Mindfulness Meditation Modulates the Conscious Experience of Pain: A Neuroscientific Account

!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.1//EN” “http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd”>

Joshua A. Grant and Fadel Zeidan

Pain is a subjectively available experience, sensitive to change arising from interactions with a great many factors, often in parallel with the underlying nociceptive activity, but not necessarily so. As defined by the International Association for the Study of Pain (IASP), “pain is an unpleasant sensory or emotional experience associated with actual or potential damage” and “is always subjective” in nature. Thus, to be considered pain at least some degree of conscious awareness is necessary.

Known modulators of pain could be said to exert their influence directly (i.e., altering the pain and/or nociceptive activity itself), or indirectly (i.e., by modifying the state in which the experience is embedded). This could be viewed as having a primarily influence on either the content or background of consciousness. Meditative states are one example of the latter, in which practices are said to alter the context of our conscious environment. During mindfulness meditation one attempts to adopt a more accepting attitude toward their experience. The practice is said to have profound implications for fundamental schemas in which experience is embedded, such as the concept of self. It is then fitting that mindfulness meditation has been shown to attenuate the subjective experience of pain. Interestingly, it appears to do so through quite unique neuronal mechanisms.

The goal of this chapter is to explore the experience of pain in relation to mindfulness-based meditation practices. The chapter builds on our previous work [22, 63] by shifting the focus to examining how changes to our consciousness or awareness, arising from these techniques, might help explain their influence on pain. We begin with a description of mindfulness meditation, providing an overview of several popular techniques, as well as their putative neural correlates. This is followed by a short summary describing the conscious experience of pain and how mindfulness meditation may relate. We then move to the scientific literature examining the effects of mindfulness on pain from a state perspective and then from a trait perspective. Finally, we discuss how other meditation-related work supports our interpretation of the influence of mindfulness on the experience of pain.

WHAT IS MINDFULNESS MEDITATION?

Mindfulness meditation is a fairly loose term to which many meditation practices apply. These practices have been found to improve a wide spectrum of clinically relevant cognitive and health outcomes [25]. In patients, training in mindfulness improves to different extents the self-reports of anxiety [21, 34, 66], depression [3, 57], stress [1, 6, 7, 35], and cognition [29, 41–43, 64]. Mindfulness-related health benefits are associated with enhancements in cognitive control, emotion regulation, positive mood, and acceptance [25], and interestingly, each of these phenomena have also been associated with pain modulation.

Generally, mindfulness has been described as a “nonelaborative, nonjudgmental awareness” of the present moment experience [32]. However, one does not need to be meditating, or even trained in meditation, to be mindful. Varying degrees of “trait mindfulness” exist in the general population, outside of any formal training [11, 13]. However, mindfulness can also be developed with mental training routines such as meditation. A variety of different practices are subsumed under the general rubric of “mindfulness meditation.” Thus, it is critical that the specifics of the practice being taught or employed be recognized [13, 41, 53]. In the present chapter, we will focus on two rather coarse categories of mindfulness practice, namely, focused attention (samatha in the Pali language) and open monitoring (vipassana in the Pali language) [41]. In general, these two groups of practices are centered on developing a number of distinct cognitive skills.

During focused attention, or samatha [59], the practitioner is taught to develop cognitive control and attentional stability by training the mind to sustain focus on the moment-to-moment quality and characteristics of sensory, emotional, and cognitive events [41]. In brief, samatha involves directing one’s attention to the dynamic nature of the chosen object of meditation, most often the sensations of breath or body. When attention drifts from the object of focus, to a distracting sensory event, for example, the practitioner is taught to acknowledge the event and to disengage by returning their attention back to the meditative object (e.g., the breath). Often samatha is taught as a series of distinct practices increasing in complexity (e.g., mindfulness of breath, of emotions, of thoughts). While samatha practices aim primarily at gaining mental control and stabilization of attention, they naturally lead, and in a somewhat ambiguous way, to the traits associated with open monitoring meditation, or vipassana. Indeed, it is difficult to see where samatha ends and vipassana begins.

As a developmental derivative of focused attention practice, the mindfulness practitioner finds himself or herself almost naturally transitioning into the open monitoring mental stance known as vipassana. Whereas samatha often entails focus on a single, dynamic, meditative object, open monitoring practices are more inclusive. When applied to the full extent, these practices are associated with a nondirected acknowledgment of any sensory, emotional, or cognitive event that arises in the mind. While practicing open monitoring, the practitioner is said to experience their current “event” without evaluation, interpretation, or preference. Fittingly, open monitoring meditation has been described as a state of nonappraisal and/or a nonelaborative mental stance [23, 63].

Traditionally, focused attention is taught before, or as a prerequisite to, open monitoring practice. The reason for this is likely that a greater capacity for attentional stability and mental control [28, 64] would allow more success in the daunting task of relaxing one’s tendency to automatically engage with, and appraise, ongoing experience. As the practitioner becomes more adept in meditation, he or she will be able to employ a unique cognitive approach where consciously available sensory events can be simply “let go,” presumably leading to significant reductions in affective or cognitive appraisals/reactions to the event. It should be noted, however, that the goal of mindfulness is not to simply train what might be termed a “Teflon mind,” incapable of holding a sensory or cognitive percept. Rather, a balance between sustained attention on one hand and “letting go” on the other should provide the ability to adaptively and flexibly shift between mindful and more reactive or absorbed thought processes.

