Brain dynamics that correlate with effects of learning on auditory distance perception.

Matthew G Wisniewski,Klaus Gramann,Scott Makeig,Eduardo Mercado,Barbara A Church

doi:10.3389/fnins.2014.00396

Abstract

Accuracy in auditory distance perception can improve with practice and varies for sounds differing in familiarity. Here, listeners were trained to judge the distances of English, Bengali, and backwards speech sources pre-recorded at near (2-m) and far (30-m) distances. Listeners' accuracy was tested before and after training. Improvements from pre-test to post-test were greater for forward speech, demonstrating a learning advantage for forward speech sounds. Independent component (IC) processes identified in electroencephalographic (EEG) data collected during pre- and post-testing revealed three clusters of ICs across subjects with stimulus-locked spectral perturbations related to learning and accuracy. One cluster exhibited a transient stimulus-locked increase in 4–8 Hz power (theta event-related synchronization; ERS) that was smaller after training and largest for backwards speech. For a left temporal cluster, 8–12 Hz decreases in power (alpha event-related desynchronization; ERD) were greatest for English speech and less prominent after training. In contrast, a cluster of IC processes centered at or near anterior portions of the medial frontal cortex showed learning-related enhancement of sustained increases in 10–16 Hz power (upper-alpha/low-beta ERS). The degree of this enhancement was positively correlated with the degree of behavioral improvements. Results suggest that neural dynamics in non-auditory cortical areas support distance judgments. Further, frontal cortical networks associated with attentional and/or working memory processes appear to play a role in perceptual learning for source distance.

Highlights

Most of what is currently known about human auditory distance perception comes from research focused on variations in acoustic cues produced by propagation, and on how degrading or altering such cues affects distance judgments
Independent component (IC) processes identified in electroencephalographic (EEG) data collected during pre- and post-testing revealed three clusters of ICs across subjects with stimulus-locked spectral perturbations related to learning and accuracy
In two studies we have found task-related EEG oscillatory dynamics attributed to sources at or near both auditory and nonauditory brain regions

Summary

Introduction

Most of what is currently known about human auditory distance perception comes from research focused on variations in acoustic cues produced by propagation, and on how degrading or altering such cues affects distance judgments. Because the known acoustic cues to distance are well matched between stimuli played forward and time-reversed (McGregor et al, 1985; Brungart and Scott, 2001), better performance for forward speech suggests that central cognitive processes play a significant role in distance perception. Important to note is that in all the above studies acoustic distance cues were identical or quite similar across conditions, demonstrating that auditory distance perception cannot be fully understood by focusing solely on the impact of cue alteration and degradation on distance judgments

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