Auditory attention reduced ear-canal noise in humans, but not through medial olivocochlear efferent inhibition: Implications for measuring otoacoustic emissions during behavioral task performance

Abstract

22Otoacoustic emissions (OAEs) are often measured to non-invasively determine activation of medial 23 olivocochlear (MOC) efferents in humans. Usually these experiments assume that ear-canal noise 24 remains constant. However, changes in ear-canal noise have been reported in some behavioral 25 experiments. We studied the variability of ear-canal noise in eight subjects who performed a two-26interval-forced-choice (2IFC) sound-level-discrimination task on monaural tone pips in masking 27 noise. Ear-canal noise was recorded directly from the unstimulated ear opposite the task ear. 28Recordings were also done with similar sounds presented, but no task done. In task trials, ear-canal 29 noise was reduced at the time the subject did the discrimination, relative to the noise level earlier in 30 the trial. In two subjects, there was a decrease in ear-canal noise, primarily at 1-2 kHz, with a time 31 course similar to that expected from inhibition by MOC activity elicited by the task-ear masker noise. 32These were the only subjects with spontaneous OAEs (SOAEs). We hypothesize that the SOAEs 33were inhibited by MOC activity elicited by the task-ear masker. Based on the standard rationale in 34 OAE experiments that large bursts of noise are artifacts due to subject movement, noise bursts above 35 a sound-level criterion were removed. As the criterion was lowered and more high-and moderate-36 level noise bursts were removed, the reduction in noise level from the beginning of the trial to the 37 time of the 2IFC discrimination became less. This pattern is opposite that expected from MOC 38 inhibition (which is greater on lower-level sounds), but can be explained by the hypothesis that 39 subjects move less and create fewer bursts of noise when they concentrate on doing the task. In 40 contrast, for the six subjects with no SOAEs, in no-task trials the noise level was little changed 41 throughout the trial. Our results show that measurements of MOC effects on OAEs must measure and 42 account for changes in ear-canal noise, especially in behavioral experiments. The results also provide 43 a novel way of showing the time course of the buildup of attention in ear-canal noise during a 2IFC 44 task. 45 46

Cochlear activity in silent cue-target intervals shows a theta-rhythmic pattern and is correlated to attentional alpha and theta modulations

“…An increasing number of studies support this notion by measuring otoacoustic emissions (OAE; [11][12][13]) or cochlear microphonics [14]. However, the described effects are restricted to sound-evoked responses, are small, and sometimes contradictory [15,16]. Furthermore, the attention research on cortical and cochlear processes has been conducted largely independently (see [13,17,18] for exceptions).…”

Cochlear activity in silent cue-target intervals shows a theta-rhythmic pattern and is correlated to attentional alpha modulations

“…An increasing number of studies support this notion by measuring otoacoustic emissions (OAE; Smith, Aouad, & Keil, 2012;Walsh, Pasanen, & McFadden, 2015;Wittekindt, Kaiser, & Abel, 2014) or cochlear microphonics (Delano et al, 2007). However, the described effects are restricted to soundevoked responses, are small, and sometimes contradictory (Francis et al, 2018;Meric & Collet, 1992). Furthermore, the attention research on cortical and cochlear processes has been conducted largely independently (see Wittekindt et al (2014), Dragicevic et al (2019), or Riecke et al (2020) for exceptions).…”