Central Pattern Generators Research Papers (original) (raw)

The question of how the central nervous system coordinates muscle activity is central to an understanding of motor control. The authors argue that motor programs may be considered as a characteristic timing of muscle activations linked to... more

The question of how the central nervous system coordinates muscle activity is central to an understanding
of motor control. The authors argue that motor programs may be considered as a characteristic timing of
muscle activations linked to specific kinematic events. In particular, muscle activity occurring during human
locomotion can be accounted for by five basic temporal components in a variety of locomotion conditions.
Spatiotemporal maps of spinal cord motoneuron activation also show discrete periods of activity. Furthermore,
the coordination of locomotion with voluntary tasks is accomplished through a superposition of motor
programs or activation timings that are separately associated with each task. As a consequence, the selection
of muscle synergies appears to be downstream from the processes that generate activation timings.

Motion of the upper limbs is often coupled to that of the lower limbs in human bipedal locomotion. It is unclear, however, whether the functional coupling between upper and lower limbs is bi-directional, i.e. whether arm movements can... more

Motion of the upper limbs is often coupled to that of the lower limbs in human bipedal locomotion. It is unclear, however, whether the functional coupling between upper and lower limbs is bi-directional, i.e. whether arm movements can affect the lumbosacral locomotor circuitry. Here we tested the effects of voluntary rhythmic arm movements on the lower limbs. Participants lay horizontally on their side with each leg suspended in an unloading exoskeleton. They moved their arms on an overhead treadmill as if they walked on their hands. Hand-walking in the antero-posterior direction resulted in significant locomotor-like movements of the legs in 58% of the participants. We further investigated quantitatively the responses in a subset of the responsive subjects. We found that the electromyographic (EMG) activity of proximal leg muscles was modulated over each cycle with a timing similar to that of normal locomotion. The frequency of kinematic and EMG oscillations in the legs typically differed from that of arm oscillations. The effect of hand-walking was direction specific since medio-lateral arm movements did not evoke appreciably leg air-stepping. Using externally imposed trunk movements and biomechanical modelling, we ruled out that the leg movements associated with hand-walking were mainly due to the mechanical transmission of trunk oscillations. EMG activity in hamstring muscles associated with hand-walking often continued when the leg movements were transiently blocked by the experimenter or following the termination of arm movements. The present results reinforce the idea that there exists a functional neural coupling between arm and legs.

Human locomotor movements exhibit considerable variability and are highly complex in terms of both neural activation and biomechanical output. The building blocks with which the central nervous system constructs these motor patterns can... more

Human locomotor movements exhibit considerable variability and are highly complex in terms of both neural activation and biomechanical output. The building blocks with which the central nervous system constructs these motor patterns can be preserved in patients with various sensory-motor disorders. In particular, several studies highlighted a modular burst-like organization of the muscle activity. Here we review and discuss this issue with a particular emphasis on the various examples of adaptation of locomotor patterns in patients (with large fiber neuropathy, amputees, stroke and spinal cord injury). The results highlight plasticity and different solutions to reorganize muscle patterns in both peripheral and central nervous system lesions. The findings are discussed in a general context of compensatory gait mechanisms, spatiotemporal architecture and modularity of the locomotor program.

An ability to produce rhythmic activity is ubiquitous for locomotor pattern generation and modulation. The role that the rhythmogenesis capacity of the spinal cord plays in injured populations has become an area of interest and systematic... more

An ability to produce rhythmic activity is ubiquitous for locomotor pattern generation and modulation. The role that the rhythmogenesis capacity of the spinal cord plays in injured populations has become an area of interest and systematic investigation among researchers in recent years, despite its importance being long recognized by neurophysiologists and clinicians. Given that each individual interneuron, as a rule, receives a broad convergence of various supraspinal and sensory inputs and may contribute to a vast repertoire of motor actions, the importance of assessing the functional state of the spinal locomotor circuits becomes increasingly evident. Air-stepping can be used as a unique and important model for investigating human rhythmogenesis since its manifestation is largely facilitated by a reduction of external resistance. This article aims to provide a review on current issues related to the " locomotor " state and interactions between spinal and supraspinal influences on the central pattern generator (CPG) circuitry in humans, which may be important for developing gait rehabilitation strategies in individuals with spinal cord and brain injuries.

