Neurophysiological aspects of brainstem processing of speech stimuli in audiometric-normal geriatric population

Neural envelope encoding predicts speech perception performance for normal-hearing and hearing-impaired adults

Peripheral hearing impairment cannot fully account for speech perception difficulties that emerge with advancing age. As the fluctuating speech envelope bears crucial information for speech perception, changes in temporal envelope processing are thought to contribute to degraded speech perception. Previous research has demonstrated changes in neural encoding of envelope modulations throughout the adult lifespan, either due to age or due to hearing impairment. To date, however, it remains unclear whether such age- and hearing-related neural changes are associated with impaired speech perception. In the present study, we investigated the potential relationship between perception of speech in different types of masking sounds and neural envelope encoding for a normal-hearing and hearing-impaired adult population including young (20-30 years), middle-aged (50-60 years), and older (70-80 years) people. Our analyses show that enhanced neural envelope encoding in the cortex and in the brainstem, respectively, is related to worse speech perception for normal-hearing and for hearing-impaired adults. This neural-behavioral correlation is found for the three age groups and appears to be independent of the type of masking noise, i.e., background noise or competing speech. These findings provide promising directions for future research aiming to develop advanced rehabilitation strategies for speech perception difficulties that emerge throughout adult life.