Structural brain differences between Monolinguals and Bilinguals (original) (raw)
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Neuropsychologia
Two independent lines of research provide evidence that speaking more than one language may 1) contribute to increased grey matter in healthy younger and older adults and 2) delay cognitive symptoms in mild cognitive impairment (MCI) or Alzheimer disease (AD). We examined cortical thickness and tissue density in monolingual and multilingual MCI and AD patients matched (within Diagnosis Groups) on demographic and cognitive variables. In medial temporal disease-related (DR) areas, we found higher tissue density in multilingual MCIs versus monolingual MCIs, but similar or lower tissue density in multilingual AD versus monolingual AD, a pattern consistent with cognitive reserve in AD. In areas related to language and cognitive control (LCC), both multilingual MCI and AD patients had thicker cortex than the monolinguals. Results were largely replicated in our native-born Canadian MCI participants, ruling out immigration as a potential confound. Finally, multilingual patients showed a correlation between cortical thickness in LCC regions and performance on episodic memory tasks. Given that MULTILINGUALISM AND RESERVE 2 multilinguals and monolinguals were matched on memory functioning, this suggests that increased gray matter in these regions may provide support to memory functioning. Our results suggest that being multilingual may contribute to increased gray matter in LCC areas and may also delay the cognitive effects of disease-related atrophy.
Bilingualism: Language and Cognition, 2021
We examined the association between bilingualism, executive function (EF), and brain volume in older monolinguals and bilinguals who spoke English, Spanish, or both, and were cognitively normal (CN) or diagnosed with Mild Cognitive Impairment (MCI) or dementia. Gray matter volume (GMV) was higher in language and EF brain regions among bilinguals, but no differences were found in memory regions. Neuropsychological performance did not vary across language groups over time; however, bilinguals exhibited reduced Stroop interference and lower scores on Digit Span Backwards and category fluency. Higher scores on Digit Span Backwards were associated with a younger age of English acquisition, and a greater degree of balanced bilingualism was associated with lower scores in category fluency. The initial age of cognitive decline did not differ between language groups. The influence of bilingualism appears to be reflected in increased GMV in language and EF regions, and to a lesser degree, in EF.
Cortex, 2012
Cognitive reserve Atrophy Medial-temporal lobes a b s t r a c t Much of the research on delaying the onset of symptoms of Alzheimer's disease (AD) has focused on pharmacotherapy, but environmental factors have also been acknowledged to play a significant role. Bilingualism may be one factor contributing to 'cognitive reserve' (CR) and therefore to a delay in symptom onset. If bilingualism is protective, then the brains of bilinguals should show greater atrophy in relevant areas, since their enhanced CR enables them to function at a higher level than would be predicted from their level of disease. We analyzed a number of linear measurements of brain atrophy from the computed tomography (CT) scans of monolingual and bilingual patients diagnosed with probable AD who were matched on level of cognitive performance and years of education.
Multilingualism as cognitive reserve: delaying the onset of dementia in the elderly
A Journal for Undergraduate Research in the Netherlands, 2018
Multilingualism can be advantageous for an individual. It is thought to contribute to their cognitive reserve, the ability to resist brain damage. As such, there is evidence it might delay cognitive decline and dementia. The evidence comes from two types of studies. Firstly, studies comparing ages of onset of dementia show that there is a delay of 3-6 years in the appearance of symptoms in multilinguals, compared to monolinguals. This suggests multilingualism could enhance the brain’s ability to deal with decline. Secondly, studies comparing neuropathology in elderly participants with the same cognitive performance found multilinguals have higher levels of atrophy and damage in the brain than monolinguals. This further suggests multilingualism increases the brain’s resilience to damage. However, in both cases more research is needed to confirm multilingualism does indeed delay the onset of dementia, as confounding factors have been identified in both types of studies.
Bilingualism provides a neural reserve for aging populations
Neuropsychologia, 2015
It has been postulated that bilingualism may act as a cognitive reserve and recent behavioral evidence shows that bilinguals are diagnosed with dementia about 4-5 years later compared to monolinguals. In the present study, we investigated the neural basis of these putative protective effects in a group of aging bilinguals as compared to a matched monolingual control group. For this purpose, participants completed the Erikson Flanker task and their performance was correlated to gray matter (GM) volume in order to investigate if cognitive performance predicts GM volume specifically in areas affected by aging. We performed an ex-Gaussian analysis on the resulting RTs and report that aging bilinguals performed better than aging monolinguals on the Flanker task. Bilingualism was overall associated with increased GM in the ACC. Likewise, aging induced effects upon performance correlated only for monolinguals to decreased gray matter in the DLPFC. Taken together, these neural regions might underlie the benefits of bilingualism and act as a neural reserve that protects against the cognitive decline that occurs during aging.
The effect of lifelong bilingualism on regional grey and white matter volume
Brain research, 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 gre...
Effects of Bilingualism on Verbal and Nonverbal Memory Measures in Mild Cognitive Impairment
Journal of the International Neuropsychological Society : JINS, 2018
Maintaining two active languages may increase cognitive and brain reserve among bilingual individuals. We explored whether such a neuroprotective effect was manifested in the performance of memory tests for participants with amnestic mild cognitive impairment (aMCI). We compared 42 bilinguals to 25 monolinguals on verbal and nonverbal memory tests. We used: (a) the Loewenstein-Acevedo Scales for Semantic Interference and Learning (LASSI-L), a sensitive test that taps into proactive, retroactive, and recovery from proactive semantic interference (verbal memory), and (b) the Benson Figure delayed recall (nonverbal memory). A subsample had volumetric MRI scans. The bilingual group significantly outperformed the monolingual group on two LASSI-L cued recall measures (Cued A2 and Cued B2). A measure of maximum learning (Cued A2) showed a correlation with the volume of the left hippocampus in the bilingual group only. Cued B2 recall (sensitive to recovery from proactive semantic interferen...
