This narrative review discusses how meditation and psychedelic drugs can alter states of consciousness. There is converging evidence that psychedelics and meditation can produce strong, short-term, and reversible disruptions of self-consciousness and underlying neural processes. However, experiences of “self-loss” are not uniform and can be decomposed in “narrative” aspects (e.g. loss of access to autobiographical information), as well as bodily and multisensory aspects (e.g. loss of body ownership). Finally, the authors consider long-term outcomes of experiences of self-loss on individual traits and prosocial behavior.

Abstract

“In recent years, the scientific study of meditation and psychedelic drugs has seen remarkable developments. The increased focus on meditation in cognitive neuroscience has led to a cross-cultural classification of standard meditation styles validated by functional and structural neuroanatomical data. Meanwhile, the renaissance of psychedelic research has shed light on the neurophysiology of altered states of consciousness induced by classical psychedelics, such as psilocybin and LSD, whose effects are mainly mediated by agonism of serotonin receptors. Few attempts have been made at bridging these two domains of inquiry, despite intriguing evidence of overlap between the phenomenology and neurophysiology of meditation practice and psychedelic states. In particular, many contemplative traditions explicitly aim at dissolving the sense of self by eliciting altered states of consciousness through meditation, while classical psychedelics are known to produce significant disruptions of self-consciousness, a phenomenon known as drug-induced ego dissolution. In this article, we discuss available evidence regarding convergences and differences between phenomenological and neurophysiological data on meditation practice and psychedelic drug-induced states, with a particular emphasis on alterations of self-experience. While both meditation and psychedelics may disrupt self-consciousness and underlying neural processes, we emphasize that neither meditation nor psychedelic states can be conceived as simple, uniform categories. Moreover, we suggest that there are important phenomenological differences even between conscious states described as experiences of self-loss. As a result, we propose that self-consciousness may be best construed as a multidimensional construct, and that “self-loss,” far from being an unequivocal phenomenon, can take several forms. Indeed, various aspects of self-consciousness, including narrative aspects linked to autobiographical memory, self-related thoughts and mental time travel, and embodied aspects rooted in multisensory processes, may be differently affected by psychedelics and meditation practices. Finally, we consider long-term outcomes of experiences of self-loss induced by meditation and psychedelics on individual traits and prosocial behavior. We call for caution regarding the problematic conflation of temporary states of self-loss with “selflessness” as a behavioral or social trait, although there is preliminary evidence that correlations between short-term experiences of self-loss and long-term trait alterations may exist.”

Authors: Raphaël Millière, Robin L. Carhart-Harris, Leor Roseman, Fynn-Mathis Trautwein & Aviva Berkovich-Ohana

Summary

INTRODUCTION

In recent years, the scientific study of meditation and psychedelic drugs has seen remarkable developments. However, few attempts have been made to bridge the two domains of inquiry, despite increasing evidence of overlap between the phenomenology and neurophysiology of meditation practices and psychedelic states.

Both meditation and psychedelics can induce a wide variety of global states of consciousness, but these states are sensitive to a multitude of factors.

We suggest that self-consciousness is a multidimensional construct, and that self-loss or ego dissolution may be a non-linear phenomenon that only occurs after a critical inflection point has been reached.

We consider the long-term outcomes of temporary states of self-loss induced by meditation and psychedelics on individual traits and prosocial behavior.

THE NEUROSCIENCE OF MEDITATION AND PSYCHEDELICS: AN OVERVIEW

Meditation refers to a set of cognitive training techniques that aim to monitor and regulate attention, perception, emotion and homeostasis. It has been developed in many different cultures and spiritual traditions.

Researchers have sought to categorize the main styles of meditation across cultural, geographical and historical contexts, based on the core goals and principles of the mental techniques involved. These effects include enhanced attention and sensory processing, largely positive emotions and mood, and increased cognitive flexibility and creativity.

Psychedelics are psychoactive substances that affect serotonin 2A (5-HT2A) receptors and cause visual and auditory distortions, profound changes in emotions and mood, heightened sensitivity to internal and external context, and at higher doses, dramatic alterations of self-consciousness known as drug-induced ego dissolution (DIED).

