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Motor networks typically generate several related output patterns or gaits where individual neurons may be shared or recruited between patterns. We investigate how a vertebrate locomotor network is reconfigured to produce a second rhythmic motor pattern, defining the detailed pattern of neuronal recruitment and consequent changes in the mechanism for rhythm generation. Hatchling Xenopus tadpoles swim if touched, but when held make slower, stronger, struggling movements. In immobilized tadpoles, a brief current pulse to the skin initiates swimming, whereas 40 Hz pulses produce struggling. The classes of neurons active during struggling are defined using whole-cell patch recordings from hindbrain and spinal cord neurons during 40 Hz stimulation of the skin. Some motoneurons and inhibitory interneurons are active in both swimming and struggling, but more neurons are recruited within these classes during struggling. In addition, and in contrast to a previous study, we describe two new classes of excitatory interneuron specifically recruited during struggling and define their properties and synaptic connections. We then explore mechanisms that generate struggling by building a network model incorporating these new neurons. As well as the recruitment of new neuron classes, we show that reconfiguration of the locomotor network to the struggling central pattern generator (CPG) reveals a context-dependent synaptic depression of reciprocal inhibition: the result of increased inhibitory neuron firing frequency during struggling. This provides one possible mechanism for burst termination not seen in the swimming CPG. The direct demonstration of depression in reciprocal inhibition confirms a key element of Brown's (1911) hypothesis for locomotor rhythmogenesis.
Aiken,
Xenopus embryonic spinal neurons recorded in situ with patch-clamp electrodes--conditional oscillators after all?
2003, Pubmed,
Xenbase
Aiken,
Xenopus embryonic spinal neurons recorded in situ with patch-clamp electrodes--conditional oscillators after all?
2003,
Pubmed
,
Xenbase Bekoff,
Neural control of limb coordination. I. Comparison of hatching and walking motor output patterns in normal and deafferented chicks.
1987,
Pubmed Berg,
Balanced inhibition and excitation drive spike activity in spinal half-centers.
2007,
Pubmed Berkinblit,
Generation of scratching. II. Nonregular regimes of generation.
1978,
Pubmed Berkowitz,
Physiology and morphology indicate that individual spinal interneurons contribute to diverse limb movements.
2005,
Pubmed Berkowitz,
Spinal interneurons that are selectively activated during fictive flexion reflex.
2007,
Pubmed Berkowitz,
Both shared and specialized spinal circuitry for scratching and swimming in turtles.
2002,
Pubmed Bhatt,
Grading movement strength by changes in firing intensity versus recruitment of spinal interneurons.
2007,
Pubmed Briggman,
Imaging dedicated and multifunctional neural circuits generating distinct behaviors.
2006,
Pubmed Brown,
On the nature of the fundamental activity of the nervous centres; together with an analysis of the conditioning of rhythmic activity in progression, and a theory of the evolution of function in the nervous system.
1914,
Pubmed Buchanan,
The roles of spinal interneurons and motoneurons in the lamprey locomotor network.
1999,
Pubmed Buchanan,
Newly identified 'glutamate interneurons' and their role in locomotion in the lamprey spinal cord.
1987,
Pubmed Budick,
Locomotor repertoire of the larval zebrafish: swimming, turning and prey capture.
2000,
Pubmed Carter,
Simultaneous control of two rhythmical behaviors. I. Locomotion with paw-shake response in normal cat.
1986,
Pubmed Clarke,
Sensory physiology, anatomy and immunohistochemistry of Rohon-Beard neurones in embryos of Xenopus laevis.
1984,
Pubmed
,
Xenbase Currie,
Interruptions of fictive scratch motor rhythms by activation of cutaneous flexion reflex afferents in the turtle.
1989,
Pubmed Dale,
Reciprocal inhibitory interneurones in the Xenopus embryo spinal cord.
1985,
Pubmed
,
Xenbase el Manira,
Calcium-dependent potassium channels play a critical role for burst termination in the locomotor network in lamprey.
1994,
Pubmed Feldman,
Looking for inspiration: new perspectives on respiratory rhythm.
2006,
Pubmed Getting,
Emerging principles governing the operation of neural networks.
1989,
Pubmed Getting,
Mechanisms of pattern generation underlying swimming in Tritonia. IV. Gating of central pattern generator.
1985,
Pubmed Grillner,
Neuronal network generating locomotor behavior in lamprey: circuitry, transmitters, membrane properties, and simulation.
1991,
Pubmed Hellgren,
Computer simulation of the segmental neural network generating locomotion in lamprey by using populations of network interneurons.
1992,
Pubmed Jing,
Interneuronal basis of the generation of related but distinct motor programs in Aplysia: implications for current neuronal models of vertebrate intralimb coordination.
