Transcranial alternating current stimulation not enough to modulate pain

Modulating brain oscillations through transcranial alternating current stimulation (tACS) seems to be ineffective at modulating experimental pain, autonomic response, or electroencephalography (EEG) oscillations, a recent study has found.

Twenty-nine healthy adults participated in the study and underwent six experimental sessions where they were subjected to a tonic heat pain paradigm. TACS was delivered concurrently with the experimental pain, at either alpha or gamma frequencies, or as a sham control. Pain ratings and autonomic responses were measured as study outcomes.

Across 8 minutes of current stimulation, average pain intensity showed no significant differences between alpha vs gamma tACS frequencies. Notably, neither tACS frequency elicited significant pain reductions relative to the sham control, suggesting that the active intervention was insufficient to modulate pain.

Moreover, tACS continued to show no modulatory effect when stratifying analysis according to different time points or intensity of applied pain (low, medium, or high temperature).

Similarly, tACS exerted no significant impact on pain-related modulated activity or brain EEG activity, even when considering individual responsiveness of the participants to tACS or peak frequencies applied.

“Our findings do not provide evidence that tACS can modulate tonic experimental pain in healthy human participants using the current stimulation protocol,” the researchers said.

“Thus, future studies investigating analgesic effects of tACS should aim to optimize the experimental setup,” they added. These could include individualized tACS parameters, guided by individual patient anatomy scans.