Neural Correlates of Meditative Practices

Over the past 20 years, neuroimaging studies have investigated various styles of meditation using electroencephalography, functional magnetic resonance imaging and positron emission tomography. These studies have revealed that meditation practices from distinct traditions share some common neural correlates.

FA was correlated with significant activation clusters in executive brain areas and with the deactivation of two important hubs of the default-mode network, suggesting that mantra recitation is linked to decreased awareness of bodily sensation.

Insular cortex activity was correlated with awareness of interoceptive signals in OM, and with the voluntary control of thought and action in LK. The right thalamus was deactivated in LK, and no significant deactivation cluster was found in OM.

Different styles of meditation activate the insula in different ways, but all involve the insula in some way. This suggests that the insula is involved in the regulation of attention.

In many studies of mindfulness meditation, the default mode network (DMN) is attenuated, particularly in the medial prefrontal cortex and the posterior cingulate cortex, compared to meditation-naive controls or within-group resting state. Moreover, within-DMN connectivity is reduced during LK.

Neural Correlates of Psychedelic States

Recent studies using fMRI and PET/SPECT have found that psychedelic drugs have significant effects on many brain areas, including the frontal and temporal cortical areas, as well as hubs of the default mode network (DMN).

Recent fMRI studies revealed that psilocybin, ayahuasca and LSD alter resting-state functional connectivity in key nodes of the default mode network (DMN), and that psilocybin and LSD produce an enhanced repertoire of dynamical brain states.

Psychedelic drugs are known to produce short-term, dramatic effects on self-consciousness, and have been linked to increased functional connectivity between the default mode network (DMN) and a task-positive network, decreased integrity of the DMN and salience network, increased entropy and spontaneous MEG signal diversity, and decreased mean energy and fluctuations of low frequency connectome harmonics.

ALTERATIONS OF SELF-CONSCIOUSNESS INDUCED BY MEDITATION AND PSYCHEDELICS

While it is often claimed that meditation and psychedelic drugs can induce “selfless” states of consciousness, this claim requires qualification. It is important to investigate which aspects of self-consciousness can be disrupted by meditation and psychedelic drugs, and whether both modes of induction may alter self-consciousness in similar ways.

Disruption of Narrative Aspects of Self-Consciousness

The familiar experience of thinking about oneself is perhaps the most salient form of self-consciousness. De se thoughts include thoughts about one’s personality traits or one’s life trajectory, as well as more mundane thoughts like wondering what one will have for dinner. Self-referential cognitive content includes de se thoughts, autobiographical memory retrieval and self-centered mental time travel to the future. Together, these self-centered mental episodes constitute narrative self-consciousness.

The rate of occurrence of self-referential thought and mental time travel may be dramatically reduced, or altogether suppressed, during a certain time interval. This is achieved by increasing meta-awareness of mind-wandering, and re-focusing attention back onto a particular object or a wider awareness of the present moment.

The DMN is deactivated during mindfulness meditation, which is consistent with the practice’s focus on attentional control of mind-wandering episodes. This deactivation is more significant during meditation than during other cognitive tasks, which may be characteristic of the suppression of mind-wandering that can be achieved by trained meditators.

A study using dynamic causal modeling suggested that self-referential processes are driven by PCC activity and modulated by the regulatory influences of the mPFC. Moreover, DMN disintegration was correlated with reports of ego dissolution and decreased mental time travel to the past.

Narrative self-consciousness may be altered by the temporary cessation of self-referential thoughts, or by a total loss of access to autobiographical memories and self-related beliefs. However, the experience of losing access to these memories and beliefs may differ from the mere cessation of de se thought.

The DMN is associated with age-related memory deficits and Alzheimer’s disease. This may explain the link between DMN disintegration and ego dissolution.

Psychedelic state may be mediated by pronounced reductions in DMN integrity. The retrosplenial cortex may act as a gateway between the hippocampal formation and specific DMN regions for memory retrieval, which may be related to a loss of access to autobiographical memories.

Psychedelic drugs can alter narrative aspects of self-consciousness through temporary cessation of self-referential thought and mental time travel, or more dramatically through a temporary loss of access to semantic autobiographical information.

During meditation and psychedelic states, the retrieval of self-related information may be reduced, and the dispositional ability to retrieve such information may be temporarily impaired. These alterations of narrative aspects of self-consciousness come in degrees, and it is not yet clear whether these different degrees lie on a linear scale.

