title: Dynamics of hemispheric dominance for language assessed by magnetoencephalographic imaging.
abstract: OBJECTIVE
  The goal of the current study was to examine the dynamics of language lateralization using magnetoencephalographic (MEG) imaging, to determine the sensitivity and specificity of MEG imaging, and to determine whether MEG imaging can become a viable alternative to the intracarotid amobarbital procedure (IAP), the current gold standard for preoperative language lateralization in neurosurgical candidates.
  
  
  METHODS
  MEG was recorded during an auditory verb generation task and imaging analysis of oscillatory activity was initially performed in 21 subjects with epilepsy, brain tumor, or arteriovenous malformation who had undergone IAP and MEG. Time windows and brain regions of interest that best discriminated between IAP-determined left or right dominance for language were identified. Parameters derived in the retrospective analysis were applied to a prospective cohort of 14 patients and healthy controls.
  
  
  RESULTS
  Power decreases in the beta frequency band were consistently observed following auditory stimulation in inferior frontal, superior temporal, and parietal cortices; similar power decreases were also seen in inferior frontal cortex prior to and during overt verb generation. Language lateralization was clearly observed to be a dynamic process that is bilateral for several hundred milliseconds during periods of auditory perception and overt speech production. Correlation with the IAP was seen in 13 of 14 (93%) prospective patients, with the test demonstrating a sensitivity of 100% and specificity of 92%.
  
  
  CONCLUSIONS
  Our results demonstrate excellent correlation between MEG imaging findings and the IAP for language lateralization, and provide new insights into the spatiotemporal dynamics of cortical speech processing.
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California at San Francisco, USA.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Findlay
authors.forename: Josiah B
authors.initials: JB
authors.lastname: Ambrose
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Cahn-Weiner
authors.forename: John F
authors.initials: JF
authors.lastname: Houde
authors.forename: Susanne
authors.initials: S
authors.lastname: Honma
authors.forename: Leighton B N
authors.initials: LB
authors.lastname: Hinkley
authors.forename: Mitchel S
authors.initials: MS
authors.lastname: Berger
authors.forename: Srikantan S
authors.initials: SS
authors.lastname: Nagarajan
authors.forename: Heidi E
authors.initials: HE
authors.lastname: Kirsch
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D001932:Brain Neoplasms / Q000601:surgery; D004292:Dominance, Cerebral / Q000502:physiology*; D004827:Epilepsy / Q000601:surgery; D005260:Female; D006801:Humans; D007802:Language; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D059906:Neuroimaging / Q000379:methods*; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult