University of Maryland biologists announced on Aug. 6 that they have identified a physical mechanism in the brain that may explain why people often experience plateaus when learning new skills, such as languages or musical instruments. The team found that a scaffold-like structure surrounding brain cells, known as the extracellular matrix, controls when the brain can change during learning.
According to their findings published in the Proceedings of the National Academy of Sciences on August 3, this matrix loosens within hours after a practice session and rebuilds itself within about a day. This cycle allows learning from one session to take hold before another begins. As mastery develops, this rebuilding process fades and eventually stops altogether.
"For the first time, we've been able to see that the remodeling 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 UMD and senior author of the study. "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."
The researchers noted that previous studies considered this matrix in adult brains to be rigid and unchanging—a factor making it harder for adults to learn compared to children whose matrices are still immature and flexible. However, by tracking changes over shorter intervals than earlier research did, Caras's team observed rapid shifts in the matrix tied directly to training sessions.
To test whether loosening or disrupting this structure affects skill acquisition or retention, scientists used an enzyme to break down the matrix during experiments with animals. They found greater disruption led to slower progress mastering new skills; if disrupted after mastery was achieved, performance declined noticeably but was not entirely lost.
Caras said these results could inform approaches for hearing rehabilitation or language instruction: "If there's a safe way to briefly reopen the learning window, it could be possible to help them acquire the skills to interpret these signals from their implant," Caras said. The researchers plan further work identifying molecules involved in triggering these changes and exploring implications for hearing loss.
