Supplementary Material for: Structural Analysis of Heschl’s Gyrus in Schizophrenia Patients with Auditory Hallucinations

Background/Aims: Heschl’s gyrus (HG) is functionally involved in the genesis of auditory verbal hallucinations (AVH). This dysfunction seems to be structurally facilitated. The aim of the study was to analyze macrostructural features of HG in a group of patients reporting AVH who demonstrated white matter diffusion tensor imaging abnormalities reported previously. Methods: 3-D anatomical MR scans were obtained (patients with and without history of AVH, controls). HG was delineated by manual segmentation. Cortical folding, absolute and relative volumes, laterality were analyzed. Results: According to the literature, in the collapsed group of patients, the normal left-greater-than-right laterality of HG was attenuated. We found a trend towards a higher number of duplicated HG in hallucinating patients. We also found a bigger volume of HG in the right hemisphere in hallucinating patients. This effect was caused by gray and white matter increase. Conclusions: This is the first study on manual volumetry of HG in a group of schizophrenia patients with AVH compared to patients without AVH. In a previous analysis of the diffusion tensor imaging data of the here presented sample, we found higher directionality of the arcuate fasciculus in patients with AVH, facilitating abnormal co-activation in the auditory cortices in the hallucinating brain. As these abnormal activations are frequent in hallucinating patients, the here described volume increase of HG might be interpreted as compensatory plastic adaptations of the contralateral regions. We suggest that this volume increase of HG is caused by the symptomatology and not by the underlying disorder of schizophrenia.