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Halely Balaban, Trafton Drew, Roy Luria; An object-based pointer system in visual working memory. Journal of Vision 2018;18(10):185. doi: 10.1167/18.10.185.
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© ARVO (1962-2015); The Authors (2016-present)
Visual working memory (VWM) representations must be stably mapped to the relevant stimuli in order to guide behavior. This "pointer system" (e.g., Pylyshyn, 2000) allows the correct representation to be accessed and updated following changes. A loss of this mapping makes updating impossible, and instead triggers a resetting process, namely removing the unmapped representation and re-encoding the new information (Balaban & Luria, 2017). Since resetting indicates a loss of the stimuli-to-representations mapping, it can be used to study the pointer system: changes that trigger resetting presumably involve factors that are critical to the pointer system. In a feature-updating task, we utilized the ERP signature of resetting to ask whether the pointers operate in an object-based or feature-based manner. We used moving colored-shapes in a change-detection task. In different blocks, either the shape or the color were relevant. During the movement, items could separate into independently moving shape-halves. In the shape-task, the separation not only destroyed a previously coherent object, but also changed the task-relevant dimension. In contrast, in the color-task the separation left the colors identical, destroying only the objects while maintaining the task-relevant features (colors). Critically, the results indicated that separation destroyed the mapping in both tasks, regardless of the relevant dimension, triggering a resetting process with a drop in the contralateral delay activity (the ERP marker of VWM) amplitude. This suggests the pointers system is object-based. An extreme object-based prediction is that in a color change-detection task, even a colored square's separation into two identical colored rectangles should produce resetting, as long as the initial colored square was encoded as one object. In another experiment this was indeed found, further corroborating an object-based mapping. Aside from supporting objects' role in VWM's pointer system, our results demonstrate that resetting can reveal how internal representations relate to the outside environment.
Meeting abstract presented at VSS 2018
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