Abstract
In this study, we focus our investigation on task-specific cognitive modulation of early cortical auditory processing in human cerebral cortex. During the experiments, we acquired whole-head magnetoencephalography data while participants were performing an auditory delayed-match-to-sample (DMS) task and associated control tasks. Using a spatial filtering beamformer technique to simultaneously estimate multiple source activities inside the human brain, we observed a significant DMS-specific suppression of the auditory evoked response to the second stimulus in a sound pair, with the center of the effect being located in the vicinity of the left auditory cortex. For the right auditory cortex, a non-invariant suppression effect was observed in both DMS and control tasks. Furthermore, analysis of coherence revealed a beta band (12∼20 Hz) DMS-specific enhanced functional interaction between the sources in left auditory cortex and those in left inferior frontal gyrus, which has been shown to be involved in short-term memory processing during the delay period of DMS task. Our findings support the view that early evoked cortical responses to incoming acoustic stimuli can be modulated by task-specific cognitive functions by means of frontal–temporal functional interactions.
Highlights
Modulation of auditory cortical responses evoked by acoustic stimuli has been widely observed in both animal and human research
We focused our research on the task-specific AER suppression during performance of an auditory DMS task and hypothesized that the DMS-related cognitive functions play active roles in the observed modulation effect
In the left auditory cortex, by controlling the habituation effect with identical timelines for each trial and the attention effect by instructing subjects to listen to the sounds during both control and DMS conditions, we have demonstrated a suppressive AER modulation effect correlated to performance of a DMS task that involved overt STM maintenance and manipulation
Summary
Modulation of auditory cortical responses evoked by acoustic stimuli has been widely observed in both animal and human research. As one of the early MEG/EEG evoked cortical responses with a latency of around 100 ms after stimulus onset, the M100/N1 is believed to be correlated with the detection of changes in the acoustic environment (Näätänen and Picton, 1987; Hari, 1990). Modulation of this transient response has shown both enhancement and suppression effects in previous experiments. Forward masking and repetitive suppression hypotheses emphasize the intrinsic automatic adaptation to repeated stimulus presentations (for a review, see Grill-Spector et al, 2006 and the comment in Baldeweg, 2006) and insensitivity to different cognitive and behavioral conditions, whereas feedback modulation can arise from functional interactions between multiple regions involved in specific cognitive functions
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