Hearing Loss May Lead to Permanent Changes in the Brain
By Steve McGaughey
Hearing loss affects an estimated 50 million people in the United States.
Now researchers have found that hearing loss may be affecting the long-term
brain structure of those who suffer from it.
Beckman Institute faculty member Fatima Husain led the research, which
employed two different imaging modalities in studies of people with hearing
loss, normal hearing, and those with hearing loss and tinnitus (ringing in
the ears). They found that those in the hearing loss group showed structural
changes in their brains.
"This suggests that functional changes due to sensory deprivation may
result in long-term structural changes," Husain said. "However, in the case
of tinnitus, surprisingly, there were few changes to brain structure despite
changes to function, suggesting that when sensory deprivation is accompanied
by self-generated noise, it may be better at preserving neural tissue."
Husain and her collaborators on the study measured neuroanatomical
changes in gray and white matter in the brains of participants with only
bilateral hearing loss (HL), participants who had hearing HL and tinnitus
(TIN), and a control group with normal hearing (NH) without tinnitus. Their
study, reported on in a paper titled Neuroanatomical changes due to hearing
loss and chronic tinnitus: A combined VBM and DTI, looked at neuroanatomical
alterations associated with hearing loss and tinnitus.
The researchers used structural magnetic resonance imaging (MRI) scans
and voxel-based morphometry (VBM) to examine changes in gray matter, and
diffusion tensor imaging (DTI), to identify changes in white matter tract
orientation. The researchers noted that while tinnitus is often accompanied
by hearing loss, not everyone with hearing loss experiences tinnitus. Their
goal in the study was to investigate structural gray and white matter
changes related to tinnitus and hearing loss and try to dissociate them from
changes due only to hearing loss.
"We observed that the HL group had the most profound changes in both
white and gray matter relative to the other groups," Husain said. "The gray
matter decreases seen in the HL group relative to the NH group were in the
anterior cingulate, putamen and middle frontal gyrus.
Husain added that two of these regions, the anterior cingulate and
frontal cortex, were "also implicated in our companion study that studied
functional response of the brain in the same group of subjects and points to
involvement of the attention processing network."
The researchers concluded that by dissociating the effect of tinnitus
from hearing loss, they observed that "hearing loss rather than tinnitus had
the greatest influence on gray and white matter alterations."
Husain, who directs the Auditory Cognitive Neuroscience Lab in the
Department of Speech and Hearing Science, is a member of Beckman's Human
Perception and Performance group.
Source: University of Illinois