The Brain Spreads Its Sights in the Deaf
Bower, B., Science News
People often assume that the deaf, because they live in a silent world, compensate by seeing more vividly or clearly than the hearing do. Yet scientists know little about the visual capacities of deaf people.
A new study finds that compared with hearing adults, people who have been deaf from birth display a unique pattern of activity in the brain's visual system that may strengthen their peripheral vision.
A brain area implicated in tracking objects that move on the fringes of a person's visual field exhibits elevated activity in deaf individuals, says a team of neuroscientists led by Daphne Bavelier of the University of Rochester. This brain response arises from deaf people's unusually high reliance on peripheral vision, the researchers propose. For instance, they note, deaf people regularly scan their surroundings to compensate for the absence of acoustic cues and typically monitor the arm and hand motions of sign language with peripheral vision while looking at a conversation partner's eyes.
The scientists report their findings in the Sept. 1 JOURNAL OF NEUROSCIENCE. "This is exciting because it's the first study to show a specific neural substrate for visual perception in the deaf," remarks Karen R. Dobkins, a psychologist at the University of California, San Diego.
The researchers studied 9 deaf and 11 hearing adults, ages 18 to 27. Deaf participants had been born unable to hear, had deaf parents, and had acquired American Sign Language as their native language.
In a series of trials, each volunteer watched sets of moving dots either on the periphery or in the center of the visual field. The participants indicated when the dots' brightness changed. At the same time, a functional magnetic resonance imaging device monitored participants' brain activity. …