Ephaptic coupling of cortical neurons.
The electrochemical processes that underlie neural function manifest themselves in ceaseless spatiotemporal field fluctuations. However, extracellular fields feed back onto the electric potential across the neuronal membrane via ephaptic coupling, independent of synapses. The extent to which such ephaptic coupling alters the functioning of neurons under physiological conditions remains unclear. To address this question, we stimulated and recorded from rat cortical pyramidal neurons in slices with a 12-electrode setup. We found that extracellular fields induced ephaptically mediated changes in the somatic membrane potential that were less than 0.5 mV under subthreshold conditions. Despite their small size, these fields could strongly entrain action potentials, particularly for slow (<8 Hz) fluctuations of the extracellular field. Finally, we simultaneously measured from up to four patched neurons located proximally to each other. Our findings indicate that endogenous brain activity can causally affect neural function through field effects under physiological conditions.
Division of Biology, California Institute of Technology, Pasadena, California, USA. costas@caltech.edu
Costas A
CA
Anastassiou
Rodrigo
R
Perin
Henry
H
Markram
Christof
C
Koch
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002450:Cell Communication / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology*; D004558:Electric Stimulation; D004594:Electrophysiology; D005110:Extracellular Space / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology*; D017966:Pyramidal Cells / Q000502:physiology*; D051381:Rats; D013569:Synapses / Q000502:physiology
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