Default Mode Network, Psychedelics, and the Double-Edged Opening of Consciousness: From Unity to the Unburied Self

Introduction

Classic psychedelics (e.g., psilocybin, LSD, DMT/ayahuasca) reliably alter self-experience and meaning-making. A central neurocognitive account places the Default Mode Network (DMN)—a self-referential hub spanning medial prefrontal and posterior cingulate/precuneus cortices—at the heart of these shifts. The DMN scaffolds autobiographical memory, narrative identity, mind-wandering, and social self-processes; perturbing it can both expand consciousness toward experiences of unity and, at times, disinhibit protective defenses, surfacing dissociative material. This article synthesizes current evidence on psychedelics and the DMN, and integrates clinical implications for both transformative insight and destabilization.

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The DMN and the sense of self

The DMN underpins self-referential and social-cognitive processing across midline structures (mPFC, PCC/precuneus), interfacing with memory and affective systems to maintain a coherent narrative “I.” Reviews converge that DMN activity/connectivity supports autobiographical memory, semantic self-knowledge, and perspective-taking (Qin & Northoff, 2011; Menon, 2023; Molnar-Szakacs & Uddin, 2013).

What psychedelics do to the DMN

Early human neuroimaging showed psilocybin acutely reduces DMN integrity—notably decoupling mPFC and PCC—with associated desynchronization of cortical rhythms (Carhart-Harris et al., 2012; Muthukumaraswamy et al., 2013). Systematic reviews confirm within-DMN connectivity decreases alongside increases in global/between-network connectivity (Gattuso et al., 2023; Madsen et al., 2021). Under LSD, global functional connectivity expands, correlating with ego-dissolution—a loosening of self-world boundaries (Tagliazucchi et al., 2016). Effective connectivity work also shows reorganization of cortico-striato-thalamo-cortical (CSTC) loops, consistent with altered gating and top-down constraint (Preller et al., 2019).

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The REBUS model (Relaxed Beliefs Under Psychedelics) explains these findings computationally: 5-HT2A agonism increases cortical entropy, relaxing high-level priors (many of which function as “defenses”), thereby liberating bottom-up information flow from limbic and interoceptive sources (Carhart-Harris & Friston, 2019).

From DMN quieting to “unity consciousness”

Subjectively, DMN attenuation often maps to mystical-type or self-transcendent experiences—feelings of unity, sacredness, and ineffability measured by the Mystical Experience Questionnaire (MEQ) (Barrett et al., 2015; Griffiths et al., 2008). Neurophenomenologically, ego-dissolution correlates with network “disintegration” and decoupling between medial temporal structures and high-level cortex (Lebedev et al., 2015), and with LSD-induced global hyper-connectivity (Tagliazucchi et al., 2016).

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Converging evidence outside psychedelics is instructive: experienced meditators also show reduced DMN activity during practice, supporting the idea that quieting self-narrative processes can foster selflessness and oneness (Brewer et al., 2011).

Therapeutic “reset”: from rigid selfing to flexible integration

Clinically, a transient DMN disintegration may be followed by post-acute reorganization. In treatment-resistant depression, psilocybin increased DMN within-network RSFC post-treatment, alongside symptom improvement—compatible with a “reset” from overly rigid patterns toward healthier integration (Carhart-Harris et al., 2017). The PiMS framework (Pivotal Mental States) proposes that psychedelics can precipitate brief, high-plasticity windows where emotional breakthrough and cognitive flexibility support enduring change—if appropriately supported (Brouwer & Carhart-Harris, 2021).

The other edge: relaxing defenses, dissociation, and “parts” material

Relaxing high-level priors (REBUS) is a double-edged process. The same reduction in top-down constraint that enables insight can also lower defensive barriers, allowing trauma-laden content to emerge abruptly (Carhart-Harris & Friston, 2019). Large survey work documents that a minority of psilocybin users undergo highly challenging experiences with significant acute distress and, rarely, persisting difficulties—risks modulated by dose, duration, and inadequate support (Carbonaro et al., 2016).

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Within trauma frameworks, structural dissociation conceptualizes the personality as divided into apparently normal parts and trauma-related parts that maintain safety via dissociative defenses (van der Hart, Nijenhuis & Steele, 2006). Psychedelic DMN perturbation—loosening narrative self-stability—may unmask or “awaken” dissociative parts, particularly when traumatic memories become highly accessible (Elfrink & Bergin, 2023).

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Mechanistic bridge: from network dynamics to parts activation

1. DMN down-weighting reduces precision of top-down predictions (priors), decreasing the brain’s bias toward the status-quo self-model. Bottom-up interoceptive/limbic signals become more salient (Carhart-Harris & Friston, 2019).
2. Connectivity reorganization (expanded global integration; CSTC retuning) facilitates novel cross-talk among systems that are usually segregated (Tagliazucchi et al., 2016; Preller et al., 2019).
3. Phenomenology: when this cross-talk is affectively charged with implicit trauma memory, the subjective result can be ego-dissolution alongside somatic/emotional reliving—experienced clinically as contact with “parts” (Lebedev et al., 2015; Gattuso et al., 2023).
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Safety, set/setting, and titration

Human hallucinogen research offers clear safety guidelines: meticulous screening (e.g., psychosis risk), skilled support, and careful dosing and preparation/integration substantially reduce adverse outcomes (Johnson, Richards & Griffiths, 2008). Still, challenging experiences are not uncommon; their therapeutic value depends on containment, meaning-making, and integration practices (Carbonaro et al., 2016).

