Neural entrainment of the Speech Envelope in Aging Normal Hearing and Hearing Impaired Listeners

Background Given that the speech envelope is a primary cue for speech understanding, a measure of neural entrainment of the envelope, obtained from the EEG, can offer complementary information to behavioural speech audiometry. Indeed, Vanthornhout et al. (2017) found an increase in entrainment with increasing signal-to-noise ratio (SNR) in young normal hearing subjects. We investigated the effect of age and hearing loss on this method. Methods We recorded the EEG in 10 older (45-85 years) and 5 young normal hearing subjects (18-35 years). In addition to the normal hearing listeners, we also collected data of 3 older hearing impaired participants. In order to measure neural entrainment to the speech envelope in function of SNR, we trained a linear decoder to reconstruct the speech envelope from the EEG. Consequently, by correlating the reconstructed with the original envelope, entrainment was estimated. We presented two target stimuli spoken by female talkers: the Flemish Matrix sentences, to compare with behavioural speech audiometry, and audiobooks to resemble daily life speech. We used two maskers: speech weighted noise and a competing male talker, with the same long-term-average spectrum as the stimulus. Behavioural speech audiometry was administered during EEG recording. Results For all conditions, we found increased envelope entrainment with increasing SNR. Similar to Presacco et al. (2016), neural entrainment to the speech envelope was higher in older normal hearing subjects compared to younger. As the behavioural speech understanding scores did not differ between age groups, these results indicate that older adults may need more cortical activation to perform in the same way. The results of the hearing impaired listeners will be presented. Conclusions There is a strong individual effect on neural envelope entrainment, depending on age. Therefore, the increase in entrainment with speech understanding only holds on an individual basis. Although ageing appears to induce the opposite effect, the results indicate that higher entrainment in older listeners can reflect an overactivation of the brain when trying to perform the same as the younger participants.status: publishe