Abstract
In deaf people, the auditory cortex can reorganize to support visual motion processing. Although this cross-modal reorganization has long been thought to subserve enhanced visual abilities, previous research has been unsuccessful at identifying behavioural enhancements specific to motion processing. Recently, research with congenitally deaf cats has uncovered an enhancement for visual motion detection. Our goal was to test for a similar difference between deaf and hearing people. We tested 16 early and profoundly deaf participants and 20 hearing controls. Participants completed a visual motion detection task, in which they were asked to determine which of two sinusoidal gratings was moving. The speed of the moving grating varied according to an adaptive staircase procedure, allowing us to determine the lowest speed necessary for participants to detect motion. Consistent with previous research in deaf cats, the deaf group had lower motion detection thresholds than the hearing. This finding supports the proposal that cross-modal reorganization after sensory deprivation will occur for supramodal sensory features and preserve the output functions.
Highlights
Most people are familiar with the popular idea that the loss of one sense, such as vision or audition, can lead to enhancements of the remaining senses
We found that people with early and profound deafness have lower thresholds for visual motion detection compared to people with normal hearing
This finding is consistent with previous research in congenitally deaf cats, where this enhanced visual ability is supported by activity in auditory regions [27]
Summary
Most people are familiar with the popular idea that the loss of one sense, such as vision or audition, can lead to enhancements of the remaining senses This idea is supported anecdotally and scientifically, in the domain of visual deprivation. Researchers have documented behavioural enhancements to specific aspects of auditory, tactile, and olfactory processing (for reviews, see [1,2]) In some instances, these enhancements have been attributed directly to cross-modal processing in the visual cortex – with no visual input, brain regions that are normally devoted to vision reorganize to process incoming auditory information Similar cross-modal neural recruitment has been found in deaf people, with increased responsiveness of the superior temporal cortex in response to visual information, to visual motion stimuli [5,6,7,8,9,10]. This cross-modal activity in deaf people is believed to support some enhanced visual abilities [11], the exact behavioural correlates of this activity have yet to be fully understood
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