Search our Database of Scientific Publications and Authors

I’m looking for a
    Mechanisms of left-right coordination in mammalian locomotor pattern generation circuits: a mathematical modeling view.
    PLoS Comput Biol 2015 May 13;11(5):e1004270. Epub 2015 May 13.
    Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America.
    The locomotor gait in limbed animals is defined by the left-right leg coordination and locomotor speed. Coordination between left and right neural activities in the spinal cord controlling left and right legs is provided by commissural interneurons (CINs). Several CIN types have been genetically identified, including the excitatory V3 and excitatory and inhibitory V0 types. Recent studies demonstrated that genetic elimination of all V0 CINs caused switching from a normal left-right alternating activity to a left-right synchronized "hopping" pattern. Furthermore, ablation of only the inhibitory V0 CINs (V0D subtype) resulted in a lack of left-right alternation at low locomotor frequencies and retaining this alternation at high frequencies, whereas selective ablation of the excitatory V0 neurons (V0V subtype) maintained the left-right alternation at low frequencies and switched to a hopping pattern at high frequencies. To analyze these findings, we developed a simplified mathematical model of neural circuits consisting of four pacemaker neurons representing left and right, flexor and extensor rhythm-generating centers interacting via commissural pathways representing V3, V0D, and V0V CINs. The locomotor frequency was controlled by a parameter defining the excitation of neurons and commissural pathways mimicking the effects of N-methyl-D-aspartate on locomotor frequency in isolated rodent spinal cord preparations. The model demonstrated a typical left-right alternating pattern under control conditions, switching to a hopping activity at any frequency after removing both V0 connections, a synchronized pattern at low frequencies with alternation at high frequencies after removing only V0D connections, and an alternating pattern at low frequencies with hopping at high frequencies after removing only V0V connections. We used bifurcation theory and fast-slow decomposition methods to analyze network behavior in the above regimes and transitions between them. The model reproduced, and suggested explanation for, a series of experimental phenomena and generated predictions available for experimental testing.

    Similar Publications

    Organization of left-right coordination of neuronal activity in the mammalian spinal cord: Insights from computational modelling.
    J Physiol 2015 Jun;593(11):2403-26
    Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, USA.
    Key Points: Coordination of neuronal activity between left and right sides of the mammalian spinal cord is provided by several sets of commissural interneurons (CINs) whose axons cross the midline. Genetically identified inhibitory V0D and excitatory V0V CINs and ipsilaterally projecting excitatory V2a interneurons were shown to secure left-right alternation at different locomotor speeds. We have developed computational models of neuronal circuits in the spinal cord that include left and right rhythm-generating centres interacting bilaterally via three parallel pathways mediated by V0D , V2a-V0V and V3 neuron populations. Read More
    Central control of interlimb coordination and speed-dependent gait expression in quadrupeds.
    J Physiol 2016 Dec 8;594(23):6947-6967. Epub 2016 Nov 8.
    Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, USA.
    Key Points: Quadrupeds express different gaits depending on speed of locomotion. Central pattern generators (one per limb) within the spinal cord generate locomotor oscillations and control limb movements. Neural interactions between these generators define interlimb coordination and gait. Read More
    Dual-mode operation of neuronal networks involved in left-right alternation.
    Nature 2013 Aug 30;500(7460):85-8. Epub 2013 Jun 30.
    The Mammalian Locomotor Laboratory, Department of Neuroscience, Karolinska Institutet, Stockholm S-17177, Sweden.
    All forms of locomotion are repetitive motor activities that require coordinated bilateral activation of muscles. The executive elements of locomotor control are networks of spinal neurons that determine gait pattern through the sequential activation of motor-neuron pools on either side of the body axis. However, little is known about the constraints that link left-right coordination to locomotor speed. Read More
    Modelling genetic reorganization in the mouse spinal cord affecting left-right coordination during locomotion.
    J Physiol 2013 Nov 30;591(22):5491-508. Epub 2013 Sep 30.
    I. A. Rybak: Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA 19129, USA.
    The spinal neural circuit contains inhibitory (CINi) and excitatory (CINe) commissural interneurons with axons crossing the mid-line. Direction of these axons to the other side of the cord is controlled by axon guidance molecules, such as Netrin-1 and DCC. The cord also contains glutamatergic interneurons, whose axon guidance involves the EphA4 receptor. Read More