Subjects were also exposed to tactile stimuli and light stimuli separately and time-periods without stimuli to establish a baseline for brain activity. In their experiment, the researchers used a double puff of air as a tactile stimulus to replace the auditory stimulus, but kept the single flash of light.
The researchers took advantage of an already known perceptual illusion in hearing people known as the auditory induced double flash, in which a single flash of light paired with two or more brief auditory events is perceived as multiple flashes of light. Functional MRI was used to measure reactions to the stimuli in Heschl’s gyrus, the site of the primary auditory cortex in the human brain’s temporal lobe as well as other brain areas. Visual stimuli-brief pulses of light-were delivered through fiber optic cables mounted directly below the air-puff nozzle. Flexible tubing, connected to a compressor in another room, delivered soundless puffs of air above the right eyebrow and to the cheek below the right eye. Karns and her colleagues developed a unique apparatus that could be worn like headphones while subjects were in a magnetic resonance imaging (MRI) scanner. However, no one has tackled whether vision and touch together are processed differently in deaf people, primarily because in experimental settings, it is more difficult to produce the kind of precise tactile stimuli needed to answer this question.ĭr. Deaf people may process vision using many different brain regions, especially auditory areas, including the primary auditory cortex. Previous research, including studies performed by the lab director, Helen Neville Ph.D., has shown that people who are born deaf are better at processing peripheral vision and motion. “This will be of great interest to other researchers who are studying multisensory processing in the brain.” Battey, Jr., M.D., Ph.D., director of the NIDCD. “This research shows how the brain is capable of rewiring in dramatic ways,” said James F. The finding suggests that since the developing auditory cortex of profoundly deaf people is not exposed to sound stimuli, it adapts and takes on additional sensory processing tasks. Karns, Ph.D., a postdoctoral research associate in the Brain Development Lab at the University of Oregon, Eugene, and her colleagues, show that deaf people use the auditory cortex to process touch stimuli and visual stimuli to a much greater degree than occurs in hearing people. The study is published in the July 11 online issue of The Journal of Neuroscience. It adds to a growing list of discoveries that confirm the impact of experiences and outside influences in molding the developing brain. The finding reveals how the early loss of a sense- in this case hearing-affects brain development. People who are born deaf process the sense of touch differently than people who are born with normal hearing, according to research funded by the National Institutes of Health. At center is the superior temporal region, which contains the human auditory cortex.
This graphic of a human brain is derived from multiple structural magnetic resonance images.