Interrelations between neurons of the frontal cortex and hippocampus under cholinergic deficit in choice behavior of cats

Appetitive instrumental conditioned reflexes on light (CS+) were formed in six cats by the method of "active choice" of quality of reinforcement; bread-meat mixture was given after short-delay conditioned bar-press responses, and the delayed responses were rewarded by meat. The animals differed in choice behavior strategy: "self-control", "ambivalent", "impulsive". The multiunit activity in the frontal cortex and hippocampus (CA3) was recorded. Cross-correlation analysis was used for estimation of correlation of activities in neuronal pairs in the frontal cortex and hippocampus (distributed frontal-hippocampal networks) and pairs within the same structure (frontal and hippocampal local neuronal networks). It was shown that the number of cross-correlations between the discharges of neurons both in the local and distributed networks was significantly higher in "self-control" cats. Under conditions of systemic administration of antagonists of muscarinic central cholinoreceptors (trihexyphenidyl and scopolamine), the bar-press conditioning impaired, the number of direct interneuronal connections decreased, and the number of externally synchronized correlations ("common input") significantly increased. The results suggest that the local and distributed neural networks of the frontal cortex and hippocampus are involved in the system of brain structures that determine the behavioral strategy of "self control".     

Ensemble activity of visual and frontal cortex in the conditions of choice of different value food reinforcement in cats

The method of "low choice" of food value reinforcement depending on delayed response to its reception demonstrated various strategy of behaviour, showing short or delayed responses of pressing pedal for reception of low or high value of food reinforcement. In trained cats, multiunit activity was recorded in investigated brain areas and functional interneuron interactions were subsequently analysed. Significant prevalence of interneuron interactions was revealed in "impulsive" animals in both cortical zones as well as intergroup differences during the pre-signal and signal periods in visual and frontal cortex.     

The interrelations between neurons of the amygdala and hypothalamus during conditioning with selection of food reinforcement quality in cats

Three cats were subjected to appetitive instrumental conditioning to light by the method of the "active choice" of the reinforcement quality. The short-delayed conditioned bar-pressings were reinforced by bread-meat mixture and the delayed response by meat. The animals differed in behavior strategy: two animals preferred bar-pressing with long delay (the so-called "self-control" group) and one animal preferred bar-pressing with short delay (the so-called "impulsive" group). The multiunit activity of the basolateral amygdala and nucleus lateralis of the hypothalamus was recorded through chronically implanted nichrome wire semimicroelecrodes. The interactions between the neighboring neurons in the lateral hypothalamus and basolateral amygdala (within the local neuronal network) and between the neurons of the basolateral amygdala and lateral hypothalamus (distributed neuronal networks in the direction amygdala--hypothalamus and vice versa) were evaluated by means of statistical crosscorrelation analysis of spike trains. The crosscorrelational interneuronal connections in the delay range of 0-100 ms were examined. It was shown that the number of crosscorrelations between the discharges on neurons both in the local networks of basolateral amygdala and distributed networks was significantly higher in "impulsive" cats. In both groups of animals, the percentage of crosscorrelations between neighbouring neurons in the local networks of the lateral hypothalamus was similar. We suggest that the local networks of the basolateral amygdala and amygdalar-hypothalamic distributed neuronal networks are involved in the system of brain structures which determine the individual features of animal behavior.     

Functional asymmetry of the frontal cortex and lateral hypothalamus of cats during food instrumental conditioning

The synchronism and latency of auditory evoked potentials (EP) recorded in symmetric points of the frontal cortex and lateral hypothalamus of cats were measured at different stages of instrumental food conditioning and after the urgent transition to 30% reinforcement. Correlation coefficients between EPs in the cortex and hypothalamus were high (with left-side dominance) at the beginning of the experiments, when food motivation was high, and during the whole experiments in cases of high-probability of conditioned performance. Analysis of early positive P55-80 EP component showed that at all conditioning stages the peak latency of this component was shorter in the left cortical areas than in symmetrical points, whereas in the hypothalamus the shorter latency at the left side was observed at the stage of unstable conditioned reflex, and at the stage of stable reflex the latency of the studied component was shorter at the right side. During transition to 30% reinforcement, the latency was also shorter in the right hypothalamus. It is suggested that the high left-side correlation between the hypothalamus and cortex was associated with motivational and motor component of behavior rather than reflected the emotional stress induced by transition to another stereotype of food reinforcement (30%).     

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.     

