Characteristics of the systemic organization of the cortical neurons in various forms of the manifestation of the conditioned reflex to time

Conditioned food-procuring reflex to time (2 minutes interval) was elaborated in cats. By the method of cross-correlative analysis the combined neurones activity in microareas and between microareas of the motor cortex was compared at various forms of conditioned reflex manifestation. Three types of reactions were considered: A--decrease of respiratory movements amplitude towards the end of the studied interval between reinforcement; B--increase of the amplitude; C--food-procuring paw movement a few seconds before the reinforcement. All three forms of the conditioned reflex to time differed from each other by the level of increase of functional connections number by the moment of the reinforcing stimulus action, and also to a greater extent by the frequency of occurrence of intervals in which the sum of neuronal connections in all simultaneously recorded microareas was greater in the "active" phase than in the "inactive" one. These parameters did not always correlate with the change of impulses frequency of separate neurones which occurred considerably more seldom. All the observed changes were manifest significantly more often when the animals performed the instrumental food-procuring movement than during changes of only the respiratory movements amplitude.     

Effect of disulfiram on the interconnected activity of cortical neurons in trained cats

The action of disulfiram on interconnected activity of neurones in the visual and motor cortical areas was studied in cats with food-procuring conditioned responses to light. Multiunit activity was recorded from the areas and, by means of amplitude discrimination, separated into impulse flows. Crosscorrelation analysis of the impulse series was used to reveal the character and temporal parameters of interconnected activities of neurones firing in correlation within the limits both of the same cortical area and of the two different ones. A depressing action was shown of the disulfiram on the food-procuring reaction, accompanied by a decrease of the number of pairs of neurones from the visual and motor cortical areas mostly acting in interconnection, interactions with long time delays being mostly affected. The character of action of neighbouring neurones in the visual and motor cortical areas changed in the same direction, expressed in their firing by a "common source" type. The question is discussed of disulfiram influence on interneuronal connections of both types suggesting a decrease of alimentary motivation as well as disturbance of food-procuring conditioned motor coordination.     

The effect of vasopressin on memory processes in Macaca fascicularis]

The role of vasopressin (arginin-vasopressin) in the regulation of conditioned instrumental food-procuring reactions and different kinds of memory such as delayed reflexes, image, short-, and long-time memory was studied in monkeys. Motor and autonomic effects of vasopressin were assessed. It was found that in monkeys, vasopressin administration differently affected the simple conditioned food-procuring reactions and memory. During functional disorders of the higher nervous activity, vasopressin was more efficient in its action on memory and its restoration. Formation of two types of vasopressin effects on the higher nervous activity in evolution of mammals is discussed.     

Neuronal reactions in field 2 of the frontal cortex, related to organization and performance of food-procuring movements in rats

Movement-related electrical reactions of neuronal units localized in field 2 of the frontal cortex were studied in albino rats performing fast food-procuring movements under conditions of unrestrained behavior. According to the temporal characteristics of the changes in the neuronal spike activity, three types of reactions were classified: (i) activation that forestalled the movement initiation for 1.0–1.5 sec; (ii) activation or inhibition forestalling this beginning for 0.20–0.26 sec; and (iii) activation in the course of a performed movement. Considerations about the involvement of the neurons of various cortical layers in the mechanisms of programing, switching on, and current control of the efficiency of performance of food-procuring movements are proposed, and the role of the frontal cortex in these processes is discussed.     

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.     

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.     

Spectral-correlative characteristics of the EEG reactions preceding conditioned reflex motor reactions in dogs

The work is a logical continuation of previous studies (analysis of the background electrical activity in the band 1-100 Hz in interstimulus intervals in the process of lever pressing alimentary conditioning in dogs) and it is dedicated to correlation-spectral analysis of prestimulus periods and EEG-reactions to conditioned stimuli, previous to conditioned lever pressing. Visually the EEG reactions present discharges of high-frequency (40-100 Hz) synchronized activity preceding for 40-300 ms the beginning of the changes in EMG of the "working" limb. It is shown that EEG reactions are characterized (in comparison with the background activity) by a higher energetic level and a greater expression of the high coherence (I greater than 0.75) and also by greater phase shifts, in counterbalance to the domination of little phase shifts in the background activity. It is assumed that the patterns of EEG reactions may participate in trigger mechanisms either eliciting conditioned motor reactions (to positive conditioned stimuli) or preventing them (to inhibitory conditioned stimuli).     

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.     

Neuronal reactions in the reticular nucleus of the thalamus upon realization of conditioned placing and its differential inhibition

Cats were trained to perform conditioned forepaw placing (CFP) using food reinforcement. Reactions of 33 neurons were recorded extracellularly in the reticular nucleus (RN) of the thalamus; among these neurons, 24 units were localized in the sensorimotor part of the nucleus. We used short acoustic signals as conditioning positive and differential (negative) stimuli (PS and DS, respectively). When CFP was realized, 21 neurons of the RN sensorimotor part generated late long-lasting activating or inhibitory spike reactions (durations up to 6 sec and 2 sec, respectively); in 3 neurons there were no reactions. Under conditions of differential inhibition, such reactions were not observed, while the background impulse activity became clearly suppressed. In two-thirds of the neurons under study, alternating PS and DS presentations led to suppression of the reactions to PS presentation. We suppose that differential inhibition-related suppression of the background activity and of the spike reactions related to CFP realization result from restriction of the input synaptic volleys to the RN neurons.     

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.     

