Ontogenesis of the asymmetry of transcallosal responses in the cat parietal cortex

In acute experiments on 2-24 days old immobilized kittens and adult cats, studies have been made on the development of functional interhemispheric asymmetry of homotopical transcallosal responses in the parietal cortex. It was found that the number of animals with evident asymmetry increases with age. Alongside, with respect to such characters as asymmetry coefficient, mean amplitude of components of transcallosal components and the ratio of zones of direct and inverse domination, the increase in functional interhemispheric asymmetry was observed during the second week of postnatal life of kittens, which was accompanied by the inversion of its sign; in adult cats, the decrease in the asymmetry up to its complete absence was found. The data obtained are discussed with respect to peculiarities of the development and functional properties of the associative parietal cortex in cats.     

Temporal organization of interneuronal relations in the cerebral cortex of the cat in relation to the level of alimentary motivation

By means of records of multicellular activity, interneuronal relations and their modifications in two cortical zones (Visual and motor) were studied in cats at different levels of alimentary motivation. For quantitative evaluation of interneuronal relations the statistic method of cross-correlation analysis of impulse trains was used in determining the probability of the appearance of the discharge of one neurone after the impulse of the other one. For groups of neurones in both investigated cortical areas, three-neurones microsystems were singled out and their activity was analyzed by temporal parameters of interaction between neurones at the interval of 120 ms, both within one microarea (intraanalyzer connections) and between microareas of two cortical zones. The correlation of temporal parameters of interneuronal connections (temporal delays in the activity of neuronal pairs) changed depending on spatial localization of neurones and functional condition of the animals. The existence is suggested of "informational" (1-30 ms) and "motivational" (90-120 ms) values of interneuronal relations for interanalyser connections.     

The phenomenon of the replication of ontogenetic immaturity in adult cats caused by the cerebrospinal fluid of kittens

Studies have been made on the electrical activity of muscles in the hindlimbs in kittens and adult cats before and after injection the liquor from 10-, 21-day and 1-month kittens into the lumbar part of the spinal cord. Analysis was made of the EMG at rest and that of the evoked reactions. It was shown that EMG of adult cats after injection of kitten liquor attained the pattern typical of the donor. The data obtained indicate the presence in kitten liquor of biologically active substances which account for the level of regulatory relationships. Transfer of these substances to adult animals results in the formation of a new level of coordinations of movements which corresponds to immature organism.     

A statistical analysis of the functional connections between the neurons of the visual and motor cortex in different forms of conditioned-reflex behavior]

In experiments on cats with elaboration of delayed alimentary operant reflexes to light organization was studied of interneuronal cortical connections. By means of cross-correlation analysis the dynamics of intra- and interstructural neuronal network was revealed at the level of cortical projections (visual and motor) of cats brain zones at three forms of behaviour: CR realization, in intersignal period with the presence and absence of operant movements. Depending on the forms of behaviour, predominance of "informational" or "motivational" interneuronal connections was observed.     

Organization of interneuronal relationships in the nucleus accumbens during impulsive and self-control behavior in cats

Under conditions of a choice between a high-valuable delayed and a low-valuable immediate food rewards, cats were divided into 3 groups on the basis of their individual strategy of behavior: (1) choosing predominantly the high-valuable reward because of inhibition of the instrumental response (capable of self-control), (2) choosing predominantly the immediate low-valuable reward (impulsive), and (3) with a mixed pattern of reactions (ambivalent). Coherent activity of nucleus accumbens neurons which was a characteristic of interactions between nearby cells was assessed by the method of crosscorrelation. It was found that the total number of interneuronal interactions in cats capable of self-control exceeded that displayed by impulsive cats. In those rare cases when impulsive cats performed long-latency responses not typical of them, the number of interneuronal interactions was the same as during the self-control behavior. In animals of different groups, the number of interneuronal interactions was higher during erroneous responses as compared to correctly performed reactions. The results suggest an important role of systemic activity of neurons in the nucleus accumbens in the organization of the long-latency reaction pattern, characteristic of self-control behavior.     

Formation of plastic connections of the visual system during ontogenesis of the rabbit

Analysis of evoked potentials and unit activity in the visual cortical projection area of rabbits revealed a definite succession of forming of interneuronal connections in ontogeny. In early postnatal period, the neuronal reactions were characterized by stable responses with one excitatory phase corresponding to initially negative surface evoked potential. Similarity of reactions of neurones situated in the same vertical column was observed and explained by functioning of a system of rigid connections of the thalamic relay nuclei afferents with cortical pyramidal neurones. Beginning from the third week of postnatal life of rabbits the neuronal reactions assumed a distinctly expressed phasic character, and variability of responses was seen along the vertical line. The changes revealed correlated with formation of a system of interneurones providing a possibility of plastic neuronal interaction. A study of the influence of preliminary cortical stimulation of the associative areas showed that intercentral cooperation mediated by cortical interneurones providing a systemic analysis of visual information began to form from the third week of postnatal life and reached the definitive level at later stages of development.     

