How it (Mindfulness) Works? (Part 3)

“Mindfulness Training Ameliorates Addiction by Targeting Neurocognitive Mechanisms

In the third part of this excellent review paper  (1) we look at the empirical evidence is presented suggesting that MBIs ameliorate addiction by enhancing cognitive regulation of a number of key processes.

EMOTION REGULATION

When individuals are unable to marshal effective problem-solving to resolve a stressor, lack of a favorable resolution may lead to deployment of emotion regulation efforts to manage the emotional distress elicited by the stressful circumstance. Neuroimaging research has provided evidence for a reciprocal, dual-system neural network model of emotion regulation comprised of a dorsal brain system (e.g., dlPFC, dACC, parietal cortex) subserving top-down cognitive control, and a ventral brain system (e.g., amygdala, striatum) subserving bottom-up emotional impulses (133135). Top-down engagement of proactive cognitive control mechanisms regulates negative affect and attenuates the effects of emotional interference on cognition (135138), and is associated with increased activation of PFC which in turn attenuates amygdala activation (139, 140). Research suggests that dysregulated emotional reactions occur when the reciprocal balance between the relative activation of bottom-up and top-down neural circuits becomes tipped in favor of bottom-up processes (141). A number of studies suggest that mindfulness training may counter this imbalance and augment emotion regulation [for reviews, see Ref. (78, 142)] by restructuring neural function in favor of context-dependent top-down control processes. For example, Goldin and Gross (143) demonstrated that individuals with elevated negative affect at baseline who later received mindfulness training exhibited increased emotion regulatory capacity coupled with greater recruitment of attentional control resources and reduced amygdala activation during exposure to negative, self-relevant stimuli. Thus, by enhancing top-down cognitive control over emotional responses in a context-dependent fashion, MBIs may reduce drug use precipitated by negative affective states.

Importantly, MBIs provide training in cultivating a state of mindful awareness and acceptance of the extant emotional response as a precondition for emotion regulation. While acceptance of aversive mental experience may itself result in reduced negative affect (144), mindfulness training may also exert downstream facilitative effects on cognitive regulation of emotion following the acute state of mindfulness. For instance, mindfulness training may promote cognitive reappraisal, the process by which the meaning of a stressful or adverse event is re-construed so as to reduce its negative emotional impact (125). One theoretical model posits a multi-stage process of mindful emotion regulation (1, 145). According to this model, during an adverse experience mindfulness practitioners first disengage from initial negative appraisals into the metacognitive state of mindfulness in which cognitions and emotions are viewed and accepted as transitory mental events without inherent veridicality. Subsequently, the scope of attention broadens to encompass a larger set of previously unattended information from which new situational appraisals may be generated. By accessing this enlarged set of contextual data, present circumstances may be reappraised in an adaptive fashion that promotes positive affect and behavioral activation. For instance, a newly abstinent alcohol dependent individual might reappraise an affront by a former “drinking buddy” as evidence of their need to build new, sober relationships. In support of this model, recent studies indicate that mindfulness during meditation predicts enhanced cognitive reappraisal (146), which in turn mediates the association of mindfulness and reduced substance craving (147). This context-dependent use of prefrontal regulatory strategy represents a “middle way” between hypo- and hyper-activation of cognitive control resources, thereby preventing resource depletion and untoward rebound effects.

Speculatively, this “mindful reappraisal” process may involve spreading activation in a number of brain networks. Generating the state of mindfulness in the midst of a negative affective state may activate the ACC and dlPFC (148, 149), which could facilitate metacognitive monitoring of emotional reactivity, foster attentional disengagement from negative appraisals, and regulate limbic activation. In so doing, the acute state of mindfulness may attenuate activation in brain areas that subserve self-referential, linguistic processing during emotional experience (e.g., mPFC) while promoting interoceptive recovery from negative appraisals by increasing activation in the insula (113). Metacognitive disengagement from the initial negative appraisal may result in non-elaborative attention to somatosensory information, thereby facilitating the set shifting process of cognitive reappraisal, as brain activations shift from posterior to anterior regions of cortex centered on the node of the OFC. During this process emotional interference is attenuated while alternate appraisals are retrieved from memory and evaluated for goodness-of-fit to situational parameters and demands (150).

