Task Type Affects Location of Language-Positive Cortical Regions by Repetitive Navigated Transcranial Magnetic Stimulation Mapping

Abstract

ObjectivesRecent repetitive TMS (rTMS) mapping protocols for language mapping revealed deficits of this method, mainly in posterior brain regions. Therefore this study analyzed the impact of different language tasks on the localization of language-positive brain regions and compared their effectiveness, especially with regard to posterior brain regions.MethodsNineteen healthy, right-handed subjects performed object naming, pseudoword reading, verb generation, and action naming during rTMS language mapping of the left hemisphere. Synchronically, 5 Hz/10 pulses were applied with a 0 ms delayResultsThe object naming task evoked the highest error rate (14%), followed by verb generation (13%) and action naming (11%). The latter revealed more errors in posterior than in anterior areas. Pseudoword reading barely generated errors, except for phonological paraphasias.ConclusionsIn general, among the evaluated language tasks, object naming is the most discriminative task to detect language-positive regions via rTMS. However, other tasks might be used for more specific questions.

Results on the spatial resolution of repetitive transcranial magnetic stimulation for cortical language mapping during object naming in healthy subjects

“…Mappings were successfully performed in 19 healthy, right-handed volunteers, which were already analyzed for different purposes in previous investigations [11, 12]. Table 2 gives an overview of subject-related characteristics and mapping parameters.…”

“…All mapping sessions were originally performed in 19 healthy, right-handed (as indicated by the Edinburgh Handedness Inventory = EHI) subjects in 2013 to investigate different research questions of rTMS-based language mapping [11, 12]. The enrolled volunteers were German native speakers without general transcranial magnetic stimulation (TMS) exclusion criteria (e.g., metal implants).…”

“…During baseline testing and rTMS-based language mapping, volunteers participated in an object-naming task, which has been frequently used in previous rTMS investigations [2, 6–8, 10–12]. The task consisted of a total amount of 100 colored photographs, similar to the objects of the Snodgrass and Vanderwart picture set (1980) [11–13].…”

“…Overall, 46 left-hemispheric cortical spots, which were manually tagged on the 3-D MRI scan of the volunteer prior to mapping, were stimulated three times each in a row without any particular order (Fig. 1), as reported previously [11, 12]. Thus, mapping was carried out over predefined spots.

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“…For each mapping session, the following stimulation parameters were chosen, as they (a) have shown to be efficient in terms of eliciting reproducible naming errors during object naming, and (b) have been proven to be well tolerable and safe for the individual subject [1, 2, 6–8, 10–12]:Stimulation intensity: 100% of the RMTStimulation frequency: 7 HzNumber of pulses: 10Duration of each stimulation burst (7 Hz/10 pulses): 1430 msPicture-to-trigger interval (=PTI, time between the presentation of an object on the screen and the beginning of the rTMS pulse): 0 msDisplay time (=DT, duration of the screening of an object): 700 msInter-picture interval (=IPI, time between the screening of two objects): 3000 ms …”