Abstract
This electrophysiological study investigated the role of the medial olivocochlear (MOC) efferents in listening in noise. Both ears of eleven normal-hearing adult participants were tested. The physiological tests consisted of transient-evoked otoacoustic emission (TEOAE) inhibition and the measurement of cortical event-related potentials (ERPs). The mismatch negativity (MMN) and P300 responses were obtained in passive and active listening tasks, respectively. Behavioral responses for the word recognition in noise test were also analyzed. Consistent with previous findings, the TEOAE data showed significant inhibition in the presence of contralateral acoustic stimulation. However, performance in the word recognition in noise test was comparable for the two conditions (i.e., without contralateral stimulation and with contralateral stimulation). Peak latencies and peak amplitudes of MMN and P300 did not show changes with contralateral stimulation. Behavioral performance was also maintained in the P300 task. Together, the results show that the peripheral auditory efferent effects captured via otoacoustic emission (OAE) inhibition might not necessarily be reflected in measures of central cortical processing and behavioral performance. As the MOC effects may not play a role in all listening situations in adults, the functional significance of the cochlear effects of the medial olivocochlear efferents and the optimal conditions conducive to corresponding effects in behavioral and cortical responses remain to be elucidated.
Highlights
Human auditory perception depends on elaborate neural coding of acoustic properties of the target sounds and involves bidirectional interactions of the afferent and efferent systems along the auditory pathway
The neural coding of auditory stimulation begins in the afferent system of the cochlear inner hair cells on the basilar membrane, which is regulated by the active mechanical behavior of outer hair cells under the control of a complex efferent innervation system originating from the medial olivary complex in the brainstem
Click-evoked otoacoustic emission (OAE) were present at acceptable signal-to-noise ratio (SNR) in both ears for all the conditions, and the probe close to 100%
Summary
Human auditory perception depends on elaborate neural coding of acoustic properties of the target sounds and involves bidirectional interactions of the afferent and efferent systems along the auditory pathway. The neural coding of auditory stimulation begins in the afferent system of the cochlear inner hair cells on the basilar membrane, which is regulated by the active mechanical behavior of outer hair cells under the control of a complex efferent innervation system originating from the medial olivary complex in the brainstem. A major function of the MOC efferents is thought to be the enhancement of transient signals in noise. Brain Sci. 2020, 10, 428 how the activation of the MOC system by ipsilateral and/or contralateral stimulation contributes to the enhanced central processing of the auditory target either autonomously or via interactions with attentional control.
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