Neural correlates of parallel and distributed engrams

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Chang, HaoRan
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta. : University of Lethbridge, Dept. of Neuroscience
From the waking hours into the depths of sleep, the hippocampus and the neocortex engage in an enigmatic dialogue on that which occurs, that which had occurred and that which could occur eventually. Together, this information weaves the memories of our past and the knowledge of our world. Yet, if one attempts to eavesdrop on this conversation, they would be perplexed to discover that the details that would give rise to such sophisticated structures could mostly be diluted into the mapping of space. What invisible bonds may tie space and memory in the brain, this present thesis offers no answers for. What it does offer, instead, are more enigmas to be fancied over and more confusions to be resolved: (1) The neural representation of space is found across multiple regions of the dorsal cortex and necessitates an intact hippocampus to form; (2) During offline periods, the retrosplenial cortex spontaneously reinstates patterns of activity specifically related to the locations of spatial landmarks; (3) The secondary motor cortex, in contrast, reinstates a conjunction of spatial and non-spatial information, in the forms of recent trajectories undertaken in an environment and the locations of visuo-tactile landmarks, respectively. Together, these results elaborate a spatial code that is heavily redundant and dispersed, with a link to mnemonic processing — a neural correlate of parallel and distributed engrams.
learning & memory , consolidation , hippocampo-neocortical dialogue , reactivation , place cells , two-photon calcium imaging , spatial/non-spatial representations , virtual reality , spatial landmarks , pattern completion , engrams , spatial memory , navigation , sharp-wave ripples , retrospenial cortex , hippocampal lesion , secondary motor cortex