Effect of "animal hypnosis" on the rhythmic defensive dominanta

A defensive dominanta (stationary excitation focus) in the sensorimotor cortex of rabbits was formed by rhythmical electrodermal paw stimulation with the frequency of 0.5 Hz. After cessation of the stimulation, the state of hidden excitation was tested with acoustic stimuli, in response to which nonrhythmic activity of leg muscles increased or the leg rhythmically startled with the frequency close to that of the electrodermal stimulation. After conducting a routine hypnotizing procedure, the incidence of the rhythmic responses to testing stimulation increased, while the incidence of nonrhythmic responses decreased.     

"Animal hypnosis" and defensive dominant,behavioral aspect

A stationary excitation focus produced in the sensorimotor cortex of a rabbit by rhythmic electrodermal paw stimulation was manifested in the reaction to a testing sound stimulus earlier indifferent for the animal. Regardless of the stimulated paw (left or right), reactions to the testing stimuli appeared approximately in the equal percent of cases (70.7% and 71.5%, respectively). After a single-trial induction of the "animal hypnosis" state, it was difficult to produce the dominant focus by simulation of the left paw, whereas the results of the right-paw stimulation did not differ from those obtained during control stimulation. Consequently, the influence of hypnosis on defensive stationary excitation foci in different hemispheres was not the same.     

Correlated activity of neurons in the sensorimotor cortex of rabbits in the state of defensive dominanta and "animal hypnosis"

A hidden excitation focus (dominanta focus) was produced in the rabbit's CNS by threshold electrical stimulation of the left forelimb with the frequency of 0.5 Hz. As a rule, after the formation of the focus, pairs of neurons with prevailing two-second rhythm in their correlated activity were revealed both in the left and right sensorimotor cortices (with equal probabilities 29.3 and 32.4%, respectively). After "animal hypnosis" induction, the total percent of neuronal pairs with the prevalent dominanta-induced rhythm decreased significantly only in the right hemisphere (21%). After the termination of the "animal hypnosis" state, percent of neuronal pairs in the right cortex with prevailing two-second rhythm significantly increasead if the neurons in a pair were neighboring and decreased if they were remote from each other. Similar changes after the hypnotization were not found in the left cortex. Analysis of correlated activity of neuronal pairs with regard to amplitude characteristics showed that for both the right and left hemispheres, the prevalence of the two-second rhythm was more frequently observed in crosscorrelation histograms constructed regarding discharges of neurons with the lowest spike amplitude (in the right hemisphere) or the lowest and mean amplitudes (in the left hemisphere) selected from multiunit records.     

Instrumental and classical reflexes with water reinforcement]

Thirsty dogs were learned to regulate the supply of water by flexing the paw. The movement was effective only during an acoustic stimulation, either immediately at its beginning, or 10 to 20 sec. after its isolated action. The acoustic signal produced both flexion of the paw (instrumental reflex) and rhythmic swallowing movements which preceded the moment when water was fed into the mouth (classical conditioned reflex). The effect of prolongation of the isolated acoustic stimulation was manifested with extinction of the classical conditioned reflex and activation of the instrumental one.     

Characteristics of the systemic organization of the cortical neurons in various forms of the manifestation of the conditioned reflex to time

Conditioned food-procuring reflex to time (2 minutes interval) was elaborated in cats. By the method of cross-correlative analysis the combined neurones activity in microareas and between microareas of the motor cortex was compared at various forms of conditioned reflex manifestation. Three types of reactions were considered: A--decrease of respiratory movements amplitude towards the end of the studied interval between reinforcement; B--increase of the amplitude; C--food-procuring paw movement a few seconds before the reinforcement. All three forms of the conditioned reflex to time differed from each other by the level of increase of functional connections number by the moment of the reinforcing stimulus action, and also to a greater extent by the frequency of occurrence of intervals in which the sum of neuronal connections in all simultaneously recorded microareas was greater in the "active" phase than in the "inactive" one. These parameters did not always correlate with the change of impulses frequency of separate neurones which occurred considerably more seldom. All the observed changes were manifest significantly more often when the animals performed the instrumental food-procuring movement than during changes of only the respiratory movements amplitude.     

