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At least 253 records · Page 14Linked to original sources

PubMed1990

3 beta-hydroxysteroid dehydrogenase/isomerase in the fetal zone and neocortex of the human fetal adrenal gland.

The fetal zone of the human fetal adrenal (HFA) gland is established to have decreased 3 beta-hydroxysteroid dehydrogenase/delta 4-5 isomerase (3 beta HSD) activity compared to the neocortex or definitive zone. 3 beta HSD activity, however, can be induced in primary cell culture through treatment with ACTH. Therefore, the HFA with two distinct steroidogenic zones with differences in 3 beta HSD activity as well as the capacity to increase 3 beta HSD activity in response to ACTH provides an excellent model to study the regulation of this enzyme. The presence of 3 beta HSD in the fetal and neocortex zones of the HFA was examined using a polyclonal antibody raised against purified human placental microsomal 3 beta HSD. After homogenates of the fetal and neocortical zones of the HFA were electrophoresed on a sodium dodecyl sulfate-polyacrylamide gel and immunoblotted, the presence of the 3 beta HSD protein with a molecular size of 45 kDa could be demonstrated only in the neocortical zone. ACTH treatment (greater than 2 days) of fetal and neocortical zone explant cultures produced increases in cortisol secretion associated with the respective levels of immunodetectable 3 beta HSD protein. Cortisol and dehydroepiandrosterone sulfate were the respective principal steroid products of neocortical and fetal zone explants. After ACTH treatment, immunodetectable 3 beta HSD was induced to a greater magnitude in the neocortex. These findings provide evidence that the lack of 3 beta HSD activity in the fetal zone, previously considered to be the result of the presence of an endogenous inhibitor, is due to an absence of the protein in this portion of the gland. The lack or minimal expression of 3 beta HSD in the fetal zone of HFA may be due to the action (or lack thereof) of a tissue-specific factor regulating the synthesis of 3 beta HSD.

3-Hydroxysteroid Dehydrogenases↗

PubMed1994

Left temporal neocortex mediation of verbal memory: evidence from functional mapping with cortical stimulation.

We examined the contribution of the temporal neocortex to short-term memory (STM) in 15 patients with left hemisphere language dominance during intraoperative or extraoperative cortical mapping prior to left anterior temporal lobectomy. Recall errors were examined following stimulation during the acquisition, consolidation, and retrieval stages of a verbal STM task. Ten patients showed stimulation-induced recall errors, and five patients showed no significant memory errors. More patients showed errors following stimulation during consolidation than during acquisition or retrieval, possibly because of disrupted transfer of information from the temporal neocortex to the hippocampus. Patients with stimulation-induced recall errors did not differ significantly from patients without memory errors in terms of seizure, demographic, or neuropsychological variables. Patients with resection of sites showing stimulation-induced recall errors had greater postoperative decline in verbal memory than did patients with resection sparing these sites. We suggest that the left temporal neocortex contributes to verbal memory consolidation in patients with chronic epilepsy.

Adult↗

PubMed1990

Long-term potentiation and depression in the cerebral neocortex.

Long-term potentiation of synaptic efficacy following tetanic synaptic inputs was described originally in the hippocampus, and it has been studied extensively based on the hypothesis that it represents a synaptic model of learning and memory in the brain. In the cerebral neocortex, studies on LTP have burgeoned later, and have progressed less rapidly than those in the hippocampus. Recently, however, experimental data describing the phenomenology and the mechanisms underlying LTP have accumulated in the neocortex, particularly in the visual, somatosensory, and motor cortices. In the developing visual cortex, LTP has been induced by afferent tetanic stimulation at relatively low frequencies, for long duration. Thus, particular attention has been given to parameters of the tetanus optimal for the induction of cortical LTP, and the differences between these and those effective in inducing hippocampal LTP have been reviewed. In the motor cortex, the associative LTP following combined activation of separate sites as well as homosynaptic LTP following activation of single pathways have been reported and these types of synaptic plasticity have been suggested as being a basis for a certain type of motor learning. Long-lasting depression (LTD) of synaptic efficacy also has been reported in the developing visual cortex and suggested as a neural basis for experience-dependent modifications of visual cortical neurons. LTD has been found in other areas of the neocortex as well, although the probability of its induction is relatively low and its functional significance is not yet clear. Among the possible mechanisms for the induction of LTP and LTD, those including the involvement of NMDA receptors, protein kinase C, Ca2+/calmodulin-dependent kinase II, and membrane-associated cytoskeletal proteins have been reviewed, although the results obtained so far are only fragmentary and are premature for definitive conclusions to be drawn.

