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Influence of transitivity on nTMS language mapping: Insights from healthy individuals and people with gliomas
Poster B11 in Poster Session B, Tuesday, October 24, 3:30 - 5:15 pm CEST, Espace Vieux-Port
Effrosyni Ntemou1,2,3, Roel Jonkers1, Frank Burchert2, Klara Reisch3, Thomas Picht3, Adrià Rofes1; 1University of Groningen, 2University of Potsdam, 3Charité – Universitätsmedizin Berlin
Introduction Navigated Transcranial Magnetic stimulation (nTMS) has been used to causally identify cortical regions involved in language processing within the clinical setting of preoperative language mapping as well as for research purposes with healthy individuals. nTMS has previously indicated that the production of nouns vs verbs engages different cortical regions. However, to this date the influence of linguistic characteristics of the same semantic category on nTMS mapping results has not yet been examined. For example, although the verb variable of argument structure has been investigated with functional Magnetic Resonance Imaging (fMRI), similar investigations are scarce within TMS research. According to fMRI data, bilateral cortical areas connected by the arcuate fasciculus (AF) have been implicated in the processing of transitive compared to unergative verbs. The present study examines the influence of transitivity on the outcomes of clinical and non-clinical language mapping with nTMS. Methods To test this connection between transitivity and bilateral perisylvian regions, we administered a tractography-guided online inhibitory nTMS protocol during picture naming of finite transitive verbs (The man reads) and unergative verbs (The man sails). After tracking the left and right AF, we stimulated the cortical terminations of the tract in frontal, parietal and temporal regions in 20 neurologically healthy native speakers of German. Additionally, we performed the same task and tractography-based nTMS protocol within the preoperative setting of 22 individuals with left hemisphere gliomas. Results Our data revealed that nTMS induced more errors during naming of finite transitive verbs compared to unergative verbs when stimulating the left (vs right) AF terminations in healthy individuals. This effect was specific to the left temporal terminations of the AF, whereas no differences between the two verb types were identified when stimulating inferior parietal and frontal AF terminations. Induced errors for transitive verbs over left temporal terminations mostly manifested as access errors (i.e., anomias, hesitations). Comparable results were obtained from the group of people with gliomas. However, an exploratory analysis suggested that the nTMS-induced effect over left temporal terminations of the AF was absent when gliomas displaced or infiltrated AF terminations. Conclusion The nTMS data from healthy individuals indicate that only posterior temporal regions result in more errors during naming of verbs with more arguments (i.e., transitive vs unergative verbs). The nTMS data from patients indicate that more language-positive sites are identified when patients produce transitive vs unergative verbs. From a neurolinguistic perspective, these results stress the role of left temporoparietal areas in language processing, with a particular emphasis on argument structure processing. From a clinical perspective, we highlight that different verb stimuli can influence the sensitivity of pre-operative nTMS language mappings.
Topic Areas: Language Production, Syntax and Combinatorial Semantics