A Study on How Fear Persists in the Mouse Brain %

We all have had moments of intense panic due to the fear of the unknown or an undesirable outcome. Our hands get shaky and sweat profusely, our knees feel wobbly and we start to freeze in response. In order to study this phenomenon, researchers observed the brain of a mouse on the cellular level during the persistent display of fear behavior. Neurologists discovered the neural mechanisms underlying persistent fear responses that were encoded in the hypothalamus rather than the cortex where persistent activity was previously usually associated with. They concluded that persistent fear states were not only due to persistently elevated stress hormones but also involved persistent electrical activity in the brain.

Traditionally, mice have well-characterized defensive behaviors such as fleeing or freezing in response to something that might impose danger. For instance, when a rat was put near the mouse’s experimental area, it would hug up against a wall at one corner to protect itself. In the research, the main focus was ‘Ventromedial Hypothalamus’ (VMH) which is responsible for this defensive behavior in mice. VMH neurons are activated when an imminent danger, for instance, a rat, was presented in front of the mouse and these neurons lasted for tens of seconds even after the rat was taken away. This was a new finding as neurons are usually only active for a few milliseconds which led to the team finding out that they could artificially stimulate these neurons.

Researchers continue their work on studying the ventromedial hypothalamus and its response to fear and panic so that not only the evolution of animals could be better understood but also to provide better and sustainable solutions to panic disorders in humans.