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Right-hemisphere dominance in visual working memory for color-shape binding

23.558, Saturday, 17-May, 8:30 am - 12:30 pm, Pavilion
Session: Visual memory: Mechanisms and models

Jun Saiki1; 1Graduate School of Human and Environmental Studies, Kyoto University

Binding in visual working memory (VWM) remains equivocal whether non-spatial features are bound together, or independently maintained. Evidence for and against binding in VWM show a lack of binding costs during change detection tasks and the independence of color and shape during feature report tasks, both of which are based on null results. The current study obtained evidence for a significant, functional role of binding in VWM by extending the redundancy gain paradigm, which has been used to examine feature coactivation by the race model inequality test. Instead of a predefined set of critical and distractor features, the current study presented a set of critical features as a memory display with two objects within a participant’s right and left hemifield, followed by a feature-matching task after a variable interval. Participants remembered critical features and judged if a probe object contained any critical features, regardless of the feature locations. The probe contained two (redundant trials), one (single-feature trials), or zero critical features (new trials). To evaluate the objectness effect, redundant trials were divided into grouped and separated conditions in which color and shape belonged to a single object and two objects in the memory display, respectively. The race model inequality test revealed significant feature coactivation only when features were presented to the left side in the memory display of the grouped condition. The N1 amplitude around centro-parietal electrodes, contralateral to the probe in the grouped condition, was significantly larger than in the separated condition but only for the memory-left trials, consistent with the RT data. Moreover, the hallmark of object files, location-based preview benefit (LSPB), was observed only in the probe-left trials, and ERP at posterior parietal sites during 250–350ms revealed a consistent pattern. Binding VWM is formed even when feature-conjunction is task-irrelevant, but dominated in the right hemisphere.

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