عدم تقارن مغز کاربردی و ساختاری در بیماران مبتلا به اختلالات اسکیزوفرنی و اختلال دوقطبی

Objectives This study aimed to compare the functional and gray matter asymmetries in patients with schizophrenia (SZ), patients with bipolar disorders (BD), and healthy controls (HCs) to test whether decreased leftward functional hemispheric lateralization and gray matter volume asymmetry could mark the boundary between schizophrenia and bipolar disorder. Methods A total of 31 right-handed SZ and 20 right-handed BD underwent a session of functional MRI with a speech listening paradigm. Participants were matched with HCs for gender, age, and education. Functional laterality indices (FLI) and gray matter volume asymmetry indices (GVAI) were computed from the individual functional language network. Correlations between the FLI and GVAI indices were also examined. Results SZ exhibited significantly decreased leftward functional hemispheric lateralization whereas BD did not. The GVAIs did not differ significantly between SZ and HCs or between BD and HCs. There were positive correlations between GVAIs and FLIs in all groups. Conclusions Loss of laterality for language comprehension with retention of gray matter volume asymmetry indicates that gray matter loss alone will not account for the pathophysiology of schizophrenia. Impaired leftward functional hemispheric lateralization for language but not gray matter volume asymmetry can be considered a biomarker of SZ. Abbreviations AHRS, Auditory Hallucinations Rating Scale; ARS, Association de Recherche pour la Schizophrénie; BD, bipolar disorders; CS, comprehension score; DSM-IV, Diagnostic and Statistical Manual of Mental Disorder 4th edition; FLI, functional laterality index; FLIint, intermediate functional laterality index; FWE, family-wise error; GVAI, gray matter volume asymmetry index; GVAIint, intermediate gray matter volume asymmetry index; HC, healthy control; HCL-20, hypomania checklist; HRSD, Hamilton Rating Scale for Depression; MNI, Montreal Neurological Institute; MRI, magnetic resonance imaging; nCS, normalized comprehension score; PANSS, Positive and Negative Syndrome Scale; SPM, Statistical Parametric Mapping; SZ, schizophrenia

Specificity of cerebral markers in patients with schizophrenia (SZ) or bipolar disorders (BD) must be considered in light of the debate on the nosological delimitation of the two disorders (Lake and Hurwitz, 2007). Few functional magnetic resonance imaging studies investigating language networks have sought to identify cerebral biomarkers to discriminate these patient groups (McIntosh et al., 2008, Maïza et al., 2010 and Whalley et al., 2012). Nevertheless, some authors have reported decreased leftward functional lateralization for language in SZ patients (Sommer et al., 2003, Dollfus et al., 2005, Van Veelen et al., 2011 and Sheng et al., 2013), and one previous study suggested that change in functional hemispheric lateralization for language could be a biomarker of SZ (Alary et al., 2013b). However, gray matter volume changes in language structures in SZ and BD patients have been little investigated (Ratnanather et al., 2013). Therefore, the present study compared functional and gray matter asymmetries among SZ patients, BD patients, and healthy controls (HCs). We hypothesized that decreased leftward functional hemispheric lateralization and gray matter volume asymmetry in a language network would be specifically observed in SZ patients but not in BD patients.