Disruption of Multisensory Aspects of Self-Consciousness

Self-related thoughts are a paradigmatic example of self-consciousness, but there are many different forms of self-consciousness, including the “narrative self” and the “minimal self”. The minimal self is crucially linked to embodiment and agency. The distinction between high-level/narrative and minimal/embodied selfhood is helpful in clarifying the umbrella notion of self-consciousness, but remains somewhat ambiguous and potentially simplistic as such.

At least three constructs may be distinguished as being related to a basic form of self-consciousness rooted in multisensory processing: body ownership, bodily awareness, and spatial self-location.

The Sense of Body Ownership

Body ownership is a controversial notion, as it is not clear whether there is a phenomenology of ownership in daily experience, or how to characterize such a phenomenology. In the rubber hand illusion, healthy participants report experiencing an illusory ownership over a fake hand, as well as a loss of ownership over their real hand. Moreover, a number of physiological measurements appear to indicate that the real limb is temporarily ‘disowned’ by the body during the illusion.

Many authors interpret these data as evidence that ordinary conscious experience involves a sense of body ownership that can be altered by meditation and psychedelics. Recent studies suggest that mindfulness meditation can indeed induce a loss of body ownership. One highly experienced meditator described the dissolution of the sense of body ownership in a series of open-ended interviews following the methodological principles of the microphenomenological interview technique. Dor-Ziderman and colleagues tested 12 long-term mindfulness meditators using magnetoencephalogram (MEG) recording and first-person reports.

Subjective reports were analyzed and grouped in categories validated by 12 naive referees. Four reports were grouped in the category of experiences lacking a sense of ownership.

There are many reports of people feeling disconnected from their bodies when they take psychedelics, including descriptions of a loss of ownership over one’s body. The hypothesis that top-down constraints on body representation are loosened in the psychedelic state is supported by evidence of reduced binocular rivalry switching rate and occasional phenomenal fusion of rival images under psilocybin and ayahuasca, as well as reduced susceptibility to the hollow mask illusion.

Evidence from open-ended interviews and self-report questionnaires suggests that the sense of body ownership can go missing during certain conscious states induced by meditation and psychedelics.

Bodily Awareness

Bodily awareness can be defined as the conscious awareness of bodily sensations, including tactile, proprioceptive and interoceptive stimuli. Some philosophers have argued that bodily awareness constitutes a form of self-consciousness. In recent years, a similar idea has emerged within neuroscience that one’s body is experienced as one’s own, anchoring oneself in one’s body. This idea does not necessarily rest on the hypothesis that there is a specific phenomenology of body ownership.

Meditation practices focus on bodily sensations, and the insula is an important hub for processing interoceptive signals. Therefore, one would not expect to lose bodily awareness during meditation practice. In certain forms of mindfulness meditation, bodily awareness can be reduced to a subtle background presence. However, a minimal level of dynamic proprioception remains, even when the sense of boundaries disappears.

It is debatable whether proprioceptive awareness was retained in this state, but it is plausible that some degree of interoceptive awareness was preserved, and that experienced mindfulness meditators could significantly inhibit awareness of bodily sensations during their practice.

Although it remains unclear whether bodily awareness can completely disappear during meditation, there is evidence that subjects can lack any awareness of their body and of specific bodily sensations in altered states induced by psychedelic substances.

In a recent neuroimaging study of DMT, almost all participants reported losing awareness of their body for several minutes during the peak of the experience. Anecdotal evidence suggests that 5-MeO-DMT may be particularly effective at suppressing bodily awareness.

Certain meditation practices may inhibit awareness of bodily sensations, while psychedelic substances may completely suppress awareness of the body. Sensory deprivation may play an important role in this reduction of bodily awareness.

Psychedelic drugs and some styles of meditation can increase awareness of the body, but there is also evidence that body awareness can fade away in so-called “bodiless” dreams and “asomatic” out-of-body experiences.

Spatial Self-Location

A third notion associated with a minimal form of self-consciousness rooted in multisensory integration is spatial self-location. This idea combines two claims: first, that perceptual experience is self-locating, and second, that the location of the point of origin is represented as the location of the subject.

