Various neurochemical mechanisms for the production of conditioned reflexes of various biologicals modalities at the level of the caudate nucleus]

Microinjection of noradrenaline in to the head of the caudate nucleus failed to influence the latent time of the conditioned reaction of avoidance and the muscle tone, but limited the motor activity and considerably increased the value and the latent time of the food-procuring reflex. Serotonin failed to influence the latent time of the conditioned defence reflex and did not alter the motor activity of rats; however, it shortened the latent period of the conditioned motor-food reflex and markedly stimulated the food-procuring reaction. Dopamine inhibited the conditioned food and defence reflex, but markedly stimulated the spontaneous motor activity of rats. The data obtained pointed to differences in the neurochemical mechanisms realizing the conditioned reflex reactions of different biological modality at the level of the caudate nucleus of rats.     

Monoaminergic influences of the caudate nucleus on conditioned food-getting reactions in rats]

Influence of microinjections of monoamines and glutamic acid into the caudate nucleus head on conditioned food-procuring reaction was studied in experiments on rats. Dopamine, noradrenaline and glutamic acid prolong the latency of the reflex, while serotonin reduces it. However, all the drugs tested reduce the number of conditioned food-procuring movements. The effects of dopamine are achieved through neurone receptors of the caudate nucleus which are sensitive to haloperidol and chlorpromazine; effects of serotonin are mediated through the D-serotoninoreactive systems, and those of noradrenaline, through the alpha-adrenoreactive systems of the neostriatum neurones. The inhibitory effect of glutamic acid is not due to the action on the serotonino-, adreno-, or dopamine receptors of caudate units.     

EEG analysis of the effect of stimulation of GABAergic structures of the caudate nucleus on the development of the effect of haloperidol

Functional significance of GABA-structures of the caudate nucleus was studied by EEG analysis of the influence of stimulation of these structures on the development of the effect of systemic introduction of the blockader of dopaminergic receptors haloperidol. Microinjections of GABA to the caudate nucleus prevented the suppressing action of haloperidol on food-procuring cats behaviour and led to restoration of the EEG-reaction to conditioned sound stimuli. A conclusion is made about an important role of GABA-ergic structures in the mechanisms of dopaminergic control of the inhibitory function of the caudate nucleus.     

Role of acetylcholinergic structures of the caudate nucleus in mechanisms of inhibition of a conditioned food-getting reflex in the cat

The effect of acetylcholinergic structures stimulation on the acquisition and inhibition of a conditioned food-procuring reflex was studied in cats. Physostigmine injections (0.1 mg/kg) did not facilitate the extinction of the non-reinforced food-procuring reactions of caudatectomized cats in contrast to the intact or lobectomized ones. The conclusion is made that acetylcholinergic structures of the caudate nucleus play an important role in the central inhibitory mechanisms responsible for the extinction of nonreinforced reactions.     

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.     

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.     

Conditioned reflex analysis of functional connections between the hippocampus and limbic system structures

Instrumental defensive conditioned reflex elaborated in dogs to stimulation of the dorsal and ventral hippocampus, also appeared, due to generalization, in response to stimulation of a number of limbic structures. Two types of changes in the generalization effects (estimated by parameters of motor conditioned reaction) were observed in the course of conditioned reflex stabilization: enhancement (in response to stimulation of the lateral hypothalamus, lateral nucleus of septum, limbic cortex) and weakening toward complete disappearance (in response to stimulation of the medial nucleus of amygdala and medial hypothalamus). Manifestation of the generalization phenomenon from the brain structures, which are not involved initially into conditioned activity, suggests the existence of close functional connections between these structures and the hippocampus.     

Formation of temporary connections in dogs following destruction of the amygdaloid complex, head of the caudate nucleus and orbital cortex]

Ablation of the orbital cortical zones in dogs after ablation of the basolateral part of the amygdala and the caudate nucleus head considerably impeded the elaboration of secretory conditioned alimentary reflexes, without affecting the rate of elaboration of simple instrumental food-procuring reaction. The dogs lost however the capacity to differentiate non-reinforced stimuli from reinforced ones, which was revealed in both secretory and instrumental reactions.     

