Scott Sponheim¹, Joshua Stim², Victor Pokorny³; ¹Minneapolis VAMC / University of Minnesota, ²Johns Hopkins University, ³Northwester University

Introduction: Psychotic disorders, such as schizophrenia, are in part defined by disturbances in perception (e.g., hallucinations). Despite decades of research on visual perception in people with psychotic psychopathology the neural processes that underlie abnormal percept formation are unknown. Methods: To better understand the neural functions that may lead to abnormal perception we had 57 people with psychotic psychopathology (41 schizophrenia, 16 bipolar disorder with psychosis) 25 siblings of these people, and 43 healthy comparison participants complete a binocular rivalry task while magneto-encephalography (MEG) was recorded. Average percept durations during rivalry were computed from the behavioral responses of each participant. We also used SSVEPs derived from frequency-tagged stimuli of the two rival percepts to investigate neural activity related to information accumulation during perception. We submitted the time course of SSVEPs to a frequency decomposition to characterize the dominant frequency of the rise and fall of SSVEP power associated with perceptual switching. Results: Individuals with psychotic psychopathology and their siblings failed to differ from controls in their percept durations based on button presses related to changes in percept. Inspection of the frequency composition of the SSVEP time courses revealed a dominant .5 Hz frequency that appeared reduced in people with psychotic psychopathology compared to their siblings and control participants. Paired comparisons revealed that individuals with schizophrenia had lower power than controls at .5 Hz (t56.3 = -2.13, p =.038). This reduction was absent in individuals with bipolar disorder (t24.5 = -1.57, p =.129). Discussion: Our analysis of neural activity reflective of processing frequency-tagged stimuli during binocular rivalry revealed anomalies in neural information accumulation in people with schizophrenia. Reduced power of the dominant frequency within SSVEP time courses may represent reductions in neural activity that contribute to atypical percept formation in schizophrenia.

Acknowledgements: This work was funded by VA Merit Grant I01CX000227 and NIMH grant R01MH112583 (SRS as PI)