ABOVE: Manduca sexta hooked to a tether as it flies toward a plastic “flower”

When a hawk moth (Manduca sexta) hovers around a flower to sip nectar, it uses flight muscles that are coordinated by the timing of neuronal signals down to the millisecond, according to a study published in PNAS December 16.

A hawk moth’s flight muscles are controlled by only a few motor neurons. Researchers led by neuromechanist Simon Sponberg at Georgia Tech tracked the activity of these neurons by inserting small wires into the moths’ exoskeletons. The insects were tethered in place near a moving 3D-printed plastic flower that they attempted to fly toward. As the moths flexed their muscles, a computer recorded the action potentials generated by the neurons, and an accelerometer measured torque generated by muscle movements. Together, these measurements provided a picture of neuronal activity during flight....

The researchers found that the specific timing of neuronal signals seems to carry more information for controlling coordination than the number of signals or the magnitude of their action potentials. “People have recorded lots of muscles together before, but what we have shown is that all of these muscles are using timing codes,” says Joy Putney, a graduate student at Georgia Tech and a study coauthor, in a news release. “The way they are using these codes is consistent, regardless of the size of the muscle and how it is attached to the body.” 

J. Putney et al., “Precise timing is ubiquitous, consistent, and coordinated across a comprehensive, spike-resolved flight motor program,” PNAS, doi:10.1073/pnas.1907513116, 2019.

Emily Makowski is an intern at The Scientist. Email her at emakowski@the-scientist.com.

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