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).