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The study of brain gyrification may provide useful information on the cytoarchitecture and connectivity of the brain. One of the methods that have been developed to estimate brain gyrification, known as surface ratio (SR), has not yet been studied in schizophrenia. Here we aimed to assess whether SR could provide new insights on the brain structure of schizophrenia patients and the severity of symptoms. We also computed a more established brain gyrification measure, namely absolute mean curvature (AMC). We analyzed 63 magnetic resonance images, 25 from schizophrenia patients with treatment-resistant auditory verbal hallucinations (SCH-H), 18 from schizophrenia patients without hallucinations (SCH-NH), and 20 from healthy controls (HC). The SR measure revealed that SCH-H patients had a more folded orbitofrontal cortex than SCH-NH patients and HC. Gyrification in this region was also negatively associated with positive symptoms, specifically with the delusions and conceptual disorganization items, only in the SCH-H group. Regarding the AMC measure, we identified two areas where HC showed more gyrification than SCH-H patients, but no relationships arose with symptoms. The hypergyrification of the orbitofrontal cortex displayed by SCH-H patients, as captured by the SR measure, suggests aberrant and/or excessive wiring in these patients, which in turn could give rise to auditory verbal hallucinations. Alternatively, we comment on potential compensatory mechanisms that may better explain the negative association between orbitofrontal gyrification and positive symptomatology. The SR measure captured the most relevant differences and associations, making it a promising biomarker in schizophrenia., Competing Interests: Conflicts of interest Dr. Roldán has served as advisor or speaker for the companies Otsuka, Rovi and Angelini (unrelated to the present work). The rest of the authors have nothing to disclose., (Copyright © 2024. Published by Elsevier B.V.)

The aim of this study is to analyze the differences in low frequency fluctuation (LFF) values between schizophrenia patients with and without auditory verbal hallucinations (AVH). Nineteen schizophrenia patients with persistent AVH (HP), fourteen non-hallucinating schizophrenia patients (nHP) and twenty healthy controls (HC) underwent R-fMRI. LFF values were calculated in the slow frequency band (0.01-0.08Hz). By means of group level contrasts, we performed direct voxel-wise group comparisons. Both groups of patients showed decreased amplitude LFF (ALFF) values in the occipital pole and lingual gyrus compared to HC, whereas increased ALFF values were found in the temporal pole and fusifom gyrus. Schizophrenia patients exhibited decreased fractional ALFF (fALFF) values in the precuneus, occipital pole and bilateral occipital cortex, and increased fALFF in the insula compared to HC. There were also differences between patients with and without AVH. (Ok to start with lower case?) fALFF values were higher in the putamen and insular cortex and lower in the frontal pole in HP compared to nHP and HC. ALFF increased in HP patients in the bilateral thalamus and bilateral parahippocampal gyrus, compared to nHP patients and HC. Our results suggest that altered dynamics in low-frequency fluctuations may play a key role in the neurophysiology of auditory hallucinations., (Copyright © 2017 Elsevier B.V. All rights reserved.)