Magazine article Science News

Unlocking the Gaits: Robot Tests Locomotion Switch

Magazine article Science News

Unlocking the Gaits: Robot Tests Locomotion Switch

Article excerpt

A blocky, bright-yellow robot that would look at home in a toy chest moves like a salamander, as its inventors intended. The robot and the mathematical model behind it provide insights into how vertebrates transitioned from swimming to walking, the researchers say.

Computer scientist Auke Jan Ijspeert of the Swiss Federal Institute of Technology in Lausanne and his colleagues chose to model the salamander because it resembles the first ten-estrial vertebrates. Salamanders can both swim and walk. A network of neurons located in the spinal cords of salamanders and other vertebrates triggers motion in the body's musculature that leads to the swimming gait. Another such network in the limbs produces a walking gait.

Each of these body and limb networks generates regular patterns of nerve cell activity that cause muscles to contract and relax in a rhythmic fashion. Ijspeert and his coworkers propose that the limb network appeared later in the salamander's evolutionary development than the body network. Coordination between the two networks enables salamanders to sometimes swim and sometimes walk.

The researchers also hypothesize that nerve cells within the limb network switch between muscle-contracting and musclerelaxing states more slowly than cells in the body network do. When the brain sends out signals in rapid succession, the limb network can't keep up, leaving the body network in command. At low frequencies of stimulation, the limb network overrides the body network and the animal walks.

To test their theories, the researchers first produced a mathematical model based on data on nerve and muscle function in salamanders and limbless animals. …

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