Figure 3.

(a). Rotational field TMS coils array: two orthogonal coils one on top of the other. (b). With only the lower coil operated, electric field is induced along the anterior–posterior axis; thus, only neurons aligned along this axis will be activated (indicated in red). The color code indicates the field intensity (red is highest). (c). With only the upper coil operated, an electric field is induced along the lateral–medial axis, thus only neurons aligned along this axis will be activated (indicated in red). (d). With both coils operating simultaneously, electric field is induced at 45° to the lateral–medial axis; thus, only neurons aligned along this orientation will be activated (indicated in red).