Cerebellum as a neural substrate for impoverishment in early psychosis.

BACKGROUND: Formal Thought Disorder and includes both positive (i.e., disorganized speech) and negative (i.e., impoverished speech) symptoms. Emerging evidence suggests that the cerebellum plays a critical role in cognitive functions, including language processing. This study leverages Natural Language Processing to objectively measure language disturbances in patients with first-episode psychosis and investigates the relationship between these disturbances and cerebellar structure. METHODS: Fifty-four patients with schizophrenia, either drug-naïve or minimally medicated, were recruited from an early psychosis program. Impoverished thought was assessed using the Thought Language Index while lexico-semantic features (affect, cognitive, linguistic, perception, time) were identified from speech samples analyzed using the Linguistic Inquiry Word Count-22 software. Structural cerebellar analysis was completed on 7.0 Tesla MRI scans using voxel-based morphometry (VBM) to measure global and regional grey matter volume changes. RESULTS: Linear regression analysis revealed that reduced perceptual word usage was the strongest predictor of impoverished thinking. Correlational analysis identified reduced cerebellar volumes in patients with lower LIWC-based perception scores. VBM localized this relationship to a cluster in the right posterolateral cerebellar hemisphere, an area related to executive demand and verb generation function. CONCLUSION: The cerebellum contributes to impoverished thinking in early psychosis, likely by influencing the lexical expression of perceptual experiences. This underscores the cerebellum's role in higher-order cognitive processes relevant to psychotic disorders and its potential as a therapeutic target for language and cognitive deficits in schizophrenia.