Extended Data Fig. 5: Modulation of EEG activity during volitional contraction of leg muscles without and with EES.

a, Recordings of EEG activity while participants were asked to produce an isometric torque at the knee joint without and with continuous EES targeting motor neuron pools innervating knee extensors, as shown in b. b, Superimposed EEG responses (n = 40 repetitions) and temporal changes in the topography of average activity over the cortical surface after the onset of EES, as indicated above each map. The onset was calculated from the onset of EMG responses in the targeted vastus lateralis muscle (insets). The stimulation elicited a robust event-related response over the left sensorimotor cortex with a latency of 90 ± 40 ms for P1 and P3, and of 170 ± 40 ms for P2 (full range of the peaks and middle of this range indicated). c, Average normalized time–frequency plots (n = 40 trials) showing ERD and ERS over the Cz electrode (central top electrode) for each individual during the voluntary activation of knee extensor muscles without and with EES. Schematic drawings (left) indicate the motor scores of the tested legs, including the targeted muscles (*), at the time of enrolment in the study. Both legs were tested in P1 owing to his asymmetric deficits. d, Normalized average power (mean ± s.e.m.) of the β-band over the Cz electrode during ERS from 0 to 500 ms after termination of contraction without and with continuous EES (n = 40 repetitions for each condition, individual data points shown except for outliers more than 3 median absolute deviations away from the median). ***P < 0.001 (permutation tests, see Methods).