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  • 1
    Electronic Resource
    Electronic Resource
    The estimation of the frequency response function of a mechanoreceptor (1972)
    Springer
    Biological cybernetics 11 (1972), S. 15-23 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Widespread use has been made of linear systems theory to describe the input-output relations of receptors. The frequency response function of an insect mechanoreceptor, the tactile spine of the cockroach, has been estimated by using deterministic inputs (sines and step functions), deterministic inputs added to a stochastic, auxiliary signal (band-limited white noise), and a stochastic input alone. When a stochastic input is used, spectral analysis provides methods for estimating the coherence function as well as the frequency response function. The coherence function of the tactile spine is low, suggesting that the linear frequency response function is not a good characterization of the input-output relation of the receptor. Two non-linearities, rectification and phase-locking are described. Rectification can reduce the absolute value of the frequency response measured using sine waves of all frequencies without changing its form. Phase-locking changes the form of the frequency response function at high frequencies. Use of a stochastic auxiliary signal linearizes the input-output relations of the receptor in the sense that the cycle histograms obtained with sinusoidal inputs are more sinusoidal and the form of the frequency response function agrees with that predicted from the step response over a wider range of frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00267761
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  • 2
    Electronic Resource
    Electronic Resource
    Application of optimal multichannel filtering to simulated nerve signals (1979)
    Springer
    Biological cybernetics 32 (1979), S. 25-33 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The optimal linear filters derived in the preceding paper can be thoroughly evaluated using computer simulations, based on the properties of mammalian sensory and motor nerve fibres. Using reasonable values for action potential waveforms, conduction velocity and electrode noise, good separation of motor and sensory signals can be obtained. The performance of the filters is degraded by 1) increasing the electrode noise, 2) introducing dispersion in the conduction velocities, or 3) variation in the waveform of the action potentials from that used in designing the filters. However, the variations needed to seriously degrade performance are quite large compared to those which are likely to be present in mammalian nerves. Use of these filters to distinguish different classes of sensory (or motor) signals based on conduction velocity is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00337448
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  • 3
    Electronic Resource
    Electronic Resource
    Dynamics of a long-latency reflex pathway in the monkey (1979)
    Springer
    Biological cybernetics 34 (1979), S. 107-110 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Angular wrist displacements in the monkey result in a short-latency (20–25 ms) “reflex” response of motor cortical cells in area 4 and separate peaks of activity in the gross EMG of the stretched muscles. Frequency domain analysis was carried out between (1) wrist position as input and motor cortical neuron response as output, (2) position as input and EMG response as output, and (3) motor cortical neuron response as input and EMG response as output. The results show that the dynamics of primary spindle afferents characterize the dynamics of the pathway to the motor cortex and that of the reflex loop. Results are discussed in terms of “long-loop” reflexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365474
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  • 4
    Electronic Resource
    Electronic Resource
    Quantitative studies on the slowly adapting stretch receptor of the crayfish (1966)
    Springer
    Biological cybernetics 3 (1966), S. 175-185 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Summary In isolated receptors the impulse frequency following “step” stretches had a highly significant correlation with both muscle length and tension; any deviations from linearity were in opposite directions, impulse frequency rising more quickly than linearly with length and more slowly than linearly with tension. The impulse frequency decayed according to a power function of time from application of a step increase in length. A transfer function was derived and used to predict responses to sinusoidal and constant velocity stretches. The experimental data generally agreed with predictions. The deviations that were found could be accounted for by considering quantitatively any non-linearity between frequency and length, the adaptation of the impulse frequency to constant currents, the all-or-none nature of the action potential, and the viscous forces present during dynamic stretch. The approximately linear relationship between impulse frequency and muscle length and muscle tension is discussed. Muscle tension appears to be the more direct causal agent of impulse generation. Possible physical bases for the transfer function are also considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00290253
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  • 5
    Electronic Resource
    Electronic Resource
    Tremor and other oscillations in neuromuscular systems (1976)
    Springer
