Functional role of the red nucleus in the cerebral cortex-cerebellum-spinal cord communication system

Unilateral transection of the rubrospinal tract before lesion of the red nucleus or the ventrolateral thalamic nucleus has been shown to facilitate recovery of operantly conditioned reflexes and compensatory processes in rats. Such strengthening of the recovery plasticity and operantly conditioned was found when transection of the bulbar pyramide performed before ablation of the sensorimotor cortex. These influences are explained by activation of the rubroolivary projection, which is switching of descending cortico-rubrospinal system on the corticospinal system, and on the contrary. The general property of this phenomenon is that preliminary lesion of the peripheral part of the descending spinal projection to acquire a signal forestalling significance for mibilization of compensatory brain capacity in order to recovery the deficit of central link of the system.     

Relation between the level of conditioned reflex activity and concentration of serotonin in the blood of normal and neurotic dogs

Higher nervous activity of dogs was studied using Pavlovian method of alimentary salivary conditioned reflexes. Serotonin (5- hydroxytryptamine) content in the venous blood was defined by means of fluorescent spectrofluorimeter using orthophthalic dialdehyde. A high level of conditioned and unconditioned reflexes was accompanied by a low serotonin blood content, while a low level of reflexes was accompanied by a high serotonin content. Negative correlation is supposed to exist between the degree of activation of nervous processes and blood serotonin content. Blood serotonin content increased in dogs in experimental neurosis with expressed reduction of the level on alimentary conditioned and unconditioned reflexes.     

The significance of the thalamic parafascicular complex in tracking processes in cats

In conditions of free behaviour, trace processes of various complexity degrees (conditioned reflexes to time, temporal prognostication and delayed behaviour) were studied in cats in norm and following electrolytic destruction of some thalamic structures. It has been shown that parafascicular nuclei of the cat thalamus take part in the control of temporal reactions characteristics, and the thalamus median centre provides for generalization function proceeding on the basis of complicated trace phenomena connected with events prognostication.     

Role of intralaminar thalamic nuclei in strengthening inhibition induced by stimulation of the caudate nucleus

The influence of preliminary subthreshold activation of thalamic intralaminary nuclei on achievement of instrumental reflex and on inhibitory effects, caused by stimulation of the caudate nucleus head, were studied in chronic experiments on 5 dogs with a model of instrumental defensive conditioned reflexes, providing for maintainance of a given posture. It was shown that the preceding high-frequency electrostimulation of intralaminary nuclei activates motor components of the instrumental response (shortened latency, EMG and mechanogram of the response, increased amplitude of instrumental response) and significantly lowers threshold strength of the current, necessary for obtaining "caudate pause". The greatest increase in inhibitory influences, caused by stimulation of the caudate nucleus head, was observed when thalamic stimulation preceded stimulations, localized in the dorsolateral segment of the caudate nucleus head. The obtained data are discussed in aspect of Buchwald et al. hypothesis on the existence of "caudate loop".     

Effect of a cyclic analog of enkephalin on learning and memory in the mouse

In experiments on mice, the effect of cyclic analogue of enkephalin (CAE) on the processes of learning and memory was studied in control animals and in animals with changed functional state of monoaminergic brain systems. Administration of the peptide to intact animals significantly accelerated the acquisition of conditioned reflexes of two-way avoidance and did not significantly affect the retention of these reflexes and their subsequent reproduction. Retention and reproduction of conditioned reflexes elaborated in one combination, was disturbed. Administration of iprazid did not eliminate the "accelerating effect" of CAE on the formation of conditioned reflexes of the two-way avoidance but sharply disturbed their retention. In such conditions, the amnesing iprazid effect increased still more. Besides, under CAE effect, the activity of acetylcholinesterase in the motor and especially in the visual cortex of the mice increased. The obtained data testify to an important role of the monoaminergic and cholinergic brain mechanisms in realization of CAE effects on the processes of learning and memory.     

