Mechanisms of Input-Frequency Dependent Pattern Separation in the Dentate Gyrus
Selena Singh, Suzanna Becker, McMaster University, Canada; Thomas Trappenberg, Abraham Nunes, Dalhousie University, Canada
Session:
Posters 3B Poster
Presentation Time:
Sat, 26 Aug, 13:00 - 15:00 United Kingdom Time
Abstract:
Pattern separation (PS) within the dentate gyrus (DG) is dependent on oscillatory perforant path input frequencies in a “U” shaped fashion, where slow and fast input frequencies support PS, while intermediate frequencies disrupt PS. The mechanisms governing this “U” shaped relationship are unclear. We implemented a biophysical model of the DG that replicates the empirically observed “U”-shaped input frequency-PS relationship and its associated oscillatory electrophysiological signatures. We subsequently evaluated the network’s PS ability using an adapted spatiotemporal task. We undertook systematic lesion studies to identify the network-level mechanisms driving the “U” shaped input frequency-PS relationship. A minimal circuit of a single granule cell (GC) stimulated with oscillatory inputs was also used to study cellular-level mechanisms. Lesioning synapses onto GCs did not impact the “U”-shaped input frequency-PS relationship. GC interspike interval was found to be input frequency dependent in a “U”-shaped fashion, paralleling frequency-dependent PS observed at the network level. We conclude that independent of network-level inhibition, GCs may intrinsically be capable of producing a “U” shaped input frequency-PS relationship. GCs may preferentially decorrelate slow and fast inputs via spike timing reorganisation.