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Topic: Isocortex


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  Isocortex - the free encyclopedia   (Site not responding. Last check: 2007-10-31)
Isocortex is the part of the cerebral cortex with a sixlayer laminar structure.
This is in contrast to the allocortex that has a variable number of layers.
Granular cortex(koniocortex or "dustlike cortex"), part of the isocortex with many granular cells, e.g., found in the sensory areas.
www.encyclopedia-of-knowledge.com /default.asp?t=Isocortex   (46 words)

  
 Localized Proton MR Spectroscopy of the Allocortex and Isocortex in Healthy Children -- Choi et al. 21 (7): 1354 -- ...
of the temporal lobe and isocortex of the parietal or frontal
in the isocortex of the parietal or frontal lobe: 1.05 ±
with the isocortex, the allocortex is characterized by a relatively
www.ajnr.org /cgi/content/full/21/7/1354   (2437 words)

  
 aboitizetal
The isocortex may have originated partly as a consequence of an overall dorsalizing effect (that is, an expansion of the territories expressing dorsal-specific genes) during pallial development.
Mammals are characterized by the possession of the isocortex (Fig.
Comparing the adult isocortex with the reptilian cortex, Ebner (1969) and Reiner (1991; 1993) proposed that the reptilian cortex mostly corresponds to the deep isocortical layers VI and V of the mammalian cortical plate.
www.bbsonline.org /Preprints/Aboitiz/Referees   (18016 words)

  
 Cerebral cortex   (Site not responding. Last check: 2007-10-31)
The grooves between the Gyri (known sulci) on the brain's surface results in of the cortex being buried; over 60% the cerebral cortex in primates is buried not visible from the surface.
Isocortex (homotypical cortex) the part of the with six layers.
Mesocortex classification between isocortex and allocortex layers 2 3 and 4 are merged.
www.freeglossary.com /Cerebral_cortex   (329 words)

  
 Evolution of the Amniote Brain
The six layered isocortex in mammals may not be as different from the DVR of diapsid reptiles and birds as it appears.
Both isocortex and ADVR have the cell groups of their sensory circuits (i.e., cortical layers or ADVR nuclei) organized perpendicular to the lateral ventricle.
One interpretation of the aforementioned trends is that the forebrain expansion in the ancestors of modern reptiles (and eventually birds) reflects the evolution of the DVR, while the evolution of the forebrain in mammals reflects the expansion of the basal ganglia and the uniquely mammalian isocortex (Ulinski, 1983).
www.pigeon.psy.tufts.edu /avc/husband/avc2amnt.htm   (3508 words)

  
 Cogprints - The evolutionary origin of the mammalian isocortex: insights from molecular developmental biology   (Site not responding. Last check: 2007-10-31)
The isocortex is a distinctive feature of the mammalian brain, which has no clear counterpart in the cerebral hemispheres of other amniotes.
Furthermore, recent evidence on the expression patterns of regulatory genes strongly suggests that a large part of the dorsal ventricular ridge arises from a region denominated the intermediate territory or ventral pallium, which in mammals gives rise to parts of the amygdalar complex among other structures.
Additionally, we suggest a scenario for the origin of the isocortex as an expansion of the reptilian dorsal cortex, which is consistent with current evidence.
www.cogprints.org /132   (294 words)

  
 Brazilian Journal of Medical and Biological Research - Critical steps in the early evolution of the isocortex: Insights ...   (Site not responding. Last check: 2007-10-31)
Furthermore, a characteristic of the isocortex is that it develops according to an inside-out neurogenetic gradient, in which late-produced cells migrate past layers of early-produced cells.
The first question is related to the topographic position of the isocortex (and its ancestral structure) in the brain of early reptiles or mammal-like reptiles, while the second question is related to the evolution of the internal structure of the isocortex.
The second main point of this paper is that the superficial isocortical laminae are evolutionarily new components of the isocortex, and their origin, together with the tangential expansion of the early isocortex, triggered the development of the inverted neurogenetic gradient of mammals and the radial entrance of thalamocortical axons, respectively.
www.scielo.br /scielo.php?script=sci_arttext&pid=S0100-879X2002001200006&lng=en&nrm=iso   (8982 words)

  
 Neocortex - Wikipedia, the free encyclopedia
It is involved in higher functions such as sensory perception, generation of motor commands, spatial reasoning, conscious thought, and in humans, language.
Other names for the neocortex include neopallium ("new mantle") and isocortex ("equal rind").
The neocortex consists of grey matter surrounding the deeper white matter of the cerebrum.
en.wikipedia.org /wiki/Isocortex   (524 words)

