Event-related Potentials Reveal Early Visual-tactile Integration in the Deaf

This study examined visual-tactile perceptual integration in deaf and normal hearing individuals. Participants were presented with photos of faces or pictures of an oval in either a visual mode or a visual-tactile mode in a recognition learning task. Event-related potentials (ERPs) were recorded when participants recognized real faces and pictures of ovals in learning stage. Results from the parietal-occipital region showed that photos of faces accompanied with vibration elicited more positive-going ERP responses than photos of faces without vibration as indicated in the components of P1 and N170 in both deaf and hearing individuals. However, pictures of ovals accompanied with vibration produced more positive-going ERP responses than pictures of ovals without vibration in N170, which was only found in deaf individuals. A reversed pattern was shown in the temporal region indicating that real faces with vibration elicited less positive ERPs than photos of faces without vibration in both N170 and N300 for deaf, but such pattern did not appear in N170 and N300 for normal hearing. The results suggest that multisensory integration across the visual and tactile modality involves more fundamental perceptual regions than auditory regions. Moreover, auditory deprivation played an essential role at the perceptual encoding stage of the multisensory integration.