It is generally agreed that ordinary perceptual experience has self-locating content, but full-body illusions can manipulate self-location, such that subjects may feel located outside of their own body or closer to the virtual avatar over which they feel ownership during the illusion.

Researchers claim that spatial self-location is an important aspect of bodily self-consciousness, and that a loss of sense of orientation in space is a minimally sufficient condition for self-consciousness. However, meditation and psychedelics may radically disrupt the experience of spatial self-location. In another study, long-term mindfulness meditation practitioners were able to induce a state of “spacelessness,” described as a sense of spaciousness, boundlessness, and no quality of border.

Psychedelic drugs induce a loss of spatial self-location, a feeling of unity with everything, and a loss of boundary between self and world. Subjects score high on the factor related to “experience of unity” after administration of LSD and psilocybin, and a recent online survey found that the overwhelming majority of respondents scored positively on items corresponding to “Loss of your usual sense of space”.

There is a large amount of anecdotal evidence from online narrative reports that DMT and 5-MeO-DMT can induce a loss of self-location. These reports include: “I didn’t know where it was, or where I was” (DMT), “I was the universe, I was everywhere and nowhere, everything and nothing all at the same time” (DMT), “I had no body” (DMT). Narrative reports from online databases and questionnaire data from multiple controlled studies suggest that psychedelic drugs can induce experiences without spatial content.

Some reports of meditative and psychedelic experiences lacking spatial self-locating content are reminiscent of reports of conscious episodes during dreamless sleep, which allegedly lack any form of self-consciousness and spatial content. However, some reports of drug-induced ego dissolution insist on the timeless character of the experience.

The temporoparietal junction is involved in processing spatial self-location, and the intensity of drug-induced ego dissolution correlated with the magnitude of increased functional connectivity in the bilateral insular cortex and the temporoparietal junction. Studies have suggested that beta oscillations encode top-down modulations of predictions, and that decreased beta power in the temporoparietal junction may relate to weakened top-down constraint on multisensory processing underlying self-location.

This section has left out the notion of the sense of agency, which is typically defined as the experience of being in control of one’s actions. There is little available evidence regarding how the sense of agency, in either construal, may be modulated by meditation and drug-induced states.

PURE CONSCIOUSNESS, NON-DUAL AWARENESS AND TOTAL SELFLESSNESS

In this section we consider how meditation practices that aim at a dissolution of self-consciousness compare to drug-induced states, and whether they involve a dramatic inhibition of the dimensions of self-consciousness.

Non-dual Awareness

Non-dual awareness meditation (NDA) is a family of practices which can be found in several Eastern contemplative traditions. It rests on three core assumptions: (a) ordinary experience is “dual” (i.e. structured around a subject-pole and an object-pole), (b) this subject-object dichotomy is illusory, and (c) conscious awareness is non-dual.

There are at least two ways to understand this claim: either there is a form of sui generis self-awareness in experience which is irreducible to the cognitive, bodily and spatial features of experience, or there is a background awareness of oneself which is reducible to these components.

The seemingly dichotomous nature of experience rests on the very nature of conscious representation in general, which is structured by an implicit distinction between the represented objects and the subject to whom those objects are presented.

Non-dual awareness meditation practices assume that the subject-object dichotomy in ordinary experience is illusory, and reveal that the putative phenomenological distinction between oneself and one’s experience of the external world is ultimately an illusion.

While Fasching’s argument is consistent with the reductionist interpretation of the subject/object dichotomy, he goes on to argue that in perception I am necessarily co-conscious of myself, because the subject/object polarity is built in all conscious representational states. Fasching and Albahari suggest that non-dual awareness meditation involves a direct realization that consciousness is ownerless.

The second interpretation of ordinary consciousness is that subjects have a sense that all of their experiences are theirs, given to them, or owned by them. Trained meditators can dispel this illusion by becoming aware of consciousness itself as a non-dual process.

Non-duality may be interpreted as a blurring or dissolution of the boundary between self and world, and a loss of narrative and multisensory aspects of self-consciousness. However, it is possible that global states of consciousness reached through NDA meditation may preserve some awareness of bodily sensations.

In summary, we have suggested that NDA states can be understood in two different ways: either as conscious states in which narrative and perhaps multisensory aspects of self-consciousness are radically disrupted, or as ordinary conscious states involving a minimal form of self-awareness.

