Cross-modal reorganization of the cortex, a phenomenon in which the brain reorganizes itself, has been shown in profoundly deaf individuals. A recent study, conducted by Garrett Cardon and Anu Sharma of the University of Colorado, investigated cross-modal reorganization between the auditory and somatosensory modalities in older adults with normal hearing and mild-moderate age-related hearing loss in response to vibrotactile stimulation using high density electroencephalography (EEG).
According to the researchers, activation of the somatosensory cortices occurred in adults with normal hearing as well as those with hearing loss. However, adults with mild-moderate age-related hearing loss also showed robust activation of auditory cortical regions in response to somatosensory stimulation. In addition, the degree of cortical plasticity may be related to performance on speech perception in noise outcomes, as the normal hearing group tended to score lower suggestive of better speech perception in noise, while the group with mild-moderate hearing loss tended to have higher (worse) scores.
Results of speech perception in noise testing (Quick SIN) and electrophysiologic testing indicated that those listeners who exhibited more difficulty in speech perception showed more evidence of cortical plasticity.
The study, published online in early May by the journal Frontiers in Human Neuroscience, involved 19 adults between the ages of 49 and 77 years, separated into two groups. One with normal hearing and the other with mild-moderate hearing loss related to aging.
Cortical Plasticity and Hearing Loss
Their study presents the first evidence of somatosensory cross-modal reorganization of the auditory cortex in adults with early-stage, mild-moderate age-related hearing loss.
Importantly, their findings suggest that even mild levels of age-related hearing loss is associated with communication difficulty result in fundamental cortical changes, and that such reorganization is associated with decreased speech perception in noise performance.
Recall that in 2016 Sharma and colleagues published a study suggesting interventional strategies, such as hearing aids may have the potential to reverse functional consequences of cortical plastic changes. This new study provides evidence that even mild hearing loss has an impact on cortical reorganization and functioning of the auditory cortex.
The entire study can be found here.