How does mindfulness meditation work? Proposing mechanisms of action from a conceptual and neural perspective.
Holzel, B.K., Lazar, S.W., Gard, T., Schuman-Olivier, Z., Vago, D.R., & Ott, U. (2011)
 Perspectives on Psychological Science, 6(6), 537-559.

­­Abstract

Cultivation of mindfulness produces beneficial effects on well-being and ameliorates psychiatric and stress-related symptoms.

Components through which mindfulness meditation exerts its effects:

• Attention regulation
• Body awareness
• Emotion regulation
• Change in perspective on the self

Definition of mindfulness

Mindfulness is nonjudgmental attention to experiences in the present moment.

Two component model of mindfulness

• The regulation of attention in order to maintain it on the immediate experience
• Approaching one’s experiences with an orientation of curiosity, openness, and acceptance, regardless of their valence and desirability.

The practice of mindfulness meditation encompasses focusing attention on the experience of thoughts, emotions, and body sensations, simply observing them as they arise and pass away.  

Need for a theoretical framework

There is a relative paucity of theoretical reviews that consolidate the existing literature into a comprehensive theoretical framework.

Five facets of mindfulness

• Observing
  Attending to or noticing internal and external stimuli
• Describing
  Noting or mentally labelling these stimuli
• Acting with awareness
  Attending to one’s current actions, as opposed to behaving automatically or absentmindedly
• Nonjudging intter experience
  Refraining from evaluation of one’s sensations, cognitions and emotions
• Non-reactivity to inner experience
  Allowing thoughts and feelings to come and go, without attention getting caught in them

Components of mindfulness mediation

The combination of the following components describe much of the mechanism of action through which mindfulness works

• Attention regulation
• Body awareness
• Emotion regulation
  • Reappraisal
  • Exposure, extinction, and reconsolidation
• Change in perspective on the self

These components interact closely to constitute a process of enhanced self-regulation.
The different components might come into play to varying degrees within any specific moment during mindfulness meditation.

Attention regulation

Many mediation traditions recommend a focused attention meditation before moving on to other types of meditations later in the learning process.
In focused attention meditation, attention is supposed to rest on a single object.
Whenever the practitioner notices that the mind has wandered off, she or he returns it to the chosen object.

Behavioural findings on meditation and executive attention

During focused attention meditation, distracting external events as well as memories or thoughts about future events represent conflicts to task goals. These are disregarded while the practitioner concentrates on the meditative object.

Maintaining the focus of attention on a pursued object, while disregarding distractions, is referred to as conflict monitoring, or executive attention.

Neural mechanism of executive attention

The anterior cingulate cortex (ACC) enables executive attention by detecting the presence of conflicting emerging from incompatible streams of information processing.
During meditation, when distracting external events or memories conflict with task goals, ACC activation may contribute to the maintenance of attention by altering the systems implementing top-down regulation to resolve this conflict.

Together with the fronto-insular cortex, the ACC constitutes a network that is involved in switching between activations of different brain networks, thereby facilitating cognitive control.
Neurons in these brain regions have specific properties that enable a rapid relay of control signals to multiple areas of the rain to initiate responses during cognitively demanding tasks.

Neuroscientific findings on meditation practice

The ACC can be implicated in meditation.
There is an effect of meditation practice on ACC activity.

Although ACC activation might initially be enhanced when acquiring greater attentional control, it might later decrease with higher levels of expertise, when the focus of attention is so steady that monitoring distractions becomes superfluous.

Meditation practice might exert an influence on the ACC.
Cortical thickness in the dorsal ACC was greater in experienced meditators.

Clinical relevance

The strengthening of attention regulation and accompanying ACC performance through mindfulness practice is especially promising for the treatment of disorders that suffer from deficiencies in these functions.
Further research is needed to assess the effectiveness of mindfulness-based treatments on attention regulation in these disorders.

Effects of meditation practice on further components of attention

Effects of mindfulness have also been reported on other attention capacities

• Orienting
  Directing and limiting attention to a subset of possible inputs
• Altering
  Achieving and maintaining a vigilant state of preparedness

At a neurological level, this may relate to functional changes in the dorsal and ventral attention systems.
Early stages of mindfulness practice may lead to improvement in the function of the dorsal attention system involved in orienting, and more intensive open monitoring meditation may additionally result in improvements in the function of the ventral attention system involved in alerting.

3 months of intensive mindfulness meditation lead to a smaller attentional blink effect and modified distribution of brain resources.

