Sadness-specific speech-in-noise impairments and subregional left insular volume reduction in schizophrenia with auditory verbal hallucinations

This study investigated the association between regional volumes of the left insula, emotional speech-in-noise recognition (ESR), and auditory verbal hallucinations (AVHs) in individuals with schizophrenia. Fifty‑eight patients were categorized into two groups according to the PANSS P3 score: AVHs (n = 19) and non‑AVHs (n = 39). All participants completed ESR tasks and underwent structural MRI for volumetric analysis. Compared to the non-AVH group, patients with AVHs exhibited impaired ESR of sadness and reduced gray matter volumes in five left insular subregions. However, group differences in ESR performance became non-significant after controlling for PANSS cognitive symptoms, and volumetric differences were attenuated after adjusting for sex, negative symptoms, and cognitive symptoms. Following normalization to total intracranial volume, patients with AVHs still exhibited smaller volumes in the left insula, specifically in two subregions of the left ventral and dorsal agranular insula. Moreover, volumes in the dorsal agranular and dysgranular insula were significantly correlated with both AVH severity and ESR performance. These findings suggest that structural abnormalities in specific left insular subregions may underlie to emotional speech processing deficits in schizophrenia, highlighting potential neuroanatomical biomarkers and intervention targets in patients with AVHs. Given that AVH grouping was based on current symptoms (past week) rather than lifetime history, this limitation should be considered in future studies when interpreting the present findings.