Animals↗

PubMedDate not supplied

[The effect of cryogenic exclusion of the neocortex on preservation of the functioning of its temporal regions].

In chronic experiments on nine cats a study was made of different forms of their behavior in conditions of cold elimination of the cerebral cortex with the exception of the temporal areas. The first sessions of cooling produced a diminution of alimentary excitability, enhanced motor activity, loss of the reaction of mouse chasing and of a defensive reaction against the dog, and a disappearance of previously elaborated conditioned runnings to the feeding trough, etc. In the course of subsequent experiments with the neocortex cooling, the disturbed forms of behavior were restored. In the second and third sessions alimentary excitation was considerably restored; by the sixth and seventh sessions motor activity became normal, while the 20th to 25th sessions exhibited a protective reaction against the dog. Conditioned runnings restored in the seventinth session were manifest in the 20th to 25th sessions in 80% of cases. It is assumed that the temporal areas of the neocortex while playing a considerable part in integrating the activity of the whole brain, including the formation and manifestation of conditioned reflexes, under normal conditions, to a large extent lose their integrative role when the rest of the neocortex is elimated.

Agonistic Behavior↗

PubMed1976

[The role of several brain stem structures in activation of the neocortex and motor reflexes in chronically premesencephalic cats].

Chronic experiments were carried out in 18 cats. After premesencephalic section of the brain-stem, the neocortex can be activated both spontaneously and in response to the posterior hypothalamus or the forepaw skin stimulation. After bilateral lesions in the posterior hypothalamus, neither spontaneous nor the forepaw-skin stimulation-produced activation of the neocortex, was observed. Excitation of the mesencephalic RF is accompanied by activation of motor reflexes. A conclusion was made that the posterior hypothalamus, independently of the mesencephalic RF, is capable of activating the neocortex, while the mesencephalic RF, independently of the rostral structures, is responsible for the motor reflex activation.

Animals↗

PubMed1992

The size of the neocortex in relation to ecology and social structure in monkeys and apes.

In an attempt to reveal factors associated with neocortical development in monkeys and apes (anthropoids), relationships between the relative size of the neocortex and differences in ecology and social structure were examined for 24 genera of 11 subfamilies. Relative sizes of the neocortex (RSNs) in a given group were assessed as the difference between actual neocortical volume and the volume expected from an allometric relationship between neocortical volume and the volume of the rest of the brain. We found that RSNs are related to diet and social structure: frugivorous anthropoids had higher values of RSNs than folivorous anthropoids, and polygynous anthropoids had significantly higher values of RSNs than monogynous anthropoids. Furthermore, RSNs were positively correlated with the size of the troop. These results suggest that development of the neocortex is associated with both diet and social structure in anthropoids.

Animals↗

PubMedDate not supplied

[The structural-functional characteristics of the rostral sections of the neocortex in Chiroptera].

Studies have been made on the connections of rostral neocortex in bats in order to reveal connections with the structures of the auditory sensory system the existence of which is indicated by evident specific responses to ultrasound in the form of synchronization reaction. It was shown that dorsolateral parts of the rostral neocortex receive topically organized projections from the thalamic nuclei VPL and VL. Connections with the auditory cortex and suprageniculate nucleus are not evident. Afferents of the medial wall of the rostral cortex originate from the thalamic nuclei MD and AM. Possible pathways of auditory afferentation to the dorso-lateral part of rostral neocortex are discussed.

Acoustic Stimulation↗

PubMed1990

Relation of the insular claustrum to the neocortex in Insectivora.

