When shared concept cells support associations: Theory of overlapping memory engrams
Assemblies of neurons, called concepts cells, encode acquired concepts in human Medial Temporal Lobe. Those concept cells that are shared between two assemblies have been hypothesized to encode associations between concepts. Here we test this hypothesis in a computational model of attractor neural networks. We find that for concepts encoded in sparse neural assemblies there is a minimal fraction cmin of neurons shared between assemblies below which associations cannot be reliably implemented; and a maximal fraction cmax of shared neurons above which single concepts can no longer be retrieved. In the presence of a periodically modulated background signal, such as hippocampal oscillations, recall takes the form of association chains reminiscent of those postulated by theories of free recall of words. Predictions of an iterative overlap-generating model match experimental data on the number of concepts to which a neuron responds.
WG and CG were supported by the Swiss National Science Foundation (www.nsf.gov), grant agreement 200020_184615 and by the European Union Horizon 2020 Framework Program (https:// ec.europa.eu/programmes/horizon2020/) under agreement no. 785907 (HumanBrain Project, SGA2). RQQ acknowledges support from Biotechnology and Biological Sciences Research Council.
CitationPLoS Comput Biol 17(12): e1009691
Author affiliationCentre for Systems Neuroscience
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