Alpha transcranial alternating current stimulation modulates pain anticipation and perception in a context-dependent...

Area of Science:

• Neuroscience
• Pain Research
• Brain Stimulation

Background:

• Pain perception is influenced by brain anticipatory processes.
• Sensorimotor alpha oscillations (α-oscillations) are suppressed during pain anticipation, with higher levels correlating to lower pain sensitivity.
• Alpha transcranial alternating current stimulation (α-tACS) can modulate these oscillations, potentially altering pain perception.

Purpose of the Study:

• To investigate the immediate and sustained effects of α-tACS on pain anticipation and perception.
• To examine how the certainty of pain expectations influences these effects.
• To explore the neural mechanisms underlying α-tACS modulation of pain.

Main Methods:

• A double-blind, sham-controlled study with 80 healthy participants.
• Real or sham α-tACS applied over the right sensorimotor region for 20 minutes.
• Assessment of behavioral and neural responses (laser-evoked potentials, brain oscillations) before, immediately after, and 30 minutes post-stimulation under certain and uncertain pain conditions.

Main Results:

• Real α-tACS disrupted habituation of laser-evoked potentials (N2-P2) more under certain expectations, with sustained effects.
• α-tACS enhanced somatosensory α1-oscillations and midfrontal θ-oscillations, particularly in certainty conditions.
• Mediation analysis indicated α-tACS reduced pain reactivity via somatosensory α1-oscillations but increased it via midfrontal θ-oscillations, with the latter effect being stronger and more sustained.

Conclusions:

• α-tACS shows potential for pain relief by augmenting somatosensory α-oscillations.
• However, its pronounced and sustained enhancement of midfrontal θ-oscillations may paradoxically increase pain sensitivity (hyperalgesia), especially with certain pain expectations.
• The findings highlight the complex, dual effects of α-tACS on pain processing, dependent on expectation certainty and neural pathway modulation.