Cortical network activity before behavioral reaction and before its omission in rabbits with defensive dominanta

Defensive dominanta was formed in rabbit CNS. Activity of the cortical neuronal network was investigated in these rabbits in the state of quiet wakefulness and in the intervals between the presentations of testing stimulus (light flashes). Statistical analysis of spike trains revealed some distinctions in neuronal functional organizations in the excitation focus (sensorimotor cortex) and in the visual cortex in the states of quiet wakefulness, before the movement of the paw, and before the omission of the reaction. The evidence of different roles in the network activity of sensorimotor neurons that responded and not responded to light was obtained.     

Time and space distribution of coincident impulses in closed neural circuits in the sensorimotor cortex of the rabbit (the rhythmical defensive dominanta)

In the course of analysis of the conjugate unit activity of simultaneously recorded neurons in the sensorimotor cortex of rabbits, 22 closed neural circuits consisting of 3 or 4 neurons were considered. In the model of the defensive dominanta, 1-3 weeks after imposing rhythmic (2 s) activity to a rabbit, the distribution of coincident impulses was analyzed in real time. It was found out that the events when the coincident impulses of neural pairs were generated with two-second intervals could be shifted in time and space over a closed circuit of neurons in one direction. Two-second intervals between the coincident impulses of the neighboring pairs could be conjugate, i.e. the end of one interval in one pair coincided with the beginning of a two-second interval in the next pair. Conjugate intervals of the neighboring neural pairs could promote a pass-through of the information on the stimulus properties over the closed neuronal circuit, thus completing a full cycle. The longest passes-through lasted from 10 and 12 s. Also, more intricate variants of the information transfer were revealed. Thus, not only passes-through of the two- second intervals between the neuronal pairs were observed, but also, coincident impulses repeatedly occurred with this interval in some of the pairs of the circuits. The longest transitions lasted 16 and 22 s.     

Serotonin regulates rhythmic whisking

Many rodents explore their environment by rhythmically palpating objects with their mystacial whiskers. These rhythmic whisker movements ("whisking"; 5-9 Hz) are thought to be regulated by an unknown brainstem central pattern generator (CPG). We tested the hypothesis that serotonin (5-HT) inputs to whisking facial motoneurons (wFMNs) are part of this CPG. In response to exogenous serotonin, wFMNs recorded in vitro fire rhythmically at whisking frequencies, and selective 5-HT2 or 5-HT3 receptor antagonists suppress this rhythmic firing. In vivo, stimulation of brainstem serotonergic raphe nuclei evokes whisker movements. Unilateral infusion of selective 5-HT2 or 5-HT3 receptor antagonists suppresses ipsilateral whisking and substantially alters the frequencies and symmetry of whisker movements. These findings suggest that serotonin is both necessary and sufficient to generate rhythmic whisker movements and that serotonergic premotoneurons are part of a whisking CPG.     

Motor polarization dominance and "animal hypnosis"

Two kinds of dominanta were simultaneously formed under conditions of chronic experiments in rabbits. The motor polarization dominanta was formed under exposure of the right sensorimotor cortex of an animal to direct anodic current, and the state of "animal hypnosis" (the second dominanta) was induced. Animal behavior and electrophysiological characteristics were recorded. It was shown that the "animal hypnosis" induced at the optimum of the right motor polarization dominanta inhibited the motor reaction of the "dominant" extremity to testing stimuli. After the "animal hypnosis session, exposure of the right sensorimotor cortex to anodic current produced the latent excitation focus, which did not reach the level of summation. Two days later, exposure to testing stimuli developed the latent foci at first in the right cortex and then in subcortical structures. In the course of recovery of the motor polarization dominanta and its further change for the state characteristic of the "animal hypnosis", the patterns of cortical EEG coherence in the delta range typical of each kind of dominanta alternated in parallel with the time course of state changes.     