Dynamics of caudate nucleus involvement in the process of internal inhibition of the food-getting reflex]

Changes of slow spindle electrical activity (12 to 14 cps) and evoked potentials in the cat caudate nuclei and the motor cortex were studied at different stages of elaboration of differentiation inhibition of a conditioned food-procuring reflex to acoustic stimuli. It has been shown that participation of the caudate nuclei in the inhibitory process begins at the stage of enhancement of food-procuring activity (second stage) and is apparently due to the animal's strong alimentary motivational excitation. At the third stage the inhibitory influence of caudate nuclei on the animal's motor activity in general, and the activity of the motor cortex in particular, develops to the full.     

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.     

Effect of stimulation of GABA-ergic structures of the substantia nigra and caudate nucleus on food-getting behavior in the cat

A study was made of the functional significance of GABA-ergic structures of the substantia nigra (SN) and the caudate nucleus (CN) and their role in food-procuring behaviour of cats. Analysis was made of behavioral and EEG-effects of local GABA and the GABA antagonist, picrotoxin, microinjections into the studied brain structures. Stimulation of the GABA-ergic structures of the SN produced a sedative effect and depression of the cat food-procuring behaviour. Effects of stimulation of the CN GABA-ergic structures were to a great degree reverse. The conclusion has been made that GABA-ergic structures of the SN and the CN play different roles in controlling the CN inhibitory influence upon food-procuring behaviour.     

The organization of instrumental food-procuring movements in rats]

The roles of the lateral hypothalamus, basolateral nucleus of the amygdalar complex, the second field of the frontal cortex, and ventromedial thalamic nucleus in organization of the fast ballistic food-procuring movements were studied in albino rats. Sequences of uni- and bilateral destruction of the brain structures were assessed by photorecording. Movement-related neuronal activity in these structures was recorded in freely moving animals. A specific involvement of each of the above listed structures in organization of food-procuring movements was shown. The lateral hypothalamus seems to participate in initiation of the motor program and its efficient realization, the basolateral amygdala appears to produce activatory, training, and stabilizing effects. The second field of the motor cortex leads in movement acquisition (i.e., in memorizing) and decision making about triggering the program. The idea about the relay role of the thalamic motor nucleus is supplemented by understanding of its more complex integrative function.     

Neurochemical mechanisms of the septum in food getting conditioned responses in rats]

The influence of microinjections of monoamines and of glutamic acid into the lateral zone of the septum on a food-procuring conditioned reaction was studied in experiments on rats. Dopamine does not change, while noradrenaline, serotonin and glutamic acid increase the magnitude and number of conditioned food-procuring movements and substantially lengthen the reflex latency. The effects of serotonin are achieved through D-serotonin-, and of noradrenaline, through L-adrenoreactive structures of the neuronal systems of the septum. The influence of glutamic acid on the rat food-procuring conditioned reactions is not linked with the action on the serotonin- or adrenoreactive structures of the septum neuronal systems.     

The effect of phenamine and caffeine on caudate inhibition of conditioned reflex avoidance reactions in cats]

In cats with a preliminarily learned conditioned avoidance reaction, stimulation of the caudate nucleus inhibited behavioral response by lengthening its latency and reducing the number of conditioned reactions. Intensity of the inhibitory effect did not substantially depend on the localization of electrodes in the head or body of the nucleus and weakened within a few experimental days. D,1-amphetamine (0.5 to 4 mg/kg) and caffeine (10 to 10 mg/kg) suppressed the caudate inhibition, but the action of the drugs was manifested in different ways. The influence of large doses of d,1-amphetamine was characterized by a serious disturbance of behaviour and caudate inhibition of conditioned responses.     

