Does the visual MMN develop independently by the auditory MMN? The case of Deafness

In deafness auditory cortices seem to be cross-modally recruited for the processing of other sensory modalities. Evidence from blindness suggests that these reorganized areas could maintain their functional specialization. The present study aimed at testing such functional selectivity hypothesis using the visual mismatch negativity (vMMN) as a tool. We presented a visual oddball paradigm to a group of early deaf (N=12) and a group of controls (N=12). Our hypothesis was that the vMMN topography in deaf individuals would suggest the recruitment of auditory areas. Stimuli consisted in the deformation of a circle into an ellipse either in the horizontal or in the vertical direction. In each block the standard stimulus was the deformation of the circle in one direction (73% of the trials) while the deviant stimulus was the deformation in the other direction (14 % of trials). Visual features of the standards and deviants were counterbalanced between blocks. Participants were instructed to fixate a central cross and detect whenever it disappeared. Strikingly, the results showed that the vMMN displayed a difference in topography between groups (more anteriorly distributed in deaf than controls within the 150-300ms time range), confirming the possibility of recruitment of auditory cortices in the deaf. SCDs, dipole fitting, and source estimates strongly suggested additional temporal plane generators in the deaf. These results show that the vMMN can develop also in the absence of audition and are compatible with a cross-modal recruitment of temporal cortices for motion change detection in case of auditory deprivation.