The role of the lateral and medial hypothalamus in reproducing food and escape instrumental reactions]

In experiments on two dogs it has been found that testing electric stimulation of the lateral hypothalamus reproduces instrumental movement in case of elaborated alimentary instrumental conditioned reflexes (CR) to a tone and does not reproduce it at elaborated acid-defensive instrumental CR. Under testing electric stimulation of the medial hypothalamus the instrumental movement practically is not reproduced neither in alimentary nor in defensive situation. Appearance of instrumental movement at LH electro-stimulation in alimentary situation is connected with activation of backward conditioned connection from motivation "alimentary" LH centre to representation of this movement in the motor cortex.     

Activity of 3-neuron cortical microsystems in the cat during conditioned reflex switchover

Multiunit activity in two projection cortical areas (visual and motor) was studied in cats at conditioned switch-over of defensive and alimentary responses to electrostimulation of the visual pathways. Interneuronal relations of three-neuronal cortical microsystems (intra-analyzer connections) and relations between microsystems in the visual and motor cortical areas (inter-analyzers connections) were analysed by the method of crosscorrelation of action potential trains. Similar interneuronal relations were revealed in the motor microsystems and different relations were found in visual ones at elaboration of conditioned switch-over. This apparently indicates the leading role of the cortical projection of the signal stimulus in integration of adaptive behavioural act. On the other hand, the presence of common bonds for alimentary and defensive situations as well as of specific ones for each of them was shown in the distribution of interneuronal connections between the analyzers. The former apparently provide for the realization of the conditioned effector movement of the animal occurring in both situations with participation of the same effector organ (the tongue) The latter determine the character of the specific adaptive reaction.     

Functional organization of limbic brain structures during conditioned reflex activity in the dog

In experiments on 3 dogs it was shown that instrumental defensive conditioned reflex (CR) to electrical stimulation of the hippocampus is generalized within the limbic system (LS). The rate of generalization depended on the place of testing stimuli in LS. Stimulation of the medial parts of LS at the stage of stabilized initial reflex did not produce the generalized CRs, while they appeared distinctly in response to stimulation of the lateral parts of LS. In the process of elaboration of heterogeneous CRs (defensive and alimentary) to electrical stimulation of the hippocampus, generalized conditioned reactions from some brain structures appeared in both situations to the same degree while from other structures--with considerable differences. These data point to a possible participation in the genesis of the generalized CRs both of signal and reinforcing brain mechanisms.     

Effect of dalargin on the processes of memory and learning in the rat

In experiments on rats, the influence was studied of dalargin on the elaboration and preservation of various homogeneous and heterogeneous conditioned reflexes (CRs) elaborated in single and multiple pairings. The effect of dalargin on the processes of learning and memory was compared with the action of the peptide on the activity of hypothalamic neurones. Administration of dalargin delayed the elaboration of maze defensive CRs and practically did not affect the elaboration of two-way avoidance. The preservation of CR also deteriorated under the influence of dalargin. Administration of dalargin 10 min before the CRs testing did not prevent their reproduction. When using CRs elaborated in a single pairing, dalargin disturbed the preservation of the drinking CR and improved that of passive avoidance CR. Dalargin in this dose affected the emotional state of animals in the open field and did not significantly affect their motor activity. Dalargin suppressed impulse activity in 17 out of 22 tested neurones of the lateral hypothalamus, with maximum effect in 20-50 min after its administration. The obtained data show that the character of dalargin action on the elaboration of CR and mainly on its consolidation, depends on the character of the elaborated CR and is probably due to great extent to the effect of the peptide on the brain emotional mechanisms.     

Instrumental heterogeneous responses to 2 successive complex stimuli with a common initial stimulus in the dog

Formation and achievement of heterogenous instrumental reflexes to two consecutive complex stimuli was studied in dogs. Under the action of conditioned complex stimulus tone--Pause--tone, the dogs may be trained not to have a motor response to the first tone presentation, but perform alimentary instrumental reaction only to its repeated administration. Introducing into the experiment not only alimentary but also defensive complex stimulus stone-pause--light resulted in a change in animal's reactions in such a sequence: at first alimentary instrumental reaction was disinhibited under the action of the preparatory stimulus and during the pause, then bieffector responses appeared, further on in most of the dogs motor defensive reactions mainly took place. Trigger stimuli evoked the adequate instrumental reaction.     

