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1.
Peripheral feedback mechanisms acting on the central pattern generators for locomotion in fish and cat 总被引:2,自引:0,他引:2
O Andersson H Forssberg S Grillner P Wallén 《Canadian journal of physiology and pharmacology》1981,59(7):713-726
The feedback mechanisms taking part in the control of locomotion in cat and fish are reviewed, particularly with regard to position- and movement-related feedback. It is shown that in both fish and cat there is a powerful position-dependent negative feedback which will act only in the position range where the muscle activity normally changes, e.g., from extensor to flexor activity. In addition, there is positive feedback in the middle of the movement range which will act in certain conditions, e.g., to promote and maintain flexor activity during the flexion of the hind limb. 相似文献
2.
Hard-wired central pattern generators for quadrupedal locomotion 总被引:5,自引:0,他引:5
Animal locomotion is generated and controlled, in part, by a central pattern generator (CPG), which is an intraspinal network of neurons capable of producing rhythmic output. In the present work, it is demonstrated that a hard-wired CPG model, made up of four coupled nonlinear oscillators, can produce multiple phase-locked oscillation patterns that correspond to three common quadrupedal gaits — the walk, trot, and bound. Transitions between the different gaits are generated by varying the network's driving signal and/or by altering internal oscillator parameters. The above in numero results are obtained without changing the relative strengths or the polarities of the system's synaptic interconnections, i.e., the network maintains an invariant coupling architecture. It is also shown that the ability of the hard-wired CPG network to produce and switch between multiple gait patterns is a model-independent phenomenon, i.e., it does not depend upon the detailed dynamics of the component oscillators and/or the nature of the inter-oscillator coupling. Three different neuronal oscillator models — the Stein neuronal model, the Van der Pol oscillator, and the FitzHugh-Nagumo model -and two different coupling schemes are incorporated into the network without impeding its ability to produce the three quadrupedal gaits and the aforementioned gait transitions. 相似文献
3.
Dickinson PS 《Current opinion in neurobiology》2006,16(6):604-614
Central pattern generators are subject to extensive modulation that generates flexibility in the rhythmic outputs of these neural networks. The effects of neuromodulators interact with one another, and modulatory neurons are themselves often subject to modulation, enabling both higher order control and indirect interactions among central pattern generators. In addition, modulators often directly mediate the interactions between functionally related central pattern generators. In systems such as the vertebrate respiratory central pattern generator, multiple pacemaker types interact to produce rhythmic output. Modulators can then alter the relative contributions of the different pacemakers, leading to substantial changes in motor output and hence to different behaviors. Surprisingly, substantial changes in some aspects of the circuitry of a central pattern generator, such as a several-fold increase in synaptic strength, can sometimes have little effect on the output of the CPG, whereas other changes have profound effects. 相似文献
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Much can be deduced about the behavior of chains of oscillators under minimal assumptions about the nature of the oscillators or the coupling. This paper reviews work on such chains, and provides a framework within which implications may be drawn about the neural networks that govern undulatory locomotion in lower vertebrates. 相似文献
6.
Weakly coupled phase oscillators and strongly coupled relaxation oscillators have different mechanisms for creating stable
phase lags. Many oscillations in central pattern generators combine features of each type of coupling: local networks composed
of strongly coupled relaxation oscillators are weakly coupled to similar local networks. This paper analyzes the phase lags
produced by this combination of mechanisms and shows how the parameters of a local network, such as the decay time of inhibition,
can affect the phase lags between the local networks. The analysis is motivated by the crayfish central pattern generator
used for swimming, and uses techniques from geometrical singular perturbation theory. 相似文献
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In this paper we continue the analysis of a network of symmetrically coupled cells modeling central pattern generators for quadruped locomotion proposed by Golubitsky, Stewart, Buono, and Collins. By a cell we mean a system of ordinary differential equations and by a coupled cell system we mean a network of identical cells with coupling terms. We have three main results in this paper. First, we show that the proposed network is the simplest one modeling the common quadruped gaits of walk, trot, and pace. In doing so we prove a general theorem classifying spatio-temporal symmetries of periodic solutions to equivariant systems of differential equations. We also specialize this theorem to coupled cell systems. Second, this paper focuses on primary gaits; that is, gaits that are modeled by output signals from the central pattern generator where each cell emits the same waveform along with exact phase shifts between cells. Our previous work showed that the network is capable of producing six primary gaits. Here, we show that under mild assumptions on the cells and the coupling of the network, primary gaits can be produced from Hopf bifurcation by varying only coupling strengths of the network. Third, we discuss the stability of primary gaits and exhibit these solutions by performing numerical simulations using the dimensionless Morris-Lecar equations for the cell dynamics. 相似文献
9.
