Highlighting Faculty Member Michael Fanselow
Date published: 7/18/2017
Fear plays a critically important role in our lives; it triggers defensive behaviors that protect us from danger. However, fear that is disproportionate to threat causes anxiety disorders. My laboratory studies how experience and brain biology together determine fear.
According to the National Institute of Mental Health about 1/3 of all Americans will experience an anxiety disorder at some point in their lifetime. One particular debilitating anxiety disorder is Post-Traumatic Stress Disorder (PTSD), where experience of a very intense stress leads to devastating levels of fear and anxiety, often accompanied by depression, drug and alcohol abuse. Currently, we have, at best, partially successful treatments for these conditions. Given the high rate of anxiety disorders and their potentially devastating impact on the individuals and their families that suffer from them, we must improve our understanding of these conditions and develop new and/or improved treatments for these conditions.
Since protection against danger is so important to our survival, powerful fear systems evolved early on. My lab has done extensive work to map out the brain circuits that cause fear. These circuits are highly conserved in mammals. This gives us the opportunity to explore the fundamental biological basis of fear using laboratory rats and mice because the fear circuits in their brains are essentially the same as ours. With animals we can probe and manipulate the brain so that we understand, at a very basic science level, what produces normal fear and why we can develop the inappropriate fears that occur with anxiety disorders. Our ultimate goal is to find out how we can get the overly fearful brain back to a healthy state where fear protects and no longer compromises our behavior.
My lab has discovered much about these fear circuits and how they function. Deep inside our brain is a structure called the amygdala, named for its almond-like shape. When we are in a dangerous situation the amygdala’s job is to trigger all the reactions that characterize fear. We have found that after a frightening experience the amygdala stores the emotional memory for a lifetime by permanently changing the way the nerve cells within the amygdala communicate with each other. In particular, following strong stress, such as would occur in PTSD, the communication is disturbed so that greater than normal fear occurs regardless of the environment.
We have also worked extensively with another brain structure, the hippocampus. This is a brain structure that is necessary for forming our everyday memories. The hippocampus provides the amygdala with information about the context you are in and is necessary to remember places where we experienced important events. Loss of the hippocampus recapitulates many of the symptoms we see with conditions that disturb memory such as Alzheimer’s Disease. Thus our work also provides insights into how memory works.