In-vivo phase-dependent enhancement and suppression of brain oscillations by transcranial alternating current stimulation (tACS)

Published: 22 May 2023| Version 2 | DOI: 10.17632/chvcccgbxm.2
David Haslacher


Transcranial alternating current stimulation (tACS) can influence human perception and behavior, with recent evidence also suggesting its potential impact in a clinical setting, but its underlying mechanisms are poorly understood. Behavioral and indirect physiological evidence indicates that phase-dependent constructive and destructive interference between the applied electric field and ongoing brain oscillations may play an important role, but direct in-vivo validation was infeasible because stimulation artifacts impeded such assessment. Here, we overcame this limitation and provide direct evidence for phase-dependent enhancement and suppression of ongoing brain oscillations during amplitude-modulated tACS (AM-tACS). We found that AM-tACS enhanced and suppressed targeted brain oscillations by 11.7 ± 5.14% and 10.1 ± 4.07% respectively. These results not only provide direct evidence for constructive and destructive interference as a key mechanism of AM-tACS but suggest superiority of phase-locked (closed-loop) AM-tACS over conventional (open-loop) AM-tACS to purposefully enhance or suppress brain oscillations.