Fig. 2.

Buildup of an excitatory cortical state through high-frequency rTMS (nine different experiments). (A) Initial TMS pulses induced strong suppression followed by rebound of small amplitude in the case of single-pulse stimulation (green). Contrastingly, in the case of 10 Hz (red) each consecutive TMS pulse gave rise to a stepwise increase in cortical activity. Arrows mark TMS pulse time (first red arrow is covered by the green). Color shadings depict SEM. When calculated from the suppressive baseline, amplitudes of activity following 10 Hz TMS were in the same range (right bar in B) and highly correlated with visually evoked responses (r = 0.81, pairwise comparisons). Note that for low-frequency stimulation, the first-pulse excitatory peak appeared less pronounced than that for 10 Hz, because its onset was scattered across experiments, possibly reflecting reduced excitability. (B) TMS-induced amplitudes of activity during early phase (white bar, mean across five time frames with lowest responses) and late phase (gray bar, mean between 500 ms and 800 ms; compare gray area in A) compared with visually evoked responses (black contour). Error bars depict SEM. (C) Spontaneous activity after 10 Hz rTMS (red) revealed monotonous increase (8 × 10⁻⁴ units/s, dashed line shows linear regression) not present after low-frequency stimulation (green).