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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 89 (1992), S. 147-156 
    ISSN: 1432-1106
    Keywords: Walking ; Interlimb coordination ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary On the basis of behavioural studies the influences that coordinate the movement of the legs of a slowly walking cat have been investigated. The recording method applied here allows for the measurement of forward and backward movement of the legs which are called swing and stance movements, respectively. Influences etween contralateral legs, i.e. both front legs or both hind legs, are stronger than those occurring between ipsilateral legs, i.e. front and hind leg of the same side. Influences which coordinate the front legs seem to be of the same kind as those for the hind legs. These influences are symmetrical, which means that the same type of influence acts from right to left leg and in the reverse direction. Two types of influences are described for contralateral legs: 1. When the influencing leg performs a swing movement, the influenced leg is prevented from starting a swing movement. 2. When the influencing leg performs a stance movement, the probability that the influenced leg starts a swing movement increases as the influencing leg moves backwards during its stance movement. In contrast to contralateral coupling, the ipsilateral influences are asymmetric, i.e. a different influence acts from front to hind leg than does in the reverse direction. The front leg is influenced to start a swing when both legs have approached each other to a given value. The hind leg is influenced to start a stance movement after the front leg has begun its swing.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 11 (1972), S. 185-200 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract 1. Form discrimination by honeybees can be measured when individuals are trained to select a rewarded shape in preference to other, unrewarded ones (Table 2). In these experiments, the values of discrimination for some pairs of shapes depend upon which of the pair is rewarded (“symmetrical, asymmetrical discrimination”, Table 3, 4). 2. Two groups of possible mechanisms of form discrimination will be discussed. Experimental findings preclude the exclusive use by the bees of any one of those mechanisms. The following discrimination function, however, describes the present as well as previously reported results: $$U = \left| {C_{\text{1}} \frac{{R^ + + R^ - }}{G}F^ + + C_2 {\text{(log}}K^ + {\text{ - log}}K^ - {\text{)}}} \right|$$ (Figs. 4, 5, 7, 8, 9, 10). R +, R −, G and F + are parts of areas (Fig. 1), K + and K − contour lengths of the shapes to be compared. 3. The weighting factors, C 1 and C 2, are apparently given different values by the bee for different shape combinations. Some results might support Mazochin-Porshnyakov's (1969) hypothesis that bees can also recognize other features of the shapes, according to the problem to be solved (Sect. D).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 37 (1980), S. 131-136 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A quantitative hypothesis is presented modelling the neuromuscular subsystem which controls the walking movements of a single leg of an insect. The model shown how central and peripheral influences can act together to produce walking movements. The subsystem of one leg consists of a central part producing reference input for a negative feedback loop which controls the position of the leg. The means by which the peripheral signals influence the central part of the model is constructed so that intact sense organs play the decisive role in controlling the walking rhythm of the leg. However, the rhythm can be produced by the control part alone, acting as a safety device if sense organs are destroyed. Using this model a series of experimental results obtained by several authors can be described.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 32 (1979), S. 107-113 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A computer (Fortran) model is proposed that describes the temporal and spatial coordination pattern of straight walking stick insects (Carausius morosus) for a broad speed range. It provides a stable pattern independent of the different starting positions. The model is based on six relaxation oscillators. The leading oscillator corresponds to a frontleg. Therefore the information flow runs from front to rear in contrast to earlier models (Graham, 1972; Wendler, 1968).
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 37 (1980), S. 137-144 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Using the experimental results of Cruse and Saxler (1980a, b) and other authors (Graham, 1972; Pearson, 1972; Bässler, 1977, 1979) a quantitative model is developed in order to describe the behaviour of the systems controlling the leg movements of a walking insect. The whole model consists of six subsystems each of which controls the movement of an individual leg. The single subsystem (Fig. 1) consists of a central part which can assume two modes (protraction, retraction) the transition between which can be controlled by sensory influence. The central part produces the reference input for a feedback loop which controls the leg position. The reference input is however also determined by influences from other subsystems. Four different types of such connections are assumed to exist between the subsystems. Two of these produce alternating (t1, t3), two others “in phase” coupling (t2, t4) between the subsystems to be connected. These connections can transfer information originating from the central part as well as from the periphery of other subsystems. The model is capable of describing either quantitatively or qualitatively the experimental results of Cruse and Saxler (1980a, b) (see Figs. 3 and 4). In addition it is capable of describing the results of other authors, e.g. the temporal leg coordination of the free walking animal (Graham, 1972).