The effects of mindfulness-centered regulation of negative emotion might be measured with a standard emotion regulation paradigm [c.f. (137)], in which participants are instructed to use reappraisal to reduce negative affect in response to exposure to aversive visual stimuli [e.g., images from the International Affective Picture System; (151)]. In this task paradigm, mindfulness practitioners may exhibit enhanced reappraisal efficacy, as evidenced by reduced self-reported and psychophysiological responses to aversive stimuli on reappraise relative to attend trials. In that regard, a study employing ERP analysis found that when compared to controls, meditators exhibited significantly greater reappraisal efficacy as evidenced by significantly larger attenuation of brain activity during reappraisal of stressful stimuli in centro-parietal regions subserving attentional and emotional processing (152).

STRESS REACTIVITY

In addition to pro-regulatory effects on emotion, mindfulness training may facilitate neurocognitive regulation of the effects of stress on the autonomic nervous system. As addicts in treatment develop dispositional mindfulness through mindfulness training, they may be more able to engage prefrontal cortical modulation of the sympathetic “fight-or-flight” response via parasympathetic nervous system activation of the “vagal brake,” resulting in increased HRV and heart-rate deceleration in the face of stress or addictive cues (153, 154). Thus, increasing dispositional mindfulness may be reflective of greater neurovisceral integration and flexibility in the central autonomic network (67). This network is comprised of neuroanatomic and functional linkages between central (e.g., PFC and ACC) and autonomic (e.g., vagus nerve) nervous system structures which coordinate the self-regulation of attention, cognition, and emotion while exerting regulatory influences over perturbations to visceral homeostasis (155), such as those that might be evoked in abstinent substance dependent individuals exposed to stressful and/or substance-related stimuli. Mindful individuals may have greater capacity for contextually appropriate engagement and subsequent disengagement of neurocognitive resources in response to the presence and absence of stress and drug-cues. Such autonomic flexibility (156) engendered through mindfulness training may help persons in recovery from addiction adapt to situational demands without succumbing to a stress-precipitated relapse.

This hypothesis is consistent with evidence of the effects of mindfulness on neural function in dlPFC and ACC (149, 157), key structures involved in central autonomic regulation of HRV via downstream influences on the amygdala and hypothalamus (158, 159). Congruent with such findings, MBIs increase parasympathetically mediated HRV to an even greater extent than relaxation therapy (160,161), and decreases sympathetically mediated indices of stress (8), including blood pressure (162), heart rate (163), skin conductance responses (161), and muscle tension (164). These effects of mindfulness-centered regulation on autonomic function may result in improved ability to manage substance cue-reactivity. In support of this hypothesis, a Mindfulness-Oriented Recovery Enhancement intervention for alcohol dependence increased HRV recovery from stress and alcohol cue-reactivity (7). Congruent with this finding, relative to their less mindful counterparts, alcohol dependent individuals with higher levels of dispositional mindfulness exhibited greater attentional disengagement from alcohol cues which predicted the extent to which their HRV recovered from alcohol cue-exposure levels (67). Lastly, persons participating a mindfulness-based smoking cessation intervention who exhibited increased HRV during mindfulness meditation smoked fewer cigarettes following treatment than those who exhibited decreased HRV (165). Thus, addicts who develop dispositional mindfulness through participation in MBIs may become better able to regulate appetitive responses by virtue of enhanced neurocognitive control over autonomic reactivity to stress and substance cues.

The effects of MBIs on cognitive regulation of autonomic cue-reactivity might be measured with a stress-primed cue-reactivity paradigm, in which participants are first exposed to a laboratory stress induction [e.g., aversive IAPS images, c.f. (7); or the TSST, c.f. (132)], then exposed to substance-related cues (either in vivo, imaginally, or images of alcohol or drugs), and finally asked to use mindfulness skills to downregulate the resultant state of autonomic arousal.

References

1. Garland, E. L., Froeliger, B., & Howard, M. O. (2013). Mindfulness  training targets neurocognitive mechanisms of addiction at the attention-appraisal-emotion interface. Frontiers in psychiatry, 4.

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