An outstanding question in research of central pattern generators is whether CPGs can be used for whole body control of a robot. Given the spine's important role in walking, including a robotic spine may be a prerequisite for answering... more

An outstanding question in research of central pattern generators is whether CPGs can be used for whole body control of a robot. Given the spine's important role in walking, including a robotic spine may be a prerequisite for answering this question, but most current robots use rigid torsos.
Tensegrity offers exciting possibilities for future robotic structures, as their continuous tension networks automatically distribute forces. This property creates robust structures and shows the potential to improve torsos of legged robots, and may also provide mechanisms for distributed coordination of motor patterns and entrainment with oscillatory controllers such as CPGs. Our prior work with CPGs on tensegrity structures allowed for some adaptations in rough terrain, but without feedback success was limited with larger perturbations. This work demonstrates a CPG controlled tensegrity spine with locomotor capability on additional terrains by providing feedback to the CPG.

• Air-stepping can be used as a model for investigating rhythmogenesis/CPG in humans. • We compared voluntary and non-voluntary (vibration-induced) stepping. • We examined MEPs in response to TMS of the motor cortex and H-reflex. • We... more

• Air-stepping can be used as a model for investigating rhythmogenesis/CPG in humans. • We compared voluntary and non-voluntary (vibration-induced) stepping. • We examined MEPs in response to TMS of the motor cortex and H-reflex. • We found greater responsiveness to central/sensory inputs during voluntary stepping. • Findings support engagement of supraspinal motor areas in CPG-modulating therapies. a b s t r a c t Here, we compared motor evoked potentials (MEP) in response to transcranial magnetic stimulation of the motor cortex and the H-reflex during voluntary and vibration-induced air-stepping movements in humans. Both the MEPs (in mm biceps femoris, rectus femoris and tibialis anterior) and H-reflex (in m soleus) were significantly smaller during vibration-induced cyclic leg movements at matched amplitudes of angular motion and muscle activity. These findings highlight differences between voluntary and non-voluntary activation of the spinal pattern generator circuitry in humans, presumably due to an extra facilitatory effect of voluntary control/triggering of stepping on spinal motoneurons and interneurons. The results support the idea of active engagement of supraspinal motor areas in developing central pattern generator-modulating therapies.

We present a methodology enabled by the NASA Tensegrity Robotics Toolkit (NTRT) for the rapid structural design of tensegrity robots in simulation and an approach for developing control systems using central pattern generators, local... more

We present a methodology enabled by the NASA Tensegrity Robotics Toolkit (NTRT) for the rapid structural design of
tensegrity robots in simulation and an approach for developing control systems using central pattern generators, local impedance
controllers, and parameter optimization techniques to determine effective locomotion strategies for the robot. Biomimetic
tensegrity structures provide advantageous properties to robotic locomotion and manipulation tasks, such as their adaptability
and force distribution properties, flexibility, energy efficiency, and access to extreme terrains. While strides have been made in
designing insightful static biotensegrity structures, gaining a clear understanding of how a particular structure can efficiently
move has been an open problem. The tools in the NTRT enable the rapid exploration of the dynamics of a given morphology,
and the links between structure, controllability, and resulting gait efficiency. To highlight the effectiveness of the NTRT at this
exploration of morphology and control, we will provide examples from the designs and locomotion of four different modular
spine-like tensegrity robots.

Simulations performed with neuromechanical models are providing insight into the neural control of locomotion that would be hard if not impossible to obtain in any other way. We first discuss the known properties of the neural mechanisms... more

Simulations performed with neuromechanical models are providing insight into the neural control of locomotion that would be hard if not impossible to obtain in any other way. We first discuss the known properties of the neural mechanisms controlling locomotion, with a focus on mammalian systems. The rhythm-generating properties of central pattern generators (CPGs) are discussed in light of results indicating that cycle characteristics may be preset by tonic drive to spinal interneuronal networks. We then describe neuromechanical simulations that have revealed some basic rules of interaction between CPGs, sensory-mediated switching mechanisms and the biomechanics of locomotor movements. We posit that the spinal CPG timer and the sensory-mediated switch operate in parallel, the former being driven primarily by descending inputs and the latter by the kinematics. The CPG timer produces extensor and flexor phase durations, which covary along specific lines in a plot of phase- versus cycle-duration. We coined the term “phase-duration characteristics” to describe such plots. Descending input from higher centers adjusts the operating points on the phase-duration characteristics according to anticipated biomechanical requirements. In well-predicted movements, CPG-generated phase durations closely match those required by the kinematics, minimizing the corrections in phase duration required of the sensory switching mechanism. We propose the term “neuromechanical tuning” to describe this process of matching the CPG to the kinematics.

