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.     

Functional organization of myogenic pacemaker of the stomach in conditions of hunger and satiation

In chronic experiments, we have studied electrical activity of muscles of the gastro-esophageal sphincter, small curvature, corpus and antrum of the stomach in conditions of hunger, food intake behaviour and satiation of the rabbits. The aim of this study involved particularities of the electrical activity of myogenic pacemaker zone of the stomach. It has been shown that function of myogenic pacemaker of the rabbit stomach is performed by smooth muscles of the small curvature of the stomach. Pacemaker properties of muscles of the small curvature of the stomach are performed in conditions of food intake behaviour and satiation.     

Features of differential inhibition in choice between alimentary and defensive response

Instrumental defensive (avoidance/escape) and alimentary responses (reinforced with palatable food) in dogs were conditioned by the same stimulus (6-Hz light flashes). Differential inhibition for these responses (0.6-Hz flashes) was formed in unalterable series. Later on, alternative experiments with choice between reinforcements were carried out. In both of experimental series, the degree of alimentary excitability (hunger, satiation) was changed. Numbers of responses to differential and positive conditioned stimuli and their latencies were calculated. Under condition of choice (electrodes on a leg and a pedal in front of a dog) the response depended on a dominant motivation. The dogs differed in the degree of motivation dominance. Differential inhibition was less perfect in unalterable experimental series with dominant motivation. Under conditions of choice between alimentary and defensive reinforcements, the response to the differential stimuli depended on the balance between these motivations: two days of hunger increased the number of alimentary responses, defensive responses prevailed after satiation.     

Acid-Base Balance Modulates Respiratory and Alimentary Behavior of the Mollusc Lymnaea stagnalis

An active reaction (change of pH) in hemolymph of the freshwater pulmonate mollusc Lymnaea stagnalis is studied in various physiological states: hunger, satiety, and alimentary excitation. In satiated animals the hemolymph pH is shifted to the acid area (7.6 ± 0.003) as compared with hungry animals (7.9 ± 0.05). The satiated individuals are characterized by an increased respiratory activity and decreased food consumption as compared with hungry animals. Acidification of the medium leads to an increase of excitability of the respiratory network interneurons (RPeD1, VD4, VD1/RPD2) and to inhibition of activity of the alimentary network interneurons (R/L CGC), whereas alkalization, to opposite effects. It is suggested that pH is one of factors coordinating activity of functional systems of Lymnaea stagnalis due to effect on neuronal correlates of the respiratory and alimentary behavior.     

Effects of food motivation on spike activity of cat somatic cortex neurons

Spike response to unconditioned electrocutaneous stimulation was investigated in cortical neurons of areas 3 and 4 in untrained hungry cats during heightened excitation motivated by food presentation and when at rest. This reinforcement led to changed background activity level, reduced intensity of the initial stages of spike response, and disappearance of late neuronal response. Neuronal response of the same cortical area to a conditioned stimulus (a clicking sound) during reduced food motivation (the animals being sated during the course of the experiment) was also studied under the effects of instrumental feeding reflex. Coordination between the timing of neuronal response and their corresponding movements was discovered from comparing response pattern accompanying the execution of paw-placing (conditioned reflex and intersignal) movements and those recorded at different levels of food-induced excitation, as well as a similarity between these reactions. It was found that the initial stages of neuronal response to a conditioned signal only occurred during contraction of the brachial biceps muscle, while coordination between their timing and that of EMG changes was dependent on the animal's degree of satiation. Findings indicate the possibility of food-induced excitation substantially influencing spike response pattern in somatic cortex neurons.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 6, pp. 725–735, November–December, 1987.     

The role of biological needs in the genesis of self stimulation]

It has been found in fifteen rats with monopolar electrodes implanted in the lateral hypothalamus that after stimulation of the brain with bursts of electrical pulses of fixed duration, with definite combinations of stimulation parameters, the histograms of the duration of pedal pressing have a polymodal appearance. As the combinations of stimulation parameters change, the number, position and magnitude of the modes undergo a corresponding change. With unchanged parameters of stimulation the form of pressing duration histogram does not change significantly. A conclusion has been drawn that the modal duration of pressing in the course of self-stimulation is apparently an effector manifestation of central integration of reinforcing excitation. In a state of hunger and thirst as well as under weak nembutal anaesthesia, the previously monomodal histograms of the pressing durations produce additional modes which diminish and disappear after satiation and discontinuation of the nembutal effect. It is assumed that at least some modes of the histograms of the pressing duration of self-stimulation may reflect an activation of the systems of biological needs.     

