Article
Influence of word characteristics on the rate of semantic language errors induced by repetitive navigated transcranial magnetic stimulation
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Authors
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Catharina Schröter
- Klinikum der Universität zu Köln, Zentrum für Neurochirurgie, Klinik für Allgemeine Neurochirurgie, Köln, Deutschland
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Julia Pieczewski
- Klinikum der Universität zu Köln, Zentrum für Neurochirurgie, Klinik für Allgemeine Neurochirurgie, Köln, Deutschland
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Charlotte Nettekoven
- Klinikum der Universität zu Köln, Zentrum für Neurochirurgie, Klinik für Allgemeine Neurochirurgie, Köln, Deutschland
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Kristina Thiele
- University of Cologne, Faculty of Human Sciences, Department of Special Education and Rehabilitation, Köln, Deutschland
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Roland Goldbrunner
- Klinikum der Universität zu Köln, Zentrum für Neurochirurgie, Klinik für Allgemeine Neurochirurgie, Köln, Deutschland
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Carolin Weiß Lucas
- Klinikum der Universität zu Köln, Zentrum für Neurochirurgie, Klinik für Allgemeine Neurochirurgie, Köln, Deutschland
| Published: | June 9, 2017 |
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Outline
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Objective: Repetitive transcranial magnetic stimulation (rTMS) to map cortical language functions by inducing “virtual lesions” during task performance (e.g., picture-naming) has recently been introduced into pre-surgical diagnostics in brain tumor patients. We investigated to which extent the characteristics of the objects (words) used in the task influence the occurrence of semantically related language errors.
Methods: Thirteen right-handed, healthy volunteers (female n=6/male n=7) were investigated in 3 consecutive sessions by 10Hz, 30Hz and 50Hz-rTMS. After determination of the individual threshold reflecting motor cortex excitability, online-rTMS was applied during a picture-naming task: black-and-white drawings (n=50) of everyday objects were presented simultaneously with rTMS. Errors were rated by two independent examiners using post-hoc video analysis. The frequency (number of errors per 100 rTMS pulses) of errors related to semantic processing (i.e., anomia and semantic paraphasia) was quantified. Error strength (as defined by no or not identifiable word response) was assessed. All objects allowing alternative naming responses (e.g., ball / football) were excluded. The remaing words were grouped by the number of sillables in one- (1S; N=19) and two-sillable words (2S; N=25). For each object, the word frequency was assessed and correlated to the error rates by Pearson's product moment correlation. Error rates were compared between 1S and 2S using McNemar's test for paired count data.
Results: The number of sillables (1S vs. 2S) had no influence on the total error rate (1S: mean N=73.9 errors/word vs. 2S: mean N=79.9) or the error strength (1S: mean N=19.5 vs. 2S: mean N=19.5). By contrast, the rate of anomias (1S: mean N=4.2 vs. 2S: mean N=6.4) increased with the number of sillables (p<0.01), regardless of the word frequency in German language (n.s.). For semantic paraphasias, a weak statistical tendency was observed (p=0.11), presumably due to few events (1S: mean N=1.4 vs. 2S: mean N=2.2).
Conclusion: Disruption of semantic word processing / word expression, induced by rTMS, seems to be significantly influenced by the complexity of the tested words, i.e., the number of sillables. Using longer words for language mapping might be favourable in order to increase the true-positive rate of mapping results.
