Individualized Alpha-tACS for Modulating Pain Perception and Neural Oscillations: A Sham-Controlled Study in Healthy Participants

Pain encompasses sensory, affective, and cognitive dimensions, with neural oscillations increasingly recognized as key mechanisms in their integration. However, the underlying processes remain inadequately understood. Transcranial alternating current stimulation (tACS) offers a promising tool for modulating these oscillations, yet the widespread reliance on one-size-fits-all tACS protocols with fixed frequencies has led to limited and contradictory findings on its efficacy in pain treatment. In this study, we employed individualized tACS at individual peak alpha frequency (IAF) over the primary motor cortex (M1) contralateral to the dominant arm of 38 healthy participants, in a within-subject, sham-controlled design, to investigate its effects on pain perception and neural oscillations. Sustained and periodic 0.2 Hz thermonociceptive stimuli were applied to the dominant forearm before and after tACS. We measured participants pain perception and heat pain thresholds (HPT) before and after tACS stimulation. Scalp electroencephalography (EEG) measurements were used to measure neural activity during thermonociceptive stimuli. To calculate IAF, we used a discriminative approach based on independent component analysis (ICA) to separate sensorimotor related IAF (SM-IAF). The results revealed an overall increase in pain perception and a decrease in HPT in both sham and active conditions, with no significant interactions between conditions. However, a trend toward reduced sensitization post-tACS was observed. Exploratory analyses indicated a significant tACS effect on HPT in women. Furthermore, a significant correlation was found between SM-IAF and HPT. These findings provide a novel perspective on advancing individualized neuromodulation approaches for pain and neurobiological disorders.