Preconfigured, Skewed Distribution of Firing Rates in the Hippocampus and Entorhinal Cortex

• Firing rates of neurons in the hippocampal region show lognormal-like distribution
• Discharge rates of single cells are correlated across brain states and environments
• Rate distributions may be supported by lognormal distribution of spike transfer strength
• Preconfigured, highly active minority neurons may dominate information transmission

SummaryDespite the importance of the discharge frequency in neuronal communication, little is known about the firing-rate patterns of cortical populations. Using large-scale recordings from multiple layers of the entorhinal-hippocampal loop, we found that the firing rates of principal neurons showed a lognormal-like distribution in all brain states. Mean and peak rates within place fields of hippocampal neurons were also strongly skewed. Importantly, firing rates of the same neurons showed reliable correlations in different brain states and testing situations, as well as across familiar and novel environments. The fraction of neurons that participated in population oscillations displayed a lognormal pattern. Such skewed firing rates of individual neurons may be due to a skewed distribution of synaptic weights, which is supported by our observation of a lognormal distribution of the efficacy of spike transfer from principal neurons to interneurons. The persistent skewed distribution of firing rates implies that a preconfigured, highly active minority dominates information transmission in cortical networks.

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