Changes in serotonin metabolism during food satiation in the mink and its effect on predatory aggression

Effect of single and protracted alimentary satiation on predatory aggression and content of serotonin and its metabolite 5-hydroxyindoleacetic acid in the amygdalar complex and hypothalamus was studied in mink--a representative of predators. A single alimentary satiation was not accompanied by any marked changes in serotonin metabolism and predatory behaviour. A long-term alimentary satiation significantly heightened the content of the 5-hydroxyindoleacetic acid in the lateral hypothalamus and amygdala without any changes in serotonin level, testifying to a high synthesis of serotonin with its simultaneous intensive destruction. Long-term satiation also greatly increased the latencies of aggression and killing the victim. It is suggested that serotonin is one of endogenous factors controlling predatory behaviour in predators, and this control is realized in interrelation with feeding behaviour.     

Hippocampal neurons of the CA3 field in animals of different typological groups exposed to emotional stimuli

Hippocampal unit activity in of the right and left CA3 fields was studied in rats which were divided in two groups by the method of "emotional resonance": the animals that did ("A") and did not stop ("E") crying of rat-partner. The rate of neuron firing was studied in the state of hunger, satiation, and under exposure to intracranial electrical stimulation of the emotional positive and negative structures of the brain. It was shown that the intracranial stimulation, especially positive, increased the rate of firing. Under exposure to emotional stimuli, the neural activity was asymmetric only in E rats. The activity at the left was more intensive then the right-side activity and did not depend on the sigh of emotion.     

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.     

Impulse activity in the CA1 field in animals of various typological groups exposed to emotional stimuli

Hippocampal unit activity in the right and left CA1 fields was studied in rats divided in two groups by the method of "emotional resonance": the animals that did (A) and did not stop (E) crying of rat-partner. The rate of neuron firing was studied in the state of hunger, satiation, and under exposure to intracranial electrical stimulation of the emotional positive and negative structures of the brain. It was shown that the intracranial stimulation, especially positive, increased the rate of firing. Under exposure to emotional stimuli, the neural activity was asymmetric only in the A rats. The activity at the left was more intensive than the right-sided activity and did not depend on the sigh of emotion.     

Comparative analysis of neuronal impulse activity in the CA1 and CA3 hippocampal fields in various typological groups of rats under exposure to emotional stimuli

Hippocampal unit activity in the right and left CA1 and CA3 fields was studied in rats divided in two groups by the method of "emotional resonance": the animals which did ("A") and did not stop ("E") crying of a partner rat. The rate of neuronal firing was studied in the state of hunger, satiation, and under exposure to intracranial electrical stimulation of the emotional positive and negative structures of the brain. It was shown that units increasing their activity after satiation prevailed in the CA1 field, whereas, in the CA3 field, the majority of neurons decreased the firing rate under these conditions. Intracranial stimulation, especially positive, increased the rate of firing in both hippocampal fields. Under exposure to emotional stimuli, "A" rats displayed asymmetric unit activity only in the CA1 field, whereas in "E" rats, activity was asymmetric only in the CA3 field. Under these conditions in both groups of animals, the left-side activity was more intense than the right-side activity independently of the emotion sign.     

Neural ensemble coding of satiety states

The motivation to start or terminate a meal involves the continual updating of information on current body status by central gustatory and reward systems. Previous electrophysiological and neuroimaging investigations revealed region-specific decreases in activity as the subject's state transitions from hunger to satiety. By implanting bundles of microelectrodes in the lateral hypothalamus, orbitofrontal cortex, insular cortex, and amygdala of hungry rats that voluntarily eat to satiety, we have measured the behavior of neuronal populations through the different phases of a complete feeding cycle (hunger-satiety-hunger). Our data show that while most satiety-sensitive units preferentially responded to a unique hunger phase within a cycle, neuronal populations integrated single-unit information in order to reflect the animal's motivational state across the entire cycle, with higher activity levels during the hunger phases. This distributed population code might constitute a neural mechanism underlying meal initiation under different metabolic states.     

