Brain State Dependence of Hippocampal Subthreshold Activity in Awake Mice

Publication date: 3 January 2017
Source:Cell Reports, Volume 18, Issue 1
Author(s): Brad K. Hulse, Evgueniy V. Lubenov, Athanassios G. Siapas
Monitoring the membrane potential of individual neurons has uncovered how single-cell properties contribute to network processing across different brain states in neocortex. In contrast, the subthreshold modulation of hippocampal neurons by brain state has not been systematically characterized. To address this, we combined whole-cell recordings from dentate granule cells and CA1 pyramidal neurons with multisite extracellular recordings and behavioral measurements in awake mice. We show that the average membrane potential, amplitude of subthreshold fluctuations, and distance to spike threshold are all modulated by brain state. Furthermore, even within individual states, rapid variations in arousal are reflected in membrane potential fluctuations. These factors produce depolarizing ramps in the membrane potential of hippocampal neurons that precede ripples and mirror transitions to a network regime conducive for ripple generation. These results suggest that there are coordinated shifts in the subthreshold dynamics of individual neurons that underlie the transitions between distinct modes of hippocampal processing.

Graphical abstract

Teaser

Hulse et al. show that the average membrane potential and the amplitude of subthreshold fluctuations of hippocampal neurons systematically change with brain state and arousal. This results in membrane potential ramps that precede ripples and mirror transitions to a network regime conducive for ripple generation.


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