Cortland J Dahl

Antoine Lutz

Richard J Davidson
email: rjdavids@wisc.edu

Reconstructing and deconstructing the self: Cognitive mechanisms in meditation practice

Keywords: meditation, mindfulness, meta-awareness, experiential fusion, insight, self-inquiry Cognitive Mechanisms of Meditation Practice awareness, experiential fusion, self-schema, self-inquiry, and insight are discussed

Scientific research highlights the central role of specific psychological processes, in particular those related to the self, in various forms of human suffering and flourishing. This view is shared by Buddhism and other contemplative and humanistic traditions, which have developed meditation practices to regulate these processes. Building on a previous paper in this journal, we propose a novel classification system that categorizes specific styles of meditation into attentional, constructive, and deconstructive families based on their primary cognitive mechanisms. We suggest that meta-awareness, perspective taking and cognitive reappraisal, and self-inquiry may be important mechanisms in specific families of meditation and that alterations in these processes may be used to target states of experiential fusion, maladaptive self-schema, and cognitive reification.

meditation affect specific cognitive processes, nor how alterations in these processes might impact levels of well-being. Here, we address this question from the perspective of psychology and cognitive neuroscience to better understand how changes in well-being are mediated by alterations in distinct cognitive processes and in the structure and functioning of corresponding brain networks.

In a previous article in this journal, we proposed a preliminary framework to discuss commonly practiced forms of mindfulness meditation [START_REF] Lutz | Attention regulation and monitoring in meditation[END_REF]. Recent theoretical models have advanced our understanding further by attempting to identify potential cognitive and neural mechanisms in different forms of meditation and to classify different forms of contemplative practice [START_REF] Austin | Zen and the brain: mutually illuminating topics[END_REF][START_REF] Travis | Transcendental experiences during meditation practice[END_REF][START_REF] Josipovic | Neural correlates of nondual awareness in meditation[END_REF][START_REF] Kozhevnikov | The enhancement of visuospatial processing efficiency through buddhist deity meditation[END_REF][START_REF] Nash | Toward a unifying taxonomy and definition for meditation[END_REF][START_REF] Travis | Focused attention, open monitoring and automatic self-transcending: Categories to organize meditations from Vedic, Buddhist and Chinese traditions[END_REF]. While some models have proposed specific cognitive and biological processes that inform the practice of mindfulness meditation [START_REF] Holzel | How Does Mindfulness Meditation Work? Proposing Mechanisms of Action From a Conceptual and Neural Perspective[END_REF][START_REF] Vago | Self-awareness, self-regulation, and self-transcendence (S-ART): a framework for understanding the neurobiological mechanisms of mindfulness[END_REF][START_REF] Lutz | Investigating the Phenomenological Matrix of Mindfulness-related Practices from a Neurocognitive Perspective[END_REF], theoretical accounts of other families of meditation are lacking, especially models that identify important mechanisms in other styles of practice. Thus, while these pioneering efforts provide crucial insights for the scientific study of meditation, rigorous efforts to examine the psychological processes involved in different families of meditation are needed to understand the precise manner in which they might impact various aspects of well-being.

In this article we expand our original framework to accommodate a broader range of traditional and contemporary meditation practices, grouping them into attentional, constructive, and deconstructive families. According to this model, the primary cognitive mechanisms in these three families are (1) attention regulation and meta-awareness, (2) perspective taking and reappraisal, and (3) self-inquiry, respectively. To illustrate the role of these processes in different forms of meditation, we discuss how experiential fusion, maladaptive self-schema, and cognitive reification are differentially targeted by these processes in the context of Buddhist meditation, integrating the perspectives of other contemplative, philosophical, and clinical perspectives when relevant. The mechanisms and targets we propose are drawn from cognitive science and clinical psychology. Although these psychological processes are theoretically complex, as are the meditation practices that target them, we propose this novel framework as a first step in identifying specific cognitive mechanisms to aid in the scientific study of different families of meditation and the impact of these practices on well-being.

The Attentional Family: Meta-awareness and Experiential Fusion

The group of meditative practices that we refer to here as the 'attentional family' trains a variety of processes related to the regulation of attention. These include the capacities to manipulate the orientation and aperture of attention, to monitor, detect and disengage from distractors, and to re-orient attention toward a chosen object [START_REF] Lutz | Investigating the Phenomenological Matrix of Mindfulness-related Practices from a Neurocognitive Perspective[END_REF][START_REF] Jha | Mindfulness training modifies subsystems of attention[END_REF][START_REF] Hasenkamp | Mind wandering and attention during focused meditation: a fine-grained temporal analysis of fluctuating cognitive states[END_REF][START_REF] Tang | Short-term meditation training improves attention and self-regulation[END_REF]. We propose that a shared characteristic of all meditation practices in this family is the systematic training of the capacity to intentionally initiate, direct, and/or sustain these attentional processes while the strengthening the capacity to be aware of the processes of thinking, feeling, and perceiving (see Box 1 and Table 1).

In scientific literature, the term meta-awareness has been used to describe the cognitive function of being aware of the processes of consciousness [START_REF] Smallwood | The lights are on but no one's home: Meta-awareness and the decoupling of attention when the mind wanders[END_REF]. In the absence of meta-awareness, we become experientially "fused" with what we experience. We may be aware of the objects of attention, yet unaware of the processes of thinking, feeling, and perceiving. This state of experiential fusion has been referred to using a variety terms in the study of meta-cognition, including "cognitive fusion" and "object mode" [START_REF] Wells | Emotional disorders and metacognition: Innovative cognitive therapy[END_REF][START_REF] Hayes | Acceptance and Commitment Therapy, Relational Frame Theory, and the Third Wave of Behavioral and Cognitive Therapies[END_REF].

