Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Neocortex”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,423 records · Page 79Linked to original sources
PubMed1997

[The developmental characteristics of the embryonic anlagen of rat neocortex and spinal cord when transplanted into the distal end of the dissected sciatic nerve of adult animals].

The spinal cord and cerebral cortex of 14 day old embryos of Wistar rats were transplanted into the distal stump of the adult rat cut sciatic nerve in order to study dynamics of the development of the transplanted cell elements, and to elucidate relations of neuronal elements in the central and peripheral nervous systems. By means of light and electron microscopy it has been stated that the transplanted nerve cells of the cortex and spinal cord could survive for 60 days and differentiate from neuroepithelial cells and neuroblasts up to young and mature neurons. In the transplants a neuropil is seen to form with both unmyelinated and myelinated axons and synaptic contacts. In the cortex transplants cavities appear paved with ependyma-like cells having cilia and microvilli. It has been found that axons of the transplanted spinal cord neurons may leave transplants to be myelinated by the recipient's Schwann cells of the peripheral nerve.

Animals↗
PubMed1998

Basic FGF increases communication between cells of the developing neocortex.

We have found that basic fibroblast growth factor (bFGF), applied to cortical progenitor cells in vitro, produces an increase in the expression of the gap junction protein connexin (Cx) 43 and in the mRNA encoding Cx 43. This effect was evident in both proliferating and nonproliferating cells. The elevated levels of mRNA suggest that bFGF is likely to exert its effect by upregulating the rate of transcription of the Cx 43 gene. We have further shown that the increase in Cx 43 expression is mediated through the receptor tyrosine kinase pathway and is associated with enhanced intercellular dye-coupling mediated by gap junctions. These results suggest that gap junction channels provide a direct conduit for mitogens released in response to bFGF to effectively regulate proliferation during corticogenesis.

Animals↗
PubMedDate not supplied

[The tangential segregation of simple and complex cells in the visual cortex and their connections. The universal neocortex modulus].

Guinea-pig studies testify that in rodents (like in higher mammals) the primary afferents from the thalamus and inferior cortical afferents converge on discrete columns about 200 mcm in size with zones of secondary convergence between them. The cortical columns seem to be primary basic and universal cortical modules, since they have similar dimensions and uniform organization in different mammals. The columns concentrate simple cells (with complex ones among them) and afferent inhibitory neurons; these models are involved in the first stage of cortical integration. Local connections of the primary modules differ from those of the secondary intermediary zones, which are poor narrow in rodents. The intermediary zones progressively develop in phylogeny, and in higher mammals they excel the primary modules in dimensions.

Afferent Pathways↗
PubMedDate not supplied

[The effect of atropine on the ultrastructural postsynaptic plasticity of the associative type in the rat neocortex].

The effect of muscarinic antagonist atropine on thickness of postsynaptic density of axodendritic synapses was studied in the sensorimotor region of the brain cortex of rats during paired repeated microapplication of glutamate and acetylcholine. In the applied conditioning paradigm atropine significantly decreased morphological dimensions of the postsynaptic density, however, the control values were not reached. This finding testifies to participation of both muscarinic and nicotinic cholinoreceptors in associative postsynaptic plasticity.

Acetylcholine↗
PubMed1999

Epileptiform discharges in the human dysplastic neocortex: in vitro physiology and pharmacology.

Field potential and intracellular recordings were made in slices of human neocortical tissue obtained during surgery for the treatment of seizures associated with focal cortical dysplasia. Ictal-like epileptiform discharges, along with isolated field potentials, were induced by bath application of 4-aminopyridine (50-100 microM). Some of the isolated field potentials were associated with fast transients representing population spikes. Field potential profile analysis indicated that both types of synchronous activity had maximal negative values at 1,400 to 1,600 microm from the pia. The intracellular counterpart of the ictal-like discharge was a prolonged membrane depolarization capped by repetitive action potential burst firing. By contrast, the isolated field potentials were mirrored by long-lasting depolarizations with minimal action potential firing; only when population spikes occurred, the isolated field potentials were associated with epileptiform action potential bursting. Ictal-like discharges were abolished by either N-methyl-D-aspartate or non-N-methyl-D-aspartate receptor antagonists. In contrast, the isolated field potentials continued to occur synchronously during excitatory transmission blockade (although they lacked fast transients) but were abolished by the gamma-aminobutyric acid(A) receptor antagonist bicuculline methiodide (n = 2 slices). Our study demonstrates that focal cortical dysplasia tissue maintained in vitro has an intrinsic ability to generate ictal-like epileptiform events when challenged with 4-aminopyridine. These discharges depend on excitatory amino acid receptor-mediated mechanisms. Our results also show the presence in focal cortical dysplasia tissue of glutamatergic-independent synchronous potentials that are mainly contributed by gamma-aminobutyric acid(A) receptor-mediated conductances.

