Typical Electrode Configuration Analysis for Temporally Interfering Deep Brain Stimulation

Temporally interfering (TI) deep brain stimulation is an exciting neuromodulation technique, which can noninvasively drive neural activity in deep brain region. In this paper, two typical electrode configurations, opposite and cross, are modeled and, along different directions, the resulting distributions of envelope modulation amplitude are analyzed. In the 3D model, the two pairs of electrode are set in the x-y plane. First, one-layer and four-layer brain tissue structures are tested. Compared to one-layer, for four-layer brain structure, tissue of cerebrospinal fluid with higher conductivity shunts current back to the return electrode and as a result the location of maximum envelope modulation amplitude will be closer to the scalp. Then, taking brain structure into consideration, the models of the two electrode configurations are implemented with four-layer brain tissue distribution. Results demonstrate that, for opposite electrode configuration, along y direction, envelope modulation has a focused amplitude distribution, almost ellipse, in the deep of brain, which is effective for deep brain stimulation with target. And for cross electrode configuration, the relatively focused amplitude distribution, almost clover, is produced along x+y direction, which is suitable for wide-range area stimulation.