Audiovisual speech processing and listening effort in untreated age-related hearing loss: evidence from functional magnetic resonance imaging

摘要

Functional magnetic resonance imaging (fMRI) enables objective measurement of central auditory processing. We used fMRI to investigate neural processing of audiovisual speech in hearing impaired unaided and non-hearing impaired elderly subjects. Speech stimuli were used under four different conditions, visual only, auditory only and two audio-visual conditions, in which subjects could see the speakers face, one with congruent auditory and visual information and a second with incongruent information. While performance in this task did not differ between hearing impaired and non-hearing impaired participants, task-related neural activity differed. Hearing impaired participants showed higher neural activity in medial and lateral prefrontal cortex which correlated with the amount of high-frequency hearing loss. We suggest that the additional recruitment of frontal brain regions may relate to increased effort, which was supported by reports of increased daily listening effort in the hearing impaired group. An additional data analysis on resting state fMRI data in the same group of subjects, showed that this increased listening effort relates to decreased functional connectivity between inferior frontal and auditory cortex. Task and resting state fMRI data therefore provide valuable measures of central auditory processing of speech and increases in listening effort in the hearing impaired.