Extended Data Fig. 7 |. Action potentials triggered by SCS pulses are not stimulation artifacts in humans with paralysis.

a, For the experiments with STIM01, we recorded the stimulation artifact with a surface EMG placed on the dorsal. We defined the stimulation timestamps through EMG threshold-crossing above 0.05 mV (dashed line). b, For the experiments with the stroke participants, traces were recorded from high-density EMG: in gray showing the presence of stimulation artifacts and in black after removing the stimulation artifacts (showing an example of SCS03, 60 Hz SCS). c, For the experiments with the stroke participants, stimulation artifact removal was achieved by applying a series of notch filters at harmonics of SCS frequency to remove peaks in the Fast Fourier transform (shown in gray) of the bandpass filtered signal (see methods). d, Examples of the probability distribution of the time between the most recent SCS pulse and an action potential for each motor unit (MU; 40 Hz SCS, 1 ms bin) using surface EMG in STIM01. If the action potentials detected by the acquisition software were stimulation artifacts, they would be aligned to the SCS pulse, thereby showing histograms with a high peak at time 0. Given that the times from the most recent SCS pulse and the action potentials are distributed with a mean between 12.5 and 25 ms, the action potential detected can not be artifacts of SCS. e, Same as d using the high-density EMG in the stroke participants (SCS03, SCS04; 60 Hz SCS, 1 ms bin).