title: Homotopic connectivity in drug-naïve, first-episode, early-onset schizophrenia.
abstract: BACKGROUND
  The disconnection hypothesis of schizophrenia has been extensively tested in adults. Recent studies have reported the presence of brain disconnection in younger patients, adding evidence to support the neurodevelopmental hypothesis of schizophrenia. Because of drug confounds in chronic and medicated patients, it has been extremely challenging for researchers to directly investigate abnormalities in the development of connectivity and their role in the pathophysiology of schizophrenia. The present study aimed to examine functional homotopy - a measure of interhemispheric connection - and its relevance to clinical symptoms in first-episode drug-naïve early-onset schizophrenia (EOS) patients.
  
  
  METHODS
  Resting-state functional magnetic resonance imaging was performed in 26 first-episode drug-naïve EOS patients (age: 14.5 ± 1.94, 13 males) and 25 matched typically developing controls (TDCs) (age: 14.4 ± 2.97, 13 males). We were mainly concerned with the functional connectivity between any pair of symmetric interhemispheric voxels (i.e., functional homotopy) measured by voxel-mirrored homotopic connectivity (VMHC).
  
  
  RESULTS
  Early-onset schizophrenia patients exhibited both global and regional VMHC reductions in comparison with TDCs. Reduced VMHC values were observed within the superior temporal cortex and postcentral gyrus. These interhemispheric synchronization deficits were negatively correlated with negative symptom of the Positive and Negative Syndrome Scale. Moreover, regions of interest analyses based on left and right clusters of temporal cortex and postcentral gyrus revealed abnormal heterotopic connectivity in EOS patients.
  
  
  CONCLUSIONS
  Our findings provide novel neurodevelopmental evidence for the disconnection hypothesis of schizophrenia and suggest that these alterations occur early in the course of the disease and are independent of medication status.
authors.affiliation: Key Laboratory of Behavioral Science and Magnetic Resonance Imaging Research Center, Institute of Psychology, Chinese Academy of Sciences, Beijing, China; Laboratory for Functional Connectome and Development, Institute of Psychology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Hui-Jie
authors.initials: HJ
authors.lastname: Li
authors.forename: Yong
authors.initials: Y
authors.lastname: Xu
authors.forename: Ke-Rang
authors.initials: KR
authors.lastname: Zhang
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Hoptman
authors.forename: Xi-Nian
authors.initials: XN
authors.lastname: Zuo
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D063132:Connectome; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D017397:Prefrontal Cortex / Q000503:physiopathology*; D012559:Schizophrenia / Q000503:physiopathology*
keywords: Resting-state fMRI; early-onset schizophrenia; functional connectivity; interhemispheric connectivity