title: Correlation of brain white matter diffusion anisotropy and mean diffusivity with reaction time in an oddball task.
abstract: BACKGROUND
  Reaction time (RT) is a frequently used measure of information processing speed, but the underlying physiological and anatomical conditions are not yet fully understood. A correlation between measures of white matter (WM) ultrastructural properties and RT is expected--particularly for those WM tracts that are involved in the attentional system of the brain.
  
  
  METHODS
  Diffusion tensor imaging data were acquired in 43 unrelated healthy subjects (age: 22.7 +/- 1.8 years), and RT was measured during an attention-requiring visual oddball task in the same scanning session. Voxel-by-voxel and region of interest analyses were performed for the large association tracts. A linear regression model was used to correlate fractional anisotropy (FA) and mean diffusivity (MD) values with mean RT.
  
  
  RESULTS
  Our analyses revealed significant positive correlations between RT and MD in several WM association tracts, predominantly in the right hemisphere. To a lesser extent, significant negative correlations were found between RT and FA in right temporal WM.
  
  
  CONCLUSIONS
  These findings suggest that subcortical ultrastructural properties of the dorsal and ventral visual stream are relevant with regard to information processing speed. Furthermore, MD appears to be more sensitive than FA in detecting functionally relevant ultrastructural variations in WM tracts.
authors.affiliation: Department of Psychiatry and Psychotherapy, University Medical Center of the Johannes Gutenberg University, Mainz, Germany. andreas_konrad@gmx.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Konrad
authors.forename: Goran
authors.initials: G
authors.lastname: Vucurevic
authors.forename: Francesco
authors.initials: F
authors.lastname: Musso
authors.forename: Peter
authors.initials: P
authors.lastname: Stoeter
authors.forename: Georg
authors.initials: G
authors.lastname: Winterer
mesh_terms: D016880:Anisotropy; D001921:Brain / Q000033:anatomy & histology*; D003071:Cognition; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D009413:Nerve Fibers, Myelinated; D009483:Neuropsychological Tests; D011930:Reaction Time; D012727:Sex Characteristics; D044465:White People; D055815:Young Adult