The claustra of 9 species of Insectivora (Sorex araneus, Sorex minutus, Tenrec ecaudatus, Solenodon paradoxus, Neomys fodiens, Erinaceus europaeus, Talpa europaea, Desmana moschata, Potamogale velox) were investigated. In all examined animals we found two parts of the insular claustrum: the main part called by us the pars principalis and more medially situated lamina profunda claustri. In the "basal" Insectivora the main part is in close contact with the layer VIa of the neocortex. In some more developed "basal" and in all "progressive" Insectivora the area capsularis appears. Dorsolaterally it separates the main part of the insular claustrum from the neocortex and possesses, besides neurons, also numerous fibers of the extreme capsule. The above data strongly suggest that in the phylogenesis the insular claustrum originates from the cortex from which it gets separated by the extreme capsule. Lamina profunda claustri is rather a narrow band of neurons situated on the medial side of the pars principalis and mostly separated from it by a thin lamina of white substance. Lamina profunda is continuous with the layer VIb of the neocortex.

Animals↗

PubMed1991

[The comparative characteristics of the neuronal activity in surviving slices of transplanted and intact neocortex].

The background single unit activity and single or multiunit responses to electrical stimulation of the rat's embryonic cortex, grafted into the somatosensory cortex of adult rats were investigated in a slice preparation. The same characteristics of the intact cortex neurons were observed as a control. The percentage of neurons with background activity within grafts was higher, than that within intact neocortex slices (23% and 6%, respectively). However the percentage of neurons responding to electrical stimulation of the recipient neocortex was lower in grafts. The mean latency of multiunit responses of graft neurons was longer, than that of neurons of the intact neocortex recorded at the same distance from the stimulating electrode (19.4 +/- 5.0 and 5.8 +/- 1.1 ms, respectively). Duration of the evoked population discharges was approximately ten times longer in grafts. It is concluded that there are local functional connections between a graft and the host brain and that inhibitory processes within grafts are weak. Functional integration of grafts with the host brain of the recipients after cranial trauma is shown.

Animals↗

PubMed1990

[Cases of numerous diffuse plaques in the neocortex but without severe senile changes in the hippocampus].

Using modified Bielschowsky method, we studied neuropathologically 159 aged subjects autopsied during the period from 1976 to 1988, of which we found 19 cases (average age at death: 82.6 ys) with numerous diffuse plaques in the frontal and temporal neocortex and no severe senile changes in H1-H3 of Ammon's horn (dp group). Amyloid angiopathy had been excluded and one case was excluded because of considerable cerebrovascular lesions. The dp group was divided into 8 demented (average age at death: 86.0 ys) and 10 nondemented patients (average age at death: 79.7 ys). We compared the number, type, and ratio of types of senile plaques in the frontal cortex, temporal cortex, and putamen of the demented and nondemented groups, and obtained the following results: (1) Eight (14%) of the 59 nondemented and 8 (40%) of the 20 demented cases in which no severe senile changes in the neocortex and hippocampus had been detected by Bodian stain showed numerous diffuse plaques in the neocortex when the modified Bielschowsky method was used. (2) The ratio of classic and primitive plaques to diffuse plaques in the frontal cortex was the same in both groups, but the nondemented group had exclusively diffuse plaques in the temporal cortex. (3) In the putamen 2 nondemented cases (20%) and 6 demented cases (75%) had exclusively diffuse plaques. We considered that classic and primitive plaques are more closely related to dementia than are diffuse plaques in the temporal lobe in cases without severe senile changes in the hippocampus.

Aged↗

PubMed1986

[Comparative analysis of the neocortex during the ontogenesis of cetaceae and primates].

Comparative ontogenetic investigation of cytoarchitectonics of the cerebral neocortex has been performed in Cetacea and Primates using paraffin frontal and sagittal cerebral sections stained after Nissl. Cerebral hemispheres of dolphins, whales, monkeys and human being have been studied at various periods of prenatal development and in mature individuals. The comparison has been made at similar stages of cytoarchitectonical differentiation of the cortical plate. At two first stages of the prenatal ontogenesis (formation of the cortical plate and its differentiation into layers) there is not any principle differences between the Cetacea and Primates. Peculiarities of the cerebral cortical plate differentiation in the Cetacea (absence of the internal granular layer IV) is determined at the stage of stratification. Similar agranular character of the cerebral cortex differentiation is maintained during the whole subsequent ontogenesis in the Cetacea (heterogenetic type of the neocortex after Brodman). Absence of the layer IV in the cerebral neocortex determines some other principles in the spatial organization of the cortical-subcortical and in the intracortical connections in the Cetacea brain. This is confirmed by modern data of morphological and electrophysiological investigations. Perhaps, a comparatively more simple initial architectonics of the Cetacea brain limited the level of their functional possibilities, the latter is comparable only with anthropoid apes.

Adaptation, Biological↗

PubMed1982

[Effect of electric stimulation of the hippocampus and neocortex on limbic cortex neurons in the rabbit].

Extracellular recording of neuronal activity in anterior and posterior cingulate cortex was performed in unanaesthetized rabbits during electrical stimulation of the hippocampus and associative areas of anterior and posterior neocortex. Stimulation of the hippocampus was significantly more effective for posterior cingulate neurons (60% of reactive units) than for the anterior ones (18%). Most of reactive neurons in posterior cingulate cortex responded by time-locked effects; in anterior cingulate cortex such responses were rare. The latencies of the posterior cingular neuronal responses constituted two separate groups with the mean values 12.3 +/- 6.5 ms and 50.2 +/- 10.0 ms. Various forms of the activity suppression were also observed during hippocampal stimulation. Stimulation of posterior neocortex was almost equally effective for both areas of cingulate cortex: in more than a third of the units tested it evoked initial discharge followed by suppression of activity. Stimulation of anterior neocortex evoked such responses only in a limited proportion of anterior cingulate cortex neurons. The facts are discussed in the light of recent morphological data on connections between the investigated structures.

Animals↗

PubMed1982

[Asymmetrical distribution of noradrenaline in the neocortex, hippocampus and adrenal glands of rats and changes with chronic activity restriction].

The norepinephrine content of neocortex, hippocampus, and adrenals of adult male Wistar rats was estimated. In normal rats an asymmetrical right-left-distribution of the norepinephrine content was found. Neocortex and hippocampus showed a contralateral, neocortex and adrenals an ipsilateral ratio. Chronic stress cancelled this right-left asymmetry of norepinephrine distribution. In brain the levelling appeared earlier than in adrenals.

Adrenal Glands↗

PubMed1982

Comparison of brain structure volumes in Insectivora and Primates. I. Neocortex.

Based on volume measurements the total neocortex increases enormously from the lower ('basal') Insectivora, through prosimians, monkeys and apes up to man. In man it is about 132 times larger than in the average basal Insectivora of (theoretical) equal body weight and 232 times larger than in the insectivoran species which has the least developed neocortex. Within the neocortex the white matter increases more markedly than the grey matter. For man the white matter reaches a value 298 times that of the basal Insectivora and the grey matter reaches a value 198 times greater. Within the grey matter the cell dense layers (laminae 2-6) increase distinctly more than the molecular layer (lamina 1). Thus in man the volume of layers 2-6 is 272 times greater than that in basal Insectivora and the molecular layer is 68 times greater. When related to the total grey matter the percentage of the molecular layer clearly decreases from about 32% in the lower Insectivora to 12% in higher primates.

Animals↗

PubMedDate not supplied

[Functional differentiation of different portions of the the rat neocortex].

The effect of uni- and bilateral ablation of rostral and caudal parts of neocortex on conditioned avoidance reflex was studied on naive and pretrained albino rats. Maximal impairment of the reflex was seen after bilateral ablation of the caudal region of neocortex, minimal one--after unilateral neocortex ablation. The rats without rostral cortex showed medium impairment. After extirpation of caudal cortex the number of positive reactions to light was greater in pretrained rats than in naive ones. After total cortical extirpation the previously elaborated conditioned reflex disappeared irreversibly. The conclusion is made on functional heterogeneity of the rostral and caudal cortex.

