Stimulating deep cortical structures with the batwing coil: How to determine the intensity for transcranial magnetic stimulation using coil-cortex distance

► The batwing coil is efficient to stimulate deeper cortical regions. ► The effect of coil-cortex distance on TMS is examined for the batwing coil. ► Motor threshold increases linearly with distance between the coil and scalp. ► A millimeter increment demands an extra 1.4% power to induce an equivalent effect.