PainRelief.com Interview with:
Markus Ploner MD
Professor of Human Pain Research
Department of Neurology
Technische Universität München
PainRelief.com: What is the background for this study?
Response: Recent studies in humans and animals have revealed that pain is associated with rhythmic brain activity termed neural oscillations. In particular, changes of neural oscillations at alpha (8 – 13 Hz) and gamma (30 – 100 Hz) frequencies in somatosensory and prefrontal brain areas have been related to pain. Thus, modulating neural oscillations to eventually modulate pain is a promising novel approach for pain treatment.
Transcranial alternating current stimulation (tACS) is an emerging neuromodulation technique which aims at non-invasively modulating neural oscillations in the human brain. During tACS, a weak alternating current is applied to the scalp with the goal of entraining neural oscillations at the stimulation frequency, thereby increasing their amplitude. The appeal of tACS is that it is non-invasive, safe, cost-efficient, and potentially mobile which allows for broad clinical applications. Thus, tACS is increasingly explored as a new treatment approach for neuropsychiatric disorders.
In our study, we therefore explored the potential of tACS to modulate pain. We systematically applied tACS at alpha and gamma frequencies or sham tACS over somatosensory and prefrontal cortices during tonic experimental pain in healthy human participants.
PainRelief.com: What are the main findings?
Response: Our main findings are that, using the current setup, tACS did not modulate the perception of pain. Bayesian statistics further supported a lack of tACS effects in most conditions including prefrontal and gamma tACS. The only exception was tACS at alpha frequencies over somatosensory cortex where evidence for tACS effects on pain perception was inconclusive.
PainRelief.com: What should readers take away from your report?
Response: Readers might take away three key points.
First, neurophysiological studies indicate that modulating neuronal oscillations to eventually modulate pain is a promising novel approach for the treatment of pain.
Second, tACS is one non-invasive and simple approach to modulate neuronal oscillations.
Third, our mostly negative findings show that we are not there yet.
PainRelief.com: What recommendations do you have for future research as a result of this work?
Response: A very general recommendation is that rigorous, well-controlled and transparent studies are needed to further explore the potential of tACS (and other neuromodulatory techniques) for treating pain. Furthermore, we should ideally make all our data available to the public so that the whole research community can take advantage of them. Finally, to advance the field, we should not only publish positive but also negative findings, as done here.
A more specific recommendation is that modulating neuronal oscillations at alpha frequencies over somatosensory brain areas is the most promising approach for further tACS studies.
May ES, Hohn VD, Nickel MM, Tiemann L, Gil Ávila C, Heitmann H, Sauseng P, Ploner M. Modulating Brain Rhythms of Pain using Transcranial Alternating Current Stimulation (tACS) – A Sham-controlled Study in Healthy Human Participants. J Pain. 2021 Apr 9:S1526-5900(21)00191-7. doi: 10.1016/j.jpain.2021.03.150. Epub ahead of print. PMID: 33845173.
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