Animals↗

PubMed1981

Effects of 3-sulfamoylmethyl-1,2-benzisoxazole (AD-810) and some antiepileptics on the kindled seizures in the neocortex, hippocampus and amygdala in rats.

Effect of 3-sulfamoylmethyl-1,2-benzisoxazole (AD-810) on kindled seizures in the neocortex, hippocampus and amygdala was studied in comparison with that of clinically proved antiepileptics, and the differences in kindled seizure development in the three areas were also studied. The amygdala more rapidly developed a generalized seizure (kindled seizure) than the hippocampus and the neocortex. Although more days of stimulation were needed, the neocortex also developed a kindled seizure similar to limbic kindled seizures. Phenobarbital, carbamazepine, dipropylacetate and diazepam showed a depressant effect on the neocortical kindled seizures. Phenytoin showed a depressant effect only when it was administered intravenously. Phenobarbital and carbamazepine depressed the hippocampal kindled seizures, while phenytoin and diazepam had little effect. Phenobarbital and diazepam caused marked depression on the amygdaloid kindled seizures, but the effect of phenytoin, carbamazepine and dipropylacetate on them was weak or negligible. AD-810 showed a depressant effect on neocortical and hippocampal kindled seizures, but not on amygdaloid ones. The profile of AD-810 is similar to that seen with carbamazepine.

Amygdala↗

PubMed1994

Newly formed host cells in a grafted juvenile neocortex express neurone-specific marker proteins.

Recently we reported that a mouse foetal neural graft, when transferred into a lesioned juvenile neocortex, may induce cortical repair and stimulate proliferation of the host cells. The present study was focused on an immunohistochemical identification of neurones among these newly generated cells. Adjacent sections from the brains already used in our previous study were stained either with an antibody against the host-specific Thy-1 antigen, or with neurone-specific antibodies recognizing the microtubule-associated protein MAP2, the heavy subunit of neurofilaments and parvalbumin. Dividing cells, labelled repeatedly during the first three post-operative days with 3H-thymidine, were detected after 2 months by autoradiography. We found that in the repaired neocortical region newly formed host cells, whose distribution resembled the one found in an intact neocortex, also contained neurones. These new data corroborate our previous suggestion that a juvenile mammalian neocortex participates, after lesioning and under the presence of a foetal neural graft, in its own repair by the formation of new cells, including neurones.

Animals↗

PubMed1996

Differential survival of Cajal-Retzius cells in organotypic cultures of hippocampus and neocortex.

Cajal-Retzius (CR) cells are transient, pioneer neurons of layer I of the cortex that are believed to play essential roles in corticogenesis, e.g., in neuronal migration and synaptogenesis. Here we have used calretinin immunostaining to study the characteristics, survival, and fate of CR cells in single organotypic slice cultures of mouse neocortex and hippocampus deprived of their extrinsic afferents. In neocortical explants, CR cells were observed after 1-3 d in vitro (DIV), but they disappeared after 5-7 DIV, which is similar to their time of degeneration in vivo. The disappearance of CR cells in neocortical slices was prevented by incubation with tetrodotoxin and the glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3,-dione but not by 2-amino-5-phosphonopentanoic acid, suggesting that neuronal activity and non-NMDA glutamate receptors may trigger CR cell death in the neocortex. In contrast to the situation in vivo, in which many hippocampal CR cells disappear at approximately the third postnatal week, CR cells survived in single hippocampal cultures after long incubation times (31 DIV), with their morphology essentially unaltered. In contrast, fewer CR cells were found when hippocampal slices were cocultured with explants from the entorhinal cortex. Because CR cells are transient synaptic targets for entorhinohippocampal afferents, these findings suggest a role for entorhinal afferents in the degeneration of CR cells in the hippocampus. In conclusion, this study shows different survival properties of CR cells in organotypic slice cultures of hippocampus and neocortex, and it suggests that different mechanisms are involved in the regulation of the process of naturally occurring CR cell death in the two cortical regions.

Afferent Pathways↗