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K V Baev

Publications and source records attributed to K V Baev.

At least 55 records · Page 3Linked to original sources
PubMed1986

[New locomotor areas of the brain stem of the cat].

New sites in the brainstem eliciting treadmill locomotion have been revealed in decerebrated cats by means of electrical stimulation. These sites--cochlear nuclei, ventral spinocerebellar tract and resciform body which includes dorsal spinocerebellar tract--are located outside the known locomotor regions. It is suggested that the nonspecific afferent activation of the brainstem reticular formation during electrical stimulation of the mentioned sensory tracts is sufficient for the initiation of the treadmill locomotion.

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PubMed1986

[Relation between parameters of efferent activity and limb position during fictive scratching in the decerebrate cat].

The influence of tonic afferent inflow conditioned by ipsilateral hindlimb position on the spinal generator of scratching efferent activity parameters was investigated in immobilized decerebrated cats. When the afferent inflow was absent (after the hindlimb deafferentation) strong correlation between the motor activity parameters of successive "scratch" cycles was observed. In case of the intact afferentation this correlation was somewhat weaker and decreased with shifting the hindlimb from the aimed position to overaimed or deflecting backward. The discovered statistically significant correlations between the parameters of different motor activity phases and their dependence on the hindlimb position are organized in such a way that they can provide stability of the aimed position of the hindlimb carrying out oscillatory movements. According to the parameters of the efferent activity and their correlation type, the hindlimb deafferentation is most similar to the aimed position of the hindlimb.

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PubMed1985

[Depolarization of primary afferents during real scratching in the cat].

Changes in depolarization of primary afferents and their correlation with afferent impulsation and limb movement were studied in the lumbar spinal cord during real scratching of decerebrated cats. Two components in rhythmic dorsal root potential were observed. First--centrally evoked, retained during fictitive scratching after immobilization; second--evoked by afferent discharge, coming to the spinal cord during the scratching phase of the limb movement.

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PubMed1985

[Projection of forebrain structures of the cat to the hypothalamic locomotor area].

Descending projections of brain cortex and basal ganglia to the hypothalamic locomotor region were demonstrated in cat with horseradish peroxidase technique. Neurons projecting directly to the functionally identified locomotor region are dispersed in different gyri with predominance in areas 4 and 6 of the motor cortex. Such neurons are also located in entopeduncular nucleus. Massive cortico-and pallido-hypothalamic projections as a rule do not reach the most caudal hypothalamic divisions where the locomotor region is localized.

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PubMed1985

[Projections of neurons of the hypothalamic locomotor region to brain stem and spinal cord structures in the cat].

Efferent projections of the hypothalamic locomotor region were studied by means of the horse-radish peroxidase technique. Labelled neurons in this region after HRP injections in different brain structures including lumbar spinal cord and other identified brainstem locomotor zones were found mainly ipsilaterally. The most considerable amount of labelled hypothalamic neurons was observed after HRP injections in the medial brainstem reticular formation and in the locus coeruleus area. The hypothalamic locomotor region also forms direct projections to the mesencephalic locomotor region and to the locomotor strip.

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PubMed1984

[Active selection of afferent information--the principle underlying peripheral correction of the function of spinal generators of rhythmic movements].

The paper presents data obtained in experiments on the study of primary afferent depolarization and retuning of segmental reactions to afferent signals during fictitious locomotion and fictitious scratching in immobilized decorticated, decerebrated and spinal cats. Fictitious locomotion was accompanied by sustained hyperpolarization, while fictitious scratching--by sustained depolarization of primary afferent central terminals. On the background of tonic changes periodic waves of primary afferent depolarization coinciding with the rhythm of efferent activity were observed. In different ipsilateral lumbosacral segments these periodic waves occurred in phase. The data are presented about the groups of afferent fibres in which central endings display tonic and phasic changes of primary afferent depolarization. Fictitious locomotion led to tonic increase and fictitious scratching--to tonic decrease in a number of evoked segmental reflex reactions. These tonic changes served as the background on which segmental reactions were modulated with the rhythm of locomotor and scratching generators. It is shown that the modulation of polarization of central primary endings by locomotor and scratching generators is the reason for many changes in reflex reactions. The conclusion is made that due to modulation of presynaptic inhibition the generators perform an active tonic and phase-dependent selection of afferent information. The role of such active selection in the peripheral correction of the function of locomotor and scratching generators is discussed.

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PubMed1983

[Depolarization of primary afferents induced by selective activation of propriospinal tracts].

