Project Summary/Abstract Theories about the origin of perceptual abnormalities (attenuated hallucinations) have been evoked for centuries. One competitive theory is that perceptual abnormalities can be explained by atypical predictive coding. The predictive coding theory states that individuals use prior knowledge to create a mental model of the environment and that mismatches of expectancy and experience lead to an updating of the prior mental model. In people on the psychosis spectrum, more weight is given to the prior models and belief updating does not occur. According to this theory, people who experience perceptual abnormalities misattribute the prior expectation as a sensation leading to a perceptual experience. Adjacently, recent research in non-psychiatric populations has investigated the mechanisms of mental imagery. When imagined signals are strong enough, they can become subjectively indistinguishable from reality. Taking this novel research into account, it may be possible that the vividness of mental imagery may affect the strength of prior beliefs and make it more or less likely to experience perceptual abnormalities. Thus far, the role of mental imagery in the predictive coding theory of perceptual abnormalities has not been explored. The proposed study will examine the role of mental imagery in predictive coding using samples of people at clinical high-risk for psychosis (CHR) who experience perceptual abnormalities (N = 40), CHR individuals who do not experience perceptual abnormalities (N = 40), and healthy controls (N = 40). Participants will partake in a clinical and cognitive assessment, including two novel mental imagery tasks that instruct participants to imagine a sound or image and test their ability to differentiate between imagined and real stimuli later in the task. Additionally, participants will complete a self- report questionnaire about their mental imagery and perform a predictive coding task. Using this data, the study will investigate three aims to understand whether the vividness of mental imagery relates to the presence of perceptual abnormalities and if this improves the predictive coding model. Aim 1: validate the mental imagery task and mechanisms in the CHR population. Aim 2: assess whether the vividness of mental imagery relates to the severity of perceptual abnormalities. Aim 3: examine whether mental imagery can be incorporated into the predictive coding model. Training Plan: to complete this project and build an independent research career the applicant will (a) develop an understanding of theories and mechanisms of hallucination formation, (b) gain comprehensive experience with building and interpreting computational models, and (c) learn the principles and applications of structural equation modeling. This training will be accomplished through regular meetings with a team of expert scholars, coursework, workshops, and attending conferences. Training Environment: The training will take place at North...