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At least 1,099 records · Page 61Linked to original sources
PubMed1984

[Synaptic plasticity at the levels of the archicortex and neocortex].

A review of the author's studies of properties and mechanisms of long-term potentiation (LTP) is presented. LTP of field potentials and neuronal responses at hippocampal CA1 and CA3 regions of unanaesthetized rabbit was found. Excitatory and inhibitory post-synaptic potentials increased after tetanization. Microiontophoretic and histochemical studies revealed no appropriate changes in acetylcholine sensitivity or in acetylcholinesterase activity to explain LTP. Quantal analysis of EPSP evoked by microstimulation indicated increase in the number of transmitter quanta released by a presynaptic spike. LTP of field potentials evoked by white matter stimulation at neocortical slices and sensorimotor cortex of unanaesthetized rabbit are described. Changes in short-latency neuronal responses and "indirect" component of pyramidal tract response suggest monosynaptic LTP at neocortex. It is concluded that the main mechanism of both hippocampal and neocortical LTP consists of an increase in efficacy of excitatory synapses. It is suggested that these synapses are used in learning and memory processes.

Acetylcholine↗
PubMedDate not supplied

[Role of cholinergic mechanisms in the regulation of ATPase activity and the intensity of glycolysis in the rat neocortex, hippocampus and brain stem].

It was shown in experiments in rats that the increase in the level of endogenous acetylcholine induced by galanthamine entails a reduction in Na+, K+-ATPase of neocortical, hippocampal and truncus cerebri microsomes, and in the content of lactic acid in the brain structures in question. Blockage of M-cholinoreceptors with metamisyl is accompanied by the decreased activity of Na+, K+-ATPase in the neocortex and by its elevation in the truncus cerebri. At the same time the content of lactic acid in the cortex rises and that in the truncus cerebri diminishes. No substantial changes in both the biochemical indicators were recorded in the hippocamp. Inhibition of the central N-cholinoreceptors with eterofen reduces the glycolysis intensity in the truncus cerebri and hippocamp. Meanwhile Na+, K+-ATPase activity in the brain structures remains unchanged.

Animals↗
PubMed1978

[Postnatal histogenesis and cell proliferation in the parietal region of mouse neocortex under normal conditions and following brain injury].

Postnatal histogenesis of the parietal area of the neocortex and proliferative capacity in it of the main cell types were studied in mice under normal conditions and in stab wound of the brain by analysing 3H-thymidine-labeled cells on semithin sections. As revealed, microneurons failed to form in the parietal cortex of mice during the postnatal period either by migration of undifferentiated cells or by proliferation. Injury of the right hemisphere did not cause any change in the way of histogenetic transformations of cells migrating into the cortex of the parietal area in the direction of their differentiation into microneurons.

Animals↗
PubMed1984

Penicillin-induced epileptic phenomena in the rabbit's neocortex II. Laminar specific generation of interictal spikes after the application of penicillin to different cortical depths.

To elucidate the generation mechanisms of interictal spikes we analyzed the electrical events in the different layers of the rabbit's neocortex after application of penicillin to distinct cortical layers. Field potentials (FP) recorded simultaneously from all layers with a 16-fold micro-electrode-assembly were subjected to current-source-density analysis (CSD), which allows a more accurate description of local electrical events. To demonstrate the influence of neocortical architectonics on the generation of interictal spikes, 3 different areas-area occipitalis 1, precentralis 1 and 2, according to Fleischhauer et al., were studied. Interictal spikes develop regardless of the depth of PNC application. Moreover the appearance of spikes does not seem to depend exclusively on the diffusion of PNC into a distinct cortical layer (i.e. layers IV and V). The CSD analysis indicated that different generation mechanisms within the different cortical layers underly the spikes. According to CSD configurations maximum sinks occur at depths where the dendrites join closely to form bundles. This finding supports the importance of dendrites for the generation of interictal spikes. Finally, the distribution of CSD patterns is similar in all 3 neocortical areas studied, if PNC is applied to the same cortical depth.

Animals↗
PubMed1983

[Dynamics of the interaction of hypothalamic, reticular and limbic structures and the neocortex as affected by corticosteroids].

The neurophysiological analysis of the hypothalamo-reticulo-lambic structures and neocortex and dynamics of their relationship simultaneously with the content determination of the corticosteroids in rats and rabbits blood under the influence of hydrocortisone and 11-deoxycorticosterone has been carried out. It has been shown that the hypothalamo-reticulo-limbic system are involved under the action of adrenal hormones. Under the influence of corticosteroids the dynamics of changes of these structures ensuring the functions of hypophysal-adrenal complex are condition to transfer the neuroendocrine system into the new state forming definite behavioral reactions to support homeostasis.