  
 The cerebral hemispheres of the vertebrate brain probably originated in conjunction with the olfactory bulb, and in the ...   (Site not responding. Last check: 2007-10-31)
One perspective, based on similarities in the telencephalic sensory projections between birds/reptiles and mammals, asserts that the isocortex partly arose from a structure denominated dorsal ventricular ridge, that is present in the avian/reptilian brain.
In amphibians, the auditory and tectal visual pathways terminate in the corpus striatum, which is clearly not homologue of either the isocortex or the DVR (Butler 1994).
Although an explanation for the evolutionary development of the reptilian DVR is still needed, we suggest that the mammalian isocortex originated in the dorsal pallium by virtue of the relations of the dorsal cortex with the medial/dorsomedial cortex (hippocampus) and the olfactory cortex (Fig.
cogprints.ecs.soton.ac.uk /archive/00000132/00/BBS12.html   (5804 words)

  
 Isocortex is the part of the cerebral cortex cerebral cortex...   (Site not responding. Last check: 2007-10-31)
Isocortex is the part of the cerebral cortex cerebral cortex...
"Isocortex" is the part of the cerebral cortex cerebral cortex with a six layer laminar structure.
Granular cortex Granular cortex (koniocortex or "dustlike cortex"), part of the isocortex with many granular cells granular cells, e.g., found in the sensory areas.
www.biodatabase.de /Isocortex   (117 words)

  
 CVA19S00   (Site not responding. Last check: 2007-10-31)
Isocortex: 6 layers; allocortex (from medial and lateral pallium) is 3 layered.
The DVR is derived from a different part of the telencephalon during development [the lateral pallium], so it is not homologous to the isocortex [derived from the dorsal pallium].
In lower vertebrates, the main centres dominating nervous activity are in the anterior regions of the brain stem.
webpages.marshall.edu /~hurlburt/310lec19.html   (1481 words)

  
 The Symphonic Architecture of Mind
It is informed by isocortex, thalamus, and the hippocampal region, and causes effects by focally disinhibiting the thalamus (whence the signal returns to cortex).
During sleep, hippocampal memories revive while isocortex is in a state of heightened plasticity, causing their consolidation in isocortex as long term memories.
The consolidation process is the selective construction of these handles in isocortex at successively greater geometric and topological distance from the hippocampi and dentate gyri proper, until finally the interconnections between the memory components are so established that no distinguished handle is needed.
www.mega.nu:8080 /wavetrain.html   (18705 words)

  
 Reptile Brain Research -- Neurotransmitter.net
Although it seems highly likely that mammalian isocortex evolved from a structure resembling reptilian telencephalic cortex, it has been uncertain if this occurred by the laminar differentiation of three-layered reptilian cortex into six-layered mammalian isocortex without the addition of new cell types or by laminar differentiation with the addition of new cell types.
Numerous scientists have sought a homologue of mammalian isocortex in sauropsids (reptiles and birds) and a homologue of sauropsid dorsal ventricular ridge in mammals.
In any case, the isocortex may have originated partly as a consequence of an overall "dorsalizing" effect (that is, an expansion of the territories expressing dorsal-specific genes) during pallial development.
www.neurotransmitter.net /reptilebrain.html   (11614 words)

  
 The cerebral hemispheres of the vertebrate brain probably originated in conjunction with the olfactory bulb, and in the ...   (Site not responding. Last check: 2007-10-31)
The isocortex receives ascending sensory input from the thalamus and projects to the hippocampus and to the amygdala, as well as sending output to several lower brain centers including the thalamus, corpus striatum, several brainstem nuclei and the spinal cord.
Second, the mammalian isocortex projects reciprocally to the entorhinal cortex and from there to the hippocampus (Van Hoesen 1982; Rosene and Van Hoesen 1987; Insausti 1993), while in reptiles few if any connections have been reported from the DVR to the hippocampus (Ulinski 1983; Ten Donkelaar 1998; Ulinski 1990).
In reptiles and birds, although a circuit exists associating the olfactory, the dorsal (visual thalamofugal) and the medial/dorsomedial (hippocampal) cortices, the more important projections from somatosensory, auditory and visual tectal systems end in the ADVR, which is in turn connected primarily to the PDVR (comparable to parts of the mammalian amygdalar complex).
www.cogprints.org /archive/00000132/00/BBS12.html   (5804 words)

