Interlimb coordination in 20‐day‐old rat fetuses

Bekoff, Anne; Lau, Bradley

doi:10.1002/jez.1402140207

Cited by 88 publications

(55 citation statements)

References 5 publications

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“…It was clear that coordinated cervical activity evoked by brain stem stimulation was less stable and robust than that observed in lumbar segments. Similar conclusions were drawn from work in late embryonic rats where bouts of hindlimb alternation where observed more frequently than those in the forelimbs (Bekoff and Lau 1980). From a practical viewpoint, this meant that we could elicit cervical rhythmicity for ϳ10 s before the rhythm degraded.…”

Section: Rhythmogenic Capability Of Cervicothoracic Regionssupporting

confidence: 66%

Interaction Between Developing Spinal Locomotor Networks in the Neonatal Mouse

Gordon¹,

Dunbar²,

Vanneste³

et al. 2008

Journal of Neurophysiology

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Gordon IT, Dunbar MJ, Vanneste KJ, Whelan PJ. Interaction between developing spinal locomotor networks in the neonatal mouse. J Neurophysiol 100: 117-128, 2008. First published April 24, 2008 doi:10.1152/jn.00829.2007. At birth, thoracosacral spinal cord networks in mouse can produce a coordinated locomotor-like pattern. In contrast, less is known about the cervicothoracic networks that generate forelimb locomotion. Here we show that cervical networks can produce coordinated rhythmic patterns in the brain stem-spinal cord preparation of the mouse. Segmentally the C 5 and C 8 neurograms were each found to be alternating left-right, and the ipsilateral C 5 and C 8 neurograms also alternated. Collectively these patterns were suggestive of locomotor-like activity. This pattern was not dependent on the presence of thoracosacral segments because they could be evoked following a complete transection of the spinal cord at T 5 . We next demonstrated that activation of thoracosacral networks either pharmacologically or by stimulation of sacrocaudal afferents could produce rhythmic activity within the C 5 and C 8 neurograms. On the other hand, pharmacological activation of cervical networks did not evoke alternating cervical rhythmic activity either in isolated cervicothoracic or -sacral preparations. Under these conditions, we found that activation of cervicothoracic networks could alter the timing of thoracosacral locomotor-like patterns. When thoracosacral networks were not activated pharmacologically but received rhythmic drive from cervicothoracic networks, a pattern of slow bursts with superimposed fast synchronous oscillations became the dominant lumbar neurogram pattern. Our data suggest that in neonatal mice the cervical CPG is capable of producing coordinated rhythmic patterns in the absence of input from lumbar segments, but caudorostral drive contributes to cervical patterns and rhythm stability.

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Section: Rhythmogenic Capability Of Cervicothoracic Regionssupporting

confidence: 66%

Interaction Between Developing Spinal Locomotor Networks in the Neonatal Mouse

Gordon¹,

Dunbar²,

Vanneste³

et al. 2008

Journal of Neurophysiology

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“…In the neonatal rat spinal cord, however, the similarity in frequencies of the independent cervical and lumbar generators seen after sucrose-block separation suggests that, here, phase coordination between lumbar and cervical locomotor circuitry derives principally from a caudorostral asymmetry in coupling pathways between the two spinal levels rather than from a "trailing oscillator" configuration (Matsushima and Grillner, 1992), in which lumbar oscillators with an intrinsically higher rhythmogenic capacity entrain their less excitable cervical partners. It is also relevant here that earlier in the developing rat spinal cord, the pathways mediating lumbocervical coupling appear to become functional after the lumbar (Nishimaru and Kudo, 2000) and cervical CPG circuits, because uncoordinated rhythmic forelimb and hindlimb movements can occur in the late embryonic animal (Bekoff and Lau, 1980). The anatomical pathways mediating lumbocervical coordination remain to be identified, although long ascending propriospinal pathways that are presumed to ensure hindlimb-forelimb coordination have been identified in cat spinal columns (English et al, 1985).…”

Section: Pathways Mediating Lumbar-thoracic Control Of Cervical Genermentioning

confidence: 99%

Propriospinal Circuitry Underlying Interlimb Coordination in Mammalian Quadrupedal Locomotion

