Can Personalized Transcranial Alternating Current Stimulation (tACS) Modulate Pain Perception and Pain-related Oscillations?

Ongoing neural oscillatory activity was suggested to play a crucial role in the experience of pain. This study aims to determine whether there is a causal link between neural oscillations and pain perception, and whether transcranial alternating current stimulation (tACS) can modulate it. We employed tACS to modulate ongoing oscillatory activities measured using scalp electroencephalography (EEG), and investigated how this affects pain perception. To induce pain, we used sustained periodic 0.2 Hz thermonociceptive stimuli. tACS targeted M1, contralateral to the side of the thermonociceptive stimulation. The frequency of stimulation was set to the individual peak alpha frequency (PAF). A sham stimulation was used as a control condition. Data was acquired from 38 healthy volunteers. Statistical tests were performed using linear mixed models using “time” (pre vs post) and “condition” (active vs sham) as factors. In the “post” phase, we observed a significant reduction in heat pain thresholds (HPTs) and an increase in both intensity and pain perception compared to the “pre” phase, regardless of condition (p<0.01). The HPT reduction was greater for the sham condition compared to the active condition, although not significantly. Furthermore, both local and global average PAF values decreased significantly (p<0.01) in the two conditions, with a slightly greater reduction in the sham condition. The reduction of HPTs, along with the increases in the intensity of perception and pain over time, suggest that participants may have become sensitized to the thermonociceptive stimulation. Although the current study does not show a significant effect of tACS on perception, the small but consistent trend of lower pain perception and smaller PAF changes in the active condition compared to sham may be interpreted as a reduced sensitization following tACS, highlighting the potential for further exploration of tACS effects on pain with enhanced designs and strategies.