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Pattern Generators (pattern + generators)
Kinds of Pattern Generators Selected AbstractsThe role of inhibitory neurotransmission in locomotor circuits of the developing mammalian spinal cordACTA PHYSIOLOGICA, Issue 2 2009H. Nishimaru Abstract Neuronal circuits generating the basic coordinated limb movements during walking of terrestrial mammals are localized in the spinal cord. In these neuronal circuits, called central pattern generators (CPGs), inhibitory synaptic transmission plays a crucial part. Inhibitory synaptic transmission mediated by glycine and GABA is thought to be essential in coordinated activation of muscles during locomotion, in particular, controlling temporal and spatial activation patterns of muscles of each joint of each limb on the left and right side of the body. Inhibition is involved in other aspects of locomotion such as control of speed and stability of the rhythm. However, the precise roles of neurotransmitters and their receptors mediating inhibitory synaptic transmission in mammalian spinal CPGs remain unclear. Moreover, many of the inhibitory interneurones essential for output pattern of the CPG are yet to be identified. In this review, recent advances on these issues, mainly from studies in the developing rodent spinal cord utilizing electrophysiology, molecular and genetic approaches are discussed. [source] Xenopus embryonic spinal neurons recorded in situ with patch-clamp electrodes , conditional oscillators after all?EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2003Simon P. Aiken Abstract The central pattern generator for swimming Xenopus embryo is organized as two half-centres linked by reciprocal inhibition. Microelectrode recordings suggest that Xenopus neurons are poorly excitable, necessitating a key role for postinhibitory rebound in the operation of the central pattern generator. However the Xenopus central pattern generator seems unusual in that the component neurons apparently have no intrinsic or conditional rhythmogenic properties. We have re-examined the firing properties of Xenopus embryo spinal neurons by making patch-clamp recordings in situ from intact spinal cord. Recordings made from 99 neurons were divided into three groups. Central pattern generator neurons overwhelmingly (44/51) fired trains of action potentials in response to current injection. Just over half of the sensory interneurons (13/22) also fired trains of action potentials. Neurons that received no synaptic inputs during swimming mostly fired just one or two action potentials (22/26). Thirty-four neurons were identified morphologically. Commissural (8/12) and descending (6/6) interneurons, key components of the spinal central pattern generator, fired repetitive trains of action potentials during current injection. Neurons that were not part of the central pattern generator did not demonstrate this preponderance for repetitive firing. Analysis of the interspike intervals during current injection revealed that the majority of central pattern generators, descending and commissural interneurons, could readily fire at frequencies up to twice that of swimming. We suggest that Xenopus neurons can be considered as conditional oscillators: in the presence of unpatterned excitation they exhibit an ability to fire rhythmically. This property makes the Xenopus embryonic central pattern generator more similar to other model central pattern generators than has hitherto been appreciated. [source] The generation of rhythmic activity in dissociated cultures of rat spinal cordEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2001Jürg Streit Abstract Locomotion in vertebrates is controlled by central pattern generators in the spinal cord. The roles of specific network architecture and neuronal properties in rhythm generation by such spinal networks are not fully understood. We have used multisite recording from dissociated cultures of embryonic rat spinal cord grown on multielectrode arrays to investigate the patterns of spontaneous activity in randomised spinal networks. We were able to induce similar patterns of rhythmic activity in dissociated cultures as in slice cultures, although not with the same reliability and not always with the same protocols. The most reliable rhythmic activity was induced when a partial disinhibition of the network was combined with an increase in neuronal excitability, suggesting that both recurrent synaptic excitation and neuronal excitability contribute to rhythmogenesis. During rhythmic activity, bursts started at several sites and propagated in variable ways. However, the predominant propagation patterns were independent of the protocol used to induce rhythmic activity. When synaptic transmission was blocked by CNQX, APV, strychnine and bicuculline, asynchronous low-rate activity persisted at ,,50% of the electrodes and ,,70% of the sites of burst initiation. Following the bursts, the activity in the interval was transiently suppressed below the level of intrinsic activity. The degree of suppression was proportional to the amount of activity in the preceding burst. From these findings we conclude that rhythmic activity in spinal cultures is controlled by the interplay of intrinsic neuronal activity and recurrent excitation in neuronal networks without the need for a specific architecture. [source] Multi-template approach to realize central pattern generators for artificial locomotion controlINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 4 2002Paolo Arena Abstract Biologically inspired control of artificial locomotion often makes use of the concept of central pattern generator (CPG), a network of neurons establishing the locomotion pattern within a lattice of neural activity. In this paper a new approach, based on cellular neural networks (CNNs), for the design of CPGs is presented. From a biological point of view this new approach includes an approximated chemical synapse realized and implemented in a CNN structure. This allows to extend the results, previously obtained with a reaction-diffusion-CNN (RD-CNN) for the locomotion control of a hexapod robot, to a more general class of artificial CPGs in which the desired locomotion pattern and the switching among patterns are realized by means of a spatio-temporal algorithm implemented in the same CNN structure. Copyright © 2002 John Wiley & Sons, Ltd. [source] Stages 1,2 non,rapid eye movement sleep behavior disorder associated with dementia: A new parasomnia?MOVEMENT DISORDERS, Issue 9 2005Isabelle Arnulf MD Abstract A 55-year-old woman with a progressive dementia and frontal syndrome was hospitalized because she was agitated every night after falling asleep (spoke, laughed, cried, tapped, kicked, walked, and fell down). She slept 5.5 hours during video polysomnography, but the theta rhythm electroencephalograph recording typical of sleep stages 1 to 2 and the spindles and K-complexes typical of sleep stage 2 contrasted with continuous muscular twitching, prominent rapid eye movements, vocalizations, and continuous, complex, purposeful movements typical of rapid eye movement (REM) sleep behavior disorder. This newly described stages 1,2 non-REM sleep behavior disorder suggests that central motor pattern generators were disinhibited during non-REM sleep. © 2005 Movement Disorder Society [source] | ||||||||||