Figure 2.

Electrode field model of study montage (coronal slice 133, sagittal slice 93, axial slice 77). The bipolar electrode montage for targeting the left dorsal anterior cingulate cortex (dACC) was adapted from our prior work [38]. Electrodes were 5 × 7 cm carbon rubber electrodes enclosed in sponge pockets saturated with normal (0.9% NaCl) saline, held comfortably in place on the scalp with adjustable rubber straps and connected to a battery-powered, microprocessor-controlled, single-channel stimulator (DC-STIMULATOR PLUS, NeuroConn GmbH, Munich, Germany). The cathodal electrode was placed at FC₁ on the 10–20 electroencephalography system, and the anodal return electrode was placed over the contralateral (right) mastoid. Although this montage was empirically informed, for additional rigor, we performed post hoc confirmatory computer modeling to assess the montage’s ability to engage the dACC target. This modeling was performed with tDCS-Explore, v. 4.0 (Soterix Medical, New York, NY, USA), which produced the color-coded heat maps shown here for qualitative assessment. The white circles indicate the approximate location of the left dACC. The modeling demonstrated an electric field strength of >0.5 V/m at the left dACC. For a full color figure, please see the online version of this article.