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Neuron. 2018 Nov 7;100(3):564-578.e3. doi: 10.1016/j.neuron.2018.09.018. Epub 2018 Oct 4.

Ephaptic Coupling Promotes Synchronous Firing of Cerebellar Purkinje Cells.

Author information

1
Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
2
Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA. Electronic address: wade_regehr@hms.harvard.edu.

Abstract

Correlated neuronal activity at various timescales plays an important role in information transfer and processing. We find that in awake-behaving mice, an unexpectedly large fraction of neighboring Purkinje cells (PCs) exhibit sub-millisecond synchrony. Correlated firing usually arises from chemical or electrical synapses, but, surprisingly, neither is required to generate PC synchrony. We therefore assessed ephaptic coupling, a mechanism in which neurons communicate via extracellular electrical signals. In the neocortex, ephaptic signals from many neurons summate to entrain spiking on slow timescales, but extracellular signals from individual cells are thought to be too small to synchronize firing. Here we find that a single PC generates sufficiently large extracellular potentials to open sodium channels in nearby PC axons. Rapid synchronization is made possible because ephaptic signals generated by PCs peak during the rising phase of action potentials. These findings show that ephaptic coupling contributes to the prevalent synchronization of nearby PCs.

PMID:
30293822
DOI:
10.1016/j.neuron.2018.09.018
[Indexed for MEDLINE]

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