Figure 3. Effects of coil orientation on the electric fields.

The spatial patterns of the magnitude of electric fields (| $\overrightarrow{E}$|, top row) and their component orthogonal to the gray matter surface ( ${\text{E}}_{\perp }$, bottom row) are visualized; the color scale is adapted for better visualization. The black arrows indicate different coil orientations, and the maximum value of | $\overrightarrow{E}$| and ${\text{E}}_{\perp }$ (measured in V/m) are given in the bottom left of each figure. For the orthogonal component of electric fields (bottom row), red color indicates current flowing in the direction from superficial to lower cortical layers and blue color represents currents flowing in the opposite direction.