The revealed secrets of nature always led humans to their aspiring achievements. The fastest animal on land is Cheetah and similar robot has developed by engineers so far to attain a record speed of 20mph among legged robots. But in... more

The revealed secrets of nature always led humans to their aspiring achievements. The fastest animal on land is Cheetah and similar robot has developed by engineers so far to attain a record speed of 20mph among legged robots. But in nature there are some insects those are far ahead of cheetah in speed with a unit of body length per second. Insects are small in their body size with legs usually countable from 4 to 12 or more. With more legs they can have more stability and can adapt to different terrain faster while walking. Six legged robot (hexapod) is generally expect to attain higher speed in terms of body length per second, since the nature has proof for it. Bio-inspired Central Pattern Generator (CPG) is in use for so far in robotic world to mimic the locomotion patterns of insects and other animals. Currently the hybrid controller of CPG and reflex is going on and this paper suggests a new architecture for the system. Neural Network modeled CPG acts as the motor neuron for each joint of the leg. In each instant a neural network models the gait of the robot by learning procedure from the reflex system. This is like the Central Nervous System (CNS) selecting gait of an animal according to the terrain that travels. CNS takes sensory feedback from eyes, force on each leg and body balance from cochlea to adapt the gait for current terrain. This paper in first place tries to simulate the gait patterns for a hexapod.

Summary: Purpose: Nocturnal frontal lobe epilepsy (NFLE) is characterized by a wide spectrum of sleep-related motor manifestations of increasing complexity, ranging from major episodes to brief motor events (minor motor events, MMEs).... more

Summary: Purpose: Nocturnal frontal lobe epilepsy (NFLE) is characterized by a wide spectrum of sleep-related motor manifestations of increasing complexity, ranging from major episodes to brief motor events (minor motor events, MMEs). NFLE patients may exhibit a large quantity of MMEs in the form of short-lasting stereotyped movements. Whereas major episodes are considered epileptiform manifestations, it remains unclear whether the MMEs are related to epileptiform discharges (EDs).Methods: To study the relation between EDs and the occurrence of MMEs, we report a detailed neurophysiolgical evaluation in NFLE subjects explored by using implanted electrodes.Results: The median value of ED-related movements was 71.8%. Motor expression in relation to epileptiform discharge was surprisingly variable; no peculiar expression of MMEs could be attributed to the presence of EDs.Conclusions: Our data suggest that ED-associated MMEs are extremely polymorphous, and no univocal relation to EDs can be identified. We hypothesize that MMEs are not a direct effect of epileptiform discharge (i.e., not epileptic in origin), but the result of aspecific disinhibition of innate motor patterns. We warn clinicians that the epileptic nature of minimal motor phenomena in NFLE cannot be established on the clinical phenomenology of the event.

During human walking, there exists a functional neural coupling between arms and legs, and between cervical and lumbosacral pattern generators. Here, we present a novel approach for associating the electromyographic (EMG) activity from... more

During human walking, there exists a functional neural coupling between arms and legs, and between cervical and lumbosacral pattern generators. Here, we present a novel approach for associating the electromyographic (EMG) activity from upper limb muscles with leg kinematics. Our methodology takes advantage of the high involvement of shoulder muscles in most locomotor-related movements and of the natural coordination between arms and legs. Nine healthy subjects were asked to walk at different constant and variable speeds (3–5 km/h), while EMG activity of shoulder (deltoid) muscles and the kinematics of walking were recorded. To ensure a high level of EMG activity in deltoid, the subjects performed slightly larger arm swinging than they usually do. The temporal structure of the burst-like EMG activity was used to predict the spatiotemporal kinematic pattern of the forthcoming step. A comparison of actual and predicted stride leg kinematics showed a high degree of correspondence (r > 0.9). This algorithm has been also implemented in pilot experiments for controlling avatar walking in a virtual reality setup and an exoskeleton during over-ground stepping. The proposed approach may have important implications for the design of human–machine interfaces and neuroprosthetic technologies such as those of assistive lower limb exoskeletons.

