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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of computational neuroscience 5 (1998), S. 267-284 
    ISSN: 1573-6873
    Keywords: central pattern generator ; lamprey ; regeneration ; stochastic inference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine , Physics
    Notes: Abstract We present a simple stochastic model of two coupled phase oscillators and a method of fitting the model to experimental spike-train data or to sequences of burst times. We apply the method to data from lesioned isolated lamprey spinal cords. The remaining tracts at the lesion site are either regenerated medial tracts, regenerated lateral tracts, control medial tracts, or control lateral tracts. We show that regenerated tracts on average provide significantly weaker coupling than control tracts. We compare our model-dependent estimate of coupling strength to a measure of coordination based on the size of deflections in the spike-train cross-correlation histogram (CCH). Using simulated data, we show that our estimates are able to detect changes in coupling strength that do not change the size of deflections in the CCH. Our estimates are also more resistant to changes in the level of dynamic noise and to changes in relative oscillator frequency than is the CCH. In simulations with high levels of dynamic noise and in one experimental preparation, we are able detect significant coupling strength although there are no significant deflections in the CCH.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Autonomous robots 7 (1999), S. 239-245 
    ISSN: 1573-7527
    Keywords: locomotion ; sensory feedback ; central pattern generator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Rhythmic movements in biological systems are produced in part by central circuits called central pattern generators (CPGs). For example, locomotion in vertebrates derives from the spinal CPG with activity initiated by the brain and controlled by sensory feedback. Sensory feedback is traditionally viewed as controlling CPGs cycle by cycle, with the brain commanding movements on a top down basis. We present an alternative view which in sensory feedback alters the properties of the CPG on a fast as well as a slow time scale. The CPG, in turn, provides feedforward filtering of the sensory feedback. This bidirectional interaction is widespread across animals, suggesting it is a common feature of motor systems, and, therefore, might offer a new way to view sensorimotor interactions in all systems including robotic systems. Bidirectional interactions are also apparent between the cerebral cortex and the CPG. The motor cortex doesn't simply command muscle contractions, but rather operates with the CPG to produce adaptively structured movements. To facilitate these adaptive interactions, the motor cortex receives feedback from the CPG that creates a temporal activity pattern mirroring the spinal motor output during locomotion. Thus, the activity of the motor cortical cells is shaped by the spinal pattern generator as they drive motor commands. These common features of CPG structure and function are suggested as offering a new perspective for building robotic systems. CPGs offer a potential for adaptive control, especially when combined with the principles of sensorimotor integration described here.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 160 (1987), S. 181-193 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the lamprey,Ichthyomyzon unicuspis, the wave of activity required for normal swimming movements can be generated by a central pattern generator (CPG) residing in the spinal cord. A constant phase coupling between spinal segments can be organized by intersegmental coordinating neurons intrinsic to the cord. The rostral and caudal segmental oscillators of the CPG have different preferred frequencies when separated from each other. Therefore the system must maintain the segmental oscillators of the locomotor CPG at a single common frequency and with the proper relative timing. Using selective lesions and a split-bath, it is demonstrated that the coordinating system is comprised of at least 3 subsystems, short-axon systems in the lateral and medial tracts and a long axon system in the lateral tracts. Each alone can sustain relatively stable coordinated activity.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1416
    Keywords: Locomotion ; Pattern generator ; Dynamical systems ; Oscillators
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We present a theoretical model which is used to explain the intersegmental coordination of the neural networks responsible for generating locomotion in the isolated spinal cord of lamprey. A simplified mathematical model of a limit cycle oscillator is presented which consists of only a single dependent variable, the phase θ(t). By coupling N such oscillators together we are able to generate stable phase locked motions which correspond to traveling waves in the spinal cord, thus simulating “fictive swimming”. We are also able to generate irregular “drifting” motions which are compared to the experimental data obtained from cords with selective surgical lesions.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 97 (1992), S. 511-516 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Using a monoclonal antibody for glutamate the distribution was determined of glutamate-like immunoreactive neurons in the leech central nervous system (CNS). Glutamate-like immunoreactive neurons (GINs) were found to be localized to the anterior portion of the leech CNS: in the first segmental ganglion and in the subesophageal ganglion. Exactly five pairs of GINs consistently reacted with the glutamate antibody. Two medial pairs of GINs were located in the subesophageal ganglion and shared several morphological characteristics with two medial pairs of GINs in the first segmental ganglion. An additional lateral pair of GINs was also located in segmental ganglion 1. A pair of glutamate-like immunoreactive neurons, which are potential homologs of the lateral pair of GINs in segmental ganglion 1, were occasionally observed in more posterior segmental ganglia along with a selective group of neuronal processes. Thus only a small, localized population of neurons in the leech CNS appears to use glutamate as their neurotransmitter.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Footfall patterns and time sequence of activity are described for white rats conditioned to run freely in an activity wheel (which they drive). Motion is described in terms of soft contact, hard contact, soft contact, and flip phases. Duration of stride decreases and length of stride increases from walk to trot to canter to gallop. Myographic analysis shows that the brachialis has a major tonic function after it fires strongly during the flip phase and during much of the hard contact phase. Animals running at canter or gallop show major asymmetries between forelimb muscles on the first paw and on the lead paw sides.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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