The effect of ablation of the caudate nucleus on the alimentary zone of the lateral hypothalamus]

A conditioned food-procuring reaction previously elaborated to an acoustic stimulus was reproduced in chronic experiments on six cats by means of direct electrical stimulation of the posterior parts of the lateral hypothalamus. Folloiwng extensive bilateral electrolytic ablation of the caudate nucleus, conditioned food-procuring reaction to the stimulation of the hypothalamus could not be reproduced for 40 to 70 days. The conditioned foor-procuring reflex to the acoustic stimulus disappeared for 14 to 30 days to be subsequently spontaneously restored. After caudatotomy, a diminution of the average amplitude of background oscillations and of evoked potentials to acoustic stimuli was recorced in the examined zones of the lateral hypothalamus. The part played by the caudate nucleus in the processes of alimentary behaviour activation is discussed.     

Effect of neurotizing exposures on conditioned reflex activity in the late postresuscitation period in rats

In white rats resuscitated after 10-minutes stop of the blood circulation, conditioned switching over was elaborated on the basis of alimentary and defensive instrumental reflexes and the effect was studied of neurotizing influences. Single application of electrocutaneous pain stimulus in alimentary situation ("collision") led to more expressed disturbances of conditioned activity in resuscitated rats than in intact ones. Differentiation of a signal different from the positive conditioned stimulus only by the height of the tone, was practically not elaborated in resuscitated rats, and the disturbance of the conditioned alimentary reflex to the reinforced signal appearing during differentiation elaboration, was manifest in them to a greater degree. The obtained data testify that even a short-time brain ischemia, accompanied by a fast and full restoration of the neurological status, leads to functional defects of the CNS appearing at subsequent neurotic influences.     

The possibility of elaborating conditioned reflexes on the basis of emotional reactions evoked by electrical stimulation of limbic structures]

In experiments on cats with chronically implanted electrodes a conditioned stimulus (200 c/s tone) was paired with electrical stimulation of limbic structures, which produces pronounced emotional behaviour: defensive, aggressive, alimentary or drinking reactions. It has been shown that conditioned reactions are not elaborated on the basis of electrical stimulation, which activates alimentary, drinking or aggressive behaviour. Neither is a conditioned reflex formed to the combination of sound and stimulation of the brain structures, which inhibits alimentary behaviour. A distinct conditioned fear reaction sets in as a result of combination of sound and electrical stimulation of brain structures, which evoke defensive behaviour. The data obtained are analyzed in the light of the significance of natural requirements of the organism for the elaboration of conditioned reflexes.     

The effect of hypothalamic stimulation on food choice with rats maintained on different water-salt rations]

Electrical stimulation of the lateral hypothalamus in rats induces an increase of water intake and decrease of thresholds of eaten salty food. These effects are displayed in control animals and under salt diet and water deprivation. The hypothalamus stimulation relaxes the effects of "psychic distillation" of food which occur during spatial coincidence of conditioned signal of insipid food with salty reinforcement. Besides, the trans-switching of signal significance of conditioned stimuli connected with insipid and salty reinforcements is accelerated. The electrostimulation of the hypothalamus accelerates the elaboration of conditioned aversion of salty food inhibition of conditioned runnings toward corresponding food-box, and intensifies the existent state of thirst transforming it in the dominant motivation.     

Changes in the electrical activity of the hippocampus during elaboration of an inhibitory reaction in the dog

A conditioned alimentary instrumental reflex was elaborated in three dogs with chronically implanted electrodes to a consecutive complex conditioned stimulus consisting of two equal acoustic stimuli separated by a pause. At first, the animals reacted with motor reactions during the whole action of the complex signal. Then inhibition of reaction was elaborated at first in pause and then in response to the preparatory stimulus. In the process of stabilization of inhibition, there was an increase of similarity of spectral composition of hippocampal theta-rhythm with the values obtained in the inter-signal period. Conclusion is made that the hippocampus is not a structure necessary for the elaboration of internal inhibition. The frequency of hippocampal theta-rhythm may serve as a characteristic of the property called in Pavlov's school mobility of the nervous system.     

