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Sarah Shomstein, Dwight Kravitz, Marlene Behrmann; Temporal dynamics of an attentional switch. Journal of Vision 2007;7(9):184. doi: https://doi.org/10.1167/7.9.184.
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Recent neuroimaging studies have suggested an important role for a network of fronto-parietal regions in attentional switching. Several regions within the frontal cortex (e.g., MFG , FEF, etc) as well as regions within the posterior parietal cortex (e.g., SPL and precuneus) exhibit selective activation time locked to shifts of attention. Little is known about the temporal dynamics of this circuit. We examined cortical activity of human observers during shifts of attention between vision and audition using event related potentials (ERP). Participants viewed an RSVP stream of letters (4 letters/sec) appearing in the center of a computer screen (surrounded by distractor RSVP streams); simultaneously, they listened to letters spoken binaurally through headphones. Before each run, a verbal instruction directed attention to either the auditory or the visual stream. Occasional digit targets appeared within the attended (auditory or visual) stream and participants pressed a button to indicate target detection. If the digit was a ‘2,’ participants were to maintain attention on the currently attended modality; if it was a ‘4,’ they were to switch attention to the other sensory modality and to begin to monitor that stream. ERP components in visual sensory areas exhibited enhanced early and late components following a shift from audition to vision, as compared to a shift from vision to audition, reflecting attentional modulation for the attended sensory modality. Of interest was the temporal dynamic of shift-related components observed over frontal and parietal electrodes following the instruction to shift attention between modalities in either direction. Activity over frontal electrodes exhibited enhancements that were earlier than those observed over the parietal electrodes. These results introduce a temporal dimension to the existing fMRI findings, suggesting that frontal areas are engaged earlier than the parietal attentional shifting areas and may even serve as the top-down signal to activate parietal cortex.
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