Highlights
- •Transcranial alternating current stimulation (tACS) at alpha frequency affects pain.
- •Alpha tACS over somatosensory regions compared with sham lowered perceived pain.
- •However, uncertainty about pain intensity moderated this effect.
- •Perceived pain was lower during alpha tACS, only when pain intensity was uncertain.
- •Alpha tACS has the potential to alleviate pain, particularly when pain is uncertain.
Abstract
Alpha activity directly before pain onset has been implicated in pain experience with
higher prestimulus alpha associated with lower reported pain. However, expectations
about pain intensity also seem to affect prestimulus alpha activity. To date, evidence
for a relationship between alpha activity and pain experience has been largely correlational.
Transcranial alternating current stimulation at alpha frequency (alpha tACS) permits
direct manipulation of alpha activity and therefore an examination of the potential
causal relationship between alpha activity and pain. We investigated whether somatosensory
alpha tACS could reduce pain experience and whether this was influenced by uncertainty
about pain intensity. In a within-subjects design, perceived pain intensity and unpleasantness
were assessed in 23 participants during alpha tACS and sham stimulation. Visual cues
preceding the pain stimulus were used to manipulate uncertainty. A significant tACS
× Uncertainty × Stimulus intensity interaction was found for reported pain intensity
(F2,44 = 4.50, P = .017, partial η2 = .17) and unpleasantness (F1,22 = 4.78, P = .040, partial η2 = .18). Pain experience during the application of somatosensory alpha tACS was significantly
lowered compared with sham stimulation, but only when the intensity of an upcoming
stimulus was uncertain.
Perspective
To our knowledge, this is the first study to suggest that somatosensory alpha tACS
might lead to a reduction in pain. Interventions targeting alpha activity may have
the potential to alleviate chronic pain. However, a patient's expectation about the
intensity of upcoming pain must also be taken into account.
Key words
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Article info
Publication history
Published online: March 15, 2018
Accepted:
February 22,
2018
Received in revised form:
January 15,
2018
Received:
September 2,
2017
Footnotes
The study described herein is part of a PhD funded by the University of Leeds, Leeds LS2 9JT, United Kingdom (University Research Scholarship).
The authors have no conflicts of interest to declare.
Identification
Copyright
© 2018 by the American Pain Society