Attention regulation seems to be an important mechanism that is often developed early in mindfulness practice.

Body awareness

Body awareness is the ability to notice subtle bodily sensations.
In mindfulness practice, the focus of attention is usually an object of internal experience.

Self-report findings

Practitioners self-report that the practice of attending to body sensations results in an enhanced awareness of bodily states and greater perceptual clarity of subtle interoception.

Behavioural findings

There has been no empirical evidence to verify of improved capability for body awareness.

Neuroscientific findings: functional neuroimaging

There are changes in the function and structure of brain regions related to body awareness.
The insula is commonly activated during tasks of interoceptive awareness, and its local gray matter volume correlates with interoceptive accuracy and visceral awareness.

Insula activation has been found to be increased in individuals after a mindfulness-based stress reduction course when they focused on their momentary experience.
There is also increased activation of the secondary somatosensory area, which is relevant for the processing of exteroceptive sensory events.

The enhanced sensory processing has been suggested to represent increased bottom-up processing of the stimulus.

Neuroscientific findings: structural neuroimaging

Meditators have greater cortical thickness and greater gray matter concentration in the right anterior insula. Also in the temporo-parietal junction. The temporo-parietal junction is a crucial structure for mediating the first-person perspective of bodily states, or embodiment.
Impaired processing at the temporoparietal junction may lead to the pathological experience of the self.

Morphological changes in the temporo-parietal junction might be associated with an increased awareness of the experience of oneself within the body.

Body awareness and emotion regulation

Body sensations have been ascribed a crucial role in the conscious experience of emotions, current and historically.
An increased awareness of the body’s response to an emotional stimulus might thus lead to greater awareness of one’s own emotional life. In turn, an awareness of one’s emotions is a precondition for being able to regulate those emotions.

Helping individuals increase their body awareness can be considered a relevant aspect in the treatment of psychological disorders.

Body awareness as empathy

Internal awareness of one’s own experience has been suggested to be an important precondition for emphatic responses.
Accurate observations of the self are required for the appropriate understanding of others.

A higher level of mindful observation has been found to be associated with more engagement in empathy.

A subset of brain regions is impacted both in awareness of one’s own body sensations and in social cognition and empathic responses.
Enhanced function of these structures following mindfulness training might also correspond to improved empathic responses and compassion attributed to meditation training.

Body sensations are a common object of attention during mindfulness meditation, and practitioners report improved body awareness. Although there have been no objective behavioural data supporting the increased awareness, neuroscientific data on mindfulness practice point to the modification of brain regions involved in first-person conscious experience of body awareness.

Emotion regulation

A growing body of literature suggests that mindfulness practice results in improvements in emotion regulation.
Emotion regulation is the alteration of ongoing emotional responses through the action of regulatory processes.

Behavioural and peripheral physiological findings

Mindfulness practice has an effect on the physiological aspects of positive emotions and thus positively influences emotional processing.

Neural mechanisms of emotion regulation

During emotion regulation, prefrontal control systems modulate emotion-generative systems, such as the amygdala.
These prefrontal structures include:

• Dorsal regions of the lateral prefrontal cortex
  Have been implicated in selective attention and working memory.
• Ventral parts of the PFC
  Implicated in response inhibition
• The ACC
  Involved in monitoring control processes
• Dorso-medial PFC
  Implicated in monitoring one’s affective state

A typical pattern detected when individuals deliberately regulate affective responses is increased activation within the PFC, and decreased activation in the amygdala.
PFC projections to the amygdala exert an inhibitory top-down influence.

Psychological disorders and emotion regulation

A variety of psychological disorders are associated with reduced emotion regulation capacity.
Disorders characterized by a deficit in emotion regulation are frequently associated with dysfunction in the frontal-limbic network (reduced prefrontal activation and exaggerated amygdala activation).

Neuroscientific findings on mindfulness and emotion regulation

A few neuroimaging studies have found increased prefrontal activation and improved prefrontal control over amygdala responses in association with mindfulness.
The observed improvements in emotion regulation associated with mindfulness practice likely underlie many of the positive effects of mindfulness practice on mental health.

