Reduced Precision Underwrites Ego Dissolution and Therapeutic Outcomes Under Psychedelics

Abstract

Evidence suggests classic psychedelics reduce the precision of belief updating and enable access to a range of alternate hypotheses that underwrite how we make sense of the world. This process, in the higher cortices, has been postulated to explain the therapeutic efficacy of psychedelics for the treatment of internalizing disorders. We argue reduced precision also underpins change to consciousness, known as "ego dissolution," and that alterations to consciousness and attention under psychedelics have a common mechanism of reduced precision of Bayesian belief updating. Evidence, connecting the role of serotonergic receptors to large-scale connectivity changes in the cortex, suggests the precision of Bayesian belief updating may be a mechanism to modify and investigate consciousness and attention.

Keywords: belief updating; ego dissolution; hierarchical predictive coding; precision; psychedelics.

FIGURE 1

Illustration of desegregated connectivity under psilocybin, inspired by Petri et al. (2014). Change between cortical communities’ diversity of connectivity under psilocybin suggests a foundation of subjective effects (and facet of ego dissolution) that may be underwritten by reduced precision (i.e., confidence) of belief updating enabling connectivity to select from a wider range of hypotheses.

FIGURE 2

Simplified illustrative description of precision of belief updating along the cortical hierarchy. (A) Precision is represented along scales of the hierarchy and depicts the filtration of sensory impressions to cognition. Predictions and prediction errors can be seen to interact between each layer of the hierarchy, with stronger high-level predictions in the upper levels of the hierarchy. (B) Under psychedelics the precision of belief updating in high level predictions, involved in phenomenal consciousness and narrative self, is reduced. This occurs by belief updating opening alternate hypotheses that undergird neuronal populations “confidence” in the selection, and salience, of attention that integrate phenomenal consciousness and narrative self-identity. Reduced precision is represented by the reduced weight of predictions and increased influence of prediction errors in higher levels of the hierarchy where 5-HT2A receptors are abundant. The change to the precision of belief updating is hypothesized to result in ego dissolution. Elements of this model are inspired by Carhart-Harris and Friston (2019).