New research published in the journal Neuropsychologia reveals that bilingualism makes changes in brain structure that are linked with resilience against Alzheimer's disease and mild cognitive impairment.
More and more research has been pointing to bilingualism as a viable means for delaying or preventing Alzheimer's disease.
One study, for example, reported that being able to speak two languages could delay Alzheimer's by as much as 4.5 years.
Its authors then suggested that bilingualism may contribute to the development of certain brain areas that control executive function and attention tasks.
Whereas such studies only hypothesized that this was the case, a new study has used MRI data to examine brain regions associated with memory, which are known to be affected in Alzheimer's disease and its precursor, mild cognitive impairment (MCI).
The research was led by Natalie Phillips, a professor in the Department of Psychology at Concordia University in Quebec, Canada, and the first author of the study is Hilary D. Duncan, who is a Ph.D. candidate in psychology.
To the authors' knowledge, this is the first study that not only evaluated the brain areas responsible for language and cognition, but that has also established a link between the appearance of these areas and the functioning of memory in a group of people with Alzheimer's disease.
A further couple of aspects that set the new study apart from existing research, according to Prof. Phillips, is that the immigration status of the study participants was accounted for as a potential confounder, as well as the fact that the researchers used MRI data instead of computerized tomography scans, which are considered less reliable.
Bilingualism may offset brain damage
For their experiment, Prof. Phillips and team examined the brains and memory function of:
- 34 multilingual participants with MCI
- 34 monolingual participants with MCI
- 13 multilingual participants with Alzheimer's disease
- 13 monolingual participants with Alzheimer's disease
More specifically, the researchers looked at the so-called medial temporal lobes — which are key in memory formation — along with frontal areas of the brain.
"In areas related to language and cognitive control," the authors report, "both multilingual MCI and AD [Alzheimer's disease] 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."
"Our new study contributes to the hypothesis that having two languages exercises specific brain regions and can increase cortical thickness and gray matter density."
Prof. Natalie Phillips
"And," she adds, "it extends these findings by demonstrating that these structural differences can be seen in the brains of multilingual [Alzheimer's] and MCI patients."
"Our results contribute to research that indicates that speaking more than one language is one of a number of lifestyle factors that contributes to cognitive reserve," Prof. Phillips continues.
The concept of cognitive reserve refers to the brain's ability to cope with a challenge by finding alternative ways to complete a task.
The findings "support the notion that multilingualism and its associated cognitive and sociocultural benefits are associated with brain plasticity," adds Prof. Phillips. Brain plasticity describes the brain's ability to "reroute" or "rewire" itself.
She also shares some directions for future research, saying, "Our study seems to suggest that multilingual people are able to compensate for AD-related tissue loss by accessing alternative networks or other brain regions for memory processing."
"We're actively investigating that hypothesis now."