Fig. 3: Surrogate model (S-MF) predicts a range of nonlinear responses to stimulation.
From: Highly efficient modeling and optimization of neural fiber responses to electrical stimulation
All tests were conducted in nerves other than those used to train S-MF. a S-MF (dashed orange) reproduced NEURON (solid blue) responses to a 0.75 ms monopolar cathodic extracellular pulse delivered to pig vagus nerve (Supplementary Note 1 P3) with the ImThera cuff across different stimulation amplitudes (rows). Columns indicate the timepoints during each simulation at which transmembrane potential (Vm) is plotted. b S-MF (orange) reproduces the NEURON (blue) responses to kilohertz frequency extracellular stimulation with intrinsic activity. Fibers were simulated in a pig vagus nerve (Supplementary Note 1 P2) instrumented with the ImThera cuff. Intrinsic activity was generated at 100 Hz with intracellular current pulses at one end of each fiber and action potentials (APs) were counted at the opposite end. Rows correspond to the frequency of the extracellular sinusoidal signal and columns correspond to fiber diameters. Solid lines are the mean number of APs recorded across 7 sampled fascicles, and shaded regions are 95% confidence intervals. c S-MF (dashed orange) reproduces NEURON (solid blue) AP interactions. Action potentials initiated by intracellular current pulses (2 nA, 0.1 ms) at opposite ends of a fiber propagate bidirectionally at appropriate speeds and mutually annihilate when they meet. Rows correspond to different fiber diameters, and columns correspond to the timepoints at which Vm along the nerve is plotted. d S-MF (orange) reproduces state-dependent fiber responses to extracellular stimulation predicted by NEURON (blue). Fibers were placed in a human nerve (Supplementary Note 1 H2) instrumented with the helical cuff. Rows correspond to mean intrinsic firing rates, and columns correspond to fiber diameters. Lines correspond to mean SPIKE synchronization64 (a quantity between 0 and 1 that measures the proportion of coincident spikes between two spike trains) across all modeled fibers of a given diameter and mean intrinsic firing rate (n = 35, 7 fiber locations × 5 distinct patterns of intrinsic firing) at a given amplitude and frequency (line style) of extracellular stimulation (0.1 ms symmetric biphasic rectangular pulses). Shaded regions correspond to 95% confidence intervals. Source data are provided as a Source Data file.
