Research done at Manchester University shows significant pain reduction in subjects exposed to alpha wave stimulation. The researchers believe alpha waves could be a viable treatment for sufferers of chronic pain, from fibromyalgia to arthritis. Read the official experiment abstract for an in depth look at the power of alpha waves and binaural stimulation therapy.
Alpha power is believed to have an inverse relationship with the perception of pain. Increasing alpha power through an external stimulus may, therefore, induce an analgesic effect. Here, we attempt to modulate the perception of a moderately painful acute laser stimulus by separately entraining three frequencies across the alpha band: 8, 10 and 12 Hz.
Participants were exposed to either visual or auditory stimulation at three frequencies in the alpha-band range and a control frequency. We collected verbal pain ratings of laser stimuli from participants following 10 minutes of flashing LED goggle stimulation and 10 minutes of binaural beat stimulation across the alpha range. Alterations in sleepiness, anxiety and negative mood were recorded following each auditory or visual alpha-rhythm stimulation session.
A significant reduction in pain ratings was found after both the visual and the auditory stimulation across all three frequencies compared with the control condition. In the visual group, a significantly larger reduction was recorded following the 10-Hz stimulation than succeeding the 8- and 12-Hz conditions.
This study suggests that a short presentation of auditory and visual stimuli, oscillating in the alpha range, have an analgesic effect on acute laser pain, with the largest effect following the 10-Hz visual stimulation. Pain reductions following stimulation in the alpha range are independent of sleepiness, anxiety, and negative moods.
This study provides new behavioural evidence showing that visual and auditory entrainment of frequencies in the alpha-wave range can influence the perception of acute pain in humans.
The alpha rhythm (7–14 Hz) is the most studied frequency band in the human brain, as it can be detected in 95% of healthy young adults with their eyes closed (Srinivasan, 1999). The alpha rhythm has historically been described as an ‘idling’ rhythm and was believed to represent low information processing. However, more recent work indicates a central role in cognitive processing, specifically the top-down control of sensory information (Klimesch et al., 2007). Suppression of alpha power in the contralateral sensorimotor and occipital cortices has been repeatedly found to be correlated with the strength of a painful stimulus (Mouraux et al.,2003; Ohara et al., 2004; Raij et al., 2004; Ploner et al., 2006; Hu et al., 2013; Peng et al., 2014). Importantly, behavioural pain intensity ratings have been directly correlated with decreases in alpha power (Mouraux et al.,2003; Babiloni et al., 2006; Gross et al., 2007).
Early work by Trifiletti (1984), observing that high alpha was associated with intense analgesia, alluded to the idea that this relationship may work both ways. The concurrent presence of high alpha power during analgesia could indicate a causal relationship. Alpha rhythms are believed to arise from the thalamus and subsequently transmitted through thalamo-cortical tracts to the cortex. Alpha rhythms can, hence, be influenced via inputs to the thalamus, synchronizing or desynchronizing alpha oscillations (Schmidt et al., 1985). Recent neurofeedback studies have developed this idea and confirmed brain training to increase alpha power can lead to a long-term reduction in chronic pain (Jensen et al., 2013). The main disadvantage of neurofeedback is that it takes concentration and often weeks of training to be effective and thus is currently ineffective for acute pain (Kayiran et al., 2010).
Visual and auditory entrainment enables almost immediate increases in cortical alpha power through an external pulse with a consistent frequency oscillating in the alpha range (Frederick et al., 2005; Spaak et al.,2014). Entrainment occurs when other regions of the brain fall into lockstep with the stimulated cortex, eliciting a broader increase in alpha power (Halbleib et al., 2012; Thut et al., 2012; de Graaf et al., 2013; Spaak et al., 2014).
While visual alpha entrainment primarily affects the primary visual cortex with the strongest resonance at 10 Hz (Herrmann, 2001; de Graaf et al., 2013), literature suggests that modulations in cortical activity are widely elicited throughout the cortex (Timmermann et al., 1999; de Graaf et al., 2013). Although resting EEG records maximal alpha amplitude over the occipital regions (Cantero et al., 2002), entrainment through auditory stimulation proves just as effective at increasing alpha power (Schwarz and Taylor, 2005; Karino et al.,2006). Both visual and auditory alpha entrainments, thus, prove promising candidates for effortless acute pain relief.
In this study, we entrained three different alpha frequencies (8, 10 and 12 Hz) with the aim to achieve a meaningful level of experimental pain relief through either auditory or visual alpha entrainment. We hypothesized that we would observe the largest reduction in pain ratings after the 10-Hz stimulation in both the visual and auditory studies, as this is closest in frequency to the average peak of the spectral distribution of the alpha rhythm (Klimesch, 1997; Posthuma et al., 2001).
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