Juvin¹,

Simmers²,

Morin³

2005

J. Neurosci.

199

174

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Soon after birth, freely moving quadrupeds can express locomotor activity with coordinated forelimb and hindlimb movements. To investigate the neural mechanisms underlying this coordination, we used an isolated spinal cord preparation from neonatal rats. Under bath-applied 5-HT, N-methyl-D,L-aspartate (NMA), and dopamine (DA), the isolated cord generates fictive locomotion in which homolateral cervicolumbar extensor motor bursts occur in phase opposition, as does bursting in homologous (left-right) extensor motoneurons. This coordination corresponded to a walking gait monitored with EMG recordings in the freely behaving animal. Functional decoupling of the cervical and lumbar generators in vitro by sucrose blockade at the thoracic cord level revealed independent rhythmogenic capabilities with similar cycle frequencies in the two locomotor regions. When the cord was partitioned at different thoracic levels and 5-HT/NMA/DA was applied to the more caudal compartment, the ability of the lumbar generators to drive their cervical counterparts increased with the proportion of chemically exposed thoracic segments. Blockade of synaptic inhibition at the lumbar level caused synchronous bilateral lumbar rhythmicity that, surprisingly, also was able to impose bilaterally synchronous bursting at the unblocked cervical level. Furthermore, after a midsagittal section from spinal segments C1 to T7, and during additional blockade of cervical synaptic inhibition, the cord exposed to 5-HT/NMA/DA continued to produce a coordinated fictive walking pattern similar to that observed in control. Thus, in the newborn rat, a caudorostral propriospinal excitability gradient appears to mediate interlimb coordination, which relies more on asymmetric axial connectivity (both excitatory and inhibitory) between the lumbar and cervical generators than on differences in their inherent rhythmogenic capacities.

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“…However, even while locomotor movements can be elicited immediately after birth during a narrow time window (Peiper, 1963) it takes a year before children can walk independently. From different studies, it has emerged that the same general sequential changes occur during the ontogeny of rhythmic motor behaviors in many vertebrates, including rats (Bekoff and Lau, 1980;Cazalets et al, 1990), birds (Watson and Bekoff, 1990), and amphibians (Stehouwer and Farel, 1985).…”

mentioning

confidence: 99%

Functional differentiation of adult neural circuits from a single embryonic network

Casasnovas¹,

Meyrand²

1995

J. Neurosci.

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The stomatogastric nervous system (STNS) of adult lobsters and crabs generates a number of different rhythmic motor patterns which control different regional movements of the foregut. Since these output patterns are generated by discrete neural networks that, in the adult, are well characterized in terms of synaptic and cellular properties, this system constitutes an ideal model for exploring the mechanisms underlying the ontogeny of neural network organization. The foregut and its rhythmic motor patterns were studied in in vitro STNS nerve-muscle preparations of the embryo and different larval stages of the lobster Homarus gammarus. The development of Homarus comprises a long embryonic stage in ovo followed by three pelagic larval stages prior to the onset of benthic life. During these stages the foregut itself develops slowly from a simple ectodermal invagination that occurs in the embryo. During successive larval stages it progressively acquires all the specialized structures and shape of the adult foregut. In contrast, the STNS is morphologically recognizable at early embryonic stages. In all recorded stages the STNS spontaneously expresses rhythmic motor activity. During development, this activity is progressively restructured, beginning with a single rhythmic motor pattern in the embryo where all the stomodeal muscles are strongly coordinated. In subsequent stages, however, this single pattern is progressively subdivided to give rise eventually to the three discrete rhythmic motor patterns characteristic of the adult STNS. Our data suggest that rather than a dismantling of redundant embryonic and larval neural networks, the different adult networks emerge as a progressive partitioning of discrete circuits from a single embryonic network.

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Interlimb coordination in 20‐day‐old rat fetuses

Cited by 88 publications

References 5 publications

Interaction Between Developing Spinal Locomotor Networks in the Neonatal Mouse

Interaction Between Developing Spinal Locomotor Networks in the Neonatal Mouse

Propriospinal Circuitry Underlying Interlimb Coordination in Mammalian Quadrupedal Locomotion

Functional differentiation of adult neural circuits from a single embryonic network

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