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.     

Role of the lateral hypothalamus and prefrontal cortex in organization of voluntary movements

Roles of the lateral hypothalamus and prefrontal cortex in organization and control of automatized food-procuring movements were studied in rats under conditions of unrestrained behavior with the use of video- and photorecording techniques, destruction of the brain structures, and recording of single neuron impulse responses. The lateral hypothalamus is considered a link in the control system for food-procuring movements, which provides formation of the motor program. The role of the prefrontal cortex is regarded as related to programing and initiation of food-procuring movements and current control of efficiency of their performance. Positions of the lateral hypothalamus and prefrontal cortex within an ensemble of the motor centers, which organizes voluntary movements, are discussed.     

Differences in hypothalamic monoaminergic mechanisms in heterogeneous conditioned reflexes in rats

Monoamines and aminoacids were microinjected in the middle medial hypothalamus of rats following the elaboration of conditioned food-procuring or avoidance reflexes. The glutamine acid had no effect on the avoidance reflex (AR), but stimulated the motor activity and the food-procuring reflex (FR), shortening its latencies, increasing the number of the conditioned food-procuring movements and the reflex size. Dopamine decreased the motor activity, but did not influence the AR latencies, whereas norepinephrine prolonged the AR latencies without changing the motor activity. Both catecholamines, while having no effect on the muscle tone, suppressed FR, prolonging the latencies and decreasing the reflex and the number of conditioned food-procuring movements. Local administration into the hypothalamus of GABA prolonged the latencies of heteromodal conditioned reflexes, whereas the serotonin had no effect on the recorded FR parameters, but facilitated AR significantly reducing its latencies.     

Response properties of diencephalic neurons to visual, acoustic and hydrodynamic stimulation in the goldfish, Carassius auratus

We studied the responses to sensory stimulation of three diencephalic areas, the central posterior nucleus of the dorsal thalamus, the anterior tuberal nucleus of the hypothalamus, and the preglomerular complex. Units sensitive to acoustic (500 Hz tone burst), hydrodynamic (25 Hz dipole stimulus) and visual (640 nm light flash) stimuli were found in both the central posterior and anterior tuberal nucleus. In contrast, unit responses or large robust evoked potentials confined to the preglomerular complex were not found. In the central posterior nucleus, most units were unimodal. Many units responded exclusively to visual stimulation and exhibited a variety of temporal response patterns to light stimuli. In the anterior tuberal nucleus of the hypothalamus, most units responded to more than one modality and showed a stronger response decrement to stimulus repetitions than units in the central posterior nucleus. Our data suggest that units in the central posterior nucleus are primarily involved in the unimodal processing of sensory information whereas units in the anterior tuberal nucleus of the hypothalamus may be involved in multisensory integration.     

Effect of electric stimulation of the somatosensory cortex and caudate nucleus on extinctive inhibition of a conditioned alimentary reflex to sound]

In experiments performed on 9 dogs with alimentary method, extinctive inhibition was deepened and its elaboration was aceelerated by electrical stimulation of somatosensory and motor cortical areas and ventral segment of the caudate nucleus head. The extinction of the conditioned reflex was slowed down by stimulation of the anterolateral gyrus and the central segment of the caudate nucleus head. General motor excitation of animals during stimulation of the dorsal zone of caudate nucleus head impaired the elaboration of extinctive inhibition.     

Feeding behavior of the cat in response to stimulation of the caudate nucleus

In chronic free-moving cats unilateral, low frequency, long duration stimulation of the caudate nucleus causes a significant reduction of food intake. The effects are greatest at the beginning of the stimulation. On cessation of stimulation the animals take enough food to compensate for that lost during the time of stimulation. Results are discussed either considering interrelationships between striatum and lateral hypothalamus, either regarding recent viewpoints distinguishing two striatal compartments: dorsal or "non limbic" striatal region and ventral or "limbic" striatal region.