Early deafness may reshape the brain to devote more resources to peripheral vision

by Krystal Kasal, Medical Xpress

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People with intact hearing can use sound as an alert system for events outside their direct line of sight. This seemingly puts those who have lost their hearing at a disadvantage. However, according to a new study published in Proceedings of the National Academy of Sciences, the brains of people who lose their hearing at an early age may compensate by devoting more resources to developing better peripheral vision.

How the loss of one sense sharpens others

Scientists know that the loss of one sense often sharpens others, thanks to plasticity in the brain. For example, researchers have found that the visual cortex in blind people can process nonvisual information obtained from other senses. Some earlier research even indicated that early deafness can sharpen some peripheral-vision skills.

However, it was unclear whether this advantage changed the brain's earliest visual-processing pathways. Some behavioral studies had found the strongest differences between deaf and hearing people in far-peripheral vision, but studies involving the primary visual cortex gave mixed results. This was partially because they did not map vision far enough into the periphery.

The authors of the new study write, "In D/deaf adults, structural changes as early in the visual pathways as the retina have also been correlated with enhanced far-peripheral sensitivity, further supporting the possibility that early visual structures downstream may also be affected. Previous studies evaluating primary visual cortex have found either no difference between deaf and hearing groups or thinner visual cortex representing the peripheral visual field. Critically, however, these studies were confined to comparisons within a limited visual field (<37.5°), rather than the far periphery where differences in visual sensitivity are most prominent and potentially beneficial."

A shift in neural resources

To study the neural mechanisms in early visual-processing areas related to enhanced peripheral vision in D/deaf adults, the team used functional MRI to map responses across a wide visual field. The study included 16 profoundly deaf adults who lost their hearing early and 16 age-matched hearing adults. The participants watched moving checkerboard patterns extending to 72 degrees from the center of their gaze as the researchers tested responses in their brains. The team measured visual-field maps in the primary visual cortex and the lateral geniculate nucleus (LGN), a part of the brain that relays retinal signals to the cortex.

The results showed that deaf participants devoted a larger share of their primary visual cortex to the far edges of vision than hearing participants. Meanwhile, a smaller share was devoted to central vision, indicating a redistribution rather than overall brain-region growth. The same peripheral shift appeared in the visual relay center of the thalamus, suggesting the change begins early in the visual pathway.

Despite the reorganization, the total volume of both the primary visual cortex and thalamic relay center did not differ between groups. Instead of a thicker cortex, the team found that the cortex's expanded far-peripheral representation was due to greater surface area.

The study authors write, "This central/peripheral trade-off in neural resources may explain behavioral differences reported between D/deaf and hearing individuals where numerous behavioral studies demonstrate superior visual sensitivity in early D/deaf individuals, particularly to far-peripheral stimuli."

The team notes that the study does not prove exactly when or how the remapping developed because the participants were studied at only one point during adulthood. The wide-field MRI method also had lower precision for the very center of vision and at the outer edge of the map.

A boost from sign language?

Although the group size was too small for a firm conclusion, the researchers found that early and extensive sign-language experience may strengthen this shift toward enhanced peripheral vision. Most deaf participants used British Sign Language (BSL). The researchers divided them into three groups: five people whose first language was BSL, eight people whose first language was English but who later learned and used BSL, and three with no sign-language experience. The team found that those with more sign-language experience tended to have even larger peripheral representations and smaller central representations.

"The comparison reveals that the peripheral representations are largest (and central representations smallest) in the group who learned BSL as a first language, followed by BSL users with English as a first language and then nonsigning D/deaf individuals. Although sample sizes are too small to compute valid statistics, there is a clear trend suggesting that use of a visual sign language contributes to the central/peripheral trade-off of visual field representations in V1," the study authors write.

Future studies may better separate the effects of deafness and sign-language experience, as well as genetics and everyday visual demands. Studies like this can help guide vision and mobility assessments designed for deaf people and provide context for visual alert systems, classroom design and workplace safety tools that make better use of peripheral cues.

Written for you by our author Krystal Kasal, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.

Publication details

Alexandra T. Levine et al, Retinotopic remapping of the visual system in deaf adults, Proceedings of the National Academy of Sciences (2026). DOI: 10.1073/pnas.2532413123

Journal information: Proceedings of the National Academy of Sciences

Key medical concepts

Primary Visual Cortex

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Neurology Who's behind this story?

Krystal Kasal

Freelance science writer with Master's in physics. Five years clinical research and physics education experience. Science communicator. Full profile →

Gaby Clark

MA in English, copy editor since 2021 with experience in higher education and health content. Dedicated to trustworthy science news. Full profile →

Robert Egan

Bachelor's in mathematical biology, Master's in creative writing. Well-traveled with unique perspectives on science and language. Full profile →

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