Yesterday I blogged that walking on a treadmill made studying flashcards enjoyable. I also felt my retention was noticeably better than when I studied sitting or standing in one place.
Thanks to Matt Weber I learned of a rat experiment that supports the idea I was more retentive. Long-term potentiation (LTP) is a long-lasting (hours) change in synapse properties caused by a certain type of electrical stimulation from electrodes. Leung et al. measured the amount of LTP produced by the electrodes when rats were in one of four states: (a) walking, (b) immobilized, (c) short-wave sleep, (d) rapid-eye-movement sleep. They found clear LTP in all four states, but the LTP was much larger (50% larger?) when the rats were walking during the stimulation. During the other three states the LTP was about the same.
The walking and immobilization conditions must have differed in many ways. Perhaps immobilization was uncomfortable. Perhaps it required more handling. And so on. Comparing just those two states, you might wonder if (a) walking produces changes that cause things to be remembered better or (b) any of the other walking/immobilization differences made things worse (e.g., the shock of handling reduces learning). The fact that immobilization and the two sleep states produced similar results argues against the second sort of explanation.