Relation between the dynamics of a species-specific motor reaction and the duration of diencephalic stimulation

Species-specific reaction of thumping behaviour with the hind limbs in response to electrical stimulation of the ventromedial, dorsomedial and caudal parts of the hypothalamus was studied in chronic experiments on rabbits. Reaction of avoidance dominated during current action of various durations (1-20 s). The specific reaction under study appeared after the termination of stimulation and lasted for 30-120 s. The number of kicks in response to single stimulation depended on its duration (T). With T rising from 1 to 10 s, the number of kicks increased; with T being equal to 20 s, it decreased. The latency of the first kick after the termination of stimulation regularily increased with increase of its duration, and reaction intensity maxima shifted to the right along the axis of time. Possible mechanisms of limb kicking behaviour are discussed based on a transition of avoidance reaction during stimulus action to emotional reaction in post-stimulus period.     

Change in the signal properties of a conditioned stimulus during two-way avoidance conditioning in rats

Acquisition of two components of conditioned active avoidance behavior by rats was studied. First presentations of electroshock evoked a number of different behavioral reactions. However, after five trials many rats learned to escape punishment running away to another part of a shuttle-box. The efficiency of the avoidance reaction conditioning significantly depended on the ability of an animal to learn the correct escape reaction to the unconditioned stimulus. However, some animals were incapable for acquisition of the conditioned reaction despite their high level of successful escapes. Increase in the number of negative reactions to the conditioned stimulus (light) at the next stage of learning suggests that the conditioned stimulus becomes the signal of forthcoming punishment. The ability of an animal to identify the conditioned stimulus as a signal significantly affected the efficiency of conditioned avoidance acquisition.     

Reflection of the process of conditioned reflex formation in shifts of the steady potential level]

In chronic experiments on rabbits with non-polarizable electrodes shifts of steady potential level (SPL) are recorded from the brain surface during extinction of the orienting reaction and formation of a conditioned defensive reflex. During each of these processes they have their typical parameters and are respectively denoted by the author as: orienting (appearing in response to a new stimulus), conditioned (to a signal atimulus), unconditioned (to an electro-cutaneous stimulus) and trace SPL shifts (developing after stimuli pairing). Trace shifts are the earliest SPL shifts originating as a result of pairing. They are manifested more regularly, than conditioned ones, considerably exceed them in amplitude, may differ from them in their sign and reach maximum values in a few seconds after the pairing. It has been assumed that formation of conditioned temporal connections depends above all on the appearance of a new kind of activity, resulting from pairings and reflected in the SPL trace shifts. This activity possibly constitutes the neurodynamic and metabolic processes underlying memory consolidation.     

Inhibition of a conditioned reflex evoked emotional response as an "instrument" of avoidance

A method has been elaborated of training the human subjects to avoid electric shocks by overcoming the "fear" caused by a warning signal. A previously elaborated differentiated conditioned skin-galvanic response (SGR) to a sound stimulus served as a criterion of the emotional reaction. The SGR was projected on an oscilloscope screen. The electric shock was automatically delivered at the moment when the amplitude of the conditioned SGR exceeded the level marked on the screen. The subject was instructed, by overcoming the "fear", to retain the SGR amplitude below the level. If the subject succeeded in overcoming the conditioned SGR to the signal, the shock was not delivered. Since, the suppression of the conditioned SGR served as a "instrument" of avoidance and became consolidated as a habit based on a positive reinforcement. The subjects developed a stable attraction to repetition of training sessions in which they learned to suppress the "anxiety" caused by a signal of "threat".     

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.     

Evoked potentials during elaboration of fine differentiations

The paper deals with the character of changes in the EP form recorded from the visual cortex of a rat during elaboration of a system of positive and negative (with different degree of precision) conditioned defensive reflexes. It has been shown that in a state of a consolidated habit of pain stimulus avoidance in a shuttle box a negative component with peak latency up to 70 msec develops in EP to the differentiation stimulus of 0.5 c/s. This component is much less pronounced to the 2 c/s conditioned stimulus. When a more precise differentiation stimulus (1 c/s) was presented to the animal in this state the development of the studied component depended on the subsequent behavioural reaction: it developed if the animal reacted in the same way as to the differentiation stimulus. This fact suggests that the generation of this component is connected with the inhibitory processes developing at the time when the animal is choosing its behavioural reaction.     

Analysis of the formation of systems of conditioned reflexes to time in rabbits]

Experiments on rabbits carried out by the food-procuring conditioned reflex method have shown that conditioned reflex systems to "pure" time can be elaborated, provided that conditioned stimulus is presented at regular, though different time intervals, following one another in a fixed sequence. The complexity of elaborating such systems to time is determined by the number of signal time intervals in the system, their different length, and their sequence. The formation of conditioned reflex systems to time is characterized by definite stages.     