Buono PL 《Journal of mathematical biology》2001,42(4):327-346
We continue the analysis of the network of symmetrically coupled cells modeling central pattern generators (CPG) for quadruped locomotion proposed by Golubitsky, Stewart, Buono and Collins by studying secondary gaits. Secondary gaits are modeled by output signals from the CPG where each cell emits one of two different output signals along with exact phase shifts. Examples of secondary gaits are transverse gallop, rotary gallop, and canter. We classify secondary gaits that bifurcate when the Poincaré map of a primary gait has a real eigenvalue crossing the unit circle. In particular, we show that periodic solutions modeling transverse gallop and rotary gallop bifurcate from primary gaits. Moreover, we find gaits from period-doubling bifurcations and analyze plausible footfall patterns. Numerical simulations are performed using the Morris-Lecar equations as cell dynamics. 相似文献
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Allen I. Selverston Mikhail I. Rabinovich Henry D. I. Abarbanel Robert Elson Attila Szücs Reynaldo D. Pinto Ramn Huerta Pablo Varona 《Journal of Physiology》2000,94(5-6):357-374
Central pattern generating neurons from the lobster stomatogastric ganglion were analyzed using new nonlinear methods. The LP neuron was found to have only four or five degrees of freedom in the isolated condition and displayed chaotic behavior. We show that this chaotic behavior could be regularized by periodic pulses of negative current injected into the neuron or by coupling it to another neuron via inhibitory connections. We used both a modified Hindmarsh-Rose model to simulate the neurons behavior phenomenologically and a more realistic conductance-based model so that the modeling could be linked to the experimental observations. Both models were able to capture the dynamics of the neuron behavior better than previous models. We used the Hindmarsh-Rose model as the basis for building electronic neurons which could then be integrated into the biological circuitry. Such neurons were able to rescue patterns which had been disabled by removing key biological neurons from the circuit. 相似文献
12.
On the derivation and tuning of phase oscillator models for lamprey central pattern generators 总被引:1,自引:1,他引:0
Várkonyi PL Kiemel T Hoffman K Cohen AH Holmes P 《Journal of computational neuroscience》2008,25(2):245-261
Using phase response curves and averaging theory, we derive phase oscillator models for the lamprey central pattern generator from two biophysically-based segmental models. The first one relies on network dynamics within a segment to produce the rhythm, while the second contains bursting cells. We study intersegmental coordination and show that the former class of models shows more robust behavior over the animal's range of swimming frequencies. The network-based model can also easily produce approximately constant phase lags along the spinal cord, as observed experimentally. Precise control of phase lags in the network-based model is obtained by varying the relative strengths of its six different connection types with distance in a phase model with separate coupling functions for each connection type. The phase model also describes the effect of randomized connections, accurately predicting how quickly random network-based models approach the determinisitic model as the number of connections increases. 相似文献
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Valérie S Fénelon Béatrice Casasnovas John Simmers Pierre Meyrand 《Current opinion in neurobiology》1998,8(6):705-709
In contrast to the wealth of knowledge about the organizational rules of adult central pattern generators, far less is known about how these networks are assembled during development. The basic architecture for adult central pattern generators appears early in development but different generators may follow completely different developmental pathways to reach maturity. Recent evidence suggests that neuromodulatory inputs, in addition to their short-term adaptive control of central pattern generator activity, play a crucial role in both the final developmental tuning and the long-term maintenance of adult network function. 相似文献
15.
