In preoperative planning, fMRI and repetitive navigated transcranial magnetic stimulation (rTMS) repeatedly revealed differences in the detected language sites, which can be attributed to tumor-induced oxygenation changes impairing the accuracy of fMRI. We therefore compared the accordance of those techniques in healthy subjects using exactly the same tasks in both investigations. 19 healthy right-handed subjects performed object naming, pseudoword reading, verb generation, and action naming during fMRI at 3 T and rTMS. For rTMS language mapping, we stimulated 46 cortical spots over the left hemisphere; each site was stimulated for three times. Language positive points during rTMS for one, two, or three errors out the three stimulations per spot (1/3, 2/3, 3/3) were exported via DICOM, and compared to the positive fMRI clusters. As a result of this comparison, the best correlation was observed between 3/3 errors and fMRI for pseudoword reading and verb generation with t-values of pu < 0.001, uncorrected for multiple comparisons, on average across the whole rTMS-spot map. We found a close spatial agreement between several rTMS-spots (2/3 and 3/3 errors) and fMRI clusters accentuated in the frontal lobe, followed by the parietal lobe and less in the temporal lobe. Compared to the fMRI clusters, there was a higher congruence for 2/3 and 3/3 errors than for 1/3 errors. Overall, results of language mapping in healthy subjects by fMRI and rTMS correspond well yet depending on the used language task.
Keywords: Action naming; Functional MRI; Object naming; Pseudoword reading; Transcranial magnetic stimulation.