(A) Diagram showing the STDP protocol where corticospinal volleys evoked by TMS over the hand representation of the primary motor cortex were timed to arrive at corticospinal-motoneuronal synapses of the FDI muscle 2 ms before antidromic potentials elicited in motoneurons by peripheral nerve stimulation (PNS) of the ulnar nerve. (B) Raw traces showing a MEP, an F-wave, and the M-max from a representative subject recorded from the FDI muscle used to calculate central and peripheral conduction time to estimate the arrival of pre- and post-synaptic volleys at the corticospinal-motoneuronal synapse. (C) Raw MEP traces from a representative participant showing MEPs at baseline (grey traces) and immediately after AIH (green trace), STDP combined with sham AIH (STDPsham AIH, blue trace) and STDP combined with AIH (STDPAIH, black trace). Each trace is the average of 20 trials. (D) Group data (n = 11) showing the effect of AIH (green circles), STDPsham AIH (blue circles), and STDPAIH (black circles). The abscissa shows the time of measurements (baseline, immediately after (0–15), 30–45, and 60–75 min after each protocol) and the ordinate shows the MEP amplitude (expressed as a % of Baseline). (E) Graph shows box-plots group normalized MEP data at baseline (dotted line) and after the AIH and sham AIH protocols from all time points averaged. The abscissa shows the protocol tested (AIH, STDPsham AIH and STDPAIH) and the ordinate shows the MEP amplitude (expressed as a % of Baseline). Whiskers illustrate 5th and 95th percentiles and dots represent minimal and maximal values. (F) Correlation analysis between increases in MEP amplitude after STDPAIH and STDPsham AIH. Error bars indicate SDs. *p<0.05, STDPAIH different than AIH and STDPsham, θ p<0.05, STDPAIH different than AIH, #p<0.001, comparison with the baseline.