With Anu Sharma and Andrej Kral
Cross-modal neuroplasticity refers to the recruitment and repurposing of neuronal resources of one sensory modality by another. Our studies show evidence of cross-modal plasticity from visual and somatosensory modalities in deaf animals and children who are fitted with cochlear implants. Developmental cross-modal reorganization from both visual and somatosensory modalities appears to be related to developmental maturity of the central auditory system and is predictive of auditory, speech and cognitive outcomes in pediatric deafness. In young deaf adults who receive implants at later ages in childhood, cortical auditory development is delayed well into adulthood and these individuals show evidence of cross-modal plasticity as a function of their developmental auditory cortical immaturity. Cross-modal recruitment is not limited to bilateral congenital deafness, we find evidence of cross-modal recruitment by vision and somatosensation in animals and children with unilateral or single-sided deafness. Frontal cortical involvement co-occurs with visual and somatosensory re-organization, suggestive of top-down modulation of cross-modal mechanisms. Cross-modal plasticity may be reversed with appropriate intervention with hearing aids and cochlear implants. Overall, our research in animals and humans suggests that cross-modal plasticity in deafness is a dynamic, versatile and reversible process, resulting from existing sub-threshold multisensory inputs to sensory cortices and top-down influences on inhibition, which adaptively interacts with the restoration of sensory deprivation.