  
 Developmental structure in brain evolution
The idea that enlarged isocortex could be a"spandrel," a byproduct of structural constraints later adapted for various behavior, contrasts with approaches that look to selection of particular brain regions for cognitively advanced behaviors, as commonly assumed in the case of hominid brain evolution.
As all the vaunted capabilities of modern brains are fairly recent developments, their location in isocortex is a straightforward consequence of the fact that that area is the latest brain structure to undergo terminal neurogenesis, and therefore in the best position to provide the additional processing capacity for those functions.
The exponential growth of isocortex relative to the rest of the brain is due to its prosomeric location, not to accelerating technological demands "remaking" the brain.
www.bbsonline.org /Preprints/OldArchive/bbs.finlay.html   (15317 words)

  
 [No title]   (Site not responding. Last check: 2007-10-31)
Evaluate the tangential distribution of NADPH diaphorase (NADPH-d)/nitric oxide synthase (NOS) neurons in the isocortex of two medium-sized Amazonian rodents with distinct circadian habits: agouti (diurnal) and paca (nocturnal).
The sections were then reconstructed using the morphometric software Neurolucida, and the relative location of NADPH-d type I neurons were assigned in order to perform comparisons of their distribution across anterior, posterior, lateral and medial regions of the isocortex.
In both the agouti and the paca’s isocortex it was possible to identify two subtypes of NADPH-d neurons, type I (large cell bodies and heavily stained) and type II (small cell bodies and weakly stained).
www.fesbe.org.br /fesbenovo/ver-resumo/ver.php?evn=1&rsm=269&setor=2&nome=Neuromorfologia   (303 words)

  
 wikien.info: Main_Page   (Site not responding. Last check: 2007-10-31)
Then, some progenitor cells begin to divide asymmetrically, producing one postmitotic cell that migrates and leaves the ventricular zone, and a daughter cell that continues to divide or that eventually dies.
After migration, neurons form efferents and receive afferent connections characteristic of their layer.
Neocortex or Neopallium that corresponds to the isocortex.
www.pardus.info /index.php?title=Cerebral_cortex   (1247 words)

  
 [No title]   (Site not responding. Last check: 2007-10-31)
동형피질(isocortex)의 층판은 6층으로 구성되어 있지만 모든 부위에서 동일한 것은 아니며, 부분에 따라 층판의 두께와 구성에 차이가 있다.
일반적으로 6층의 층판을 잘 구분할 수 있는 피질부위는 동형전형 동형피질(homotypical isocortex)이라고 하며, 연합피질(association cortex)을 포함하는 대부분의 대뇌피질이 여기에 속한다(그림 11-5, 11-6).
제5형(type 5)은 과립형 피질(granular cortex)로 피질의 두께가 가장 얇으며 이형전형 동형피질(heterotypical isocortex)의 과립피질(granular cortex)이 여기에 속한다.
128.134.207.22 /scripts/home/book_view.idc?name=CH11-PT1-TB0-TT0-ST6   (282 words)

  
 SICB - 2006 meeting - Abstract Details   (Site not responding. Last check: 2007-10-31)
In many large brained mammals, sensory regions of isocortex are separated from one another by intervening regions of association cortex.
The extensive relative increase in the amount of isocortex in the dolphin brain occurs outside this grouping of sensory and motor regions, in a peripheral arc of extensive frontal, lateral, and posterior cortical regions.
This contrasts with the pattern which evolved in expanded cortex of highly encephalized primate brains, and also in brains of advanced carnivores, where additional cortex was inserted between the main sensory and motor regions.
www.sicb.org /meetings/2006/schedule/abstractdetails.php3?id=643   (185 words)

  
 NeuroNames Source: Stephan-76   (Site not responding. Last check: 2007-10-31)
Five fundamental types of cortex are distinguished: Allocortex bulbi olfactorii, Allocortex primitivus, Periallocortex, Proisocortex, and Isocortex maturus the first three of which are collected in the allocortex of broader sense, the two latter in isocortex of broader sense.
In the Periallocortex all transitional cortices between Allocortex primitivus and Isocortex are included, as far as they are directly adjacent to the Allocortex primitivus.
The transitional cortex adjacent to the praepiriform cortex is called Peripalaeocortex and corresponds to the Regio peripalaeocorticalis claustralis (mesocortical insula), the cortex adjacent to the Hippocampus [is] called Periarchicortex and includes four regions: Regio entorhinalis, praesubicularis, retrosplenialis and cingularis periarchicorticalis, all of which can be subdivided into areas.
braininfo.rprc.washington.edu /aboutfolder/sources/stephan-76.html   (253 words)

