Abstract
Previous magnetoencephalography (MEG) studies have revealed gamma-band activity at sensors over parietal and fronto-temporal cortex during the delay phase of auditory spatial and non-spatial match-to-sample tasks, respectively. While this activity was interpreted as reflecting the memory maintenance of sound features, we noted that task-related activation differences might have been present already prior to the onset of the sample stimulus. The present study focused on the interval between a visual cue indicating which sound feature was to be memorized (lateralization or pitch) and sample sound presentation to test for task-related activation differences preceding stimulus encoding. MEG spectral activity was analyzed with cluster randomization tests (N = 15). Whereas there were no differences in frequencies below 40 Hz, gamma-band spectral amplitude (about 50–65 and 90–100 Hz) was higher for the lateralization than the pitch task. This activity was localized at right posterior and central sensors and present for several hundred ms after task cue offset. Activity at 50–65 Hz was also increased throughout the delay phase for the lateralization compared with the pitch task. Apparently cortical networks related to auditory spatial processing were activated after participants had been informed about the task.
Highlights
IntroductionSubsequent work focusing on stimulus-specific activations has further supported both the role of GBA for the representation of task-relevant sound features in working memory and the distinction between the processing of spatial versus non-spatial sound features in posterior versus anterior brain regions, respectively[16]
Representations of the relevant stimulus features[15]
We searched for three-dimensional clusters defined by sensor space, time and frequency that differed between the auditory spatial and non-spatial working memory tasks
Summary
Subsequent work focusing on stimulus-specific activations has further supported both the role of GBA for the representation of task-relevant sound features in working memory and the distinction between the processing of spatial versus non-spatial sound features in posterior versus anterior brain regions, respectively[16]. For this aim we presented valid pre-cues at trial onset, 2 s prior to the onset of S1 They indicated whether spatial or non-spatial stimulus features had to be processed in the ensuing auditory working memory task. FMRI studies have shown an activation of sensory-selective regions following cues informing about the subsequently presented stimulus category[35] This modulation as well as working memory performance was correlated with the magnitude of functional connectivity increases between sensory and fronto-parietal networks. We explored the alpha and beta bands because of their implication in anticipatory attention as described above
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