A new pathway in the brain that controls fear, memory and behaviour in mouse has been discovered, offering mechanistic insight into how anxiety disorders may arise.
A team of researchers at Cold Spring Harbor Laboratory (CSHL) described this new circuit in the brain and found that fear was stored within a distinct region of the brain.
Associate Professor Bo Li, who led the team of researchers, explained that in their previous work, they had discovered that fear learning and memory were orchestrated by neurons in the central amygdale.
One possible candidate was a cluster of neurons that form the PVT, or paraventricular nucleus of the thalamus. This region of the brain is extremely sensitive to stress, acting as a sensor for both physical and psychological tension.
The researchers looked to see if the PVT plays a role in fear learning and memory in mice. They were able to see that neurons from the PVT extend deep into the central amygdala. Disrupting the connection significantly impaired fear learning.
The researchers then looked to data from people with post-traumatic stress disorder (PTSD) to identify chemical messengers that might connect the two structures. They focused on a molecule called BDNF that has been implicated in anxiety disorders. BDNF is a well-known neural growth factor that plays an important role in stimulating the birth of new neurons as well as new connections between neurons. Patients with anxiety disorders frequently have mutations in BDNF, suggesting that it might have a role in fear learning and memory.
They found that the addition of BDNF in the central amygdala acutely activates its neurons, triggering a fear response in animals that have not previously been exposed to a fearful stimulus, and promoting the formation of long-term fear memories.
The results provided mechanistic insight into a novel circuit that controls fear in the brain, and provides a target for the future treatment of anxiety disorders, said Li.
The work is published in Nature.