title: Effects of covert and overt paradigms in clinical language fMRI.
abstract: OBJECTIVE
  The aim of this study was to assess the intrasubject and intersubject reproducibility of functional magnetic resonance imaging (fMRI) language paradigms on language localization and lateralization.
  
  
  METHODS
  Fourteen healthy volunteers were enrolled prospectively and underwent language fMRI using visually triggered covert and overt sentence generation (SG) and word generation (WG) paradigms. Semiautomated analysis of all functional data was performed using Brain Voyager on an individual basis. Regions of interest for Broca's area, Wernicke's area, and their contralateral homologues were drawn. The Euclidean coordinates of the center of gravidity (x, y, and z) of the respective blood oxygenation level-dependent (BOLD) activation cluster, and the correlation of the measured hemodynamic response to the applied reference function (r), relative BOLD signal change as BOLD signal characteristics were measured in each region of interest. Regional lateralization indexes were calculated for Broca's area, Wernicke's area, and their contralateral homologues separately. Wilcoxon's signed-rank test was applied for statistical comparisons (P values < .05 were considered significant). Ten of the 14 volunteers had three repeated measurements to test intrasession reproducibility and intersession reproducibility.
  
  
  RESULTS
  Overall activation rates for the four paradigms were 89% for covert SG, 82% for overt SG, 89% for covert WG, and 100% for overt WG. When comparing covert and overt paradigms, language localization was significantly different in 17% (Euclidean coordinates) and 19% (BOLD signal characteristics), respectively. Language lateralization was significantly different in 75%. Intrasubject and intersubject reproducibility was excellent, with 3.3% significant differences among all five parameters for language localization and 0% significant differences for language lateralization using covert paradigms.
  
  
  CONCLUSIONS
  Covert language paradigms (SG and WG) provided highly robust and reproducible localization and lateralization of essential language centers for scans performed on the same and different days. Their overt counterparts achieved confirmatory localization but lower lateralization capabilities. Reference data for presurgical application are provided.
authors.affiliation: Department of Neuroradiology, University Hospital Basel, Petersgraben 4, 4031 Basel, Switzerland. sasanp@gmx.de
authors.forename: Sasan
authors.initials: S
authors.lastname: Partovi
authors.forename: Florian
authors.initials: F
authors.lastname: Konrad
authors.forename: Sasan
authors.initials: S
authors.lastname: Karimi
authors.forename: Fabian
authors.initials: F
authors.lastname: Rengier
authors.forename: John K
authors.initials: JK
authors.lastname: Lyo
authors.forename: Lisa
authors.initials: L
authors.lastname: Zipp
authors.forename: Ernst
authors.initials: E
authors.lastname: Nennig
authors.forename: Christoph
authors.initials: C
authors.lastname: Stippich
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology*; D059907:Functional Neuroimaging / Q000379:methods*; D006801:Humans; D007802:Language; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult