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.     

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.     

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.     

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.     

Kinematics of different types of locomotor movements in the deafferented rat

The kinematics of rat hindlimb movements were assessed and compared pre- and post-deafferentation during swimming, forelimb treadmill locomotion plus hindlimb swimming motion, and walking using all four limbs. All types of locomotion were characterized by an increase in the frequency of locomotor rhythm and reduced amplitude of motion at the hindlimb joints following deafferentation. The reduced change observed in the angle of the coxofemoral joint, indicative of a horizontal component in locomotor motion, was mainly brought about by less marked extension. This would confirm evidence indicating that increased load on the extremities, with its ensuing naturally-occurring afferent outflow, is accompanied by a reduced locomotor motion rate and a rise in the amplitude of the latter due to intensified extension of the limb. The increased forward carriage of the hind limb seen during the transition to four-legged locomotion persisted after deafferentation; this may be considered a sign of coordination amongst the limbs. Deafferentation led to a reduction in the MEG of muscle activity, which was found to be lowest in swimming and highest during walking. The role of the afferent inflow in shaping different types of locomotor motion is evaluated.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 4, pp. 520–525, July–August, 1987.     

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.     

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.     

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.     

Activity of lumbosacral interneurons during fictitious scratching

Activity of lumbosacral spinal interneurons was studied during fictitious scratching in decerebrate, immobilized cats. Neurons whose activity changed during fictitious scratching were located in the substantia intermedia lateralis and ventral horn. Among these neurons cells were distinguished whose activity was modulated in rhythm with motor discharges to different muscles (61.6%) and cells which were activated tonically (21.4%) or inhibited tonically (17%). By correlation of activity with discharges to corresponding muscles the rhythmically activated neurons were divided into "aiming" (36.6%) and "scratching" (25%). Neurons whose activity was unchanged during fictitious scratching also were observed. These cells were located mainly in the more dorsal regions of gray matter. Neurons to which wide convergence of excitatory influences from high-threshold cutaneous and muscular afferents was observed were mainly placed in the "aiming" group. "Scratching" neurons, compared with "aiming," more often received inputs only from low-threshold cutaneous or high-threshold muscular afferents. Group Ia interneurons were activated in phase with the corresponding motoneurons. Passive displacement of the limb in a forward direction predominantly inhibited spike activity of the "aiming" and potentiated activity of the "scratching" neurons. The neuronal organization of the spinal scratch generator is discussed on the basis of the results.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 1, pp. 57–66, January–February, 1981.     

Depolarization of primary afferents during fictitious scratching in thalamic cats

The dorsal cord and dorsal root potentials were recorded in immobilized thalamic cats during fictitious scratching evoked by mechanical stimulation of the ear. Depolarization of primary afferents was shown to be simulated by the central scratching generator. Antidromic spike discharges appeared at the peak of the primary afferent depolarization waves in certain afferent fibers. Similar discharges arise in the resting state in response to stimulation of limb mechanoreceptors. It is suggested that during real scratching primary afferent depolarization and antidromic spikes evoked by it may effectively modulate the level of the afferent flow to spinal neurons.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 2, pp. 173–176, March–April, 1978.     

The central program of activation of hind-limb muscles during scratching in cats

Electrical activity in nerves to various hind-limb muscles was investigated in decerebrate and decapitated cats during fictitious scratching. By analogy with the phases of real scratchingaiming (flexion of the hip and ankle and extension of the knee) and scratching (the opposite movements in these same joints), the corresponding phases of motor discharges were distinguished. Depending on the type of these discharges the hind-limb muscles were divided into three groups. In the nerves to the muscles of group I activity was observed in the period of "initial aiming" and in the rhythmic "aiming phases" and was reciprocal to activity in the nerves to group II muscles starting the "scratching phases." Activity appeared in nerves to group III muscles both in the period of "initial aiming" and in the rhythmic "aiming phases" and "scratching phases." Passive forward deflection of the limb potentiated the "scratching phases" and weakened the period of "initial aiming" and the "aiming phases." The physiological significance of the organization of the central program and the design 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. 1, pp. 48–56, January–February, 1981.     

