[The role of afferentation in the generation of walking movements].
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Animals↗
Biomedical subjects
A G Fel'dman
Publications and source records attributed to A G Fel'dman.
[Classification of the neurons of the lumbo-sacral region of the spinal cord in accordance with their discharge patterns during provoked locomotion].
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Animals↗
[Biomechanical characteristics of the wiping reflex cycle].
Multijoint goal-directed hindlimb movements in response to chemical stimulation delivered to different skin sites on the medial back surface (wiping reflex-WR) were filmed and analysed in spinal or intact frogs Rana temporaria. Each WR cycle was divisible into five phases (flexion, lifting, aiming, wiping and extension) usually separated from each other by postural interruptions. One or several of the phases might spontaneously be reduced or deleted at all (e. g. the extension phase), although the WR was still effective. Such a reduction was, as a rule, observed in intact frogs while spinal ones usually exhibited the maximum phase sequence. It is suggested that the central spinal generator of the WR is formed of separate functional blocks each of which specifies a certain interjoint coordination and brings the joints to the central-conditioned equilibrium positions.
Animals↗
[A wave nature of the central regulation of the trajectory of the articular angle in man].
It is supposed that muscles of a single joint are controlled by a wave propagation of excitation along a central line-ordered neuronal ensemble. The number of steady active output ensemble neurons increases with wave-front displacement and the neurons discretely contribute to the motor command that is defined in terms of shifts of the so-called invariant muscle force-length characteristics. The terminal position of the wave front is responsible for the final angular limb position, whereas the wave velocity responsible for the peak movement speed. To verify the wave model, human time-angle trajectories of rapid arm movements to different positions in the horizontal plane were analysed. The trajectories fall into groups having the following properties: 1) The initial profiles of the trajectories that belong to one group are identical; 2) the duration of the coincidence of any two grouped trajectories increases with their extent; 3) summation of two or more grouped trajectories with a certain time delay between them again gives a trajectory which belongs to the same group. The data obtained are in good agreement with the wave model.
Biomechanical Phenomena↗
[A model of central regulation of movement parameters].
The central processes responsible for a gradation of muscle torques or joint angles are suggested on the basis of the mass-spring hypothesis. Two fundamental commands (reciprocal and co- activative ) involved in the control over antagonist muscles are defined in terms of shifts of the so-called invariant characteristics (muscle torque vs joint angle). Each of the commands is graded by a neuronal ensemble arranged in line. Excitation propagates along the line at a centrally established rate. As the wave front moves, the output ensemble neurons are tonically recruited, and they discretely contribute to the respective command according to the superposition principle. The terminal position of the wave front of the reciprocal command is responsible for the final angular limb position, whereas the wave velocity--for the movement speed. The coactivation command just enhances muscle stiffness for a time of the movement. The theory presented is sufficiently well-defined to yield a variety of specific and testable predictions. After insignificant modifications the theory may be referred to the generation of the eye and head movements, both slow and fast ones.
Humans↗
[Locomotion of Barents Sea ophiuroids].
Locomotion of 5 species of Ophiuroids from the Barents Sea has been described--Ophiura albida, O. robusta, O. sarsi, Ophiacantha bidentata, Ophiopholis aculeata. Representatives from the genus Ophiura move by means of one or two symmertic pairs of arms which perform rhythmic rowing beats. The feet tube do not participate in their locomotion. Locomotion pattern in O. bidentata and especially O. aculeata, which have long flexible arms, is more complex. However, the analysis indicates that they replace themselves by a comparatiely limited set of standard "programmed" movements which may be used in various combinations. In locomotion of these species, the tube feet are involved which provide for the reliable contact of distal ends of the active rays with the supporting surface; due to this contact the animals can move in a straightforward direction.
Animals↗
[Turning over in the ophiuroid Amphipholis kochii].
The reaction of turning over in the ophiuroid A. kochii Lütken begins when the ambulacral legs are detached from the substrate. At the bottom, when aboral side of the animal touches the substrate, turning over begins with oral flexion of three arms. In water, turning over begins with aboral flexion of all the arms. The organism takes the shape of a ball, its center of gravity being shifted to the side of a disc which outer surface is formed by the oral part. As a result, when dropped into the water with its oral side upwards, the ophiuroid passively turns over due to the gravity force. Single arm isolated together with the adjacent part of the nervous ring is capable of turning over. After sectioning the nervous ring, coordinated activity of the arms during turning over is disturbed.
Animals↗
[Moments in human leg joints during walking].
An automated method is developed to obtain the moments of internal forces in the leg joints during walking. A considerable variability of joints moments is observed, which sufficiently exceeds that of the kinematic parameters of walking. For normal walking three different types of joints moments can be distinguished. The formal foundation for the variability of the moments is given, and a hypothesis is proposed, according to which the variability is associated with the keeping of equilibrium.
Ankle Joint↗