Specificities of Cortical Processing of Visual Information in Subjects with Hearing Deprivation (Congenital Deafness)

In this study, systemic neurophysiological and neuropsychological mechanisms providing processing of visual information in subjects suffering from auditory deprivation were examined. In 30 men (21 to 25 year old) with complete congenital deafness and 30 control normally hearing men of the same age (groups D and C, respectively), cortical visual evoked potentials (VEPs, photostimulation of the right and left eyes by LED flashes, recording from the O1 and O2 loci) and neurodynamic characteristics of processing of visual information within the go/nogo/go paradigm were analyzed. Under conditions of the respective tests, all indices that characterize processing of simple visual information in deaf subjects (including number of processed stimuli, minimum exposure of the signal, and number of errors) were significantly worse than in the control group. It was also found that median values of the latency of the early VEP components (P1, N1, and P2) in group D were significantly smaller than the respective values in group C. At the same time, median latencies of the late VEP waves (N2 and P3) in deaf subjects were significantly greater than the analogous C-group values. Median values of the peak-to-peak amplitudes of all, with no exceptions, VEP components in group D were significantly (two times or even more) smaller than those in control subjects. Patterns of correlations between the indices of visual information processing and time/amplitude parameters of visual VEPs in the examined groups noticeably differed from each other. Thus, specific brain mechanisms responsible for processing of visual information in persons with auditory deprivation and with normal hearing demonstrate significant dissimilarity; central mechanisms of the visual system in deaf subjects undergo considerable cross-modality modifications.