Recording of scratch generator efferent activity produced by cyclic hindlimb movement in decerebrate immobilized cat

The effects were observed on spinal scratch generator activity of the afferent inflow produced in decerebrate immobilized cat by regular passive movement of the hindlimb paw following a trajectory close to that observed during actual scratching. These consisted of substantial alteration in scratch generator efferent activity, which thereby became phase-locked with the afferent flow. Synchronization between efferent scratching activity and passive limb motion has occurred by the first movement cycle and phase-locking was the reverse of that seen during actual scratching.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 4, pp. 443–449, July–August, 1987.     

Alterations produced in the quantitative characteristics of efferent activity parameters of the locomotor generator by decerebellation

Changes in the parameters of activity in hindlimb locomotor generators following decerebellation were quantified during experiments on decerebrate immobilized cats. Eliminating modulating cerebellar influences on nuclei of descending systems was found to lead to a slight increase in the length of activity in the flexor generator half-center and less intensive activity, as well as shortening of the period and more intensive activity in the extensor half-center, together with increased instability in generator operation, reduced statistical dependence between alterations in parameters of activity at the hindlimb half-center generators, and finally intensified effects of afferent inputs on generator activity. A comparison is drawn between the functional role of the spino-cerebellar loop in the operation of locomotor and scratch generators.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 2, pp. 142–150, March–April, 1991.     

Reorganization of the efferent activity of the locomotor generator controlling forelimb movements for electrical stimulation of the descending systems

The reorganization of the parameters of the efferent activity of the forelimb locomotion generator for electrical stimulation of the descending systems is determined in experiments on decerebrate immobilized cats. This generator is found to be characterized by a stable state at which the sum of influences of the signals from different descending systems on the generator is extremely limited. It is concluded that under the influence of these signals, the reorganizations of the activity of the locomotion generators of different limbs bring the motor program into a dynamic (or nearly dynamic) relationship with the supraspinal inflow, allowing for a sufficient limitation and balancing of the influences of the corresponding descending systems on the interneuronal networks determining the temporal and phase characteristics of the activity of these generators.A. A. Bogomolets Institute of Physiology, Ukrainian Academy of Sciences, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 6, pp. 704–708, November–December, 1991.     

Rearrangement of parameters of efferent activity in generators of cyclic motor response produced by electrical stimulation of cerebellar inputs in cats

Rearrangement of the parameters of scratch and locomotor generators produced by electrical stimulation of the inferior olive and nucleus reticularis lateralis as well as the cerebellar fastigial nucleus and nucleus interpositus was investigated in decerebrate immobilized cats. Results showed that a comparable rearrangement of the time course of activity in both locomotor and scratch generators was produced by altering the nature of signals proceeding along mossy and climbing fibers alike. Maximum rearrangement of scratch and locomotor generator activity, as induced by electrical activation of the inferior olive and lateral reticular nucleus, is observed during the first half of flexor half-center operation in these generators. The scratch (unlike the locomotor) generator typically shows considerably rearranged efferent activity following electrical activation of nuclei of the cerebellum and cerebellar afferents. The article discusses mechanisms of cerebellar origin which may be responsible for exerting a corrective action on scratch and locomotor generators during change in the phase and amplitude parameters of cerebellar input signals.A. A. Bogomolets Institute of Physiology, Ukrainian Academy of Sciences, Kiev. Translated from Neirofiziologiya, Vol. 24, No. 2, pp. 131–140, March–April, 1992.     

Reordering of scratch generator efferent activity produced by stimulating hindlimb skin afferents in decerebrate immobilized cat

Reordering of the parameters of motor activity produced in the scratch generator by regular electrical stimulation of the ipsilateral hindlimb muscle nerve during different limb positions was investigated in decerebrate immobilized cats. Brief short latency inhibition of currently occurring motor activity was produced in response to stimulation, which did not cause an overall shift in the relationship between the intensity of aiming and scratching motion. Changes in cycle duration and intensity of these activities were phase-locked. Speculations were made on the functional role of the phase-locked nature of motor activity remodeling. The possible existence within the scratch generator of a model of the afferent inflow entering the spinal cord during true scratching is suggested.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 3, pp. 382–390, May–June, 1987.     

Analysis of the mechanisms of interaction between generators of cyclic motor reactions and inputs from suprasegmental systems

The simulation mathematical model of neuronal generator systems was used for analyzing the interaction between inputs from descending (afferent) systems and generators of scratching (locomotion). The data obtained indicate that in cases when generators of cyclic motor reactions influence the effectiveness of synaptic transmission from the fibers of descending (or afferent) systems, the differences in the main characteristics of signals that are produced by these generators themselves and those that come to them are emphasized. These data allow us to conclude that the system supplying interaction between inputs from suprasegmental (afferent) fiber systems and generators of locomotion of scratching can be interpreted as an adaptive filter which processes spatial and temporal information coming to the spinal cord via different suprasegmental or primary afferent inputs and allows generators of cyclic motor reactions to correct their functioning in accordance with changing external conditions.Neirofiziologiya/Neurophysiology, Vol. 25, No. 3, pp. 211–215, May–June, 1993.     

