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J Neurosci. 2014 Dec 3;34(49):16509-17. doi: 10.1523/JNEUROSCI.2600-14.2014.

Excitation and inhibition compete to control spiking during hippocampal ripples: intracellular study in behaving mice.

Author information

1
NYU Neuroscience Institute, School of Medicine, and.
2
NYU Neuroscience Institute, School of Medicine, and Center for Neural Science, New York University, New York, New York 10016.
3
NYU Neuroscience Institute, School of Medicine, and Center for Neural Science, New York University, New York, New York 10016 gyorgy.buzsaki@nyumc.org.

Abstract

High-frequency ripple oscillations, observed most prominently in the hippocampal CA1 pyramidal layer, are associated with memory consolidation. The cellular and network mechanisms underlying the generation of the rhythm and the recruitment of spikes from pyramidal neurons are still poorly understood. Using intracellular, sharp electrode recordings in freely moving, drug-free mice, we observed consistent large depolarizations in CA1 pyramidal cells during sharp wave ripples, which are associated with ripple frequency fluctuation of the membrane potential ("intracellular ripple"). Despite consistent depolarization, often exceeding pre-ripple spike threshold values, current pulse-induced spikes were strongly suppressed, indicating that spiking was under the control of concurrent shunting inhibition. Ripple events were followed by a prominent afterhyperpolarization and spike suppression. Action potentials during and outside ripples were orthodromic, arguing against ectopic spike generation, which has been postulated by computational models of ripple generation. These findings indicate that dendritic excitation of pyramidal neurons during ripples is countered by shunting of the membrane and postripple silence is mediated by hyperpolarizing inhibition.

KEYWORDS:

action potential threshold; hippocampus; inhibition; intracellular in vivo recording; oscillations; sharp wave ripples

PMID:
25471587
PMCID:
PMC4252557
DOI:
10.1523/JNEUROSCI.2600-14.2014
[Indexed for MEDLINE]
Free PMC Article

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