Abstract
Previous research has indicated that inner ear function might be modulated by visual attention, although the results have not been totally conclusive. Conceivably, modulation of hearing might occur due to stimulation of the cochlea via descending medial olivocochlear (MOC) neurons. The aim of the present study was to test whether increased visual attention caused corresponding changes in inner ear function, which was measured by the strength of otoacoustic emissions (OAEs) recorded from the ear canal in response to a steady train of clicks. To manipulate attention, we asked subjects to attend to, or ignore, visual stimuli delivered according to an odd-ball paradigm. The subjects were presented with two types of visual stimuli: standard and deviant (20% of all stimuli, randomly presented). During a passive part of the experiment, subjects had to just observe a pattern of squares on a computer screen. In an active condition, the subject’s task was to silently count the occasional inverted (deviant) pattern on the screen. At all times, visual evoked potentials (VEPs) were used to objectively gauge the subject’s state of attention, and OAEs in response to clicks (transiently evoked OAEs, TEOAEs) were used to gauge inner ear function. As a test of descending neural activity, TEOAE levels were evaluated with and without contralateral acoustic stimulation (CAS) by broadband noise, a paradigm known to activate the MOC pathway. Our results showed that the recorded VEPs were, as expected, a good measure of visual attention, but even when attention levels changed there was no corresponding change in TEOAE levels. We conclude that visual attention does not significantly affect inner ear function.
Highlights
The ear is passive receiver of sounds and acts actively, amplifying acoustic signals before transforming them into electrical impulses and sending them to the cerebral cortex
The present study has shown no significant effect of visual attention on transiently evoked OAEs (TEOAEs), even though we measured, objectively, different patterns of visual evoked potentials (VEPs) arising from each attention no task passive active rejection rate [%]
There has been one study where a more complicated visual task was chosen (Srinivasan et al, 2014), and this study found that visual attention had an effect on distortion product OAEs (DPOAEs); there was no monitoring of the level of attention using evoked potentials
Summary
The ear is passive receiver of sounds and acts actively, amplifying acoustic signals before transforming them into electrical impulses and sending them to the cerebral cortex We know this amplification takes place in the cochlea, but the mechanics is complicated and not fully understood (Bell & Fletcher, 2004). Contralateral acoustic stimulation (CAS) may cause a decrease in cochlear amplifier gain (a decrease in the amplitude of OAEs) via descending medial olivocochlear (MOC) neurons (reviewed by Guinan, 2006) In this way, measurements of OAE strength or strength of their suppression by CAS can become a proxy for the level of activity in neural pathways to the cochlea. Given the link between OAEs and neural activity, the question arises of whether focusing attention on a sound, or directing attention elsewhere—to another modality such as vision—will, via top-down control, modulate hearing
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