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. 2011 Oct 26;31(43):15376–15383. doi: 10.1523/JNEUROSCI.2271-11.2011

Figure 1.

Figure 1.

Methodology and experimental design. A, Multicoil focal TMS. Near-simultaneous bilateral M1 stimulation (ISI = 0.8 ms; left M1 always before right M1, stimulus intensities adjusted to elicit MEP of 1 mV peak-to-peak amplitude in the contralateral FDI) was delivered through 50 mm diameter figure-of-eight coils. During paired associative stimulation (PAS1–3, see C), SMA-proper was stimulated time-locked to bilateral M1 stimulation using a small 25 mm figure-of-eight coil (stimulus intensity set to 140% of AMT as determined over left M1). Directions of induced currents in the brain were as indicated by the white arrows. For further details, see Materials and Methods. B, Sagittal view at x = −4 in Talairach stereotaxic space (Talairach and Tournoux, 1988) of the mean anatomical image indicating SMA-proper stimulation sites (center of stimulating coil, red circles) and pre-SMA stimulation sites (yellow circles) during PAS1–3 in those subjects (n = 7 for SMA-proper, n = 4 for pre-SMA) in whom MR-navigation was used to verify stimulation topography. Circles are artificially stacked along the z-axis to provide visibility of all individual stimulation sites. The vertical plane through the anterior commissure (white line, y = 0) and the perpendicular anterior–posterior commissure plane (black line) are indicated. Mean coordinates for the SMA-proper stimulation sites were y = −1.3 ± 0.6 (Talairach and Tournoux, 1988) and 3.3 ± 0.2 cm anterior to Cz, mean coordinates for the pre-SMA stimulation sites were y = 23.7 ± 3.3 (Talairach and Tournoux, 1988) and 6.2 ± 3.2 cm anterior to Cz. C, General time line of Experiment 1–7, always consisting of nine blocks of 50 trials each (Pre1–3, PAS1–3, Post1–3). Pre1–3 measure M1 excitability at baseline, PAS1–3 apply paired associative stimulation of SMA and M1, and Post1–3 assess any lasting effects on M1 excitability after PAS1–3. Variations of the stimulation procedures in Experiments 1–7 are detailed in Materials and Methods. EXP, Experiment; Bi-M1, bilateral M1 stimulation; L-M1, left M1 stimulation; SMA, SMA-proper.