Significance of peripheral feedback in stepping movement generation under epideral spinal cord stimulation

In acute experiments on decerebrated and spinalized cats, the role of peripheral afferent input from hindlimbs in stepping patterns formation under epidural spinal cord stimulation (ESCS), was investigated. The hindlimb muscles' electromyographic activity and kinematic parameters of evoked stepping were analyzed. It has been shown that epidural stimulation (20-100 microA, 5 Hz) of L4-L5 spine segments induced coordinated stepping on the treadmill belt. In conditions of weight-bearing support (stopped treadmill, hindlimbs lifted above the treadmill), the stepping rhythmic was unstable, stepping cycle period and its internal structure having changed as well. With increased speed of locomotion the stepping frequency increased due to the duration of the support phase decreasing. Forward stepping could be reversed to backward stepping by changing the direction of the treadmill belt movement. In 2-4 hours after complete spinal transection (T8-T9), the epidural stimulation elicited stepping movements on a moving treadmill only. It was found that the influence of peripheral feedback on initiation of the stepping after spinalization increased. Peripheral feedback seems to play a major role in determining the fundamental features of motor output during the ESCS.     

Oscillatory motion in human neutrophils responding to chemotactic stimuli

Human neutrophils treated with the secretion inhibitor 17-hydroxywortmannin were stimulated with fMLP, C5a, PAF or LTB4, and the ensuing shape change was studied. The cells rapidly extended lamellipodia and showed regular oscillatory behaviour. The oscillations were observed in both light transmission and 90 degrees light scattering, had the same frequency in each case, and disappeared within 30-50 seconds. Light scattering theory suggests that they reflect rhythmic changes in the shape and/or size of the chemotactically stimulated cells, possibly related to crawling or swimming movements associated with migration.     

Rhythmic Acoustic Stimulation as a Method for Regulating the Functional State of the CNS in Young Schoolchildren

The author studied the dynamics of EEG (spectral power density and coherence functions) and autonomic (electrodermal resistance, EDR) indices in young schoolchildren with changes in the functional state of the CNS caused by rhythmic sensory stimulation (acoustic signals with frequencies of 6 and 9 Hz). Both of these signals influenced the CNS and may be used to achieve relaxation. Their comparison demonstrated both similar postrelaxation shifts (increased coherence of distant connections) and frequency-specific phenomena (more numerous significant changes in the respective frequency ranges). Thus, the signal frequency determines the pattern of physiological shifts, influencing the relaxation quality. Low-frequency (6 Hz) stimulation caused more pronounced changes in the CNS, reflected in enhanced EDR, and a stronger increase in the short-term memory volume. The author discusses the frequency-specific neurophysiological mechanisms of the effect of stimulation on the functional state of the brain.     

Effect of hypoxia on the excitability of two cranial reflexes in unanaesthetized fetal sheep

In fetal sheep acute hypoxia causes a decreased incidence of breathing movements and motor activity, and the excitability of polysynaptic reflexes in the hindlimbs is depressed. To determine whether this inhibitory effect extends to other areas in the fetal CNS, we have studied the effect of hypoxia on two reflexes with cranial pathways. The digastric (jaw opening) reflex was elicited by stimulation of the dental nerve through a pair of stainless steel electrodes implanted into the mandible (4 fetuses). The thyroarytenoid muscle of the larynx was reflexly activated by stimulation of the superior laryngeal nerve by a cuff electrode (4 fetuses). Low level stimulation at 1.5-2 X threshold was repeated at approximately 2 min intervals for 3-4 h; the stimulation did not alter the pattern of electrocortical activity, breathing movements, or cause arousal. The amplitude of the digastric reflex was greatest during low voltage electrocortical activity; conversely, the amplitude of the thyroarytenoid reflex was greatest during high voltage electrocortical activity. Isocapnic hypoxia lasting 30-60 min (16 trials), in which the PaO2 was reduced to 12-14 mmHg, did not reduce the amplitude of either reflex. The reduction of thyroarytenoid reflex amplitude which normally occurred during low voltage electrocortical activity was not present during hypoxia. These experiments show that the inhibitory effects of hypoxia on spinal reflexes, breathing movements and motor activity do not include these cranial pathways.     

Stimulation of the hippocampus and its effect on electrographic manifestations of the brain in unrestrained rats.

