Simulation of TES focality using common and novel electrode configurations

A computational study of transcranial electrical stimulation (TES) is presented using a concentric spheres human head model. Induced electric field distributions are calculated in the model using the finite element method. We simulated a range of electrode configuration geometries including: 1) stimulation with remote scalp electrodes, 2) adjacent electrodes, 3) belt electrodes, and two novel electrode designs: 4) tripolar, and 5) concentric ring. The overall goal of our study is to compute the induced electric field during TES with different electrode geometries in order to determine the optimum configurations to target specific regions of the brain. The "remote bipolar" is comparable with currently commonly used TES configurations and resulted in diffuse activation. The novel "tripolar" electrode required the lowest amount of injected current density. The use of the novel "concentric ring" electrode resulted in optimal focality, at the expense of increased total injected current.