Differential phosphorylation of tau proteins during kitten brain development and Alzheimer's disease

Differential distribution and phosphorylation of tau proteins were studied in developing kitten brain by using several antibodies, and was compared to phosphorylation in Alzheimer's disease. Several antibodies demonstrated the presence of phosphorylated tau proteins during kitten brain development and identified pathological structures in human brain tissue. Antibody AD2, recognized tau in kittens and adult cats, but reacted in Alzheimer's tissue only with a pathological tau form. Antibody AT8 was prominent in developing kitten neurons and was found in axons and dendrites. After the first postnatal month this phosphorylation type disappeared from axons. Furthermore, dephosphorylation of kitten tau with alkaline phosphatase abolished immunoreactivity of AT8, but not that of AD2, pointing to a protection of the AD2 epitope in cats. Tau proteins during early cat brain development are phosphorylated at several sites that are also phosphorylated in paired helical filaments during Alzheimer's disease. In either event, phosphorylation of tau may play a crucial role to modulate microtubule dynamics, contributing to increased microtubule instability and promoting growth of processes during neuronal development or changing dynamic properties of the cytoskeleton and contributing to the formation of pathological structures in neurodegenerative diseases.     

Conduction of excitation through the superior cervical ganglion during early postnatal development

The action of hexamethonium, D-tubocurarine, phentolamine, and atropine on synaptic transmission in the superior cervical ganglion was studied in the early stage of postnatal development (1–8 days after birth) and in the adult period in cats, rabbits, and rats. Hexamethonium and D-tubocurarine, if injected intravenously or added to the Krebs' solution surrounding the ganglion, were shown to inhibit the conduction of excitation through the ganglion effectively in both newborn and adult animals. No significant difference in the action of phentolamine and atropine on synaptic transmission in the ganglia could be found in these groups of animals. It is concluded that synaptic transmission in sympathetic ganglia is cholinergic in the early stage of postnatal development of animals blind at birth.     

The outlook for the experimental study of the network functions of cortical cells during learning]

The main outcome of the experiments described in the paper is an idea on the gnostic cortical microset. Multineuronal activity recorded from the motor cortex of cats with a conditioned response to time and the following cross-correlation analysis revealed a strict distribution of interneuronal connections within the microsystems (between the adjacent neurons) and variable connections between the remote neurons during the active waiting stage of two minute interval. Additional analysis of the narrow (0.5 ms) peaks of the histograms allowed to form a view on the synaptic interaction in time. It was found that there was different temporal distribution of the spikes in the peak obtained due to correlograms of neuronal pairs. Some cortical neurons demonstrated a visible synaptic activation at the end of the waiting period when other signs of the temporary behaviour were absent. Pharmacological testing functional interneuronal connections with acetylcholine and Ca(2+)-suppressing drug EGTA have raised a question on the neurochemical specificity of the intra- and extracortical synapses.     

Age differences in responsiveness of brainstem chemosensitive neurons to extracellular pH changes

The sensitivity of neurons in the caudal chemosensitive area on the ventrolateral surface of the medulla oblongata (VMS) to extracellular pH changes was examined in newborn and young developing kittens and compared to that of adult cats. The pH was varied by superfusion of the VMS with mock cerebrospinal fluid (CSF) of pH 7.4 (control), 7.0 (acid) and 7.8 (alkaline). A total of 97 neuronal units in the three age groups changed their firing rates inversely in response to extracellular fluid (ECF) pH changes. The greatest sensitivity was found in the adult group where acid superfusion caused an increase in neuronal activity. The least sensitivity was observed in the newborn group (1-6 days old), whereas the young kitten group (4-6 weeks old) exhibited an intermediate sensitivity. Neurons of kittens older than 7 weeks of age demonstrated a response pattern characteristic of the adult group. Neurons of neonates older than seven days, exhibited a response pattern characteristic of the young kitten group.     

