Laterality shifts in neural activation coupled to language ability

• 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.

Ämnesord

HUMANIORA  -- Språk och litteratur -- Jämförande språkvetenskap och allmän lingvistik (hsv//swe)

HUMANITIES  -- Languages and Literature -- General Language Studies and Linguistics (hsv//eng)

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Radiologi och bildbehandling (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Radiology, Nuclear Medicine and Medical Imaging (hsv//eng)

Nyckelord

Language ability

healthy adults

lateralization

fMRI

temporal lobe

inferior frontal gyrus

performance

difficulty

semantic

fluency

language

Publikations- och innehållstyp

vet (ämneskategori)

ovr (ämneskategori)