Bottom-up driven involuntary attention modulates auditory signal in noise processing

Lothar Lagemann,Hidehiko Okamoto,Christo Pantev,Henning Teismann

doi:10.1186/1471-2202-11-156

Lothar Lagemann, Hidehiko Okamoto + Show 2 more

Open Access

https://doi.org/10.1186/1471-2202-11-156

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Abstract

BackgroundAuditory evoked responses can be modulated by both the sequencing and the signal-to-noise ratio of auditory stimuli. Constant sequencing as well as intense masking sounds basically lead to N1m response amplitude reduction. However, the interaction between these two factors has not been investigated so far. Here, we presented subjects tone stimuli of different frequencies, which were either concatenated in blocks of constant frequency or in blocks of randomly changing frequencies. The tones were presented either in silence or together with broad-band noises of varying levels.ResultsIn silence, tones presented with random sequencing elicited a larger N1m response than tones presented with constant sequencing. With increasing noise level, this difference decreased and even vanished in the condition where noise intensity exceeded the tone intensity by 10 dB. Furthermore, under noisy conditions, the N1m latency was shorter in the constant sequencing condition compared to the random sequencing condition.ConclusionsBesides the well-known neural habituation mechanisms, bottom-up driven attention plays an important role during auditory processing in noisy environments. This bottom-up driven attention would allow us to track a certain auditory signal in noisy situations without voluntarily paying attention to the auditory modality.

Highlights

Auditory evoked responses can be modulated by both the sequencing and the signal-to-noise ratio of auditory stimuli
The difference between random and constant sequencing decreased, and vanished completely in the condition when the noise intensity exceeded the stimulus intensity by 10 dB (Figure 4)
The largest difference between constant and random sequencing was found in the +10 dB noise condition (Figure 5)

Summary

Introduction

Auditory evoked responses can be modulated by both the sequencing and the signal-to-noise ratio of auditory stimuli. This ability might have helped noticing and spotting predators sneaking up in the midst of wind rustling in the trees or against a background of heavy rain It plays an important role in today’s everyday life (e.g., to be warned of an approaching vehicle in a diffuse traffic noise setting). The segregational and integrational mechanisms at work during this auditory scene analysis [1] are based upon the physical features of the sounds (such as spectrum, intensity, phase, etc.) coming from distinct or identical sources Besides these features neural activity in the auditory cortex is affected by the sequencing of sounds in time.

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