Dynamics of the formation, reproduction and recognition of trace conditioned reflexes to positive and negative stimuli

The dynamics of formation, reproduction, and recognition of trace conditioned reflexes to positive and differentiation stimuli was studied on subjects of 15-17 years old. Formation and reproduction of such reflexes was found to occur under a close interaction of both levels of the higher nervous activity--recognized and unrecognized levels. Recognized reactions prevailed on unrecognized ones in cases of involvement of active attention. On the basis of this fact, the formation and reproduction of trace conditioned reflexes to positive stimuli has been supposed to occur with an active participation of the left hemisphere. The right hemisphere apparently plays a leading role in formation and reproduction of trace conditioned reflexes to differention stimuli to which the attention of the subjects was not fixed.     

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.     

Spatial-temporal synchronization of cerebral biopotentials and the problem of the brain's activity as a whole

The author compares the results of his own investigations into the influence of instantaneous and multiple reversible (cold) inactivation of the neocortex on the manifestation and elaboration of conditioned reflexes in cats with dynamic characteristics of spatial-temporal synchronization of biopotentials in the cortex and subcortical formations at different stages of formation and manifestation of the conditioned reflex in animals, and in different functional states (emotions and mental stress) in humans, as presented in the studies by M.N. Livanov and coworkers. It has been stressed that different experimental approaches reveal the one principle of brain functioning, its integral involvement in any purposeful activity.     

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.     

Changes in trace reactions of sensorimotor cortex and putamen neurons as affected by haloperidol

Experiments on conscious rabbits were made to elaborate motor conditioned reflexes through pairing stimuli with electrocutaneous reinforcement applied every 30 s. Neuronal activity in the sensorimotor cortex and putamen was recorded during formation and reproduction of the conditioned reflexes before and after haloperidol injection (0.2 mg/kg i. v.). In the putamen, haloperidol increased the number of neurons exhibiting trace conditioned activity and made the intensity and duration of these processes rise. The changes seen in the sensorimotor cortex were opposite in nature. Inhibition of trace conditioned activity in the sensorimotor cortex depended mainly on the decreased amplitude of the reaction conditioned component. The role of the dopaminergic system in the interaction of the neostriatum and sensorimotor cortex and in formation and reproduction of trace conditioned activity of both the structures is discussed.     

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.     

Association by Synaptic Facilitation in Highly Damped Neural Nets

Cognitive functions are sought in a homogeneous, randomly connected net of neuron-like elements. Information is assumed to be contained in the instantaneous states of the system, which specify the firing states (off or on) of each neuron in the net. The hypothesis of synaptic facilitation is assumed to be the basis of learning and memory. Owing to the high degree of damping no reverberations occur in the net. However, close analogies can be found between the performance of the net and known association functions of the cerebral cortex, among them various types of conditioned reflexes. The data are obtained by a combination of mathematical analysis and computer simulation. It is emphasized that the biological entity simulated by this model is at best a limited component of the cerebral cortex.     

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.     

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.     

Tonic component of the conditioned reflex process and its functional role

Tonic background activity of 266 neurones in the hippocampus and different neocortical areas was studied in freely moving rabbits in the process of defensive and food instrumental conditioned performance and during switching-over of instrumental and classical food and defensive reflexes. Associations of CS and reinforcement evoke background activity changes in most of recorded cortical neurones preceding the development of other conditioned manifestations. Conditioned reflex was performed only after reaching the background firing rate of almost every examined neurone optimal for its realization. The performance of different conditioned reflexes was associated with different background activity levels of cortical neurones. The above mentioned data form the experimental basis for the identification of the tonic component in conditioned process which reflects tonic character of temporary connection formation and function.     

Formation of combined stereotypes of systems of secretory conditioned reflexes

A rhythmic stereotype, followed by a rhythmic-mozaic one of positive and inhibitory conditioned secretory reflexes were successively elaborated in dogs with stabile stereotype of three heteromodal randomely organized systems. Thus a combined stereotype was formed of five randomely and stereotypically organized systems of conditioned reflexes, achieved at intervals of 24 hours or longer in a regular sequence. It has been shown that in the course of formation of the combined stereotype the general functional state (tone) of the cerebral cortex is enhanced. The preliminarily formed specialized systemic nervous process with a similar structure is of major importance for the rate of formation of the complex rhythmic-mozaic stereotype.     

The relationship between the dose of caffeine and the magnitude of conditioned reflex salivation in dogs]

Statistical estimates carried out on a comprehensive experimental material of the archives in the Laboratory of physiology of nervous system types at the Pavlov Institute of Physiology, USSR Academy of Sciences, made it possible to plot average static characteristics of changes in the magnitude of positive conditioned reflexes in dogs, depending on the dose of caffeine. It appeared that conditioned reflexes decreased to some extent after a 0.01 g dose; within the range of 0.05 to 1 g doses, the magnitude of reflexes increased to the maximum; within the range of 0.1 to 0.5 g, their magnitude diminished from the maximum to the normal level, and, finally, a dose of 0.5 g or greater resulted in a drop of the magnitude of the reflexes below the normal level.     