Rearrangement of scratch generator efferent activity during electrical activation of descending systems

Effects of signals proceeding along descending pathways on parameters of scratch generator activity were investigated in decerebrate immobilized cats. Certain phase-linked alterations in these parameters were shown to occur under the effects of electrical activation of the main descending systems. The biggest increase in scratch cycle duration under electrical stimulation of Deiter's nucleus, the red nucleus, and pyramidal tract is produced when stimuli are applied during the first half of the aiming stage. Stimulation during the second half of the aiming phase and at the start of the scratching movement hardly affect the scratching cycle. The main increase in length of scratch cycle during electrical stimulation of the reticular gigantocellularis nucleus is noted when stimuli are presented during the second half of the aiming stage. Electrical activation of descending pathways during the latter induces a rise in intensity in this phase and reduced intensity of the actual scratching stage. Activation of the pathways during this scratching motion causes heightened intensity of the motion while hardly affecting intensity of the aiming phase. The principles of suprasegmental rectification of scratch generator operation are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 3, pp. 300–309, May–June, 1990.     

Possible organization pattern of interaction between the generators of cyclic motor activity and inputs from supraspinal and afferent systems

Possible organization patterns of scratching and locomotor generators that allow interpretation of experimentally demonstrated reorganizations in temporal parameters of these generator activities after electrical stimulation of descending and peripheral afferent systems were analyzed with application of mathematical simulation of neuronal generator systems. The results obtained led to the conclusion that patterns of such reorganizations influenced by signals from suprasegmental and/or peripheral systems may be determined by only two factors: 1) the structure of synaptic connections between interneuronal functional groups underlying these generator associations, and 2) the structure of connections between these groups of interneurons and fibers from suprasegmental and peripheral afferent sources. The existence of inhibitory-excitatory actions from descending and afferent systems upon the neurons of locomotor or scratching generator half-centers is a sufficient condition to ensure phasic changes in the sensitivity of these generators to supraspinal and afferent signals. The locomotor generator, unlike the scratching generator, is apparently characterized by a more complex organization of connections between functional neuronal groupings and descending fibers.Translated from Neirofiziologiya, Vol. 25, No. 1, pp. 45–50, January–February, 1993.     

Correlation between the kinematics of hindlimb movement and efferent activity in the decerebrate cat during scratching

The statistical relationship was investigated between temporal and amplitude parameters of scratching motion performed by the hindlimb and those of muscular activity during naturally-occurring scratching in the course of experiments on decerebrate cats. The factors mainly determining movement parameters, such as amplitude or the speed and duration of a specific phase were found to be the intensity of EMG activity displayed by scratching and aiming muscles and the duration of aiming muscle activity. Findings from experiments involving limb deafferentation showed that the statistical relationship between the parameters of motion and muscular electrical activity reflect certain patterns of scratch generator operation. Certain relationships linking parameters of electrical activity changed due to the effects of afferent signals.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 4, pp. 525–533, July–August.     

Polarization of primary afferent terminals in the lumbar spinal cord during fictitious locomotion

Changes in electrical polarization of primary afferent terminals in the lumbosacral portion of the spinal cord were investigated during fictitious locomotion in immobilized decorticated and spinal cats. Fictitious locomotion was accompanied by stable hyperpolarization of the afferent terminals, against the background of which they were periodically depolarized in rhythm with efferent activity. These tonic and phasic changes were observed in terminals of all groups of afferent fibers tested: cutaneous and muscular (Ia and Ib). Periodic in-phase depolarization was carried out in different ipsilateral segments of the lumbosacral enlargement. During ficitious galloping changes in depolarization of the primary efferents were in phase on different sides; during fictitious walking, these periodic changes were out of phase. On the basis of these results the physiological importance of changes in electrical polarization of primary afferent terminals of the spinal locomotor generator is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 5, pp. 481–489, September–October, 1980.     

