title: Microstructural abnormalities in anterior callosal fibers and their relationship with cognitive function in major depressive disorder and bipolar disorder: a tract-specific analysis study.
abstract: BACKGROUND
  The corpus callosum modulates interhemispheric communication and cognitive processes. It has been suggested that white matter abnormalities in the corpus callosum are related to the pathophysiology of major depressive disorder (MDD) and bipolar disorder (BD). The aim of this study was to examine microstructural abnormalities in callosal fibers separated by their connection to functional brain regions and determine the relationship of these abnormalities with cognitive function in MDD and BD.
  
  
  METHODS
  The subjects were 18 patients with MDD, 20 patients with BD, and 21 healthy controls. The callosal fibers were divided into 6 segments based on their cortical projection using tract-specific analysis of diffusion tensor imaging. We examined differences in the fractional anisotropy (FA) of callosal fibers in six segments among the three subject groups and examined the correlation between the FA in each segment and cognitive performance in the 3 groups.
  
  
  RESULTS
  The FA of anterior callosal fibers were reduced significantly in the MDD and BD groups compared to those in the HC group, and the FA of anterior callosal fibers correlated significantly with the raw scores of the digit sequencing task and symbol coding in the MDD group.
  
  
  CONCLUSIONS
  The patients were medicated at the time of scanning, and the MDD and BD groups were not matched for symptom severity.
  
  
  CONCLUSIONS
  Our results suggest that MDD and BD have similar microstructural abnormalities in anterior callosal fibers connecting bilateral frontal cortices, and these abnormalities may be related to impairment of working memory and attention in MDD.
authors.affiliation: Department of Neuropsychiatry, Wakayama Medical University, Wakayama, Japan. Electronic address: shinyama@wakayama-med.ac.jp.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Yamada
authors.affiliation: Department of Neuropsychiatry, Wakayama Medical University, Wakayama, Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Takahashi
authors.affiliation: Department of Neuropsychiatry, Wakayama Medical University, Wakayama, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ukai
authors.affiliation: Department of Neuropsychiatry, Wakayama Medical University, Wakayama, Japan.
authors.forename: Tomikimi
authors.initials: T
authors.lastname: Tsuji
authors.affiliation: Department of Neuropsychiatry, Wakayama Medical University, Wakayama, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Iwatani
authors.affiliation: Department of Neuropsychiatry, Wakayama Medical University, Wakayama, Japan.
authors.forename: Kumi
authors.initials: K
authors.lastname: Tsuda
authors.affiliation: Department of Neuropsychiatry, Wakayama Medical University, Wakayama, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Kita
authors.affiliation: Department of Neuropsychiatry, Wakayama Medical University, Wakayama, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Sakamoto
authors.affiliation: Department of Neuropsychiatry, Wakayama Medical University, Wakayama, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamamoto
authors.affiliation: Wakayama-Minami Radiology Clinic, Wakayama, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Terada
authors.affiliation: Department of Neuropsychiatry, Wakayama Medical University, Wakayama, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Shinosaki
mesh_terms: D000328:Adult; D016880:Anisotropy; D001714:Bipolar Disorder / Q000150:complications / Q000473:pathology*; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000150:complications / Q000473:pathology*; D003337:Corpus Callosum / Q000473:pathology*; D003865:Major Depressive Disorder / Q000150:complications / Q000473:pathology*; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D059906:Neuroimaging; D009483:Neuropsychological Tests; D066127:White Matter / Q000473:pathology*; D055815:Young Adult
keywords: Bipolar disorder; Corpus callosum; Diffusion tensor imaging; Major depressive disorder; Tract-specific analysis; White matter pathophysiology