Researchers have identified a physical mechanism in the brain that could help explain why one makes rapid progress while learning a new skill but then hits a plateau.
A scaffold-like structure surrounding brain cells, called the extracellular matrix, loosens and rebuilds within about a day during the initial stages of picking up a new skill—the rebuilding cycle fades as the skill is mastered and eventually stops—researchers, including those from the University of Maryland, said.
It is as if the brain has decided that learning is finished and it’s time to protect what’s been gained, they said.
“For the first time, we’ve been able to see that the remodelling process changes as you gain experience. It happens early in learning, declines and then gradually stops,” said Melissa Caras, an assistant professor of biology at the University of Maryland and senior author of the study published in the journal Proceedings of the National Academy of Sciences.
“This tells us that the brain isn’t just passively storing what you learn; it’s also actively regulating when learning can happen and when it should stop, so that the skills you’ve built are protected rather than overwritten,” Caras said.
The extracellular matrix helps control when the brain can change during learning. In the auditory cortex, the matrix loosens within hours of a practice session and rebuilds itself within about a day—a cycle that lets the learning from a session take hold before the next one, the researchers said.
They added that for decades, the matrix in adult brains was viewed as a rigid barrier, a scaffold that holds the brain wiring in place and makes learning harder as people age.
While previous studies caught glimpses of the matrix changing during learning as well, scientists sampled the matrix occasionally—often over days or weeks—and concluded that it rebuilt slowly over long periods.
Caras’s team tracked the matrix rebuilding cycle over much shorter intervals, resulting in findings that suggest that the adult matrix is far more dynamic.
Rather than sitting fixed in place, the matrix was seen to shift on a rapid rhythm tied to training—loosening after practising a skill to acquire it and then knitting back together by the next day.
The team used an enzyme to break down the matrix, which slowed learning. The more the matrix was disrupted, the greater the impairment—learning a skill and mastering it became more difficult.
Further, when the matrix was broken down after a skill was successfully mastered, performance began to slip.
While the team’s research is still in the early stages and far from a direct human application, they believe the results open intriguing possibilities, especially for how we currently approach learning and retention.
Based on the findings, Caras theorised that plateaus in language learning could result from the brain regions involved flipping from a “ready to learn” state into a more stable one, with the matrix sealing the gains in place.
