How Deaf People's Brains Change To Boost Sight
After studying the brain congenitally deaf cats, the only animal besides humans that can be born deaf, the researchers suggested that part of the brain normally used for hearing reorganized to improve sight in blind people, which explains their ability to reported "supersight".
You can read how the researchers made their discovery in a paper that was published online in the journal Nature Neuroscience on October 10.
Lead author was Dr. Stephen G Lomber from the center of the brain and the mind at the University of Ontario in Canada, and his co-authors were Dr M Alex Meredith School of Medicine at Virginia Commonwealth University in the U.S. and Dr. Andrej Kral from Hannover Medical University Audioneurotechnology Institute in Germany.
When the brain receives input from one sense that does not work, he often compensate by increasing productivity another sense, it works: for example, deaf and blind people often report increased opportunities in other senses. But what remains a little unclear how this is happening neurologically.
As a result of what they found in congenitally deaf cats, Lomber and his colleagues suggested that the brain is "plastic" enough to redistribute the areas normally devoted to one sense of the further implementation of the rest.
Lomber, who is assistant professor of physiology and pharmacology at the Schulich School of Medicine and Dentistry, and Department of Psychology at the Faculty of Social Sciences, both at the University of Ontario, explained that the brains of deaf people are likely to use the surplus in the auditory region of the brain to improve performance in two ways Visual : increased peripheral vision and identify how quickly all around them are moving.
For example, he said: "If you are deaf, then it would be beneficial, seeing a car coming in far peripheral vision, because you do not hear the car approaching from the side, the same with the opportunity to more accurately determine how fast something is moving."
"The brain wants to compensate for the lost sense with accessories that are beneficial," said Lomber, adding that "the brain is very efficient, and does not allow unused space to waste."
He and his colleagues have already had a hunch that this was the case: "It has been suggested that cross-modal reorganization of the deaf auditory cortex may provide the neural substrate mediating compensatory visual function," they wrote that they tested their hypothesis comparing congenitally deaf cats that hearings cats while they conducted a series of psychophysically challenges.
They found that deaf cats were "generally have a greater localization in the peripheral field and the lower visual motion detection thresholds, as compared to hearing cats.
But when they were reversible operations of the brain in deaf cats that are disabled posterior auditory cortex (the part that usually takes a peripheral sound), they found the cat had lost his excellent performance in peripheral vision, which led them to propose the function remained the same (for the detection of peripheral signals ), but simply shifted from auditory to visual.
They also found that disabling the deaf cat dorsal auditory cortex has made them lose their superior visual motion detection.
So Lomber and colleagues concluded that:
"Our results show that the improved visual performance in deaf due to cross-modal reorganization of the deaf auditory cortex and can locate individual visual functions in discrete parts of the reorganized auditory cortex.
Lomber and his colleagues now want to further investigate how this phenomenon could affect the deaf who receive cochlear implants. What happens to the brains of people who have been deaf all their lives when they suddenly begin to receive audio signals to the process, especially if the areas normally used for hearing are currently being used to enhance the mind?
Lomber drew an analogy with letting others settled in the cottage you're not using for some time. And suddenly you find the need for it back, but they made themselves comfortable, rearrange the furniture and made it to their needs.
"They do not want to leave just because you come back," explained Lomber.
The team also hopes to investigate if these same changes occur in brains of people were deaf at birth, but became deaf later in life. They want to know, for example, if the experience of hearing stops brain reorganization of auditory cortex to increase another sense.
"Cross-modal plasticity in specific auditory cortex is the basis of visual compensation in the deaf." Stephen G Lomber, M Meredith, Alex and Andrew Kral. Nature Neuroscience, Published online: 10 October 2010. DOI: 10.1038/nn.2653