Delaying the onset of Alzheimer disease: Bilingualism as a form of cognitive reserve
Neurology, 2010
Objectives: There is strong epidemiologic evidence to suggest that older adults who maintain an active lifestyle in terms of social, mental, and physical engagement are protected to some degree against the onset of dementia. Such factors are said to contribute to cognitive reserve, which acts to compensate for the accumulation of amyloid and other brain pathologies. We present evidence that lifelong bilingualism is a further factor contributing to cognitive reserve. Methods: Data were collected from 211 consecutive patients diagnosed with probable Alzheimer disease (AD). Patients' age at onset of cognitive impairment was recorded, as was information on occupational history, education, and language history, including fluency in English and any other languages. Following this procedure, 102 patients were classified as bilingual and 109 as monolingual. Results: We found that the bilingual patients had been diagnosed 4.3 years later and had reported the onset of symptoms 5.1 years later than the monolingual patients. The groups were equivalent on measures of cognitive and occupational level, there was no apparent effect of immigration status, and the monolingual patients had received more formal education. There were no gender differences. Conclusions: The present data confirm results from an earlier study, and thus we conclude that lifelong bilingualism confers protection against the onset of AD. The effect does not appear to be attributable to such possible confounding factors as education, occupational status, or immigration. Bilingualism thus appears to contribute to cognitive reserve, which acts to compensate for the effects of accumulated neuropathology. Neurology ® 2010;75:1726-1729 GLOSSARY AD ϭ Alzheimer disease; MMSE ϭ Mini-Mental State Examination. Although evidence has accumulated validating the role of cognitive reserve in protecting against age-related dementias, 1 the relation between such factors as education and enhanced cognitive reserve is necessarily correlational. That is, it is unclear whether intellectual, social, and physical activities genuinely improve cognitive performance, or whether individuals with better-functioning brains (perhaps for genetic reasons) are more likely to perform well intellectually and are also protected naturally against the onset of dementia. This is not the case for bilingualism: in the vast majority of cases people become bilingual not because they are naturally gifted language learners, but because of circumstances that require it. The possibility that bilingualism may contribute to cognitive reserve and thus be associated with a delayed onset of dementia was suggested by a series of studies showing that the constant use of 2 or more languages enhances aspects of attention and cognitive control across the lifespan. 2-4
Bilingualism Delays Expression of Alzheimer’s Clinical Syndrome
Dementia and Geriatric Cognitive Disorders
Objective: To evaluate the effects of bilingualism on the emergence of Alzheimer's clinical syndrome. Background: Studies have proposed an increase in cognitive and neural reserve from the management and control of two languages, with a consequent delayed expression of dementia. Methods: In a clinic with a large immigrant population, we identified 253 patients with probable Alzheimer's disease (AD) with intermediate or high evidence of AD pathophysiological process. These patients were reviewed for demographic variables, native language (L1) other than English, ages of onset and presentation, Mini-Mental State Examination (MMSE), digit spans, word fluencies, naming, and memory. Results: Among these patients, 74 (29.2%) were bilinguals with various L1s (Farsi, Spanish, Chinese, Tagalog, Arabic, others). When compared to the 179 monolingual AD patients, those who were bilingual had significant delays in ages of onset and presentation of approximately 4 years (p = 0.003). These delays persisted despite bilinguals having worse MMSE scores on presentation. There were no significant group differences on other variables except for worse naming in English among bilinguals versus monolinguals. Caregiver/informants reported that 66 (89.2%) of the 74 bilingual AD patients had gradually regressed to the predominant use of their L1. Conclusions: In line with published reports worldwide, we found that bilingualism delays the expression of Alzheimer's clinical syndrome. We also found frequent reversion to the first learned language. These findings suggest that, among bilinguals, the availability of an L1 "back-up" either facilitates compensation or masks emergence of the early symptoms of dementia.
Beneficial effect of bilingualism on Alzheimer's disease CSF biomarkers and cognition
Neurobiology of Aging, 2017
Bilingualism as a component of cognitive reserve has been claimed to delay the onset of Alzheimer's disease (AD). However, its effect on cerebrospinal fluid (CSF) AD-biomarkers has not been investigated. We assessed cognitive performance and CSF AD-biomarkers, and potential moderation effect of bilingualism on the association between age, CSF AD-biomarkers, and cognition. Cognitively healthy middle-aged participants classified as monolinguals (n ¼ 100, n CSF ¼ 59), early (n ¼ 81, n CSF ¼ 55) and late bilinguals (n ¼ 97, n CSF ¼ 52) were evaluated. Models adjusted for confounders showed that bilinguals performed better than monolinguals on digits backwards (early-bilinguals p ¼ 0.003), Judgment of Line Orientation (JLO) (early-bilinguals p ¼ 0.018; late-bilinguals p ¼ 0.004), and Trail Making Test-B (late-bilinguals p ¼ 0.047). Early bilingualism was associated with lower CSF total-tau (p ¼ 0.019) and lower prevalence of preclinical AD (NIA-AA classification) (p ¼ 0.02). Bilingualism showed a moderation effect on the relationship between age and CSF AD-biomarkers and the relationship between age and executive function. We conclude that bilingualism contributes to cognitive reserve enhancing executive and visual-spatial functions. For the first time, this study reveals that early bilingualism is associated with more favorable CSF AD-biomarker profile.