To illustrate the difference between meta-awareness and experiential fusion, let us consider an example. Imagine that you are watching an enthralling movie. In one moment, you might be experientially fused with the movie, to the point when you are no longer consciously aware that you are sitting in a movie theater. In the next moment, you might suddenly become aware of your surroundings and the fact that you are viewing images on a screen. In both moments you may be attentive to the movie, but only in the second moment are you also aware of the process of watching the movie.

In this example, paying attention to the images and sounds that constitute the movie is a form of awareness. If someone tapped you on the shoulder and asked you what just happened in the movie, you could answer. However, if you were asked whether or not you were conscious of sitting in a movie theater in the moment before being asked, you would probably answer no. The awareness that you were watching a movie, in this case, would only be retrospective. Across a range of traditional and contemporary contemplative traditions, the absence of meta-awareness is viewed as an impediment to various forms of self-monitoring, self-regulation, and self-inquiry [START_REF] Hadot | Philosophy as a way of life: Spiritual exercises from Socrates to Foucault[END_REF][START_REF] Gethin | On some definitions of mindfulness[END_REF][START_REF] Mccracken | Decentering, rumination, cognitive defusion, and psychological flexibility in people with chronic pain[END_REF].

Experiential Fusion and the Training of Attention

The inability to regulate attentional processes has been linked to ADHD [START_REF] Castellanos | Characterizing cognition in ADHD: Beyond executive dysfunction[END_REF], addiction [START_REF] Waters | Attentional bias to drug cues is elevated before and during temptations to use heroin and cocaine[END_REF], and other forms of psychopathology [START_REF] Van Bockstaele | A review of current evidence for the causal impact of attentional bias on fear and anxiety[END_REF][START_REF] Cohen | Impairments of attention and effort among patients with major affective disorders[END_REF], as well as to abnormalities in brain structure and function [START_REF] Castellanos | Large-scale brain systems in ADHD: Beyond the prefrontal-striatal model[END_REF]. Experiential fusion in particular has received a great deal of attention in a number of contemporary therapeutic interventions. Although associated with overlapping constructs, including "cognitive distancing," "cognitive defusion," and "decentering," reversing states of experiential fusion through the cultivation of meta-awareness is considered to be especially important in the cultivation of mental health [START_REF] Hayes | Acceptance and Commitment Therapy, Relational Frame Theory, and the Third Wave of Behavioral and Cognitive Therapies[END_REF][START_REF] Linehan | Dialectical Behavior Therapy for patients with borderline personality disorder and drug-dependence[END_REF][START_REF] Segal | Mindfulness-based cognitive therapy for depression[END_REF][START_REF] Kabat-Zinn | Full catastrophe living: Using the wisdom of your body and mind to face stress, pain, and illness[END_REF][START_REF] Butler | The empirical status of cognitive-behavioral therapy: a review of meta-analyses[END_REF].

Clinical studies have shown that a diminished ability to step back and observe one's internal processes of thinking and feeling plays an important role in a variety of psychiatric conditions, including depression [START_REF] Lo | Decentering Mediates the Effect of Ruminative and Experiential Self-Focus on Negative Thinking in Depression[END_REF] and anxiety [START_REF] Hoge | Change in Decentering Mediates Improvement in Anxiety in Mindfulness-Based Stress Reduction for Generalized Anxiety Disorder[END_REF]. In one recent study, authors found that decreases in psychological processes related to experiential fusion were found in patients undergoing treatment for depression who received training in mindfulness-based cognitive therapy but not in control groups, and that these changes were associated with positive changes in depressive symptomology [START_REF] Bieling | Treatment-specific changes in decentering following mindfulness-based cognitive therapy versus antidepressant medication or placebo for prevention of depressive relapse[END_REF]. Similar findings have been found in relation to the treatment of addiction [START_REF] Brewer | Craving to Quit: Psychological Models and Neurobiological Mechanisms of Mindfulness Training as Treatment for Addictions[END_REF]. A study on smoking cessation, for example, demonstrated that mindfulness practice attenuated cigarette smoking, in particular by altering the relationship between addictive craving and the behavior of smoking [START_REF] Elwafi | Mindfulness training for smoking cessation: Moderation of the relationship between craving and cigarette use[END_REF].

As recently reviewed, mindfulness-related practices have been shown to train many of the attentional processes described above and to induce functional and structural changes in attention-related networks in the brain [START_REF] Tang | The neuroscience of mindfulness meditation[END_REF][START_REF] Fox | Is meditation associated with altered brain structure? A systematic review and meta-analysis of morphometric neuroimaging in meditation practitioners[END_REF]. For instance, there is growing evidence that attentional stability increases with mindfulness training, as measured by reduced response time variability and EEG brain response variability during continuous performance tasks [START_REF] Maclean | Intensive meditation training improves perceptual discrimination and sustained attention[END_REF][START_REF] Lutz | Mental training enhances attentional stability: neural and behavioral evidence[END_REF]. Similarly, intensive meditation training has been shown to reduce both behavioral and EEG markers of attentional blink, a phenomena that reflects the propensity for attention to become fused with a perceptual target [START_REF] Slagter | Mental training affects distribution of limited brain resources[END_REF]. This effect is also modulated by different forms of meditation, with enhanced reductions in attentional blink in relation to open monitoring meditation relative to focused attention practices [START_REF] Van Vugt | Control over experience? Magnitude of the attentional blink depends on meditative state[END_REF] (see Box 1). Reducing experiential fusion with emotional experiences should facilitate the regulation of emotions by decreasing their perseveration. This prediction is in line with findings that expert meditators exhibited less amygdala activity in response to negative emotional stimuli relative to controls [START_REF] Brefczynski-Lewis | Neural correlates of attentional expertise in long-term meditation practitioners[END_REF]. A similar effect was found when patients with anxiety disorders underwent a training in mindfulness meditation [START_REF] Goldin | Effect of Mindfulness Meditation Training on the Neural Bases of Emotion Regulation in Social Anxiety Disorder[END_REF].

