Neural Mechanisms of Listening to Speech in Noise With Age-Related Hearing Loss

Age-related hearing loss is prevalent in a large proportion of older adults and is the largest modifiable risk factor of dementia. Previous studies have shown that hearing loss in older adults is associated with reductions in brain volume and alterations in brain connectivity, but there is a gap in our understanding of how hearing loss may impact brain activity, specifically while listening to speech. In this study, we hypothesized that hearing loss would be associated with (1) reduced activation within temporal auditory regions in response to speech presented with and without background noise, and (2) increased activation in the cingulo-opercular network in response to speech in noise.

Twenty-seven older adults (mean age = 68 yr, 17 women) recruited from the community completed a clustered sparse-sampling functional magnetic resonance imaging protocol while listening to speech presented with and without multi-talker background noise. Regions of interest-based and exploratory voxel-wise analyses were used to investigate correlations between functional magnetic resonance imaging activation to speech and hearing ability. Hearing was defined as the pure-tone average of hearing thresholds at 0.5, 1, 2, and 4 kHz from the better ear and ranged from normal to a moderate hearing loss.

Our results indicate that age-related hearing loss was associated with reduced activation in right Heschl's gyrus and left middle temporal gyrus in response to speech. Exploratory voxel-wise analyses suggest that hearing loss may be associated with alterations in activation in other sensory cortical regions and portions of the frontal cortex, including left pars opercularis. Activation within the cingulo-opercular network was not associated with hearing loss.

These findings suggest that age-related hearing loss in humans is associated with altered brain activity in response to speech, particularly within right Heschl's gyrus. It further provides hypothesis-generating data for future studies on the effects of hearing loss on brain function.