Primary afferent depolarization (PAD) in the lumbosacral enlargement of the spinal cord evoked by selective activation of propriospinal (PS) pathways was studied in anesthetized cats. Activation of PS pathways in the lateral funiculus was more effective for PAD generation than that in the ventral funiculi. Excitation of PS pathways evoked PAD in terminals of cutaneous and muscle fibres including Ia muscle fibres. Neuronal mechanisms of intersegmental distribution of PAD and its possible functions are discussed.

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PubMed1981

[Retuning of segmental responses to peripheral stimulation during fictive locomotion in cats].

Segmental reflex responses of the lumbosacral spinal cord to peripheral afferent stimulation were investigated in immobilized decorticated cats before and during fictitious locomotion. Appearance of fictitious locomotion was accompanied by an increase of the N1 component of the dorsal cord potential and of the dorsal root potential. Modulation of these responses depending on the phase of fictitious locomotion was observed against a background of their tonic increase. The N1 component and dorsal root potential had larger amplitudes when they appear at the end of the "extensor" phase and at the beginning of the "flexor" phase and smaller amplitudes when they were evoked at the end of the "flexor" phase and at the beginning of the "extensor" phase. Poly- and monosynaptic reflex responses of motoneurons revealed the same phase dependence during fictitious locomotion. Mechanisms and physiological significance of the revealed retuning of segmental reflex responses are discussed on the basis of the obtained data.

Animals↗
PubMed1981

[Central program for activation of hindlimb muscles during scratching in cats].

Electrical activity in nerves of different hindlimb muscles was investigated during fictitious scratching in decerebrated and decapitated cats. Phases of motor discharges could be distinguished corresponding to the phases of real scratching: aiming (flexion in the thigh and ankle joints and extension in the knee joint) and scratching (opposite movements in the same joints). According to the pattern of the discharges the hindlimb muscles were divided into three groups. In the nerves to the muscles of the 1st group the activity was observed during "initial aiming" period and during rhythmic "aiming phases". It was reciprocal to the activity in the nerves to the muscles of the 2nd group appearing during "scratching phases". In the nerves to the muscles of the 3d group the activity was observed both in "initial aiming" period and in rhythmic "aiming and scratching phases". Passive forward deflexion of the limb intensified the "scratching phases" and decreased the intensity of the discharges during "initial aiming" and "aiming phases". Physiological significance of such an organization of central program and structure of spinal scratching generator are discussed.

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PubMed1981

[Activity of interneurons of the lumbosacral division of the spinal cord during fictive scratching].

Impulse activity of lumbosacral interneurons was recorded extracellularly during fictitious scratching in decerebrated immobilized cats. Most neurons whose activity was modulated during fictitious scratching were revealed in the lateral intermediate zone and in the lateral ventral horn. These neurons were divided into some groups differing in the type of activity modulation during fictitious scratching. Neurons whose activity did not change during fictitious scratching were mainly located dorsally in the gray matter. Cells showing wide convergence of excitatory influences from high threshold cutaneous and muscle afferents referred mainly to "aiming" neurons. In contrast to "aiming" neurons, most cells with inputs from only low threshold cutaneous or high threshold muscle afferents belonged to "scratching" neurons. The neuronal activity in different groups is shown to depend on the limb position. The neuronal organization of the spinal scratching generator is discussed on the basis of the obtained data.

Animals↗
PubMed1981

[Reorganization of segmental reactions to peripheral stimulation during fictive scratching in the cat].

Segmental reflex responses of the lumbosacral spinal cord to peripheral afferent stimulation were investigated in immobilized decerebrated cats before and after d-tubocurarine or bicuculline application to the upper cervical segments and during fictitious scratching evoked by mechanical stimulation of the pinna. Application of these drugs led to a decrease of N1 component of the cord dorsum potential, dorsal root potential and polysynaptic responses in efferent nerves. The appearance of fictitious scratching was accompanied by additional tonic inhibition of these reactions and against its background the modulation of amplitudes of segmental reactions depending on the fictitious scratching phase was observed. Modulation of monosynaptic reflexes was also observed during fictitious scratching. Mechanisms and physiological significance of retuning of segmental reflex responses during activation of a spinal scratching generator are discussed on the basis of the data obtained.

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PubMed1980

[Statistical characteristics of impulse activity of spinal locomotor centers].