Dynamics of the spectral composition of the hippocampal theta-rhythm in the dog during switching-over of heterogeneous instrumental reflexes

In two dogs with electrodes chronically implanted in the hippocampus, hippocampal electrical activity and the heart rate were recorded in the process of elaboration of a conditioned switch-over of operant alimentary and defensive responses. Averaged computerized spectral characteristics of hippocampal theta-rhythm were essentially different between the alimentary and defensive situations in intersignal period as well as during the action of triggering conditioned stimulus. Individual differences in the dominant frequency of bioelectrical activity were observed. The animal with a higher theta-rhythm frequency elaborated conditioned switch-over of heterogeneous operant responses sooner and more successfully.     

The active electrogenesis of the command neurons in the defensive behavior of the mollusk during conditioning]

In the paper changes of active electrogenesis of the command neurones of defensive closure of snail pneumostome at elaboration, extinction and repeated elaboration of classic conditioned defensive reflex to tactile stimulus was described; the tactile stimulation of other point of the body served as a differentiating stimulus. During the increase of biological significance of conditioned stimulus as a result of learning the stimulation of the command neurones in response to this stimulus was raised. At the same time the neurones showed decreased excitability in response to differentiating stimulus. Possible mechanisms of quick reconstruction of neurones excitability and functional value of PA generation threshold changes were discussed.     

Conditioned reflex and electrical activities of the hippocampus during the random use of heterogeneous triggering stimuli

In dogs with electrodes chronically implanted in the hippocampus, the conditioned activity, heart rate frequency and spectral characteristics of the hippocampal theta-rhythm were studied in conditions of irregular presentation after a preparatory stimulus now of alimentary and now of defensive triggering conditioned stimuli. It is shown that uncertainty of alimentary or defensive reinforcement is a stronger emotiogenic factor than the action of the triggering defensive conditioned stimulus. Changes in electrical hippocampal activity and autonomous activity depend, along with other factors, on forecasted volume of the forthcoming motor activity. The speed of instrumental conditioned reflexes formation correlates with the hippocampal theta-rhythm frequency, typical for the given animal.     

Autonomic correlates of the formation of a functional self-stimulation system

Capability of intracerebral electrostimulation to serve as an unconditioned reinforcing stimulus in classical conditioning was studied in rabbits. Changes of such vegetative characteristics as respiration frequency and ECG were taken as criterion of conditioned response (CR) elaboration. In preliminary experiments, optimal parameters of stimulation maintaining the highest level of instrumental self-stimulation behaviour were found for each of the animals. Isolated presentation of the unconditioned reinforcing stimulus led to the increase of respiratory rate. Such kind of stimulation induced tachicardia in 5 animals, bradicardia in 3 ones, and in the remaining 6 rabbits a biphasic reaction was observed with initial tachicardia changing for bradicardia. Reactions were taken as CRs if they were similar to those to the unconditioned stimulus and appeared at the moment of omitted reinforcement. After 10 pairings of conditioned sound stimulus with positive reinforcement, CR changes of the two vegetative parameters were observed in 21,4 per cent of cases. After 40 pairings CRs were observed in 87,5 per cent of trials for cardiac and in 78,5 per cent cases for respiratory components. The results obtained confirm the idea of validity and efficiency of intracerebral stimulation of self-stimulation zones as a factor of positive reinforcement.     

Generalization of an instrumental defensive conditioned reflex elaborated to electric stimulation of the hypothalamus in dogs

Generalization of defensive conditioned reflexes elaborated to electrical stimulation of the lateral hypothalamus (LH) was studied in four dogs with electrodes implanted in various structures of the limbic system. Electrocutaneous stimulation was switched off when the dog lifted the foreleg to a definite level. Generalization of the conditioned reflex was manifested in different degrees when testing different formations of the limbic system, or testing one and the same structure, but at different stages of conditioning. Two types of generalization were found: the first one--a well pronounced motor reaction, by its latency, level and duration of lifting the foreleg similar to movements appearing in response to the conditioned stimulus; and the second one--low amplitude or short-term movements differing from conditioned ones. The first type of generalization was observed in response to stimulation of LH, contralateral to the point of signal stimulation, of the ventromedial hypothalamic nucleus, the mammillary bodies and the basal, lateral and to a lesser degree, the central nucleus of the amygdaloid complex; the second type--in response to stimulation of the ventral hippocampus, the medial and lateral septum nuclei.     

