Figure 7. Comparison of SICI and ICF assessed in the cortical representation of masseter (MM) and of first dorsal interosseus (FDI) muscles.

The same TMS paired pulse protocol was applied to the left hemisphere of 12 subjects and EMG responses were recorded from contralateral muscles, both activated at 10% MVC. TS intensity was adjusted to elicit a test MEP of 0.5 mV peak to peak and CS intensity was equal to 70% of AMT. Two coil orientations were used to induce motor responses in the active FDI: coil handle pointing backwards and rotated 30 deg from the midline (FDI_30deg, bright grey) and coil handle pointing forwards and rotated 120 deg from the midline (FDI_120deg, dark grey). This last coil orientation was also used to induce masseter MEPs (MM_120deg, black line). Ordinate indicates mean conditioned MEP amplitude expressed as a percentage of the test MEP amplitude, taken as 100% (dotted horizontal line) and abscissa reports ISIs. Error bars represent standard error of the mean. Note that SICI observed at the 2 and 3 ms ISI is not significantly different in the two muscles. On the contrary, MEP inhibition observed in MM at 10 and 15 ms ISI is significantly different (*P < 0.05; **P < 0.01) from that observed in FDI muscle with both coil orientations used. Moreover, a significant difference between FDI_30deg and FDI_120deg at 10 ms ISI was observed (•P < 0.05).