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Visual and auditory stimulation at 3 frequencies in the alpha-band range caused an analgesic effect in participants exposed to experimental pain, according to a study recently published in the European Journal of Pain.1
The presence of alpha waves has been shown to correlate positively with the perception of pain. Suppression of alpha power boosts the perception of pain, while higher alpha rhythms are associated with analgesia. Boosting alpha activity through neurofeedback, a computer-aided method in which patients learn to selectively modulate neuronal oscillations via operant conditioning, has been demonstrated to be effective in chronic pain.2
However, neurofeedback requires significant training and concentration, making it unsuitable as a treatment for acute pain. In contrast, rhythmic sensory stimuli oscillating at a specific frequency can increase the EEG power of that frequency almost immediately, in a process known as neural entrainment.
For the current study, 64 healthy volunteers were randomly assigned to auditory or visual entrainment groups. Patients in the visual arm of the study (n=32) wore in-house built flashing LED goggles delivering visual stimulation in the alpha-band range at 8, 10, 12 and 1 Hz (control). Those in the audio arm (n=32) received 10 min of auditory entrainment in the form of binaural beats at 8, 10 and 12 Hz. Both auditory and visual entrainment sessions lasted 10 minutes for each of the frequencies.
Following each 10-minute session, participants received 30 moderately painful heat laser pulses and were requested to rate the pain intensity on a 1-10 numerical scale. Participants were also asked to complete a set of standardized behavioral questionnaires at the beginning of each visit, and following each entrainment session. Patients in the auditory group received an additional control visit in which the same painful stimuli were administered, but white noise was substituted for the alpha entrainment.
Results showed that entrainment at 8, 10 and 12 Hz resulted in reduced pain perception from baseline in both visual and auditory arms of the study, with the greatest effect observed at 10 Hz. Changes in pain ratings in the visual and auditory groups were not statistically compared, due to distinctions in visual and auditory entrainment paradigms; however, visual stimulation at 8 and 10 Hz was associated with a numerically larger decrease in pain ratings than the auditory entrainment. Analysis of the questionnaire scores revealed no significant changes or correlations.
Summary and Clinical Applicability
“This study provides new evidence that visual and auditory entrainment in the alpha range can influence the perception of acute pain independently of arousal and negative emotional influences,” wrote the investigators in their concluding remarks.
“Overall, visual entrainment produced a larger effect than auditory entrainment in the mid- and lower alpha frequencies. This provides further evidence that external stimulation can modulate pain perception and requires further study to ascertain its relevance to clinical pain states.”
References
- Ecsy K, Jones AKP, Brown CA. Alpha-range visual and auditory stimulation reduces the perception of pain. Eur J Pain Lond Engl. November 2016. doi: 10.1002/ejp.960.
- Jensen MP, Gertz KJ, Kupper AE, et al. Steps toward developing an EEG biofeedback treatment for chronic pain. Appl Psychophysiol Biofeedback. 2013;38(2):101-108.
