Entropic Brain Theory & Psychedelics: A Prelude to REBUS
Written by Justin Belko
In 2019 Dr. Robin Carhart-Harris and neuroscientist Karl Friston published REBUS and the Anarchic Brain. This joint work was invaluable to the field of psychedelic medicine, providing a unified framework for how psychedelics might act on the brain and their effect on cognition, habits, and behaviors. The work builds on a great deal of preexisting neuroscience and psychedelic research, as well as their own hypothesis: Entropic Brain Theory and Free Energy Principle. In light of the large volume of background information making up REBUS, it is ideal that the reader first understands the Entropic Brain Theory.
During day-to-day life, entropy is limited to keep informational complexity at a manageable level. The brain’s default mode network (DMN), a group of functionally related brain regions, is responsible for maintaining the brain's status quo, yet this state is temporarily disrupted by psychedelic substances [2-4]. For a more in-depth look at the DMN and psychedelics, read “The Default Mode Network and Ego Dissolution: Not So Cut and Dry”.
Entropy and the Brain
Upon hearing the word entropy, many might think of physics and the laws of thermodynamics. Fortunately, the connotation here is quite similar. For readers who aren't familiar, entropy is the measure of disorder in any given system, in this case, that system is the brain [1].
The entropic brain theory asserts that one’s subjective experience, that is the depth and qualities of one’s consciousness, is heavily determined by the level of entropy in the brain. Higher levels of entropy correspond to greater levels of disorder and uncertainty in the mind [2]. While this reduction in cognitive order may result in racing thoughts or confusion it is not necessarily a negative occurrence. It can lead to one gaining insight and a new perspective on ideas or world views, allowing one to connect ideas in a fashion previously unknown to them. A hallmark of high-level entropic brain states is also increased depth of experience. In other words, one's subjective conscious experience may seem more vivid or “complete” when compared to their ordinary waking state.
During day-to-day life, entropy is limited to keep informational complexity at a manageable level. The brain’s default mode network (DMN), a group of functionally related brain regions, is responsible for maintaining the brain's status quo, yet this state is temporarily disrupted by psychedelic substances [2-4]. For a more in-depth look at the DMN and psychedelics, read “The Default Mode Network and Ego Dissolution: Not So Cut and Dry”.
States of Consciousness
Heavily inspired by Freudian psychology, the Entropic Brain Theory asserts that consciousness can exist in two states: Primary consciousness and secondary consciousness [5]. Primary consciousness, also known as primary process thinking, is suggested to be similar to that of early man, instinctual, and harken back to an era before the development of one’s sense of self. Primary consciousness lacks a great deal of entropy suppression and is exemplified in REM sleep, psychedelic experiences, and early-stage psychosis [2,6]. Secondary consciousness is one’s normal waking state and is characterized by an intact sense of ego/self, and an ordered, disciplined mind with rational and logical thought patterns, traits that are valuable for survival, especially for early man.
The entropic brain theory suggests that by increasing entropy, psychedelics temporarily shift an individual from a secondary state to a primary state of consciousness [2,7]. One might assume given the advantages secondary consciousness confers in a survival setting that it is a more effective state of existence overall, but this is not the case. Despite a realistic and order-bound manner of thought, secondary states have their shortcomings.
This is most evident in patients with depression. Major depressive disorder (MDD) is often characterized by negative intrusive thinking. Ruminative and unrelenting, an individual often cannot shake their detrimental thought patterns. [8] It’s undeniable that for those experiencing MDD, upholding the brain’s rigid, status quo in a state of secondary consciousness is not always advantageous. Similarly, the rigidity and order of the secondary state are disadvantageous to those suffering from OCD and addiction [9-11].
It is suggested that psychedelics' ability to shift the brain into primary consciousness, where beliefs and habits are more flexible and malleable plays a key role in its therapeutic efficacy for depression and addiction [12-14].