Cheetahs and beetles run, dolphins and salmon swim, and bees and birds fly with grace and economy surpassing our technology. Evolution has shaped the breathtaking abilities of animals, leaving us the challenge of reconstructing their... more

Cheetahs and beetles run, dolphins and salmon swim, and bees and birds fly with grace and economy surpassing our technology. Evolution has shaped the breathtaking abilities of animals, leaving us the challenge of reconstructing their targets of control and mechanisms of dexterity. In this review we explore a corner of this fascinating world. We describe mathematical models for legged animal

We investigated whether dorsal (DR) and ventral root (VR) stimulus trains engage common postsynaptic components to activate the central pattern generator (CPG) for locomotion in the neonatal mouse spinal cord. VR stimulation did not... more

We investigated whether dorsal (DR) and ventral root (VR) stimulus trains engage common postsynaptic components to activate the central pattern generator (CPG) for locomotion in the neonatal mouse spinal cord. VR stimulation did not activate the first order interneurons mediating the activation of the locomotor CPG by sacrocaudal afferent stimulation. Simultaneous stimulation of adjacent dorsal or ventral root pairs, subthreshold for evoking locomotor-like activity, did not summate to activate the CPG. This suggests that locomotor-like activity is triggered when a critical class of efferent or afferent axons is stimulated and does not depend on the number of stimulated axons or activated postsynaptic neurons. DR-and VR-evoked episodes exhibited differences in the coupling between VR pairs. In DR-evoked episodes, the coupling between the ipsilateral and contralateral flexor/extensor roots was similar and stronger than the bilateral extensor roots. In VR-evoked episodes, ipsilateral flexor/extensor coupling was stronger than both the contralateral flexor/extensor and the bilateral extensor coupling. For both types of stimulation, the coupling was greatest between the bilateral L1/L2 flexor-dominated roots. This indicates that the recruitment and/or the firing pattern of motoneurons differed in DR and VR-evoked episodes. However, the DR and VR trains do not appear to activate distinct CPGs because trains of DR and VR stimuli at frequencies too low to evoke locomotor-like activity did so when they were interleaved. These results indicate that the excitatory actions of VR stimulation converge onto the CPG through an unknown pathway that is not captured by current models of the locomotor CPG.

The plasticity of the nervous system during the processing of sensory information is of major interest to interdisciplinary neurobiology research. Here, we used an insect model system with stereotyped behavioral patterns for the... more

The plasticity of the nervous system during the processing of sensory information is of major interest to interdisciplinary neurobiology research. Here, we used an insect model system with stereotyped behavioral patterns for the investigation of how the nervous system can switch between two different motor outputs, walking and standing, despite having the same sensory input, in a computer simulation based on the known network structure. The strengths of 16 specific information pathways which integrate sensory information were permutated and the resulting database of more than 43 million network outputs was analyzed. Two independent analysis show that the same neural network can produce two different behaviors by specifically altering the weighting of several information pathways. We obtained specific combinations of pathway transmission levels that produced these behaviors. This means, that solely changing the strength with which a pathway transmits sensory information is sufficient to switch between different behaviors, like from standing to walking. The predictions that derive from our results can now be used in physiological experiments.

An outstanding question in research of central pattern generators is whether CPGs can be used for whole body control of a robot. Given the spine’s important role in walking, including a robotic spine may be a prerequisite for answering... more

An outstanding question in research of central pattern generators is whether CPGs can be used for whole body control of a robot. Given the spine’s important role in walking, including a robotic spine may be a prerequisite for answering this question, but most current robots use rigid torsos. Tensegrity offers exciting possibilities for future robotic structures, as their continuous tension networks automatically distribute forces. This property creates robust structures and shows the potential to improve torsos of legged robots, and may also provide mechanisms for distributed coordination of motor patterns and entrainment with oscillatory controllers such as CPGs. Our prior work with CPGs on tensegrity structures allowed for some adaptations in rough terrain, but without feedback success was limited with larger perturbations. This work demonstrates a CPG controlled tensegrity spine with locomotor capability on additional terrains by providing feedback to the CPG.

