M15. MORPHOLOGY OF THE SUPERIOR TEMPORAL SULCUS IN PATIENTS WITH SCHIZOPHRENIA: A MARKER OF GENETIC OR ENVIRONMENTAL VULNERABILITY?

Background Hallucinations are the most common and debilitating symptom in schizophrenia, affecting more than 70% of patients. The superior temporal sulcus (STS) is involved in the language process notably in the perception of the human voice and several studies show its implication in auditory verbal hallucinations (AVHs). Sulcal patterns in the white matter can reflect an early vulnerability, probably genetic since they set up at a very early stage and are stable over the life course. In contrast, the cortical thickness is dynamic and variable over the development and so can reflect the impact of environmental factors on the maturation of the brain. The aim of this study is therefore to determine whether AVHs are associated with morphological changes of the STS and in particular, whether these changes concern sulcal patterns or cortical thickness reflecting early (genetic) or late (environmental) vulnerability respectively. Methods Seventy-three schizophrenia patients (DSM-IV) with a proneness of AVH (53 AVH+) and without AVH (20 AVH-) and 100 healthy volunteers (HC) had a 3T MRI brain scan. Cortical reconstructions were generated using Freesurfer. Mean cortical thickness was measured over the entire brain in each participant. Number of sulcal pits, which represents the position with the maximum depth in the sulcus, was automatically counted on the white matter surface. Both measures were compared between groups and related to the Auditory Hallucination Rating Scale (AHRS). Results AVH+ patients compared to HC showed a significantly thinner cortical thickness in the left temporal and frontal regions and especially in the STS (p ≤ 0.05 FDR corrected). A negative correlation (r²=0.25) between the cortical thickness in the central part of the left STS and the AHRS score was found (p = 0.01 uncorrected). A different distribution of the number of pits in the left STS is found in AVH+ patients compared to HC (p = 0.05). Discussion The results suggest that AVH+ patients compared to HC have a lower cortical thickness in the left STS, but also have a specific white matter pattern of the left STS. These results support the hypothesis that a particular morphology of the STS related with auditory hallucinations might be due to both early (genetic) and late (environmental) factors.