One of the most amazing things about the human brain is neuroplasticity -- the brain's ability to reorganize and restructure itself with new knowledge and experiences. Simply put, learning literally changes the brain.
While scientists used to think that the brain stopped developing in early childhood, we now know that the brain continues changing and adapting into middle and old age.
But we're still learning about the nature of plasticity. Researchers at Karolinska Institutet in Sweden have just discovered that the brain's plasticity doesn't work the way that neuroscientists had previously thought.
While previous theories of plasticity were formulated based on lab animals, the new research used human brains. Researchers found that a particular type of cell -- the oligodendrocyte, a building block of myelin, which is known to play an important role in communication between cells in the nervous system -- is far more sophisticated in human beings than in mice or rats, which may contribute to the human brain's superior plasticity.
Here's how it works: When we learn something new, nerve cells create new connections in the brain. These nerve cells are, therefore, important for storing new information in the brain. Our nerve impulses travel quickly, and myelin acts as an insulating layer protecting the nerve fibers (axons). In large quantities, myelin helps to speed up nerve impulses and to improve their function. When learning is taking place, there is an increase in myelin production in the area of the brain where the learning is occurring.
Studies on lab rodents have found that when the nerve cells need more myelin in order to create new neural connections, the existing oligodendrocytes are replaced with new oligodendrocytes. But when they were looking at the brains of 55 deceased people, the Karolinska researchers found that the same process does not take place in human beings, as had been previously assumed. Instead, the existing oligodendrocytes enact a process on their own to boost myelin production.
Unlike rats and mice, humans do not generate many new oligodendrocytes. However, we are still able to increase and modify myelin production as needed -- which suggests that the existing oligodendrocytes are in some way prepared to increase myelin production as called upon when the nerve cells are creating new brain connections.
This new understand could also have important applications for future treatments of neurological disorders in which myelin production plays a role, primarily neurodegenerative autoimmune diseases like multiple sclerosis.
“We were surprised by this discovery," Jonas Frisén, professor of stem cell research at Karolinska Institutet, said in a statement. "In humans, the existing oligodendrocytes modulate their myelin production, instead of replacing the cells as in mice. It is probably what enables us to adapt and learn faster. Production of myelin is vital in several neurological diseases such as MS. We now have new basic knowledge to build upon."
The study was published in the journal Cell.