Friday, September 23rd
Analgesic Effects of Alpha Rhythm Entrainment Through Passive Visual Stimulation
The cortical alpha rhythm (7-14Hz) plays a central role in the top-down control (or “gating”) of somatosensory information. Based on knowledge that acute noxious stimuli induce a suppression of cortical alpha rhythms, we investigated whether therapeutically augmenting alpha rhythms have analgesic effects. The cortical alpha rhythm was augmented using external sensory stimuli using a process known as entrainment, in which neural oscillations naturally adapt to the frequency of the driving stimulus. In particular, visual entrainment at 10Hz can be observed widely throughout the cortex, potentially impacting the top-down modulation of nociceptive processing. Our studies provided the first evidence that visual alpha entrainment reduces the perceived intensity of experimental pain and suppresses acute nociceptive processing. EEG source modelling revealed that increased alpha power and decreased nociceptive processing overlapped in precuneus and posterior cingulate cortex, with further reductions in nociceptive processing in insula cortex. Extending this work, we conducted a proof-of-concept controlled study in 28 patients with chronic pain comparing 10 Hz (alpha) and 7 Hz (control) frequency blocks in a randomized cross-over design. Frontal alpha power increased when stimulating at 10 Hz when compared to 7 Hz, correlating with a reduction in chronic pain intensity and unpleasantness.