Changes in the Central Auditory System with Deafness and Return of Activity via a Cochlear Prosthesis

It is well established that sensory deprivation during development results in lasting changes in the central nervous system (CNS) (Wiesel and Hubel. 1963). This is certainly the case for the auditory system where in developing animals, sound deprivation and/or cochlear ablation are especially potent means of producing significant neuronal atrophy and reorganization in central structures (Rubel et al., 1984). The loss of afferent input often occurs in the adult auditory system and there is increasing evidence that the mature central auditory system (CAS) also displays substantial changes in structure and function following deafferentation (Gerken, 1979; Rajan et al., 1993, 1996, Willott et al., 1994). However, despite the high incidence of inner ear pathology and a growing utilization of the cochlear prosthesis in deaf adults, little is known about the effects of cochlear damage on the mature CAS, the mechanisms underlying CNS physiological changes produce by deafness, or how deafness induced changes may affect processing with subsequent reactivation of the CAS via a cochlear prosthesis. Elucidating how the CAS responds to such deafferentation is fundamental to our understanding the mechanisms of plasticity and homeostasis of the brain throughout an organisms lifetime.