4-Aminopyridine↗
PubMed1975

Intercellular relationships in the external glial limiting membrane of the neocortex of the cat and rat.

The external glial limiting membrane of the cerebral cortex appears to be a complete astrocytic mantle covering the pial surface of the molecular layer. It consists of flattened cell bodies arranged singly or in small groups spaced about 100 mu apart and multitudes of interdigitating processes arrayed in layers. The glial mantle is thicker in the sulci than on the gyri. It is covered externally by a basal lamina which is associated with collagenous fibrils and cells of the pia mater. The extracellular space in aldehyde-perfused material appears as a regular, electron-lucent interval 150 A wide between adjacent cell membranes. Gap junctions are frequently encountered in the external glial limiting membrane; desmosomes are present between astrocytic processes but are seen much less often.

Animals↗
PubMed1975

The number, size and spatial distribution of neurons in lamina IV of the mouse SmI neocortex.

We located the corresponding barrel in Layer IV of the mouse SmI cortex in eleven cerebral hemispheres sectioned in a plane tangential to the pia overlying SmI and in one sectioned and prepared by a combined Golgi-Nissl method. In the section in which barrel C-1 could be optimally visualized each neuronal soma was outlined with a camera lucida and the cross-sectional area measured with the aid of a small computer. In all, nearly 7,000 neurons were measured. We estimate that on average barrel C-1 contains about 2,000 neurons. The mean cross-sectional area of the perikarya is 62.51 mu2 (S.D. plus or minus 14.51 mu2) and the size distribution of the neurons is unimodal and positively skewed. There is no segregation of cells within the barrel on the basis of size. The spatial distribution of cells in the barrel is fairly constant, from specimen to specimen, and the charactieristic cytoarchitectonic appearance of the barrel can be related to regional neuronal packing density since there are at least 1.6 as many neurons in the sides of the barrel as the hollow. The constancy of the cellular composition of the barrels indicates that the mechanisms responsible for the development of the mouse SmI cortex are fairly rigidly determined, and that the barrel field should lend itself well to further quantitative, developmental and physiological analysis.

Animals↗
PubMed1977

The second somatic sensory area (SmII) of opossum neocortex.

Organization of the neocortical second somatic sensory area (SmII) of anesthetized Virginia opossums has been examined utilizing micro-electrode recording techniques. SmII is situated between the first somatic sensory area (SmI) medially, and the rhinal fissure laterally. The head representation is located anteromedially within SmII, and the hindlimb representation posterolaterally, with the forelimb representation in between. Approximately 49% of SmII is devoted to representation of the head, 36% to forelimb representation, and 15% to trunk and hindlimb representation. All peripheral receptive fields (RF's) were either contralateral or bilateral. Approximately 63% of head RF's, 25% of forelimb RF's and 100% of hindlimb RF's were bilateral. For a given body locus, SmII RF's are larger than those for SmI. SmII is contained entirely within an area yielding evoked potentials responses to auditory click stimuli.

Animals↗
PubMed1978

Converging projections from the mediodorsal thalamic nucleus and mesencephalic dopaminergic neurons to the neocortex in three species.

Previous studies in the rat have shown that the neocortical dopaminergic afferents, originating in the mesencephalon, terminate in those areas of the frontal lobe which receive projections from the mediodorsal thalamic nucleus i.e., the prefrontal cortex. In order to clarify whether this overlap is accidental for the rat or a consistent feature of several species we have compared the projection areas of the ventral tegmental area and the mediodorsal thalamic nucleus in three species, rat, opossum and tree shrew, using HRP injections in combination with glyoxylic acid histofluorescence method. The results have shown, first, that the area innervated by the mediodorsal nucleus of the thalamus is localized in a different part of the frontal lobe in each species: dorsolateral in the opossum, anteromedial, polar and suprarhinal in the rat and frontopolar in the tree shrew. Secondly, this area alone in each species receives projections from the ventral tegmental area. Thirdly, this area alone receives a dense innervation in the deep cortical layers by fluorescent fibres probably containing dopamine. The neighbouring neocortical areas receive afferents neither from the mediodorsal nucleus of the thalamus nor from the ventral mesencephalic tegmentum; their catecholamine innervation is mainly confined to the superficial layers and appears to be of noradrenergic nature. Although the techniques used did not allow a precise determination of the borders of the two projection areas and, therefore, the exact degree of overlap, it appears that mesencephalic dopaminergic innervation is a characteristic feature of the prefrontal cortex in the mammalian brain.

Animals↗