  
 Neuronal Classes in the Isocortex of a Monotreme, the Australian Echidna (Tachyglossus aculeatus) - Karger ...
All except the pyramidal neurons were morphologically similar to neuronal classes seen in eutherian and metatherian isocortex.
Many pyramidal neurons in the echidna isocortex were atypical (30-42% depending on region) with inverted somata, short or branching apical dendrites and/or few basal dendrites, very different from the usual pyramidal neuron morphology in eutherian cortex.
Dendritic spine density on apical and basal dendrites of echidna pyramidal neurons in somatosensory cortex and apical dendrites of motor cortex pyramidal neurons was also lower than that found in the rat.
content.karger.com /ProdukteDB/produkte.asp?Aktion=ShowFulltext&ProduktNr=223831&Ausgabe=228982&ArtikelNr=68877   (269 words)

  
 HUMAN PHYSIOLOGY I
In either case, the depolarization causes the opening of voltage gated calcium channels leading to the release of neurotransmitter.
Starting with the taste buds on the anterior 2/3rds of the tongue, describe the pathway by which gustatory sensation reaches the isocortex.
Starting with the cells of the olfactory bulb, describe the pathway by which olfactory sensation reaches the isocortex.
nas.cl.uh.edu /puzdrowski/Neuroscience/Exam22K4key.htm   (2024 words)

  
 Evolutionary Developmental Biology of the Cerebral Cortex - No. 228 (CIBA Foundation Symposia Series) by Novartis ...
Recent data on the earliest generated transient cells in the mammalian, reptilian, avian and amphibian forebrain are discussed, as are possible homologies based on specific connectional analysis.
The various hypotheses on the origin of the mammalian isocortex are discussed in detail and new results are presented on cortical organization in reptiles, birds, marsupials, monotremes and other species.
This short book (271, not 500+ pages as stated by Amazon)consists of brief review articles by leading researchers, followed by an edited Q&A/discussion section that followed the presentations at a symposium held in 4/99.
www.gettextbooks.com /isbn_0471979783.html   (525 words)

  
 Heterogeneous expression of the polysialyltransferases ST8Sia II and ST8Sia IV during postnatal rat brain development.   (Site not responding. Last check: 2007-10-31)
In the mature brain, ST8Sia IV is the predominant polysialyltransferase.
ST8Sia II was not detectable at any time point in the subependymal layer and the layers of the olfactory bulb.
Persistent ST8Sia IV expression was localized in the subependymal layer, the glomerular layer of the olfactory bulb, and the granule cell layer of the dentate gyrus and in some widely dispersed cells of the isocortex.
www.uni-hohenheim.de /i3ve/00068900/18013041.htm   (334 words)

  
 Nobel Symposium 103-Abstracts
In the isocortex, the basic circuit, scaled to specific requirements, is repeated in each layer.
Tangential intralaminar connections in both the hippocampus and isocortex also connect output neurones with similar properties, as best seen in the patchy connections in the isocortex.
The additional radial superposition of several laminae of distinct sets of output neurones, each representing and suported by its basic circuit, requires a co-ordination of their activity that is mediated by highly selective interlaminar connections, involving both the GABAergic and the excitatory amino acid releasing neurones.
nobelprize.org /medicine/symposia/ns103/somogyi.html   (559 words)

  
 Abstract: Alan Turing draws a firm line between the mental and the physical, between the cognitive and physical sciences
This conserved order of neurogenesis predicts the relative scaling not only of gross brain regions like the isocortex or mesencephalon, but also the level of detail of individual thalamic nuclei.
Special selection of particular areas for specific functions does occur, but it is a minor factor compared to the large‑scale covariance of the whole brain.
The idea that enlarged isocortex could be a "spandrel," a by product of structural constraints later adapted for various behavior, contrasts with approaches that look to selection of particular brain regions for cognitively advanced behaviors, as commonly assumed in the case of hominid brain evolution.
www.hfac.uh.edu /phil/leiber/ValeriePaper.htm   (3774 words)

  
 Cortical column
From outside inward: Molecular layer External granular layer External pyramidal layer Internal granular layer Internal pyramidal layer Multiform layer After migration (interestingly, the inner layers are formed first during development), neurons form efferents and receive afferent connections characteristic of its layer.
Based on the differences in lamination the cerebral cortex can be classified into two major groups: Isocortex (homotypical cortex), the part of the cortex with six layers.
Auxiliary classes are: Mesocortex, classification between isocortex and allocortex where layers 2, 3 and 4 are merged.
www.experiencefestival.com /cortical_column   (546 words)

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