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PubMedDate not supplied

[Formation of linear relations of potentials in the dog neocortex in a dynamic stereotype].

During elaboration of a stereotype system of defensive conditioned reflexes in dogs (Pavlov dynamic stereotype), a correlation spectral analysis was made of electrical activity in the neocortex. With a stable dynamic stereotype, substantial changes of background electrical activity were observed in the interstimuli periods, manifested in a significant growth of linear relations of cortical potentials at certain frequencies. This was expressed in separation from the wide-band random process (involving background activity before the formation of the dynamic stereotype) of definite, relatively narrow ranges of frequencies which formed the high coherence of the processes. No such changes of electrical activity were observed in conditioning without a stereotype; this points to special mechanisms of the dynamic stereotype, which differ from those of ordinary conditioned reflexes.

Animals↗
PubMed1976

[An analysis of the electrical responses of the neocortex evoked by stimulation of different hypothalamic structures].

Evoked potentials and extracellular spike activity during stimulation of the posterior, lateral, anterior, and ventro-medical hypothalamus were recorded in different areas of the neocortex in unanesthetized cats. Hypothalamo--cortical evoked potentials (HC EP) of maximal amplitude are generated in gyr. sigm. ant. with 0.5--2.5 msec latency. The responses are of positive--negative configuration and often a fast spike--like defiction appears at the positive phase. EP in gyr. suprasylv. med. are initially negative and of 2--6 msec latency. Most effective is stimulation of the posterior and lateral hypothalamus, HC EP in gyr. sigm. ant. following the frequency of stimulation up to 200/sec and being characterized not only by a high "functional lability" or reproducibility but also by the ability of posttetanic potentiation. With the aid of paired stimuli, the early fast component of the EP in the sensorimotor cortex was shown to appear at an interval of approximately 2 msec. HC EP entirely recover 50--150 msec after the conditioning stimulus. The recovery cycle is biphasic and reflect, a biphasic change of the excitability of neurons in gyr. sigm. ant. and suprasylvian associative areas of the cortex. The latency of evoked discharges of some neurons of the sensorimotor cortex during stimulation of the posterior hypothalamus, is 0.8--1.5 msec, which suggests the existence of a monosynaptic pathway for the hypothalamo--cortical discharges. The maximal amount of neurons in deep layers of gyr. sigm. ant. respond during development of the early and the main positive deflections of HC EP.

Animals↗
PubMed1976

[The effect of stimulation of the posterior hypothalamus on the electrical activity of the neocortex in chronically premesencephalic cats].

Experiments were carried out on 19 adult cats with chronic brain stem transections at the level of the foremost border of the supperior colliculus. High-frequency electric stimulation of the posterior hypothalamus produced in these cats desynchronization of electrical activity in different parts of the neocortex. A predominant influence from the posterior hypothalamus on the electrical activity of frontal lobes was observed. On the basis of the obtained data, it is suggested that the influences from posterior hypothalamus elicit neocortical activation via thalamic nuclei.

Animals↗
PubMed2003

Neuroprotective effects of nimodipine and MK-801 on acute infectious brain edema induced by injection of pertussis bacilli to neocortex of rats.

