title: Language function distribution in left-handers: A navigated transcranial magnetic stimulation study.
abstract: Recent studies suggest that in left-handers, the right hemisphere (RH) is more involved in language function when compared to right-handed subjects. Since data on lesion-based approaches is lacking, we aimed to investigate language distribution of left-handers by repetitive navigated transcranial magnetic stimulation (rTMS). Thus, rTMS was applied to the left hemisphere (LH) and RH in 15 healthy left-handers during an object-naming task, and resulting naming errors were categorized. Then, we calculated error rates (ERs=number of errors per number of stimulations) for both hemispheres separately and defined a laterality score as the quotient of the LH ER - RH ER through the LH ER + RH ER (abbreviated as (L-R)/(L+R)). In this context, (L-R)/(L+R)>0 indicates that the LH is dominant, whereas (L-R)/(L+R)<0 shows that the RH is dominant. No significant difference in ERs was found between hemispheres (all errors: mean LH 18.0±11.7%, mean RH 18.1±12.2%, p=0.94; all errors without hesitation: mean LH 12.4±9.8%, mean RH 12.9±10.0%, p=0.65; no responses: mean LH 9.3±9.2%, mean RH 11.5±10.3%, p=0.84). However, a significant difference between the results of (L-R)/(L+R) of left-handers and right-handers (source data of another study) for all errors (mean 0.01±0.14 vs. 0.19±0.20, p=0.0019) and all errors without hesitation (mean -0.02±0.20 vs. 0.19±0.28, p=0.0051) was revealed, whereas the comparison for no responses did not show a significant difference (mean: -0.004±0.27 vs. 0.09±0.44, p=0.64). Accordingly, left-handers present a comparatively equal language distribution across both hemispheres with language dominance being nearly equally distributed between hemispheres in contrast to right-handers.
authors.affiliation: Department of Neurosurgery, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675 Munich, Germany. Electronic address: Tussislorena@gmail.com.
authors.forename: Lorena
authors.initials: L
authors.lastname: Tussis
authors.affiliation: Department of Neurosurgery, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675 Munich, Germany; TUM-Neuroimaging Center, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675 Munich, Germany. Electronic address: Nico.Sollmann@tum.de.
authors.forename: Nico
authors.initials: N
authors.lastname: Sollmann
authors.affiliation: Section of Neuroradiology, Department of Radiology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675 Munich, Germany. Electronic address: Boeckh-behrens@tum.de.
authors.forename: Tobias
authors.initials: T
authors.lastname: Boeckh-Behrens
authors.affiliation: Department of Neurosurgery, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675 Munich, Germany. Electronic address: Bernhard.Meyer@tum.de.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Meyer
authors.affiliation: Department of Neurosurgery, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675 Munich, Germany; TUM-Neuroimaging Center, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675 Munich, Germany. Electronic address: Sandro.Krieg@tum.de.
authors.forename: Sandro M
authors.initials: SM
authors.lastname: Krieg
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008037:Linguistics; D008297:Male; D038361:Neuronavigation; D010364:Pattern Recognition, Visual / Q000502:physiology; D011597:Psychomotor Performance; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: Cortical mapping; Language; Left-handedness; Navigated brain stimulation; Object naming; Transcranial magnetic stimulation