March 25, 2009 --
Virginia Commonwealth University School of Medicine researchers have
discovered that adult animals with hearing loss actually re-route the
sense of touch into the hearing parts of the brain.
In
the study, published online in the Early Edition of the Proceedings of
the National Academy of Sciences the week of March 23, the team
reported a phenomenon known as cross-modal plasticity in the auditory
system of adult animals. Cross-modal plasticity refers to the
replacement of a damaged sensory system by one of the remaining ones.
In this case, the sense of hearing is replaced with touch.
About 15 percent of American adults suffer from some form of hearing
impairment, which can significantly impact quality of life, especially
in the elderly.
"One often learns, anecdotally, that 'grandpa'
simply turned off his hearing aid because it was confusing and no
longer helped. Our study indicates that hearing deficits in adult
animals result in a conversion of their brain's sound processing
centers to respond to another sensory modality, making the
interpretation of residual hearing even more difficult," said principal
investigator Alex Meredith, Ph.D., a professor in the VCU Department of
Anatomy and Neurobiology.
"Whether this becomes a positive
feedback cycle of increasing hearing difficulty is currently under
investigation, but these findings raise the possibility that even mild
hearing loss in adult humans can have serious and perhaps progressive
consequences," Meredith said.
The findings provide researchers
and clinicians with insight into how the adult brain retains the
ability to re-wire itself on a large scale, as well as the factors that
may complicate treatment of hearing loss with hearing aids or cochlear
implants.
The study was supported by a grant from the National Institutes of Health.
Meredith
worked with postdoctoral fellows Brian L. Allman and Leslie P.
Keniston, both in the Department of Anatomy and Neurobiology.
Source : Virginia Commonwealth University
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