Cooperative activity of motor and frontal cortex neurons in trained cats systemically administered M-cholinoreceptor blockers]

It was shown previously that peripherally administered antagonists of the central 1 M-cholinoreceptors led to a selective impairment of bar-pressing response in a food-reinforced operant conditioned task but did not alter contextual behavior and functions such as motivation, perception, and locomotion. To obtain information about the central mechanisms of the conditioning impairment, we recorded simultaneously the extracellular multiunit activity from the frontal and motor neocortical areas of five cats trained to acquisition criteria in a food-reinforced operant conditioning task. Multiunit recordings were performed drur 1) normal conditioning; 2) conditioning during subcutaneous administration of muscarinic antagonists scopolamine (0.03 mg/kg), trihexyphenidyl (1 mg/kg), and methylscopolamine (0.03 mg/kg). Autocorrelation analysis showed that scopolamine and trihexyphenidyl but not methylscopolamine led to a significant increase in the tendency of cortical cells to fire in a cyclic way (i.e., the shift of the firing pattern from a single-spike discharge to burst, rhythmic, or rhythmic-burst discharge) both in the motor and frontal areas. Cross-correlation analysis showed that the bursting and rhythmic-bursting cells synchronized their activity within and (in a number of cases) between the cortical areas. These changes in the neuronal activity within the motor cortex and frontal cortex were accompanied by a significant decrease in the functional connectivity both inside and between the cortical areas in parallel with selective impairment of the conditioned response.     

The choice of reinforcement quality depending on the delay time of the instrumental reaction in cats]

In experiments on seven cats instrumental delayed reflexes with different quality reinforcement were elaborated by method of "active choice", where the time of delay of the motor reaction served as a signal of quality of the reinforcement. Five cats used a strategy with long delay high-quality reinforcement (meat), and two cats preferred short delay and low-quality reinforcement (bread-meat mixture). In special experiments with the change of alimentary motivation (24-hour alimentary deprivation and saturation of animals) it was established that the level of alimentary motivation within the studied limits did not change the strategy of behaviour preferred by the given animal. Individually varying ability to choice of reaction determining more valuable reinforcement it is possible to consider as an experimental analogue of the mechanisms of will. The question is discussed about the role of typological properties of cats in choice of behaviour strategy.     

Distribution of neuronal nitric oxide synthase-immunoreactive neurons in the cerebral cortex and hippocampus during postnatal development

Although many reports have argued a role for nitric oxide (NO) during postnatal development, there has been no combined demonstration in the cerebral cortex and hippocampus. We have investigated the distribution and morphology of neurons and fibers expressing neuronal NO synthase (nNOS) in the cerebral cortex and hippocampal formation of rats during the postnatal development, and correlated these findings with developmental events taking place in these regions. In the cerebral cortex, the nNOS-immunoreactive cells could be divided into two classes : heavily stained neurons and lightly stained neurons. For the lightly stained nNOS-positive neurons, only the cell bodies were observed, whereas for the heavily stained neurons, the cell bodies and their dendrites were visible. During the postnatal days, heavily stained neurons reached their typical morphology in the second week and appeared in all layers except for layer I. In the hippocampus, there was a transient expression of nNOS in the pyramidal cell layer at P3â€P7, and this expression disappeared during following days. The adult pattern of staining developed gradually during the postnatal period. This study suggested that these alterations might reflect a region-specific role of NO and a potential developmental role in the postnatal cerebral cortex and hippocampus     

Interaction between influences of functionally different cortical areas on caudate neurons in cats

Unit activity in the caudate nucleus evoked by paired stimulation of the anterior sigmoid and middle suprasylvian gyri was studied in acute experiments on cats. Responses in most neurons to testing stimulation of the anterior sigmoid gyrus during the period of inhibition of spontaneous activity evoked by conditioning stimulation of the suprasylvian gyrus were preserved, but in isolated cases they were actually facilitated. Meanwhile conditioning stimulation of the anterior sigmoid gyrus in the period of inhibition depressed responses to testing stimulation of the suprasylvian gyrus. Similar results were obtained in experiments on animals with deep transcortical sections between the sensomotor and parietal regions, ruling out the possibility of interaction between the stimulated zones at the cortical level.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 2, pp. 142–148, March–April, 1981.     

Interaction between the human hippocampus and the caudate nucleus during route recognition

Navigation through familiar environments can rely upon distinct neural representations that are related to different memory systems with either the hippocampus or the caudate nucleus at their core. However, it is a fundamental question whether and how these systems interact during route recognition. To address this issue, we combined a functional neuroimaging approach with a naturally occurring, well-controlled human model of caudate nucleus dysfunction (i.e., preclinical and early-stage Huntington's disease). Our results reveal a noncompetitive interaction so that the hippocampus compensates for gradual caudate nucleus dysfunction with a gradual activity increase, maintaining normal behavior. Furthermore, we revealed an interaction between medial temporal and caudate activity in healthy subjects, which was adaptively modified in Huntington patients to allow compensatory hippocampal processing. Thus, the two memory systems contribute in a noncompetitive, cooperative manner to route recognition, which enables the hippocampus to compensate seamlessly for the functional degradation of the caudate nucleus.     

