Test-Retest Reliability of Homeostatic Plasticity in the Human Primary Motor Cortex

Figure 1

Experimental protocol for days 0, 2, 7, and 14. The corticomotor excitability was assessed at the beginning of each test session using 15 motor-evoked potentials (MEPs) recorded at 120% of resting motor threshold. To ensure a consistent level of baseline corticomotor excitability across subjects prior to the induction of plasticity, further 15 MEPs were recorded at an intensity sufficient to elicit an average MEP of 1 mV peak-to-peak amplitude (S_1mV) immediately before the first block of 7 min anodal transcranial direct current stimulation (tDCS). This intensity was kept consistent for the remainder of the test session. Plasticity was induced using a 7 min block of anodal tDCS, followed by a second 5 min block of anodal tDCS, separated by a 3 min rest period. Fifteen MEPs were recorded at between the two blocks of anodal tDCS, and at 0 min, 10 min, and 20 min follow-ups.