title: Disease severity is correlated to tract specific changes of fractional anisotropy in MD and CM thalamus--a DTI study in major depressive disorder.
abstract: BACKGROUND
  Depression is commonly conceptualized as corticolimbic dysregulation. Due to insufficient studies in normal aged populations especially subcortical sources of disconnection are unclear in contrast to potentially general parietal white matter (WM) deficits. This may be due to important influences of variable patient characteristics, most importantly episode severity. Especially thalamic disconnections have been functionally revealed, however, their structural correlates have not been distinctly investigated for its highly diverse subnuclei.
  
  
  METHODS
  We compared 20 major depressive disorder (MDD) patients with mixed Hamilton depression rating scale (HAMD) severity to matched controls in fractional anisotropy (FA) derived from diffusion tensor imaging (DTI). Robust acquisition of 4 repetitions restricted to twelve directions, also to match the same parameters used by Eckert et al. (2011) who described a preferential architecture of centromedian (CM) and mediodorsal (MD) thalamic connections. Second to whole brain analysis, we tested for group differences within the preferred structural network of these two nuclei using a tract of interest (TOI) approach.
  
  
  RESULTS
  Significant FA deficits in a whole brain analysis were only found in right parietal WM (p<0.05, corrected). Effects of severity were found for increasing thalamic FA. Post hoc analysis revealed this effect to be restricted to CM specific tracts. In contrast, we found MD to dorsolateral prefrontal cortex (DLPFC) tracts to be decreased in FA. Unspecific decreases between MD and CM towards amygdala were paralleled by primary amygdala FA reductions.
  
  
  CONCLUSIONS
  Specificity of the TOI approach and heterogenous sample.
  
  
  CONCLUSIONS
  Robust parietal FA reductions, controlled for age effects were found in MDD. Further we revealed subcortical disease state dependency of FA in thalamic tracts, specific to predescribed preferential connections.
authors.affiliation: Department of Psychiatry, Otto-von-Guericke University, Magdeburg, Germany. anne@canlab.de
authors.forename: Annemarie
authors.initials: A
authors.lastname: Osoba
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hänggi
authors.forename: Meng
authors.initials: M
authors.lastname: Li
authors.forename: Dorothea I
authors.initials: DI
authors.lastname: Horn
authors.forename: Coraline
authors.initials: C
authors.lastname: Metzger
authors.forename: Ulf
authors.initials: U
authors.lastname: Eckert
authors.forename: Jörn
authors.initials: J
authors.lastname: Kaufmann
authors.forename: Kathrin
authors.initials: K
authors.lastname: Zierhut
authors.forename: Johann
authors.initials: J
authors.lastname: Steiner
authors.forename: Kolja
authors.initials: K
authors.lastname: Schiltz
authors.forename: Hans-Jochen
authors.initials: HJ
authors.lastname: Heinze
authors.forename: Bernhard
authors.initials: B
authors.lastname: Bogerts
authors.forename: Martin
authors.initials: M
authors.lastname: Walter
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016880:Anisotropy; D001921:Brain / Q000473:pathology; D003865:Major Depressive Disorder / Q000473:pathology*; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013788:Thalamus / Q000473:pathology*; D055815:Young Adult