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Burst ensemble multiplexing: connecting dendritic spikes with cortical inhibition

Banff International Research Station for Mathematical Innovation and Discovery

Two distinct types of inputs impinge on different spatial compartments of pyramidal neurons of the neocortex. A popular view holds that the input impinging on the distal dendrites modulates the gain of the somatic input encoding. This gain modulation is thought to participate in top-down processes such as attention, sensory predictions and reward expectation. Here we use computational and theoretical analyses to determine how the two input streams are represented simultaneously in a neural ensemble. We find that dendritic calcium spikes in the distal dendrites allows multiplexing of the distal and somatic input streams by modifying the proportion of burst and singlet events. Two ensemble-average quantities encode the distal and somatic streams independently: the event rate and the burst probability, respectively. Simulations based on a two-compartment model reveal that this novel neural code can more than double the rate of information transfer over a large frequency bandwidth. To corroborate these findings, we determined analytically the parameters regulating mutual information in a point process model of bursting. Secondly, we find that an inhibitory microcircuitry combining short-term facilitation and short-term depression can decode the distal and somatic streams independently. These results suggest a novel functional role of both active dendrites and the stereotypical patterns with which inhibitory cell types interconnect in the neocortex. Burst ensemble multiplexing, we suggest, is a general code used by the neural system to flexibly combine two distinct streams of information.

Mathematics; Statistics; Probability theory and stochastic processes; Applied statistics

video/mp4

Author affiliation: University of Ottawa

2019-03-09

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/68550

Unreviewed

http://creativecommons.org/licenses/by-nc-nd/4.0/