Scientists Discover Pathway of Fear

A normal amount of fear keeps us safe, but too much fear, as is the case with post-traumatic stress disorder, can prevent a healthy life. Wednesday, scientists at Cold Spring Harbor Laboratory (CSHL) announce the discovery of a new neural circuit in the brain that directly links the site of fear memory with an area of the brainstem that controls behavior, according to a press release announcing the findings.

For years, researchers have known that memories of fear are learned and stored in the amygdala. Events that we consider "scary" activate neurons in the lateral and then central portions of the amygdala. Once the message reaches the brainstem, the fear response is triggered.

In past research, CSHL associate professor Bo Li and his colleagues used new genetic techniques to determine the precise neurons in the central amygdala that control fear memory. His new research exploits these methods to understand how the central amygdala communciates fear to areas of the brain that control our fear response.

"In work published [Wednesday] in The Journal of Neuroscience, Li and his team identify a group of long-range neurons that extend from the central amygdala. These neurons project to an area of the brainstem, known as the midbrain periaqueductal gray (PAG), that controls the fear response," the release stated.

Li and his team conditioned animals to fear certain sounds by associated them with a shock. In these animals, the activity of the long-range projection neurons in the central amygdala became enhanced.

"This study not only establishes a novel pathway for fear learning, but also identifies neurons that actively participate in fear conditioning," said Li. "This new pathway can mediate the effect of the central amygdala directly, rather than signaling through other neurons, as traditionally thought."

The researchers said they hope to apply their findings to the treatment of PTSD. "We are working to find out how these circuits behave in anxiety disorders, so that we can hopefully learn to control fear in diseases such as PTSD," said Li.