Scientific American – In the 1990s researchers announced a series of discoveries that would upend a bedrock tenet of neuroscience.
For decades the mature brain was understood to be incapable of growing new neurons.
Once an individual reached adulthood, the thinking went, the brain began losing neurons rather than gaining them. But evidence was building that the adult brain could, in fact, generate new neurons.
In one particularly striking experiment with mice, scientists found that simply running on a wheel led to the birth of new neurons in the hippocampus, a brain structure that is associated with memory.
Since then, other studies have established that exercise also has positive effects on the brains of humans, especially as we age, and that it may even help reduce the risk of Alzheimer’s disease and other neurodegenerative conditions.
But the research raised a key question:
Why does exercise affect the brain at all?
Physical activity improves the function of many organ systems in the body, but the effects are usually linked to better athletic performance.
For example, when you walk or run, your muscles demand more oxygen, and over time your cardiovascular system responds by increasing the size of the heart and building new blood vessels.
The cardiovascular changes are primarily a response to the physical challenges of exercise, which can enhance endurance. But what challenge elicits a response from the brain?
Answering this question requires that we rethink our views of exercise. People often consider walking and running to be activities that the body is able to perform on autopilot.
But research carried out over the past decade by us and others would indicate that this folk wisdom is wrong. Instead exercise seems to be as much a cognitive activity as a physical one.
In fact, this link between physical activity and brain health may trace back millions of years to the origin of hallmark traits of humankind … Read more.