Mc b70

To further evaluate the performance of the predicted E-field maps, we computed the distance between peaks of the predicted and reference E-field magnitude. Similar to TOC, we computed the E-field peak distance (EPD) in both the volume and the surface space, respectively, using the following definition
EPD=‖Peak(EP)−Peak(ER)‖,
where E_P and E_R denote the predicted and reference E-field and Peak() obtains the coordinate of the voxel at the gray matter region or the vertex at brain surface with the maximum magnitude. To reduce the influence of outliers on EPD in the volume space, we took the average value of the E-field magnitude in 3x3x3 neighboring voxels within the gray matter region as magnitude of a voxel to determine the location of the peak value of E-field maps for Magstim-70mm-Fig8 and MagVenture-MC-B70 coils. For the less focal E-field distributions corresponding to the Magstim-70mm-circular coil, the location of the target was determined as the average position of the top 200 voxels with the highest E-field magnitude in the gray-matter region.

In order to determine the right M1 hot-spot, motor-evoked potentials of the left fore-arm muscles were elicited by single TMS pulses delivered with a standard figure-of-eight coil (MC-B70, MagPro Stimulator, MagVenture, Willich, Germany). The coil was held tangentially to the scalp with the handle pointing backward and laterally at an angle of about 45° away from the midline. The coil was positioned over the M1 hand area to elicit motor responses. By moving the coil in 0.5 cm steps anterior, posterior, medial, and lateral to this area, the exact localization of the area which evoked the maximal motor response was determined. This location was marked on the scalp with a pen and used for positioning of the tDCS electrode.

TMS was delivered with a figure-of-eight coil (MC-B70 with outer diameter of each wing 97 mm) connected to a biphasic MagPro X100 system (MagVenture, Skovlunde, DK) over the left motor cortex to elicit motor evoked potentials (MEPs) at the right FDI muscle.^{25 (link)} Resting motor threshold (RMT) and active motor threshold (AMT) were determined according to standard procedures.^{26 (link)}Facilitatory circuits were evaluated by the intracortical facilitation (ICF) and the short-interval intracortical facilitation (SICF) protocols, while inhibitory circuits by SICI, long-interval intracortical inhibition (LICI) and CSP.^{27 (link)}SICI–ICF, SICF and LICI were studied with a paired-pulse model with a conditioning-test design. For all paradigms, the test stimulus (TS) was adjusted to evoke an MEP of 1 mV amplitude. The interstimulus interval (ISI) between TS and conditioning stimulation differed among protocols (see Supplementary Data and Table 1). Fifteen trials were recorded for each ISI and each protocol randomly intermixed with 15 trials of TS alone (0.2 Hz ± 10%). The ratio of the mean amplitude of the conditioned response to that of the TS response (unconditioned response) was calculated for each condition and ISI in each subject.

The left dPMC was localized using a neuronavigation system (LOCALITE, Sankt Augustin, Germany). The target area was pre-defined by Talairach coordinates −29, 5, 47 (x, y, z) corresponding to Brodmann area 6.
To ensure that the target area for stimulation was sufficiently separated from the left M1, the cortical representation of the right first dorsal interosseus (FDI) muscle was localized using single pulse TMS. To this end, a standard figure of eight coil (MC-B70) connected to a MagPro stimulator (Mag Venture, Hückelhoven, Germany) was placed tangentially to the scalp to trigger motor-evoked potentials (MEP). The area evoking the largest motor response was defined as motor hot spot. In two sessions, M1 localization was not possible. The mean distance between M1 hot spot and the PMC target area was 5.11 ± 0.13 cm (sham), 5.08 ± 0.20 cm (anodal) and 4.89 ± 0.21 cm (cathodal). The distance did not differ significantly between sessions (F(2, 30) = 0.456, p = 0.638).

Biphasic TMS pulses were delivered by a figure-of-eight coil, specifically designed to stimulate lower limb motor cortical area (MC-B70, MagVenture), and produced by a MagPro R30 Stimulator (MagVenture). During the whole experiment, pulses were biphasic with the current flowing in the coil in an anterior-posterior/posterior-anterior direction. The coil was held so that the figure-of-eight was oriented perpendicularly to the interhemispheric fissure, with the center of the coil placed over the left hemisphere a few centimeters lateral of the vertex. The position was adjusted in order to elicit the biggest MEP possible in VL (around 40% Mmax amplitude). The position of the coil was drawn on a swimming cap to ensure an identical position of the coil throughout the whole experiment. TMS intensity was set to elicit the biggest MEP possible during VA_TMS measurements (90–100% maximal stimulator output (MSO), identical intensity during the whole experiment) and a second intensity was used to produce MEPs equal to 10–20% Mmax amplitude during 10% MVC. The intensity was then kept constant during the whole experiment.