Exercise doesn't cost you your memory

People, your nightly run isn't causing you to forget things. Contradicting earlier work, a team of researchers has confirmed that new neurons created via exercise don't erase old memories.

Exercise is well known for its cognitive benefits, thought to occur because it causes neurogenesis, or the creation of new neurons, in the hippocampus, which is a key brain region for learning, memory and mood regulation. Therefore, it was a surprise in 2014 when a research study, published in the journal Science, found that exercise caused mice to forget what they'd already learned.

"It stunned the field of hippocampal neurogenesis," said researcher Ashok K. Shetty of the Texas A and M University. "It was a very well-done study, so it caused some concern that exercise might in some way be detrimental for memory."

The animal models in the exercise group, in the previous study, showed far more neurogenesis than the control group, but contrary to what one might think, these additional neurons seemed to erase memories that were formed before they started the exercise regimen. To test this, the researchers removed the extra neurons and the mice suddenly were able to remember again.

"The mice who exercised had a large number of new neurons," Shetty said, "but somehow that seemed to break down the old connections, making them forget what they knew."

Shetty and his team decided to replicate this earlier research, using rats instead of mice. Rats are thought to be more like humans physiologically, with more-similar neuronal workings. They found that these animal models showed no such degradation in memories.

"We had completely contradictory findings from the 2014 study," said first author Maheedhar Kodali. "Now we need to study other species to fully understand this phenomenon."

"Exercise is not at all harmful," Shetty said. "It doesn't cause any memory problems, and there are many studies proving its benefits for making new memories and maintaining good mood. Now, our study showed that exercise does not interfere with memory recall ability. Keep exercising, and don't worry about losing your old memories."

The study appears in Journal of Neuroscience.