Peak alpha frequency is not significantly altered by five days of experimental pain and repetitive transcranial stimulation of the left dorsolateral prefrontal cortex

Repetitive transcranial magnetic stimulation (rTMS) holds promise as a non-invasive pain treatment. Given the link between individual peak alpha frequency (PAF) of resting-state electroencephalographic recordings and pain sensitivity, and the potential for rTMS to modulate PAF, we investigated these relationships through a secondary analysis of established rTMS-induced analgesia in an experimental model of sustained muscle pain.

In a randomised, single-blind, sham-controlled experiment, 30 healthy adults underwent either active (n=15) or sham (n=15) high-frequency rTMS (20 min) to the left dorsolateral prefrontal cortex for five consecutive days following induction of sustained experimental pain by nerve growth factor (NGF) injected into the right extensor carpi radialis brevis muscle. The pain intensity was assessed daily for 14 days on a numerical rating scale (NRS). PAF of the resting state electroencephalography (5 min) was assessed before and one day after the five rTMS treatment days.

The pre-registered analysis revealed no significant changes in PAF following five consecutive days of active (from 9.90±0.39 Hz to 9.95±0.38 Hz) or sham (from 9.86±0.44 Hz to 9.81±0.35 Hz) rTMS, suggesting that the impact of rTMS on NGF- induced pain is independent of PAF modulation. However, exploratory analysis indicated an association between the absolute difference of baseline PAF to 10 Hz (i.e. the rTMS frequency) and higher NRS pain ratings at Day 5 in participants receiving active rTMS. This suggests that rTMS is more efficient when delivered close to the individual PAF and necessitates further exploration of PAF’s role in rTMS-induced pain relief.

Disclosures: The Center for Neuroplasticity and Pain (CNAP) is supported by the Danish National Research Foundation (DNRF121). The authors have no conflicts of interest to declare.