- Emotional responses a exist in part of the brain called the amygdala
- Scientists find area of brain responsible for fear memories and learning to be afraid
- Findings could help the millions of people suffering with anxiety disorders
Researchers have found the pathway responsible for learning and remembering fear in mouse brains. Scientists at the Cold Spring Harbor Laboratory in New York found that the emotional centre, the amygdala, was connected to a cluster of nerve cells in the thalamus, the part of the brain that relays sensory information.
The researchers found that a stress-sensitive neuron cluster in the thalamus, called the PVT, has nerve cells that reach deep into the amygdala, emotion-processor and response coordinator of the brain. “We found that the PVT is specifically activated as animals learn to fear or as they recall fear memories,” says Professor Bo Li, study team leader. Blocking the PVT’s connection to the amygdala hindered the mice’s ability to learn fear.
The physical link between the PVT region and the amygdala is only part of the story. While specific nerve cells bridge the PVT and amygdala, there must be a chemical messenger travelling along it. Professor Li and his team looked and people suffering from post-traumatic stress disorder (PTSD), a type of anxiety disorder, to identify possible chemical messengers. They focused on BDNF, a chemical growth factor in nerve cells, which has been implicated in anxiety disorders before.
Adding BDNF to the amygdala stimulated fear, even when there was no fearful stimulus, and even caused long-term fear memories to form. “We established that this is a regulatory circuit that controls fear in mice: BDNF is the chemical messenger that allows the PVT to exert control over the central amygdala,” explains Professor Li.
Professor Li hopes the work will shed light on how anxiety disorders form in the brain and provide targets for treatments in the future. Anxiety disorders affect millions of people worldwide, approximately one in seven people in European and Anglo-American countries according to a 2013 study.