Search our Database of Scientific Publications and Authors

I’m looking for a
    Neuronal activity in the isolated mouse spinal cord during spontaneous deletions in fictive locomotion: insights into locomotor central pattern generator organization.
    J Physiol 2012 Oct 6;590(19):4735-59. Epub 2012 Aug 6.
    Department of Neurobiology and Behavior, Cornell University, W 159 Seeley G. Mudd Hall, Ithaca, NY 14853, USA.
    We explored the organization of the spinal central pattern generator (CPG) for locomotion by analysing the activity of spinal interneurons and motoneurons during spontaneous deletions occurring during fictive locomotion in the isolated neonatal mouse spinal cord, following earlier work on locomotor deletions in the cat. In the isolated mouse spinal cord, most spontaneous deletions were non-resetting, with rhythmic activity resuming after an integer number of cycles. Flexor and extensor deletions showed marked asymmetry: flexor deletions were accompanied by sustained ipsilateral extensor activity, whereas rhythmic flexor bursting was not perturbed during extensor deletions. Rhythmic activity on one side of the cord was not perturbed during non-resetting spontaneous deletions on the other side, and these deletions could occur with no input from the other side of the cord. These results suggest that the locomotor CPG has a two-level organization with rhythm-generating (RG) and pattern-forming (PF) networks, in which only the flexor RG network is intrinsically rhythmic. To further explore the neuronal organization of the CPG, we monitored activity of motoneurons and selected identified interneurons during spontaneous non-resetting deletions. Motoneurons lost rhythmic synaptic drive during ipsilateral deletions. Flexor-related commissural interneurons continued to fire rhythmically during non-resetting ipsilateral flexor deletions. Deletion analysis revealed two classes of rhythmic V2a interneurons. Type I V2a interneurons retained rhythmic synaptic drive and firing during ipsilateral motor deletions, while type IIV2a interneurons lost rhythmic synaptic input and fell silent during deletions. This suggests that the type I neurons are components of the RG, whereas the type II neurons are components of the PF network.We propose a computational model of the spinal locomotor CPG that reproduces our experimental results. The results may provide novel insights into the organization of spinal locomotor networks.

    Similar Publications

    Modelling spinal circuitry involved in locomotor pattern generation: insights from deletions during fictive locomotion.
    J Physiol 2006 Dec 28;577(Pt 2):617-39. Epub 2006 Sep 28.
    Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA.
    The mammalian spinal cord contains a locomotor central pattern generator (CPG) that can produce alternating rhythmic activity of flexor and extensor motoneurones in the absence of rhythmic input and proprioceptive feedback. During such fictive locomotor activity in decerebrate cats, spontaneous omissions of activity occur simultaneously in multiple agonist motoneurone pools for a number of cycles. During these 'deletions', antagonist motoneurone pools usually become tonically active but may also continue to be rhythmic. Read More
    Regional distribution of putative rhythm-generating and pattern-forming components of the mammalian locomotor CPG.
    Neuroscience 2013 Oct 8;250:644-50. Epub 2013 Aug 8.
    Center for Neuroscience, Faculty of Medicine, University of Alberta, 3-020D Katz Building, Edmonton, Alberta T6G 2H7, Canada.
    The ventromedial spinal cord of mammals contains a neural network known as the locomotor central pattern generator (CPG) which underlies the basic generation and coordination of muscle activity during walking. To understand how this neural network operates, it is necessary to identify, characterize, and map connectivity among its constituent cells. Recently, a series of studies have analyzed the activity pattern of interneurons that are rhythmically active during locomotion and suggested that they belong to one of two functional levels; one responsible for rhythm generation and the other for pattern formation. Read More
    Organization of flexor-extensor interactions in the mammalian spinal cord: insights from computational modelling.
    J Physiol 2016 Nov 21;594(21):6117-6131. Epub 2016 Jul 21.
    Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, USA.
    Key Points: Alternation of flexor and extensor activity in the mammalian spinal cord is mediated by two classes of genetically identified inhibitory interneurons, V1 and V2b. The V1 interneurons are essential for high-speed locomotor activity. They secure flexor-extensor alternations in the intact cord but lose this function after hemisection, suggesting that they are activated by inputs from the contralateral side of the cord. Read More
    Activity of Hb9 interneurons during fictive locomotion in mouse spinal cord.
    J Neurosci 2009 Sep;29(37):11601-13
    School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
    Hb9 interneurons (Hb9 INs) are putative components of the mouse spinal locomotor central pattern generator (CPG) and candidates for the rhythm-generating kernel. Studies in slices and hemisected spinal cords showed that Hb9 INs display TTX-resistant membrane potential oscillations, suggesting a role in rhythm generation. To further investigate the roles of Hb9 INs in the locomotor CPG, we used two-photon calcium imaging in the in vitro isolated whole neonatal mouse spinal cord preparation to record the activity of Hb9 INs, which were subsequently stained for unambiguous genetic identification. Read More