Researchers suggest the findings show that the bilingual brain is more efficient and economical, as it uses fewer - and only specialized - regions when focusing on a task.
Researchers at the Université de Montréal in Canada came to this conclusion after studying brain connections in older people with the help of brain imaging.
Senior author Prof. Ana Inés Ansaldo, whose laboratory investigates the effects of language processing and aging brain plasticity, says:
"After years of daily practice managing interference between two languages, bilinguals become experts at selecting relevant information and ignoring information that can distract from a task."
When we are engaged in a task, our brains recruit different networks, depending on the nature of the task.
Prof. Ansaldo and colleagues found that when performing a task that requires concentration on a specific piece of information, the brains of monolingual seniors recruited a large circuit with several connections. However, the brains of their bilingual counterparts recruited a smaller circuit that was more relevant to the required information.
'React to object color but not position'
When concentrating on an object, the brain uses circuits that deal with visual function (color, for example) and motor function (such as spatial information).
For the study, the team invited two groups of seniors - 10 monolingual and 10 bilingual - to perform a task during which they had to focus on the color of an object while ignoring its position.
The task involved responding to a screen on which yellow or blue squares appeared one at a time and at random, either on the left or the right.
Participants were instructed to press a key on the left if they saw a yellow square, and a key on the right if they saw a blue one - regardless of the object's position on the screen.
The task tests "interference control," as the participant is challenged not to press a key just because it corresponds to the object's position.
It is similar to the challenge of learning to reverse a trailer - to make the trailer go left in reverse, you have to turn the steering wheel to the right (and vice versa).
All participants (10 French speakers and 10 French and English speakers) were born and raised in Montreal and ranged in age from 63-84 years. The age at which the bilinguals acquired their second language ranged from 8-30.
As the participants performed the task, the researchers monitored their brain activity using functional MRI. This allowed them to compare functional brain connections in different areas of the brain.
Bilingual brains are 'more efficient and economical'
The results showed that the brains of the bilinguals had higher connectivity between the visual processing areas situated at the back of the brain. The researchers note that:
"These findings support the notion that the bilingual brain is able to deal with interference by allocating fewer and more task-specific resources, as reflected by the support of a smaller, more integrated visuospatial hub."
In contrast, the monolingual brain appears to rely on "a larger, and multifunctional network which includes a wide set of processing nodes dedicated to executive processing," they add.
Prof. Ansaldo, who is also a researcher at the Institut universitaire de gériatrie de Montréal, a center specially dedicated to seniors, says this means that "the bilingual brain is more efficient and economical, as it recruits fewer regions and only specialized regions."
To summarize, the team suggests that being bilingual can benefit the brain in two ways. Firstly, it conserves resources by having more centralized and specialized connections. Secondly, whereas the monolingual brain uses diverse brain connections, the bilingual brain achieves the same result without the use of the frontal regions, which are vulnerable to aging.
Perhaps, they add, this might explain why the bilingual brain appears better able to resist the signs of cognitive aging or dementia.
"We have observed that bilingualism has a concrete impact on brain function and that this may have a positive impact on cognitive aging. We now need to study how this function translates to daily life, for example, when concentrating on one source of information instead of another, which is something we have to do every day. And we have yet to discover all the benefits of bilingualism."
Prof. Ana Inés Ansaldo