تجربه مدیتیشن ارزیابی منفی کمتری از درد پیش بینی می کند: شواهد الکتروفیزیولوژیک برای دخالت پاسخ های عصبی مقدماتی

The aim of mindfulness meditation is to develop present-focused, non-judgmental, attention. Therefore, experience in meditation should be associated with less anticipation and negative appraisal of pain. In this study we compared a group of individuals with meditation experience to a control group to test whether any differences in the affective appraisal of pain could be explained by lower anticipatory neural processing. Anticipatory and pain-evoked ERPs and reported pain unpleasantness were recorded in response to laser stimuli of matched subjective intensity between the two groups. ERP data were analysed after source estimation with LORETA. No group effects were found on the laser energies used to induce pain. More experienced meditators perceived the pain as less unpleasant relative to controls, with meditation experience correlating inversely with unpleasantness ratings. ERP source data for anticipation showed that in meditators, lower activity in midcingulate cortex relative to controls was related to the lower unpleasantness ratings, and was predicted by lifetime meditation experience. Meditators also reversed the normal positive correlation between medial prefrontal cortical activity and pain unpleasantness during anticipation. Meditation was also associated with lower activity in S2 and insula during the pain-evoked response, although the experiment could not disambiguate this activity from the preceding anticipation response. Our data is consistent with the hypothesis that meditation reduces the anticipation and negative appraisal of pain, but effects on pain-evoked activity are less clear and may originate from preceding anticipatory activity. Further work is required to directly test the causal relationship between meditation, pain anticipation, and pain experience.

The use of alternative medicine is common for self-managing chronic and stress-related conditions that do not respond well to conventional medicine [15]. Despite this there is debate about whether alternative therapies have anything to offer beyond the placebo effect [24]. A major problem facing research into alternative therapies is the lack of clear hypotheses regarding their therapeutic mechanisms. One of the few alternative therapies that has been adopted by conventional psychological medicine is mindfulness meditation [22], [39] and [43]. The therapeutic mechanisms of meditation have been discussed in terms of attentional functioning [5] and [27]. Such mechanisms may be clinically relevant to a wide range of psychological, psychosomatic and stress-related diseases [1] and [22]. Although there is a broad range of meditation techniques, those related to mindfulness meditation involve training in cognitive control, specifically the ability to voluntarily direct attention to a chosen sensory or cognitive event whilst minimizing distraction by other sensory or cognitive phenomena [27]. Mindfulness methods include focusing on the internal feeling of breathing and other body sensations at objects of concentration. It has been noted that one aspect of training in meditation is to learn how to re-focus attention away from either past or anticipated future experience and onto present-moment experience [5] and [10]. Meditation should therefore reduce the emotional appraisal of pain or other stressful events by withdrawing attention away from anticipating their unpleasantness. This would be expected to be associated with reductions in brain processes related to anticipating the unpleasantness of pain, without necessarily reducing those brain processes related to the pain itself. Research using fMRI suggests that regions of the pain matrix showing differential responses to pain in meditators include the thalamus, primary and secondary somatosensory cortices, insula, prefrontal cortex, and the anterior cingulate cortex [23] and [34]. However, the effects of meditation may occur at multiple time points in the sequence of anticipating and experiencing pain. Limitations in the design of fMRI investigations have meant that it is not clear whether meditation primarily affects anticipatory or pain-evoked responses. We aimed to resolve this problem using high-density electrophysiology to measure affective processing during the anticipation and response to pain. We recruited participants with a broad range of experience of meditation to compare with a non-meditating control group and to determine the effects of lifetime meditation experience. We hypothesized that meditation experience would be related to anticipatory activity in brain regions such as cingulate, prefrontal and parietal cortices. We used a methodology previously reported [7], [8], [9] and [11] for defining the sources of brain activity during different time periods of anticipation and pain experience. We and others have previously suggested that early anticipatory processes are likely to involve establishing an expectation [8] and confidence in that expectation [9]. However, late anticipatory processes more likely relate to preparatory (e.g. attentional and motor) and motivational processes, as well as establishing top-down influences on pain [8]. It is during late anticipation that we would expect differences in cognitive control to influence the affective appraisal of pain and top-down affective influences on pain perception.

Our data is consistent with the hypothesis that meditation reduces the anticipation and negative appraisal of pain. This has implications for the use of mindfulness meditation in chronic pain: individuals whose pain is strongly influenced by anticipation may benefit most. However, further work is required to directly test the causal relationship between meditation, pain anticipation, and pain experience, using experiments that can assess pain processing independently from anticipation.