Abstract: There has been an increasing interest in the neurocomputational mechanisms underlying psychotic disorders in recent years. One promising approach is based on the theoretical framework of predictive processing, which proposes that inferences regarding the state of the world are made by combining prior beliefs with sensory signals. Delusions and hallucinations are the core symptoms of psychosis and often co-occur. Yet, different predictive-processing alterations have been proposed for these two symptom dimensions, according to which the relative weighting of prior beliefs in perceptual inference is decreased or increased, respectively. I will present recent behavioural, neuroimaging, and computational work that investigated perceptual inference to elucidate the changes in predictive processing that may give rise to psychotic experiences. Based on the empirical findings presented, I will provide a more nuanced predictive-processing account that suggests a common mechanism for delusions and hallucinations at low levels of the predictive-processing hierarchy, but still has the potential to reconcile apparently contradictory findings in the literature. This account may help to understand the heterogeneity of psychotic phenomenology and explain changes in symptomatology over time.

Bio: Philipp Sterzer is a psychiatrist, neurologist and neuroscientist who trained in Frankfurt am Main, London and Berlin and held a professorship for psychiatry and computational neuroscience at Charité Berlin from 2011 to 2022. Recently, he was appointed Professor of Translational Psychiatry at University of Basel, Switzerland. His work focuses on the investigation of predictive neural processes in perception and their alterations in psychotic disorders using functional neuroimaging and computational modeling among other methods. Along with numerous articles in scientific journals and textbooks, he recently published “Die Illusion der Vernunft”, a popular science book on delusions and other irrational beliefs.