Electromyographic responses of the auriculomotor system during effortful listening in hearing aid users.

BACKGROUND: Auricular muscles in humans may still display increased activity associated with auditory attention and effortful listening in complex patterns. As research into this auriculomotor system has primarily been conducted in normal-hearing participants, this study investigated electromyographic (EMG) signals of auricular muscles in hearing aid users under challenging listening conditions in order to evaluate their potential future use as a measure of perceived listening effort. METHODS: Twenty-four experienced, bilateral hearing aid users (mean age approximately 64 years) were instructed to attend a target podcast, which was either presented in quiet (SIQ), or in front of a spatially distributed, noisy background. If noise was present, a specialized noise reduction feature of the hearing aids was either turned off (NR-off) or on (NR-on), which resulted in three task difficulties, or conditions: SIQ, NR-on, and NR-off. EMGs of two auricular muscles, the superior and posterior auricular muscles (SAM, PAM), as well as the corrugator supercilii (part of the facial muscles) were recorded. RESULTS: Perceived listening effort significantly increased from SIQ to NR-on to NR-off, indicating that these three conditions presented distinct task difficulties. PAM activity resembled the perceived listening effort (highest activity during NR-off, intermediate during NR-on, lowest during SIQ), but statistical significance was only observed between NR-off and SIQ (p = 0.013). Activity of the corrugator significantly increased over time in the presence of noise, regardless of the noise reduction algorithm, but remained low during SIQ. While we did not observe a significant effect of task difficulty on the SAM, we unexpectedly found a strong time-dependent decrease in SAM activity, which likely poses as a serious confounding factor. CONCLUSIONS: This preliminary study shows that, in a group of hearing aid users, the activity of auricular muscles increased in highly demanding listening tasks, but due to an unexpected time drift, replication of the study with a modified protocol and a larger participant group is necessary.