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Subject: NIH STUDY SHOWS THE DEAF BRAIN PROCESSES TOUCH DIFFERENTLY

U.S. Department of Health and Human Services NATIONAL INSTITUTES OF HEALTH
NIH News National Institute on Deafness and Other Communication Disorders
(NIDCD) <http://www.nidcd.nih.gov/>
Embargoed for Release: Tuesday, July 10, 2012, 5 p.m. EDT   

CONTACT:  Robin Latham, NIDCD Office of Health Communication and Public
Liaison, 301-496-7243,<e-mail:[log in to unmask]>

NIH STUDY SHOWS THE DEAF BRAIN PROCESSES TOUCH DIFFERENTLY Lacking sound
input, the primary auditory cortex "feels" touch

People who are born deaf process the sense of touch differently than people
who are born with normal hearing, according to research funding by the
National Institutes of Health.  The finding reveals how the early loss of a
sense- in this case hearing-affects brain development. It adds to a growing
list of discoveries that confirm the impact of experiences and outside
influences in molding the developing brain. The study is published in the
July 11 online issue of The Journal of Neuroscience.

The researchers, Christina M. 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 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.  

"This research shows how the brain is capable of rewiring in dramatic ways,"
said James F. Battey, Jr., M.D., Ph.D., director of the NIDCD. "This will be
of great interest to other researchers who are studying multisensory
processing in the brain." 

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. Deaf people may process vision
using many different brain regions, especially auditory areas, including the
primary auditory cortex. 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.   

Dr. Karns and her colleagues developed a unique apparatus that could be worn
like headphones while subjects were in a magnetic resonance imaging (MRI)
scanner. 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. Visual stimuli-brief pulses of light-were delivered
through fiber optic cables mounted directly below the air-puff nozzle.
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. 

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. 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. Subjects were also exposed to tactile
stimuli and light stimuli separately and time-periods without stimuli to
establish a baseline for brain activity.

Hearing people exposed to two puffs of air and one flash of light claimed
only to see a single flash. However, when exposed to the same mix of
stimuli, the subjects who were deaf saw two flashes. Looking at the brain
scans of those who saw the double flash, the scientists observed much
greater activity in Heschl's gyrus, although not all deaf brains responded
to the same degree.  The deaf individuals with the highest levels of
activity in the primary auditory cortex in response to touch also had the
strongest response to the illusion.   

"We designed this study because we thought that touch and vision might have
stronger interactions in the auditory cortices of deaf people," said Dr.
Karns." As it turns out, the primary auditory cortex in people who are
profoundly deaf focuses on touch, even more than vision, in our experiment."

There are several ways the finding may help deaf people. For example, if
touch and vision interact more in the deaf, touch could be used to help deaf
students learn math or reading. The finding also has the potential to help
clinicians improve the quality of hearing after cochlear implants,
especially among congenitally deaf children who are implanted after the ages
of 3 or 4. These children, who have lacked auditory input since birth, may
struggle with comprehension and speech because their auditory cortex has
taken on  the processing of other senses, such as touch and vision. These
changes may  make it more challenging for the auditory cortex to recover
auditory processing function after cochlear implantation. Being able to
measure how much the auditory cortex has been taken over by other sensory
processing could offer doctors insights into the kinds of intervention
programs that would help the brain retrain and devote more capacity to
auditory processing. 

This research was supported with NIDCD funding 5R01DC000128-34, and by
Recovery Act supplement R01DC000128-32S1.

NIDCD supports and conducts research and research training on the normal and
disordered processes of hearing, balance, taste, smell, voice, speech and
language and provides health information, based upon scientific discovery,
to the public. For more information about NIDCD programs, see the Web site
at www.nidcd.nih.gov.

About the National Institutes of Health (NIH): NIH, the nation's medical
research agency, includes 27 Institutes and Centers and is a component of
the U.S. Department of Health and Human Services. NIH is the primary federal
agency conducting and supporting basic, clinical, and translational medical
research, and is investigating the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and its programs,
visit <www.nih.gov>.

 NIH...Turning Discovery into Health
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