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Comprehending speech in noisy situations is difficult and suffers with aging, hearing loss, and cognitive decline. Using visual speech cues improves perception and comprehension of speech in noise (SiN) in older adults with hearing impairment. In the current study we investigated neurofunctional correlates (i.e., neural tracking of speech) of the visual enhancement effect in a naturalistic setting in which older adults with hearing impairment (N=67) listened to sentences in babble noise in audio-only and audiovisual conditions and performed an intelligibility and a comprehension task, while EEG was recorded. Behaviorally, we found that visual speech cues improved intelligibility and comprehension of speech presented in babble noise and that particularly individuals with high working memory capacity benefitted. Furthermore, we found that the visual enhancement effect was accompanied by increased cortical tracking of the speech envelope particularly in individuals who were low performers in the audio-only condition (i.e., < 70% correct) leading to improved speech in noise comprehension in an audiovisual setting. Further, these low auditory-only performers showed deficient neural speech tracking in a right auditory topographical cluster, which improved significantly when visual speech cues were presented leading to more bilateral processing of speech. Overall, our results show that older adults with hearing impairment who have difficulties with speech in noise perception use visual speech cues to improve performance which is reflected in more bilateral processing of speech.
Frei et al. (Wed,) studied this question.