Changes in the complex conditioned reflex activity of rat pups under the influence of penta-peptide]

Influence of YFRKD, modified fragment of interferon-alpha, on the formation of two-links system of feed-procuring conditioned reflexes was studied in rats in ontogenesis. The experiments have shown that YFRKD impedes both current learning and use of previous experience. The process of synthesis of two reflexes in united complicated functional complex is disturbed.     

Vector representation of associative learning

I. P. Pavlov [12] has shown that conditioned reflexes are selective both with respect to conditioned stimuli and to conditioned reflexes elicited by those conditioned stimuli. At the neuronal level selective aspects of conditioned stimuli are based on detectors selectively tuned to respective stimuli. The selective aspects of conditioned reflexes are due to command neurons representing specific unconditioned reflexes. It can be assumed that conditioned reflexes result from association between selective detectors and specific command neurons. The detectors activated by a conditioned stimulus constitute a combination of excitations--a detector excitation vector. The detector excitation vector acts on a command neuron via a set of plastic synapses--a synaptic weight vector. Plastic synapses are modified in the process of learning making command neuron selectively tuned to a specific conditioned stimulus. The selective tuning of a particular command neuron to a specific excitation vector referred to a conditioned stimulus is a basis of associative learning. The probabilities of conditioned reflexes elicited by conditioned and differential stimuli implicitly contain information concerning excitation vectors that encode respective stimuli. Contribution of the vector code to associative learning was explored combining differential color conditioning with intracellular recording from color-coding neurons. It was shown that colors in carps and monkeys are represented on a hypersphere in the four-dimensional space similar to human color space. The basis of the color space is constituted by red-green, blue-yellow, brightness and darkness neurons.     

Peculiarities of modifying influence of the factors forming the functional status of the central nervous system on dynamics of the rat higher nervous activity disturbances totally exposed to electron and gamma-radiation at a dose of 100 Gy

The dynamics of using a stabilized motor defensive conditioned reflex of active avoidance in "shuttle-box" in rats after the total influence of high energy electrons and gamma-rays at a dose of 100 Gy and a modifying influence of the two most important factors forming the functional status of the central nervous system: the stage of the conditioned reflex consolidation and typological peculiarities of the higher nervous activity have been investigated. The influence of both types of ionizing radiation has been shown to cause far more profound disturbances of non consolidated conditioned reflexes in comparison with the automatized conditioned reflexes and provoke an inverted picture of disturbances in the animals with opposed peculiarities of the higher nervous activity. The qualitative picture of the dynamics of disturbances that are caused by these types of radiation is identical. In summary, the studied conditions that form the functional status of the central nervous system determine the nature of neuroradiation syndrome to a greater extent than differences in the effectiveness of these types of radiation.     

Effect of activating the putamen on alimentary conditioned reflexes in dogs

The influence was studied of the near-threshold high- and low-frequency stimulation of the putamen on achievement of alimentary conditioned reflexes in dogs. Both low- and high-frequency activation of the examined structure significantly changes the parameters of intermediate secretion, of the salivary conditioned reflexes, without influencing unconditioned ones. Unilateral stimulation disturbs the achievement of positive and inhibitory conditioned reflexes to a greater extent than bilateral one. Difference between the effects of low- and high-frequency stimulation has been revealed.     

The role of the pallidum in regulating cortical activity]

Bilateral ablation of the pallidum halves the duration of extinction of conditioned motor food reflexes and contributes to 30 to 50% extinction of the electro-defensive reflexes. Pallidum functional depression by potassium chloride or novacaine leads to a temporary total depression of conditioned motor food reflexes. Depending on the frequency of pallidum stimulation, synchronization or desynchronization of the cortical bioelectrical activity is observed. Ablation of the pallidum in anaesthetized cats results in a high amplitude and low-frequency cortical activity. Injection of large doses of potassium chloride into the pallidum results in a forced running forward which lasts 30 to 40 min. The pallidum is considreed as a structure controlling the cortex activity, which takes part in the mechanisms of sensory information processes in the course of adaptive behaviour.     

