Reliable assessment of evoked brain responses targeted by transcranial alternating current stimulation (tACS) using optically pumped magnetometers (OPMs)

Abstract Background: Millisecond-precise targeting of ongoing brain oscillations with electric stimulation is an important goal to uncover brain-behavior relationships or treat neurological and psychiatric disorders related abnormal activity. The main challenge implement such a paradigm reliably assess activity despite artifacts that often exceed physiological signals by many orders magnitude. Recently, we have introduced artifact source separation (SASS) recover using electroencephalography (EEG) during transcranial alternating current (tACS). Due volume conduction susceptibility muscle artifacts, EEG remains limited establish millisecond- millimeter-precise closed-loop adaptive stimulation. Here tested the feasibility optically pumped magnetometers (OPMs) visually evoked responses targeted tACS. Methods: Visually-evoked flickering visual stimuli random intertrial intervals were assessed 16 OPM sensors (FieldLine Inc., Boulder, USA) fitted into custom 3D-printed array. tACS pads placed over occipital regions applied at phase angles relative stimuli. Brain-evoked recovered SASS. Results: We found (1) tACS-related remain well within dynamic range sensors, (2) could be successfully recovered, allowing for real-time paradigms. Conclusion: combining OPMs feasible may pave way millimeter-precised neuromodulation. Research Category Technology Methods Translational Research: 8. Transcranial Alternating Current Stimulation (tACS) Keywords: Source, Artifact, MEG, Optically magnetometer