Effects Evoked in an Axon by the Activity of a Contiguous One

Ephaptic coupling of myelinated nerve fibers

“…Thus Equation (1) is merely Ohm's law, relating the voltage difference between two adjacent nodes of the current flowing between them times the sum of the inside and outside resistances: R i and R o . Equation (2) says that the current flowing into the nth node from the (n − 1)th node (I n−1 ) minus the current flowing out of it to the (n+1)th node (I n ) is equal to the following two components of transverse (inside to outside) current leaving the node: (i) the capacitive current, C dV n /dt, and (ii) the ionic current, I ion,n , comprising both sodium and potassium components [17].…”

“…In the parallel nerve interactions observed experimentally in the early 1940s by Katz and Schmitt [22] and by Arvanitaki [2], the mechanism of impulse coupling was through an electrical linking of the external return currents of nearby impulses. An analytic formulation of such an interaction between nonmyelinated impulses was presented by Markin in 1970 [29,30,40] and experimentally verified by Ramón and Moore in 1978 [35].…”

“…In this paper, we consider the dynamics of impulses on myelinated nerve fibers that are parallel and relatively close together (as in vertebrate motor nerves) so the electrodynamics on one fiber can influence those on others and vice versa. Such parallel fiber interactions have been known to electrophysiologists since the 1940s [2,22], and are termed ephaptic from a Greek word meaning "to touch" [21].…”

Ephaptic transmission between single nerve fibres in the spinal nerve roots of dystrophic mice.

“…Since shortly after the development of the local circuit theory of propagation of the nerve impulse (Hodgkin, 1937a, b), it has been recognized that currents flowing external to active fibres can influence the excitability of neighbouring fibres (Katz & Schmitt, 1940;Arvanitaki, 1940Arvanitaki, , 1942. The current flowing external to an active fibre can flow either through extracellular space or through adjacent fibres; any increase in the resistance of extracellular space will divert current into adjacent fibres and will thus enhance the influence of an active fibre on the excitability of its neighbours (Katz & Schmitt, 1940;Arvanitaki, 1940Arvanitaki, , 1942Ramon & Moore, 1978).…”

Open questions on the mechanisms of neuromodulation with applied and endogenous electric fields

“…An ephapse "Gr: touching across" was originally coined to describe how two axons placed close together in mineral oil, which has a higher resistance than saline, transmit an action potential at what can be considered an artificial synapse (Katz and Schmitt, 1940;Arvanitaki, 1942). This finding led Sir John Eccles to propose the Golgi cell theory of inhibition in which he speculated that ephapses could mediate inhibitory neurotransmission (Brooks and Eccles, 1947).…”