One avenue through which meta-awareness might impact well-being lies in its relationship to mind wandering. Mind wandering has been found to consume as much as 50% of our waking life and is tied to our sense of well-being [START_REF] Killingsworth | A wandering mind is an unhappy mind[END_REF]. If training in attentional forms of meditation does strengthen meta-awareness, we might expect this to impact both the incidence and impact of mind wandering. Recent studies have indeed found that meditation training alters patterns of task-unrelated thought, showing that even brief trainings in mindfulness meditation decrease the behavioral indicators of mind wandering [START_REF] Mrazek | Mindfulness and mind-wandering: finding convergence through opposing constructs[END_REF][START_REF] Levinson | A mind you can count on: validating breath counting as a behavioral measure of mindfulness[END_REF]. Although meta-awareness and self-referential processes are difficult to operationalize, a few recent studies seem to indicate that brain regions associated with self-referential processing [START_REF] Mason | Wandering minds: the default network and stimulus-independent thought[END_REF][START_REF] Fox | The wandering brain: Meta-analysis of functional neuroimaging studies of mindwandering and related spontaneous thought processes[END_REF][START_REF] Christoff | Experience sampling during fMRI reveals default network and executive system contributions to mind wandering[END_REF], such as the medial prefrontal cortex and the posterior cingulate cortex, may be down-regulated by mindfulness-related practices [START_REF] Farb | Attending to the present: mindfulness meditation reveals distinct neural modes of self-reference[END_REF][START_REF] Brewer | Meditation experience is associated with differences in default mode network activity and connectivity[END_REF]. In one of these studies, this pattern was linked to enhanced coupling between these midline regions and attentional brain networks associated with executive function, such as the dorsolateral prefrontal cortex and the dorsal anterior cingulate cortex [START_REF] Brewer | Meditation experience is associated with differences in default mode network activity and connectivity[END_REF]. In the other, this pattern was linked to a decreased coupling between the medial prefrontal cortex and an interoceptive region, the insular cortex [START_REF] Farb | Attending to the present: mindfulness meditation reveals distinct neural modes of self-reference[END_REF]. It was speculated that these patterns reflected decreased self-referential thought and enhanced present-centered awareness [START_REF] Farb | Attending to the present: mindfulness meditation reveals distinct neural modes of self-reference[END_REF][START_REF] Brewer | Meditation experience is associated with differences in default mode network activity and connectivity[END_REF]. These interpretations require further investigation, particularly because mind-wandering recruits multiple brain regions, some of which may also play roles in attention and interoception [START_REF] Fox | The wandering brain: Meta-analysis of functional neuroimaging studies of mindwandering and related spontaneous thought processes[END_REF]. It is also unclear how metaawareness affects one's ability to use the constructive aspects of mind wandering more effectively, and how activation patterns in brain regions associated with self-referential thought change when periods of mind wandering coincide with meta-awareness.

The Constructive Family: Reappraisal, Perspective Taking, and Self-

Schema

The style of practice that we refer to as the 'constructive family' includes a variety of meditation practices that strengthen psychological patterns that foster well-being. We propose that one avenue through which these practices may affect well-being is by targeting maladaptive self-schema and replacing them with more adaptive conceptions of self. In cognitive psychology, latent beliefs and conceptions about the self, referred to as selfschema, are thought to underlie and inform thoughts and emotions [START_REF] Beck | The Current State of Cognitive Therapy[END_REF] and to impact patterns of brain function [START_REF] Disner | Neural mechanisms of the cognitive model of depression[END_REF]. In contrast to attentional practices, which often focus on simply monitoring cognitive and affective patterns, constructive meditations involve systematically altering the content of thoughts and emotions. Some constructive practices are designed to cultivate qualities like patience and equanimity that safeguard the mind from the stressors of daily life. Others aim to bring about a restructuring of priorities and values and a reorienting of the mind toward what is truly meaningful in life. Still more address interpersonal relationships by nurturing pro-social qualities like kindness and compassion (see Box 2 and Table 1).

The wide variety of practices in this family, as well as their individual complexity, makes identifying core cognitive mechanisms challenging. Nevertheless, a number of processes appear to be central to a broad spectrum of constructive meditations. Two mechanisms that appear to be especially important in this family are cognitive reappraisal and perspective taking. Cognitive reappraisal refers to the process of changing how we think about situations and events in such a way that our response to them is altered [START_REF] Gross | Emotion Regulation in Adulthood: Timing Is Everything[END_REF]. Reappraisal is an important strategy in the regulation of emotion [START_REF] Webb | Dealing with feeling: A meta-analysis of the effectiveness of strategies derived from the process model of emotion regulation[END_REF] and recruits brain regions related to cognitive control, including the dorsomedial, dorsolateral, and ventrolateral prefrontal cortex, as well as the posterior parietal cortex [START_REF] Buhle | Cognitive Reappraisal of Emotion : A Meta-Analysis of Human Neuroimaging Studies[END_REF]. In a study of reappraisal in those with social anxiety disorder (SAD), for example, results showed that the use of reappraisal reduced negative affect in both patients with SAD and healthy controls, but that in healthy controls different patterns of activity in regulatory brain regions were associated with reduced amygdala activity compared to SAD patients [START_REF] Goldin | Neural Mechanisms of Cognitive Reappraisal of Negative Self-Beliefs in Social Anxiety Disorder[END_REF].

