The effect of lifelong bilingualism on regional grey and white matter volume.
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. This article is part of a Special Issue entitled SI: Memory Å.
Rotman Research Institute, Baycrest Health Sciences, 3560 Bathurst Street, Toronto, ON, Canada M6A 2E1.
Rosanna K
RK
Olsen
Rotman Research Institute, Baycrest Health Sciences, 3560 Bathurst Street, Toronto, ON, Canada M6A 2E1.
Melissa M
MM
Pangelinan
Department of Psychology, York University, 4700 Keele St., Toronto, ON, Canada M3J 1P3.
Cari
C
Bogulski
Rotman Research Institute, Baycrest Health Sciences, 3560 Bathurst Street, Toronto, ON, Canada M6A 2E1; Cerebral Imaging Centre, Douglas Mental Health University Institute, 6875 LaSalle Boulevard, Montreal, QC, Canada H4H 1R3; Department of Psychiatry, McGill University, 1033 Pine Avenue West, Montreal, QC, Canada H3A 1A1; Department of Biomedical Engineering, McGill University, 3775 Rue University, Montreal, QC, Canada H3A 2B4.
M Mallar
MM
Chakravarty
Harvard Graduate School of Education, Appian Way, Cambridge, MA 02138, USA.
Gigi
G
Luk
Rotman Research Institute, Baycrest Health Sciences, 3560 Bathurst Street, Toronto, ON, Canada M6A 2E1; Department of Psychology, University of Toronto, 100 St. George Street, Toronto, ON, Canada M5S 3G3; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, ON, Canada M5T 1R8.
Cheryl L
CL
Grady
Rotman Research Institute, Baycrest Health Sciences, 3560 Bathurst Street, Toronto, ON, Canada M6A 2E1; Department of Psychology, York University, 4700 Keele St., Toronto, ON, Canada M3J 1P3. Electronic address: ellenb@yorku.ca.
Ellen
E
Bialystok
D000367:Age Factors; D000368:Aged; D000375:Aging / Q000523:psychology*; D000704:Analysis of Variance; D002540:Cerebral Cortex / Q000033:anatomy & histology / Q000502:physiology*; D005260:Female; D066128:Gray Matter / Q000033:anatomy & histology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D019303:Multilingualism; D009483:Neuropsychological Tests; D066127:White Matter / Q000033:anatomy & histology*
Aging; Bilingual; Cognitive reserve; Hippocampus; MRI; Volumetric