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Irida Mance, Edward Vogel; Temporal Dynamics of Shifting Visual Attention Between Cerebral Hemispheres. Journal of Vision 2012;12(9):541. doi: 10.1167/12.9.541.
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Studies with split-brain patients have demonstrated that attention can often operate independently and in parallel in each hemisphere. However, it is still unclear whether attention shows similar hemispheric independence in healthy, intact individuals. Here, we recorded event-related potentials (ERPs) from subjects while they performed a sustained tracking task that often required them to shift attention to a different visual field during the trial. Specifically, participants attended to one of four rotating pinwheels (2 in each hemifield). Halfway through the trial, a cue prompted them to either maintain their attention at the original location, or to switch to a new location. On switch trials, the new location was either in the same hemifield as the initially tracked item, or in the opposite hemifield. The lateralized arrangement of stimuli allowed us to use the contralateral delay activity (CDA) as a neural marker of which items the participants were processing at a given moment during the trial. For between hemifield switches, we found that individuals quickly began to engage attention at the new location shortly following the switch cue onset and that this neural activity had now shifted to the opposite hemisphere (i.e., contralateral to the new location). Furthermore, by decomposing the CDA into ipsilateral and contralateral components, we found that individuals began to engage attention at the new location 200ms prior to disengaging (measured as a drop in amplitude) from the previously attended location. That is, rather than a sequential shift process of disengaging the old location before engaging the new, we found evidence that the engagement of attention to the new item preceded the complete disengagement of attention at the old location. These results provide additional support for a model of attention in which the two hemispheres can process, engage, and disengage, attention independently.
Meeting abstract presented at VSS 2012
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