Journal of Computational Neuroscience

, Volume 6, Issue 2, pp 169–184 | Cite as

Electrical Interactions via the Extracellular Potential Near Cell Bodies

  • Gary R. HoltEmail author
  • Christof Koch


Ephaptic interactions between a neuron and axons or dendrites passing by its cell body can be, in principle, more significant than ephaptic interactions among axons in a fiber tract. Extracellular action potentials outside axons are small in amplitude and spatially spread out, while they are larger in amplitude and much more spatially confined near cell bodies. We estimated the extracellular potentials associated with an action potential in a cortical pyramidal cell using standard one-dimensional cable theory and volume conductor theory. Their spatial and temporal pattern reveal much about the location and timing of currents in the cell, especially in combination with a known morphology, and simple experiments could resolve questions about spike initiation. From the extracellular potential we compute the ephaptically induced polarization in a nearby passive cable. The magnitude of this induced voltage can be several mV, does not spread electrotonically, and depends only weakly on the passive properties of the cable. We discuss their possible functional relevance.

extracellular field potential volume conduction branch point failure axon hillock/initial segment 


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Copyright information

© Kluwer Academic Publishers 1999

Authors and Affiliations

  1. 1.Computation and Neural Systems ProgramCalifornia Institute of TechnologyPasadena

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