title: Internal and External Feedback Circuits for Skilled Forelimb Movement.
abstract: Skilled motor behavior emerges from interactions between efferent neural pathways that induce muscle contraction and feedback systems that report and refine movement. Two broad classes of feedback projections modify motor output, one from the periphery and a second that originates within the central nervous system. The mechanisms through which these pathways influence movement remain poorly understood, however. Here we discuss recent studies that delineate spinal circuitry that binds external and internal feedback pathways to forelimb motor behavior. A spinal presynaptic inhibitory circuit regulates the strength of external feedback, promoting limb stability during goal-directed reaching. A distinct excitatory propriospinal circuit conveys copies of motor commands to the cerebellum, establishing an internal feedback loop that rapidly modulates forelimb motor output. The behavioral consequences of manipulating these two circuits reveal distinct controls on motor performance and provide an initial insight into feedback strategies that underlie skilled forelimb movement.
authors.affiliation: Departments of Neuroscience and Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Kavli Institute for Brain Science, Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, New York 10032 tmj1@columbia.edu ea2471@columbia.edu.
authors.forename: Eiman
authors.initials: E
authors.lastname: Azim
authors.affiliation: Departments of Neuroscience and Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Kavli Institute for Brain Science, Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, New York 10032.
authors.forename: Andrew J P
authors.initials: AJ
authors.lastname: Fink
authors.affiliation: Departments of Neuroscience and Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Kavli Institute for Brain Science, Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, New York 10032 tmj1@columbia.edu ea2471@columbia.edu.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Jessell
mesh_terms: D000818:Animals; D005246:Feedback; D005552:Forelimb / Q000502:physiology*; D006801:Humans; D009043:Motor Activity / Q000502:physiology; D009068:Movement / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology*; D012677:Sensation / Q000502:physiology