Transcript: The entropic brain: a theory of conscious states informed by neuroimaging research with psychedelic drugs

Alex: Welcome to another episode of ResearchPod.

Sam: Today we're looking at a paper that maps how our brain creates our sense of self—and what happens when that anchor is cut loose. It's called the Entropic Brain Hypothesis, and the central claim is that normal consciousness isn't the brain's default state. Instead, it's a state of active suppression—the brain constantly working to keep itself stable and orderly.

Alex: So the paper is asking whether our consistent feeling of being a "self" is actually a biological construction? Something the brain is actively building, moment to moment?

Sam: Exactly. Here's a way to picture it. Imagine the brain is like a gas inside a container. Left alone, gas expands in every direction—it explores every possible space. But your brain compresses that gas into a tight, orderly shape. That compression is what gives you a stable sense of who you are. The paper suggests that psychedelics release that pressure, allowing the gas to expand again.

Alex: So the "gas" is the range of possible brain states the mind could be in, and the "container" is whatever mechanism keeps us focused on being us?

Sam: That's it. A specific network of brain regions acts like a conductor in an orchestra, keeping every section playing in time and on cue. Your thoughts stay constrained, predictable, and organised around a coherent identity.

Alex: And what happens when you turn that conductor off?

Sam: The brain enters what the researchers call a "primary state"—a state of higher entropy. Entropy, here, is simply a measure of how many different configurations a system could be in at once. Think of a tidy bedroom versus a messy one: the tidy room is in one specific arrangement, but the messy room could be messy in thousands of different ways. In a high-entropy state, the brain is no longer locked into one predictable pattern. It's been given permission to explore a much wider range of possibilities.

Alex: So in this primary state, the brain is more disorganised—but also more flexible?

Sam: Precisely. The researchers describe it as a state of "criticality"—poised right on the edge between order and chaos. Not so rigid that it's stuck, not so disordered that it falls apart. The paper suggests this is actually closer to how an infant's brain operates, before years of experience carve deep, fixed grooves into how we think.

Alex: So the adult brain is normally held back from that edge—kept in a more ordered state—to let us function in a stable, predictable way?

Sam: That's the hypothesis. And that suppression is genuinely useful. It's what allows us to think about our own thinking—to plan, to reflect, to maintain a coherent identity across time. But like most biological trade-offs, it comes with a cost.

The entropic brain: a theory of conscious states informed by neuroimaging research with psychedelic drugs

Robin L. Carhart-Harris, Robert Leech, Peter J. Hellyer, Murray Shanahan, Amanda Feilding, Enzo Tagliazucchi, Dante R. Chialvo, David Nutt

Jan 1, 2014·5:41·doi·Original Paper

Entropic Brain HypothesisPrimary States of ConsciousnessDefault-Mode Network (DMN)CriticalityEntropy SuppressionThe Entropic Brain

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6 min

Briefing

Research Question

This paper introduces the 'entropic brain' hypothesis, a theoretical framework that integrates physics, neurobiology, and psychoanalysis to explain the nature of conscious states. The authors seek to understand how normal waking consciousness differs from 'primary' states—such as the psychedelic experience, REM sleep, and early psychosis—and how the brain maintains its organized, adult state.

The Entropic Brain Hypothesis

The authors propose that the quality of any conscious state is determined by its system entropy, which serves as a proxy for the brain's degree of disorder and the repertoire of potential mental states. They argue that normal waking consciousness is a state of 'constrained' entropy, where the brain operates just below a 'critical' point—a transition zone between order and chaos. By suppressing entropy, the adult brain maintains a stable sense of self and high-level metacognitive functions like reality-testing.

Psychedelics as a Research Tool

The paper posits that psychedelic drugs act as a 'superhighway' to the unconscious by inducing a state of elevated entropy. Neuroimaging data with psilocybin suggests that these substances cause a collapse of the default-mode network (DMN) and a decoupling of its connectivity with the medial temporal lobes. This disruption allows the brain to move toward a more critical, disordered state, which the authors identify as a 'primary' state of consciousness similar to that of infants or archaic humans. This transition provides a unique, observable window into the mechanisms of ego-dissolution and the underlying structure of the mind.

Why It Matters

By bridging the gap between cognitive neuroscience and psychoanalytic theory, this framework offers a mechanistic way to study subjective experiences that were previously considered untestable. It suggests that the evolution of human consciousness involved a transition from high-entropy, primary states to a more organized, entropy-suppressed state, providing a new perspective on mental health, self-awareness, and the fundamental architecture of human cognition.

Key Terms and Definitions

Entropy — A measure of the uncertainty or randomness within a system, used here to quantify the disorder and the repertoire of potential states in brain activity.
Criticality — A state of a complex system poised at the transition between order and chaos, characterized by maximum sensitivity to input and a wide range of metastable states.
Default-Mode Network (DMN) — A set of brain regions that are highly active during rest and self-referential thought, which the authors associate with the maintenance of the ego or sense of self.
Primary State — A mode of consciousness characterized by high entropy and a lack of the rigid, constrained organization found in normal adult waking consciousness.
Ego-Dissolution — A psychological phenomenon often reported during psychedelic experiences where the subject's sense of an immutable, integrated identity breaks down.

Abstract

Entropy is a dimensionless quantity that is used for measuring uncertainty about the state of a system but it can also imply physical qualities, where high entropy is synonymous with high disorder. Entropy is applied here in the context of states of consciousness and their associated neurodynamics, with a particular focus on the psychedelic state. The psychedelic state is considered an exemplar of a primitive or primary state of consciousness that preceded the development of modern, adult, human, normal waking consciousness. Based on neuroimaging data with psilocybin, a classic psychedelic drug, it is argued that the defining feature of "primary states" is elevated entropy in certain aspects of brain function, such as the repertoire of functional connectivity motifs that form and fragment across time. Indeed, since there is a greater repertoire of connectivity motifs in the psychedelic state than in normal waking consciousness, this implies that primary states may exhibit "criticality," i.e., the property of being poised at a "critical" point in a transition zone between order and disorder where certain phenomena such as power-law scaling appear. Moreover, if primary states are critical, then this suggests that entropy is suppressed in normal waking consciousness, meaning that the brain operates just below criticality. It is argued that this entropy suppression furnishes normal waking consciousness with a constrained quality and associated metacognitive functions, including reality-testing and self-awareness. It is also proposed that entry into primary states depends on a collapse of the normally highly organized activity within the default-mode network (DMN) and a decoupling between the DMN and the medial temporal lobes (which are normally significantly coupled). These hypotheses can be tested by examining brain activity and associated cognition in other candidate primary states such as rapid eye movement (REM) sleep and early psychosis and comparing these with non-primary states such as normal waking consciousness and the anaesthetized state.

The entropic brain: a theory of conscious states informed by neuroimaging research with psychedelic drugs | Robin L. Carhart-Harris et al. | ResearchPod

The entropic brain: a theory of conscious states informed by neuroimaging research with psychedelic drugs: Research Paper Podcast