Study Provides Answers for the Famous ‘Freeze’ Response
A Columbia University study has identified serotonin as a chemical that triggers the body’s ‘freeze response’, the automatic deer-in-the-headlights reflex that freezes the body momentarily in response to a potential threat and has a key role in the storing of trauma.
The study, carried out on fruit flys, reveals that when a fly experiences an unexpected change to its surroundings, such as a sudden vibration, the release of serotonin helps to literally – and temporarily – stop the fly in its tracks.
These findings offer broad insight into the biology of the freeze response, a ubiquitous, yet mysterious, phenomenon that has been observed in virtually every animal studied to date, from flies to fish to people.
The paper’s senior author, Richard Mann, PhD, said: “Imagine sitting in your living room with your family and — all of a sudden — the lights go out, or the ground begins to shake.
“Your response, and that of your family, will be the same: You will stop, freeze and then move to safety.
“With this study, we show in flies that a rapid release of the chemical serotonin in their nervous system drives that initial freeze and because serotonin also exists in people, these findings shed light on what may be going on when we get startled as well.”
In the brain, serotonin is most closely associated with regulating mood and emotion.
However, previous research on flies and vertebrates has shown it can also affect the speed of an animal’s movement.
While these findings are specific to fruit flies, the ubiquity of serotonin and the startle response provides clues as to the chemical and molecular processes that occur when more complex animals, including people, get startled.
Going forward, the researchers hope to further investigate serotonin’s role in movement, as well as what other factors may be at play.
“Our results indicate that serotonin has the potential to interact with many different types of nerve cells in the fly nervous system, such as those that guide movement and process sensory information,” said Dr. Mann.
“As we and others continue to investigate, we hope to develop a detailed, molecular blueprint for locomotion that can be applied broadly to other animals, perhaps even people.”