Golubitsky, Stewart, Buono and Collins proposed two models for the achitecture of central pattern generators (CPGs): one for bipeds (which we call leg) and one for quadrupeds (which we call quad). In this paper we use symmetry techniques to classify the possible spatiotemporal symmetries of periodic solutions that can exist in leg (there are 10 nontrivial types) and we explore the possibility that coordinated arm/leg rhythms can be understood, on the CPG level, by a small breaking of the symmetry in quad, which leads to a third CPG architecture arm. Rhythms produced by leg correspond to the bipedal gaits of walk, run, two-legged hop, two-legged jump, skip, gallop, asymmetric hop, and one-legged hop. We show that breaking the symmetry between fore and hind limbs in quad, which yields the CPG arm, leads to periodic solution types whose associated leg rhythms correspond to seven of the eight leg gaits found in leg; the missing biped gait is the asymmetric hop. However, when arm/leg coordination rhythms are considered, we find the correct rhythms only for the biped gaits of two-legged hop, run, and gallop. In particular, the biped gait walk, along with its arm rhythms, cannot be obtained by a small breaking of symmetry of any quadruped gait supported by quad. 相似文献
16.
Central pattern generators (CPGs) consisting of interacting groups of neurons drive a variety of repetitive, rhythmic behaviors
in invertebrates and vertebrates, such as arise in locomotion, respiration, mastication, scratching, and so on. These CPGs
are able to generate rhythmic activity in the absence of afferent feedback or rhythmic inputs. However, functionally relevant
CPGs must adaptively respond to changing demands, manifested as changes in oscillation period or in relative phase durations
in response to variations in non-patterned inputs or drives. Although many half-center CPG models, composed of symmetric units
linked by reciprocal inhibition yet varying in their intrinsic cellular properties, have been proposed, the precise oscillatory
mechanisms operating in most biological CPGs remain unknown. Using numerical simulations and phase-plane analysis, we comparatively
investigated how the intrinsic cellular features incorporated in different CPG models, such as subthreshold activation based
on a slowly inactivating persistent sodium current, adaptation based on slowly activating calcium-dependent potassium current,
or post-inhibitory rebound excitation, can contribute to the control of oscillation period and phase durations in response
to changes in excitatory external drive to one or both half-centers. Our analysis shows that both the sensitivity of oscillation
period to alterations of excitatory drive and the degree to which the duration of each phase can be separately controlled
depend strongly on the intrinsic cellular mechanisms involved in rhythm generation and phase transitions. In particular, the
CPG formed from units incorporating a slowly inactivating persistent sodium current shows the greatest range of oscillation
periods and the greatest degree of independence in phase duration control by asymmetric inputs. These results are explained
based on geometric analysis of the phase plane structures corresponding to the dynamics for each CPG type, which in particular
helps pinpoint the roles of escape and release from synaptic inhibition in the effects we find. 相似文献
17.
Ken Lukowiak 《Current opinion in neurobiology》1991,1(4):577-582
It has recently become possible to reconstruct a central pattern generator in tissue culture. This accomplishment will allow investigators to design and interpret experiments at a level not possible in in vivo preparations and enhance our understanding of the mechanisms that underlie the generation of rhythmic behaviour. 相似文献
18.
B. W. Verdaasdonk H. F. J. M. Koopman F. C. T. van der Helm 《Biological cybernetics》2009,101(1):49-61
Like human walking, passive dynamic walking—i.e. walking down a slope with no actuation except gravity—is energy efficient
by exploiting the natural dynamics. In the animal world, neural oscillators termed central pattern generators (CPGs) provide
the basic rhythm for muscular activity in locomotion. We present a CPG model, which automatically tunes into the resonance
frequency of the passive dynamics of a bipedal walker, i.e. the CPG model exhibits resonance tuning behavior. Each leg is
coupled to its own CPG, controlling the hip moment of force. Resonance tuning above the endogenous frequency of the CPG—i.e.
the CPG’s eigenfrequency—is achieved by feedback of both limb angles to their corresponding CPG, while integration of the
limb angles provides resonance tuning at and below the endogenous frequency of the CPG. Feedback of the angular velocity of
both limbs to their corresponding CPG compensates for the time delay in the loop coupling each limb to its CPG. The resonance
tuning behavior of the CPG model allows the gait velocity to be controlled by a single parameter, while retaining the energy
efficiency of passive dynamic walking. 相似文献
19.
Central pattern generators (CPGs) are localized neuronal networks that have the ability to produce rhythmic movements even in the absence of movement-related sensory feedback. They are found in all animals, including man, and serve as informative model systems for understanding how neuronal networks produce behavior. Traditionally, CPGs have been investigated with electrophysiological techniques. Here we review recent molecular and genetic approaches for dissecting the organization and development of CPGs. 相似文献
20.
V Henn 《Applied neurophysiology》1986,49(5):251-255