The Neuroprotective Influence of Biligualism
Bilingualism is quite common in North America with many individuals speaking more than one language. In Canada, 20% of people have knowledge of both official languages (English and French; Statistics Canada, 2011), but there is likely a much higher proportion of bilingual individuals in Canada due to immigration, with many learning English or French in addition to their native language. Similar rates of bilingualism are also observed in the United States (Hyon & Kominski, 2010). Although it was previously believed that bilingualism could lead to a delay in language development of children, this has since been dispelled (McCabe et al., 2013) with studies showing that bi- or multi-lingual children are not at a greater risk for language impairment (Paradis et al., 2011) nor are they at a cognitive disadvantage (e.g. Bialystok, 2007). A growing body of research supports the idea that speaking multiple languages may actually have a neuroprotective influence during childhood and across the life span. Specifically, bilingualism promotes better executive control in childhood (Adescope et al., 2010) and in adulthood (Hilchey & Klein, 2011). There is also evidence suggesting that bilingualism protects against age-related cognitive decline (Bialystok, Craik, Klein & Viswanatha, 2004; Salvatierra & Rosselli, 2010) and enhances cognitive reserve (Stern, 2002).
ABSTRACT: The effect of life-long bilingualism on regional grey and white matter volume (2015)
Lifelong bilingualism is associated with the delayed diagnosis of dementia, suggesting bilingual experience is relevant to brain health in aging. While the effects of bilingualism on cognitive functions across the lifespan are well documented, less is known about the neural substrates underlying differential behaviour. It is clear that bilingualism affects brain regions that mediate language abilities and that these regions are at least partially overlapping with those that exhibit age-related decline. Moreover, the behavioural advantages observed in bilingualism are generally found in executive function performance, suggesting that the frontal lobes may also be sensitive to bilingualism, which exhibit volume reductions with age. The current study investigated structural differences in the brain of lifelong bilingual older adults (n=14, mean age=70.4) compared with older monolinguals (n=14, mean age=70.6). We employed two analytic approaches: 1) we examined global differences in grey and white matter volumes; and, 2) we examined local differences in volume and cortical thickness of specific regions of interest previously implicated in bilingual/monolingual comparisons (temporal pole) or in aging (entorhinal cortex and hippocampus). We expected bilinguals would exhibit greater volume of the frontal lobe and temporal lobe (grey and white matter), given the importance of these regions in executive and language functions, respectively. We further hypothesized that regions in the medial temporal lobe, which demonstrate early changes in aging and exhibit neural pathology in dementia, would be more preserved in the bilingual group. As predicted, bilinguals exhibit greater frontal lobe white matter compared with monolinguals. Moreover, increasing age was related to decreasing temporal pole cortical thickness in the monolingual group, but no such relationship was observed for bilinguals. Finally, Stroop task performance was positively correlated with frontal lobe white matter, emphasizing the importance of preserved white matter in maintaining executive function in aging. These results underscore previous findings implicating an association between bilingualism and preserved frontal and temporal lobe function in aging.
Olsen, R., Pangelinan, M., Bogulski, C., Chakravarty, M., Luk, G., Grady, C., & Bialystok, E. (2015). The effect of lifelong bilingualism on regional grey and white matter volume. Brain Research, 1612(1), 128-139. doi:10.1016/j.brainres.2015.02.034 http://www.sciencedirect.com/science/article/pii/S0006899315001341
PODCAST/WEBINAR: Bilingual Brain Symposium, Montreal Neurological Institute
Dr. Denise Klein, assistant professor at the Montreal Neurological Institute, discusses her recent findings from research on bilingual brains, from the benefits of optimal learning and plasticity in childhood to the protective factors of life-long bilingualism in older adults.
VIDEO: Bilingualism may delay dementia (2013) https://www.youtube.com/watch?v=NjLMsTm0s5I
Everyday Health interviews Dr. Stephen Rao of the Cleveland Clinic about a recent study that demonstrated bilinguals have a delayed onset of Alzheimer’s disease, fronto-temporal dementia, and vascular dementia compared to monolinguals.
- Gold, B., Kim, C., Johnson, N., Kryscio, R., & Smith, C. (2013). Lifelong bilingualism maintains neural efficiency for cognitive control in aging. The Journal of Neuroscience, 33(2), 387-396. http://www.jneurosci.org/content/33/2/387.short
- Kousaie, S., Sheppard, C., Lemieux, M., Monetta, L., & Taler, V. (2014). Executive function and bilingualism in young and older adults. Frontiers in Behavioral Neuroscience, 8, 250. http://journal.frontiersin.org/article/10.3389/fnbeh.2014.00250/abstract
- Kowoll, M., Degen, C., Gladis, S., & Schroder, J. (2015). Neuropsychological profiles and verbal abilities in lifelong bilinguals with mild cognitive impairment and Alzheimer's disease. Journal of Alzheimer's Disease, 45(4), 1257-1268. http://www.ncbi.nlm.nih.gov/pubmed/25697707