NEW YORK, NY (May 1, 2014) Researchers have identified two types of neurons that enable the spinal cord to control skilled forelimb movement. The first is a group of excitatory interneurons that are needed to make accurate and precise movements; the second is a group of inhibitory interneurons necessary for achieving smooth movement of the limbs. The findings are important steps toward understanding normal human motor function and potentially treating movement disorders that arise from injury or disease.
"We take for granted many motor behaviors, such as catching a ball or flipping a coin, that in fact require considerable planning and precision," said Columbia University Medical Center's (CUMC's) Thomas M. Jessell, PhD, a senior author of both studies, which were published separately in recent issues of Nature. "While such motor acts seem effortless, they depend on intricate and carefully orchestrated communication between neural networks that connect the brain to the spinal cord and muscles."
To move one's hand to a desired target, the brain sends the spinal cord signals, which activate the motor neurons that control limb muscles. During subsequent movements, information from the limb is conveyed back to the brain and spinal cord, providing a feedback system that can support the control and adjustment of motor output.
"But feedback from muscles is not quick enough to permit the most rapid real-time adjustments of fine motor control," said Dr. Jessell, "suggesting that there may be other, faster, systems at play." Dr. Jessell is the Claire Tow Professor of Motor Neuron Disorders in the Departments of Neuroscience and of Biochemistry and Molecular Biophysics, co-director of the Mortimer B. Zuckerman Mind Brain Behavior Institute, co-director of the Kavli Institute for Brain Science, and a Howard Hughes Medical Institute investigator, all at Columbia.
Researchers had suspected that one rapid form of feedback m
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Columbia University Medical Center