Speech-in-Noise Auditory Training and The Medial Olivocochlear Efferent System

Abstract

The medial olivocochlear system is an important system that mediates efferent control over the outer hair cells of the cochlea (Boothalingam, Allan, Allen, & Purcell, 2019). It has been shown to play a role in varying aspects of hearing, such as signal-in-noise perception (Lilaonitkul & Guinan, 2009; Robertson, 2009; D. W. Smith & Keil, 2015). Importantly, the connection between speech-in-noise auditory training and the changes seen in speech-in-noise perception and how these relate to the medial olivocochlear system are fundamentally important (Bhattacharya, 2020; de Boer & Thornton, 2008). This study aimed to build on a previous study by further evaluating the relationship between an auditory training programme and its effects on speech-in-noise perception and medial olivocochlear system activity (Bhattacharya, 2020). Additionally, this study aimed to evaluate the relationship between the changes in speech-in-noise perception following the auditory training programme and changes in medial olivocochlear activity to identify the mechanisms underlying these changes. Speech-in-noise perception was measured using Word Recognition-in-Noise and Quick Speech-in- Noise Tests, whereas medial olivocochlear system activity was measured through Distortion Product Otoacoustic Emissions and Auditory Brainstem Responses. The findings of this study showed an improvement in speech-in-noise perception ability for participants who underwent the auditory training programme. Furthermore, there was a suppression identified in DPOAE and ABR wave I response amplitudes when measured with the presence of a medial olivocochlear reflex elicitor. However, the findings of this study did not reflect any significant changes in medial olivocochlear system activity following the training programme or any significant relationship between the changes in speech-in-noise perception and medial olivocochlear system activity. This led to the conclusion that the improvements seen in speech-in-noise perception with auditory training could have been mediated by alternative mechanisms, or there could be an involvement of the medial olivocochlear system that was undetected. Importantly, this study identifies that perceptual improvements seen with auditory training and medial olivocochlear activity are a result of complex interconnections between multiple structures, and therefore, require further research to develop certainty regarding these mechanisms. These findings are generally consistent with the previous study on this topic (Bhattacharya, 2020).