Delusions and Imagination

Predictive processing theories of delusions and hallucinations suggest a simple dysfunction as the core of these puzzling symptoms. Perception, belief, and action are all cast in terms of inferences, wherein prior beliefs are integrated with sensory inputs based on their relative reliabilities. Delusions and hallucinations then arise when this integration process is perturbed, either toward priors (hallucinations) or sensory inputs (delusion formation). However, there are other popular theories of delusions and hallucinations, including models that suggest delusions and hallucinations involve confusing imagining for believing or perceiving respectively. In this chapter, I will attempt to reconcile these accounts with predictive processing theory, appealing to associative and reinforcement learning data that integrate imaginative mechanism, including representation mediated learning, which may bring source monitoring and imagination accounts under the explanatory umbrella of predictive coding theory. I will end by speculating on a neurocomputational architecture that may underlie predictive processing and makes use of generative, imaginative, processes in service of reality perception. Dysfunction in this network can give rise to hallucinations, delusions, and other perturbations of conscious experience.