Functional Magnetic Resonance Imaging and Computational Modeling
A hippocampal model is utilized to simulate activation in humans detected using functional magnetic resonance imaging (fMRI). During a picture encoding task, fMRI measurements demonstrate increased signal intensity changes in the hippocampal formation and parahippocampal gyrus during sequential presentation of novel pictures, as compared to activation levels during repeated presentation of a single picture. In the hippocampal model, sequential presentation of novel patterns activates separate populations of neurons in the dentate gyrus, region CA3 and region CA 1. In contrast, repeated presentation of a single pattern activates the same subpopulation of neurons. In a model of region CA3, repeated activation of the same subpopulation results in decreased activity due to activation of a calcium-dependent potassium current. These results suggest that the changes in fMRI signal intensity during the presentation of novel vs. repeating pictures may be related to neuronal adaptation mediated by calcium-dependent potassium currents in hippocampal neurons.
KeywordsDentate Gyrus Hippocampal Formation Functional Magnetic Resonance Image Inhibitory Interneuron Parahippocampal Gyrus
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