The role of the temporal areas in conditioned reflex activity following section of the brachia of the inferior colliculi]

The role of the neocortex temporal areas in the closing function was studied in chronic experiments on cats in the norm and after section of the posterior colliculi brachia. The techniques of functional elimination of the temporal neocortex by cold and section of the posterior colliculi brachia were used. Functional elimination of the cortical temporal areas prevents formation of a stable conditioned reflex in the first twenty sessions with cooling. Conditioned reflexes elaborated after section of the posterior colliculi brachia are not manifested in the case of cooling of the temporal areas throughout the period of observation (18 sessions). At the same time the conditioned reflexes elaborated before the section, are restored quite rapidly (five to six sessions). Hence, the neocortex temporal areas are more important for setting up conditioned connections than for their preservation and the use of connections previously elaborated.     

Significance of the relative position in space of associated stimuli for formation and performance of motor conditioned reflexes

In experiments on cats the rate of formation of conditioned reflexes to sound (running to the feeding trough) depended on the spatial interrelations of the paired stimuli: the closer the source of the conditioned signal to the feeding trough, the sooner the formation of the conditioned reflex. It has been assumed that during formation of a conditioned reflex the closing of connection between conditioned and unconditioned stimuli is also attended with the closing of connection between the spatial parameters of the paired stimuli. Experiments with inactivation through cold of the temporal area (cortical representation of the vestibular system) of one hemisphere have shown that such a connection is formed in central parts of the vestibular analyser. When the conditioned reflex is elaborated to one feeding trough, the connection is duplicated by both hemispheres; in reflexes to two feeding troughs (i.e. spatial choice) such connections are lateralized in each hemisphere.     

Effect of streptomycin sulfate on the process of higher nervous activity recovery in dogs in the postanesthesia period]

The effect of streptomycin on recovery of the higher nervous activity during the postanesthesia period was studied on 3 dogs with the method of the conditioned reflexes. It was found that streptomycin sulphate administered in a dose of 25 mg per 1 kg body weight induced no changes in the conditioned reflexes of the non-anesthetized animals. After ether anesthesia disorders in the conditioned and unconditioned reflexes, as well as differentiation was observed during the postanesthesia period. On an average they normalized in 7, 6 and 2 days respectively from the moment of anesthesia. When streptomycin sulphate was used during the post anesthesia period, both the strength and the character of the disorders in the conditioned reflexes changed. In this case recovery of the conditioned and unconditioned reflexes was registered in 2 days, while that of the differential inhibition was registered in 3--7 days from the moment of anesthesia.     

Conditioned alimentary motor reflexes in cats following destruction of the scorpula]

Bilateral ablation of the putamen results in temporary disappearance of natural as well as artificial conditioned motor reflexes in cats. Further training is necessary for their reestablishment. Restored conditioned reflexes appear with a long latency. After partial bilateral ablation of the putamen, animals that have been trained not only to press a pedal, but also to make a choice between a right or left feeding tray, lose the latter ability. After the reestablishment of conditioned reflexes, the animal makes a correct choice of side only in 68--70% of cases. After total bilateral ablation of the putamen the animals lose artificial conditioned reflexes. The results suggest that the putamen has a close relation to the mechanisms of learning and memory.     

Experimental neuroses in dogs caused by an increase in the intensity of (light) stimuli conditions

The influence of enhanced intensity of general illumination on conditioned reactions of a different degree of complexity was studied on dogs by the classical method of secretory conditioned reflexes. In most of the dogs, increase of general illumination from 30 to 300 luxes leads to more intensive secretory conditioned and unconditioned reactions, a smaller number of errors in differentiation, and stabilization of parameters of conditioned activity, which testifies to the improved general functional state of the brain. In two animals in the same conditions of the experiment, an experimental neurosis set it, not connected with the complexity of the elaborated activity. It is assumed that the neurotizing agent was the superfluous situational (photic) stimulation which presented excessive requirements to the mechanisms regulating the general functional state of the brain.     