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 36 (1980), S. 159-163 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract In the experiments presented here adult stick insects (Carausius morosus) walk on a treadwheel with various legs standing on platforms fixed relative to the body of the insect. These standing legs produce large forees directed towards the rear which are modulated in the rhythm of the walking legs. Neighbouring legs which both stand on a platform often oscillate “in phase”. Possible reasons for the occurrence of the force oscillations are discussed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 62 (1990), S. 519-528 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The aim of our investigation is to understand the mechanisms which control the movement of the human arm. The arm is here considered as a redundant system: the shoulder, elbow and wrist joints, which provide three degrees of freedom, combine to move the hand in a horizontal plane, i.e. a two dimensional space. Thus the system has one extra degree of freedom. Earlier investigations of the static situation led to the hypothesis that independent cost functions were attached to each of the three joints and that the configuration chosen for a given target position is that which provides the minimum total cost (Cruse 1986). The aim of the current investigation was to look for measurable values corresponding to the hypothetical cost functions. Experiments using pointers of different lengths attached to the hand showed that the strategy in choosing the joint angles are independent of the limb length. The muscle force necessary to reach a given angle is increased by a spring mounted across a joint. In this situation the angles of the loaded joint are changed for a given target point to give way to the force effect. This leads to the conclusion that the hypothetical cost functions are not independent of the physiological costs necessary to hold the joint at a given angle. The cost functions seem to depend on joint angle and on the force which is necessary to hold the joint in a given position. Cost functions are measured by psychophysical methods. The results showU-shaped curves which can be approximated by parabolas. The position of minimum cost (maximum comfort) for one joint showed no or weak dependency on the angles of the other joints. For each subject these “psychophysical” cost functions are compared with the hypothetical cost functions. The comparison showed reasonable agreement. This supports the assumption that the psychophysically measured “comfort functions” provide a measure for the hypothetical cost functions postulated to explain the targeting movements. Targeting experiments using a four joint arm which has two extra degrees of freedom showed a much larger scatter compared to the three joint arm. Nevertheless, the results still conform to the hypothesis that also in this case the minimum cost principle is applied to solve the redundancy problem. As the cost function for the whole arm shows a large minimum valley, quite a large range of arm positions is possible of about equal total costs. The scatter does not result from pure randomness but seems to be mainly produced by the fact that the angles at the end of the movement depend on the value of the joint angles at the beginning of the movement.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 62 (1990), S. 549-555 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract In an earlier investigation (Cruse and Brüwer 1987) an algorithmic model was proposed which describes targeting movements of a human arm when restricted to a horizontal plane. As three joints at shoulder, elbow and wrist are allowed to move, the system is redundant. Two models are discussed here which replace this algorithmic model by a network model. Both networks solve the static problem, i.e. they provide the joint angles which the arm has to adopt in order to reach a given point in the workspace. In the first model the position of this point is given in the form ofx —y coordinates, the second model obtains this information by means of a retina-like input layer. The second model is expanded by a simple procedure to describe movements from a start to an end point. The results qualitatively correspond to those obtained from human subjects. The advantages of the network models in comparison to the algorithmic model are discussed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 72 (1995), S. 421-430 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A system that controls the leg movement of an animal or a robot walking over irregular ground has to ensure stable support for the body and at the same time propel it forward. To do so, it has to react adaptively to unpredictable features of the environment. As part of our study of the underlying mechanisms, we present here a model for the control of the leg movement of a 6-legged walking system. The model is based on biological data obtained from the stick insect. It represents a combined treatment of realistic kinematics and biologically motivated, adaptive gait generation. The model extends a previous algorithmic model by substituting simple networks of artificial neurons for the algorithms previously used to control leg state and interleg coordination. Each system controlling an individual leg consists of three subnets. A hierarchically superior net contains two sensory and two ‘premotor’ units; it rhythmically suppresses the out-put of one or the other of the two subordinate nets. These are continuously active. They might be called the ‘swing module’ and the ‘stance module’ because they are responsible for controlling the swing (return stroke) and the stance (power stroke) movements, respectively. The swing module consists of three motor units and seven sensory units. It can produce appropriate return stroke movements for a broad range of initial and final positions, can cope with mechanical disturbances of the leg movement, and is able to react to an obstacle which hinders the normal performance of the swing movement. The complete model is able to walk at different speeds over irregular surfaces. The control system rapidly reestablishes a stable gait when the movement of the legs is disturbed.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract In the legs of the stick insect Carausius morosus a feedback mechanism exists to control the value of the angle between femur and tibia. It is possible to investigate the open loop system by moving as input experimentally the receptor apodeme of the femoral chordotonal organ, which acts as feedback transducer measuring the angle between femur and tibia (Bässler, 1965). As output the forces are measured separately which are developed by the two antagonistic muscles moving the femur-tibia joint. The response of this system to different step-, sine-, ramp-and δ-functions are measured. An electronic analog model is constructed to simulate the biological system (Fig. 1). Although a number of different nonlinearities arise in the biological system, as a first-order approximation the model shows a sufficient fit to the experimental results (Figs. 2–9). The main characteristics of the model are as follows. It consists of two independent subsystems, the “flexor system” and the “extensor system”. Each subsystem again consists of two parallel branches with high-pass properties of different time constants. In each subsystem one branch is only excitable by input functions of a slope smaller than a certain degree. It is remarkable, that no mutual inhibitory influence between the sub-systems controlling the antagonistic muscles is necessary in the model.
    Type of Medium: Electronic Resource
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