Your Brain Swells—Then Deflates—While You Learn

Researchers hypothesize that the brain “auditions” various cells that form, but only keeps the best of the best

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Researchers have known for quite some time that learning causes the brain to change and realign—even grow larger. But if that is the case, why don't our brains eventually outgrow our skulls?

As Dana Dovey at Newsweek reports, scientists think they may have an answer to that conundrum: Although our our brains get bigger when we learn, our bodies heavily edit these cells. The opinion article, published in the journal Trends in Cognitive Science, suggests that majority of the new matter produced during the learning process is actually tossed out—only the most necessary is left behind.

The new cells produced during learning are like actors that “audition” for a place in the brain, with the brain functioning as a director, says Elisabeth Wenger, lead author of the paper and a neuroscientist at the Max Planck Institute for Human Development in Berlin, in a press release. After a new cells are created, the brain puts them through their paces, determining which ones function most efficiently. Those that don’t make the cut either wither away or are assigned different functions.

“Brain matter volume increases in the initial stages of learning, and then renormalizes partially or completely,”  Wenger says. “This seems to be an effective way for the brain to first explore the possibilities, call in different structures and cell types, select the best ones, and get rid of the ones that are no longer needed.” 

As Wenger tells Rafi Letzter at LiveScience, though the idea still needs to be confirmed, their early tests are promising. Wenger and her colleagues studied brain changes in 15 right-handed patients over over the course of seven weeks. During the test period, the team taught the participants to write with their left hand, occasionally scanning their brains using Magnetic Resonance Imaging (MRI). What they found is that the area of brains involved in muscle control grew 2 to 3 percent during the teaching but eventually shrunk back down to normal or near-normal size. 

Their subjects, however, did not lose their newly acquired skills. As Dovey reports, researchers have previously observed a similar phenomenon in rats and primates. 

Though the team hopes to confirm the latest result in future work, it’s very difficult to observe and measure these small changes in brain volume. Many factors can cause a person’s brain to swell and shrink—even drinking a couple glasses of water. And MRI machines suffer from plenty of noise.

“It’s so hard to observe and detect these volumetric changes, because, as you can imagine, there are also many noise factors that come into play when we measure normal participants in the MRI scanner,” Wenger tells Letzter.

The research could help scientists better understand neuroplasticity, the ability of the brain to reorganize and move “data” around after suffering damage. In fact, there are cases where people were able to function almost normally with just half a brain, with one hemisphere taking on functions from missing parts of the brain.

Next time you're studying something difficult, just think about how much you could be making your brain (albeit temporarily) swell.