Controlling Cockroaches: Neurons Shed Light On Insect's Movement

Identifying the neurons in a cockroach's brain that enable it to walk may help scientists develop better remote-controlled technology, a new study has revealed. Researchers from Case Western Reserve University (CWRU) identified the specific neurons that govern walking speed and direction. Now researchers believe they can simulate these neurons selectively and cause a cockroach to move accordingly.

"The central complex appears to be an area of the insect brain that monitors many forms of sensory information as well as the insect's internal state, and then influences various forms of movement," Roy Ritzmann, a biology professor at CWRU, said in a news release.

Essentially, the central complex acts like a joystick, which can be used to ultimately control the insect's speed and direction, Joshua Martin, a postdoctoral researcher in Ritzmann's lab, further explained.

For their study, researchers inserted tiny wires into the central complex of 27 free-walking cockroaches which allowed them to record neural activity as the insects moved around. The electrodes of the tiny wires were placed in an area of the brain that responds to antennal and visual inputs and that ultimately sends messages to the brain that allow the insects to navigate. Then they videotaped the cockroaches as they changed course and speed so that they mark spikes in brain activity with specific movements.

"The neural activity is generated in the center of the cockroach brain," said Joshua Martin, a postdoctoral researcher in Ritzmann's lab. "The outputs from the central complex are sent to the motor center in the thoracic ganglia – its version of the spinal cord – and on to the limbs."

To test whether or not they could direct the cockroaches to replicate movement while bypassing visual and antennal stimuli, researchers sent an electrical current through the same electrodes and recorded that activity.

"For the vast majority of cockroaches we tested, if you stimulate the cells you saw were active before the turn or slow or fast walk, you get the same movement every time you stimulate them," Martin said in the release.

As a walking insect turns, its legs change from pushing back off the surface to reaching out and pulling laterally. This triggers a reflex that allows them to basically change the way their leg joints are coordinated. Researchers were also able to directly control these reflexes when stimulating neurons.

"It is highly likely that descending motor control such as this also resides in all legged animals, including us," Ritzmann said in a statement. "So this kind of study, with the technical advantages that insects afford researchers, can help to understand how movement is generally controlled in complex environments."

Their study sheds light on the control of movement, not just in insects, but in other species as well. Researchers believe that the mechanisms behind the cockroach's system could be applied to helping the handicapped walk, building more stable robots, and improving self-driving cars and drones. The study's findings were recently published in the journal Current Biology.

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