Abstract
Age-related hearing loss has been related to a compensatory increase in audio-visual integration and neural reorganization including alterations in functional resting state connectivity. How these two changes are linked in elderly listeners is unclear. The current study explored modulatory effects of hearing thresholds and audio-visual integration on resting state functional connectivity. We analysed a large set of resting state data of 65 elderly participants with a widely varying degree of untreated hearing loss. Audio-visual integration, as gauged with the McGurk effect, increased with progressing hearing thresholds. On the neural level, McGurk illusions were negatively related to functional coupling between motor and auditory regions. Similarly, connectivity of the dorsal attention network to sensorimotor and primary motor cortices was reduced with increasing hearing loss. The same effect was obtained for connectivity between the salience network and visual cortex. Our findings suggest that with progressing untreated age-related hearing loss, functional coupling at rest declines, affecting connectivity of brain networks and areas associated with attentional, visual, sensorimotor and motor processes. Especially connectivity reductions between auditory and motor areas were related to stronger audio-visual integration found with increasing hearing loss.
Highlights
Age-related hearing loss has been related to a compensatory increase in audio-visual integration and neural reorganization including alterations in functional resting state connectivity
For age-related hearing loss, differences in network connectivity have been reported for the default mode network (DMN) and the dorsal attention network (DAN)
Twelve subjects exhibited hearing thresholds < 40 dB HL denoting a mild hearing loss, 26 subjects were considered to be moderately impaired (41–60 dB HL), and the remaining eight participants exhibited a severe form of age-related hearing loss with a maximum hearing loss of 69.5 dB HL
Summary
Age-related hearing loss has been related to a compensatory increase in audio-visual integration and neural reorganization including alterations in functional resting state connectivity. Reduced coupling of the DAN to the precuneus and superior parietal lobule as well as the auditory cortices to the inferior frontal gyrus were associated with subjective listening effort In another study[21], connectivity between auditory and visual areas (MT+) was positively related to hearing thresholds during both resting state and audio-visual processing. Audio-visual integration in hard-of-hearing participants has been linked to elevated activity in frontal brain regions and the left postcentral gyrus[28] as well as task-based connectivity alterations of the auditory cortex to middle frontal, occipital and supramarginal g yri[29] Whether these connectivity modulations are persistent at rest and to what extent alterations in cross-modal activity patterns are mirrored in functional resting state connectivity remains unknown. In order to advance hearing aid fitting options, understanding neural adaptations of already mild stages of age-related hearing loss is of crucial relevance
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