Fig 1.
The stimulation protocol included eight sequences.
In the first seven sequences, 30 trains consisted of four or twenty pulses. The inter-train interval (ITI) was determined as an interval between the last pulse in a train and the first pulse in the next train. The ITIs were 3, 4, 6, 7, 12, and 17 s and an inter-stimulus interval (ISI) was 1 s. In the last sequence, 120 pulses were applied with an ISI of 1 s. When the last sequence was divided into 4-pulse trains, the ITI was equal to ISI and the number of trains was 30. The sequences were applied in a random order except the 120 pulses/train sequence which was always given last.
Fig 2.
Repetition suppression of the motor-evoked potentials.
The effects of the stimulus order and inter-train interval (ITI) on the amplitudes are shown. The amplitudes (mean±standard deviation) are averaged and normalized to the first ones in the train (dashed line). Asterisks mark the amplitudes that differ from the first one (p<0.05) in the train according to the pairwise comparisons using Bonferroni adjustment of p-values for correction of multiple comparisons. A) All 4-pulse sequences. B) ITI 1 s. C) ITI 3 s. D) ITI 4 s. E) ITI 6 s. F) ITI 7 s. G) ITI 12 s. H) ITI 17 s. I) 20-pulse sequence. J) 120 pulses/train at inter-stimulus interval (ISI) of 1 s.
Table 1.
Differences between the first motor-evoked potential amplitudes with different inter-train intervals.