Both shared and specialized spinal circuitry for scratching and swimming in turtles

In principle, nervous systems could generate a behavior either via neurons that are relatively specialized for producing one behavior or via multifunctional neurons that are shared among multiple, diverse behaviors. I recorded extracellularly from individual turtle spinal cord neurons while evoking hindlimb scratching, swimming, and withdrawal motor patterns. The majority of spinal neurons recorded were activated during both scratching and swimming motor patterns, consistent with the existence of shared circuitry for these types of limb movements. These neurons tended to have a similar degree of rhythmic modulation of their firing rate and a similar phase preference within the hip flexor activity cycle during scratching and swimming motor patterns. In addition, a substantial minority of neurons were activated during scratching motor patterns but silenced during swimming motor patterns. This raises the possibility that inhibitory interactions between some scratching and swimming neural circuitry play a role in motor pattern selection. These scratch-specialized neurons were also less likely than the putative shared neurons to be activated during withdrawal motor patterns. Thus, these neurons may represent two separate classes, one of which is used generally for hindlimb motor control and the other of which is relatively specialized for a subset of hindlimb movement types.     

Reflex component of the swing phase: A comparative analysis of rat locomotion before and after deafferentation

A comparative analysis was made of the kinematics of movement and EMG activity during different types of locomotion before and after bilateral deafferentation of segments L₁-S₂ of the rat spinal cord. It was found that deafferentation is accompanied by a reduction in the amplitude of locomotor movements and by a delay in both the initiation and increase in duration of flexion in the knee and ankle joints during the swing phase, without producing much effect on the time course of hip joint flexion. An increase in the F period of the swing phase, at its lowest during swimming and highest during stepping, was also discovered, which accordingly rose in step with increasingly deficient afferent inflow. Flexor activity rose especially noticeably during dragging on the limb in the swing phase post-deafferentation. The role of peripheral afferent influence in shaping the F (swing) phase is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 5, pp. 654–659, September–October, 1987.     

Role of afferent activity in the generation of stepping movements

Efferent fibers of the hind limbs were divided and electrical activity of a filament from the ventral root of S1 was recorded in experiments on mesencephalic cats capable of locomotion in response to stimulation of the "locomotor region" of the midbrain. In response to weak stimulation of the locomotor region, when the forelimbs were not performing stepping movements, regular waves of activity appeared in the filament with a period close to the duration of the step during walking (0.5–1.0 sec). This periodic process was largely dependent on the tonic afferent inflow: various extero- and interoceptive stimuli applied to the hind limb could change the period of generation or abolish it. Active stepping movements of the forelimbs as well as passive movements of the hind limbs led to synchronization of activity in the filament with these movements. After division of the afferent fibers to the hind limbs the animals performed one or two steps in response to stimulation of the dorsal root of S1 by a short series of pulses. They could also perform independent stepping movements of the hind limb if 15–30% of the fibers in the dorsal root of L7 remained intact.M. V. Lomonosov Moscow State University. Institute of Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 4, No. 4, pp. 401–409, 1972.     

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.     

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.     

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.     

HANDEDNESS IN THE BROWN-THROATED PARAKEET ARATINGA PERTINAX EST RELATION WITH SKELETAL ASYMMETRY

Observations on 56 specimens of Aratinga pertinax when bringing food to the beak prove that 28 birds were right-handed while the other 28 were left-handed. A biometric analysis reveals a slight departure from bilateral symmetry in hindlimb bones in close relationship with handedness. In the right-handed birds, there is a significant predominance in the length of the right hindlimb as a whole and all right limb segments. The opposite holds true in left-handed parrots (except for the femur). Right-handed birds are in general more highly asymmetrical than left-handed ones. There is a positive correlation between asymmetry of homologous segments of a pair of limbs and the asymmetry of the other segments of the same pair of limbs. The absence of significant negative correlations between bilateral differences of the different segments of a limb indicates that departures from bilateral symmetry tend to affect the limb as a whole, and thus is not in agreement with the rule of compensating variations.     

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.     

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.