The effects of aging on neural signatures of temporal regularity processing in sounds

Abstract

Sensitivity to temporal regularity (e.g., amplitude modulation) is crucial for speech perception. Degradation of the auditory periphery due to aging and hearing loss may lead to an increased response gain in auditory cortex, with potential consequences for the processing of temporal regularities. We used electroencephalography recorded from younger (18-33 years) and older (55-80 years) adults to investigate how aging affects neural gain and the neural sensitivity to amplitude modulation in sounds. Aging was associated with reduced adaptation in auditory cortex, suggesting an age-related gain increase. Consistently, neural synchronization in auditory cortex to a 4-Hz amplitude modulation of a narrow-band noise was enhanced in ~30% of older individuals. Despite enhanced responsivity in auditory cortex, sustained neural activity (likely involving auditory and higher-order brain regions) in response to amplitude modulation was absent in older people. Hence, aging may lead to an over-responsivity to amplitude modulation in auditory cortex, but to a diminished regularity representation in higher-order areas.