Monoaminergic mechanisms of the amygdaloid complex actualizing conditioned reflexes of different biological modality]

Microinjection of dopamine and serotonin into the dorso-medial portions of the amygdalic complex of rats increased the latent period of conditioned defense and motor food reactions, spontaneous motor activity, the number of jerks and the value of the conditioned food reflex. Noradrenaline failed to influence the recorded indices of the conditioned food-procuring reflex, but facilitated the conditioned reaction of avoidance, significantly shortening its latent time. The results obtained pointed to the specificity of the neurochemical mechanisms realizing at the level of the amygdalic complex conditioned reflexes of various biological modality in rats.     

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 neurotensin on the behavior of rats with damaged serotoninergic neurons under immobilization stress

It was shown that the immobilization of animals has led to reducing of vertical and horizontal locomotor activity in the "open field" and decreasing of number of conditioned food-procuring reactions into T-maze. The damages of serotoninergic neurons produced via local injections of selective neurotoxin 5, 7-dihydroxytriptamine into dorsal raphe nucleus intensified behavior alterations. Neurotensin administrations reduced effects of neurotoxin: the rats locomotor activity and quantity of conditioned reactions into T-maze were kept at the phone level just after immobilization as well as next two days. The results indicate the important protective significance of neurotensinergic brain structures for ensuring of adaptive behavior of animals with damaged serotoninergic neurons under emotional stress conditions. It is supposed that neurotensin normalizing influences on behavior is connected to a restoration of balance of dopamine-and serotoninergic brain structures interaction.     

Automated Food-Procuring Movement-Related Neuronal Activity in the Basolateral Amygdala of the Rat

We studied the impulse activity of neurons of the basal and lateral amygdalar nuclei generated when experimental animals (rats) performed fast stereotyped food-procuring movements by the forelimb. Within the basolateral amygdala, there are neurons whose activity is related to different stages of getting off the food, and according to the characteristics of their spiking these neurons should be divided into a number of subpopulations. Activation forestalling the movement initiation by 0.5-1.0 sec was observed in most neurons of the basolateral amygdala; this is considered a manifestation of excitation related to a motivation component of the food-procuring behavior. Activation of amygdalar neurons following movement initiation can result from generation in this structure of additional excitation necessary for successful performance of a complete food-procuring motor cycle.     

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.     

Correlation of evoked potentials in the frontal cortex and hippocampus of cats in emotional stress

Averaged auditory evoked potentials (AEPs) were recorded in symmetric points of the frontal cortex and dorsal hippocampus of cats performing acquired conditioned food-procuring reaction reinforced in 100% cases, urgent transition to 30%-reinforcement, and return to 100%-reinforcement. Emotional stress estimated by a heart rate rise developed during increased food motivation of a cat as well as during change in ordinary food-procuring stereotype. The emotional stress was accompanied by a high positive correlation of cortical and hippocampal AEPs. Decrease in the stress level led to a drop between AEP correlations and appearance of their negative values. In emotional stress, the interactions between the frontal cortex and dorsal hippocampus were asymmetric: right-side correlations were higher.     

Impulse activity of neurons of the visual and somatosensory regions of the cerebral cortex at different stages of goal-directed behavior

Impulse activity of neurones of the visual and somatosensory cortical areas was studied in free moving cats during performance of conditioned instrumental food-procuring reactions to the presentation of light or sound. It was established that the units of these cortical areas may participate in both all or individual stages of complex instrumental behaviour. The visual cortex neurones are more extensively involved in the formation of successive stages of the goal-directed behavioral act. Significant differences were revealed in the unit responses of the visual and somatosensory cortical areas at the moment of the switching on of the conditioned signal, at the period of "reinforcement anticipation", at the moment of appearance of milk, the reinforcing agent, and during reinforcement, when the milk was lapped by the animal.     

Characteristics of cortical responses to electrostimulation of the internal geniculate body during formation of a defensive conditioned reflex]

During elaboration of a classical defensive conditioned reflex the dogs exhibited a dependence of the changes in amplitude and configuration of evoked potentials (EP) to electrical stimulation of the medial geniculate body (MGB), a conditioned stimulus, on the nature of effector manifestation of the conditioned reflex: the late components were the most depressed at multiple phasic reactions and not infrequently increased and became complicated at single and short motor reactions as well as at their incidental absence. The primary oscillations, while mostly remaining unchanged, were depressed in the case of conditioned reactions attended with a general motor restlessness. A difference has been revealed during conditioning in the EP changes to electrical stimulation of MGB and to an adequate peripheral stimulation. It has been assumed that EP changes during conditioned activity are determined by the relationship between the levels of tonic and phasic cortical activation.     

The dynamics of the interimpulse intervals in the activity of sensorimotor cortex neurons during the acquisition of the food-procuring reflex in the rabbit]

State of hunger is characterized by the presence of definite distribution of interimpulse intervals in the activity of sensorimotor cortical neurones (SMC) of rabbit. Mostly bi- and three-modal distribution of interimpulse intervals in the background activity in hungry animals changes in the process of elaboration of food-procuring habit. As the habit consolidates, the SMC neurones acquire the ability to forestalling actions. Peculiarities are revealed of organization of the SMC neurones impulse stream in response to the action of conditioned signal in the case of abolition or substitution of the reinforcement. Repeated substitutions of reinforcement cause the formation of activity of concordance in the moment of substitute "recognition" despite the absence of alimentary reinforcement.     

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.