title: Left-hemisphere lateralization for language and interhemispheric fiber tracking in patients with schizophrenia.
abstract: BACKGROUND
  It has been suggested that the degree of hemispheric specialization (HS) depends on the structural connectivity between the two hemispheres, that is to say the corpus callosum (CC). Studies, performed only on healthy participants, investigated this anatomo-functional relationship. Nevertheless, it has never been studied in schizophrenia. We therefore propose to study the anatomo-functional relationships between the integrity of interhemispheric connectivity and leftward functional lateralization for language in patients with schizophrenia compared with healthy participants, driven by a multimodal approach combining fMRI and DTI-based fiber tractography. We hypothesized that reduced leftward functional lateralization for language in patients with schizophrenia could be related to a callosal hypoconnectivity.
  
  
  METHODS
  Seventeen patients based on the DSM-IV, and 17 controls were included. The functional laterality index and interhemispheric diffusion values between homologue temporal regions, belonging to the language network, were individually extracted in order to study the anatomo-functional relationships.
  
  
  RESULTS
  In the patients, higher mean and radial diffusivity (RD) values (thicker myelin sheaths) were associated with less leftward lateralization. In contrast, the controls presented higher RD values and lower fractional anisotropy values (axonal loss) with more leftward lateralization.
  
  
  CONCLUSIONS
  Our study revealed a relationship between the CC and the HS for language, but did not provide evidence clarifying the direction of the relationship between callosal connectivity and functional lateralization for language. In particular, the present findings showed that the loss of integrity in interhemispheric callosal fibers was associated with reduced leftward cerebral dominance for language in patients with schizophrenia.
authors: CHU de Caen, Service de Psychiatrie, Centre Esquirol, Caen F-14000, France; CNRS, UMR 6301 ISTCT, ISTS Team, GIP CYCERON, Bd Henri Becquerel, BP5229, F-14074 Caen cedex, France. Electronic address: eleroux@cyceron.fr.
authors: Elise
authors: E
authors: Leroux
authors: CNRS, UMS 3408, GIP CYCERON, Bd Henri Becquerel, BP5229, F-14074 Caen cedex, France. Electronic address: delcroix@cyceron.fr.
authors: Nicolas
authors: N
authors: Delcroix
authors: CHU de Caen, Service de Psychiatrie, Centre Esquirol, Caen F-14000, France; CNRS, UMR 6301 ISTCT, ISTS Team, GIP CYCERON, Bd Henri Becquerel, BP5229, F-14074 Caen cedex, France; Université de Caen Basse-Normandie, UFR de médecine (Medical School), Caen F-14000, France. Electronic address: dollfus-s@chu-caen.fr.
authors: Sonia
authors: S
authors: Dollfus
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D003337:Corpus Callosum / Q000098:blood supply / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007806:Language Disorders / Q000209:etiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D010100:Oxygen / Q000097:blood; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000150:complications* / Q000473:pathology*
chemical_list: D010100:Oxygen
keywords: Diffusion tensor imaging (DTI); Functional left-lateralization; Interhemispheric connectivity; Language; Schizophrenia; Tractography