Although there have been few neuroimaging studies of NDA meditation, the available evidence suggests that the default-mode network is positively correlated with regions commonly recruited in attention-demanding tasks during NDA meditation compared to the resting state and focused attention meditation. The decrease of the anticorrelation between the default mode network and a task-positive network was observed after administration of psilocybin, and was hypothesized to correlate with decreased separatedness between internally and externally focused states.

Pure Consciousness

Stace (1960) applied the notion of pure consciousness to mystical experiences, and it has been qualified as a state reached through certain forms of meditation.

There is considerable debate about whether purely conscious states are even possible. Some argue that they are impossible, while others argue that we can find evidence of pure consciousness in contemplative practices or dreamless sleep.

Although controversial, the hypothesis that some conscious mental states lack representational content has been defended on the ground that states such as moods, pain or orgasm do not seem to represent anything. However, the notion of a purely conscious mental state literally lacking phenomenal character is absurd.

Pure consciousness is a conscious state lacking ordinary phenomenal content, such as self-referential thoughts, bodily ownership, body awareness and self-location. It is unclear whether purely conscious states can actually occur, specifically during meditation or after psychedelic intake.

In the Hindu and Buddhist traditions, Samadhi practice aims at inducing a state of deep absorption, culminating in a “formless” or “objectless” state, where all intentional objects have been stripped away and only “onepointed” awareness remains.

The aim of Samadhi meditation is to reach a state of pure consciousness, which involves a complete loss of self-consciousness. Miri Albahari has suggested that this state could provide evidence for the existence of witness-consciousness, which she defines as the neutral common denominator between all conscious experience.

The neurophysiological evidence regarding Samadhi practice is still extremely sparse, but a single-participant study found decreased activity in Brodmann areas 5 and 7, which may be associated with the representation of the body’s orientation in three-dimensional space.

The notions of non-dual awareness and pure consciousness are not clearly distinguished in the relevant literature, and there is not yet enough data on the phenomenology and neurobiology of alleged states of “pure consciousness” and “non-dual awareness” to determine whether these are valid and distinct constructs.

Non-dual awareness may be defined as a temporary loss of experiential boundary between self and world, or between endogenous and exogenous stimuli. Pure consciousness may also be defined as a state of extreme absorption involving high sensory gating, whose sparse phenomenal content has little overlap with the rich phenomenology of ordinary wakeful experience. Some forms of self-loss induced by psychedelics may involve a rich sensory phenomenology, while others are more similar to descriptions of “pure consciousness”, and may be almost devoid of sensory content.

TOWARD A MULTIDIMENSIONAL MODEL OF ALTERED SELF-CONSCIOUSNESS

In what precedes, we have suggested that some meditation practices and some psychedelic substances can disrupt self-consciousness in different ways, and that these disruptions can be categorized into two main categories: narrative and embodied selfhood. These two categories can be modulated by meditation and drugs in different ways, and to different degrees.

A more complex model of self-consciousness would involve more dimensions, and take into account the overall richness or sparsity of phenomenology to identify phenomenally distinct forms of self-loss, such as bodiless dreams, asomatic out-of-body experience and some psychedelic states (e.g., 5-MeO-DMT-induced states).

Meditation-induced states involve intense attentional control at least during certain stages of the practice, unlike drug-induced states, and may sometimes be associated with a specific phenomenology of retrograde amnesia.

Although we have focused on disruptions of self-consciousness in this paper, it is important to underline that both meditation and psychedelics may increase awareness of bodily sensations in other cases. This apparent paradox is resolved when considering the many parameters that may modulate the phenomenology of meditation practice and psychedelic states. We have represented four examples of global states of consciousness induced by meditation and psychedelics, and have tentatively summarized how such states might differ between meditation and psychedelics.

Future research could develop a more fine-grained way to assess the features of conscious states described as involving a loss of one’s sense of self, such as the Ego Dissolution Inventory, which would discriminate between several kinds of disruption of self-consciousness.

Although the reports discussed in this paper show a remarkable convergence, they should be treated with caution because they could be systematically unreliable and confabulatory. However, the evidence discussed in this paper is still tentative because most studies rely on a limited sample size.

