The Firing Rate Speed Code of Entorhinal Speed Cells Differs across Behaviorally Relevant Time Scales and Does Not Depend on Medial Septum Inputs

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience
Holger DannenbergMichael E Hasselmo

Abstract

The firing rate of speed cells, a dedicated subpopulation of neurons in the medial entorhinal cortex (MEC), is correlated with running speed. This correlation has been interpreted as a speed code used in various computational models for path integration. These models consider firing rate to be linearly tuned by running speed in real-time. However, estimation of firing rates requires integration of spiking events over time, setting constraints on the temporal accuracy of the proposed speed code. We therefore tested whether the proposed speed code by firing rate is accurate at short time scales using data obtained from open-field recordings in male rats and mice. We applied a novel filtering approach differentiating between speed codes at multiple time scales ranging from deciseconds to minutes. In addition, we determined the optimal integration time window for firing-rate estimation using a general likelihood framework and calculated the integration time window that maximizes the correlation between firing rate and running speed. Data show that these time windows are on the order of seconds, setting constraints on real-time speed coding by firing rate. We further show that optogenetic inhibition of either cholinergic, GABAergic,...Continue Reading

Citations

Aug 5, 2020·Proceedings of the National Academy of Sciences of the United States of America·Ian M BrightMarc W Howard
Sep 17, 2021·Learning & Memory·Zachary M GemzikAmy L Griffin
Jul 14, 2021·Physiological Reviews·John J TukkerDietmar Schmitz

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