THE SHAPING OF PAINFUL EXPERIENCE

Pain is a complex, and subjective, conscious experience. Psychophysical evaluations of painful experiences demonstrate that dissociable differences exist between the sensory aspects (i.e., intensity) and the affective aspects (i.e., unpleasantness), although these two dimensions are usually highly correlated [45, 47, 50]. Further, the integration of a constellation of sensory, cognitive, and affective factors including the mood, psychological disposition, meaning-related cognitions (e.g., suffering), prepain cognitive state (e.g., expectations), etc. interact to provide a continually changing experience. In short, the experience of pain can be significantly influenced by the context in which it occurs. One example of this comes from studies assessing pain in cancer patients and in women giving birth [46]. The pain of labor was rated as significantly higher on sensory aspects compared to the affective dimension. In contrast, cancer pain was rated significantly higher on pain unpleasantness than pain intensity [48]. The suggestion here is that the contextual evaluation of welcoming a new baby into the world when compared to facing one’s own death has profound implications for what might have been very similar experiences otherwise. In what follows we suggest that mindfulness, in a similar albeit less profound manner than giving birth or dying, also alters the meaning, interpretation, and appraisal of nociceptive information. First, we will give an overview of what these practices appear to be doing in the brain.

A CAVEAT AND THE NEURAL CORRELATES OF MINDFULNESS MEDITATION

Elucidating the brain networks underlying any experiential state is complicated by many factors, not least of which is often the lack of outward behavioral markers preventing even a coarse orientation with the mental landscape. Specifically concerning mindfulness, most studies apply the construct to something, such as pain, and cannot make statements about what the state of mindfulness, in itself, might reveal in the brain. What these studies can say is that “mindfulness of pain,” or, “mindfulness of the breath during pain” activates a specific and distinct pattern of neural activation. Here we make the assumption, rightly or wrongly, that there is something to mindfulness, in terms of brain activity, beyond the object to which it is being applied. This postulation is supported by claims of the existence of mindful but nonreferential awareness [13, 30]. Nevertheless, repeated experimentation, literature reviews, and meta-analyses paint a slowly emerging picture of what is happening in the brain during mindfulness.

Contrasting Hindu and Buddhist meditative practices, Tomasino et al. [58] conducted a meta-analysis of functional imaging studies which (a) reported the style of meditation used, (b) asked participants to meditate, and (c) reported whole brain activation (i.e., not simply regions of interest). Consistent with the idea that Buddhist practices are associated more with the cognitively oriented concept of mindfulness, and Hindu practices more with absorptive attention, the authors reported primarily medial and lateral prefrontal loci for Buddhism versus parietal and cingulate cortices for Hindu practices. These results are largely consistent with another recent meta-analysis of 21 meditation studies, looking at structural brain correlates [16]. These authors found significantly greater gray matter of the anterior insula (aINS), dorsal anterior cingulate cortex (dACC), prefrontal cortex (PFC) (including lateral and orbitofrontal [OFC] regions), hippocampus, and several temporal lobe regions. Interestingly, when looking at only novices, gray matter differences were observed selectively in the cingulate (posterior cingulate cortex [PCC/ACC]) and insula. The structural changes to PFC were restricted to more advanced meditators. Together, these two meta-analyses support our previous suggestion that as skill and proficiency of mindfulness increase, there is a shift from active prefrontal regulation to more effortless regulation, which we suggest requires less prefrontal recruitment. That is, novice meditators show increased activation of PFC while attempting to be mindful whereas advanced practitioners show lower activity in comparison to both their own control conditions and control groups [22, 23, 63]. Of course, the context and meditative object being regulated in individual functional imaging studies will dictate which other brain regions and networks are activated.

NEURAL MECHANISMS SUPPORTING MINDFULNESS-BASED ANALGESIA

Several approaches have been taken to studying the influence of mindfulness on pain. The first approach we review is state induction. That is, the active practice of mindfulness meditation. While studies have looked at both advanced practitioners and beginners, the latter is particularly salient, as the transition from mindfully “naïve” to mindful seems to be profound, allowing observation of large effects. As one advances in skill and proficiency the baseline itself begins to change. One begins to have greater “trait” mindfulness, not necessarily needing to sit and meditate to produce a nonevaluative cognitive approach. One possible consequence of this, for research, is that state inductions in advanced practitioners may seem less remarkable than in beginners. Indeed, this may explain why certain effects appear to be much larger in novices. One solution to this is to take a trait approach, comparing practitioners and controls in nonmeditative states. This approach is also important as it provides an indication of whether meditative training has any long-term impact on daily life, which is ultimately the goal.

State-Induced Mindfulness Meditation during Pain

Only gold members can continue reading. Log In or Register to continue