OBJECTIVE: To explore the mechanism and type of acute infectious brain edema induced by injection of pertussis bacilli (PB) in rat neocortex, to study the neuroprotective effect of non-competitive antagonist of N-methl-D-aspartate (NMDA) receptor (MK-801) and antagonist of Ca(2+) channels (nimodipine) on brain edema, and to investigate the relationship between percentage of water content and cytosolic free calcium concentration ([Ca(2+) ](i)) in synaptosomes or content of Evans Blue (EB). METHODS: 95 SD rats were randomly divided into five groups, ie, normal control group, sham-operated control group, PB group, nimodipine treatment group and MK-801 pretreatment group. The acute infectious brain edema was induced by injection of PB into the rats. Quantitative measurements of water content and the concentration of EB were performed. [Ca(2+) ](i) was determined in calcium fluorescent indication Fura-2/AM loaded neuronal synaptosome with a spectrofluorophotometer. To observe the effect of MK-801 and nimodipine, we administered MK-801 48 hours and 24 hours before the injection of PB in MK-801 pretreatment group, and nimodipine after the injection of PB in nimodipine treatment group. The specific binding of NMDA receptor was measured with [(3)H]-MK-801 in the neuronal membrane of cerebral cortex. RESULTS: The levels of water content and EB content of brain tissues, and [Ca(2+) ](i) in the neuronal synaptosomes increased more significantly in the PB-injected cerebral hemisphere in the PB group than those of normal control group and sham-operated control group (P<0.05). The water content and [Ca(2+) ](i) increased with the duration of infectious brain edema. Nimodipine administered after the injection of PB could significantly decrease the water content, EB and [Ca(2+) ](i) (P<0.05). MK-801 could significantly decrease the water content, EB and [Ca(2+) ](i) in 4 h and 24 h groups (P<0.05). The Kd values were 30.5 nmol/L+/-3.0 nmol/L and 42.1 nmol/L+/-4.2 nmol/L in PB group and NS group respectively (P<0.05), and Bmax were 0.606 pmol/mg.pro+/-0.087 pmol/mg.pro and 0.623 pmol/mg.pro+/-0.082 pmol/mg.pro respectively, without statistical significance (P>0.05). CONCLUSIONS: The changes in the permeability of blood-brain barrier (BBB) and Ca(2+)-overload may participate in the pathogenesis of infectious brain edema. Treatment with nimodipine can dramatically reduce the damage of brain edema and demonstrate neuroprotective effect on brain edema by inhibiting the excess of Ca(2+) influx and reducing the permeability of BBB. MK-801 pretreatment may inhibit the delayed Ca(2+) influx into the neurons. The infectious brain edema is not only cytotoxic brain edema (intracellular edema) but also vasogenic brain edema (extracellular edema) followed by earlier BBB breakdown, so infectious brain edema is complicated with brain edema.

Acute Disease↗
PubMed1998

Afferents to Visually Responsive Grafts of Embryonic Occipital Neocortex Tissue Implanted into V1 (Oc1) Cortical Area of Adult Rats.

The aim of this study is to determine, as precisely as possible, the topography and the density of host afferents to visually responsive grafts of occipital embryonic cells implanted in block form into the occipital neocortex of adult rats. The presence of visual activity in the grafts was assessed through field potential and single unit electrophysiological recordings. Field potentials appeared triphasic in shape, had low peak-to-peak amplitude (= 100 micro V), and had normal time latencies (˜ 30 msec). Polarity reversal was never observed. Single unit recordings showed that graft neurons exhibited normal (desynchronized) spontaneous activity, had discrete receptive fields (˜ 20 masculine in dia.), and responded to small stationary light flashes. A topic projection of the visual field in the grafts was also observed. Injections of cholera toxin sabunit B (CTB) into these responsive grafts induced retrograde labeling in almost all the brain regions normally projecting to the occipital cortical areas. The visual related cortical (Oc 1, Oc2) and thalamic (LP, LD, LGB) regions of the host provide the largest contingent (70-75%) of afferents to the graft. Finally, one of the major findings of this study is that 93-97% of the labeled cortical cells were found in cortical layers V and VI with a net preference for layer VI. A noticeable proportion of these layer VI labeled neurons (15-20%) was systematically observed in sublayer VIb, very close to, or even within, the white matter. We suggest thus that grafts inserted into the occipital cortex of adult rats receive functional visual inputs through various neuronal circuits. Visual inputs could be conveyed to graft eells by: (i) regenerating axons of geniculate neurons previously innervating the injured cortical site; (ii) formation of collateral branches from thalamic axons ending normally in the host cortex close to the graft boundary; and (iii) development of neuronal processes from cells located in the host cortex, mainly in layers V and VI of the occipital areas. Depending on multiple factors, yet unknown but very likely related to the host-graft integration, the cortical circuits might be either the principal afferent inflow to the graft or only a complement to the thalamic input.

Journal Article↗
PubMedDate not supplied

[The neuronal activity of suspension grafts of the neocortex].

