Nanoelectrode Nerve Stimulation Simulator (2D)

Stimulation Parameters

Current amplitude 150 µA

Pulse width 200 µs

Electrode height above axon 0.60 mm

Electrode Position

Live Readouts

Recruitment

Peak voltage

0 mV

Activation radius along axon

0 mm

Current for threshold here (at this pulse width)

— µA

How it works

The nanoelectrode tip is modelled as a point current source in a homogeneous conductive tissue of conductivity σ. In a volume conductor, a point source of current I produces an extracellular voltage field that falls off with distance r as:

V(r) = I / (4πσr)

Every point along the axon sits at its own distance r from the tip, so the field it feels is highest directly under the electrode and fades smoothly outward — visualised here as the glow along the axon and the radial field rings. A segment of axon only fires if the local voltage exceeds its activation threshold, and — exactly as in the 3D nanoelectrode-array engine this simulator pairs with — that threshold itself depends on pulse width through Lapicque's strength-duration law:

V_th(PW) = V_rheobase · (1 + τ_chronaxie / PW)

Shorter pulses need a disproportionately stronger field to trigger a response (rheobase = the threshold at infinitely long pulses; chronaxie ≈ 200 µs, the same myelinated-fibre value used in the 3D array engine). Every point along the axon carries its own randomised rheobase, so the recruited zone grows gradually rather than as an all-or-nothing switch. Wherever threshold is crossed, a real action potential is launched and propagates away from the activation zone in both directions along the axon at a fixed conduction velocity, exactly as a real depolarisation wave would.

Current amplitude — scales the field from the electrode linearly, widening the activated zone.
Pulse width — shorter pulses raise every point's threshold (right side of the strength-duration curve), the same law from the 3D engine.
Electrode height — the perpendicular distance from tip to axon; moving the electrode closer concentrates the field over a narrower stretch of axon (1/r falloff).
Drag along axon — repositions the electrode's contact point horizontally, sliding the activated zone with it.
Current for threshold here — the amplitude at which the axon point directly under the electrode would just reach threshold at the current pulse width, found by inverting the linear field-vs-current relationship.

Firing / action potential Below threshold Nanoelectrode tip