title: Global-local interference is related to callosal compromise in alcoholism: a behavior-DTI association study.
abstract: BACKGROUND
  Visuospatial ability is a multifactorial process commonly impaired in chronic alcoholism. Identification of which features of visuospatial processing are affected and which are spared in alcoholism, however, has not been clearly determined. We used a global-local paradigm to assess component processes of visuospatial ability and MR diffusion tensor imaging (DTI) to examine whether alcoholism-related microstructural degradation of the corpus callosum contributes to disruption of selective lateralized visuospatial and attention processes.
  
  
  METHODS
  A hierarchical letter paradigm was devised, where large global letters were composed of small local letters. The task required identification of target letters among distractors presented at global, local, both, or neither level. Attention was either selectively directed to global or local levels or divided between levels. Participants were 18 detoxified chronic alcoholics and 22 age-matched healthy controls. DTI provided quantitative assessment of the integrity of corpus callosal white matter microstructure.
  
  
  RESULTS
  Alcoholics generally had longer reaction times than controls but obtained similar accuracy scores. Both groups processed local targets faster than global targets and showed interference from targets at the unattended level. Alcoholics exhibited moderate compromise in selectively attending to the global level when the global stimuli were composed of local targets. Such local interference was less with longer abstinence. Callosal microstructural integrity compromise predicted degree of interference from stimulus incongruency in the alcoholic group. This relationship was not observed for lateral or third ventricular volumes, which are measures of nonspecific cortical volume deficits.
  
  
  CONCLUSIONS
  Global-local feature perception was generally spared in abstinent chronic alcoholics, but impairments were observed when directing attention to global features and when global and local information interfered at stimulus or response levels. Furthermore, the interference-callosal integrity relationship in alcoholics indicates that compromised visuospatial functions include those requiring bilateral integration of information.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, California 94305-5723, USA.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Müller-Oehring
authors.forename: Tilman
authors.initials: T
authors.lastname: Schulte
authors.forename: Rosemary
authors.initials: R
authors.lastname: Fama
authors.forename: Adolf
authors.initials: A
authors.lastname: Pfefferbaum
authors.forename: Edith V
authors.initials: EV
authors.lastname: Sullivan
mesh_terms: D000328:Adult; D000428:Alcohol Drinking; D000437:Alcoholism / Q000473:pathology / Q000503:physiopathology*; D001288:Attention; D016022:Case-Control Studies; D003337:Corpus Callosum / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014796:Visual Perception