People who are deaf from an early age may develop stronger peripheral vision as their brains adapt to the absence of hearing, new research suggests.
Scientists from the University of Sheffield and the University of York studied how lifelong deafness affects visual processing. Their findings may explain why some D/deaf adults detect movement outside their direct line of sight more effectively.
This ability could help people notice movement around them. It may also help them spot potential dangers without looking directly at them.
Brain Devotes More Resources to Peripheral Vision
Researchers used functional MRI scans to study 32 adults. The group included 16 people with early, profound deafness. It also included 16 hearing adults of similar ages.
The researchers tested how the participants’ brains processed different parts of their visual field. They focused on two important areas of the visual system.
One area was the primary visual cortex. The other was the lateral geniculate nucleus, or LGN. The LGN helps relay visual information between the eyes and the brain.
The scans showed stronger activity linked to far-peripheral vision among the D/deaf participants. This pattern appeared in both brain regions.
The researchers did not simply find more visual activity overall. Instead, the brain appeared to shift its resources.
It devoted more processing power to the edges of the visual field. At the same time, it devoted less to central vision.
Deafness May Change How the Brain Processes Sight
The findings highlight the brain’s ability to adapt to major changes in sensory input. Scientists call this ability neuroplasticity.
People who grow up without hearing often rely heavily on visual information. The brain may therefore adjust its visual system to make better use of that information.
Professor Charlotte Codina leads orthoptics and ophthalmology at the University of Sheffield. She said the research shows how strongly the brain can adapt to its sensory environment.
Codina also said the findings could help scientists understand how the brain responds to sensory loss.
The study involved only a small group of participants. Therefore, researchers need more studies to determine how common this pattern is among D/deaf people.
What the Research Could Mean
The study adds to growing research into neuroplasticity. The brain can change its organisation and function in response to experience.
For people with lifelong deafness, visual information can play an important role in everyday life. The brain may adjust its visual processing system as a result.
The findings may also help researchers understand how the brain handles the loss of one sensory input. In some cases, another sensory system may receive more attention.
However, the researchers have not shown that every deaf person has superior peripheral vision. Their study examined a specific group of adults with early, profound deafness.
Further research could show how age, hearing level and individual experience affect these changes.
The study appeared in the Proceedings of the National Academy of Sciences.
