Limb movement,intensity of integral afferent impulses from limb receptors,and level of primary afferent terminal polarization during locomotion in cats decerebrated at high level

The relationship between parameters of electrical muscle activity, changes at hindlimb joint angles, intensity of integral afferent flow, and dorsal root potential during real-life locomotion was investigated in cats decerebrated at high level. Characteristics of rear limb movements before and after deafferentation were described. It was found that afferent activity during locomotion motion consists, of two components — a tonic and a periodic phasic stage. Three main waves may be distinguished in the latter, each of which gives rise to associated changes in the level of primary afferent terminal polarization. These changes in turn are summated with the effects produced by the central generator. Correlations, between the parameters of these processes were investigated and the mechanisms underlying afferent control of locomotion generator function discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 20, No. 1, pp. 119–127, January–February, 1988.     

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.     

Quantitative changes in efferent activity of the scratch generator produced by eliminating influences from the descending systems

The effects of signals proceeding along descending systems of the spinal cord on the parameters of efferent activity in the scratch generator (i.e., discharges in ventral roots L₅ and L₇) were investigated in decerebrate immobilized cats. It was found that eliminating cerebellar modulatory influences on nuclei of the descending system (decerebellation) leads to an altered ratio between the activity of generator hemicenters, increased instability of generator operation, a reduced statistical relationship between alteration in parameters of hemicenter activity, and raised sensitivity to afferent signals in the generator. Complete elimination of descending system influences (after severing the spinal cord at the anterior boundary of the first cervical segment) produced a reduction in the intensity of efferent activity and in the afferent sensitivity of the scratch generator. The functional significance of descending signals for operation of the scratch generator is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 1, pp. 123–131, January–February, 1990.     

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.     

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.     

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.     

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.     

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.     

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.     

Active selection of afferent information as the basic principle of peripheral correction of the activity of spinal rhythmic movement generators

This paper summarizes information obtained in the experimental study of the dynamics of polarization of central primary afferent endings and modifications of segmental responses to afferent stimuli during fictitious locomotion and fictitious scratching in immobilized, decorticated, decerebrate, and spinal cats. Fictitious locomotion was accompanied by tonic hyperpolarization, fictitious scratching by tonic depolarization of central primary afferent endings. Against the background of these long-lasting changes in primary afferent depolarization, it exhibited periodic changes in the rhythm of efferent activity. Periodic changes of depolarization were virtually in phase in different ipsilateral segments of the lumbosacral enlargement. Data on groups of afferent fibers in whose central endings tonic and phasic changes of polarization took place. The appearance of fictitious locomotion was accompanied by a tonic increase, and of fictitious scratching by tonic inhibition of several evoked segmental responses. These tonic changes were a background against which segmental responses were modulated in step with the working rhythm of the locomotion and scratching generators. Many of the changes in evoked segmental responses were shown to be based on modulation of polarization of central endings of primary afferents by locomotion and scratching generators. It is concluded that active tonic and phase-dependent selection of incoming afferent information is effected through modulation of presynaptic inhibition of the generator. The role of this selection in peripheral collection of activity of locomotion and scratching generators is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 3, pp. 343–353, May–June, 1984.     

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.     

Organization of the afferent input in the rabbit superior colliculus

The organization of the afferent input into the superior colliculus was investigated in unanesthetized curarized rabbits. The afferent signal reaches the rabbit superior colliculus via at least two groups of fibers with mean conduction velocities of 3 and 6 m/sec. The components C₁ and C₂ of the evoked potential reflect postsynaptic unit activity arising after the arrival of impulses along these groups of fibers. This is confirmed by investigation of the shape of the evoked potential after stimulation of different points of the afferent pathway, data on conduction velocities, and comparison of single unit activity with the phases of evoked potential. The presence of components of this potential with short latent periods is evidence of predominance of the direct retinotectal input in the rabbit, a fact which may be connected with the lissencephalic type of brain development.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 9, No. 3, pp. 281–289, May–June, 1977.     

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.     

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.     

Regulation of afferent transmission in the feeding circuitry of Aplysia

Although feeding in Aplysia is mediated by a central pattern generator (CPG), the activity of this CPG is modified by afferent input. To determine how afferent activity produces the widespread changes in motor programs that are necessary if behavior is to be modified, we have studied two classes of feeding sensory neurons. We have shown that afferent-induced changes in activity are widespread because sensory neurons make a number of synaptic connections. For example, sensory neurons make monosynaptic excitatory connections with feeding motor neurons. Sensori-motor transmission is, however, regulated so that changes in the periphery do not disrupt ongoing activity. This results from the fact that sensory neurons are also electrically coupled to feeding interneurons. During motor programs sensory neurons are, therefore, rhythmically depolarized via central input. These changes in membrane potential profoundly affect sensori-motor transmission. For example, changes in membrane potential alter spike propagation in sensory neurons so that spikes are only actively transmitted to particular output regions when it is behaviorally appropriate. To summarize, afferent activity alters motor output because sensory neurons make direct contact with motor neurons. Sensori-motor transmission is, however, centrally regulated so that changes in the periphery alter motor programs in a phase-dependent manner.     

