Deaf people use the region of the brain associated with hearing to sense vibrations, a new study shows. "These findings illustrate how altered experience can affect brain organization," says investigator Dean Shibata of the University of Washington. He presented his results yesterday at the annual meeting of the Radiological Society of North America.
Using functional magnetic resonance imaging (fMRI), Shibata scanned the brains of 10 deaf students and 11 students with normal hearing while they experienced intermittent vibrations on their hands. All the subjects showed activity in the region of the brain that processes vibrations. The deaf students, however, also exhibited activity in the auditory cortex, a golf-ball-size area used in hearing. "In someone who is deaf," he explains, "the young brain takes advantage of valuable real estate in the brain by processing vibrations in the part of the brain that would otherwise be used to process sound."
Because vibrations and sound have similar features, Shibata notes, it makes sense that the brain can adapt to replace one with the other in a processing region. What's more, he suggests, it may be helpful to expose deaf children to music and vibrations converted from speech sounds early in life while their brains are still developing.