Abstract
Auditory selective attention is an important mechanism for top-down selection of the vast amount of auditory information our perceptual system is exposed to. In the present study, the impact of attention on auditory steady-state responses is investigated. This issue is still a matter of debate and recent findings point to a complex pattern of attentional effects on the auditory steady state response (aSSR). The present study aimed at shedding light on the involvement of ipsilateral and contralateral activations to the attended sound taking into account hemispheric differences and a possible dependency on modulation frequency. In aid of this, a dichotic listening experiment was designed using amplitude-modulated tones that were presented to the left and right ear simultaneously. Participants had to detect target tones in a cued ear while their brain activity was assessed using MEG. Thereby, a modulation of the aSSR by attention could be revealed, interestingly restricted to the left hemisphere and 20 Hz responses: contralateral activations were enhanced while ipsilateral activations turned out to be reduced. Thus, our findings support and extend recent findings, showing that auditory attention can influence the aSSR, but only under specific circumstances and in a complex pattern regarding the different effects for ipsilateral and contralateral activations.
Highlights
In daily life our brain is constantly exposed to a huge amount of sensory information which our perceptual system has to deal with
To find out if the significant main effects are due to attentional processes we looked at the accordant interactions: there was a first order interaction for laterality × attention (F = 4.30, p = 0.04), showing that auditory steady state response (aSSR) contralaterally to tone presentation are enhanced by attention and aSSRs ipsilaterally to tone presentation reduced by attention
With the present work we demonstrate that top-down modulated auditory spatial selective attention affects the power of the aSSR in a specific pattern: attending to the right ear resulted in a contralateral enhancement of the 20 Hz aSSR in the left hemisphere while attending to the left ear led to an ipsilateral reduction of the 20 Hz aSSR in the left hemisphere
Summary
In daily life our brain is constantly exposed to a huge amount of sensory information which our perceptual system has to deal with. Due to limited processing capacities the sensory input has to be selected and structured, so that the brain becomes able to effectively cope with its environment. Attention to auditory stimuli was shown to induce an amplification of neuronal activity elicited by relevant stimuli (Petkov et al, 2004; Woldorff et al, 1993) and an inhibition of neuronal activity related to irrelevant stimuli (Bidet-Caulet et al, 2007) in auditory brain regions. Empirical data from neuroimaging as well as electrophysiology has not been conclusive and only few studies were able to find involvement of auditory cortex (Bidet-Caulet et al, 2007; Fujiwara et al, 1998; Jäncke et al, 1999). For a better understanding of the mechanisms involved in auditory attention, it remains interesting if and how primary and secondary auditory cortices are contributing
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