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).