Anh Pham¹ (), Scott R. Sponheim^2,1, Cheryl Olman¹; ¹University of Minnesota, ²Minneapolis VA Health Care System

Psychosis leads to the disruption of visual perception, which can be explained by the hierarchical predictive coding model as an impairment of the feedforward and feedback interactions between sensory input and prior knowledge. However, it is essential to have direct evidence from behavior and brain activity to support the model. Our study used an object recognition task with stimuli designed to control low-level features while varying recognizability. Using 7T fMRI, data were collected with 37 controls (CON), 15 bipolar disorder individuals (BP) and 5 relatives (BREL), and 19 people with schizophrenia (SCZ) and 10 relatives (SREL). Stimuli consisted of rough sketches of the outlines and textures of real-world objects formed by controlling the orientation of line segments on a grid. Three image conditions were high recognizability (meaningful - MF), low recognizability (meaningless - ML), and a baseline with randomized line segments. Regions of interest (ROIs) were V1, defined as the intersection of visually responsive voxels clustered in the calcarine sulcus, and post-hoc ROIs in fusiform, parietal, ventral temporal, lateral occipital (LOC), and prefrontal cortex, defined as clusters of voxels showing significant differences in responses to MF and ML stimuli. We found no significant group differences in BOLD responses to MF vs. ML objects in LOC; contrasts between ML objects and random were also generally consistent across groups, suggesting no significant differences in basic grouping processes. In contrast, the intraparietal sulcus and fusiform cortex showed greater BOLD enhancement to MF objects in SREL compared to ML than either SCZ or CON, and BP also showed larger response enhancements by object recognizability. This finding points toward higher visual areas, and differential use of prior knowledge, rather than low- and intermediate-level visual processing (edge detection and grouping) as a source of perceptual differences in psychosis patients and individuals with genetic liability for psychosis.

Acknowledgements: NIH R01 MH112583