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Summer Sheremata, Sarah Shomstein; Dynamic reallocation of resources in visual short-term memory. Journal of Vision 2014;14(10):1370. doi: 10.1167/14.10.1370.
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Visual short-term memory (VSTM) is a capacity-limited system for maintaining visual information across brief durations of time. Hemispheric asymmetries are apparent in VSTM within topographically defined regions of the parietal lobe (Sheremata et al., 2010). Consistent with topographic mapping, the left hemisphere coded items in the right, or contralateral, visual field. Importantly, as memory load increased, the right hemisphere coded items bilaterally. These neuroimaging results suggest that memory demands modulate right parietal cortex representations, setting forth the prediction that memory performance across the visual field varies based upon memory demands. Because activity in posterior parietal cortex reflects feature-load dependence during VSTM (Xu & Chun, 2006), we predicted that differences in performance should occur in a feature-load dependent manner. In a series of experiments, we investigated the effects of feature-load on dynamic reallocation of resources in VSTM. In each experiment, participants performed a change detection task in which either color or shape could change. In the single-feature condition, participants were cued to a single feature, while in the two-feature condition either feature could change. Our results demonstrate feature-load dependent changes in visual field bias. First, we demonstrated a reduced feature cost for items in the right visual field. We then excluded the possibility that hemispheric asymmetries could be caused by perceptual or decision-making processes, and demonstrated that hemifield asymmetries occurred within randomized blocks. Finally, we hypothesized that if VSTM task demands result in a reallocation of resources from the left to right visual field, then task-set should guide this reallocation. We found that VSTM performance is modulated by manipulating task-set, demonstrating direct evidence for the role of VSTM task demands on hemifield asymmetries. Consistent with hemispheric asymmetries reported in functional imaging, these experiments demonstrate that VSTM task demands result in a dynamic reallocation of resources across the visual field.
Meeting abstract presented at VSS 2014
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