Sight sounds off in brains of the deaf

The brain increasingly looks like a sensory opportunist. Deprive the master organ of access to sounds, a new study finds, and it reorganizes so that tissue typically consigned to handling acoustic information instead joins the visual system.

That resilient strategy plays out in the brains of young adults who have been deaf for all or most of their lives, according to brain-imaging data slated to appear in Nature Neuroscience. Three brain regions that handle incoming sounds–each located on the right side of the so-called auditory cortex–showed surges of activity as deaf volunteers completed visual tasks, report psychologist Eva M. Finney of the University of California, San Diego and her colleagues.

The researchers used functional magnetic resonance imaging to study six deaf and six hearing adults. The technique tracks brain activity by measuring changes in blood flow throughout the brain. Each group contained three men and three women.

While viewing moving dot patterns on a computer screen, only deaf participants displayed increased activity in the acoustic cortex, the researchers say. One of the affected areas included tissue within the neural gateway for incoming acoustic information in hearing individuals.

Nearly as much activation of the auditory cortex occurred when deaf volunteers tried ignoring the moving dots and instead tracked the brightness of a stationary dot on the screen.

Other findings about the brain’s cross-sensory talents have recently emerged (SN: 9/29/01, p. 204: Joined at the Senses). In particular, the new data dovetail with a report that sounds from sources in motion stimulate extra activity in the right visual cortex of blind people.