    Biological cybernetics 22 (1976), S. 147-157 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A model has been analyzed which is based on recent experimental evidence concerning the properties of muscles and the sensory feedback pathways from muscles. Damped oscillations can arise in the absence of sensory feedback due to the interaction of a muscle with inertial loads. These mechanical oscillations can have a wide range of frequencies depending on the inertial and elastic loads that are attached to the muscle. Small amounts of sensory feedback will tend to reduce deviations from a steady muscle length, but larger amounts of feedback can produce oscillations. The frequency of these reflex oscillations is determined by the properties of the muscle and feedback pathway, and is rather independent of load. If the strength of the sensory feedback is sufficient, either the mechanical oscillations or the reflex oscillations or both can grow, rather than decay, with time. The growth of these oscillations is limited by saturation non-linearities in the muscle receptors and the muscle itself, so that the oscillations approach a steady amplitude and frequency. Using typical properties of muscles and spinal reflex pathways, the frequency of reflex oscillations will be within the range 8–12 Hz found for physiological tremor. With the longer latency found for supraspinal reflexes, oscillations will occur in the range 4–6 Hz which is characteristic of Parkinson's and cerebellar diseases. The role of longer latency reflexes in the generation of these tremors is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365525
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  • 6
    Electronic Resource
    Electronic Resource
    Optimal filtering of nerve singnals (1977)
    Springer
    Biological cybernetics 27 (1977), S. 41-48 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Recording from multiple electrodes at different sites along a peripheral nerve permits the application of powerful filtering methods to extract the activity of populations of fibres within the nerve which differ in temporal or spectral characteristics. The design of optimal linear filters is initially treated as a general problem in the calculus of variations in which the signals from one population of nerve fibres are extracted so as to minimize those from a second population of nerve fibres or from other sources (noise). A particularly important application arises when the signals at two electrodes are related by weighting functions. In the simplest example the weighting function represents the time delay for nerve impulses to conduct from one electrode to the other, but explicit results are also derivable when there are a range of conduction delays with probabilities distributed according to well-known functions such as the sinc2 function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00357709
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  • 7
    Electronic Resource
    Electronic Resource
    Mathematical analysis of optimal multichannel filtering for nerve signals (1979)
    Springer
    Biological cybernetics 32 (1979), S. 19-24 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract This paper extends recent analyses (Roberts and Hartline, 1975; Oğuztöreli and Stein, 1977) of optimal linear filters for separating neural signals from more than one electrode site. Roberts and Hartline's result, using a matched filter criterion, represents one of a class of optimal filters with different, but symmetrical, output waveforms derived by Oğuztöreli and Stein (1977). Another narrow bandwidth filter of this class will give the optimal results according to an energy criterion, but may be less useful in practical situations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00337447
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  • 8
    Electronic Resource
    Electronic Resource
    Optimal control of antagonistic muscles (1983)
    Springer
    Biological cybernetics 48 (1983), S. 91-99 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Recently, a model for a pair of antogonistic muscles has been studied (Oğuztöreli and Stein, 1982). In the present paper we formulate and investigate the minimization of the costs associated with the time to complete the movement, the oscillation about the end-point, the energy costs to the muscles to complete the movement, the cost to the nervous system to supply the inputs, and the cost of reliability in the face of perturbing forces. To solve these optimization problems the maximum principle of Pontryagin is employed. In all of these optimization problems, except the energy optimal problem, the optimal controls (active states or nervous inputs) are of the bang-bang type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00344392
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  • 9
    Electronic Resource
    Electronic Resource
    Optimal task performance of antagonistic muscles (1990)
    Springer
    Biological cybernetics 64 (1990), S. 87-94 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Movements against a variety of loads are relatively invariant in form. These movements are controlled in general by antagonistic groups of muscles. In this paper optimal control strategies are computed for coupling antagonistic muscles so as to minimize deviations from a desired trajectory. Simulations are presented for linear and nonlinear “decision functions” linking control of the two muscles for a variety of movements in a way that may be compared with experimental observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02331337
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  • 10
    Electronic Resource
    Electronic Resource
    Predictions and ecperimental tests of a visco-elastic muscle model using elastic and inertial loads (1976)
    Springer
    Biological cybernetics 22 (1976), S. 139-145 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A simple, linear visco-elastic model of muscle is described which contains five parameters: a series and a parallel elasticity, a viscosity, and a magnitude and rate constant for the decay of the active state. The effects of adding springs in series with a muscle are predicted. The responses to random stimulus trains can be used to evaluate the parameters of the model. The effects of applying inertial loads to the muscle can also be predicted. These predictions are in good agreement with experimental observations on plantaris muscle of the cat. For example, damped oscillations of the predicted frequencies can be observed for various inertial loads. The gain of the frequency response falls off sharply (as the fourth power of frequency) at higher frequencies. However, responses to lower frequency signals, including most of the frequencies important for cyclic movements, are only slightly affected by a wide variation in inertial load.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365524
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