Reordering of scratch generator efferent activity produced by stimulating hindlimb muscle afferents in decerebrate immobilized cats

Reorganization of the parameters of efferent activity produced in the spinal generator by electrical stimulation of the ipsilateral hindlimb muscle nerves during different limb positions were investigated in decerebrate immobilized cats. A direct relationship was found between this reordering and the stage at which stimuli were applied. The rearranged duration of the scratch cycle showed a tendency to bring motor activity into phase with stimuli so that the stimulus falls due at the onset of the motor activity phase. This phasically collated rearrangement was observed where a shift had occurred in the relationship between "aiming" and "scratch" motion tending towards intensified activity in the muscles innervated by the stimulated nerve. Rearrangement became more evident when the hindlimb deflected from the target position in accordance with the direction of muscle stretching. The physiological significance of the interposition of the "no rearrangement" phase is discussed. It is deduced that this absence of change in duration and intensity can only be produced simultaneously when a certain relationship is achieved between the phase of afferent signal reception in the scratch cycle and signal intensity.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 3, pp. 372–382, May–June, 1987.     

Changes in the intensity of integral afferent inflow from limb receptors and in primary afferent terminal polarization during scratching in the decerebrate cat

Experiments performed on decerebrate cats showed that afferent activity accompanying scratching consists of two components—one with a tonic and the other with a periodic phase. The first of these is determined by limb position and the second closely related to speed and amplitude of angular changes occurring at the joints. Peak integral afferent activity within the cycle occurred at the end of the scratch phase itself, when aiming muscles are already operating. These two components of afferent activity produce corresponding changes in depolarization at primary afferent terminals (DPA), which are added to those DPA changes brought about by the effects of the central generator. Statistical relationships between the aforementioned processes were investigated. Mechanisms underlying afferent control over the operation of the scratch generator are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 20, No. 1, pp. 49–57, January–February, 1988.     

Changes in presynaptic processes during tonic sub-threshold activation of spinal scratch generator in the cat

It was found during experiments on immobilized decerebrate (at intracollicular level) cats that tonic sub-threshold activation of the spinal generator of scratching action (following application of tubocurarine or bicuculline to segments C₁-C₂) was accompanied by depolarization of primary afferent terminals, a reduction in the N₁ component of dorsal surface potential produced by stimulating the cutaneous afferents, and a reduction in the amplitude of dorsal root potentials and lead-phase polysynaptic response produced in motoneurons by stimulating the cutaneous and muscle afferents. A rise or a reduction in the activity of interneurons belonging to the interstitial nucleus connected respectively mono- and di-(oligo)synaptically with the afferents occurred in parallel with this. Spinalization produced the same changes in reverse in the animal. By administering DOPA to the spinal animal, a comparison could be made of changes occurring in the state of the segmental apparatus of the lumbar section of the spinal cord during tonic sub-threshold activation of spinal scratch generators and locomotor movements.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 2, pp. 236–243, March–April, 1987.     

Investigation of spinal neuronal mechanisms of movement control systems

Morphological and electrophysiological investigations of the means whereby the principal descending motor systems (the cortico-, rubro-, reticulo-, and vestibulo-spinal tracts) are connected with the segmental interneuronal apparatus and motoneurons show that these connections can be based on two different principles. Descending systems either activate motoneurons directly (monosynaptically) or are connected primarily with various interneuron systems, exerting their influence in that case by regulating the activity of simpler or more complex spinal mechanisms. The older descending system (reticulo- and vestibulo-spinal) possess a monosynaptic excitatory action of motoneurons; the evolutionarily newer descending systems, which transmit the most complex motor signals from the cerebral and cerebellar cortex to the spinal cord (cortico- and rubro-spinal), terminate synaptically in every case on interneurons. It is only in primates that a few cortico-spinal fibers form monosynaptic connections with motoneurons. The chief ways of action of the descending systems on interneurons are: control of the afferent inflow into the interneuron system by presynaptic inhibition of the corresponding synapses; control of the interneuron system by postsynaptic interaction with afferent influences; control of motoneurons through the specialized interneuron apparatus. The investigation shows that the last of these mechanisms functions in the cortico- and rubro-spinal, and possibly also in the reticulo- and vestibulo-spinal systems. The functional role of the various means of connection of the descending systems with the spinal neurons in the system of movement control is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 2, No. 2, pp. 189–202, March–April, 1970.     

Depolarization of different groups of lumbar afferent terminals during fictitious scratching

The kinetics of primary afferent depolarization (PAD) in the lumbar spinal cord was studied in immobilized decerebrate and decapitated cats during fictitious scratching. Fictitious scratching was accompanied by tonic and periodic PAD. Periodic PAD was cophased in different segments of the lumbosacral enlargement. Tonic depolarization was observed in terminals of all groups of afferent fibers studied (low-threshold cutaneous and of groups Ia and Ib). Periodic changes were observed only in endings of low-threshold cutaneous fibers and group Ib fibers. The physiological role of modulation of PAD by the spinal scratch generator is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 11, No. 6, pp. 569–577, November–December, 1979.     

