title: Method for quantitatively evaluating the lateralization of linguistic function using functional MR imaging.
abstract: OBJECTIVE
  Various methods for evaluating the lateralization of linguistic function using functional MR imaging have been proposed. However, the optimal method remains controversial. The purpose of this study was not only to establish a method for quantitatively evaluating the lateralization of linguistic function but also to evaluate its optimality.
  
  
  METHODS
  Internal speech tasks were measured by functional MR imaging in 17 healthy adult volunteers by use of z scores. The laterality index (LI) was calculated first by a previously reported method and second by our newly designed method, in which we investigated the correlation between the z scores and the number of activated pixels in the regions of interest; that is, we made scatter diagrams (z scores versus number of activated pixels). To obtain detailed information, we searched a regression function that fit the scatter diagrams well.
  
  
  RESULTS
  We found the number of activated pixels was proportional to (1/z score)(4) and the correlation coefficient was very high. Each hemisphere showed an original proportional constant. Our newly designed LI was calculated from these two constants and was found to be a fixed value. In contrast, the reported LI varied with the z score. We found our LI differed in robustness and reproducibility from the reported LI.
  
  
  CONCLUSIONS
  Our LI method proved more optimal than the reported LI. The lateralization of linguistic function can be evaluated quantitatively using our new LI method.
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima City, Japan, 890-8520.
authors.forename: S I
authors.initials: SI
authors.lastname: Nagata
authors.forename: K
authors.initials: K
authors.lastname: Uchimura
authors.forename: W
authors.initials: W
authors.lastname: Hirakawa
authors.forename: J I
authors.initials: JI
authors.lastname: Kuratsu
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D004292:Dominance, Cerebral; D005260:Female; D006801:Humans; D007802:Language; D008279:Magnetic Resonance Imaging; D008297:Male; D008959:Models, Neurological; D012016:Reference Values