A goshawk relies on precise symmetrical motor control to fly (especially through tight spaces). Click here for an animated gif.
Whether it’s a bird flying, a kangaroo hopping or a human smiling, symmetrical actions are found throughout the animal kingdom. Many, such as breathing, are essential to life, but little has been known about how organisms actually carry out these sophisticated, coordinated movements.
The discovery of a new network of neurons in the nerve cords of fruit flies now sheds light on this phenomenon. In a study published online in Neuron in early October, Ellie Heckscher, PhD, assistant professor in the Department of Molecular Genetics and Cell Biology, and colleagues at the University of Oregon described how a population of interneurons—a class of “relay” neuron located in the spinal cord, which enables communication between sensory and motor neurons—allows fruit fly larvae to crawl in a straight line.
A better understanding of how these neurons function not only reveals the neurobiology of a fundamental motor process, but could lead to novel therapies for motor-system disorders such as amyotrophic lateral sclerosis (Lou Gehrig’s disease) or inform the construction of all-terrain robotic devices.
“We let the animal tell us what neurons are important for movement,” said Heckscher, who conducted the work while a post-doctoral fellow at the University of Oregon. “At random we went in, disrupted neuronal function, and then looked at how their behavior changed. We were able to identify the specific neuronal population that is required for executing normal, bilaterally symmetric motor patterns.”
Using behavioral screening, transmission electronmicroscopic reconstruction and neuronal activity recording in freely moving animals, the team discovered a novel sensorimotor circuit containing interneurons known as Even-skipped+ interneurons.
When these neurons were overstimulated or turned off, the researchers were able to disrupt symmetrical motion in fruit fly larvae without affecting other motor actions—the larvae could still crawl, but only asymmetrically.
“Our work could be likened to opening the hood of a car and mapping the wiring that allows the steering wheel to turn the wheels,’ Heckscher said. “While this study was conducted in fruit flies, these interneurons are evolutionarily conserved. Thus, our finding may be directly relevant to similar motor circuits at work in other organisms, including humans.”
To read more, visit the University of Oregon newsroom.
The study, “Even-Skipped+ Interneurons Are Core Components of a Sensorimotor Circuit that Maintains Left-Right Symmetric Muscle Contraction Amplitude” was supported by the National Institutes of Health (grant MH051383), American Heart Association, Howard Hughes Medical Institute and Wellcome Trust.
Additional authors include: Aref Arzan Zarin, Serge Faumont, Matthew Q. Clark, Laurina Manning, Shawn R. Lockery and Chris Doe at the University of Oregon; Akira Fushiki, Casey M. Schneider-Mizel, Richard D. Fetter, James W. Truman and Maarten F. Zwart at the Howard Hughes Medical Institute’s Janelia Farms Research Campus in Ashburn, Virginia; and Matthias Landgraf of the University of Cambridge.