Top-down modulation of the auditory steady-state response in a task-switch paradigm

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 fi ndings 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 fi ndings support and extend recent fi ndings, showing that auditory attention can infl uence the aSSR, but only under specifi c circumstances and in a complex pattern regarding the different effects for ipsilateral and contralateral activations.

Sustained Selective Attention to Competing Amplitude-Modulations in Human Auditory Cortex

“…In contrast to other findings based on shorter intervals [10], [11], [12], [13], sustained AM-selective attention produced overall stronger neural enhancement for the non-target AM than the target AM. Thus, overall, this main result does not support the notion of sustained AM-selective attentional enhancement in AC.…”

“…Closer inspection of the initial sound interval revealed a trend that fits well with the previous findings of attentional response enhancement during this interval [10], [11], [12], [13]. The fact that we could not detect a more robust (statistically significant) AM-selective attentional response enhancement during this interval may be due to the rather limited number of data points (i.e., few trials related to the long duration of our stimuli).…”

“…Previous studies have shown that selective attention to an AM sound enhances the SSR evoked by the AM of that sound, compared with the SSR evoked by a competing, unattended AM sound with distinct tone frequency or location [10], [11], [12], [13]. The main goal of our study was to test if similar selective attentional enhancement occurs in the absence of location and pitch cues, i.e., when attention is focused exclusively and continuously on a specific ongoing AM.…”

Task Switching Processes

“…In prepared conditions, switch and repeat trials diverge as early as 150 ms, but at short CTIs, this effect is delayed until the switch positivity is resolved (Karayanidis et al, 2003;Muller, Schlee, Hartmann, Lorenz, & Weisz, 2009;Nicholson et al, 2005). N2 amplitude progressively increases across single-task, repeat, and switch trials (Goffaux, Phillips, Sinai, & Pushkar, 2006;Jost et al, 2008;Karayanidis, Whitson, Heathcote, & Michie, 2011), from univalent to bivalent targets (Hsieh & Liu, 2008;Karayanidis et al, 2003;Poulsen et al, 2005), and progressively reduces with increasing the length of repeat runs (i.e., ABB vs. ABBB, vs. ABBBB; Wylie et al, 2003).…”

Evidence for modality-specific but not frequency-specific modulation of human primary auditory cortex by attention

“…Following a different approach, Müller et al (2009) presented a 20 Hz AM sound to one ear and a 45 Hz AM sound to the other ear (AM rate counterbalanced between ears), both sounds consisting of a carrier frequency of 655 Hz. Participants were instructed to attend to one ear or the other ear and press a button when the AM rate changed within a 800 ms stimulus epoch (the probability of a change was 0.10).…”