Targeting Impaired Alpha Oscillations in Chronic Pain with Transcranial Alternating Current Stimulation

Alpha oscillations are a fundamental human brain rhythm that modulates engagement of cortical circuits with afferent input. We hypothesized that chronic low back pain is reflected in a pathological hyperexcitability of sensory-motor circuits that can be detected by EEG as a downregulation of alpha oscillations. We further hypothesized that tACS at 10 Hz (in the alpha frequency) can be used to restore these impaired alpha oscillations and thereby reduce the pain symptoms. To test these hypotheses, we performed a pilot double-blind placebo-controlled study in people with chronic low back pain. We found that pain symptoms correlated with impairment of alpha oscillations at baseline. Importantly, alpha-tACS enhanced and restored these alpha oscillations, which correlated with improved pain ratings. More studies are urgently needed to replicate and expand on our findings. Next-generation tACS strategies that use individualized stimulation waveforms and real-time feedback may further increase efficacy of this approach. Studies of multiday stimulation paradigms as we have recently used in clinical trials of tACS for the treatment of depression and schizophrenia represent a further, highly promising avenue towards targeted non-pharmacological treatments for chronic pain by modulating brain rhythms.