Auditory Attention Causes Gain Enhancement and Frequency Sharpening at Successive Stages of Cortical Processing—Evidence from Human Electroencephalography

Abstract

Previous findings have suggested that auditory attention causes not only enhancement in neural processing gain, but also sharpening in neural frequency tuning in human auditory cortex. The current study was aimed to reexamine these findings. Specifically, we aimed to investigate whether attentional gain enhancement and frequency sharpening emerge at the same or different processing levels and whether they represent independent or cooperative effects. For that, we examined the pattern of attentional modulation effects on early, sensory-driven cortical auditory-evoked potentials occurring at different latencies. Attention was manipulated using a dichotic listening task and was thus not selectively directed to specific frequency values. Possible attention-related changes in frequency tuning selectivity were measured with an adaptation paradigm. Our results show marked disparities in attention effects between the earlier N1 deflection and the subsequent P2 deflection, with the N1 showing a strong gain enhancement effect, but no sharpening, and the P2 showing clear evidence of sharpening, but no independent gain effect. They suggest that gain enhancement and frequency sharpening represent successive stages of a cooperative attentional modulation mechanism that increases the representational bandwidth of attended versus unattended sounds.

Neural Responses and Perceptual Sensitivity to Sound Depend on Sound-Level Statistics

“…Single-trial responses within each category were averaged (Fig. 3A) and the P1-N1 and P2-N1 peak-to-peak amplitudes were calculated separately for each participant [34][35][36][37][38] . A linear function was fit to amplitude data (separately for P1-N1 and P2-N1) as a function of the five sound levels, independently for each participant.…”

“…P1-N1 and P2-N1 peak-to-peak amplitude. Data analysis focused on the P1-N1 and P2-N1 peak-to-peak amplitudes, as in previous work [34][35][36][37][38] . Estimation of P1, N1, and P2 peak amplitudes for each participant can be challenging when responses are strongly adapted as in the current experiment.…”

Interpretable Representation Learning for Speech and Audio Signals Based on Relevance Weighting

“…Both physiological and behavioral studies have suggested that stimulusdriven neural activity in the sensory pathways can be modulated in amplitude with attention [18]. The recordings of event-related brain potentials indicate that such sensory gain control or amplification processes play an important role in tasks that involve attention [19]. The combined event-related brain potential and neuroimaging experiments provide strong evidence that attentional gain control operates at an early stage of sensory processing [20].…”

Neural Responses and Perceptual Sensitivity to Sound Depend on Sound-Level Statistics

“…Sensitivity of neural responses to sound level was assessed by binning the responses to each sound (across both contexts) into five sound-level categories (10-dB width, centered on 10, 20, 30, 40, and 50 dB SL 21 ). Single-trial responses within each category were averaged (Figure 3, left) and the P1-N1 peak-to-peak amplitude was calculated separately for each participant [25][26][27] . A linear function was fit to P1-N1 amplitude data as a function of the five sound levels independently for each participant.…”

“…P1-N1 peak-to-peak amplitude. Data analysis focused on the P1-N1 peak-to-peak amplitude, as in previous work [25][26][27] . Response latencies can only be estimated accurately for responses with a sufficiently large amplitude.…”