Effects of selective blockade of synaptic transmission in the parafascicular complex on activity of sensorimotor cortex neurons

Neuronal firing activity pattern in the sensorimotor complex and conditioned reflexes produced by blockade of noradrenergic and serotoninergic input to the parafascicular complex (CM-PF) were investigated during chronic experiments on cats in which lever-pressing reflex had previously been set up. Micro-injection of obsidan, a beta-adrenergic blocker and lysergide, a serotonin blocker, were found to produce intensification and inhibition, respectively, of neuronal spontaneous firing activity in the sensorimotor cortex, with both blockers having a similar (inhibitory) effect on neuronal response induced by conditioned acoustic stimuli. Blockade of monoaminergic inputs to the CM-PF temporarily suppressed execution of the conditioned reflex and the non-conditioned reflex of lever-pressing (for 30–60 min). The study concludes that the pattern of effect produced by the monoaminergic system on the sensorimotor cortex is largely determined by indirect as well as direct agents and that such effects are mediated by neurons belonging to the CM-PF complex of the thalamic nuclei.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 3, pp. 327–336, May–June, 1990.     

The influence of electrocoagulation of the septum and section of the entorhinal cortex on general behaviour and memory in cats

In chronic experiments on cats it was shown that the lesion of the medial part of the septum does not result in the "septal syndrome"; the ratio of the different sleep-wakefulness cycle phases remains within the baseline values; the acquisition, retrieval and extinction of instrumental alimentary conditioned reflexes proceed normally; the delayed conditioned reflexes are impaired. Massive septal lesion, including its lateral part, leads to the development of the "septal syndrome"; there are changes in the structure and percentage of the different sleep-wakefulness cycle phases; the acquisition and extinction of instrumental alimentary reflexes with the sound discrimination are markedly retarded; the performance of delayed conditioned reflexes is completely destroyed. The section of the entorhinal cortex produces an increase in the number of repeated errors and perseverative movements during performance of instrumental alimentary reflexes, the deceleration of the acquisition and extinction of instrumental alimentary reflexes, complete disturbance of the delayed conditioned reflexes and does not affect the sleep-wakefulness cycle. The problems of the role of the hippocampus and its main inputs in the regulation of the short-term operative memory in the "pure form" as well as the significance of the descending influence of the hippocampus on the regulation of general animal behavior were also discussed.     

Physiologic characteristics of systems of conditioned connections during urgent formation of a program of action]

Examination of preschool age children has shown that instantaneous formation of a system is possible only on the basis of integration of conditioned reflexes, which are differentiated by the nature or strength of reinforcement. Integration of previously elaborated conditioned reflexes is more successful if the initial systems of conditioned connections were in a state of conditioned tonic excitation of an optimal strength. Uniformly strong or uniformly weak stability of all reflexes in the system renders it inert, hence makes it a poor basis for instantaneous formation of a new system.     

Features of the formation of conditioned secretory reflexes in response to the stimulation of different areas of the caudate nucleus of the dog

Properties were studied of elaboration of conditioned alimentary secretory reflexes to threshold electric stimulation of the caudate nucleus in dogs. The rate of formation of such a reflex and its magnitude were considerably lower than in reflexes elaborated to distant stimuli. Latencies were longer; dynamics of conditioned and unconditioned secretory reactions was similar to that of reflexes to a weak stimulus--light. The motor component of the conditioned alimentary reaction, as a rule, was absent. Characteristics were revealed of formation of alimentary reflexes to stimulation of the dorsal and ventral parts of the head and body of the caudate nucleus.     

Characteristics of higher nervous activity in the suslik Citellus fulvus during its active period

In experiments on active ground squirrels, it was possible to form motor defensive conditioned reflexes and to re-arrange the conditioned reflexes from visual and auditory analysers. It was originally demonstrated that repetitive alteration of the informational content of the conditioned stimuli results in neurotic disturbances in animals.