Activity of neurons in the pedunculopontine nucleus in conditioned instrumental appetitive reflex

Activity of 91 neurons in the compact and diffuse parts of the pedunculopontine tegmental nucleus (PPTg) was recorded in freely moving rabbits during execution of instrumental appetitive conditioning. Of the recorded neurons, 37.4% changed their activity in response to a conditioned stimulus, which is the evidence for the PPTg involvement in instrumental conditioning. Excitatory conditioned neuronal responses to the conditioned stimulus and food reinforcement significantly prevailed over inhibitory reactions. Neuronal responses to the conditioned stimulus were classified in several basic patterns reflecting stimulus effects, structure of the behavioral act, and reinforcement properties. These reactions indicate the involvement of the PPTg in attention, motor learning, and reinforcement. The revealed differences in associative reactive properties of the compact and diffuse parts of the PPTg to the conditioned stimulus and reinforcement point to the functional heterogeneity of this structure and suggest the leading role of the cholinergic part of the PPTg in instrumental appetitive conditioning and reinforcement as well as the essential contribution of the diffuse part into classical appetitive conditioning.     

Changes in the configuration of conditioned reactions of visual cortex neurons during changes in reinforcement parameters]

In order to study the influences of controlled changes of defensive integration on the activity of visual cortical units their responses to a conditioned light flash and electric cutaneous stimulation with a 600 msec interval between them were recorded in experiments on alert rabbits. It has been shown that in a third of the neurones the types of reaction to light flashes and electric stimuli coincide. The changes in parameters of the reinforcing shock led to a changed response of most cells to the conditioned photic stimulus and electric stimulation. The changes may have affected units which produce any activation phase, including cells with activity characteristic of detectory ("simple" and "complex") visual neurones. The data obtained suggest that the special function of the visual cortex is used in different ways in systemic mechanisms of conditioned and unconditioned defensive acts and that the integrated system of a behavioral act exerts control both on the use of the unit in a certain systemic process and on its receptive field.     

The humoral link in the mechanism of formation of conditioned food refusal in the edible snail

Effect was studied of hemolymph of snails-donors with conditioned food refusal, on learning the same habit by snails-recipients. Facilitation was observed of the recipients' learning depending on the quantity of injected hemolymph and the type of conditioned stimulus. The hemolymph of pseudo-conditioned donors inhibited the learning of intact snails-recipients. The possibility is suggested of appearance in the hemolymph of conditioned snails of one or several chemical factors, capable to facilitate elaboration of the same conditioned reflex.     

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.     

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.     

The role of the lateral and medial hypothalamus in reproducing a motor reaction as the signal during the acquisition of classical conditioned reflexes]

In experiments on three dogs there was shown that testing electrostimulation of the lateral hypothalamus reproduced the motor reaction which is a signal stimulus at elaboration of classic alimentary conditioned reflexes (CRs) and did not reproduce it at elaboration of classic defensive CR. Testing electrostimulation of medial parts of the hypothalamus reproduced, as LH electrostimulation the "signal" motor reaction, but in less percentage of cases, during elaboration of classic alimentary CRs and did not reproduce it at elaboration of classic defensive CRs. The reproduction of the signal motor reaction at LH electrostimulation is connected with activation of backward conditioned connection from motivation structures of the hypothalamus to representation of the signal stimulus in the motor cortex.     

The relationship between a conditioned slow negative potential and focused attention]

A conditioned slow negative vertex potential (CSNP) was studied in the interval between two stimuli: anticipatory and trigger, under different experimental conditions, namely; in response to a trigger stimulus the subject was to press an operating key; or to memorize the number of trigger stimuli; or to respond to the trigger stimulus by pressing the key and memorizing the number of anticipatory stimuli. A sound, geomatrical figures and separate words flashing up on a screen were used as stimuli. All of them were presented both as anticipatory and trigger signals. If a sound was used as an anticipatory stimulus, and a word as trigger one, the recorded CSNP was at its maximum in the case of a simple motor reaction, and at its lowest during retention. When the stimuli interchanged, was drawn to the anticipatory verbal stimulus, the CSNP amplitude diminished and the latency became shorter. The dependence of SCNP parameters on the subject's attention drawn to the anticipatory resp. trigger stimuli is discussed.     

The dynamics of latent inhibition in rats under the action of substance P]

The role of substance P in latent inhibition was studied in experiments on rats. Administration of neuropeptide during pre-exposition of conditioned stimulus and before conditioning disturbed all signs of latent inhibition: level of reproduction, retention and resistance to amnestic action of conditioned reaction in the task of passive avoidance. Single administration of haloperidol before learning prevented the disturbance. Significance of hyperfunction of substance P in selective attention and pathogenesis of schizophrenia is discussed.     

