• Mervi Könönen, Niko Tamsi, Laura Säisänen, Samuli Kemppainen, Sara Määttä, Petro Julkunen, Leena Jutila, Marja Äikiä, Reetta Kälviäinen, Eini Niskanen, Ritva Vanninen, Pasi Karjalainen, and Esa Mervaala.
• Department of Clinical Neurophysiology, Kuopio University Hospital, PO Box 100, 70029 Kuopio, Finland; Department of Radiology, Kuopio University Hospital, PO Box 100, 70029 Kuopio, Finland. Electronic address: mervi.kononen@kuh.fi.
• J. Neurosci. Methods. 2015 Jun 15;248:32-40.

BackgroundNavigated transcranial magnetic stimulation (nTMS) is a modern precise method to activate and study cortical functions noninvasively. We hypothesized that a combination of nTMS and functional magnetic resonance imaging (fMRI) could clarify the localization of functional areas involved with motor control and production of speech.New MethodNavigated repetitive TMS (rTMS) with short bursts was used to map speech areas on both hemispheres by inducing speech disruption during number recitation tasks in healthy volunteers. Two experienced video reviewers, blinded to the stimulated area, graded each trial offline according to possible speech disruption. The locations of speech disrupting nTMS trials were overlaid with fMRI activations of word generation task.ResultsComparison With Existing MethodsSpeech disruptions were produced on both hemispheres by nTMS, though there were more disruptive stimulation sites on the left hemisphere. Grade of the disruptions varied from subjective sensation to mild objectively recognizable disruption up to total speech arrest. The distribution of locations in which speech disruptions could be elicited varied among individuals. On the left hemisphere the locations of disturbing rTMS bursts with reviewers' verification followed the areas of fMRI activation. Similar pattern was not observed on the right hemisphere.ConclusionsThe reviewer-verified speech disruptions induced by nTMS provided clinically relevant information, and fMRI might explain further the function of the cortical area. nTMS and fMRI complement each other, and their combination should be advocated when assessing individual localization of speech network.Copyright © 2015 Elsevier B.V. All rights reserved.

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