Neurogenesis is the process through which new neurons and brain cells are formed. Simply said, exercise is critical for promoting neurogenesis and maintaining brain alertness. New neurons are produced throughout our lives in two places in the brain--the hippocampus and the cortex. The hippocampus is responsible for forming new memories while the cortex controls higher functions such as reasoning and judgment. As we age, the number of neurons in our brains decreases which can lead to cognitive problems. However, exercise has been shown to increase the production of neurotrophic factors, which help protect and support neurons. There are several studies showing a connection between increased physical activity and increased neurogenesis. In one study, mice were given a drug that prevented them from exercising. This led to less neurogenesis in the hippocampus, but when the drug was removed, neurogenesis returned to normal levels. Mice that were allowed to exercise normally had more neurogenesis than sedentary mice. Another study showed that human patients who underwent surgery to remove tumors located near their hippocampus experienced improved memory function after being asked to walk on a treadmill for an hour a day. Other studies have shown similar results with healthy individuals who exercised regularly.