Auditory, tactile, and audiotactile information processing following visual deprivation

We highlight the results of those studies that have investigated the plastic reorganization processes that occur within the human brain as a consequence of visual deprivation, as well as how these processes give rise to behaviorally observable changes in the perceptual processing of auditory and tactile information. We review the evidence showing that visual deprivation affects the establishment of the spatial coordinate systems involved in the processing of auditory and tactile inputs within the peripersonal space around an individual. In blind individuals, the absence of a conjoint activation of external coordinate systems across modalities co-occurs with a higher capacity to direct auditory and tactile attentional resources to different spatial locations and to ignore irrelevant distractors. Both processes could thus contribute to the reduced spatial multisensory binding that has been observed in those who are blind. The interplay between auditory and tactile information in visually deprived individuals is modulated by attentional factors. Blind individuals typically outperform sighted people in those tasks where the target is presented in one sensory modality (and the other modality acts as a distractor). By contrast, they are less efficient in tasks explicitly requiring the combination of information across sensory modalities. The review highlights how these behavioral effects are subserved by extensive plastic changes at the neural level, with brain areas traditionally involved in visual functioning switching and being recruited for the processing of stimuli within the intact residual senses. We also discuss the roles played by other intervening factors with regard to compensatory mechanisms, such as previous visual experience, age at onset of blindness, and learning effects.