2002,
Pubmed Kahn,
The neuromuscular basis of swimming movements in embryos of the amphibian Xenopus laevis.
1982,
Pubmed
,
Xenbase Kahn,
The neuromuscular basis of rhythmic struggling movements in embryos of Xenopus laevis.
1982,
Pubmed
,
Xenbase Kimura,
alx, a zebrafish homolog of Chx10, marks ipsilateral descending excitatory interneurons that participate in the regulation of spinal locomotor circuits.
2006,
Pubmed Kosmidis,
Respiratory-like rhythmic activity can be produced by an excitatory network of non-pacemaker neuron models.
2004,
Pubmed Li,
A direct comparison of whole cell patch and sharp electrodes by simultaneous recording from single spinal neurons in frog tadpoles.
2004,
Pubmed
,
Xenbase Li,
The spinal interneurons and properties of glutamatergic synapses in a primitive vertebrate cutaneous flexion reflex.
2003,
Pubmed
,
Xenbase Li,
Spinal inhibitory neurons that modulate cutaneous sensory pathways during locomotion in a simple vertebrate.
2002,
Pubmed
,
Xenbase Li,
Dorsal spinal interneurons forming a primitive, cutaneous sensory pathway.
2004,
Pubmed
,
Xenbase Li,
Glutamate and acetylcholine corelease at developing synapses.
2004,
Pubmed
,
Xenbase Li,
Persistent responses to brief stimuli: feedback excitation among brainstem neurons.
2006,
Pubmed
,
Xenbase Li,
Primitive roles for inhibitory interneurons in developing frog spinal cord.
2004,
Pubmed
,
Xenbase Li,
Defining classes of spinal interneuron and their axonal projections in hatchling Xenopus laevis tadpoles.
2001,
Pubmed
,
Xenbase Lieske,
Reconfiguration of the neural network controlling multiple breathing patterns: eupnea, sighs and gasps [see comment].
2000,
Pubmed Marder,
Invertebrate central pattern generation moves along.
2005,
Pubmed McLean,
A topographic map of recruitment in spinal cord.
2007,
Pubmed Meyrand,
Construction of a pattern-generating circuit with neurons of different networks.
1991,
Pubmed Mortin,
Spinal cord segments containing key elements of the central pattern generators for three forms of scratch reflex in the turtle.
1989,
Pubmed Popescu,
Highly dissimilar behaviors mediated by a multifunctional network in the marine mollusk Tritonia diomedea.
2002,
Pubmed Ritter,
In vivo imaging of zebrafish reveals differences in the spinal networks for escape and swimming movements.
2001,
Pubmed Roberts,
Motoneurons of the axial swimming muscles in hatchling Xenopus tadpoles: features, distribution, and central synapses.
1999,
Pubmed
,
Xenbase Sautois,
Role of type-specific neuron properties in a spinal cord motor network.
2007,
Pubmed Sillar,
Modulation of swimming rhythmicity by 5-hydroxytryptamine during post-embryonic development in Xenopus laevis.
1992,
Pubmed
,
Xenbase Sillar,
The development of swimming rhythmicity in post-embryonic Xenopus laevis.
1991,
Pubmed
,
Xenbase Soffe,
Active and Passive Membrane Properties of Spinal Cord Neurons that Are Rhythmically Active during Swimming in Xenopus Embryos.
1990,
Pubmed
,
Xenbase Soffe,
Triggering and gating of motor responses by sensory stimulation: behavioural selection in Xenopus embryos.
1991,
Pubmed
,
Xenbase Soffe,
Two distinct rhythmic motor patterns are driven by common premotor and motor neurons in a simple vertebrate spinal cord.
1993,
Pubmed
,
Xenbase Soffe,
Motor patterns for two distinct rhythmic behaviors evoked by excitatory amino acid agonists in the Xenopus embryo spinal cord.
1996,
Pubmed
,
Xenbase Soffe,
The pattern of sensory discharge can determine the motor response in young Xenopus tadpoles.
1997,
Pubmed
,
Xenbase Stein,
Neuronal control of turtle hindlimb motor rhythms.
2005,
Pubmed Sun,
Differential inhibition of N and P/Q Ca2+ currents by 5-HT1A and 5-HT1D receptors in spinal neurons of Xenopus larvae.
1998,
Pubmed
,
Xenbase Taylor,
Analysis of oscillations in a reciprocally inhibitory network with synaptic depression.
2002,
Pubmed Tunstall,
Modelling inter-segmental coordination of neuronal oscillators: synaptic mechanisms for uni-directional coupling during swimming in Xenopus tadpoles.
2002,
Pubmed
,
Xenbase Wall,
A slowly activating Ca(2+)-dependent K+ current that plays a role in termination of swimming in Xenopus embryos.
1995,
Pubmed
,
Xenbase
