Prefrontal Speaker-Listener Neural Coupling Supports Speech-in-Noise Comprehension in Normal-Hearing Older Adults: An fNIRS Study

Despite age-related declines in the structure and function of auditory and language-related regions, many older adults retain a relatively preserved ability to understand speech in noisy environments. However, the neural mechanisms supporting this ability remain unclear. In this study, 30 older adults (59-71 years) with normal hearing listened to narratives spoken by a separate group of speakers at varying noise levels, with their neural activity recorded using functional near-infrared spectroscopy (fNIRS). Speaker-listener neural coupling analysis revealed that older listeners' neural activity across broad brain regions, including classical language regions and the prefrontal cortex, was coupled with the speaker's speech-production-related neural activity. Compared to younger listeners, older adults exhibited stronger prefrontal neural coupling, which was stably integrated with language-region coupling across noise levels. Crucially, as noise levels increased, prefrontal neural coupling became more strongly correlated with comprehension performance. These findings elucidate the neural mechanisms supporting natural speech-in-noise processing in the aging brain, highlighting the compensatory involvement of the prefrontal cortex in facilitating speech-in-noise comprehension in older adults and indicating it as a potential target for neuromodulatory and cognitive interventions to promote successful aging.