PyFibers: An open-source NEURON-Python package to simulate responses of model nerve fibers to electrical stimulation
Fig 10
Replication of published responses for five of the seven unmyelinated fiber models in PyFibers.
Data from [10] were downloaded from the publicly available repository [49]. All fibers were 5 mm long with 600 sections (i.e., each section was 8.33 μm long and comprised a single segment), and except for panel A, all data are for 1 μm diameter fibers. As in [10], we removed all nonlinear mechanisms from the end nodes, except in the Tigerholm model. Stimulation was an intracellular anodic rectangular pulse beginning at t = 1 ms with a pulse width of 0.1 ms, except for panel C where we evaluated different pulse widths and panel D where we evaluated pairs of pulses (0.1 ms duration each). A) Conduction velocity calculated using action potential times from fiber(0.25) to fiber(0.75) after intracellular stimulation at fiber[1]. Each dot represents one fiber diameter (0.5, 0.75, 1, 1.25, 1.5). B) Action potential time course recorded at the center node fiber(0.5) after an intracellular stimulus at fiber[1]. C) Strength-duration curves calculated using intracellular stimulation at fiber(0.5). D) Recovery cycle for intracellular stimulation delivered at the center node (fiber(0.5)). We first determined activation threshold (Ith) for a single pulse with 0.1 ms duration. We then simulated a pair of 0.1 ms duration pulses: one at t1 = 1 ms and 1.5 * Ith, and a second 0.1 at t2 = 1 ms + inter-stimulus interval (ISI); we determined the activation threshold for the second pulse and its difference relative to Ith. E) Action potential duration calculated by taking the earliest and latest times where Vm > baseline Vm + 0.1*(peak Vm – baseline Vm).