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LIT-1953: Ephaptic coupling of cortical neurons

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StatusActive — read 2026-11-03 (NOTE-1516), main text, online methods and references, from the scan of the published article on gwern.net, at the owner's direction; the supplementary material was not read. Worth reading as the measurement of how large, and how small, ephaptic effects are at physiological field strengths: fields like the LFP's shift spike timing and synchronize nearby neurons without changing spike counts. It explains them by Kirchhoff's laws, so it is not evidence against micro-level description.
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Tagsneuroscience
Cited as “paper” byNOTE-1516 — Anastassiou et al. — Ephaptic coupling of cortical neurons
Cited as “source” byTHEORY-1346 — In rat cortical slices with synapses blocked, extracellular fields of the local field potential's size, applied by an electrode, shift the membrane potential of layer 5 pyramidal neurons by less than 0.5 mV at frequencies up to 100 Hz and, with spiking driven by current, phase-lock spike times without changing spike counts, most effectively for slow fields, and synchronize nearby neurons; the authors explain the effect by Kirchhoff's circuit laws and a fixed firing threshold

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Anastassiou, C. A., Perin, R., Markram, H., Koch, C. (2011). Ephaptic coupling of cortical neurons. Nature Neuroscience, 14(2), 217-223. doi:10.1038/nn.2727.

Key takeaways

  • Ephaptic coupling at physiological strengths changes when neurons fire, not whether they fire: membrane effects under 0.5 mV, no extra spikes, phase locking to slow fields.
  • Slow fields work best. Entrainment was strongest at 1 Hz, weaker at 8 Hz, and at 30 Hz needed fields nearly ten times larger.
  • The fields were applied by an electrode. The paper shows neurons respond to fields of the LFP’s size, not that the fields neurons generate feed back on them in vivo.

Standing in the record

Registered as Jennings’s evidence against weak emergence (LIT-1963, p. 35). The paper supports her quotation, that “groups of cells change their local electric environment, which in turn feeds back onto the electric activity of all of its members” (p. 217). It does not support her inference, that “brain activity cannot be described simply through local interactions”: the authors call the potentials “a simple consequence of Kirchhoffs’ circuit laws” (p. 221). It is also the second appearance of ephaptic coupling in the record, after LIT-388’s hypothesis about sentience, on which it is silent.

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