Infants strut a runway wearing electrodes to show how the walking reflex works

By Laura Sanders

Web edition: February 13, 2013

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Before you can run, you have to walk, and before you can walk well, you have to walk like a brand-new baby. A new study uncovers the logistics of newborns’ herky-jerky, Frankensteinian stepping action and how this early reflex morphs into refined adult locomotion.

In the study, electrodes on infants’ chubby legs picked up signals from neurons that tell muscles to fire, revealing that three-day old babies tense up many of their leg muscles all at once. Toddlers, preschoolers and adults, by contrast, showed a progressively more sophisticated, selective pattern of neuron activity.

From birth to adulthood, motor neurons in the spine get an overhaul as neurons in different  locations along the spine become specialized for various aspects of walking, such as foot position, balance and direction, Yuri Ivanenko of the Santa Lucia Foundation in Rome and colleagues conclude in the Feb. 13 Journal of Neuroscience.

With a helper supporting about 70 percent of the newborn’s weight, a three-day old baby walks across a flat surface while electrodes record motor neuron activity.
Credit: Y. Ivanenko et al/J. of Neuroscience 2013