Restructuring consciousness -the psychedelic state in light of integrated information theory

This theory-building article examines the psychedelic state (and the entropic brain theory) from the perspective of Integrated Information Theory (IIT) and attributes the diversity of psychedelic-induced brain correlates to a loss of cause-effect information represented within the brain dynamics, which leads to a more flexible, but less predictable form of perception and cognition.

Abstract

“The psychological state elicited by the classic psychedelics drugs, such as LSD and psilocybin, is one of the most fascinating and yet least understood states of consciousness. However, with the advent of modern functional neuroimaging techniques, the effect of these drugs on neural activity is now being revealed, although many of the varied phenomenological features of the psychedelic state remain challenging to explain. Integrated information theory (IIT) is one of the foremost contemporary theories of consciousness, providing a mathematical formalization of both the quantity and quality of conscious experience. This theory can be applied to all known states of consciousness, including the psychedelic state. Using the results of functional neuroimaging data on the psychedelic state, the effects of psychedelic drugs on both the level and structure of consciousness can be explained in terms of the conceptual framework of IIT. This new IIT-based model of the psychedelic state provides an explanation for many of its phenomenological features, including unconstrained cognition, alterations in the structure and meaning of concepts and a sense of expanded awareness. This model also suggests that whilst cognitive flexibility, creativity, and imagination are enhanced during the psychedelic state, this occurs at the expense of cause-effect information, as well as degrading the brain’s ability to organize, categorize, and differentiate the constituents of conscious experience. Furthermore, the model generates specific predictions that can be tested using a combination of functional imaging techniques, as has been applied to the study of levels of consciousness during anesthesia and following brain injury.”

Author: Andrew R. Gallimore

Summary

Introduction

Modern functional neuroimaging techniques have revealed the neural correlates of the psychedelic state in humans, which has prompted the development of new models of the effects of these drugs on neural function.

Integrated information theory (IIT) is a contemporary theory of consciousness that attempts to explain the conditions under which systems, such as the brain, are conscious and for the phenomenological structure of conscious experience. It is likely that IIT has something to tell us about the psychedelic state. Recent models of the psychedelic state, based on functional imaging data, are compatible with IIT and can be used to generate testable predictions.

Phenomenology of the Psychedelic State

The psychedelic state can be characterized by an unconstrained form of cognition, with novel neural states being explored, and can be explained by the fluidity and dynamic nature of the stream of conscious experience.

Functional Neuroimaging of the Psychedelic State

The classic psychedelic drugs are partial agonists at the serotonin 5HT2A receptor, and this site has been established as the major locus for their effects. However, recent magnetoencephalography studies have shown that activation of deep layer V pyramidal neurons results in decreased neural activity.

Psilocybin causes a decrease in the anti-correlation between the default mode network (DMN) and several task positive networks (TPNs), as well as an increase in the functional connectivity between these networks post-psilocybin. This indicates a loss of network integrity and a “disorganized” brain state.

According to this model, the brain operates at a slightly subcritical state between a highly ordered, low entropy (sub-critical) state and a highly disordered, high entropy (super-critical) state. Psychedelic drugs increase the entropy of the brain and generate a more disordered and fluid state of consciousness.

A related approach was used to examine the entropy of the dynamic temporal sequence of states explored by the brain post-psilocybin, and it was found that specific connectivity motifs were exclusive to the psilocybin state.

Overview of Integrated Information Theory (IIT)

The key ideas of IIT are presented, with particular emphasis placed on those aspects of the theory most informative to the psychedelic state.

IIT proposes that for a system to be conscious, it must be both highly differentiated (informative) and integrated, and its information must be beyond that generated by its individual components.

Information is quantified by 8 (big phi), and a maximally irreducible conceptual structure is defined as a system of concepts. Concepts are the constituents of thoughts, although a more helpful definition might be “constituents of conscious experience”.

IIT describes the structure of consciousness as a system of concepts, with each cortical column representing an element of the system. Elements can combine to form mechanisms, which can be combined to form higher order mechanisms.

