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Overweighting of prior knowledge during predictive language processing is associated with psychotic-like symptoms

Elisabeth F. Sterner (presenting), Lucy MacGregor, Verena Demler, Christoph Mathys, Franziska Knolle


Background: Impaired language processing is a core symptom of psychosis and is critically involved in shaping positive (e.g., auditory hallucinations) and negative symptoms (e.g., social withdrawal). Hierarchical Bayesian accounts of psychosis suggest an imbalance in the weighting of prior beliefs and incoming sensory information to be an underlying mechanism of symptom development. Thus, the goal of this study was (1) to investigate the use of semantic prior beliefs relative to sensory information during predictive language processing as a trait marker for early psychotic-like symptoms and (2) to explore the underlying oscillatory signatures of potential alterations.

Methods: 37 participants assessed for psychotic-like symptoms completed a predictive language paradigm while their brain activity was recorded with EEG. In the task, participants listened to sentences of varying predictability, with the sentence-final words being degraded in clarity. They were asked to report the word they perceived to assess conditioned hallucinations. To estimate the relative strength of semantic prior beliefs over the sensory input, we applied Bayesian regression modelling and investigated the neurophysiological underpinnings with EEG.

Results and Conclusion: Bayesian regression modelling revealed an overweighting of prior beliefs relative to sensory information with increasing psychotic-like symptoms. On a neurophysiological level, we found that this was linked to a stronger prediction-related alpha power (8-12 Hz) decrease. Interestingly, the overweighting of semantic prior beliefs was also associated with experiencing more conditioned hallucinations. In conclusion, the present findings may provide an initial mechanistic explanation of how suboptimal predictive language processing contributes to the formation of hallucinations.