Planar figure-8 coils for ultra-focal and directional micromagnetic brain stimulation.

Recently, white-matter fiber tract pathways carrying neural signals through the brain were shown to follow curved, orthogonal grids. This study focuses on how these white-matter fibers may be selectively excited using micromagnetic stimulation (μMS), a new type of neuronal stimulation, which generates microscopic eddy currents capable of directionally activating neurons. One of the most remarkable properties of this novel type of stimulation is that the μMS fields provide unique directional activation of neuronal elements not seen with traditional electrical stimulation. An initial prototype built with SU-8 based photolithography technology shows that the structure can be fabricated. The coil design was optimized through electrical resistance calculations and electric field simulations to elicit the brain's maximal focal and directional neural responses.