Different strategies of emotion regulation

The exact processes underlying improvements on emotion regulation are not entirely clear.
There is a distinction between

• Behavioural regulation
  Suppressing expressive behaviour
• Cognitive regulation
  Relies on attentional control or on cognitive change

Cognitive change strategies include

• The controlled regulation of an ongoing emotional response such as
  • Reappraisal
    Reinterpreting the meaning of a stimulus to change one’s emotional response to it
  • Extinction
• Stimulus-response reversal

Attentional control plays a crucial role in mindfulness meditation.
Mindfulness usually involves brining attention to the stimulus.
Extinction plays a crucial role in producing the beneficial effects of mindfulness meditation.

Reappraisal

Reappraisal has been suggested to be one of the ways in which emotion gets regulated during mindfulness.
Mindful emotion regulation is the adaptive process through which stressful events are reconstrued as beneficial, meaningful, or benign.

Mindfulness practice leads to increases in positive reappraisal and these increases mediate an improvement in stress levels.

Neuroscientific findings

Cognitive reappraisal of aversive stimuli has been found to coincide with activity in the dorso-lateral PFC, orbitofrontal PFC, and ACC.
Dorsal PFC activity has been found to go along with reappraisal success.

Extinction processes may depend more upon ventral frontal systems that are directly connected with the subcortical systems.
Reappraisal may depend more on dorsal frontal systems.

Trait mindfulness seems to be positively associated with reappraisal success and with increased activation in brain regions that support this kind of emotion regulation.

Does mindfulness involve reappraisal or nonappraisal?

Whereas the acceptance of one’s emotional response is characterized by the absence of active cognitive control over the emotional reaction, bringing mindful awareness to emotional responses might initially require some cognitive control, in order to overcome habitual ways of internally reacting to one’s emotions.

Exposure, extinction and reconsolidation

During mindfulness, practitioners expose themselves to whatever is present in the field of awareness, including external stimuli as well as body sensations and emotional experiences.  
They let themselves be affected by the experience, refraining from engaging in internal reactivity toward it, and instead bringing acceptance to bodily and effective responses.

Practitioners are instructed to meet unpleasant emotions, by turning towards them, rather than turning away.
Mindfulness meditation includes refraining from engaging in cognitive avoidance or other safety behaviours by using enhanced attention regulation skills, thereby maximizing the exposure to the experienced emotion.

Meditation is often associated with high levels of relaxation in the form of increased parasympathetic tone and decreased sympathetic activity.
Mindfulness practice leads to the self-perception of decreased reactivity.
This is likely a mechanism for facilitating exposure.

Fear conditioning, extinction and reconsolidation

Fear conditioning is a learning process in which a neutral conditioned stimulus is paired with an aversive unconditioned stimulus.
After a few pairings, the presentation of the conditioned stimulus also comes to elicit various responses.

Repeated presentations of the conditioned stimulus in the absence of the unconditioned stimulus result in the extinction of the conditioned responses.
Extinction does not erase the initial association between conditioned and unconditioned stimuli but is thought to form a new memory trace or reconsolidate the old memory with new contextual associations.

After extinction training, extinction memory is thought to compete with conditioned memory for control of fear expression.

Extinction learning and its retention may be a critical process in the transformation of maladaptive states.
Individuals can flexibly elicit other adaptive emotional and behavioural responses.

Neural mechanisms of fear extinction and extinction retention

There is a network of brain regions that are crucial for the extinction of conditioned fear responses and its retention.
This network seems to strengthen through mindfulness practice.

The ventromedial prefrontal cortex (vmPFC) has been shown to be important for the successful recall of the extinction.
Hippocampus activation is involved in fear extinction recall.
The vmPFC and hippocampus comprise a network that mediates the expression of extinction memory in the appropriate context.

Hippocampal activation during extinction recall is likely related to signalling the extinguished context.

The amygdala plays a crucial role during the acquisition and expression of conditioned fear.
Including the detection of stressful and threatening stimuli and the initiation of adaptive coping responses.
When individuals regulate their emotions, the amygdala is thought to be down-regulated by the vmPFC and hippocampus. This inhibition of the amygdala suppresses fear, thereby allowing control over behavioural  reactions to emotions.

Effects of meditation practice on the neural network underlying extinction

The aforementioned brain regions show structural changes following mindfulness meditation training.
Meditators show greater gray matter concentration in the hippocampus.
There are striking similarities in the brain regions being influenced by mindfulness meditation and those involved in mediating fear extinction.
Mindfulness meditation could directly influence one’s capacity to extinguish conditioned fear by enhancing the structural and functional integrity of the brain network involved in safety signalling.