The dorsal hippocampus was electrically stimulated in unanaesthetized, unrestrained rats with a cobalt-gelatin rod in their cortex. The significance of the hippocampus in the elicitation of both physiological spontaneous rhythmic activity (episodic activity of 8--9/sec frequency bound, in rats, to a state of quiet wakefulness, and "sleep spindles") and pathological rhythmic activity of the self-sustained after-discharge (SSAD) type was determined from the aspect of the EEG and behavioural characteristics. 1. Single electrical pulses (0.1 msec, 1--10 V, 0.3/sec) elicited an evoked potential bilaterally in the somatosensory cortex. Elicitation of rhythmic after-activity (of the type of episodes or sleep spindles) was observed only in some cases in which an adequately strong stimulus was used. 2. Repeated series of rhythmic electrical stimuli following each other at short intervals (2--3 min) led to the formation of SSAD in about one third of the cases and at all stimulation frequencies (3-15/sec), although low frequencies (3--4/sec) were the least effective. The character of the SSAD and simultaneous behavioural phenomena differed fundamentally from those evoked by electrical stimulation of the thalamus (Chocholová et al. 1977). The development of paroxysmal after-activity was signalled by responses of a more or less distinct "recruiting" character during stimulation. On the basis of a comparison of electrographic and behavioural manifestations after electrical stimulation of the thalamus and hippocampus, the possibility of both thalamic and extrathalamic projection from the hippocampus to the cortical region is considered.     

Dynamics of driven rhythm in neuronal assemblies in sensorimotor and visual cerebral cortices in rabbit

Coincident activity of pairs of neurons in the sensorimotor and visual areas of the cerebral cortex was studied in naive, learning, and trained rabbits during the formation of a hidden excitation focus in their central nervous system (a defensive dominanta) of the rhythmic nature. In the trained rabbits (as compared to the naive animals), percent of neuronal pairs (both neighboring and distant) in whose coincident activity the rhythm of stimulation prevailed was higher. In the visual cortex, percent of such pairs was significantly higher only for the distant neurons. Analysis of interaction between neurons in the visual and sensorimotor cortices revealed increasing the number of neuronal pairs with the driven rhythm while training. Such an increase was observed when both sensorimotor and visual neurons were considered as leading.     

Effect of Blocking of Calcium Channels on Cognitive Processes and General Motor Activity in Normal and Stressed Rats

In Wistar rats, we studied the effects of injections of a Ca²⁺ channel blocker, verapamil, on realization of a food-procuring operant conditioned reflex, OCR, and general motor activity within intersignal periods in the norm and under conditions of stress-induced disorders. The OPRs and a few behavioral phenomena (immobilization, grooming, research behavior, orientational and locomotor activity, vertical stands, and intersignal limb movements in a manger) were recorded. The acute stress state was induced by intense acoustic stimulation (a loud ringing sound presented in the course of OCR realization). Inhibition of the conditioned reflex activity (immobilization of the animal within an interstimulus period) and weakening of attention to the manger resulted from stress induction. Stress-related behavioral effects evoked by intense auditory stimulation were eliminated against the background of the action of verapamil, while the OCR and motor activity were not inhibited. Verapamil suppressed reactions of fear and anxiety in a dose-dependent manner and promoted concentration of attention; these effects improved the integrative functions and abilities to adequately estimate the signals in a given situation of the OCR performance. Such effects can be based on weakening of stress-related adrenaline release and certain normalization of the state of the cardiovascular systems due to partial blocking of calcium channels.     

Formation of "caudate spindles" in the rabbit sensomotor cortex during ontogeny

Electrical activity of the sensomotor and visual areas of the neocortex during stimulation of the caudate nucleus was recorded in young rabbits aged 3–60 days and in adults. Single stimulation of the caudate nucleus was found to cause the appearance of characteristic bursts of spindle-like rhythmic activity ("caudate spindles"), described previously in cats and monkeys, in the adult rabbit cortex. The latent period of the caudate spindle was about 200 msec, its duration 1–3 sec, and the frequency of its oscillations of the order of 12 Hz. Caudate spindles were most marked in the sensomotor cortex of the ipsilateral hemisphere. In rabbits under 10 days old caudate spindles were not found even if the intensity of stimulation was increased many times. Starting from the age of 15 days bursts of rhythmic activity resembling caudate spindles, but with lower frequency (about 8 Hz), longer latent period (up to 350 msec), and also with a higher threshold, appeared in the sensomotor cortex. The definitive type of caudate spindles was established toward the end of the first month of postnatal life, corresponding to the time of formation and complication of conditioned-reflex activity in developing animals.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 1, pp. 11–15, March, 1985.     

