Neuroimaging-guided rTMS of the left inferior frontal gyrus interferes with repetition priming.
Neuroimaging studies of right-handed normal volunteers under semantic word generation tasks have consistently reported left lateralized activation of the anterior inferior frontal gyrus (ifg) which decreased during task repetition. This repetition-related activation decrease has been interpreted as the neurophysiological correlate of repetition priming, a mechanism of implicit memory for initial semantic processing. We interfered with left lateralized ifg activation, as identified by O-15-water PET activation, using repetitive transcranial magnetic stimulation (rTMS) in five right-handed male normal subjects, once using new (unprimed) nouns and once using known (primed) nouns for the procedure. All five subjects exhibited clear left lateralized activations of the triangular part of the left ifg in the PET studies. In all subjects, reaction time latencies were significantly longer during rTMS over the activation sites in the left ifg as compared to latencies off stimulation. Latencies were not affected during stimulation of the right ifg or over the vertex. These effects were observed within the group and in each individual, only if lists of primed nouns were used in the verb-generation task. In conclusion, these results demonstrate that the anterior part of the left ifg is not only involved in semantic processing, but is also essential for repetition priming on semantic tasks since successful interference with rTMS was only observed if lists of primed words were used for the generation task.
Thiel
Alexander
A
Department of Neurology, University of Cologne, Germany. A.Thiel@pet.mpin-koeln.mpg.de
Haupt
Walter F
WF
Habedank
Birgit
B
Winhuisen
Lutz
L
Herholz
Karl
K
Kessler
Josef
J
Markowitsch
Hans-Joachim
HJ
Heiss
Wolf-Dieter
WD
D000328:Adult; D001288:Attention / Q000502:physiology*; D001931:Brain Mapping; D004292:Dominance, Cerebral / Q000502:physiology*; D004574:Electromagnetic Fields; D005625:Frontal Lobe / Q000000981:diagnostic imaging*; D006185:Habituation, Psychophysiologic / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term; D008875:Middle Aged; D009415:Nerve Net / Q000502:physiology; D010153:Paired-Associate Learning / Q000502:physiology*; D049268:Positron-Emission Tomography; D011930:Reaction Time; D012660:Semantics