Brain Science: This Is Why Our Heads Don't Actually Explode When We're Learning

The human brain never stops fascinating us with its many skills and capabilities. New research shows how our brain can continue to learn without continuing to grow in size. Kurt Vinion/Getty Images

As babies and children grow and learn, their brain increases in size, but how does the brain continue to learn, even after it's done growing? Easy. As shown by a new study published now in Trends in Cognitive Sciences, brain cells "audition" to show their strength and ability to process new information. Those that make the cut remain and contribute to our newfound knowledge, and those that don't, well, they gotta go.

The new research helps to reshape our understanding of the brain and how it learns and remembers a new skill. Our past understanding of the brain would suggest that new knowledge requires new brain cells, and as a result our brain would grow in size upon each new skill we learn. We know this is not true, as the human brain stops growing in size somewhere during our mid-20s. Still, humans can continue to learn new information well into old age. Now, we know how.

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To study this, the international team, led by Elisabeth Wenger from the Max Planck Institute for Human Development in Berlin, referred back to past research on how the brain learns, giving particular attention to a study in which right-handed people learned to write and draw with their left hands. Here, the researchers observed brain volume increased initially as the volunteers learned a new skill, but then it shrunk back down to its original size after three weeks. Similar results were also seen in monkeys and rats as they were taught new skills.

Based on these previous findings, the team concluded that when the brain learns a new skill it initially increases in volume, but then after a process of elimination retains only the most useful brain cells, eliminating those not more effective, and thus eventually returning to its pre-learning size.

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"Brain matter volume increases in the initial stages of learning and then renormalizes [sic] partially or completely," said Wenger in a recent statement. "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."

The research adds further understanding to the neuroscience concept of plasticity. Brain plasticity refers to how the brain acquires new information by constantly reorganizing its neurons in order to function differently. As reported in the study, the concept was first put forward in 1894 by Nobel Prize winner Santiago Ramon y Cajal, who proposed that the brain undergoes physical changes in structure during learning. Now, over 100 years later, we understand the concept slightly better.

During plasticity, the brain reorganizes and assigns neurons new and different functions in order either to acquire a new skill or to overcome injury, such as a stroke or trauma, that may have caused serious neurological damage. Often, other parts of the brain will take over, learning the role of the lost brain cells as a way to compensate. For example, if the area of the brain associated with speech is destroyed, the brain may use plasticity to cause other areas of the brain not originally associated with this speech to learn the skill as a way to make up for lost cells.

The new findings show even further evidence of neural expansion and reorganization upon learning new information and provides us with a better understanding of our most amazing yet most misunderstood organ, our own brain.