Comparative characteristics of septal "burst" neurons after elimination of afferent effects of the reticular formation in the rabbit

Comparative analysis of characteristics of rhythmic theta-activity in the neurones of the medial septal nucleus and nucleus of diagonal band was performed in intact rabbits after. i. v. injection of pentobarbital, and in rabbits with chronic lesion of the ascending brain-stem afferent fibers. In both conditions theta-bursts disappeared in some cells with unstable periodic rhythmic modulation; substantial population of the septal units preserved regular burst activity. Main characteristics of theta-bursts were almost identical in both states, their mean frequency decreased to 3.5 Hz. The theta-rhythm in hippocampal EEG was usually absent; but low-frequency rhythmic activity could be evoked by electrical or sensory stimulation as well as by injection of bemegrid or physostigmine. The data show that the ascending brain-stem afferents control: the frequency of the bursts in a population of septal units regarded as bursting pace-maker cells; the total number of the septal cells secondarily (synaptically) involved into rhythmic activity. The effect of pentobarbital upon theta-rhythm results from elimination of these influences upon the septal cells.     

The pattern and influential factors of aquatic pharyngeal movements of Trionyx sinensis

• 1.1. The pharyngeal movements of Trionyx sinensis during submersion where recorded with physiological instruments.
• 2.2. Anoxia or hypercapnia caused a marked increase in breathing rate of tested turtles during voluntary diving, and in anoxia there was a significant increase in the frequency of aquatic pharyngeal movements while hypercapnia had a slight or no effect on the frequency of these movements.
• 3.3. During voluntary diving when turtles could easily extend their heads out of water to breathe air, the frequency of rhythmic pharyngeal movements was lower; but during forced submersion, the frequency was higher and the movements were continuous.
• 4.4. The frequency increased more rapidly and greatly when turtles were in forced submersion than when they dived freely and could easily surface to breathe in N₂.
• 5.5. The frequency of pharyngeal movements of T. sinensis during diving in an aquarium with water depth of 30 or 45 cm was markedly higher than that at a water depth of 15 cm. Disturbing stimuli also influenced the aquatic rhythmic pharyngeal movements of T. sinensis.

     

Are interlimb interactions disturbed in patients with Parkinson’s disease? A study under unloading conditions

During natural human locomotion, neural connections are activated that are typical of regulation of the quadrupedal walking. The interaction between the neural networks generating rhythmic movements of the upper and lower limbs depends on tonic state of each of these networks regulated by motor signals from the brain. Distortion of these signals in patients with Parkinson’s disease (PD) may lead to disruption of the interlimb interactions. We examined the effect of movements of the limbs of one girdle on the parameters of the motor activity of another limb girdle at their joint cyclic movements under the conditions of arm and leg unloading in 17 patients with PD and 16 healthy subjects. We have shown that, in patients, the effect of voluntary and passive movements of arms, as well as the active movement of the distal parts of arms, on the voluntary movement of legs is weak, while in healthy subjects, the effect of arm movements on the parameters of voluntary stepping is significant. The effect of arm movements on the activation of the involuntary stepping by vibrational stimulation of-legs in patients was absent, while in healthy subjects, the motor activity of arms increased the possibility of involuntary rhythmic movements activation. Differences in the effect of leg movements on the rhythmic movements of arms were found in both patients and healthy subjects. The interlimb interaction appeared after drug administration. However, the effect of the drug was not sufficient for the recovery of normal state of the neural networks in patients. In PD patients, neural networks generating stepping rhythm have an increased tonic activity, which prevents the activation and appearance of involuntary rhythmic movements facilitating the effects of arms on legs.