Development of the hypothalamic-cortical interrelations in the ontogeny of the cat

Under chloralose narcosis, employing the evoked potentials method, studies have been made on the projection of the posterior hypothalamus to the frontal cortex in 1-30 days old kittens. The animals were divided into 3 age groups: 1-9, 10-19 and 20-30 days. Studies of the EPs in different points of pericruciate zone showed that these potentials are observed in all the investigated points from the first days of postnatal life. The latent period of responses in the youngest animals varied from 40 to 80 ms, exhibiting insignificant fluctuations depending on the cortical zone investigated. From the very beginning of postnatal life, in the same cortical zone the EPs may be observed in response to stimulation of the ischiadic nerve as well. In older animals, the latent period of the EPs decreases in all the points, the decrease being most significant near the crucial fissure. To the 30th day of postnatal life, the EPs in this zone with respect to their latency and configuration became quite similar to those in adult animals. In the third age period, the latency varies from 6 to 10 ms in the focus of maximum activity; with the removal of the recording electrode from this zone the latent period of the hypothalamo-cortical responses increases up to 30-40 ms. Overlapping of the EPs in response to central and peripheral stimulation was observed at all age periods.     

Synaptic connections of physiologically identified geniculocortical axons in kitten cortical area 17.

Single geniculocortical axons were recorded in the cortical white matter of kittens and adult cats by using micropipettes filled with horseradish peroxidase (HRP). Of 41 axons recovered in 4-5 week old kittens, three well-filled axons arborized in area 17; the remainder were incomplete or arborized in area 18. One axon had Y-like physiological properties, two were X-like. They were recovered from two 34-day-old kittens. All three axons formed clustered arborizations, mainly in layer 4A. Electron microscopic (EM) analysis of 50 boutons from kitten and 38 boutons from adult controls revealed that the boutons from kitten made synapses more frequently on spines (91% of targets) than did the boutons from the adult (71%). One X-like axon in kitten also had a collateral projection that made synapses in layer 1; this has not been seen in adult cats. In overall extent, the axons from kitten fell within the adult range.     

Activity of 3-neuron cortical microsystems in the cat during conditioned reflex switchover

Multiunit activity in two projection cortical areas (visual and motor) was studied in cats at conditioned switch-over of defensive and alimentary responses to electrostimulation of the visual pathways. Interneuronal relations of three-neuronal cortical microsystems (intra-analyzer connections) and relations between microsystems in the visual and motor cortical areas (inter-analyzers connections) were analysed by the method of crosscorrelation of action potential trains. Similar interneuronal relations were revealed in the motor microsystems and different relations were found in visual ones at elaboration of conditioned switch-over. This apparently indicates the leading role of the cortical projection of the signal stimulus in integration of adaptive behavioural act. On the other hand, the presence of common bonds for alimentary and defensive situations as well as of specific ones for each of them was shown in the distribution of interneuronal connections between the analyzers. The former apparently provide for the realization of the conditioned effector movement of the animal occurring in both situations with participation of the same effector organ (the tongue) The latter determine the character of the specific adaptive reaction.     

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.     

Development of stimulus selectivity and functional organization in the suprasylvian visual cortex of the cat

We have recorded from single neurons in the medial bank of the middle suprasylvian sulcus (PMLS) of anaesthetized and paralysed cats aged between nine days and eight weeks. Visual responses were assessed qualitatively, by using conventional projected stimuli, and quantitatively for drifting, high-contrast gratings of optimum spatial and temporal frequencies, but varying in orientation and direction of drift. At 9 days of age, some cells in the PMLS were spontaneously active but in three long penetrations only one visually responsive neuron was isolated. Between 9 and 15 days there was a rapid increase in the proportion of responsive units, which first appeared in small clusters in the lower layers (IV, V, VI). During the second and third postnatal weeks, spontaneous activity and the strength of visual responses increased to adult levels, and the proportion of cells showing rapid habituation to visual stimulation decreased. Even before two weeks of age, at least 85% of responsive cells in the PMLS were selective, by quantitative criteria, for image motion along one particular axis, and a majority of these were clearly direction-selective (responding to movement in one direction significantly more strongly than to that in the opposite). By the end of the third postnatal week the proportion of units with strong direction preference reached adult levels. The selective cells were initially more broadly 'tuned', on average, for the direction of motion of a grating (mean half-width in animals of 10-12 days was 32.6 degrees), but the sharpness of tuning improved to reach the adult level (ca. 23 degrees) during the third postnatal week. In animals younger than three weeks a slightly smaller proportion of cells than in adults (but always more than one third of all visually responsive cells) responded to stationary, contrast-modulated gratings. The majority of these cells showed clear selectivity for the orientation of a flashed grating. A few 'non-selective' cells were found in the youngest animals but by the end of the third postnatal week virtually all cells responsive to stationary gratings displayed orientation selectivity. There was always good agreement between the preferred orientations for stationary and drifting gratings. Even before two weeks of age, when responsive cells occurred only in small clusters, there was a clear tendency for neighbouring neurons to have similar or opposite preferred directions, just as in adult cats. By 2-3 weeks of age there were clear progressive shifts in stimulus preference along oblique or tangential tracks.(ABSTRACT TRUNCATED AT 400 WORDS)     

