We might have more in common with a lamprey than we think, according to a new Northwestern University study on locomotion. At its core, the study of transparent zebrafish addresses a fundamental evolution issue: How did we get here?
Neuroscientists Martha W. Bagnall and David L. McLean have found that the spinal cord circuits that produce body bending in swimming fish are more complicated than previously thought.
Vertebrate locomotion has evolved from the simple left-right bending of the body exemplified by lampreys to the appearance of fins in bony fish to the movement of humans, with the complex nerve and muscle coordination necessary to move four limbs.
Bagnall and McLean report that differential control of an animal's musculature -- the basic template for controlling more complex limbs -- is already in place in the spinal networks of simple fish. Neural circuits in zebrafish are completely segregated: individual neurons map to specific muscles.
Specifically, the neural circuits that drive muscle movement on the dorsal (or back) side are separate from the neural circuits activating muscles on the ventral (or front) side. This is in addition to the fish being able to separately control the left and right sides of its body.
Ultimately, understanding more about how fish swim will allow scientists to figure out how humans walk.
"Evolution builds on pre-existing patterns, and this is a critical piece of the puzzle," McLean said. "Our data help clarify how the transition from water to land could have been accomplished by simple changes in the connections of spinal networks."
The findings will be published Jan. 10 in the journal Science. McLean, an assistant professor of neurobiology in the Weinberg College of Arts and Sciences, and Bagnall, a postdoctoral fellow in his research group who made the discovery, are authors of the paper.
"This knowledge will put us in a better position to
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