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For trauma-exposed or dissociative clients, a psycholytic (low-to-moderate) dosing strategy with somatic titration and parts-informed work may help avoid over-exposure and autonomic flooding that can destabilize functioning. This recommendation follows from both the neuroscience of graded DMN perturbations (Muthukumaraswamy et al., 2013) and the clinical insights of PISD (Elfrink & Bergin, 2023).

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Conclusions

Psychedelics transiently loosen the DMN’s hold on self-narrative, enabling experiences of unity and perspectival flexibility—and, post-acutely, the possibility of a therapeutic reset toward healthier integration. The same mechanism can lower defenses and surface dissociative parts, which is potentially healing in the right container and destabilizing without it.

The emerging hypothesis of Psychedelic Iatrogenic Structural Dissociation (PISD) (Elfrink & Bergin, 2023) provides a crucial trauma-informed lens: DMN disintegration can both expand consciousness into unity and simultaneously expose dissociative parts in destabilizing ways. Integrating neuroscience of the DMN with trauma frameworks like PISD may guide the development of safer, more effective psychedelic-assisted therapies—balancing transformation with containment.

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References

Barrett, F.S., Johnson, M.W. & Griffiths, R.R., 2015. Validation of the revised Mystical Experience Questionnaire in experimental sessions with psilocybin. Journal of Psychopharmacology, 29(11), pp.1182–1190.

Brewer, J.A. et al., 2011. Meditation experience is associated with differences in default mode network activity and connectivity. Proceedings of the National Academy of Sciences, 108(50), pp.20254–20259.

Brouwer, A. & Carhart-Harris, R.L., 2021. Pivotal mental states. Journal of Psychopharmacology, 35(4), pp.362–375.

Carbonaro, T.M. et al., 2016. Survey study of challenging experiences after ingesting psilocybin mushrooms: Acute and enduring positive and negative consequences. Journal of Psychopharmacology, 30(12), pp.1268–1278.

Carhart-Harris, R.L. et al., 2012. Neural correlates of the psychedelic state as determined by fMRI studies with psilocybin. Proceedings of the National Academy of Sciences, 109(6), pp.2138–2143.

Carhart-Harris, R.L. et al., 2017. Psilocybin for treatment-resistant depression: fMRI-measured brain mechanisms. Scientific Reports, 7, 13187.

Carhart-Harris, R.L. & Friston, K.J., 2019. REBUS and the anarchic brain: Toward a unified model of the brain action of psychedelics. Pharmacological Reviews, 71(3), pp.316–344.

Elfrink, S. & Bergin, L., 2023. Psychedelic Iatrogenic Structural Dissociation (PISD): An Exploratory Hypothesis on Amplified Dissociative Processes. Frontiers in Psychology.

Gattuso, J.J., Azzopardi, C., Comninos, A.N. & Warwick, J., 2023. Default Mode Network modulation by psychedelics: A systematic review. International Journal of Neuropsychopharmacology, 26(3), pp.155–176.

Griffiths, R.R. et al., 2008. Mystical-type experiences occasioned by psilocybin mediate the attribution of personal meaning and spiritual significance 14 months later. Journal of Psychopharmacology, 22(6), pp.621–632.

Johnson, M.W., Richards, W.A. & Griffiths, R.R., 2008. Human hallucinogen research: Guidelines for safety. Journal of Psychopharmacology, 22(6), pp.603–620.

Lebedev, A.V. et al., 2015. Neural correlates of ego-dissolution under psilocybin. Human Brain Mapping, 36(8), pp.3137–3153.

Madsen, M.K. et al., 2021. Psilocybin-induced changes in brain network integrity and segregation. European Neuropsychopharmacology, 50, pp.52–63.

Menon, V., 2023. Twenty years of the default mode network: a review and synthesis. Annual Review of Neuroscience, 46, pp.77–104.

Molnar-Szakacs, I. & Uddin, L.Q., 2013. Self-processing and the default mode network: Interactions with the mirror neuron system. Frontiers in Human Neuroscience, 7, 571.

Muthukumaraswamy, S.D. et al., 2013. Broadband cortical desynchronization underlies the human psychedelic state. Journal of Neuroscience, 33(38), pp.15171–15183.

Preller, K.H. et al., 2019. Effective connectivity changes in LSD-induced altered states of consciousness in humans. Proceedings of the National Academy of Sciences, 116(7), pp.2743–2748.

Qin, P. & Northoff, G., 2011. How is our self related to midline regions and the default-mode network? NeuroImage, 57(3), pp.1221–1233.

Tagliazucchi, E. et al., 2016. Increased global functional connectivity correlates with LSD-induced ego dissolution. Current Biology, 26(8), pp.1043–1050.

van der Hart, O., Nijenhuis, E.R.S. & Steele, K., 2006. The Haunted Self: Structural Dissociation and the Treatment of Chronic Traumatization. New York: W.W. Norton.

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