When a fruit fly detects an approaching predator, it takes just a fraction of a second to launch itself into the air and soar gracefully to safetybut there's not always time for that. Some threats demand a quicker getaway, even if things get a little clumsy. New research from scientists at the Howard Hughes Medical Institute's Janelia Research Campus reveals how a quick-escape circuit in the fly's brain overrides the fly's slower, more controlled behavior when a threat becomes urgent.
"The fly's rapid takeoff is, on average, eight milliseconds faster than its more controlled takeoff," says Janelia group leader Gwyneth Card. "Eight milliseconds could be the difference between life and death."
Card studies escape behaviors in the fruit fly to unravel the circuits and processes that underlie decision making, teasing out how the brain integrates information to respond to a changing environment. Her team's new study, published online June 8, 2014, in the journal Nature Neuroscience, shows that two neural circuits mediate fruit flies' slow-and-stable or quick-but-clumsy escape behaviors. Card, postdoctoral researcher Catherine von Reyn, and their colleagues find that a spike of activity in a key neuron in the quick-escape circuit can override the slower escape, prompting the fly to spring to safety when a threat gets too near.
A pair of neurons -- called giant fibers -- in the fruit fly brain has long been suspected to trigger escape. Researchers can provoke this behavior by artificially activating the giant fiber neurons, but no one had actually demonstrated that those neurons responded to visual cues associated with an approaching predator, Card says. She was curious how the neurons could be involved in the natural behavior if they didn't seem to respond to the relevant sensory cues, so she decided to test their role.
Genetic tools developed in the lab of Janelia executive director Gerald Rubin enabled Card's team to sw
|Contact: Jim Keeley|
Howard Hughes Medical Institute