Fig. 1.

Experimental procedures.

(A) The protocol of quadripulse stimulation (QPS). The inter-stimulus interval (ISI) used in this study was 5 ms.

(B) Timelines of the experiments. Patients were studied in two separate sessions; “PD with L-DOPA” and “PD without L-DOPA ” states. In “PD without L-DOPA”, patients did not take L-DOPA for at least 16 h, and in “PD with L-DOPA”, they took L-DOPA 60 min before the study. For each session, we assessed MDS-UPDRS, the motor thresholds (RMT/AMT) and 20 baseline motor evoked potentials (MEPs). Immediately after the baseline MEP recordings, we delivered QPS5 for 30 min. After QPS, 20 MEPs were measured every 5 min up to 30 min (5, 10, 15, 20, 25, and 30 min) using the same intensity as the baseline recording. HC were studied only once by the same protocol as that used for PD patients.