Parameters of conduction via afferent nerve fibers in mice with streptozotocin-induced and genetically determined diabetes

The parameters of conduction via afferent nerve fibers were studied in mice with streptozotocin-induced and genetically determineddiabetes mellitus (9- to 12-week-old animals; streptozotocin was injected into 5-week-old mice). Recording of spinal cord dorsal surface potentials evoked by stimulation of the sciatic nerve showed that within the studied time interval the mice of the two diabetic groups were characterized by a moderate decrease (by 7.9% and 5.8%, on average) in the conduction velocity for afferent volleys (measured according to the delay of the peak of positivity of a volley) and by a considerable increase in the duration of the positive phase of these volleys (by 36% and 33%, respectively, as compared with the values in intact animals). Therefore, the population of relatively slow group A afferent fibers becomes noticeably larger in the sciatic nerve of diabetic mice even at early stages of the pathology, but at the same time a considerable amount of the fastest-conducting (about 45–60 m/sec) fibers is still preserved. The changes in mice with diabetes of different etiology were very similar, in spite of different hyperglycemia levels in these groups. Possible factors determining diabetes-induced modifications of the conduction velocity via the nerve fibers are discussed.Neirofiziologiya/Neurophysiology, Vol. 28, No. 4/5, pp. 173–178, July–October, 1996.     

Primary afferent depolarization induced by cyclically modulated natural hind limb proprioceptor activity in cats

Primary afferent depolarization (PAD), developing during passive movements of the ankle with a frequency of 0.14–5.0 Hz was investigated in decerebrate cats. An increase in the dorsal root potential, the amplitude of which was used to judge the intensity of PAD, was observed during both extension and flexion of the joint. Parallel with waves of the dorsal root potential, changes in amplitude of the N component of the dorsal cord potential in response to stimulation of a cutaneous nerve during different phases of the limb movement cycle were recorded. These changes were periodic in character and opposite in phase to oscillations of dorsal root potential. The mechanisms of the observed changes in the PAD level and also the functional significance of these changes during cyclic motor acts are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 3, pp. 372–380, May–June, 1985.     

Rearrangement of efferent activity of the locomotor generator under electrical activation of descending systems in immobilized cats

The effects of signals travelling through vestibulo-, rubro-, reticulo-, and corticospinal systems on the parameters of locomotor generator activity were investigated in decerebrate immobilized cats. Certain phase-linked alterations in these parameters were found to occur under the effects of electrical stimulation applied to these systems (brief trains of stimuli). The biggest increase in locomotor cycle length was produced by electrical stimulation of Deiter's nucleus — stimulus presentation at the end of the extension phase; stimulation at the flexor stage leads to a shortening of this cycle. Maximum increase in locomotor cycle length produced by electrical stimulation of the red nucleus and nucleus gigantocellaris reticularis together with the pyramidal tract takes place during the first half of the flexion phase. Electrical activation of these descending pathways during the flexion phase induces intensification of this phase and reduced intensity of the extension phase. Activation of the vestibulospinal tract produces increased and reduced intensification of the extension phase respectively. Principles of suprasegmental correction of locomotor and scratch generators are compared.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 2, pp. 151–160, March–April, 1991.     

Electron-microscopic analysis of synapses of the inferior mesenteric sympathetic ganglion in the afferent chain of sympathetic reflexes

There are axodendritic, axosomatic, dendrodendritic, and axoaxonic synapses in the inferior sympathetic ganglia. Preliminary transectioning of the preganglionic fibers, degeneration of these fibers, and circumferential preliminary cutting of all connections of the ganglion do not give rise to structural disturbances in all of the synapses: some of them remain intact. Preliminary cutting of the hypogastric nerves — which leads to degeneration of the central ends of peripheral afferent neuron axons, above all those of Dogel' type II cells — causes structural changes of a degenerative nature in a number of ganglionic synapses, although no changes are observed in most of them. Intact and structurally changed synapses are analyzed as synapses between afferent and efferent sympathetic neurons on the one hand, and between afferent neurons of different levels of the vegetative nervous system forming visceral afferent pathways that are interrupted in the ganglion on the other.Preliminary results were published in Dokl. Akad. Nauk BSSR,2, 934–937 (1967), and presented at the First All-Union Conference on Electron Microscopy, Leningrad, 1968.Institute of Physiology, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Neirofiziologiya, Vol.3, No. 1, pp. 84–88, January–February, 1971.