The second core process that we propose to be central in many constructive meditations is that of perspective taking, the act of considering how oneself or another would feel in a particular situation [START_REF] Lamm | The neural substrate of human empathy: effects of perspective-taking and cognitive appraisal[END_REF]. Perspective taking is especially important as a contributor to the experience of social emotions [START_REF] Ruby | How Would You Feel versus How Do You Think She Would Feel ? A Neuroimaging Study of Perspective-Taking with Social Emotions[END_REF]. As a critical component of healthy interpersonal relationships, for instance, it is found to be diminished in psychopaths [START_REF] Decety | An fMRI study of affective perspective taking in individuals with psychopathy: imagining another in pain does not evoke empathy[END_REF] and also a central mediator in reducing intergroup prejudice [START_REF] Pettigrew | How does intergroup contact reduce prejudice? Meta-analytic tests of three mediatorsy[END_REF]. Imaging studies indicate that there is no single neural mechanism related to perspective taking, but rather that differences in perspective (imagining oneself experiencing pain versus another experiencing pain, for example) recruit different brain networks [START_REF] Ruby | How Would You Feel versus How Do You Think She Would Feel ? A Neuroimaging Study of Perspective-Taking with Social Emotions[END_REF].

In constructive meditation practices, cognitive reappraisal and perspective taking are hypothesized to be important mechanisms used to target maladaptive or neutral psychological processes and replace them with more adaptive patterns. One common example is the transformation of empathy into compassion (see Box 3). Hearing a crying baby on an airplane, for example, might first elicit a feeling of distress followed by aversion. This experience can be transformed by taking the perspective of the baby's mother, thereby triggering a sense of warmth and compassion, and also by reinterpreting the sound of the baby's cries, viewing the experience as an opportunity to cultivate kindness and concern rather than an impediment to one's own well-being. By systematically cultivating compassion in this manner, responding to aversive stimuli with altruistic concern may eventually become automatic. Such changes may thus be studied within the framework of habit formation, which is associated with various facets of physical and psychological wellbeing [START_REF] Lally | Promoting habit formation[END_REF].

To date, constructive meditation practices have received less attention than other forms of meditation in scientific research, though a few studies have begun to explore practices related to this family, including the cultivation of compassion [START_REF] Mascaro | Compassion meditation enhances empathic accuracy and related neural activity[END_REF][START_REF] Klimecki | Differential pattern of functional brain plasticity after compassion and empathy training[END_REF] and imagination-based meditations [START_REF] Kozhevnikov | The enhancement of visuospatial processing efficiency through buddhist deity meditation[END_REF]. The precise role that reappraisal and perspective taking play in constructive styles of meditation is therefore not yet known, nor is it clear how these processes relate to the recruitment of specific brain networks. Nevertheless, investigations of the cultivation of compassion, a widely practiced style of meditation in this family, provide useful information regarding the cognitive and neural mechanisms of constructive meditations. Preliminary findings indicate that this practice may affect the regulation of emotion and corresponding brain networks (see Box 3). Though further work is needed to clarify the role of reappraisal and perspective taking in other forms of constructive meditation, these data suggest one possible mechanism through which specific forms of meditation may impact well-being.

Deconstructive Family: Self-inquiry and Insight

The group of meditations that we refer to as the 'deconstructive family' aims to undo maladaptive cognitive patterns by exploring the dynamics of perception, emotion, and cognition and generating insights into one's internal models of the self, others, and the world. We propose that a central mechanism in the deconstructive family is self-inquiry, which we define as the process of investigating the dynamics and nature of conscious experience. Though self-inquiry has received little attention as a subject of scientific research, various forms of inquiry are employed across a range of contemplative traditions [START_REF] Maharshi | Be as you are: The teachings of Sri Ramana Maharshi[END_REF][START_REF] Karr | Contemplating Reality: A Practitioner's Guide to the View in Indo-Tibetan Buddhism[END_REF][START_REF] Buddhaghosa | The Path of Purification[END_REF]. Self-inquiry may involve discursive analysis or a direct examination of conscious experience, and often involves explorations of self-related processes (see Box 4 and Table 1). Discursive analysis might entail identifying the assumptions that underlie the reification of a particular object or experience and subsequently thinking about and questioning the logical consistency of these assumptions. If you are anxious, for example, you might identify the fearful assumptions that underlie the emotion and then inquire into the rational basis for your beliefs. Another approach would be to directly examine your experience, for example by dissecting the feeling of anxiety into its component parts and noticing how the thoughts, feelings, and physical sensations that comprise the emotion are constantly changing. In the context of Buddhist meditation, this process of inquiry is often applied to beliefs about the self, though it can similarly be applied to the nature and dynamics of perception, to the unfolding of thoughts and emotions, or to the nature of awareness.

In the deconstructive family, self-inquiry is practiced in order to elicit insight. Insight has been framed as a shift in consciousness, often sudden, that involves a feeling of knowing, understanding, or perceiving something that had previously eluded one's grasp [START_REF] Kounios | The cognitive neuroscience of insight[END_REF]. Scientific studies of this phenomena have focused on the burst of understanding that can occur in relation to solving simple mathematic or semantic problems [START_REF] Bowden | Aha! Insight experience correlates with solution activation in the right hemisphere[END_REF]. Research has found that this form of insight is linked to hemispheric differences in the brain, with recent studies demonstrating that facilitatory direct current stimulation of the right frontal-temporal cortex along with inhibitory stimulation of the corresponding region in the left hemisphere greatly enhanced insight-based problem solving capacity [START_REF] Chi | Facilitate insight by non-invasive brain stimulation[END_REF][START_REF] Chi | Brain stimulation enables the solution of an inherently difficult problem[END_REF]. To date, the scientific study of insight has not investigated forms of insight that may arise through self-inquiry, nor has there been a systematic investigation of the relationship between insight and well-being. This is an area that calls for future research, especially since a variety of meditative traditions hold that specific forms of insight, such as insight into the nature of the self, are of particular importance when it comes to the cultivation of well-being [START_REF] Hadot | Philosophy as a way of life: Spiritual exercises from Socrates to Foucault[END_REF][START_REF] Maharshi | Be as you are: The teachings of Sri Ramana Maharshi[END_REF][START_REF] Harvey | The Selfless Mind: Personality, Consciousness, and Nirvana in Early Buddhism[END_REF].

