Abstract
Cortical traveling waves are a neural oscillation pattern indicating the existence of a network between distinct cortical regions. It is characterized by a gradual phase shift of neural oscillations across these spatially separated regions. Previous research showed that it is possible to generate an electric field in the form of a traveling wave inside the brain. It does so by using multi-channel transcranial alternating current stimulation (tACS) with a phase difference across channels. However, optimization algorithms and experimental validation for traveling wave tACS (twtACS) are still lacking. In this study, we suggest a novel computational method for phase optimization to create a traveling wave using multi-channel tACS. Moreover, we conducted invasive measurements in surgical epilepsy patients (approved by UMN IRB) to validate the accuracy of the phase optimization. Our simulation used a realistic finite element head model with three electrodes attached on Fpz, neck, and left tragus. Then, we employed a complex least square method to optimize each electrode’s phase and amplitude to deliver an electric field with the desired phase difference across the targeted region (left temporal lobe in this study). Lastly, we applied the optimized tACS electrode conditions to the human participant and recorded the electric potential from ECoG electrodes attached on the left temporal lobe. Our simulation results confirmed that our approach enables us to form the desired phase difference in the target region. Additionally, the simulated results and measured results via the human experiments were in good agreement. In conclusion, we demonstrated the feasibility of our approach for phase optimization, facilitating the generation of a traveling wave with a desired phase difference across cortical regions.