New research may help explain the ancient origins of the ‘deer in the headlights’ phenomenon


(WLNS) — Humans often freeze before we act when we face something unexpected and now researchers are hoping to be able to explain the ancient origins of the “startle response.”

The video above shows a race between two fruit flies or Drosophila melanogaster.

The fly at the top zips along at about 25 millimeters per second, the normal walking speed for Drosophila.

The slowpoke at the bottom of the video clocks in at a mere 15 millimeters per second which isn’t because of an injury or natural lack of speed, but rather a release of a chemical messenger in its nervous system that models a startle response.

A team from Columbia University discovered that fruit flies naturally release serotonin to turn on neural circuits that tells the flies to slow down.

You may have already heard about serotonin because of its role in regulating mood and appetite in humans, but for flies serotonin helps weather the stress of extreme temperatures, conserve energy during times of hunger and even walking upside down on the ceiling.

The research team found that serotonin’s most-powerful effect came during an actual startle response. Scientists suspect the release of serotonin activates motor neurons much like an emergency brake, stiffening and locking up the fly’s leg joints. When the researchers blocked the fly’s release of serotonin, it interrupted their normal startle response.

Drosophila contain many basic clues into human biology, whether the area of research is genetics, nutrition, biomechanics, or even the startle response.


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