In Buddhist meditation practice, insights that would ordinarily be fragile and fleeting are systematically stabilized and integrated with one's experience, first in formal meditation and subsequently in daily life. The heightened awareness of present-moment experience cultivated through attentional meditations and the self-inquiry carried out in deconstructive meditations are thus considered important, though distinct, processes [START_REF] Gethin | The Foundations of Buddhism[END_REF]. To give an example of the relationship between these two processes, consider the feeling of being overcome by anger. When your sense of self is fused with the presence of anger (i.e., the feeling "I am angry"), the arising of anger is not seen clearly, but instead forms the lens through which you view experience. Attentional family practices train the capacity to recognize the occurrence of anger and other states of mind, enabling one to notice the presence of angry thoughts, physiological changes, and shifts in affective tone. This process of sustained recognition allows for the investigation of the experience of anger, an approach taken with deconstructive meditations. With this added element, one is not merely sustaining awareness of the experience of anger, but also investigating its various components, inquiring into its relationship with one's sense of self, and/or uncovering the implicit beliefs that inform the arising of anger and then questioning the validity of these beliefs in light of present-moment experience (see Box 4). This investigation of conscious experience is said to elicit an experience of insight, a flash of intuitive understanding that can be stabilized when linked with meta-awareness. Thus, meta-awareness sets the stage for self-inquiry and allows for the stabilization of the insight it generates while nevertheless being a distinct process.

To date, only one study has investigated the relationship between meditation training and insight. Though the form of meditation used in the study was not deconstructive in nature, results showed that short-term meditation training increased creative problem solving relative to training in progressive muscle relaxation [START_REF] Ding | Short-term meditation modulates brain activity of insight evoked with solution cue[END_REF]. This difference, moreover, was linked to heightened activation in a variety of brain regions, including the right cingulate gyrus, insula, putamen, and inferior frontal gyrus, and the bilateral middle frontal gyrus, inferior parietal lobule, and superior temporal gyrus [START_REF] Ding | Short-term meditation modulates brain activity of insight evoked with solution cue[END_REF]. Further study is needed to determine if specific forms of meditation, and deconstructive meditations in particular, enhance the capacity to arouse and sustain insight, and also to investigate the psychological and biological correlates of insight experiences. Thus, studying the relationship between different forms of meditation and well-being calls for a more comprehensive account of the varieties of insight, their neural correlates, and the conditions and interventions that may facilitate their occurrence.

Self-related Processing and the Brain

As noted above, inquiring into the nature of the self is an important practice in a variety of contemplative traditions, including both Buddhist meditation and Greco-Roman contemplative exercises [START_REF] Hadot | Philosophy as a way of life: Spiritual exercises from Socrates to Foucault[END_REF][START_REF] Harvey | The Selfless Mind: Personality, Consciousness, and Nirvana in Early Buddhism[END_REF]. One of the most compelling aspects of our sense of self is the ongoing personal narrative that weaves together the various aspects of our lives into a coherent, unified experience. This inner interpreter has been linked to activity in the left cerebral hemisphere in split brain patients [START_REF] Gazzaniga | Forty-five years of split-brain research and still going strong[END_REF] and to activity in the medial prefrontal cortex and posterior cingulate cortex in brain imaging research [START_REF] Denny | A meta-analysis of functional neuroimaging studies of self-and other judgments reveals a spatial gradient for mentalizing in medial prefrontal cortex[END_REF][START_REF] Lemogne | Negative affectivity, self-referential processing and the cortical midline structures[END_REF][START_REF] Brewer | What about the "Self" is Processed in the Posterior Cingulate Cortex? Front[END_REF]. The narrative self can be contrasted with the first person subjective experience that is not extended in time. This aspect of selfhood has been referred to as the "minimal self" [START_REF] Gallagher | Philosophical conceptions of the self: implications for cognitive science[END_REF] and "minimal phenomenal self" [START_REF] Blanke | Full-body illusions and minimal phenomenal selfhood[END_REF] and has been hypothesized to be instantiated in cortical activity in regions related to interoception, such as the anterior insula [START_REF] Seth | Interoceptive inference, emotion, and the embodied self[END_REF][START_REF] Critchley | Will studies of macaque insula reveal the neural mechanisms of selfawareness?[END_REF][START_REF] Craig | How do you feel--now? The anterior insula and human awareness[END_REF], in the temporo-parietal junction [START_REF] Ionta | Multisensory Mechanisms in Temporo-Parietal Cortex Support Self-Location and First-Person Perspective[END_REF], as well as in the hypothalamus, brainstem, and other subcortical regions associated with homeostatic functioning [START_REF] Damasio | Self comes to mind: Constructing the conscious brain[END_REF].

