Electric field characteristics of low-field synchronized transcranial magnetic stimulation (sTMS)

Low-field synchronized trancranial magnetic stimulation (sTMS) was hypothesized to have significant therapeutic effects in patients with major depressive disorder by entrainment of neural oscillations. The sTMS device is comprised of neodymium magnets mounted over multiple brain regions and set to rotate at the patients alpha frequency. We characterized the electric field strength and distribution of sTMS using the finite element method. We found that the maximum induced electric field strength on the surfaces of the head and cortex are approximately 0.06Vm^-1 and 0.02Vm^-1, respectively. These field strengths are an order of magnitude lower than that delivered by transcranial current stimulation.