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Serra E Favila, Jonathan Winawer; Retinotopic reactivation in human visual cortex tracks memory success in a single-shot encoding paradigm. Journal of Vision 2020;20(11):762. doi: https://doi.org/10.1167/jov.20.11.762.
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More than twenty cortical areas containing maps of the visual field have been identified. By training subjects extensively on a few memories, we previously demonstrated that these maps are retinotopically activated during long-term retrieval of spatial information (Favila et al., bioRxiv 2019). Here, we extended this work by asking three questions: 1) Is extensive training necessary to observe these results? 2) Does reactivation quality relate to memory success? 3) Does reactivation occur when spatial information is not explicitly probed? We designed a single-shot spatial memory paradigm to address these questions. First, based on subjective ratings from six subjects, we identified 480 object images that were recognizable in the near periphery. A different group of subjects (N=5) then encountered these stimuli across three scanned, interleaved tasks: encoding, recognition memory, and spatial memory retrieval. During encoding blocks, subjects were presented with objects, each of which appeared only once in one of four visual field locations. During recognition blocks, subjects were presented with previously studied and new objects at central fixation and made old/new judgments. This task did not require remembering the spatial location of the objects. During spatial memory retrieval blocks, subjects were presented with old objects at central fixation and explicitly cued to make a four alternative forced-choice decision about the location of the object during encoding. Across the visual system, we observed reliable retintopically-specific reactivation during successful, but not unsuccessful, spatial memory retrieval. We also observed incidental reactivation during successful recognition of objects for which subjects later expressed accurate spatial memory. Spatial tuning in both memory tasks was consistent with our previous work. Our results indicate that memory retrieval can evoke organized, spatially tuned activity in visual cortex, that this activity tracks recall accuracy, and that it can be observed during non-spatial memory tasks and for stimuli studied only once.
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