As there is still a paucity of empirical evidence relating to deconstructive meditation practices and their impact on neural processes, this is an area that calls for more intensive study in the future. Some data highlight the possibility of using meditation to willfully manipulate core aspects of identity [START_REF] Brewer | Meditation experience is associated with differences in default mode network activity and connectivity[END_REF][START_REF] Lutz | Long-term meditators self-induce high-amplitude gamma synchrony during mental practice[END_REF][START_REF] Josipovic | Influence of meditation on anti-correlated networks in the brain[END_REF], though it is not clear whether insight into the nature of experience disrupts rigid and/or maladaptive self-related processes, nor is it clear how alterations of these processes might be instantiated in the brain. Nevertheless, there does appear to be some overlap between the insights that are said to arise in forms of meditation that explore the nature of the self and recent research in the arena of cognitive neuroscience, which suggests that self-processing in the brain is not instantiated in a particular region or network, but rather extends to a broad range of fluctuating neural processes that do not appear to be self-specific [START_REF] Legrand | What is self-specific? Theoretical investigation and critical review of neuroimaging results[END_REF][START_REF] Gillihan | Is self special? A critical review of evidence from experimental psychology and cognitive neuroscience[END_REF]. Future studies may explore this convergence by using contemplative practices, and specifically those from the deconstructive family, to probe the malleability of self-related processes, their instantiation in the brain, and their relationship to both suffering and well-being.

Concluding Remarks and Future Directions

Scientific research on the effects of meditation is in the very early stages. Though preliminary findings suggest that meditation and other forms of mental training may produce demonstrable changes in subjective experience, behavior, patterns of neural activity, and peripheral biology, rigorous studies are still needed to uncover the precise mechanisms that underlie these changes. In particular, randomized trials, active control groups, and longitudinal studies that examine within-and across-subject changes over time, as well as across-practice comparisons, will be especially important in determining the efficacy of meditation training paradigms. In addition, subjective, behavioral, and clinical correlates of meditation-related neural changes are needed to assess the impact of different styles of meditation.

The framework presented here highlights the need to expand the scope of scientific research to include a broad range of meditation practices. In the same way that the study of mindfulness meditation has provided a unique window into the training of specific forms of attention, and the impact of attentional training on emotion regulation, learning and memory, and various forms of psychopathology, other forms of meditation may similarly yield important insights into the regulation of self-related processes and their import for wellbeing, health, and peripheral biology.

It is important to note that here we have explored these families through the lens of cognitive neuroscience and clinical psychology, focusing our attention on the primary cognitive mechanisms and phenomenological targets of specific forms of meditation. If, however, we are to fully understand these practices, it will also be important to study the wider context within which these practices are engaged. This context includes, but is certainly not limited to, issues of ethics (see Box 2), embodiment, inter-personal dynamics, cultural setting, and the role that belief and expectation play in shaping subjective experience. In providing this framework, inadequate though it may be, we hope to spur further discussion about the nature of contemplative practice and how scientific study of meditation may help us better understand the causes and conditions of human flourishing.

Supplementary Material

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Glossary of Terms

Attentional Family

A class of meditation practices that strengthen the self-regulation of various attentional processes, especially the ability to initiate and sustain meta-awareness. Some forms of meditation in this family involve a narrowing of attentional scope, while others involve releasing attentional control and bringing awareness to whatever enters the field of consciousness.

Cognitive Reification

The experience of thoughts, emotions, and perceptions as being accurate depictions of reality, and in particular the implicit belief that the self and objects of consciousness are inherently enduring, unitary, and independent of their surrounding conditions and circumstances. In the Buddhist tradition, cognitive reification is a primary target in deconstructive styles of meditation.

Constructive Family

A family of meditation practices that allow one to cultivate, nurture, or strengthen cognitive and affective patterns that foster well-being. Practices in this family may aim to promote healthy interpersonal dynamics, to strengthen a commitment to ethical values, or to nurture habits of perception that lead to enhanced well-being. Perspective taking and cognitive reappraisal are important mechanisms in this style of meditation.

Experiential Fusion

An automatic process whereby one becomes absorbed in the contents of consciousness, leading to a diminished capacity to monitor and/or regulate psychological processes. In attentional styles of meditation this process is systematically undermined through the cultivation of meta-awareness and the regulation of attention. Experiential fusion is also indirectly undermined in the constructive and deconstructive families.

Deconstructive Family

A family of meditation practices that employs self-inquiry to foster insight into the processes of perception, emotion, and cognition. Deconstructive meditation practices may be oriented toward the objects of consciousness or toward consciousness itself.

Insight

A shift in consciousness that is often sudden and involves a feeling of knowing, understanding, or perceiving something that had previously eluded one's grasp. In deconstructive meditation practices, insight is often elicited through self-inquiry and pertains to specific self-related psychological processes that inform well-being.

Meta-awareness

Heightened awareness of the processes of consciousness, including the processes of thinking, feeling, and perceiving. Along with the regulation of the scope and stability of attention, the cultivation of meta-awareness is an important objective in attentional styles of meditation practice. It is also strengthened indirectly in the constructive and deconstructive families.

Mindfulness

A term that is defined differently in Buddhist and contemporary contexts, but which often refers to a self-regulated attentional stance oriented toward present-moment experience that is characterized by curiosity, openness, and acceptance. In some traditional Buddhist contexts, mindfulness is equivalent to the psychological process that we refer to here as meta-awareness.

Perspective Taking

The process of considering how one or another would think or feel in a particular situation.

Re-appraisal

The process of changing how one thinks or feels about situations and events in such a way that one's response to them is altered.

Self-inquiry

The investigation of the dynamics and nature of conscious experience, particularly in relation to thoughts, feelings, and perceptions that pertain to one's sense of self. Self-inquiry may be an important mechanism in deconstructive meditations due to its role in facilitating insight.

Self-schema

Mental representations of the self that synthesize information from sensory, affective and/or cognitive domains. Constructive styles of meditation often involve developing and/or strengthening adaptive self-schema.

