Abstract
The auditory efferent system, especially the medial olivocochlear reflex (MOCR), is implicated in both typical auditory processing and in auditory disorders in animal models. Despite the significant strides in both basic and translational research on the MOCR, its clinical applicability remains under-utilized in humans due to the lack of a recommended clinical method. Conventional tests employ broadband noise in one ear while monitoring change in otoacoustic emissions (OAEs) in the other ear to index efferent activity. These methods, (1) can only assay the contralateral MOCR pathway and (2) are unable to extract the kinetics of the reflexes. We have developed a method that re-purposes the same OAE-evoking click-train to also concurrently elicit bilateral MOCR activity. Data from click-train presentations at 80 dB peSPL at 62.5 Hz in 13 young normal-hearing adults demonstrate the feasibility of our method. Mean MOCR magnitude (1.7 dB) and activation time-constant (0.2 s) are consistent with prior MOCR reports. The data also suggest several advantages of this method including, (1) the ability to monitor MEMR, (2) obtain both magnitude and kinetics (time constants) of the MOCR, (3) visual and statistical confirmation of MOCR activation.
Highlights
The auditory efferent system serves as a dynamic feedback mechanism through which the brain regulates afferent neural inputs
We have introduced a time-course-based method of the medial olivocochlear reflex (MOCR) magnitude and kinetics estimated solely using clicks without any additional elicitors
The following highlights from our findings suggest that our proposed method can be successful in clinical translation. (1) 100% of the participants had MOCR activation in at least one frequency among seven 1/3rd bands (>90% across all seven frequencies)
Summary
The auditory efferent system serves as a dynamic feedback mechanism through which the brain regulates afferent neural inputs. Such feedback control occurs at multiple stages in the auditory system and is thought to aid in automatic and attention-driven signal detection in noise (Winslow and Sachs, 1988; de Boer and Thornton, 2007; Delano et al, 2007; Mertes et al, 2019) and protection of peripheral sensory cells from acoustic overexposure (Galambos and Rupert, 1959; Borg et al, 1983; Liberman, 1990; Walsh et al, 1998; Rajan, 2000; Lauer and May, 2011; Liberman et al, 2014; Boero et al, 2018). To fill this longstanding gap, here we describe a time-course and click-evoked otoacoustic emission (CEOAE)-based method that has the potential to serve as a simple and efficient test of efferent modulation of cochlear function
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