FactSentinel

The claim misrepresents how the adult brain works. Neurons are not frozen in place after childhood. The brain keeps changing throughout life through neuroplasticity, the ability of neural circuits to strengthen, weaken, form, and prune connections in response to learning, experience, and injury. Each time a person learns a skill, forms a memory, or recovers function after a stroke, the connections between brain cells are physically reorganized. Studies of London taxi drivers, musicians, and people learning new languages show measurable structural changes in adult brains.

The claim also rests on an outdated idea. For much of the twentieth century, scientists believed adults could not generate new neurons. Research since the 1990s has challenged this, with evidence of neurogenesis in the hippocampus, a region tied to learning and memory. Whether and how much this occurs in adult humans is still debated, and some studies have found little evidence of it. Even so, the broader point holds: the brain's wiring is dynamic, even if the total number of neurons changes less than the connections among them.

A common misconception is that brain cells are simply lost with age and never replaced. Some neuron loss does occur, but healthy aging does not involve massive die-off, and lifestyle factors such as exercise, sleep, and mental engagement are associated with better brain health. The brain is better described as adaptable than as fixed.