Artikel
Language function distribution in left-handers: a navigated transcranial magnetic stimulation study
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Veröffentlicht: | 8. Juni 2016 |
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Objective: Recent studies suggest that in left-handers, the right hemisphere (RH) is more involved in language function when compared to right-handers. Since data on lesion-based approaches is lacking, we aimed to investigate language distribution of left-handers by repetitive navigated transcranial magnetic stimulation (rTMS).
Method: rTMS was applied to both hemispheres in fifteen healthy left-handers during an object-naming task, and resulting naming errors were categorized. Then we calculated error rates (ER = number of errors per number of stimulations) and defined the hemispheric dominance ratio (HDR) as the quotient of the left- through the right-sided ER (HDR > 1 = left dominant; HDR < 1 = right dominant).
Results: No significant difference in ERs was found between the RH and left hemisphere (LH) (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=0.67; no responses: mean LH 9.3 ± 9.3%, mean RH 11.5 ± 10.2%, p=0.91). However, left-handers present a lower HDR compared to right-handers (source data of another study) for all errors and all errors without hesitation (all errors: mean 1.1 ± 0.3 vs. 1.8 ± 0.8, p=0.0001; all errors without hesitation: mean 1.0 ± 0.4 vs. 1.8 ± 1.0, p=0.0008), but not for no-response errors (mean: 1.1 ± 0.9 vs. 1.5 ± 1.5, p= 0.78).
Conclusions: According to our rTMS approach, left-handers present a comparatively homogeneous language distribution across the LH and RH with language dominance being nearly equally distributed between hemispheres in contrast to right-handers.