Were compared electrophysiological characteristics of suspension (SUS) and solid (SOL) tissue grafts of embryonic neocortex transplanted into the barrel field of adult rats. The level of survival of SUS and SOL grafts did not differ significantly (89% and 95% correspondingly). All SUS grafts were integrated with the host brain judging by histological and electrophysiological criteria. Reactivity of neurons to electrical stimulation of the recipient's brain and to sensory (tactile) stimulation, as well as the latencies of on-responses were similar in both types of the grafts. However, proportion of neurons with on-responses was nearly twice lower in SUS grafts, while the number of neurons responding to tactile stimulation by primary suppression of activity was significantly higher than in SOL ones. It is suggested that the derangement of primary architectonics unavoidable during preparation of suspensions is responsible for the described differences between SUS and SOL grafts.

Animals↗
PubMed1992

[The ultrastructural changes in the hemato-encephalic barrier in the neocortex of rat progeny with prenatal exposures to desoxycorticosterone acetate].

Electron microscopic methods were used to study the antero-parietal area of the cortex of newborn rats from intact mothers (I group) and rats born after intramuscular injection of desoxycorticosterone acetate (DOCA) to pregnant rats during the III trimester (II group) in dose 10 mkg/100 g of the body mass or during the II-III trimester of gestation (III group) in dose of 2 mkg/100 g. By the moment of delivery the hormone dose in the both experimental groups was gradually decreased up to 0.8 mkg/100 g of the body mass. Prenatal treatment by DOCA resulted in the following changes in the structure of hematoencephalic barrier: ultrastructural changes of endotheliocytes and pericytes showing accelerated synthetic and metabolic processes; lengthening of interendotheliocytic dense junctions, increase of the amount of astroblast peduncles; accelerated development of the basement membrane (lengthening and thickening) and differentiation of astroblasts. Signs of accelerated differentiation of glioblasts and vascular wall were much more pronounced in the neocortex of the III group of animals. However, part of the vessels were surrounded by edema. The perivascular edema was accompanied by loosening of the basement membrane, flattening of endotheliocytes, pericytes and increase of their electron density.

Animals↗
PubMed1992

Suppression of spreading depression of Leão in neocortex by an N-methyl-D-aspartate receptor antagonist.

Spreading depression has been implicated in the pathophysiology of a number of diseases such as migraine, stroke and epilepsy. The characteristics of this phenomenon were explored in neocortex of anesthetized rats. Spreading depression was produced in 10 of 15 animals using mechanical, electrical and chemical stimulation. Mean amplitude of the DC shift was -9.3 mV, mean duration at any one electrode 65 sec and rate of spread 2-5 mm/min. Spreading depression was facilitated by focal interictal spike activity induced by penicillin and completely blocked by the N-methyl-D-aspartate (NMDA) receptor antagonist, DL-2-aminophosphonovaleric acid (APV), providing further evidence that excitatory amino acid neurotransmission is a critical element in the development or propagation of the phenomenon.

2-Amino-5-phosphonovalerate↗
PubMed1992

Amyotrophic lateral sclerosis, Parkinson's disease and Alzheimer's disease: phylogenetic disorders of the human neocortex sharing many characteristics.

Features common to amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD) and Alzheimer's disease (AD) are reviewed. Shared epidemiological aspects include an increasing frequency which is proportional for each disease. We draw attention to geographic non-uniform distribution which, for ALS and PD, correlates positively with latitude. Clinical and pathological overlap occurs in the same patients, and in members of the same family. A high early morning plasma cysteine/sulphate ratio possibly related to the development of proteinacious inclusions, as well as ubiquinated neuronal inclusions, characterize ALS, PD and AD. HLA-DR (the human group II major histocompatibility class) staining is marked in ALS, PD and AD and may represent autoimmunity-incited by-products of neuronal degeneration. Based upon demonstrated glutaminergic connections between the neocortex and anterior horn cells, the entorhinal cortex and the basal ganglia we hypothesize that ALS, AD and PD are phylogenetic disturbances of the neocortical cell. The postsynaptic neuron may degenerate secondarily to anterograde effects of deranged glutamate metabolism. Future therapeutic strategies should be directed to agents that decrease transmission induced by excitatory amino-acids.

Alzheimer Disease↗
PubMed1991

Effects of locus coeruleus activation on electroencephalographic activity in neocortex and hippocampus.