Adrenal Cortex Hormones↗
PubMed1980

[Adenosine and its derivatives released by neocortex synaptosomes of the guinea pig].

Nerve endings (synaptosomes) prepared from guinea-pig neocortex were loaded with [14C] adenosine at 37 degrees C during a 30 min incubation. After the removal of the extracellular adenosine, the preparations were superfused and adenosine derivatives were analyzed in the superfusion fluid. The measurement of the amounts of [14C] nucleotides released in the presence or absence of metabolic inhibitor allowed us to conclude that adenosine and to a smaller extent inosine, are the molecules released from the synaptosomes during superfusion.

Adenine↗
PubMed1982

[Noradrenergic innervation of rat neocortex during development: immunocytochemical evidence using anti-dopamine-beta-hydroxylase antibodies].

Dopamine-beta-hydroxylase (DBH), the synthetizing enzyme for norepinephrine, has been visualized by immunofluorescence technique ontogeny in the Rat cerebral cortex. DBH like immunoreactive fibers develop as two bundles, one in the marginal zone observed at embryonic day 19 and another in the deep cortex visible at birth. These plexuses rapidly invade the whole neocortex following a rostro-caudal gradient. Five days after birth, all cortical layers show DBH containing fibers but the adult pattern is only reached two weeks after birth.

Aging↗
PubMed1983

[Changes in the proximal axon segment in layer III pyramidal cells in the neocortex of aged humans. A Golgi study].

In the neocortex (in area 11) of the non-demented aged humans (average age: 72.6 years) preferably the pyramidal cells of layer III are subjected to a conspicuous aged-related alteration in that they develop spindle-shaped enlargements of their proximal axon segment. We found different degrees of these enlargements. A slender process arises distally from the dilatation showing the morphological characteristics of the axon. In Golgi impregnations, such layer III pyramidal cells with an axon alteration do not display obvious changes in the ramification or spine density of their dendrites.

Aged↗
PubMed1982

[Changes in neocortex function in the direct action of optical radiation].

Direct action of ultraviolet radiation with wavelength of 280, 310 and 365 nm increased the amplitude of neocortex EEG and enhanced the epileptiform activity in the penicillin--induced epileptic focus, whereas action of superthreshold radiation with wavelength of 580 and 630 nm decreased the EEG amplitude and suppressed the epileptiform activity. The mechanism of ultraviolet radiation effect on the neocortical electrical activity seems to be based on changes in permeability of neuronal membranes for Na and K ions and on following depolarization of the membranes, whereas the action of visible radiation leads to the heat injuring of neurons in the irradiated area which evokes irreversible suppression of their activity and reducing of their EEG amplitude.

Animals↗
PubMed1982

[Reorganization patterns in the synaptic architectonics of the neocortex in the postresuscitation period].

Staining of brain tissue with phosphotungstic acid was used to assay interneuronal contacts in the molecular layer of the cerebral cortex of rats with a history of clinical death because of hemorrhage and asphyxia. Common regularities of reconstruction of neocortical architectonics during the resuscitation period were defined. Marked reduction in the number of synapses was discovered in the neocortex. The main form of destruction of the contacts was the light type of destruction. Hypertrophy of the remaining synapses occurs in the early periods. The processes of neosynaptogenesis get activated on day 7. Both the types of structural recovery of the synaptic pool (hypertrophy and neoformation of the contacts) were fairly marked in the long-term period.

Animals↗
PubMedDate not supplied

[EEG activity of symmetrical points of the cerebral cortex during unilateral cooling of the temporal neocortex in cats].

A study of ten alert cats has shown that inactivation with cold of the temporal neocortex elicits a sharp drop in EEG activity in all the examined points of the homonymous hemisphere, which actually points to a temporary switching off of its function. At the same time a unilateral switching off of the temporal area brings about an increase in EEG activity of the contralateral hemisphere. Functional asymmetry sets in not only in the system of the auditory analyser, but also in other sensory systems. Systematic cold switching off of the temporal cortex in one hemisphere results in a reduced contrast in the EEG of the brain symmetrical regions.

Animals↗
PubMedDate not supplied

[Interrelations between biopotentials of the neocortex, archicortex and intermediate cortex during formation of conditioned reflexes to time].

By means of instrumental food-procuring technique in chronic experiments on dogs, it was shown that during formation of the reflex to time, two complexly interacting systems of bioelectrical activity appear in the EEG in the form of rapid 28-32 c/s spindles in the neocortex (motor and parietal cortex) and slow (4-7 c/s) activity in the hippocampus and entorhinal cortex. The involvement of both structures in the mechanisms of voluntary activity is analyzed.

Animals↗
PubMedDate not supplied

[Functional interactions between the rabbit hypothalamus and neocortex].