Dynamics of functional reciprocal connections between cerebral motor cortex neurons under stimulation in cats

Activity was recorded from neurons belonging to the representation of the forelimb in the motor cortex (sulcus cruciatus, L 7–9 mm) using multiple multi-channel/barrel electrodes during acute experiments on cats. Cross-correlation analysis of impulse trains was adopted to investigate dynamics of interneuronal connections during passive flexion and electrical stimulation of the limb contralateral to the recording site. It was found that neither passive bending nor electrical stimulation of the limb leads to a significant increase in the total number of direct relationships between cortical neurons. At the same time, passive flexion does produce a considerable decrease in the number of instances of both inputs operating in neighboring neurons (50–100 µm apart) and an increase in cells located further (between 100 and 400 µm) apart. Some increase in the number of direct inhibitory interactions between neighboring neurons was observed during electrical stimulation.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Nentskii Institute of Experimental Biology, Warsaw, Poland. Center of Experimental and Clinical Medicine, Warsaw, Poland. Translated from Neirofiziologiya, Vol. 23, No. 1, pp. 73–80, January–February, 1991.     

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.     

Mastication-related neurons in the orofacial first somatosensory cortex of awake cats

In the orofacial area of the first somatosensory cortex (SI), we recorded single unit activity from 699 neurons in 11 awake cats. Fifty-two percent (362/699) were mastication-related neurons (MRNs) showing activity related to some aspects of masticatory movements. MRNs were divided into three types by their activity patterns: (1) the rhythmical type, showing rhythmical bursts in pace with the masticatory rhythm; (2) the sustained type, showing a sustained firing during the period of taking food and (3) the transient (biting) type, showing intense discharges in coincidence with biting hard food. MRNs had mechanoreceptive fields in the perioral, tongue, periodontal and mandibular regions. The activities of perioral rhythmical-MRNs, mandibular transient-MRNs, tongue rhythmical-MRNs and periodontal transient-MRNs were correlated with food texture, while perioral rhythmical-MRNs, perioral sustained-MRNs and tongue sustained-MRMs were not. Both facial and intraoral MRNs were scattered throughout the facial and intraoral projection areas in SI. These findings provide evidence that the orofacial SI monitors masticatory movements for food ingestion.     

Multisensory convergence on neurons of the motor cortex in unanesthetized cats

Postsynaptic potentials (PSPs) of 83 neurons in the motor cortex of unanesthetized cats in response to electrodermal, photic, and acoustic stimulation were investigated by intra-and quasi-intracellular recording methods. Most cells responded to stimulation of at least one limb. About 60% of neurons of the posterior and over 75% of neurons of the anterior sigmoid gyrus responded to stimulation of two (or more) limbs. In 29 of 39 neurons of the anterior and 12 of 44 of the posterior sigmoid gyrus PSPs with a short (less than 50 msec) and stable latent period were evoked by flashes and clicks. On presentation of two somesthetic stimuli complete blocking (if the interval was less than 30–60 msec) or weakening (interval 30–200 msec) of responses to the second (testing) stimulus was observed. On presentation of paired photic (or acoustic) stimuli or paired stimuli of different modalities at various intervals from 0 to 100 msec, the testing response was often potentiated. The character of the responses and their interaction thus differed from those obtained under chloralose anesthesia [6, 7]. It is postulated that under the action of chloralose a system of neurons with strong excitatory feedback is formed in the motor cortex which may respond to stimuli of different modalities by something resembling the "all or nothing" principle.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 3, No. 6, pp. 563–573, November–December, 1971.     

Activity of sensorimotor cortex neurons during a dopaminergic transmission block in cats performing conditional reflex

Activity of sensorimotor cortex neurons was recorded in chronic experements on cats trained to perform instrumental conditional reflex; records were made before, during, and after isolated iontophoretic applications of haloperidol or glutamate, or their combined application. Haloperidol was shown either to facilitate or to inhibit the background and evoked (related to acoustic stimulation and motor response) spike activity of cortical neurons. Aftereffects of haloperidol were observed too; they were still expressed 10–15 min after the cessation of the iontophoresis. Combined haloperidol and glutamate application was followed by a sharp suppression of the evoked responses potentiated earlier by glutamate. An adenylatecyclase system is supposed to mediate the facilitation evoked by glutamate application. Some modulators, including dopamine, probably activate adenylatecyclase and in this way ensure facilitation of the glutamate-induced responses.Neirofiziologiya/Neurophysiology, Vol. 26, No. 5, pp. 347–355, September–October, 1994.     

Reduced high affinity cholecystokinin binding in hippocampus and frontal cortex of schizophrenic patients

Cholecystokinin (CCK) binding sites were assessed in post-mortem brain membrane preparations from controls and schizophrenic patients. 125I-BH CCK33 specific binding was reduced by 40% (p less than 0.02) in the hippocampus and by 20% (p less than 0.01) in the frontal cortex of schizophrenic patients compared with controls. There were no differences in 125I-BH CCK33 binding between the two groups in the amygdala, temporal cortex or caudate nucleus.