Experiments were conducted to examine the hypothesis that increased neuronal discharge activity of noradrenergic neurons of the locus coeruleus (LC) above resting discharge rates can alter forebrain electroencephalographic (EEG) activity. Small infusions (70-135 nl) of the cholinergic agonist bethanechol within 500 microns of the LC were used to activate this nucleus reversibly in halothane-anesthetized rats. A combined recording-infusion probe allowed verification of this electrophysiological activation. Simultaneously, EEG activity was recorded from sites in the frontal cortex and hippocampus and subjected to power-spectrum analyses. The findings were (1) LC activation was consistently followed, within 5 to 30 sec, by a shift from low-frequency, high-amplitude to high-frequency, low-amplitude EEG activity in frontal neocortex and by the appearance of intense theta-rhythm in the hippocampus; (2) forebrain EEG changes followed LC activation with similar latencies whether infusions were made lateral or medial to the LC; (3) infusions placed outside the immediate vicinity of the LC were not followed by these forebrain EEG effects; (4) following infusion-induced activation, forebrain EEG returned to preinfusion patterns with about the same time course as the recovery of LC activity (10-20 min for complete recovery). These infusion-induced effects on EEG activity were blocked or severely attenuated by pretreatment with the alpha 2-agonist clonidine, which inhibits LC discharge and norepinephrine release, or the beta-antagonist propranolol. These observations indicate that enhanced LC discharge activity is the crucial mediating event for the infusion-induced changes in forebrain EEG activity observed under these conditions and suggest that LC activation may be sufficient to induce EEG signs of cortical and hippocampal activation.

Animals↗
PubMed1990

[Structure of the neocortex of the Baikal ringed seal (Pusa sibirica Gm.)].

The sulci and gyri of the neocortex, as well as cyto-, synaptoarchitectonics and neuronal composition of the sensomotor (brain area) have been studied in the Baikal ringed seal. The structure of the sulci and gyri have been found to be similar to that in carnivores. The following specific features have been revealed in the brain of this endemic species: a thick layer I, presence of giant pyramidal cells in the layer III, large mitochondria in the presynaptic parts and dendrites. The results obtained are discussed concerning adaptation to semiaqueous way of life and to diving.

Adaptation, Physiological↗
PubMed1991

Cytoarchitectonics of some cortical areas of the feline neocortex (a quantitative study in semithin sections).

This paper presents quantitative analysis of the size of neurons in individual architectonic layers of the neocortex of the cat. In semithin sections the area, perimeter and maximal diameter of the perikarya and their nuclei were measured. Eight different cortical areas were evaluated, including the motor cortex (anterior and lateral sigmoid gyrus), the sensory cortex (coronal gyrus and anterior ectosylvian gyrus), the association cortex (lateral gyrus), the auditory cortex (medial and posterior ectosylvian gyrus) and the visual cortex (occipital gyrus). The obtained quantitative data are summarized in tables.

Animals↗
PubMed1991

[A cross-correlational analysis of the background neuronal pulse trains in surviving slices of the guinea pig neocortex].

Cross-correlation analysis of interdependence of the background spike activity was carried out for pairs of adjacent neurons simultaneously recorded in the incubated slices of the neocortex of guinea-pig. Statistical correlation of spike discharges was detected in 16 out of 26 recorded pairs of the neurons. Significant correlation was observed mainly in the range of +/- 100 ms from the null point. Cross-correlation had symmetric or asymmetric maxima up to 150 ms long and negative shifts up to 200 ms long. More complex positive-negative types of cross-correlations were also obtained. The data were compared to those known from other authors for the intact brain. The contribution of intrinsic intracortical interactions and extrinsic afferent influences in these correlations of activity is discussed.

Animals↗
PubMed1991

[An embryonic tissue xenograft of neocortex in old rats].

To 31 2-3-year-old white noninbred rats transplantation of the neocortical tissue, obtained from human embryos 12-20-week-old has been performed. Under aseptic conditions after an osseous-plasty cranial trepanation (thiopental narcosis intraperitoneally) tissue pieces 2 x 3 mm have been put into an artificially made cavity in the cortex of the right parietal region. In 3-4 weeks after the operation, reparation takes place at the intracellular level both in neurons and in microglial elements, both hemispheres being involved in the process of compensatory-restoration process equivalently: realization of regeneration is performed in the brain as a single organ. The working hypertrophy of the neurons results from increase of both the perikaryon and the previously shrunken nucleus against the background of their normochromia and distinct structurally. Therefore, massive diffusive dystrophy of nervous cells disappears. Amount of microglial elements increases essentially. A close contact of neurons with satellite cells demonstrates certain activation of a single metabolic system neuron-neuroglia. Thus, xenotransplantation of the embryonal tissue of the neocortex to old animals produces a positive reparative process in involutively altered neurons and in macroglial elements.

