Language skills stay strong in older adults, even while other cognitive abilities decline
By Health Correspondent
Getting older can bring changes to the brain, with some abilities such as working memory, attention and problem-solving becoming more difficult.
But language appears to be different.
A new study by researchers at the Massachusetts Institute of Technology (MIT) and Boston University has found that the part of the brain responsible for processing language remains remarkably similar in older and younger adults.
The findings suggest that some parts of the brain may be more resistant to ageing than others – particularly areas that are highly specialised for a particular job.
The study, published in Nature Communications, compared brain activity in people aged 17 to 39 with those aged 41 to 80.
Researchers looked at two different brain networks. One, known as the multiple demand network, is involved in tasks such as attention, working memory, decision-making and problem-solving. The other is the brain’s language network, which helps us understand spoken and written language.
The differences between the two networks were striking.
During a spatial memory task, the researchers found that the multiple demand network was less active and less well synchronised in older adults. The network was also smaller and showed weaker overall activation.
But when participants listened to stories and read sentences, the researchers found that activity in the language network was very similar in the two age groups.
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The older participants also showed similar responses when they encountered an unfamiliar word or an unusual grammatical construction.
That is important because previous research has shown that younger adults respond strongly to these kinds of linguistic challenges, with increased activity in the brain’s language areas.
The new study found that older adults showed the same pattern.
“We have previously used similar kinds of materials to show that young adults show strong sensitivity to these points of linguistic difficulty: activity in the language areas goes up,” says Evelina Fedorenko, an MIT associate professor of brain and cognitive sciences and a member of the MIT McGovern Institute for Brain Research.
“Here we found that in older adults, you also see this sensitivity, which suggests that there’s nothing fundamentally different about how they process language.”
A language network that stays strong
The researchers also looked at how closely different parts of the language network worked together. They found no evidence that the network became less synchronised with age, or that it became more mixed with the brain’s multiple demand network.
That is in contrast to the multiple demand network, which is involved in attention, working memory and problem-solving. In older adults, this network showed lower levels of activity and synchronisation.
“In the language network, we couldn’t find any differences between older and younger groups,” says Anne Billot, one of the study’s lead authors. “In contrast, the executive system showed decline across almost all of the measures.”
Can language skills improve with age?
The study did not test whether people’s language skills actually improve as they get older.
However, previous research suggests that vocabulary can continue to grow throughout adulthood.
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The researchers say this could be because people continue to build their knowledge of language through life experience, reading and everyday exposure to new words.
“Vocabulary keeps increasing as long as people have been measuring,” says Evelina Fedorenko. “People get exposed to more and more language, and older people sometimes start reading more, so they get an extra boost.”
Why does the brain age differently?
The findings raise the question of why some parts of the brain appear to be more resistant to ageing than others.
The language network is highly specialised, while the multiple demand network acts more like a flexible system, helping us adapt to new situations, learn new skills and tackle different kinds of problems.
The researchers suggest that this difference may help explain why the language network appears to be more resilient as we age.
“The multiple demand network is a different system in the sense that it’s not accumulating knowledge over time,” says Fedorenko. “It’s more like a flexible resource that you can deploy in all sorts of ways. And somehow that’s the thing that is more vulnerable to aging.”
Exactly why this happens is still unknown, and the researchers say understanding why some brain networks age differently will be an important area for future research.
The study was led by former MIT research assistant Niharika Jhingan and Anne Billot, with Evelina Fedorenko and Swathi Kiran, the James and Cecilia Tse Ying Professor in Neurorehabilitation at Boston University, as senior co-authors.