Every mechanism in the brain occupies a particular state at any point in time. This state constrains the past and future states of the system, and the cause-effect repertoire is the set of system states that could have caused the mechanism to enter its current state.

Upon entering a current state, a mechanism effectively rules out certain past and future system states and generates information about the past state of the system. The cause information is calculated by calculating the Earth Mover’s distance between the cause repertoire and the unconstrained past repertoire.

A concept is the integrated information specified by a mechanism. If a mechanism fails to generate any integrated information, then a concept does not exist from the subjective perspective of the complex.

A conceptual structure is a constellation of points in concept space that represent the cause-effect repertoire of a system. Each concept specifies a quantifiable amount of cause-effect information, and a conceptual structure generates conceptual information by calculating the difference between the cause-effect repertoire of each concept and the null concept.

A conceptual structure can be formed from a subset of concepts within the power set of concepts specified by the system, but only one conceptual structure can exist at any time.

The subjective conscious experience of a complex is identified with the complex itself, and its constellation of concepts determines the structure or quality of the experience.

The Psychedelic State and IIT

IIT describes conscious experiences as a shape in qualia space. This includes the psychedelic state, and can be used to explain many phenomenological features of the psychedelic state.

The Effect of Psychedelic Drugs on Information

Psychedelic drugs increase the entropy of the brain, producing a state of unconstrained cognition. This state can be explained by an increase in the repertoire of states explored by the brain.

IIT defines information as the cause-effect relationship between a state and a response. Increasing the size of a system’s state repertoire does not necessarily imply an increase in information, because a system’s current state cannot constrain random past or future states.

IIT can be used to model the psychedelic state, and it makes most sense to begin at the level of the mechanism and move up to the level of the conceptual structure.

When a mechanism enters a specific state, it constrains the cause and effect repertoires of the system, and generates cause-effect information that measures how much the mechanism constrains the past and future states of the system.

IIT suggests that the brain’s past and future states are less constrained by the states of its mechanisms, and this is equivalent to stating that the entropy of the cause and effect repertoires is increased. This can be modeled mathematically by taking a linear combination of the cause and unconstrained past repertoires.

If a system has only three possible states, then the psychedelic repertoire lies somewhere on a line connecting the unconstrained repertoire (U) and the cause or effect repertoire (R).

A linear combination of U and R will always generate a distribution with higher entropy than R, because the probabilities of the individual states must be changed, so that high probability states become lower probability and vice versa. A phenomenological perspective suggests that the concept of psychedelics changes in the psychedelic state, becoming “about more things” or acquiring additional characteristics not present in normal consciousness.

Psychedelic drugs affect the cause-effect information specified by each mechanism. The Earth Mover’s Distance (EMD) between the cause and effect repertoires can be defined as follows.

The results suggest that the psychedelic state lies somewhere in between the normal waking state and unconsciousness, with the psychedelic state varying distances from normal consciousness depending on the drug and dose. Ketamine may have a more profound disruptive effect on neural integration than the classic psychedelics.

Psychedelic drugs may reduce cause-effect information, but may also increase the degree to which this information is integrated across the cortex. As a result, concepts that don’t exist during normal waking consciousness may become present during the psychedelic state.

A psychedelic drug increases the entropy of the cause-effect repertoire and reduces the cause-effect information specified by each mechanism as it enters its current state. This results in the brain exploring an expanded repertoire of states in a more random fashion.

Changing the cause-effect repertoire and -values of concepts within the conceptual structure, and perhaps also incorporating additional concepts, changes the shape of the structure in qualia space. A psychedelic state is more dimensional than normal waking consciousness, and this higher dimensionality is due to the increased cause-effect repertoires of the concepts within the conceptual structure. However, this does not necessarily imply an increase in the overall quantity of consciousness.

This model suggests that increasing the entropy of the cause-effect repertoires of mechanisms within a complex expands the characteristics and meaning of concepts, but at the expense of the cause-effect information associated with each concept. This provides an elegant explanation for the need to optimize neural entropy.

