Motion determines how an experience is stored in memory, optogenetics study suggests

The research was presented at Neuroscience 2010, the annual meeting of the Society for Neuroscience, held in San Diego.

"Our behavior seems to influence what we remember," said senior author Loren Frank, PhD, at the University of California, San Francisco. "We are encouraged to 'stop and smell the roses' with the idea that slowing down to take in our surroundings will enhance our memories of those experiences. But we don't know if the way we move changes the way we learn."

Rats placed in an unfamiliar room will move slowly and explore, even if food is present, while rats put in a familiar space rush to find food. While these behaviors are well-documented, how brain circuits change with different patterns of motion and exploration is unknown. The hippocampus, a brain circuit essential for memory formation, was thought to process memories in two ways: recording memories during movement and consolidating memories during immobility. But the new study shows that memory circuits change continuously.

The authors used optogenetics to make neurons in the hippocampus sensitive to light. When the neurons were laser- activated, the researchers could measure the flow of activity through the circuit as animals learned about a new place. They found that the pathway associated with storing and consolidating memories was most active when the animals moved slowly. At faster speeds, the balance shifted from these circuits to circuits bringing in info from the outside world.

"Our results suggest that the way an animal explores its environment could have a profound effect on how the memories for that experience are stored," Frank said.

Research was supported by Alfred P. Sloan Foundation, the Swartz Foundation, the John Merck Fund, the Helen Hay Whitney Foundation, the National Science Foundation, and the National Institutes of Health.