Psychedelics and schizophrenia: Distinct alterations to Bayesian inference
Hardik Rajpal, Pedro A.M. Mediano, Fernando E. Rosas, Christopher B. Timmermann, Stefan Brugger, Suresh Muthukumaraswamy, Anil K. Seth, Daniel Bor, Robin L. Carhart-Harris, Henrik J. Jensen
bioRxiv February 1, 2022 preprint DOI: 10.1101/2022.01.31.478484
Summary
AI-generated from the abstractSchizophrenia and drug-induced states from LSD and ketamine both increase neural signal diversity, but they differ in how information flows in the brain. In schizophrenia, transfer entropy from the front to the back of the brain is increased, whereas under both drugs it is reduced overall. These differences can be modeled by altering Bayesian inference within a predictive processing framework: drug effects correspond to reduced precision of prior beliefs, while schizophrenia corresponds to increased precision of sensory information. The findings clarify similarities and differences between these altered states, with potential implications for understanding consciousness and developing mental health treatments.
Study at a glance
| Characteristics | Observational study |
|---|---|
| Population | Healthy volunteers |
| Interventions | LSD ketamine |
| Keywords | Predictive mechanisms Belief updating Brain prediction Cognitive processing Uncertainty processing |
| Citations | 5 |
| Key finding | Schizophrenia and LSD/ketamine states both increase neural signal diversity but show opposite changes in front-to-back transfer entropy, modeled as altered precision in Bayesian inference. |
Abstract
Abstract Schizophrenia and states induced by certain psychotomimetic drugs may share some physiological and phenomenological properties, but they differ in fundamental ways: one is a crippling chronic mental disease, while the others are temporary, pharmacologically-induced states presently being explored as treatments for mental illnesses. Building towards a deeper understanding of these different alterations of normal consciousness, here we compare the changes in neural dynamics induced by LSD and ketamine (in healthy volunteers) against those associated with schizophrenia, as observed in resting-state M/EEG recordings. While both conditions exhibit increased neural signal diversity, our findings reveal that this is accompanied by an increased transfer entropy from the front to the back of the brain in schizophrenia, versus an overall reduction under the two drugs. Furthermore, we show that these effects can be reproduced via different alterations of standard Bayesian inference applied on a computational model based on the predictive processing framework. In particular, the effects observed under the drugs are modelled as a reduction of the precision of the priors, while the effects of schizophrenia correspond to an increased precision of sensory information. These findings shed new light on the similarities and differences between schizophrenia and two psychotomimetic drug states, and have potential implications for the study of consciousness and future mental health treatments.