Language remains strongly left-lateralized in older adults: A cross-sectional and longitudinal study.
Level 3 - non-randomized controlled study
Observational cohort study with a longitudinal follow-up component (design analogy for cognitive neuroscience)
PubMed 42539264 · doi:10.64898/2026.07.17.739182
What was done
Researchers evaluated language lateralisation in 115 healthy adults (57 female, 58 male; mean age 59.6 years) using functional MRI during an adaptive semantic decision task. Laterality indices (LIs) were computed via a bootstrap-based approach across whole-hemisphere, frontal, and temporal regions. Cross-sectional relationships with age were assessed using Pearson and Bayesian correlations. A subset of 15 participants underwent follow-up fMRI after a mean interval of 44.2 months to assess longitudinal changes.
What was found
Language activation was left-lateralised in 96% of participants and right-lateralised in 3%. Frontal and temporal laterality indices were strongly correlated. Analyses revealed no significant relationship between age and lateralisation across the cohort. In the longitudinal subset (n = 15), no significant changes in lateralisation occurred over the ~44-month interval, with Bayesian analyses supporting the absence of age-related differences and longitudinal shifts.
Why it matters
These findings suggest that hemispheric language dominance is stable across healthy ageing rather than becoming bilateral. This clarifies baseline neurobiology and indicates that ageing alone may not alter vulnerability to or recovery patterns from lateralised aphasia.
Limits
The longitudinal component had a very small sample size (n = 15), limiting power to detect subtle within-individual shifts over time. The cohort's mean age of 59.6 years captures late middle-age to early older age, leaving very advanced ages potentially underrepresented. Cognitive domains beyond semantic decision-making were not evaluated.
Cited by
- supports Language centers of the human brain are localized in the left hemisphere.