In a study two groups took a memory quiz. Then one group cycled to exhaustion in 30 minutes and the other group sat there. Their memories were then retested. The result:
“The exercised volunteers performed significantly better on the memory test than they had on their first try, while the volunteers who had rested did not
improve” – quote from the NY Times article How Exercise Benefits The Brain.
They also took blood samples throughout the experiment. They found that: “The cyclists had significantly higher levels of a protein known as brain-derived neurotrophic factor, or BDNF, which is known to promote the health of nerve cells. The men who had sat quietly showed no comparable change in BDNF levels.”