Conditioned reflex activity of pigeons as affected by an infra-low frequency alternating magnetic field

In experiments on 35 pigeons formation and realization was studied of alimentary motor conditioned reflexes under the influence of alternating magnetic field (AMF) with a frequency of 5 and 8 Hz and induction 5100 nTl. It has been found that under the action of such AMF, the percent of adequate responses lowers and the time of motor reaction during execution of motor alimentary conditioned reflexes and of delayed reactions increases. Realization of delayed reactions is disturbed more significantly than that of the present conditioned reflexes. AMF with a frequency of 8 Hz influences more expressively the pigeons conditioned activity in comparison with 5 Hz frequency.     

Phase Changes in EEG as Indications of Formation of Cortical Coordination

During the formation of positive and negative conditioned reflexes, the stimulus ("indifferent" positive or negative) acquires a dual biological significance. It becomes simultaneously a stimulus of functionally incompatible reflexes, giving rise to antagonistic interaction between them, and to their cortical coordination.     

Effect of tryptophan and its metabolites on the conditioned reflex activity of the honeybee

The effect of tryptophane and its derivatives on the rate of elaboration and transformation of conditioned reflexes (CR) to odour, with alimentary reinforcement, was studied in wild bees under two conditions: free movement of the bee or its immobilization (stress situation), by means of genetic models (mutations, successive blocking stages of kynurenin path of tryptophane metabolism). It was shown that mutations eliciting accumulation of free tryptophane and serotonin in the hemolymph of the bees and creating a deficit of kynurenins accelerate the transformation of conditioned reflexes and aggravate the depression of conditioned activity usually elicited in wild bees by monotonous prolonged presentation of conditioned signal. The injections of tryptophane and serotonin (5 mg) produce the same action. Mutations, eliciting accumulation in the hemolymph of the kynurenins (kynurenin and 3-hydroxikynurenin) accelerate, in conditions of immobilization, the formation of conditioned reflexes and delay the process of their transformation, and also contribute to maintainance of a higher (in comparison with the norm) level of the conditioned activity under monotonous presentation of the signal. The same action is produced by the injection of 1 mcg kynurenin.     

Changes in the cholinosensitivity of sensomotor cortex neurons during conditioned reflex extinction]

Characteristics of neuronal responses of the sensorimotor cortex to ionophoretically administered neuromediators (acetylcholine, L-glutamate) were studied in rabbit in the course of extinction of conditioned defensive reflex. In the majority of neurones the extinction of the conditioned reflex is accompanied by a drop of cholinosensitivity. In a number of neurones the extinction of reflexes either does not change the reaction to acetylcholine, or enhances it. The analysis of these reactions permits to assume the existence of a group of neurones directly involved in the formation, fixation and storage of the temporary connection.     

Newly revealed range of action in the preparation derinat: Mnemotropic effect

Mnemotropic effect has been revealed in the action of Derinat, a biologically active compound of natural origin, on the formation of conditioned reflexes of active and passive avoidance. Derinat accelerates the elaboration of conditioned reflexes. This effect manifests itself already at initial stages of the elaboration, which resembles the effect produced by nootropics.     

Motor alimentary conditioned reflexes and delayed reactions in dogs following destruction of the caudate nucleus]

The characteristics of formation and achievement of motor conditioned reactions were studied in seventeen dogs before and after the lesion of head or body of the caudate nucleus. It has been shown that the degree of higher nervous activity disturbances depends on the localization of injuries in the nucleus, and on the complexity of the tests used. The caudate nucleus exerts a modulating effect on the parameters of motor conditioned reflexes and takes a direct part in the structure of delayed reflexes. Lesion of the caudate nucleus body is attended with more serious disturbances of higher nervous activity than lesion of its head.     

Individual typologic characteristics of the open-field behavior of rats

By means of ethograms record and analysis, connection has been studied between the properties of rats behaviour organization in the open field, determining the level of behaviour entropy in this test, and the speed of conditioned reflexes formation in the Skinner chamber. According to behaviour entropy level the rats are significantly divided into four groups; the lowest speed of conditioned reflexes formation in the Skinner's chamber is observed in the animals of the first (low entropy) group, the highest--in the fourth (high entropy) group. The obtained data are discussed according to Pavlov's concepts on the characteristics of the basic nervous processes, determining individual-typological characteristics of the higher nervous activity of the animal. Conclusion is made that division according to the level of behaviour entropy in the open field test may serve as a safe method of express-estimation of the animals abilities to conditioned habits formation.     

The effect of a decrease in cerebral noradrenaline concentrations on the formation and fixation of temporary connections]

A sharp drop in the noradrenaline content (Na) in the brain of mice does not prevent the elaboration and fixation of relatively simple conditioned reflexes, but considerably disturbs the elaboration of more complex conditioned reflexes with delayed reinforcement. The decrease in the NA content in the brain does not appear to influence directly the process of consolidation of temporary connections; impaired fixation of relatively more complex forms of temporary connections is of a secondary nature and is due to disturbances in their formation.