Medical Research: Dual Adaptation In Deaf Brains

The brains of people who cannot hear adapt to process vision-based language, in addition to brain changes associated with the loss of auditory input.

The brains of Deaf people reorganize not only to compensate for the loss of hearing, but also to process language from visual stimuli sign language, according to a study published today (February 12) in Nature Communications. Despite this reorganization for interpreting visual language, however, language processing is still completed in the same brain region.



“The new paper really dissected the difference between hand movements being a visual stimulus, and cognitive components of language,” said Alex Meredith, a neurobiologist at Virginia Commonwealth University, who was not involved in the study.



The brain devotes different areas to interpreting various sensory stimuli, such as visual or auditory. When one sense is lost, the brain compensates by adapting to other stimuli, explained study author Velia Cardin of University College London and Linköping University in Sweden. In Deaf people, for example, “the part of the brain that before was doing audition adapts to be doing something else, which is vision and somatosensation,” she said. However, Deaf humans “don’t just have sensory deprivation,” she added they also have to learn to process a visual, rather than oral, language.



To untangle brain changes due to loss of auditory input from adaptations prompted by vision-based language, the researchers used functional MRI to look at brain activation in three groups of people: Deaf people who communicate through sign language, Deaf people who read lips but don’t understand sign language, and hearing people with no sign language experience.



The researchers showed the three groups videos of sign language and videos that held no linguistic content. The signing videos were designed to allow Cardin’s team to pinpoint which areas had reorganized to process vision-based language, as these areas would only activate in Deaf signers. In contrast, the language-free videos would allow the researchers to identify areas in Deaf brains that had adapted to the loss of auditory input, as these brain areas would activate in both Deaf groups, but not in the brains of hearing volunteers... Read The Full Story.