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Summer Sheremata, George Malcolm, Sarah Shomstein; Visual short-term memory demonstrates retinotopic visual field asymmetries. Journal of Vision 2015;15(12):674. doi: 10.1167/15.12.674.
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Visual short-term memory (VSTM) maintains information across eye movements and distraction. However, VSTM holds a very limited amount of information, with memory capacity reaching a maximum of 3 ± 1 objects. Activity in the parietal cortex mirrors these restrictions, plateauing at a subject's maximum capacity. Parietal cortical activity also shows hemispheric asymmetries in representing memory items across the visual field. Consistent with these asymmetries, memory performance demonstrates a left visual field bias for single-feature objects (Sheremata & Shomstein, 2014). It is, however, an open question which coordinate system, retinotopic or spatiotopic, underlies VSTM biases. Eye position was monitored while subjects performed a color change-detection task for items presented to the left and the right of the monitor while subjects fixated different positions across the visual field. In separate conditions, subjects fixated either the center of the screen (control condition) or locations peripheral to the stimuli. If VSTM is represented in spatiotopic coordinates, then visual field asymmetries should be independent of eye position. If, however, VSTM is retinotopically represented, then visual field performance should be modulated by eye position, reversing when subjects fixate peripheral visual field locations. Results supported retinotopic representations in VSTM, as evidenced by a reversal of visual field asymmetries as compared to the control condition. Further manipulations controlling for spatiotopic location and non-spatial encoding corroborated our findings. These results demonstrate that VSTM, like visuo-spatial processing, is coded in retinotopic coordinates.
Meeting abstract presented at VSS 2015
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