title: Direct demonstration of transcallosal disinhibition in language networks.
abstract: Neuroimaging studies in right-handed patients with left hemisphere brain lesions have demonstrated a shift of language activity from left to right inferior frontal gyrus (IFG). This shift may be caused by greater right hemisphere dominance before the injury or by reduced inhibitory activity of the injured left hemisphere. We simulated a brain lesion applying transcranial -magnetic stimulation over left IFG in normal subjects, while simultaneously measuring language activity with positron -emission tomography. Interference with transcranial -magnetic stimulation decreased activity in left and increased it in right IFG in all subjects. We thus demonstrate for the first time that a rightward shift of language activity is caused by the brain lesion and not by greater right-hemisphere dominance, thus supporting the hypothesis of reduced transcallosal inhibition.
authors.affiliation: Department of Neurology, University of Cologne, Köln, Germany. A.Thiel@pet.mpin-koeln.mpg.de
authors.forename: Alexander
authors.initials: A
authors.lastname: Thiel
authors.forename: Birgit
authors.initials: B
authors.lastname: Schumacher
authors.forename: Klaus
authors.initials: K
authors.lastname: Wienhard
authors.forename: Stefanie
authors.initials: S
authors.lastname: Gairing
authors.forename: Lutz W
authors.initials: LW
authors.lastname: Kracht
authors.forename: Rainer
authors.initials: R
authors.lastname: Wagner
authors.forename: Walter F
authors.initials: WF
authors.lastname: Haupt
authors.forename: Wolf-Dieter
authors.initials: WD
authors.lastname: Heiss
mesh_terms: D000328:Adult; D003337:Corpus Callosum / Q000000981:diagnostic imaging / Q000502:physiology*; D005625:Frontal Lobe / Q000000981:diagnostic imaging / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007802:Language; D008297:Male; D009415:Nerve Net / Q000000981:diagnostic imaging / Q000502:physiology*; D010104:Oxygen Radioisotopes; D049268:Positron-Emission Tomography; D011578:Psycholinguistics; D050781:Transcranial Magnetic Stimulation
chemical_list: D010104:Oxygen Radioisotopes