Abstract
Auditory deprivation is known to be accompanied by alterations in visual processing. Yet not much is known about tactile processing and the interplay of the intact sensory modalities in the deaf. We presented visual, tactile, and visuo-tactile stimuli to congenitally deaf and hearing individuals in a speeded detection task. Analyses of multisensory responses showed a redundant signals effect that was attributable to a coactivation mechanism in both groups, although the redundancy gain was less in the deaf. In line with these behavioral results, on a neural level, there were multisensory interactions in both groups that were again weaker in the deaf. In hearing but not deaf participants, somatosensory event-related potential N200 latencies were modulated by simultaneous visual stimulation. A comparison of unisensory responses between groups revealed larger N200 amplitudes for visual and shorter N200 latencies for tactile stimuli in the deaf. Furthermore, P300 amplitudes were also larger in the deaf. This group difference was significant for tactile and approached significance for visual targets. The differences in visual and tactile processing between deaf and hearing participants, however, were not reflected in behavior. Both the behavioral and electroencephalography (EEG) results suggest more pronounced multisensory interaction in hearing than in deaf individuals. Visuo-tactile enhancements could not be explained by perceptual deficiency, but could be partly attributable to inverse effectiveness.
Highlights
For many decades, the sensory systems were studied in isolation to learn about the function of the visual, the auditory, and the tactile systems, amongst others
We found tactile P300 amplitudes to be significantly larger in deaf than in hearing participants whereas the group difference for visual P300 amplitudes pointed into the same direction approaching significance
The deaf participants showed larger N200 amplitudes in visual event-related potentials (ERPs) and shorter N200 latencies in somatosensory ERPs compared to hearing controls
Summary
The sensory systems were studied in isolation to learn about the function of the visual, the auditory, and the tactile systems, amongst others. Many deaf do not see themselves as impaired, but as members of a community with its own language, its own identity, and its own culture that needs to be preserved (see e.g., Paddy, 2003) In this spirit, the present study is not focusing on what is not working, but focusing on what might be different with deafness. How do the intact visual and tactile systems change due to altered sensory experiences as with deafness? The question of the extent to which the contribution of all sensory systems during maturation is necessary to develop the ability to integrate information from different sensory systems could be answered by looking at individuals who are deprived of one sensory input, such as the deaf
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