Cognitive aging has a well-documented shape: working memory slows, decision-making gets harder, and the brain’s executive-control systems show measurable wear. Language has always seemed to be the exception — older adults tend to hold onto their vocabularies, and some even keep expanding them well into old age. A new brain imaging study from MIT and Boston University now shows why: the neural machinery behind language doesn’t appear to age the way the rest of the brain does.

The study, a collaboration between MIT’s McGovern Institute for Brain Research and Boston University, compared brain activity in younger adults (ages 17 to 39) against older adults (ages 41 to 80) as both groups performed language tasks and a separate battery of executive-function tasks. The result: the brain’s language network looked nearly identical across age groups, while a second system, known as the multiple demand network, showed clear signs of decline in the older group.

The findings appear in Nature Communications. The paper’s lead authors are Anne Billot, who carried out the work as a PhD student at BU and is now a postdoc at Harvard University, and former MIT research assistant Niharika Jhingan. Evelina Fedorenko, an MIT associate professor of brain and cognitive sciences and McGovern Institute member, and Swathi Kiran, the James and Cecilia Tse Ying Professor in Neurorehabilitation at BU, are the paper’s senior co-authors.

Two systems, two different aging trajectories

“In the language network, we couldn’t find any differences between older and younger groups,” Billot said. “In contrast, the executive system showed decline across almost all of the measures. The network synchronization declined in older adults, the extent of activation was reduced, and the magnitude of activation was reduced as well.”

That contrast was the study’s starting hypothesis, drawn from decades of behavioral research. “It’s well known that executive functions, such as attention, working memory, and cognitive control, tend to decline with age. And it’s also known that in opposition to that, language skills typically tend to remain quite stable or even improve with age,” Billot said. “These two types of functions really go in opposite directions in healthy aging. In terms of behavior, that’s quite well-established, and we wanted to see if that was also the case in the brain.”

To isolate the two systems, the researchers designed separate tasks for each: a spatial memory task, which required participants to remember the location of squares in a grid, to probe the multiple demand network, and a language task involving listening to stories and reading sentences, to probe the language network. That design let the researchers map each participant’s individual language and executive-control regions rather than relying on a generic template, since the precise location of these networks varies somewhat from person to person.

Confirming the decline — and the exception

The spatial memory task confirmed what prior research on the multiple demand network had suggested: in older adults, this network was smaller, less synchronized, and produced weaker overall activation compared to younger adults’ networks.

The language task told a different story. Across both age groups, brain activity in response to language tasks showed similar levels and a similar spatial distribution throughout the network. The researchers also tested something more specific — how the brain responds when it hits a point of linguistic difficulty, such as an unfamiliar word or an unusual grammatical construction. In younger adults, these moments reliably produce a spike in activity in language-processing areas. The older adults in this study showed the same sensitivity.

“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,” Fedorenko said. “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.”

The researchers also tested two specific ways the language network might have quietly declined even while superficially appearing intact: reduced synchronization across the network, and a blurring of boundaries between the language network and the multiple demand network, both of which some neuroscientists have hypothesized could occur with age. Neither showed up in the data.

Why one network might be more resilient than another

The researchers frame the difference between the two networks as a difference in what each one is built to do. The language network is a specialized system, tuned over a lifetime to a fixed job. The multiple demand network is closer to a general-purpose resource, deployed flexibly across an enormous range of unrelated cognitive tasks — attention, planning, decision-making, and beyond.

“The multiple demand network is a different system in the sense that it’s not accumulating knowledge over time. 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,” Fedorenko said. “Why it’s so vulnerable — that is a very good question.”

That distinction may also explain why vocabulary, in particular, can keep growing across a lifetime rather than merely holding steady. Because the language network accumulates knowledge rather than functioning as a general resource, continued exposure to language keeps feeding it new material to work with. “Vocabulary keeps increasing as long as people have been measuring, which makes sense,” Fedorenko said. “People get exposed to more and more language, and older people sometimes start reading more, so they get an extra boost — it’s like a large language model trained on increasingly more data.”

The study didn’t directly measure language ability itself, only the underlying brain activity, so it can’t say precisely how the preserved network translates into real-world language performance for a given person. But it offers a mechanistic account for an effect long observed in behavior: that as other mental faculties become harder to rely on with age, the capacity for language — reading, listening, finding words — tends to remain remarkably intact.

The research was funded by the National Institute on Deafness and Other Communication Disorders, along with MIT’s McGovern Institute, the Simons Center for the Social Brain, the Poitras Center for Psychiatric Disorders Research, and the Quest for Intelligence.

Endnotes

• Massachusetts Institute of Technology, “Language skills stay strong in older adults, even while other cognitive abilities decline,” news release, August 24, 2026, https://www.eurekalert.org/news-releases/1140917.
• Anne Billot et al., “Preserved topography, lateralization, selectivity, and functional connectivity of the language network in older brains,” Nature Communications, 2026.