Neuronal Organization of Mammalian Stellate Ganglion in Postnatal Ontogenesis

The paper considers the problem of peculiarities of maturation of the stellate ganglion nerve elements in mammals of different species. This process differs in precocious and altricial animals. It has been shown that in spite of some individual peculiarities, the neurons, fibers, and conducting pathways in altricial animals are not, on the whole, completely formed morphologically and functionally. In the course of postnatal ontogenesis, not only an increase of cell sizes and development of dendrite tree, but also reorganization of nerve connections with target organ occur. The postnatal ontogenesis is also accompanied by an increase of the excitation transmission rate along the fibers and by their myelination. The asymmetry of the right and left stellate ganglia (SG) by their sizes and functional peculiarities, which exists in adult animals appears as soon as at early stages of postnatal development. The neural elements of precocious animals are changed to a lesser extent in postnatal ontogenesis and are, in many aspects, similar to those of adult organisms as early as at birth.     

Postnatal development of postganglionic parasympathetic neurones in the heart of the albino rat.

Electrical stimulation of the sinoatrial node region of isolated atria in medium containing physostigmine (0.1 micrograms/ml) produces a negative chronotropic effect whose intensity and duration depend mainly on the amount of acetylcholine released from postganglionic parasympathetic fibres endings. This technique was used to study functional maturation of the given neurones during postnatal development of albino rats. Preparations from animals of different ages were stimulated with 2-second bursts of rectangular pulses (frequency 50 Hz, pulse duration 0.02 ms, voltage 22.5--27.5 V) and frequency changes of the preparation were registered by recording extracellular action potentials. At 10 days the negative chronotropic effect is very weak and at 15 days it is only slightly stronger, but at 18 days it is almost the same as in adult animals. At 24 and 34 days the reaction is somewhat stronger than in adulthood. It can be concluded from these observations that functional maturation of the postganglionic parasympathetic neurones innervating the sinoatrial node in albino rats occurs between the 10th and 20th day of postnatal life.     

Functional characteristics of the developing brain after early postnatal neural immunization in rats: a behavioral analysis

In experiments on Wistar line young rats immunized in the early postnatal period with antigenic complexes of the nervous tissue of the hippocampus or the neocortex of an adult rat, the influence was studied of the change of the immunoreactivity to antigenic complexes of these structures on the functional brain development. Experimental animals were immunized twice in the age of 5 and 12 days or daily in the first 7 days of life. Studies of the behaviour of experimental and control animals in various situations, beginning from the two-weeks age, revealed expressed distinctions in the behaviour of animals, immunized by the hippocampus antigens: reduction of the capability to change the behaviour in changed experimental conditions (two-weeks age), and also a deficit of orienting (three weeks age) and conditioned (six weeks age) activities. A raised level was found of anticerebral antibodies in 1.5-months animals immunized in the early age. Suggestion is expressed about the significance of neuroimmune interaction in the mechanisms of the functional brain development.     

Functional organization of local neuronal networks in the cat neocortex. Dependence on the food motivation

The multiple unit activity (MUA) from clusters of adjacent neurones in deep layers of the frontal and motor cortex was recorded in alert cats with different levels of alimentary motivation. Up to 7 spike trains were selected from the MUA. Neurones in the local circuits could be divided into 2 groups: large neurones with prevailing divergent characteristics, and small neurones with prevailing convergent characteristics. A 24-hour food deprivation altered the cross-correlation interneuronal connections with a time delay within the range of 2 to 100 ms.     

Ultrastructural changes in the neurons and interneuronal synapses of the hypothalamus in the progeny of morphine-dependent rats

The electron microscopic method has revealed early maturation of the protein-synthesizing apparatus of some cells, on the one hand, and underdevelopment of neuroblast volumes, appearance of artificial contacts, axonal degeneration and destruction in large trunks, on the other hand. Compensatory-restorative processes in the cell on the 14th and 21st days of the postnatal development result in a complete restoration of morphological organization of neurons and interneuronal connections in the hypothalamus of offspring of the morphine-dependent rats.