Psychedelic drugs push the brain into a slightly higher entropy state, which is more experientially rich and flexible, but less informative than normal waking consciousness. This is because high entropy states contain a greater uncertainty about the past states that caused the current state, and those that will follow it.

By considering how psychedelics restructure concepts, we can see that some concepts share a non-zero number of states, which makes perfect sense, since not all concepts are independent.

As the entropy of the cause-effect repertoire increases, conceptual overlap between certain concepts will inevitably increase, potentially even between those that are not normally related. This could degrade the brain’s ability to maintain the organization and differentiation of the concepts within conscious experience.

“The lady next door, whom I scarcely recognized…was no longer Mrs. R., but rather a malevolent, insidious witch with a colored mask.” (Hofmann, 1980)

Hofmann’s psychedelic experience could be interpreted as the conceptual blending of the concept of Mrs. R with the concept of a malevolent witch, and a failure to distinguish concepts related to self from concepts related to other.

A study by Carhart-Harris et al. (2014) suggests that the brain’s entropy must be suppressed to maximize cause-effect information and maintain the organization, categorization, and differentiation of concepts, but this does not mean that the psychedelic state of consciousness is without value.

The Effect of Psychedelic Drugs on Neural Integration

So far, only the effects of psychedelic drugs on neural differentiation has been considered. However, the maximally integrated conceptual structure is likely to be highly dynamic, and may include more than just the high 8 complex.

Neural integration is commonly measured by the synchronization of neural activation, but it is important to distinguish between functional and effective connectivity. Effective connectivity describes the causal influence of neural systems over each other.

The synchronization of neural oscillations across a range of frequency bands has become the dominant model to explain how integration is achieved, and specific thalamocortical circuits regulating information transfer between disparate cortical regions have been invoked as a model for hallucinations and perceptual aberrations that occur during psychosis and certain psychedelic states. Fast-spiking inhibitory interneurons in the brain generate cortical gamma oscillations, which are regulated by 5HT1A and 5HT2A receptors. The gamma oscillations are closely associated with neural integration, and the psychedelic state might be characterized by an increase in integration. Studies that used quantitative EEG to measure changes in oscillatory power and coherence following ayahuasca ingestion observed a highly integrated brain state, but other studies found generalized decreases in power across all frequency bands. A recent MEG study of psilocybin subjects suggested that the psychedelic state is one of disintegrated neural activity, but a later fMRI study showed that the post-psilocybin state was characterized by an increase in the degree of integration between cortical areas.

Although functional connectivity and coherence analyses are highly suggestive, they do not necessarily imply effective connectivity, and thus a definitive account of the effect of psychedelic drugs on neural integration across the brain must be considered.

Measurement of Integrated Information in the Psychedelic State

Although psychedelic drugs are associated with increased neural entropy and reduced differentiation between network states, most individuals feel a heightened sense of alertness and awareness under the influence of a psychedelic drug.

Transcranial magnetic stimulation coupled with EEG can be used to measure the response of the brain to direct perturbation of targeted cortical regions. This approach separates effective connectivity (causal interactions) from functional connectivity (temporal correlations).

The Perturbational Complexity Index (PCI) is a measure of integrated information used to differentiate between levels of consciousness in both healthy individuals and those with severe neurological injury. It is conceivable that the PCI could detect any difference in the level of consciousness between normal wakefulness and the psychedelic state.

Conclusions, Predictions, and Future Work

The brain’s task in shaping conscious experience has been framed as a problem of minimizing entropy whilst maintaining cognitive flexibility. Psychedelic drugs increase cognitive flexibility but sacrifice a degree of cause-effect information specified by each mechanism (concept) within the conscious complex.

Despite reducing cause-effect information, the classic psychedelics do not appear to reduce consciousness. Instead, they seem to increase consciousness by expanding the number of states within the cause-effect repertoires of individual mechanisms, reducing the differentiation between network states and resulting in a state of unconstrained cognition and expanded awareness.