Learning Rewires the Brain, Adding and Cutting Connections
The brain stops making most new cells by age 3, yet its wiring keeps changing for life.
Andrew Huberman · Accelerate Learning & Increase Cognitive Capacity | Dr. Tommy WoodAs an adult you are not growing many new brain cells when you learn something new. You are mainly changing how the cells you have connect to each other, by strengthening some connections and removing others.
That changeability is neuroplasticity, the brain's ability to adjust with experience. Dr. Tommy Wood, a doctor who studies the brain, described it as "the brain responding to inputs in order for us to then be able to better navigate and survive our environment." A large part of that process is pruning, which means removing connections between nerve cells that are not needed.
Many people confuse this rewiring with neurogenesis, the making of new neurons. The adult brain makes almost no new neurons, except for tiny numbers in two small areas tied to smell and memory. Compared with the rest of the brain, Wood says, you are not really making new cells.
A fixed number of cells can still keep learning because the connections keep changing. Take billiards as an example: improvement requires both sides of the process. Wood says it takes strengthening useful connections and removing others that reduce accuracy, though he adds that he does not know which side accounts for most of the gain.
That emphasis on removal starts early. The brain finishes making new neurons in large numbers when a child is about 2 or 3 years old, Wood says. After that, it mainly removes connections to refine language, movement, and social skills based on experience.
The same pruning continues through adult life. One possible reason we may lose a function later, Wood says, is that we stop giving the brain the inputs needed to maintain it, so pruning refines it away.
Questions people ask
If adults barely make new neurons, where do the few new ones appear?
In humans, the best accepted sites are the olfactory bulbs, which process smell, and the dentate gyrus of the hippocampus, which helps form memories. Even there, production is very small compared with the billions of existing neurons. Most learning happens through changes in connections, not through these newcomers.
Does pruning mean I am losing memories or getting dumber?
No. Pruning removes weak, noisy, or unused connections between neurons, which can make the remaining circuits faster and more accurate. It is similar to trimming a bush to leave a clearer shape. Problems arise mainly when useful circuits are pruned because they are no longer used.
Can I keep useful connections from being pruned away?
The broad principle is continued, challenging use. Regular practice, new variations on a skill, and exposure to complex social, motor, and language experiences give the brain reason to maintain those circuits. Long periods without that input signal that the wiring is expendable.