Matter

Abstract

This chapter discusses functional brain reorganization and recovery after injury to white matter. It primarily focuses on motor recovery. The brain has a limited repertoire of responses to brain injury. Three general mechanisms for recovery can be defined: (1) repair; (2) compensation; and (3) adaptation. The relative contributions of these different mechanisms to recovery change with the nature of the pathology and its context. Motor learning by the healthy brain provides a basis for understanding adaptive functional reorganization of the brain after injury. A number of special mechanisms may alter the potential for functional reorganization in the context of brain injury. Studies in the healthy brain suggest that functional reorganization in motor cortex could be strongly affected by γ-aminobutyric acid activity, as well as the excitatory glutaminergic system acting through N-methy D-aspartate (NMDA) receptors. Adaptive functional reorganization is an example of the more general phenomenon of “plasticity.” Postinjury reorganization depends to a significant extent on modifications to existing pathways rather than the development of entirely new circuits that may be used to only a minor extent by the healthy brain or only under different conditions. A potentially important brain region mediating recovery is the cerebellum. The cerebellum has a well-described and key role in functional plasticity of the motor system during skill learning by the healthy brain. Cerebellar pathways have been implicated in circuitry mediating recovery and could be particularly important for adaptive responses to injury because of their high intrinsic synaptic plasticity.