Figure 1.
TMS experiment procedure. A, Random dot motion task: after a fixation cross and a period of random motion, coherent motion (here: upward, coherence 70%) was displayed for 2000 ms or until response (the same task was used in the EEG experiment). B, Response setup in TMS experiment: participants held one button (up) between their thumb and index finger (pinch) and one in the palm of their hand (down), attached to a cylinder (grasp); EMG electrodes were placed on the ADM and FDI. C, Example EMG traces from a single trial (here, a hard speed trial, where the responding muscle is the FDI and the nonresponding muscle is the ADM). D, To create model predictions which are comparable to MEP data, accumulation values from both the correct accumulator (corresponding to the responding muscle) and the incorrect accumulator (corresponding to the nonresponding muscle) are sampled at simulated TMS times. E, Illustrative real MEP amplitudes (from the speed/easy condition) collated from all participants. F, MEPs and simulations (data not shown) are then z-scored per muscle, participant, and session (note that latencies were normalized by the median, not maximum, EMG RT for each participant). G, Real and simulated continuous signals can be created for each muscle (responding, nonresponding), using a Gaussian smoothing kernel. H, However, to remove nonspecific processes, the same smoothing is applied to the difference between simultaneously recorded MEPs (responding minus nonresponding).