The impact of extinction processes within meditation practice

The extinction process plays a role in the improvements following mindfulness-based treatments.
Exposure is pursued toward whatever emotions present themselves. Extinction is effective during all of these emotional experiences, leading to an overwriting of previously learned stimulus-response associations.
Nonreactivity leads to unlearning of previous connections and thereby liberations from being bound to habitual emotional reactions.

Change in perspective on the self

The essence of Buddhist psychology lies in the teaching that there is no such thing as a permanent, unchanging self.
The perception of a self is a product of an ongoing mental process. This perception reoccurs very rapidly in the stream of mental events, leading to the impression that the self is a constant and unchanging entity.

When internal awareness becomes enhanced through meditation, meditators report that they can observe mental processes with increasing clarity and increasing temporal resolution.
Within this enhanced clarity, the process of a repeatedly arising sense of self becomes observable to the meditator through the development of meta-awareness.
Meta-awareness is a form of subjective experience and executive monitoring, in which one takes a nonconceptual perspective as a distributed from of attention toward the contents of conscious experience and the processes involved. It is not entangled in the contents of awareness and facilitates a detachment from identification with the static sense of self.

The self can be experienced as an event.

From the Buddhist perspective, identification with the static sense of self is the cause of psychological distress. Disidentification results in less afflictive experience and the freedom to experience a more genuine way of being.
A change in perspective on the self is the key in the process to enduring forms of happiness.

A de-identification form some parts of mental content is often experienced even in the earliest stages of meditation practice.
In mindfulness practice, all experiences are observed as they arise and pass. By closely observing the contents of consciousness, practitioners come to understand that these are in constant change and thus are transient.

The mindful, non-judgmental observation fosters a detachment from identification with the contents of consciousness.

Self-report findings

Self-report studies suggest that some beneficial changes in the perspective on the self can happen resulting from mindfulness meditation practice.

Neuroscientific findings: functional neuroimaging

Neuro-imaging studies of mindfulness meditation have demonstrated that brain structures that support self-referential processing are structurally and functionally impacted by mindfulness meditation.

Neuroscientific findings: structural neuroimaging

The posterior cingulate cortex, the temporo-partietal junction, and the hippocampus show increased gray matter concentration following mindfulness-based stress reduction.
Given the relevance of these brain structures for the experience of the self, it seems possible that the structural changes might be associated with changes in the perspective on the self.

Integration

The above described components are presumably highly interrelated.

Attention regulation appears to be a prerequisite for the other mechanisms to take place.
Focused attention on internal events is necessary in order for practitioners to gain an increased awareness of bodily sensations with the resultant ability to recognise the emergence of emotions. The ability to keep attention focused on conditioned stimuli is a prerequisite for the successful extinction of conditioned responses.
Enhanced body awareness might be closely related to the changes in the perspective on the self and might replace a narrative form of self-reference.
The change in perspective on the self may result in reappraisal of situations in specific ways, which might provide motivation for further development of attention regulation and body awareness.

As the components mutually facilitate each other, the process could be understood as an upward spiral process.

Self-compassion

Self-compassion entails three components

• Self-kindness
  Being kind and understanding toward oneself in instances of perceived inadequacy or suffering
• Common humanity
  Perceiving one’s experiences as part of the larger human experience
• Mindfulness
  Holding one’s painful thoughts and feelings in a balanced awareness

The relationship between self-compassion and mindfulness

Mindfulness and self-compassion are highly correlated.
It has been suggested that mindfulness is required in order for self-compassion to develop because the former enables one to clearly see mental and emotional phenomena as they arise.
Changes in mindfulness have been found to predict changes in self-compassion.

It has been suggested that self-compassion partially mediates the relationship between mindfulness and well-being.
The cultivation of self-compassion has been suggested to explain much of the success of mindfulness-based interventions.

The cultivation of self-compassion in meditation practice

Meditation is typically practiced with an intention (implicit or explicit) to cultivate self-compassion as well as compassion toward other beings.
In mindfulness-based stress reduction, even though it is not the declared primary goal of the program, self-compassion is implicitly and explicitly interwoven into meditation instruction.

Self-compassion within the theoretical framework proposed here

Self-compassion is presumably most related to emotion regulation as well as to the change in perspective on the self.
The generation of feelings of kindness toward oneself in instances of perceive inadequacy or suffering is an act of emotion regulation.
When cultivating self-compassion, seeing one’s difficult experiences as part of the larger human experience might initially require reappraisal. This might ultimately result in a change in the perspective on the self.