Selective attention reduces physiological noise in the external ear canals of humans. II: Visual attention

Abstract

Human subjects performed in several behavioral conditions requiring, or not requiring, selective attention to visual stimuli. Specifically, the attentional task was to recognize strings of digits that had been presented visually. A nonlinear version of the stimulus-frequency otoacoustic emission (SFOAE), called the nSFOAE, was collected during the visual presentation of the digits. The segment of the physiological response discussed here occurred during brief silent periods immediately following the SFOAE-evoking stimuli. For all subjects tested, the physiologicalnoise magnitudes were substantially weaker (less noisy) during the tasks requiring the most visual attention. Effect sizes for the differences were >2.0. Our interpretation is that cortico-olivo influences adjusted the magnitude of efferent activation during the SFOAE-evoking stimulation depending upon the attention task in effect, and then that magnitude of efferent activation persisted throughout the silent period where it also modulated the physiological noise present. Because the results were highly similar to those obtained when the behavioral conditions involved auditory attention, similar mechanisms appear to operate both across modalities and within modalities. Supplementary measurements revealed that the efferent activation was spectrally global, as it was for auditory attention.

Selective attention reduces physiological noise in the external ear canals of humans. I: Auditory attention

“…The results were similar to those in Table 1; the means calculated either across ears or triplets differed by less than 1 dB. (No systematic differences between the ipsilateral and contralateral measures, nor the two triplets were seen in the visual-attention data either; Walsh et al, 2014). Accordingly, we conclude that the ipsilateral and contralateral measures from the silent period are essentially equivalent, as are the triplet 1 and triplet 2 measures.…”

“…In this first report, a nonlinear version of the stimulus-frequency OAE (SFOAE), called the nSFOAE or the residual from linear prediction (Walsh et al, 2010a, 2010b), was used to measure cochlear responses during tasks that required either selective auditory attention to strings of digits spoken by one of two simultaneous talkers (dichotic or diotic listening), or relative inattention. In a companion paper, we report similar results involving visual rather than auditory attention (Walsh et al, 2014). These first two reports emphasize cochlear measures made during brief silent periods following the nSFOAE-evoking stimuli.…”

“…As shown, physiological responses still could be measured after the offset of the tone-plus-noise, and those responses still showed a difference for these two attentional conditions. The responses during the silent period were invariably smaller in the selective-attention conditions than in the inattention conditions, and this was true for every subject and for both the auditory- and visual-attention tasks (see Walsh et al, 2014). Before showing the comparisons between the attention and inattention conditions in detail for the silent period, we describe several equivalences in the data: between ipsilateral and contralateral measurements, between the two triplets, and between dichotic- and diotic-listening conditions.…”

“…Consecutive nSFOAE stimuli always were separated by a 500-ms ISI (during which digits were spoken by the two talkers). As noted, the nSFOAE responses obtained during the presentations of the tone and noise (the perstimulatory responses) will be described elsewhere; here and in the companion paper on visual attention (Walsh et al, 2014), the emphasis will be on the nSFOAEs measured during brief silent periods that followed each nSFOAE-evoking stimulus. Specifically, following the simultaneous offset of tone and noise for each presentation was a 30-ms silent period from which a measure of the physiological noise in the ear canal was extracted for each triplet.…”

“…These corrections ranged from 21.5 dB at 1.1 kHz to 1.5 dB at 7 kHz (2.46 dB at 4.0 kHz). All noise levels reported in this and the companion paper (Walsh et al, 2014) have been adjusted by these frequency-dependent correction factors; the values in Walsh et al (2010a, 2010b) were not so corrected. Note that these adjustments had no effects on whatever differences existed between the physiological responses obtained from different attention conditions.…”