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Psychedelics & Consciousness

REBUS and the Anarchic Brain

Carhart-Harris, Friston · 2019 · Pharmacological Reviews

Theoretical synthesis proposing that psychedelics work by relaxing high-level priors in a hierarchical predictive brain.

Research objective

Unify pharmacology, network neuroscience, and predictive-processing theory into a single account of psychedelic action.

Methodology

Theoretical paper integrating fMRI connectivity findings, 5-HT2A pharmacology, and active-inference frameworks.

Key findings

  • Psychedelics flatten the precision of high-level beliefs, allowing bottom-up information to update otherwise rigid models.
  • This 'anarchic' state plausibly underlies both therapeutic flexibility and risk of distress.
  • Frames set, setting, and integration as Bayesian belief updating.

Strengths

  • Bridged previously disconnected fields.
  • Generated testable predictions about pharmacology, imaging, and therapy.

Limitations

  • Theoretical scope outpaces direct empirical validation in places.
  • Difficult to falsify some core formulations.

Practical implications

  • Provides the leading theoretical framework guiding mechanistic studies of psychedelic therapy.
  • Informs why integration psychotherapy and post-dose context matter so much.
Read the original paper

Related entities

Glossary · predictive-codingGlossary · default-mode-networkGlossary · 5-ht2a-receptor

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