Impact of visual and auditory deprivation on speech perception: an EEG study

This study investigated the impact of auditory and visual deprivation on speech processing by analyzing auditory evoked potentials (MMN, P3a, P2, N2b) in congenitally blind individuals, cochlear implant (CI) users, and normal-hearing controls. Using a passive oddball paradigm with /u/ as the standard stimulus and /i/ and /y/ as deviants, we recorded and analyzed auditory evoked potentials in fronto-central and centro-parietal regions. Blind participants exhibited significantly faster MMN and N2b latencies than controls and CI users, reflecting enhanced auditory temporal resolution due to cross-modal plasticity. CI users showed reduced P2 and N2b amplitudes, indicating challenges in early sensory processing and conflict monitoring, particularly for the /i/-/u/ contrast. Notably, blind participants had larger P3a amplitudes, emphasizing superior attentional engagement in response to deviant stimuli. Postlingually deafened CI users exhibited greater P3a amplitudes than prelingually deafened users, underscoring the impact of early auditory experiences on cortical responses. These findings demonstrate distinct effects of sensory deprivation on speech processing, with blind individuals showing compensatory neural mechanisms and CI users experiencing sensory and cognitive challenges. The results underscore the need for personalized rehabilitation strategies to enhance outcomes for populations with sensory deprivation and highlight the potential of cross-modal plasticity in auditory rehabilitation.