In acute experiments on rabbits under chloralose-nembutal anaesthesia, studies have been made on the distribution and the pattern of the evoked potentials (EP) in neocortical structures of the brain cortex during electrical stimulation of different hypothalamic nuclei. It was found that during stimulation of the supramammilar area of the hypothalamus, the focus of maximum activity of cortical responses of the negative-positive configuration is localised in the median parts of precentral agranular region. During stimulation of the posterior hypothalamic area, the EP were of the positive-negative-positive type. Registration of the EP in different cortical layers during stimulation of the posterior hypothlamic nuclei showed that from 100 to 100 micrograms the amplitude of EP components decreases, whereas at the level of 600 mu the inversion of the EP takes place. At the depth of 1.800 mu the EP elicited by stimulation of the posterior hypothalamus had a form of a positive oscillation with a long latent period. It is concluded that the posterior hypothalamic nuclei have a vast representation in rabbit neocortex, this representation being realized by both polysynaptic and olygosynaptic systems of connections.

Animals↗
PubMed1980

[Formation of determinant structures and functional complexes in the neocortex when the brain is transected at different levels].

A strychnine focus created in the cat neocortex preparations with mediopontine section and encephale isolé, increased activity in other weaker foci, synchronized discharges in them, united them into a functional complex and determined the character of the whole complex activity. Such an hyperactive focus plays an active role of the determinant structure. In cortex isolé and preparations with mesencephalic section of the stem, a more rapid formation of functional complexes occurred under the effect of determinant focus. Complete elimination of the afferent and thalamo-cortical interactions seems to hinder neither the hypersynchronization of cortex neuronal elements, nor the formation of functional complexes, nor the generalization of seizure activity over the cortex.

Animals↗
PubMedDate not supplied

[Functional state of the CNS at extreme levels of spatial synchronization of background potentials of rabbit neocortex].

Neurophysiological mechanisms of facilitation of excitation transmission from receptors to effectors were studied in the case of maximal correlation between cortical potentials. This condition was accompanied by a rise in excitability of the sensorimotor, visual, auditory cortex and of the dorsal hippocampus as well as by an increase of muscle activity. On the basis of the obtained and literature data it is suggested that maximal synchroneity of cortical potentials reflects a certain state not only of the neocortex, but also of other CNS parts, down to spinal centres. This condition is attended with facilitation of excitation irradiation and of its transmission to motor periphery.

Afferent Pathways↗
PubMedDate not supplied

[Effect of damage to the associative zones of the neocortex on visuomotor coordination in cats].

The changes in characteristics of motor reactions, performed under constant visual control, were studied after lesion of separate associative zones in the cat neocortex. It was shown that the ability to perform a given task is impaired after local lesions of the sensorimotor cortex and extensive ablation of the parietal cortical areas. At the same time an increase of reaction temporal parameters is noted, which correlates with changes in the strategy of animal's search movements. Alone the ablation of the occipital areas does not impair the task performance. In case of local lesion of the parietal areas and the frontal pole of the cortex the preoperational level of task performance is preserved, but the time of search increases and the pattern of search movements is changed specifically for each cortical area.

Animals↗
PubMed1978

Postnatal development of the mouse cerebral neocortex. IV. Evolution of the total cortical volume, of the population of neurons and glial cells.

The total neocortical volume delimited between precise anatomical features was measured. Serial frontal sections cresyl-violet stained were measured with plainimetric methods and the total volume evaluated at 5, 10, 30, 60 and 180 days. The total volume was used to obtain the total number of neurons and glial cells at each age using our quantitative data (published in our previous papers). The evolution of the cellular densities were studied in the sensory and motor areas 10--4--3 and 2 (Leuba and coll. 1977) and in the visual and auditory areas 17--18a--18--41 and 20 (Heumann anc coll. 1977) in the mouse cerebral neocortex. 1. The total neocortical volume increases rapidly between 5 and 10 days, less between 10 and 30 days, slightly decreases at 60 days and reincreases at 180 days. 2. Between 5 and 30 days, the loss of cortical neurons is of about 30% by neuronal death. 3. The total number of glial cells doubles between 5 and 180 days. The increase is progressive through the development.

Animals↗
PubMed1994

Three classes of GABAergic interneurons in neocortex and neostriatum.

We have compared the cellular organization of GABAergic interneurons between frontal cortex and neostriatum of rats by immunohistochemistry for calcium-binding proteins, somatostatin and nitric oxide synthase (NOS). GABAergic interneurons in both neocortex and neostriatum could be divided into three separate populations containing parvalbumin, somatostatin, or calretinin. NOS cells were considered to be GABAergic and belong to somatostatin cells in both structures. Distributions of calbindin D28k in three classes of interneurons were different among neocortical layers and neostriatum.

Amino Acid Oxidoreductases↗