Oscillating neuronal circuits, known as central pattern generators (CPGs), are responsible for generating rhythmic behaviours such as walking, breathing and chewing. The CPG model alone however does not account for the ability of animals... more

Oscillating neuronal circuits, known as central pattern generators (CPGs), are responsible for generating rhythmic behaviours such as walking, breathing and chewing. The CPG model alone however does not account for the ability of animals to adapt their future behaviour to changes in the sensory environment that signal reward. Here, using multi-electrode array (MEA) recording in an established experimental model of centrally generated rhythmic behaviour we show that the feeding CPG of Lymnaea stagnalis is ...

Abstract. A newborn foal can learn to walk soon after birth through a process of rapid adaptation acting on its locomotor controller. It is proposed here that this kind of adaptation can be modeled as a distributed system of adaptive... more

Abstract. A newborn foal can learn to walk soon after birth through a process of rapid adaptation acting on its locomotor controller. It is proposed here that this kind of adaptation can be modeled as a distributed system of adaptive modules (AMs) acting on a distributed system of ...

The effect of proprioceptive feedback on the control of posture and locomotion was studied in the crayfish Procambarus clarkii (Girard). Sensory and motor nerves of an isolated crayfish thoracic nerve cord were connected to a... more

The effect of proprioceptive feedback on the control of posture and locomotion was studied in the crayfish Procambarus clarkii (Girard). Sensory and motor nerves of an isolated crayfish thoracic nerve cord were connected to a computational neuromechanical model of the crayfish thorax and leg. Recorded levator (Lev) and depressor (Dep) nerve activity drove the model Lev and Dep muscles to move the leg up and down. These movements released and stretched a model stretch receptor, the coxobasal chordotonal organ (CBCO). Model CBCO length changes drove identical changes in the real CBCO; CBCO afferent responses completed the feedback loop. In a quiescent preparation, imposed model leg lifts evoked resistance reflexes in the Dep motor neurons that drove the leg back down. A muscarinic agonist, oxotremorine, induced an active state in which spontaneous Lev/Dep burst pairs occurred and an imposed leg lift excited a Lev assistance reflex followed by a Lev/Dep burst pair. When the feedback lo...

We present a methodology enabled by the NASA Tensegrity Robotics Toolkit (NTRT) for the rapid structural design of tensegrity robots in simulation and an approach for developing control systems using central pattern generators, local... more

We present a methodology enabled by the NASA Tensegrity Robotics Toolkit (NTRT) for the rapid structural design of tensegrity robots in simulation and an approach for developing control systems using central pattern generators, local impedance controllers, and parameter optimization techniques to determine effective locomotion strategies for the robot. Biomimetic tensegrity structures provide advantageous properties to robotic locomotion and manipulation tasks, such as their adaptability and force distribution properties, flexibility, energy efficiency, and access to extreme terrains. While strides have been made in designing insightful static biotensegrity structures, gaining a clear understanding of how a particular structure can efficiently move has been an open problem. The tools in the NTRT enable the rapid exploration of the dynamics of a given morphology, and the links between structure, controllability, and resulting gait efficiency. To highlight the effectiveness of the NTR...

The present discourse links the electrical and chemical properties of the brain with neurotransmitters and movement behaviors to further elucidate strategies to diagnose and treat brain disease. Neuromolecular imaging (NMI), based on... more

The present discourse links the electrical and chemical properties of the brain with neurotransmitters and movement behaviors to further elucidate strategies to diagnose and treat brain disease. Neuromolecular imaging (NMI), based on electrochemical principles, is used to detect serotonin in nerve terminals (dorsal and ventral striata) and somatodendrites (ventral tegmentum) of reward/motor mesocorticolimbic and nigrostriatal brain circuits. Neuronal release of serotonin is detected at the same time and in the same animal, freely moving and unrestrained, while open-field behaviors are monitored via infrared photobeams. The purpose is to emphasize the unique ability of NMI and the BRODERICK PROBE® biosensors to empirically image a pattern of temporal synchrony, previously reported, for example, in Aplysia using central pattern generators (CPGs), serotonin and cerebral peptide-2. Temporal synchrony is reviewed within the context of the literature on central pattern generators, neurotr...

