Figure 2. Effects of LIHI on SICI in one representative subject.

Each trace represents averaged MEPs from 10 trials. A, the test stimulus (TS) alone. TS was set to produce MEP of about 1 mV (state 2A in Table 1). B, short-interval intracortical inhibition (SICI) elicited by a subthreshold conditioning stimulus (CS₂) that precedes the TS1mV by 2 ms (state 2B). C, TS1mV_CCS40 alone. TS was adjusted to produce test MEP of 1 mV in the presence of contralateral cortical stimulation (CCS₄₀) preceding the TS by 40 ms (state 2E). D, long interval interhemispheric inhibition (LIHI) induced by CCS₄₀ preceding the TS1mV_CCS40 by 40 ms (state 2H). The test MEP amplitude matched was similar to the test MEP amplitude in condition 2A. E, SICI elicited by a subthreshold conditioning stimulus (CS₂) that precedes the TS1mV_CCS40 by 2 ms (state 2F). F, combined LIHI and SICI (CCS₄₀–CS₂–TS1mV_CCS40 combination, condition 2I). The inhibition is greater compared to D and E demonstrating that there is an additive effect of the two inhibitory pulses.