NARSAD Distinguished Investigator Grantee and professor of psychology Michael S. Fanselow, Ph.D., with NARSAD Young Investigator Grantee Stephanie Bissiere, Ph.D. and research team at the University of California Los Angeles, showed that when the hippocampus, the part of the brain responsible for learning and memory, is damaged, the brain activates new neuronal circuits in other regions to compensate for the loss of function. They also showed that the same circuits that compensate for loss of the hippocampus are important for both fear learning, the root cause of anxiety disorders and also for fear extinction, the main line of treatment for anxiety disorders. The findings published online in Proceedings of the National Academy of Sciences earlier this week could potentially help researchers develop new treatments for anxiety and other brain and behavior disorders.
The research team, composed of scientists from the University of California Los Angelses and Monash University in Melbourne, Australia, performed experiments on rats to show that the animals were able to learn new tasks even after their hippocampus was damaged. Whereas these rats required more training than rats with undamaged brains, when they were given a problem to solve, their brains were still able to learn though experience. The findings suggest that a region in the brain called the prefrontal cortex takes over from the damaged hippocampus to create alternative compensatory neuronal pathways.
Additionally, the team found that loss of one of the prefrontal regions they were studying, the infralimbic cortex, causes fear to be generalized to a safe place. “Without the infralimbic cortex the rats were unable to distinguish between a dangerous and safe environment, expressing fear in both situations. Such inappropriate fears are a hallmark of anxiety disorders,” explained Dr. Fanselow. “This is a vitally important finding because we may be able to help anxiety patients if we promote activity within the infralimbic cortex. But it is an issue we need to do more work on.”