Researchers find the blind use visual brain area to improve other senses

Oct 06, 2010

People who have been blind from birth make use of the visual parts of their brain to refine their sensation of sound and touch, according to an international team of researchers led by neuroscientists at Georgetown University Medical Center (GUMC).

Published today in the journal Neuron, the scientists say this finding helps explain why the blind have such advanced of these senses – abilities that far exceed people who can see, they say.

Using functional magnetic resonance imaging (fMRI), the researchers found that the blind use specialized "modules" in the visual cortex that process the spatial location of an object when a person localizes it in space. More generally, they believe that the different functional attributes that make up vision, such as analysis of space, patterns, and motion, still exist in the visual cortex of blind individuals. But instead of using those areas to understand what the eyes see, the blind use them to process what they hear and touch because the same components are necessary to process information from those senses.

"We can see that in the blind, large parts of the visual cortex light up when participants are engaged in auditory and tactile tasks. This is in addition to the areas in their that are dedicated to processing sound and touch," says the study's lead investigator, Josef P. Rauschecker, PhD, professor in the Department of Physiology and Biophysics at GUMC.

"This shows us that the visual system in the blind retains the functional organization that was anatomically laid out by genetics, but that the brain is plastic enough to use these modules to analyze input they receive from different senses,' he says.

In this experiment, which included researchers from Belgium and Finland, 12 sighted and 12 blind participants agreed to perform a set of auditory or tactile tasks. "We know that in the blind, the brain reroutes other sensory inputs to unused portions of the brain to compensate for loss of sight, but we wondered what specifically the visual cortex in these individuals was doing," Rauschecker says. "The visual cortex is one of the largest and most powerful parts of the brain, with about 40 different specialized modules. By comparison, the auditory processing center in the brain only has about 20 modules."

In one task, volunteers wore stereo headphones while in the fMRI machine, and they reported where in space the variety of sounds they heard came from. In the other test, they wore piezo-electric vibrators on each finger, and the goal was to report which finger was being gently stimulated.

"We found that the visual cortex in the blind was much more strongly activated than it was in the sighted, where visual cortex was mostly deactivated by sounds and touch," Rauschecker says. "Furthermore, there was a direct correlation between brain activity and performance in the blind. The more accurate blind people were in solving the spatial tasks, the stronger the spatial module in the visual cortex was activated.

"That tells us that the in the blind takes on these functions and processes sound and tactile information which it doesn't do in the sighted," he says. "The neural cells and fibers are still there and still functioning, processing spatial attributes of stimuli, driven not by sight but by hearing and touch. This plasticity offers a huge resource for the blind."

Clinically, the results suggest that these powerful senses may potentially be harnessed to help the blind better navigate in their world, Rauschecker says. For example, GUMC researchers, collaborating with colleagues in Belgium, are developing goggles that process visual stimuli and turn them into auditory cues that help guide the blind. This sensory substitution device is now being tested in volunteers.

Explore further: Lost memories might be able to be restored, new study indicates

Related Stories

Adult brain can change, study confirms

Sep 05, 2007

It is well established that a child's brain has a remarkable capacity for change, but controversy continues about the extent to which such plasticity exists in the adult human primary sensory cortex. Now, ...

Wired for sound: How the brain senses visual illusions

Apr 11, 2007

In a study that could help reveal how illusions are produced in the brain's visual cortex, researchers at the UCSD School of Medicine have found new evidence of rapid integration of auditory and visual sensations in the brain. ...

Do the blind have a more acute sense of smell?

Apr 26, 2010

An ongoing study by Mathilde Beaulieu-Lefebvre, a graduate student from the Universite de Montreal Department of Psychology, has debunked the myth that the blind have a more acute sense of smell than the sighted. Vision loss ...

Recommended for you

Researchers unlock mystery of skin's sensory abilities

Dec 19, 2014

Humans' ability to detect the direction of movement of stimuli in their sensory world is critical to survival. Much of this stimuli detection comes from sight and sound, but little is known about how the ...

Tackling neurotransmission precision

Dec 18, 2014

Behind all motor, sensory and memory functions, calcium ions are in the brain, making those functions possible. Yet neuroscientists do not entirely understand how fast calcium ions reach their targets inside ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.