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Jonathan Gill, George Alvarez; The bias towards a contralateral representation in parietal activity is increased during full-field attentional tracking. Journal of Vision 2011;11(11):178. doi: 10.1167/11.11.178.
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© ARVO (1962-2015); The Authors (2016-present)
Activation in parietal regions is contralaterally biased, showing a stronger response when attention is directed to the contralateral visual field than to the ipsilateral visual field. Here we explored how parietal activity changes when attention is divided across the both halves of the visual field simultaneously. While undergoing whole brain imaging in a 3T fMRI scanner, observers performed an attentional tracking task. Displays consisted of 16 circles, with 4 circles appearing in each quadrant of the visual field. A variable number of targets were cued (turned red for 1 second), and then all items appeared identical and moved while observers attentionally tracked the targets. On some trials observers tracked a single target that appeared in one of the four quadrants. On other trials, two targets appeared in separate quadrants, diagonally across from each other. We then analyzed the patterns of activation for each of these conditions within parietal regions determined by a separate functional localizer run (tracking > passive viewing). Activation patterns for the 2 target diagonal conditions were well predicted by the average pattern of the component target locations. For example, the pattern of activation for tracking 2 targets in the top-left / bottom-right configuration was predicted by averaging the patterns for tracking 1 target in the top-left and 1 target in the bottom right. Interestingly, the patterns of activity were consistent with a weighted average of the component patterns that was biased towards the pattern for the contralateral target location. This bias appeared to be stronger for the left parietal lobe than for the right parietal lobe. These results suggest that each parietal lobe can select and track targets in both the left and right visual field. However, under conditions of full-field attention, the bias towards a contralateral representation is increased in parietal regions.
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