Muscles in and around the ear as the source of “physiological noise” during auditory selective attention: A review and novel synthesis

Abstract

The sensitivity of the auditory system is regulated via two major efferent pathways: the medial olivocochlear system that connects to the outer hair cells, and by the middle ear muscles—the tensor tympani and stapedius. The role of the former system in suppressing otoacoustic emissions has been extensively studied, but that of the complementary network has not. In studies of selective attention, decreases in otoacoustic emissions from contralateral stimulation have been ascribed to the medial olivocochlear system, but the acknowledged problem is that the results can be confounded by parallel muscle activity. Here, the potential role of the muscle system is examined through a wide but not exhaustive review of the selective attention literature, and the unifying hypothesis is made that the prominent “physiological noise” detected in such experiments, which is reduced during attention, is the sound produced by the muscles in proximity to the ear—including the middle ear muscles. All muscles produce low‐frequency sound during contraction, but the implications for selective attention experiments—in which muscles near the ear are likely to be active—have not been adequately considered. This review and synthesis suggests that selective attention may reduce physiological noise in the ear canal by reducing the activity of muscles close to the ear. Indeed, such an experiment has already been done, but the significance of its findings have not been widely appreciated. Further sets of experiments are needed in this area.

The Reliability of Contralateral Suppression of Otoacoustic Emissions Is Greater in Women than in Men

“…In the case of MOCR measurements based on CAS, it is always possible for the signal to be contaminated by middle ear muscle responses (MEMRs), e.g., [ 36 ]. We did not use any special procedure to check for MEMRs within our TEOAE measurements, as our equipment did not provide such a facility.…”

Relationships between the expectations based on the regularity of preceding sound sequences and the medial olivocochlear reflex

“…Francis et al (2018) reported that noise levels in the ear canal decrease when performing an auditory attention task [ 28 ]. Bell and Jedrzejczak (2021) also reported that the reduction of auditory peripheral response measured in the ear canal during a selective attention task may be attributed to the reflex contraction of muscles in and near the ear [ 29 ].…”

The Relationship between Contralateral Suppression of Transient Evoked Otoacoustic Emission and Unmasking of Speech Evoked Auditory Brainstem Response

“…The human auditory system consists of afferent and efferent pathways that interact with each other while processing the auditory information. 1 The efferent pathways of the auditory system are believed to aid in selective attention, 2 3 protect the inner ear from auditory fatigability and acoustic trauma, 4 5 6 and improve the coding of signals embedded in noise, 7 8 9 speech perception in noise, 10 11 12 13 and sound localization in noise. 14 The role of efferent auditory pathways on speech perception in noise has received greater attention among researchers, 10 11 12 13 15 16 17 18 19 20 21 22 but their functional role in speech perception is not understood.…”