Expecting the Unexpected: The Paranoid Style of Belief Updating Across Species

• Main Author: Reed, Erin J
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2019
• Subjects: Neurosciences
• ISBN: 9798607320607

Delusions, the fixed false beliefs characteristic of psychotic illness, have long defied understanding despite response to pharmacological treatments. Computational neuroscience and associative learning theory assist in explaining their development and persistence. Beliefs, in humans and other animals, may be defined as associations between representations (e.g., of cause and effect) formed by minimizing uncertainty via new learning and attentional allocation. We propose that organisms strive to minimize uncertainty about their future states by forming and maintaining a hierarchy of beliefs about the organism and the world that are robust, but flexible. If irreducible uncertainty is generated at the highest levels, beliefs may manifest a rigidly flexible style characteristic of delusions. Here, we combine computational modeling with an associative learning task to examine belief-updating across rodents and human participants. We focus on participants endorsing a subset of delusion-like ideation that is particularly prominent within the general population: paranoia. We hypothesize that individuals with paranoia exhibit deficits in fundamental uncertainty-driven belief updating processes that extend beyond social threat perception. Our results show that paranoia is associated with a strong but immutable prior on volatility, accompanied by elevated sensitivity to perceived changes in the task environment. These manifest as context-insensitive, promiscuous choice switching in humans as well as rodents administered methamphetamine, an elicitor of paranoia in humans. Our work provides proof of principle for the translational power of computational psychiatry. It further underscores the importance of stable relationships in the treatment of paranoia and offers potential mechanisms for exacerbation of ideological intolerance during times of stress, instability, and uncertainty.