A quantitative physical model of the TMS-induced discharge artifacts in EEG
Fig 3
The simulated voltage difference between a reference and the recording electrode.
The initial voltage distribution at each electrode is a Gaussian of the form g(σ, x + μ) convolved with the box function B, where g(t, x) is the voltage impulse-response function of our model, and B(x) equals 1/πb2 for |x| ≤ b. The parameters for the reference electrode are fixed to σR = 0.5 and μR = 0. The choice of μR implies that the voltage depends only on the length |μ| of μ and not on its direction. The electrode radius was b = 2. (A, B) Effect of varying σ from 0 to 1 in steps of 0.05 (inset: close-up for σ for half step size). (D, E) Effect of varying |μ| from 0 to 2 in steps of 0.1 (inset: close-up for |μ| for half step size). (C, F) The plot on a log-log scale demonstrates the power law. In comparison to data, we note the asymmetry of positive and negative voltage shapes (compare to Figs 4A, 7A and 11A) and the emergence a local extremum near 0 in some traces (compare to Fig 4A). (G-L) The simulated voltage difference for electrodes approximated by points (b = 0).