Two-Stage Processing of Sounds Explains Behavioral Performance Variations due to Changes in Stimulus Contrast and Selective Attention: An MEG Study

Abstract

Selectively attending to task-relevant sounds whilst ignoring background noise is one of the most amazing feats performed by the human brain. Here, we studied the underlying neural mechanisms by recording magnetoencephalographic (MEG) responses of 14 healthy human subjects while they performed a near-threshold auditory discrimination task vs. a visual control task of similar difficulty. The auditory stimuli consisted of notch-filtered continuous noise masker sounds, and of 1020-Hz target tones occasionally () replacing 1000-Hz standard tones of 300-ms duration that were embedded at the center of the notches, the widths of which were parametrically varied. As a control for masker effects, tone-evoked responses were additionally recorded without masker sound. Selective attention to tones significantly increased the amplitude of the onset M100 response at 100 ms to the standard tones during presence of the masker sounds especially with notches narrower than the critical band. Further, attention modulated sustained response most clearly at 300–400 ms time range from sound onset, with narrower notches than in case of the M100, thus selectively reducing the masker-induced suppression of the tone-evoked response. Our results show evidence of a multiple-stage filtering mechanism of sensory input in the human auditory cortex: 1) one at early (100 ms) latencies bilaterally in posterior parts of the secondary auditory areas, and 2) adaptive filtering of attended sounds from task-irrelevant background masker at longer latency (300 ms) in more medial auditory cortical regions, predominantly in the left hemisphere, enhancing processing of near-threshold sounds.

Modulation of response patterns in human auditory cortex during a target detection task: An intracranial electrophysiology study

“…For instance, attended sounds embedded in notch-filtered noise elicited a modest increase in the neuromagnetic evoked M1 component, whereas the sustained portion of the response featured a robust increase peaking at 300–400 ms after stimulus onset (Kauramäki et al, 2012). Attentional effects on AEPs and AEFs that were maximal within this time frame have been also demonstrated in a variety of other experimental paradigms (Hari et al, 1989; Arthur et al, 1991; Nahum et al, 2009).…”

Action-related auditory ERP attenuation: Paradigms and hypotheses

“…Attention sets can not only be established for different modalities, input channels or moments in time (for a summary, see Lange, 2013) but for task-relevant sound features as well. Selective N1(m) enhancements have been found for example, when the task required attending a given tone frequency (Kauramäki, Jääskeläinen, & Sams, 2007;Kauramäki, Jääskeläinen, Hänninen, Auranen, Nummenmaa, Lampinen, & Sams, 2012;Okamoto, et al, 2007). It has been also demonstrated that unexpected, taskirrelevant auditory events presented in the same channel as the task-relevant auditory events may disrupt the task-relevant attention set, which leads to the removal of the attentional N1-(and possibly P2) -enhancement for closely following task-relevant events (Horváth & Winkler, 2010;Horváth, 2014aHorváth, , 2014b.…”

Probing the sensory effects of involuntary attention change by ERPs to auditory transients

“…Hillyard, Hink, Schwent, and Picton (1973) found that sounds presented in the attended ear elicited higher amplitude N1 (Näätänen & Picton, 1987) waveforms than those presented in the unattended one. Various studies found similar N1 (and N1m-the magnetic counterpart of N1) enhancements for attention sets induced by various types of task demands (e.g., for attended ears: Rif, Hari, Hämäläinen, & Sams, 1991;Woldorff et al, 1993;Woldorff & Hillyard, 1991; attended frequencies: Kauramäki et al, 2012;Kauramäki, Jääskeläinen, & Sams, 2007;Okamoto, Stracke, Wolters, Schmael, & Pantev, 2007; attended frequency or ear: Ozaki et al, 2004; a given attended moment in time: e.g., Lange, Rösler & Röder, 2003; for a recent summary, see Lange, 2013). A number of studies suggest that the enhancement of the N1 waveform is due to the superposition of different event-related potentials (ERPs) or ERP effects: Besides a "genuine" N1 modulation, an ERP of different origin (Alho, Paavilainen, Reinikainen, Sams, & Näätänen, 1986;Knight, Hillyard, Woods, & Neville, 1981) overlapping the N1-termed processing negativity (PN, Näätänen, Gaillard, & Mäntysalo, 1978), or negative difference (Nd, Hansen & Hillyard, 1980)-also contributes to the amplitude increase.…”