Direct demonstration of transcallosal disinhibition in language networks.
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.
Thiel
Alexander
A
Department of Neurology, University of Cologne, Köln, Germany. A.Thiel@pet.mpin-koeln.mpg.de
Schumacher
Birgit
B
Wienhard
Klaus
K
Gairing
Stefanie
S
Kracht
Lutz W
LW
Wagner
Rainer
R
Haupt
Walter F
WF
Heiss
Wolf-Dieter
WD
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
D010104:Oxygen Radioisotopes