Topography and timing of activity in right inferior frontal cortex and anterior insula for stopping movement

摘要

Optimization of transcranial temporal interference stimulation for targeted modulation of deep brain structures Temporal interference (TI) stimulation was recently proposed to allow for the stimulation of deep brain structures with unwanted stimulation of neocortical regions being avoided, which showed promising results in a small animal in-vivo study. In case of the human brain modulation, it has been known that TI current pat- terns are largely affected by the complex structures of the human head, and thus it is hard to deliver TI current to specific deep brain region, especially transcranial TI stimulation is employed. For the first time, we optimized scalp electrode configurations and injection currents that can deliver maximum TI stimulation currents to a specific deep brain region, i.e., right hippocampus in this study, considering each individual’s realistic anatomical head structures. Three realistic finite element (FE) head mod- els with 19 electrodes being attached according to 10-20 system were employed for the optimization of TI stimulation. To generate TI current patterns, two pairs of scalp electrodes were selected, which flow two sinusoidally alternating currents with a small frequency difference. For each of all possible combinations of elec- trode pairs, optimal injection currents delivering the maximal TI currents to right hippocampus were determined. The distribution of optimized TI currents was then compared with that of unopti- mized TI currents and conventional single frequency AC stimulation result. Optimization of TI stimulation parameters allowed for more accurate and focalized stimulation of the deep brain target while effectively reducing the unwanted stimulation of neocor- tical regions. Inconsistency of the optimal stimulation conditions suggests that customized stimulation taking individual anatomical difference into account is necessary for more effective transcranial TI stimulation. Optimization of transcranial TI stimulation based on the numerical field analysis is expected to enhance the over- all effectiveness of noninvasive stimulation of human deep brain structures.