Abstract
Studies have shown an association between sensorimotor α-oscillation and pain perception. It suggests the potential use of neurofeedback (NFB) training for pain modulation through modifying sensorimotor α-oscillation. Here, a single-session NFB training protocol targeted on increasing sensorimotor α-oscillations was applied to forty-five healthy participants. Pain thresholds to nociceptive laser stimulations and pain ratings (intensity and unpleasantness) to identical laser painful stimulations were assessed immediately before and after NFB training. Participants had larger pain thresholds, but rated the identical painful laser stimulation as more unpleasant after NFB training. These pain measurements were further compared between participants with high or low NFB training efficacy that was quantified as the regression slope of α-oscillation throughout the ten training blocks. A significant increase in pain thresholds was observed among participants with high-efficacy; whereas a significant increase in pain ratings was observed among participants with low-efficacy. These results suggested that NFB training decreased the sensory-discriminative aspect of pain, but increased the affective-motivational aspect of pain, whereas both pain modulations were dependent upon the NFB training efficacy. Importantly, correlation analysis across all participants revealed that a greater NFB training efficacy predicted a greater increase in pain thresholds particularly at hand contralateral to NFB target site, but no significant correlation was observed between NFB training efficacy and modulation on pain ratings. It thus provided causal evidence for a link between sensorimotor α-oscillation and the sensory-discriminative aspect of pain, and highlighted the need for personalized neurofeedback for the benefits on pain modulation at the individual level. Future studies can adopt a double-blind sham-controlled protocol to validate NFB training induced pain modulation.
Highlights
Oscillations of brain activities within the alpha-frequency band (8–12 Hz, α-oscillations) is generally thought to reflect mechanisms that inhibit processing of irrelevant sensory and task information by gating the information flow across different brain regions (Jensen and Maza heri, 2010; Klimesch, 2012)
Planned analysis showed that for participants in the low-efficacy group, ratings of pain unpleasantness were higher in the post-NFB session than those in the pre-NFB session (6.85 ± 0.73 vs. 5.99 ± 0.72, p = 0.007), whereas no significant difference was observed in the high-efficacy group (4.84 ± 0.73 vs. 4.73 ± 0.72, p = 0.72). These results indicated that participants with low NFB training efficacy reported more pain ratings to suprathreshold painful stimuli after NFB training, but not for those with high NFB training efficacy
The significant increase in pain thresholds after NFB training was selectively applicable to the high-efficacy group; whereas the significant increase in pain rat ings after NFB training was selectively applicable to the low-efficacy group
Summary
Oscillations of brain activities within the alpha-frequency band (8–12 Hz, α-oscillations) is generally thought to reflect mechanisms that inhibit processing of irrelevant sensory and task information by gating the information flow across different brain regions (Jensen and Maza heri, 2010; Klimesch, 2012). Suppression of senso rimotor α-oscillation induced by nociceptive stimulation is thought to reflect the excitability of the somatosensory cortex (Hu et al, 2013; Ploner et al, 2006). Previous studies have documented the association between spontaneous α-oscillations and the perception of both experi mental and clinical pain (Peng et al, 2015; Ploner et al, 2017). The amplitude of spontaneous α-oscillations over sensorimotor cortex was negatively correlated with pain perception (Babiloni et al, 2006; Tu et al, 2016). Abnormal spontaneous α-oscillations have been observed among patients with chronic pain, a phenomenon that has been interpreted as dysfunctional cortical inhibition (Ahn et al, 2019; Kim et al, 2013; Pinheiro et al, 2016; Ye et al, 2019). The relationship between α-oscillation amplitude and pain perception suggests that a neuromodulation technique that can alter sensorimotor α-oscillation has the potential to modulate pain perception
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