The experience of losing ownership over one’s body or awareness of one’s spatial location does not necessarily imply that one’s overall phenomenology was also affected by meditating or drug administration. There is evidence that people usually experience bodily sensations and are aware of their relative location.

To address the limitations of self-reports, future research could use implicit and behavioral measurements to circumvent the risk of introspective biases. For example, researchers could investigate the representation of trunk-centered peripersonal space during meditation and after psychedelic intake.

Selflessness as a Trait

Meditation’s state effects linger into daily life, becoming long-term, trait alterations. These trait alterations include alterations in self-consciousness, either from the neurophysiological or first-person perspective.

Several studies have shown that meditation practitioners exhibit reduced resting state DMN activity and connectivity, either using electrophysiology or fMRI. Specifically, 8-week mindfulness-training increased functional connectivity of the anterior DMN region with the auditory/salience network, and long-term mindfulness practitioners demonstrated increased functional connectivity between DMN and visual regions. While fMRI studies show that mindfulness meditation practice is associated with reduced DMN activity, the related structural effects in the DMN are less clear. Initial evidence suggests that such changes in DMN functioning are indeed related to a reduced tendency to engage in self-referential processing.

There is less known about whether meditation practice affects multisensory aspects of self-consciousness in a trait-like manner, and whether the experience of drug-induced ego dissolution may have long-term effects on narrative and multisensory aspects of self-consciousness.

Relation to Therapeutic Outcomes, Well-Being and Prosociality

There is preliminary evidence that psychedelic-induced alterations of self-consciousness may mediate therapeutic outcomes. This model originated in the 50’s and 60’s and involves receiving a high dose of a psychedelic drug in a supportive environment. Many controlled studies have shown that mystical-type experiences predict positive psychological outcomes for depression, addiction, palliative care, and general well-being. Furthermore, mystical-type experiences are linked to the positive emotional outcomes of meditation.

Two variables appear to predict the occurrence of mystical-type experience in both meditation and psychedelics: trait absorption and surrender state. Subjects with higher absorption and surrender state tend to have stronger mystical-type experience.

The therapeutic effects of psychedelics for treatment-resistant depression are mediated by meaningful “breakthrough” experiences, which may include ego dissolution. The therapeutic effects of contemplative practices on well-being are not necessarily mediated by intense experiences, but rather by training of different cognitive mechanisms.

“Decentering” has been found to mediate treatment effects of mindfulness based interventions, and peak meditative experiences involving a loss of the sense of self can have lasting effects on well-being. However, the long-term effects of meditation and psychedelic experiences are still not well-studied.

Future research should investigate the specific kind of “self-loss” that mediates long-term therapeutic outcome and increased well-being. For example, increased control of spontaneous thoughts may mediate increased well-being in experienced meditators.

Meditation can enhance empathy and compassion, which are regarded as antecedents of prosocial behavior. The shift from self-centered to selfless functioning, characterized by a weak distinction between self and others, and self and the environment as a whole, may be related to meditation.

Long-term meditation practice was correlated with increased trait levels of self-reported compassion, and psychedelic use was found to potentiate in certain cases the putative long-term effects of meditation on prosocial behavior.

GENERAL CONCLUSION

Psychedelic drugs and certain forms of meditation practice can produce strong disruptions of self-consciousness. These disruptions can be decomposed into narrative, bodily and multisensory aspects, and therefore “self-loss” should not be conceived as a simple graded phenomenon ordered along a single dimension.

Even forms of putative “total” self-loss involving the radical disruption of both narrative and multisensory aspects of self-consciousness can differ from a phenomenological perspective with respect to variables that are not directly related to self-consciousness.

The empirical data remains too sparse to reliably determine the phenomenological and neurophysiological specificity of the global states of consciousness under consideration, and the interpretation of self-reports is notoriously difficult.

Future research could focus on developing finer-grained psychometric tools, correlating reports from questionnaires with neuroimaging data, and investigating the possible relationship between temporary disruptions of self-consciousness induced by meditation and psychedelics, and long-term changes in cognitive processing, personality traits and prosocial behavior.

AUTHOR CONTRIBUTIONS

All authors have made a direct contribution to the work, and have contributed to subsequent revisions of the manuscript.