Box 1. Forms of Attentional Meditation

In both traditional and clinical contexts, the capacity to sustain a heightened awareness of thoughts, behaviors, emotions, and perceptions is thought to be a central feature of mindfulness meditation [START_REF] Holzel | How Does Mindfulness Meditation Work? Proposing Mechanisms of Action From a Conceptual and Neural Perspective[END_REF][START_REF] Lutz | Investigating the Phenomenological Matrix of Mindfulness-related Practices from a Neurocognitive Perspective[END_REF][START_REF] Gethin | On some definitions of mindfulness[END_REF][START_REF] Bishop | Mindfulness : A Proposed Operational Definition[END_REF][START_REF] Shapiro | Mechanisms of Mindfulness[END_REF][START_REF] Kabat-Zinn | The clinical use of mindfulness meditation for the self-regulation of chronic pain[END_REF]. Though there is considerable discussion concerning the exact nature of mindfulness practice and its relationship to the construct of mindfulness in traditional Buddhist frameworks [START_REF] Gethin | On some definitions of mindfulness[END_REF][START_REF] Dreyfus | Is mindfulness present-centred and non-judgmental? A discussion of the cognitive dimensions of mindfulness[END_REF][100][101][102], there is general agreement that the cognitive process that we refer to here as meta-awareness plays a central role across a broad spectrum of meditation practices. Following our prior categorization [START_REF] Lutz | Attention regulation and monitoring in meditation[END_REF], here we propose two main categories of attentional meditation, along with two new subcategories that allow for a more nuanced discussion of different styles of practice in this family.

Focused attention (FA) practices involve a narrowing of attentional scope and the cultivation of one-pointed concentration on a single object [START_REF] Lutz | Attention regulation and monitoring in meditation[END_REF][START_REF] Brefczynski-Lewis | Neural correlates of attentional expertise in long-term meditation practitioners[END_REF]. The presence of metaawareness distinguishes the attentional stability achieved through this form of meditation from other forms of absorption, such as the stable attentiveness that occurs when one is engaged in an engrossing conversation or playing an interesting game. Open monitoring (OM) practices similarly involve the cultivation of meta-awareness, but they do not involve selecting a specific object to orient one's attention. Rather, attentional scope is expanded to incorporate the flow of perceptions, thoughts, emotional content, and/or subjective awareness. OM meditation can be further divided into object-oriented open monitoring, which involves directing one's attention to whatever thoughts, percepts, and sensations enter the field of awareness, and awareness-oriented open monitoring, referring to the sustained recognition of the knowing quality of awareness itself. Both forms of open monitoring meditation are similar in many ways to practices discussed below in the context of the deconstructive family. What distinguishes them from deconstructive forms of meditation is that their primary objective is the stabilization of meta-awareness in relation to a particular attentional configuration. As we will see below, in the deconstructive family a similar configuration of attention may be employed, but for different purposes (such as the cultivation of insight into the nature of sensory experience, for example).

Box 2. Ethics and Forms of Constructive Meditation

The cultivation of virtuous qualities is a common pursuit in many contemplative and philosophical traditions [START_REF] Hadot | Philosophy as a way of life: Spiritual exercises from Socrates to Foucault[END_REF][START_REF] Gethin | The Foundations of Buddhism[END_REF]103]. The constructive family of meditation is one important method that allows for this cultivation. While practices in this family necessitate the presence of meta-awareness, and also serve to strengthen and sustain meta-awareness, the approach taken in this family is markedly different from practices in the attentional family, insofar as this style of practice involves actively changing cognitive and affective content, as opposed to simply observing or noting the presence of thoughts, emotions, and perceptions.

Though there are many different styles of constructive meditation, we have identified three important subgroups, which we refer to as the relationship orientation, values orientation, and perception orientation. The relationship orientation emphasizes nurturing harmonious relationships with others. In Buddhist meditation, this style of practice often involves the extension of kindness and compassion first to specific individuals, and eventually to all beings [104]. This subgroup of meditation may impact specific psychological factors, by decreasing in-group bias, for example [105], and thereby enhance important dimensions of well-being such as positive relationships and meaning in life [START_REF] Ryff | Psychological well-being revisited: advances in the science and practice of eudaimonia[END_REF].

Practices in the values orientation subgroup involve the integration of ethical frameworks or values into one's ongoing perspective. One common practice in this subgroup is the contemplation of one's own mortality, which is found in Buddhist practice as well as in Greco-Roman philosophy. In Platonic philosophy, for example, contemplations of death functioned to bring the individual into contact with a sense of self that transcends the boundaries and needs of the physical body [START_REF] Hadot | Philosophy as a way of life: Spiritual exercises from Socrates to Foucault[END_REF], while in Buddhism contemplating the fragility and fleeting nature of life is often intended to reorient the mind toward what is truly meaningful in life [106].

Practices that involve a perception orientation aim to alter perceptual habits as a way to induce shifts in implicit self-schema. A common practice in Tibetan Buddhism, for example, is the so-called "development stage" [107], a form of meditation that aims to alter both the perception of sensory objects as well as the subjective perspective itself. This perceptual shift may instantiated by imagining oneself to be the embodiment of compassion, for instance, and viewing other individuals and one's environment from that perspective. Preliminary data suggests that this practice may enhance one's ability to access heightened visuospatial processing resources [START_REF] Kozhevnikov | The enhancement of visuospatial processing efficiency through buddhist deity meditation[END_REF].

Box 3. Empathy, Compassion, and the Brain

One of the most widely studied practices in the constructive family is the cultivation of compassion. [122,123]. These findings suggest that the mind can be trained to orient itself toward the well-being of others and that this shift from self-to other-orientation impacts both the brain and the peripheral biology of the body, and in particular the way the body responds to environmental stressors. Further research is required to elucidate the precise mechanisms through which these states affect the body, and also to investigate how changes in peripheral biology reciprocally impact psychological processes and the relationship between these processes and well-being.