Impulsation of hypothalamic and amygdalar neurons in bilateral derivations in the state of food motivation

The character of impulsation of single neurons in the lateral hypothalamic and amygdalar central nucleus of rabbits recorded in bilateral derivations during quiet wakefulness, after 24-h food deprivation, and after satiation was studied by plotting autocorrelation histograms and by counting the mean frequency of discharges. During the transition from hunger to satiation, the character of impulsation of neurons in hypothalamus and amygdala changed in different ways: (1) a greater number of hypothalamic than amygdalar neurons changed their mean discharge frequency (85 versus 56%, respectively); (2) in hunger, the number of hypothalamic neurons with delta-frequency oscillations decreased as compared to quiet wakefulness and satiation, and in the amyglala the number of neurons with beta2-frequency oscillations increased; (3) in hunger, the number of hypothalamic neurons with bursting and periodic discharges decreased and the number of amygdalar neurons with equiprobabilistic discharges increased. During state alternation (according to the autocorrelation histograms) the strongest changes in the character of neuronal discharges took place in the left hypothalamus and left amygdala. The maximum differences in neuronal impulsation between the left and right hypothalamus were observed in the state of hunger and between the left and right amygdala, after satiation.     

The integrating role of biological motivation in the realization of feeding and drinking behaviors]

In chronic experiments on rabbits with preliminary alimentary or water deprivation electrical and mechanic activity was studied of the chewer muscle proper and of the esophagus in the process of animals food or water taking. It has been established that in patterns of electrical and mechanic activity of the chewer muscle proper and esophagus specific differences of alimentary and drinking behaviour of animals are reflected. Dominating motivation of different biological properties determines the specific integration of motoneurones of chewing and swallowing centers and peripheral contraction elements of digestive tract in the functional systems of alimentary and drinking behaviour.     

The spectral characteristics of the electrical activity in the rabbit brain during the hunger dominant]

By means of daily alimentary deprivation the dominant of hunger was created in rabbits. In response to acoustic stimuli summational swallowing and chewing movements appeared. Spectral analysis of the electrical brain activity showed the presence of primary dominant focus zone (lateral and ventromedial hypothalamus), characterized by an increase of spectrum power in delta-range while in the orbito-frontal, sensorimotor, parietal cerebral cortex, in the medial and lateral preoptic hypothalamic zones the power of biopotentials spectrum decreased within the whole analyzed frequency range.     

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.     

Conditioned food reflexes acquired on the basis of a dominant

By means of daily alimentary deprivation and presentation of acoustic stimuli, a hunger dominant was created in rabbits. After dominant testing by eye stimulation with air puff, when not only winking of one eye but also swallowing or chewing appeared,--the dominant was disrupted by giving food to the animal. Disruption of motivational hunger dominant led to rapid formation of stable temporary connection. At subsequent creation of hunger dominant the animal itself disrupted it by winking reaction with the significant eye. The basis of goal-directed reaction is the activation of feedback temporary connection, established at the dominant summation stage. The conditioned alimentary reflex, elaborated on the basis of dominant disruption is designated as endogenous alimentary conditioned reflex.     

Relation between the process of information processing during learning and the level of motivation

Adaptive behaviour of 58 male mice of BALB/c line was studied (10 experimental sessions) in a multialternative maze (180 positive decisions) at various levels of alimentary excitation, after 0--12--24--36 hours of starvation. It has been found that such characteristics of the brain integrative activity as power, speed and rate of the development of motor information processing (estimated by dynamics of formation of correct decisions) are in direct dependency on the level of alimentary excitation. The suggestion is discussed that the level of concrete physiological neens represents both an "energiator" of the brain activity and its directing and organizing determinant.     

Interaction between two excitation foci in the central nervous system capable for summation

The interaction between two dominant foci was carried out on different models of dominant. It was shown that the following pairs: latent motor and blinking excitation foci; hunger and hypnotic dominants, decaying polarization dominant (related with functioning of the left-hemisphere) and hypnotic dominant can function simultaneously. After repeated formation of a new dominant focus against the background of the existing stable dominant created earlier, a replacement of dominants takes place. This process passes through the stage of formation of the latent dominant not yet apparent at the behavioral level but with the electrical activity typical for the dominant focus. Actually, two dominants exist at this stage: the previous active and latent foci. The latter determines further behavior of the animal.     

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).