Aging↗
PubMed1990

[Sexual differences in the interhemispheric asymmetry of the transcallosal responses of the associative areas in the cat neocortex].

Sex differences of hemisphere asymmetry of homo- and heterotopic transcallosal responses in association cortex of 48 cats (24 male and 24 female) immobilized by tubocurarine have been studied by means of topographic EPs recordings in both hemispheres. In males left hemisphere dominates by the amplitude of homotopic and positive wave of heterotopic EPs and right hemisphere dominates by the amplitude of negative wave of heterotopic sensorimotor cortex EPs. The individual asymmetry of EPs has been observed in sensomotor cortex of females and in parietal cortex of animals of both sex. The interhemispheric asymmetry is expressed distinctly in females than in males. It is concluded that sex dimorphism is present in functional organization of associative system of (callosal and intracortical) connections in cat's neocortex projection and association areas which means its more expressed hemisphere lateralization in males with more expressed interhemispheric asymmetry of functional transcallosal connections in females.

Animals↗
PubMedDate not supplied

[A spectral-correlational analysis of the EEG of the neocortex in the rabbit in a state of thirst].

Summate electrical activity of the rabbit neocortex during formation of drinking excitation was studied by means of mathematical analysis. It is shown that the change of the electrical activity depends on the level of drinking excitability created by various duration of water deprivation (24-48 h) and is expressed in a generalized lowering of potentials amplitude without frequency change. Spectro-correlative EEG analysis showed that lowering of spectrum power took place within the whole analyzed frequencies range. Besides, an increase took place of interconnections of the cortical electrical processes, estimated by coherence function. It may by suggested that the manifested reconstruction of spectro-correlative characteristics of the neocortical biopotentials reflects a formation of motivational excitation establishing optimal level of cortex functioning.

Animals↗
PubMed1990

[The postsynaptic components of the paroxysmal reactions of the neurons in the strychninized neocortex].

Intracellular responses of neurons of cortical strychninized suprasylvian gyrus were investigated in experiments on immobilized and unanaesthetized cats. Paroxysmal depolarizing shifts (PDS) of the neuronal membrane potential were registered. They consisted of the burst discharge (BD) and slow depolarization wave. By means of intracellular stimulation it was shown that PDS could be summarized and were able to change their form and size. BD in PDS were triggered by large EPSPs which could be elicited from paroxysmal responses. Presumably, the intradendritic recordings have shown the presence of large EPSPs during generation of epileptiform discharges in the neocortex. In some neurons PDSs were accompanied by hyperpolarizing potentials which were apparently IPSPs because they were reversed at the intracellular Cl- injections. The contribution of excitatory and inhibitory synaptic influences to the neuronal paroxysmal responses is discussed.

Animals↗
PubMed1990

[The individual variability of pyramidal neurons in the neocortex of the rat].

In Golgi-Kopsch impregnated pyramid neurons of the neocortex (regio precentralis agranularis and area striata) of adult rats the individual variability was investigated. As parameters served the dendritic lengths, spine numbers and spine densities along the dendritic orders (basal and apical), within single dendritic fields, the apical and basal parts of the dendritic tree and of the whole neuron. The statistical tests gave the following results: Pyramid neurons in the regio precentralis agranularis are more variable than pyramid neurons in the area striata. Within the area striata the lamina III-pyramid neurons are more invariable than the lamina V-pyramid neurons. The basal dendrites are statistically more invariable than the apical dendrites. The dendritic lengths are less variable than the spine values. In general, the variability is different in particular subdivisions of the neurons analyzed as well as for the parameter chosen. The variability of neuronal structures depends from genetical factors and from a functional training. The knowledges about this variability are still insufficient. They are of considerable importance for the planning of experiments followed by statistical analyses.

Animals↗