Box 4. Cognitive Reification and Forms of Deconstructive Meditation

The deconstructive family represents a range of meditation practices that employ selfinquiry to elicit insight into in the nature and dynamics of conscious experience. We have identified three subgroups of the deconstructive family: object-oriented insight, subjectoriented insight, and non-dual-oriented insight. Object-oriented insight practices employ self-inquiry to investigate the objects of consciousness. This may involve, for example, investigating physical sensations and noting how they are constantly changing [102]. Subject-oriented insight practices involve inquiries into the nature of thought, perception, and other cognitive and affective processes. In this style of practice one may, for instance, dissect thoughts and emotions into their component parts [START_REF] Karr | Contemplating Reality: A Practitioner's Guide to the View in Indo-Tibetan Buddhism[END_REF]. Non-dual practices are designed to elicit an experiential shift into a mode of experiencing in which the cognitive structures of self/other and subject/object are no longer the dominant mode of experience. These practices often emphasize the importance of releasing attempts to control, direct, or alter the mind in any way and also serve to undo the reification of a witnessing "observer" that is separate from the objects of awareness [START_REF] Josipovic | Neural correlates of nondual awareness in meditation[END_REF]100]. The goal of all three styles of practice in the deconstructive family is not simply to maintain awareness of different aspects of experience, as we find with the attentional family, but rather to gain direct, experiential insight into the nature and dynamics of experience.

Though deconstructive meditations are used to inquire into many facets of conscious experience, the nature of the self is a topic of inquiry in a broad range of contemplative and philosophical practices. To give two important examples, examining the self is linked to the highest good in ancient Greek philosophy [START_REF] Hadot | Philosophy as a way of life: Spiritual exercises from Socrates to Foucault[END_REF] and as the key to undoing the cycle of suffering in Buddhism [START_REF] Harvey | The Selfless Mind: Personality, Consciousness, and Nirvana in Early Buddhism[END_REF]. In Buddhist meditation, the primary target of many selfinquiry practices is cognitive reification, the implicit belief that thoughts, emotions, and perceptions are accurate depictions of reality [124]. Deconstructive practices in this tradition are especially concerned with the view that the self is enduring and unitary, since a reified sense of self is believed to be the primary cause of suffering and states of discontent [START_REF] Harvey | The Selfless Mind: Personality, Consciousness, and Nirvana in Early Buddhism[END_REF]. Buddhist deconstructive practices, therefore, often involve exploring the experience of subjectivity by inquiring into the various components that comprise the self, for example [125], or by examining the relationship between the self as agent or observer and the objects it interacts with [126].

  Compassion training is held to alter core self-related processes, initiating a shift from self-oriented cognitive, affective, and behavioral patterns to patterns that are oriented toward the well-being of others[108]. In the field of psychology, empathy is characterized as the ability to understand or resonate with another's emotional state[109- 112] and compassion as a concern for the suffering of another accompanied by the motivation to help[109,113]. In the absence of compassion, empathic distress can lead to negative affect[START_REF] Lamm | The neural substrate of human empathy: effects of perspective-taking and cognitive appraisal[END_REF]114], while compassion is associated with well-being and positive emotions[114,115].Research into the neural correlates of empathy have found that similar regions, including the insula, the anterior and mid-cingulate cortices, and the supplementary motor area, are activated across various forms of empathy[111,116,117]. By way of contrast, compassion is linked to regions associated with reward, positive affect, and feelings of affection, such as the ventral striatum and medial orbitofrontal cortex[START_REF] Klimecki | Differential pattern of functional brain plasticity after compassion and empathy training[END_REF]114]. Studies of compassion training have also found increased activation in regions associated with executive function, including the dorsolateral prefrontal cortex [118] and the anterior cingulate cortex[START_REF] Klimecki | Differential pattern of functional brain plasticity after compassion and empathy training[END_REF]119]. Though further research is required to determine the unique roles that each of these regions plays in the development of compassion, these preliminary findings suggest that cultivating compassion strengthens multiple networks, each of which may affect distinct psychological processes and thereby contribute to wellbeing in different ways.Empathy and compassion also affect the peripheral biology of the human body. Perceiving stress in another individual has been linked to elevated cortisol levels, a relationship that is more robust in those with high trait empathy [120], whereas compassion has been linked to lower levels of cortisol reactivity[121]. Preliminary studies of compassion training have found associations between the amount of time spent engaging in compassion training and inflammatory biomarkers, with more compassion training leading to decreased levels of both C-reactive protein and interleukin (IL)-6

Trends Cogn Sci. Author manuscript; available in PMC 2016 September 01.

Acknowledgements

Support for our research described here was provided by NCCIH NIH P01AT004952, ERC Consolidator Grant (BRAINandMINDFULNESS, 617739), and several gifts to the Center for Investigating Healthy Minds at the University of Wisconsin-Madison (CIHM_UW). RJD is Founder and President of the Center for Investigating for Investigating Healthy Minds, Inc., (CIHM, Inc) a non-profit corporation associated with CIHM-UW. CJD is Chairman of Tergar International, a non-profit organization that coordinates a global network of meditation centers.

Outstanding Questions

1. How do the various forms of training found in the three families interact with one another? Is there an optimal sequence or does it depend on the individual? What are the order effects of individual practices?

2.

To what extent do the effects of specific meditations rest on the frameworks, beliefs, and worldviews that underlie these practices?

Typology of Meditation Practices and Related Clinical Interventions

This typology groups commonly practiced forms of meditation and meditation-based clinical interventions into subcategories of each of the three families. Please note that while many practices contain elements of all three families, categorizations in this framework are based on the primary mechanisms of individual practices. Given the complexity of each practice listed here, we present this system as an initial step in the long process of studying the diversity of meditation practices. See supplementary materials for descriptions of individual practices and relevant citations.

Attentional Family

Constructive Family

Deconstructive Family

Focused Attention (FA)

•