Unraveling the impact of congenital deafness on individual brain organization

Abstract

Research on brain plasticity, particularly in the context of deafness, consistently emphasizes the reorganization of the auditory cortex. However, a critical question arises: to what extent do all individuals with deafness show the same level of reorganization? To address this question, we examined the individual differences in deafness functional connectivity (FC), specifically from the deprived auditory cortex. Our findings demonstrate a remarkable differentiation between individuals deriving from the absence of shared auditory experiences, resulting in heightened FC variability among deaf individuals, compared to more consistent FC in the hearing group. Notably, this increased variability is particularly pronounced in regions where FC diverges between the deaf and hearing individuals, reflecting the individual differences in how the brain reorganizes in response to sensory deprivation. Additionally, connectivity to language regions also becomes more diverse in deafness across individuals. Importantly, this does not stem from delayed language acquisition, as it is found in deaf native signers, who are exposed to rich natural language since birth. Further, comparing FC diversity between deaf native signers and deaf delayed signers who were deprived of language in early development, we show that language experience also impacts individual differences, although to a more moderate extent. Overall, our research points out the intricate interplay between brain plasticity and individual differences, shedding light on the diverse ways reorganization manifests among individuals. It further joins findings in blindness, showing that individual differences are affected by sensory experience. Finally, these findings highlight the importance of considering individual differences in personalized rehabilitation for hearing loss.