Adaptation of the communicative brain to post-lingual deafness. Evidence from functional imaging.

Not having access to one sense profoundly modifies our interactions with the environment, in turn producing changes in brain organization. Deafness and its rehabilitation by cochlear implantation offer a unique model of brain adaptation during sensory deprivation and recovery. Functional imaging allows the study of brain plasticity as a function of the times of deafness and implantation. Even long after the end of the sensitive period for auditory brain physiological maturation, some plasticity may be observed. In this way the mature brain that becomes deaf after language acquisition can adapt to its modified sensory inputs. Oral communication difficulties induced by post-lingual deafness shape cortical reorganization of brain networks already specialized for processing oral language. Left hemisphere language specialization tends to be more preserved than functions of the right hemisphere. We hypothesize that the right hemisphere offers cognitive resources re-purposed to palliate difficulties in left hemisphere speech processing due to sensory and auditory memory degradation. If cochlear implantation is considered, this reorganization during deafness may influence speech understanding outcomes positively or negatively. Understanding brain plasticity during post-lingual deafness should thus inform the development of cognitive rehabilitation, which promotes positive reorganization of the brain networks that process oral language before surgery. This article is part of a Special Issue entitled Human Auditory Neuroimaging.