Lifelong deafness may alter how brain processes vision
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Researchers in the UK studied how brains adapt in people who have been profoundly deaf since early childhood. They found that these individuals dedicate more brain activity to processing information from the edges of their field of view, potentially as an early warning system in the absence of sound. The team compared the brains of 16 deaf adults to 16 hearing adults using MRI scans.
The scientists examined two key brain regions, the lateral geniculate nucleus (LGN) and the primary visual cortex (V1), to understand how visual information is processed. They mapped brain activity to different parts of a person’s visual field, dividing it into concentric slices to analyze which brain regions respond most strongly to specific areas of vision. The study revealed that the LGN in deaf adults showed a stronger bias towards processing peripheral vision compared to hearing adults.
Although the total volume of the LGN and V1 did not differ between the two groups, the distribution of activity within V1 was different. Deaf participants exhibited greater neural preference for peripheral vision, while hearing participants favored central vision. These differences appeared to be linked to changes in the surface area of the visual cortex, not its thickness. The researchers suggest this reorganization reflects the brain’s ability to compensate for a lack of auditory input by enhancing visual processing.
They also noted that people who learned British Sign Language (BSL) as their first language showed the most pronounced increase in peripheral vision preference, and that differences in brain structure may originate in the retina.
