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Brice Kuhl, Wilma Bainbridge, Marvin Chun; Decoding retrieval of competing visual memories from neural reactivation. Journal of Vision 2011;11(11):1240. doi: 10.1167/11.11.1240.
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© ARVO (1962-2015); The Authors (2016-present)
Cortical regions activated during the encoding of visual experience are often ‘reactivated’ when that visual experience is remembered. The present study assessed how or whether competition between memories is reflected in reactivation. Subjects (n = 20) encoded pairings of words (nouns) with images of faces, scenes, or objects. Word-image pairings were repeated twice; at a third presentation, some words were paired with new images and some with the same images. In cases where a word was paired with a new image, subjects were instructed to disregard the former image (competitor) and attempt to remember the new image (target). During retrieval subjects were presented with words and attempted to retrieve the corresponding target image and to indicate the category (face, object, scene) of the image. Multi-voxel pattern analysis (MVPA) of fMRI data measured the extent to which face-, object-, or scene-related patterns of activity elicited in ventral occipito-temporal cortex during encoding were reactivated during retrieval. Successful retrieval of target images was associated with robust neural reactivation of the target representation, but also significant – albeit weaker – reactivation of the competing representation, reflecting an influence of competing images even when target images were successfully remembered. When competing images were mistakenly retrieved (instead of the relevant target), there was robust evidence for reactivation of competing representations but no evidence for target reactivation. Additional analyses revealed (a) fronto-parietal responses during retrieval that were highest when the relative evidence for target vs. competing memories was lowest, and (b) prefrontal responses during encoding that were positively associated with subsequent reactivation of target vs. competing memories. Together, these results indicate that successes and failures in retrieving target memories amidst competing memories are borne out in neural measures of reactivation; moreover, these results point to specific prefrontal and parietal mechanisms that guide visual memory when competition is present.
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