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.     

Excitability cycles of direct cortical responses during elaboration of conditioned defense reflexes in dogs]

Direct cortical responses (DCRs) to paired stimuli were studied in chronic experiments in dogs during elaboration of classical and instrumental defensive conditioned reflexes. The DCRs were recorded with 20 to 250 ms intervals between stimuli. Paired and single electrical stimulations of the middle suprasylvian gyrus given with a frequency of one per second were used as conditioned stimuli and were reinforced in a similar way. During electrical cutaneous stimulation of the dog's paw and to an even greater extent during isolated action of the conditioned stimulus the initial negativity of the testing DCR became shorter and the degree of its depression diminished. In the case of a following period of facilitation, its degree became greater. It was higher at a distance of 4 to 5 mm from the point of stimulation than at a distance of 2 to 3 mm. During isolated action of the conditioned stimulus, the degree of facilitation was higher than at the period of the possible action of the unconditioned stimulus. The greatest shorterning of the DCR excitability cycle was observed immediately before and during the conditioned lifting of the dog's paw. Excitability cycles of DCR, and possibly of other evoked potentials as well, are a more sensitive indicator of the function state of the cerebral cortex than responses to single stimuli. For this reason it appears promising to use them in studying conditioned reflexes.     

The dependence of the neuronal reactions of the sensorimotor cortex to a simultaneous complex stimulus on the level of the differentiation of its components]

On alert animals the change was studied of the neuronal activity of the sensorimotor cortical area of cats brain in dependence on the level of differentiation of the components of simultaneous heteromodal complex stimulus. According to the character of this dependence and a number of other parameters two groups of neurones were singled out in the sensorimotor cortex. It was shown that parameters of reactions of all recorded neurones of the sensorimotor cortex to the positive conditioned signal were the first established after consolidation of the animal conditioned motor activity. In the course of elaboration following parameters changed: expressiveness, intensity, duration and value of latency. Reactions of neurones of both groups to the inhibitory stimuli were stabilized only after consolidation of the habit of differentiation. Responses of the first group neurones changed only by the pattern of discharge, while the responses of the second group neurones could change by expressiveness of response, its sign, duration and value of latency. Oscillations of the differentiation level after finishing of the elaboration of inhibitory conditioned reactions affected only the responses of the second group neurones to complex components.     

Generalization of learned taste aversions in rabbits: similarities among gustatory stimuli

Although rabbits have been used in a number of electrophysiologicaland anatomical studies on the gustatory system, there have beenfew behavioral experiments on these animals and these have beenlimited to studies of taste preference. The similarities amonga number of gustatory stimuli were assessed in rabbits by measuringthe generalization patterns in a conditioned taste aversionexperiment. Rabbits were trained to take their daily rationof water within a 30-min session, during which the number oflicks per 10-s presentation of a drinking tube could be recorded.During one of these sessions, one of 12 stimuli (sucrose, fructose,Na-saccharin, NaCI, NaNO₃, Na₂SO₄, KC1, NH₄C1, CaCl₂, HC1, QHC1or urea) was presented, followed by i.p. injection of LiCl toproduce a conditioned taste aversion. Animals were then testedwith all of the stimuli and the amount of suppression of lickingwas used as a measure of stimulus generalization. The patternsof generalization were compared for the test and conditioningstimuli separately. Some nonreciprocities were seen betweenthe conditioning and test stimuli, which reflected the occurrenceof multiple taste qualities and the tendency for aversions togeneralize more to stronger stimuli than to weaker ones. Principalcomponents analysis of the stimulus relationships showed thatrabbits responded to these stimuli in a fashion similar to thatof other mammals, including humans. Within the principal componentssolution, there were strong similarities among the sugars, thesodium salts, the nonsodium salts and the bitter-tasting stimuli.     

慢性动脉血压监测模型在惊恐条件反射中的应用

目的：探索一种新的、可靠的模型,用于惊恐条件反射的相关研究。方法：通过使用条件刺激(声音)和非条件刺激(足部电击)相结合的方法,可使动物对条件刺激产生惊恐反应。同时对动脉血压进行长期监测并测定利多卡因阻断杏仁基底外侧核群前后的血压变化。结果：该惊恐条件反射建立后(需经4d训练),单独给予动物条件刺激即可引起血压明显升高。我们将它作为条件反射已形成的标志。此时,用利多卡因阻断杏仁基底外侧核群的作用,单独给予动物条件刺激不再引起血压明显升高。结论：慢性动脉血压监测模型在惊恐条件反射的研究中是一种可靠的动物模型。