Laterality shifts in neural activation coupled to language ability
2013 (English)Manuscript (preprint) (Other academic)
The right-hemispheric homologues to Broca’s and Wernicke’s area play an important, but currently poorly understood role in language ability. In the current study, we tested 27 healthy adults for their language ability. We acquired functional magnetic resonance imaging (fMRI) data when the participants performed a sentence reading and a word fluency task. The fMRI data were used to calculate a measure of brain laterality – the laterality index – in the inferior frontal gyrus, the superior and middle temporal gyrus, and the angular gyrus. These laterality measurements were correlated with performance scores on language tasks administered prior to fMRI. We expected to see that high performance was characterized by a more efficient, i.e. decreased, neural activation pattern in typical language areas. Furthermore, we expected to see activation in additional, right-hemispheric brain regions in high performing subjects as a sign of neural adaptability.
High performance in a test measuring subtle language deficits (BeSS test) was related to increased activation in the right middle temporal gyrus when the participants were reading sentences. Thus, semantic ability correlated negatively with laterality in the temporal lobe, but not in the frontal lobe. For increased verbal fluency ability, we did observe a decreased left-hemispheric dominance in the inferior frontal gyrus when the participants were generating words. Increased task demands in the word generation task were not related to brain activation, but in the sentence reading task, the bilateral inferior frontal gyrus did exhibit an increase in activation when the sentences increased in difficulty. This result was independent of individual language ability. Increased brain activation at increased difficulty of a language task is interpreted as a sign that the brain recruits additional resources upon higher demands. The negative correlation between language ability and laterality in the in right-hemispheric middle temporal gyrus indicates a higher degree of neural adaptability in the temporal lobes of high skilled individuals.
Place, publisher, year, edition, pages
Language ability, healthy adults, lateralization, fMRI, temporal lobe, inferior frontal gyrus, performance, difficulty, semantic, fluency, language
General Language Studies and Linguistics Radiology, Nuclear Medicine and Medical Imaging
IdentifiersURN: urn:nbn:se:liu:diva-91044OAI: oai:DiVA.org:liu-91044DiVA: diva2:615922