With the support of a NARSAD Young Investigator Grant, David Foster, Ph.D., led research to understand spatial memory in the hippocampus area of the brain. His findings, published online today in Nature, have potential clinical relevance for treating complex disorders such as schizophrenia.
When we plan a road trip, we may look at the map or use one of the many online services to predict the best possible route to our destination. But our own spatial memory also serves as a mapping device, retaining information about locations in a particular environment. Just as lab rats use their spatial memory to learn how to navigate through a maze to find food, we use our spatial memory to navigate through familiar streets, neighborhoods and locations in our city to get to our final destination. The hippocampus is the part of the brain, in both rats and humans that is responsible for spatial memory. Specialized cells in the hippocampus, called place-cells, have been proposed to play a role in navigational planning, but so far, researchers have lacked direct evidence to prove it.
Dr. Foster and postdoctoral fellow Dr. Brad Pfeiffer at Johns Hopkins University School of Medicine in Baltimore found that when rats were allowed to navigate through an open area, the hippocampus produced spatial signals that enabled the animals to find their way between known locations and also enabled the rats to find paths to novel locations.
The Hopkins researchers implanted rats with tiny electrodes that were lowered into their hippocampus, allowing researchers to record neuronal activity from over 250 cells in the animals’ brain as they navigated in search of food. The researchers observed that as the animals moved, place-cells reactivated prior spatial memories but also signaled to create novel routes between old and new locales that had not been linked to previous experiences. Mapping their cognitive circuit unraveled the rats’ intended future paths, a sort of “mental time travel.”
“This ability to look ahead in time and space and plan complex sequences of behavior may also contribute to high-level reasoning in people,” says Dr. Foster. “Understanding the basis for this ability in the brain can provide a new potential target for the treatment of disorders of cognition, like schizophrenia.”