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キーワード:
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要旨:
Introduction:
Recently, several studies reported behavioral and brain data on pain analgesia induced by mindfulness-based interventions (Zeidan, Martucci et al. 2011, Lutz, McFarlin et al. 2013, Zeidan, Emerson et al. 2015). However, the exact mechanisms of mindfulness-induced pain relief remain unclear (Tang, Hoelzel et al. 2015). Mindfulness comprises several distinct elements, whose specific effects on pain analgesia have not yet been dissociated: mindfulness-based interventions have only been compared to sham meditation and placebo conditioning as a whole (Zeidan, Emerson et al. 2015). To close this gap, we designed a large-scale longitudinal study on pain analgesia induced by three different instructions based on classic meditation practices: focus on the breath (FB), observe thoughts (OT) and loving-kindness (LK); and obtained behavioral and brain data before and after mental training.
Methods:
For the ReSource project (Singer, Kok et al. 2015), we recruited 332 participants (197 female; age 40.74±9.24 years) with no previous mediation experience. Before training, participants underwent fMRI involving low vs. high painful stimulation by a short (1s) electric pulse to the left forearm. To reduce pain, we asked participants to use one of three meditation-based instructions: (i) focus on the breath (FB-I)–direct your attention to and observe your breath; (ii) observe thoughts (OT-I)–observe your thoughts from a distance and let them arise and fall without identification; (iii) loving-kindness (LK-I)–imagine a loved person and be attentive to the emerging feeling of warmth. Pain was assessed through individual behavioral intensity (INT) and unpleasantness (UNP) ratings. Participants then followed a 9-month mental training during which core meditations (FB, OT, LK) underlying the three different instructions were practiced three months each. At the end of every training module, we acquired additional fMRI scans to assess the longitudinal effects of mental training on pain analgesia induced by meditation-based instructions. Separate retest control cohorts not obtaining any mental training were also included. Data were analyzed with SPSS (version 22) and SPM8.
Results:
Before training, behavioral INT and UNP ratings significantly decreased for all three instructions (ps<.013) with no differential effects. However, on the brain level, only the FB-I was found to significantly reduce pain-related activity in bilateral insula, anterior cingulate, SII, amygdala and thalamus (p<.001 unc. height & p<.05 FWE-cor. extent). Furthermore, there only was a significant positive correlation between activation decrease in above areas and UNP ratings decrease in participants using the FB-I (same statistical threshold). As a result of training, pain analgesia induced by meditation-based instructions increased in strength. This was reflected by a significantly larger UNP ratings decrease across all training cohorts (versus controls) the longer the training lasted (p=.012). Furthermore, in training cohorts, we observed differential longitudinal effects of mental training modules on the efficiency of pain-analgesia induced by meditation-based instructions (p=.019). Concomitant longitudinal changes in brain activation and their correlation with behavioral data linked to pain relief will be outlined in detail on the poster.
Conclusions:
Our data reveal that the previously observed behavioral and brain effects of mindfulness-based interventions on pain analgesia can be decomposed into distinct elements, of which the FB-I appears to have the strongest effect on pain relief before training onset. Furthermore, we show that a 9-month mental training not only significantly increases behavioral pain analgesia induced by meditation-based instructions overall, but that the different training modules have dissociable
longitudinal effects on behavior and brain activity during instruction use. These data importantly add to the available literature on the mechanistic underpinnings of contemplative practice.