The statistical analysis of the neuronal impulse activity of spinal locomotor centres was performed at rest and during generation of efferent discharges in thalamic immobilized cats. The activation of the spinal locomotor generator was accompanied by shortening of interspike intervals in neuronal spike trains and reduction of their fluctuations. During this process the interspike interval histograms became more symmetrical and the quantity of neurons which had regular oscillations in autocorrelation histograms increased considerably. At rest neuronal spike trains were characterized by dependence of successive intervals. This dependence increased during generation of efferent discharges. Possible mechanisms of the reconstruction of time organization of the neuronal impulse activity of spinal locomotor centres during their activation are discussed.

Animals↗
PubMed1980

[Mathematical analysis of the possibility of detecting a correlation between the spike trains of weakly interacting neurons].

The quantity of impulses which is necessary to be registered for detecting a reliable correlation between spike trains of synaptically connected neurons was estimated using a mathematical model. This quantity of impulses was studied as dependent on the weight of connection between neurons (the amplitude of EPSP evoked by a single impulse of an input neuron in an output one), on the intensity of total background excitatory influences upon the output neuron and on its own parameters. The necessary quantity of impulses was 10(7)-10(8) for cells with connection weights, parameters and characteristics of background activity similar to those of real spinal neurons. An increase in the amplitude of unitary EPSP and a decrease in the intensity of the input background impulse train and in duration and amplitude of interspike hyperpolarization of the postsynaptic neuron led to a decrease in the quantity of impulses necessary for detecting a reliable correlation. The possible principles of the construction of the spinal locomotor generator are discussed on the basis of those data.

Animals↗
PubMed1980

[Polarization of terminals of the primary afferents of the lumbar region of the spinal cord during fictitious locomotion].

Changes in electric polarization of lumbosacral primary afferent terminals were studied during fictious locomotion of immobilized decorticated and spinal cats. Fictitious locomotion was accompanied by a stable hyperpolarization of afferent terminals. In the presence of hyperpolarization a periodic depolarization took place with the rhythm of efferent activity. These tonic and phasic changes were observed in the terminals of all the studied groups of afferent fibres (cutaneous and muscle Ia and Ib). Periodic depolarization was in-phase indifferent ipsilateral lumbosacral segments. During fictitious gallop the changes in depolarization of primary afferent terminals were in-phase on different sides; during fictitious walking these periodic changes were of out-of-phase character. Physiological significance of changes in electric polarization of primary afferent terminals by the spinal locomotor generator is discussed on the basis of the data obtained.

Animals↗
PubMed1980

[Changes in the excitability of central endings of the superior laryngeal nerve following activation of the respiratory center].

Changes in polarization of central afferent terminals of the superior laryngeal nerve with variations in the level of the respiratory generator activity evoked by a short (up to 1 min) asphyxia were investigated in experiments on anesthetized and paralyzed rabbits using Wall's method. Antidromic responses decreased up to 5-20% of the control level during activation of the respiratory generator with an increase in frequency and amplitude of rhythmic discharges in the phrenic nerve evoked by a short asphyxia. It is supposed that the primary afferent polarization depends not only on the level of afferent inflow but also on the activity of the central respiratory generator.

Animals↗
PubMed1979

[Central program for interaction between the hindlimbs of cats during locomotion].

Central program of interaction of hindlimbs during fictitious locomotion expressed in the time structure of motor discharges in nerves to different muscles was investigated in decerebrated and spinal immobilized cats. It was shown that in the decerebrated animals the program of interaction of hindlimbs (alternative or synphase) is determined by interaction of the flexor half-centres. The latter work either in-phase or out-of-phase. The character of activity of extensor half-centres is determined secondarily by alternating interaction of each of them with homolateral flexor half-centre. After injection of DOPA the central program of interaction of hindlimbs can be determined by synchronous work of extensor half-centres.

Animals↗
PubMed1979

[Late prolonged discharges in the motor nerves of the hindlimbs and their relationship to locomotor rhythmicity in thalamically immobilized cats].

Effects of flexor reflex afferents stimulation were investigated on high decerebrated curarized cats. Stimulation of ipsilateral flexor reflex afferents evoked late long-lasting discharges in flexor nerves. Contralateral flexor reflex afferents stimulation evoked late discharges both in extensor and flexor nerves. Transition from late discharges to rhythmic discharges was observed. Early segmental reflexes were tonically depressed in thalamic in comparison with acute spinal cats. A similar tonic depression of segmental reflexes took place in acute spinal cats after DOPA injection. Segmental reflexes were distinctly modulated during late and rhythmic discharges. On the basis of the data available possible central mechanisms of the observed changes of segmental reflexes are discussed.

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