© Oxford University Press, 2015. This chapter discusses the behavioral mechanisms of use-dependent cortical reorganization for the enhancement of purposive movement, particularly in regard to rehabilitation after neurological injury. It shows that cortical reorganization is opportunistic; when input to the central nervous system (CNS) changes, the CNS rapidly adapts. Deficient afferentation from one body region is responded to by augmenting the cortical representation of adjoining regions. Increased utilization of a body region is responded to by expanding its cortical representation. These changes are probably fundamental to adaptation to the diverse demands placed upon the organism by the environment and therefore have substantial survival value.