The subjective experience of one’s environment is constructed by interactions among sensory, cognitive, and affective processes. For centuries, meditation has been thought to influence such processes by enabling a non-evaluative representation of sensory events. To better understand how meditation influences the sensory experience, we employed arterial spin labeling (ASL) functional magnetic resonance imaging to assess the neural mechanisms by which mindfulness meditation influences pain in healthy human participants. After four-days of mindfulness meditation training, meditating in the presence of noxious stimulation significantly reduced pain-unpleasantness by 57% and pain-intensity ratings by 40% when compared to rest. A two factor repeated measures analysis of variance was used to identify interactions between meditation and pain-related brain activation. Meditation reduced pain-related activation of the contra lateral primary somatosensory cortex. Multiple regression analysis was used to identify brain regions associated with individual differences in the magnitude of meditation-related pain reductions. Meditation-induced reductions in pain intensity ratings were associated with increased activity in the anterior cingulate cortex and anterior insula, areas involved in the cognitive regulation of nociceptive processing. Reductions in pain unpleasantness ratings were associated with orbitofrontal cortex activation, an area implicated in reframing the contextual evaluation of sensory events. Moreover, reductions in pain unpleasantness also were associated with thalamic deactivation, which may reflect a limbic gating mechanism involved in modifying interactions between afferent in put and executive-order brain areas. Taken together, these data indicate that meditation engages multiple brain mechanisms that alter the construction of the subjectively available pain experience from afferent information.
These results indicate that brief meditation training has beneficial effects on mood and cardiovascular variables that go beyond the demand characteristics of a sham meditation intervention.
Neuroimaging studies of human pain have revealed a widespread "pain matrix" distributed across both hemispheres of the brain. It is not resolved whether the pain matrix is biased toward one hemisphere, although behavioral and clinical data suggest that pain is perceived differently on the two sides of the body, and several neuroimaging studies suggest that pain processing in some regions of cortex may be lateralized toward the right hemisphere. The current study used fMRI in nine subjects to determine whether acute pain is preferentially processed in one cortical hemisphere. All cortical areas that were activated during the painful simulation were investigated, and several analytic approaches were used to directly compare activated regions to similar regions in the opposite hemisphere. Results indicated that four regions of the cortical pain matrix were activated either contralaterally (somatosensory cortex) or bilaterally (mid/posterior insula, anterior insula, and posterior cingulate). In addition, activation in five cortical regions during acute pain stimulation was localized either exclusively in the right hemisphere or was strongly lateralized to the right. These five areas were in the middle frontal gyrus, anterior cingulate, inferior frontal gyrus, medial/superior frontal gyri, and inferior parietal lobule. The location of some of these regions is consistent with the idea that there may be a right-lateralized attentional system to alert an organism to an infrequent, but behaviorally relevant, stimulus such as pain.
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