Reorganizational Healing, (ROH), is an emerging wellness, growth and behavioral change paradigm. Through its three central elements (the Four Seasons of Wellbeing, the Triad of Change, and the Five Energetic In-telligences)... more

Reorganizational Healing, (ROH), is an emerging wellness, growth and behavioral change paradigm. Through its three central elements (the Four Seasons of Wellbeing, the Triad of Change, and the Five Energetic In-telligences) Reorganizational Healing takes an approach to help create a map for individuals to self-assess and draw on strengths to create sustainable change. Reorganizational Healing gives individuals concrete tools to explore and use the meanings of their symptoms, problems, and life-stressors as catalysts to taking new and sustained action to create a more fulfilling and resilient life.

Central pattern generators are neuron networks that produce vital rhythmic motor outputs such as those observed in mastication, walking and breathing. Their activity patterns depend on the tuning of their intrinsic ionic conductances,... more

Central pattern generators are neuron networks that produce vital rhythmic motor outputs such as those observed in mastication, walking and breathing. Their activity patterns depend on the tuning of their intrinsic ionic conductances, their synaptic interconnectivity and entrainment by extrinsic neurons. The influence of two commonly found synaptic connectivities--reciprocal inhibition and electrical coupling--are investigated here using a neuron model with subthreshold oscillation capability, in different firing and entrainment regimes. We study the dynamics displayed by a network of a pair of neurons with various firing regimes, coupled by either (i) only reciprocal inhibition or by (ii) electrical coupling first and then reciprocal inhibition. In both scenarios a range of coupling strengths for the reciprocal inhibition is tested, and in general the neuron with the lower firing rate stops spiking for strong enough inhibitory coupling, while the faster neuron remains active. Howev...

How sensory information influences the dynamics of rhythm generation varies across systems, and general principles for understanding this aspect of motor control are lacking. Determining the origin of respiratory rhythm generation is... more

How sensory information influences the dynamics of rhythm generation varies across systems, and general principles for understanding this aspect of motor control are lacking. Determining the origin of respiratory rhythm generation is challenging because the mechanisms in a central circuit considered in isolation may be different than those in the intact organism. We analyze a closed-loop respiratory control model incorporating a central pattern generator (CPG), the Butera-Rinzel-Smith (BRS) model, together with lung mechanics, oxygen handling, and chemosensory components. We show that: (1) Embedding the BRS model neuron in a control loop creates a bistable system; (2) Although closed-loop and open-loop (isolated) CPG systems both support eupnea-like bursting activity, they do so via distinct mechanisms; (3) Chemosensory feedback in the closed loop improves robustness to variable metabolic demand; (4) The BRS model conductances provide an autoresuscitation mechanism for recovery from...

The trace amines (TAs), tryptamine, tyramine, and β-phenylethylamine, are synthesized from precursor amino acids via aromatic-L-amino acid decarboxylase (AADC). We explored their role in the neuromodulation of neonatal rat spinal cord... more

The trace amines (TAs), tryptamine, tyramine, and β-phenylethylamine, are synthesized from precursor amino acids via aromatic-L-amino acid decarboxylase (AADC). We explored their role in the neuromodulation of neonatal rat spinal cord motor circuits. We first showed that the spinal cord contains the substrates for TA biosynthesis (AADC) and for receptor-mediated actions via trace amine-associated receptors (TAARs) 1 and 4. We next examined the actions of the TAs on motor activity using the in vitro isolated neonatal rat spinal cord. Tyramine and tryptamine most consistently increased motor activity with prominent direct actions on motoneurons. In the presence of N-methyl-D-aspartate, all applied TAs supported expression of a locomotor-like activity (LLA) that was indistinguishable from that ordinarily observed with serotonin, suggesting that the TAs act on common central pattern generating neurons. The TAs also generated distinctive complex rhythms characterized by episodic bouts of...