Volumetric MRI correlates of persistent auditory verbal hallucinations and olfactory identification impairment in chronic schizophrenia: A cross-sectional study

Olfactory impairments are often observed in schizophrenia (SCZ) patients experiencing persistent auditory verbal hallucinations (pAVHs), yet it remains unclear whether these symptoms share a common neural mechanism with specific brain regions' gray matter volume (GMV) abnormalities. This study aimed to preliminarily elucidate olfactory impairment differences between SCZ patients with and without pAVHs and their correlation with GMV abnormalities in relevant brain regions. A total of 75 SCZ patients with pAVHs (pAVH group), 56 SCZ patients without AVHs (non-AVH group), and 83 healthy controls (HC group) were examined. Voxel-based morphometry is useful for comparing and analyzing the differences in GMV among three groups. The Odor Stick Identification Test for Japanese (OSIT-J) was harnessed to gauge olfactory abilities. Olfactory impairments are notably significant across entire SCZ patients compared to HC, with no significant differences in olfactory performance among SCZ subgroups. Notably, the pAVH group demonstrated a significant GMV diminution in the frontal-temporal cortex, starkly contrasting with the non-pAVH and HC groups. Intriguingly, stepwise regression analysis confirmed a strong positive relation between OSIT-J scores and a GMV reduction in the right medial orbitofrontal cortex (mOFC), although this correlation was only observed in the overall SCZ patient group (P