Criticality
To better illustrate primary and secondary states, the entropic brain theory also proposes a spectrum of criticality, in which consciousness exists. All conscious states are theorized to exist in a zone poised between high order and high disorder (entropy). Our waking consciousness, that is our normal conscious state, lies closer to order than entropy [2].
Psychedelics are proposed to increase entropy, moving the brain towards a state of super-criticality characterized by greater depth and informational richness. The supercritical state psychedelics elicit also corresponds to heightened sensitivity to stimulus, which helps to explain the importance of set and setting during psychedelic experiences [15].
In contrast sedatives/anesthetics move the brain towards a subcritical zone where there is less informational depth. Surprisingly, psychedelics, much like sedatives/anesthetics can cause loss of consciousness depending on the dose administered. This loss of consciousness at higher doses is theorized to be a result of the brain leaving the critical zone where consciousness is readily supported [16].
Pharmacology of Psychedelics
For readers who aren't familiar, classic psychedelic drugs are generally considered to be tryptamines, ergolines, and phenethylamines, with LSD, psilocybin, DMT, and mescaline falling into these classes [17-18]. Classic psychedelics are exemplified by their method of action being serotonin receptor 5-HT2A agonism (activation).
Psychedelics activate multiple serotonin receptors but activation of the 5-HT2A receptor is critical to the psychedelic experience [19]. Blocking the 5-HT2A receptor before administration of a psychedelic compound prevents the psychedelic experience [20,21]. Unsurprisingly 5-HT2A receptor concentration is the highest amongst brain regions that make up the DMN [22].
Serotonin and Neuroplasticity
The neurotransmitter serotonin is often mistaken for the role it plays in the brain. Unlike dopamine, recent findings show it does not play a role in the brain's reward system and instead plays a role in an organism's adaptability [23].
It is suggested serotonin increases an organism's ability to adapt in two ways: 1) By passively increasing an organism's stress resiliency and 2) By increasing the plasticity of the brain which allows easier acquisition of new beliefs and adaptive behaviors [24].
Scientific literature over the decade has illustrated the importance of neuroplasticity for mental and emotional health. Not only does neuroplasticity seemingly act as a protective factor against cognitive impairment and mental illness, but its reduction is implicated in negative affective disorders such as depression and anxiety [32].
Consider the quintessential sled riding experience. After repeatedly sledding down an incline, one tends to get stuck in the paths they’ve used before, making it increasingly harder to escape from these ruts. Yet when a fresh snowfall occurs, these paths are wiped away and one is free to take any route they want. When sledding, this isn’t necessarily a bad thing; the same principle can be applied to the human mind.
As beings of habit and assumption, we tend to maintain structure and order, reflected sometimes in an inability to shake old habits and beliefs. This rigidity exists even when it no longer serves us, or is detrimental. The rumination that accompanies depression and anxiety as well as the impulsive tics in individuals with OCD exemplify our sometimes debilitating inability to rid ourselves of maladaptive habits [8,9,33]. This is not a lack of willpower but rather a feature of our neurobiology.
Psychedelics and their ability to promote behavioral and neurochemical change are akin to fresh snowfall, they act as a tool allowing people the cognitive flexibility to overcome maladaptive traits [2,16].
A Bigger Picture
It is important to remember that psychedelic neurosciences, along with the psychology of consciousness and cognition, are ever-growing fields and the Entropic Brain Theory is a part of a scientifically informed theory that is still evolving. With that said, Dr. Robin Carhart-Harris and Karl Friston are on the cutting edge of the field and since its 2014 publication, the Entropic Brain Theory has had a great deal of validation through neuroimaging and other empirical data.
The implications REBUS and the Anarchic Brain have on neuroscience, psychology, and psychedelic medicine are immense, and its relevance will only grow as the psychedelic renaissance continues. Through understanding a distilled framework for Entropic Brain theory, one will better comprehend the culminating work that is REBUS, ensuring they are well informed on the latest developments in psychedelic science.
