As we learn to walk

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Newborn babies learn to walk just as the infant rats. Or, rather, the neural circuits that control locomotion are exactly the same, even if it is distant species millions of years, evolutionarily speaking. The discovery is Italian and was made ​​in the laboratories of the Foundation, Saint Lucia and the University of Rome Tor Vergata.

The study, coordinated by Nadia Dominici and published in Science , examines the development of human locomotion by comparing it with that of other mammals and birds. The movement, the researchers say, is a matter of the brain: it depends on the electrical impulses that neurons send to the muscles. By recording these electrical signals, then you can reconstruct the neural circuits that control limb movement.

Dominici has applied to the electrodes on the body of infants, preschool children and adults, with the aim of recording the electrical activity generated by 24 different skeletal muscles. Newborn babies, of course, do not walk. However, keeping them upright and moving along a surface will begin to raise your legs as if to take steps, showing the reflection of the so-called walking.

By analyzing the recorded electrical activity, the researchers found that, in infants, the reflection of the movement is controlled by neurons of the spinal cord, and these are activated in two stages: the first controls the muscles of the legs to bend and stretch, the second of alternating movement between the left leg and right. As the child grows, however, this process becomes more complex, involving other types of neurons: supra-medullary, intra-medullary and sensory. In preschool children, in fact, the neonatal stages are added two more that are used to refine the movement, like the one that commands us to lift the heels off the ground before the legs start to bow. The four stages, then, will further adjust as they grow, until you reach the perfection of adult locomotion.

These results show that the development is a conservative process. Until now it was thought that adult neural circuits underlying the movement was formed from scratch, and they were completely different from those active in children, and now it is understood that during growth does not throw anything away: the network of electrical signals comes from neurons to muscles is nothing but a modified version of the newborn.

And what applies to the development appears to apply also to the 'evolution. To get a broader overview of the mechanisms of locomotion in the animal kingdom, researchers have analyzed the electrical activity recorded from cats, rats, monkeys and chickens made of Guinea (the only other bipedal species considered, apart from humans) . It was found that the two phases of activity of the electric circuits of the newborn rats are identical to those of human infants.

You reach adulthood, however, the four stages of action begin to differ, as in rats ATRE animal species. The explanation probably is that men in the remodeling of neural circuits must deal with a problem that the four-legged (and bipeds such as birds) do not have: refine the movement of arms to reach and grasp objects.

Despite this difference, the researchers were very surprised at how similar are the processes that control the nervous animal locomotion. We're talking about millions and millions of distant species, who have inherited the coordination of muscle activity from primitive neural circuits belonging to a very old common ancestor. And although each species has learned to walk with "their legs" in a different way depending on genetic and morphological constraints, it is true that all start from a common base: the old elements are not eliminated completely in favor of a design again, but can be adapted to cope with new problems in a more than efficient.

Reference: Science DOI: 10.1126/science.1210617

Via Wired.it