Integrative properties of parietal cortex neurons of rabbits during the switching of heterogeneous classical conditioned reflexes

The impulsive activity of parietal cortex neurons of rabbits during the elaboration and specialisation of switching-over of alimentary and defensive conditioned reflexes has been studied. There are changes of parietal cortex neurons activity correlated with the stages of switching-over elaboration. The significant differences of the background neurons activity and neurons response to the conditional signal during alimentary and defensive conditioned reflexes have been established. The dominant motivation influences the neurons activity by modulation of background and conditioned activity of neurons. The integrative properties of neurons investigated in switching-over situation are revealed in their ability to summarize the excitation coming to the same sensory input with excitation from different motivational and reinforcement systems.     

Transformation of conditioned responses of the tonic type

A reversal of signal meaning of stimuli signalling experimental situation was performed on dogs with conditioned defensive motor reflexes to clicks: clicks and electro-cutaneous stimulation were stopped, and the animals were started to be given food in the same experimental situation. Reversal of conditioned defensive tonic stimuli to alimentary ones led to a complex of behavioral and electrographic reactions. Isolated click tests showed that signals of experimental situation considerably affect a fully-elaborated defensive motor reflex. At the same time the preparatory role of certain situational elements may be specialized with regard to the components of the conditioned reflex, in particular to the local flexor reaction.     

Intralimbic evoked potentials in the formation of an instrumental food conditioned reflex to hippocampal electrostimulation in dogs]

In dogs with the electrodes implanted in the hippocampus, amygdala, septum and hypothalamus an instrumental alimentary conditioned reflex (CR) was elaborated to electrostimulation of the hippocampus. Intralimbic evoked potentials (EPs) were studied during the elaboration and extinction of this reflex and during stimulations of limbic structures conducted with the purpose of CR generalization checking. Late EP components in the lateral hypothalamus and central nucleus of the amygdala changed during CR elaboration and extinction and in the hippocampus during amygdala testing. In both cases the amplitude of trace positivity and of slow negative wave was less, when during stimulation of the structure an instrumental movement was initiated than at its absence.     

The effect of direct stimulation of the dog lateral hypothalamus on transformation of a passive-defensive situational reflex into an alimentary one]

The behavioral effect of electrical stimulation of the lateral hypothalamus with a current of equal parameters in chronic experiments on dogs depended on the signal significance of the surroundings. Stimulation of the lateral hypothalamus against the background of a defensive situational reflex in dogs which were in an experimental situation for the first time, far from evoking orientation to food and the act of feeding, enhanced the background fear reaction. After transformation of the defensive signal significance of the situation into an alimentary one, stimulation of the lateral hypothalamus began to activate the alimentary instrumental reflex and the act of feeding. However, at first the former was manifested irregularly. Combinations of stimulation of the lateral hypothalamus and achievement of the alimentary instrumental reflex with subsequent reinforcement stabilized and enhanced the alimentary instrumental reflex to the stimulation of the lateral hypothalamus.     

Neuronal activity of the cerebral cortex in cats with conditioned inhibition

Unit activity of the somatosensory cortex was studied in chronic experiments on cats during alimentary instrumental conditioned reflex performance and elaboration of conditioned inhibition (CI). First presentations of the CI signal at the beginning of CI formation caused, due to orienting reaction to a new stimulus, a levelling of the response of the neurones to the positive conditioned signal included into the CI complex. At the stage of consolidated CI, this depression proceeded gradually during the development of conditioned inhibition caused by consecutive presentations of the nonreinforced CI combination. Two groups of neurones were involved in the process of the CI performance: one of them being the same which was activated also in response to positive stimulation during performance of the conditioned response, and the second one being areactive to the positive conditioned stimulus but reducing the frequency of the background activity.