Dependence of efferent activity parameters on limb position during fictitious scratching in decerebrate cats

The influence of tonic afferent inflow as conditioned by ipsilateral hindlimb position on the efferent activity parameters of the spinal generator governing scratching motion was investigated in immobilized decerebrate cats. A significant correlation was observed between motor activity parameters and ensuing bouts of scratching in the absence of afferent flow (after deafferentation of the limbs). This correlation was less pronounced when afferentation remained intact and declined when the limb was shifted from the "aimed" to either the "overaimed" or "deflecting backwards" placing of the limb. The statistically significant correlations found between the parameters of different stages of motor activity and their dependence on hindlimb positions during actual scratching could be responsible for the stability of intended placing of the limbs during the performance of oscillatory movements. Hindlimb deafferentation would appear closest to "aimed" position judging by the parameters of efferent activity and the nature of correlations between them.A. A. Bogomolets Institute of Physiology. Academy of Sciences of the Ukrainian SSR. Kiev. Translated from Neirofiziologiya, Vol. 15, No. 5, pp. 636–645, September–October, 1986.     

Scratch reflex evoked by strychnine applied to the spinal cord

Effective facilitation of the scratch reflex was observed in experiments on recently decerebrated and spinal cats in response to application of strychnine solution to the dorsal surface of the spinal cord. The receptive fields of the scratch reflex in this case depended on the segments to which the strychnine was applied. The receptive fields of a scratch reflex evoked by D-tubocurarine coincided with those of the intact adult animals, but the receptive fields for strychnine application were wider and corresponded to those of the scratch reflex in kittens [1, 10]. It is suggested that strychnine application abolishes the inhibition of the afferent inputs of the scratch reflex in the lower cervical segments of the spinal cord which has developed during ontogeny.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 6, pp. 622–625, November–December, 1978.     

Reorganization of segmental responses to peripheral stimulation during fictitious scratching in cats

Segmental reflex responses of the lumbosacral region of the spinal cord to stimulation of peripheral afferents were studied in immobilized decerebrate cats before and after application of D-tubocurarine or bicuculline to the superior cervical segments, potentiating the scratch reflex, and also during fictitious scratching evoked by mechanical stimulation of the ear. Application of these substances led to inhibition of the N₁-component of the dorsal cord potential, the dorsal root potential, and polysynaptic responses in efferent nerves. The appearance of fictitious scratching was accompanied by additional tonic inhibition of these responses, against the background of which modulation of the amplitudes of the responses was observed depending on the phase of fictitious scratching. Modulation of amplitudes of monosynaptic reflexes also developed during fictitious scratching. Against the background of these results the mechanisms and physiological role of reorganization of segmental responses during activation of the spinal scratching generator are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 2, pp. 196–203, March–April, 1981.     

Classification of lumbosacral neurons by their discharge pattern during evoked locomotion

Unit activity was recorded in the lumbosacral division of the spinal cord during evoked locomotion in mesencephalic cats with the afferent fibers from their hind limbs intact or divided. If the afferent fibers were intact, all neurons recorded showed modulation of activity during locomotion in the rhythm of stepping movements. In experiments on cats with afferent fibers from the hind limbs divided modulation was absent in 30% of neurons, while in the modulated neurons, the frequencies in the excitation phase were approximately the same as when the limb innervation was intact. Modulation of activity in some neurons occurred in response to stimulation of the locomotor region even before stepping movements began. The tuning of the spinal generator of stepping movements is discussed.M. V. Lomonosov Moscow State University. Institute of Problems in Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 4, No. 4, pp. 410–417, July–August, 1972.     

Responses of motor neurons of lumbar section of spinal cord elicited by the activity of the propriospinal pathways

We have carried out intracellular recording from the motor neurons of the lumbar section of the cat spinal cord with electrical stimulation of the propriospinal axons descending in the dorsolateral funiculus. To prevent activation of the long descending pathways of the lateral funiculus, ipsilateral hemisectioning of the spine was performed in the segments L₁-L₂ 10–14 days before the experiment. Stimulation of the dorsolateral funiculus in two segments cranial to the point of recording elicited in the flexor motor neurons essentially e.p.s.p. and in the extensor neurons i.p.s.p. with a latent period, on the average, of 1.97 and 1.93 msec, respectively. The amplitude of such p.s.p. considerably rose with rise in the frequency of stimulation of the funiculus to 50–100 a second. Activation of the segmental interneurons was observed only in a few cases. It is assumed that the synaptic processes elicited in the lumbar motor neurons are the result of the monosynaptic influences of the propriospinal neurons.A. A. Bogomolets' Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 1, No. 1, pp. 5–14, July–August, 1969.