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Single Axon Branching Analysis in Rat Thalamocortical Projection from the Anteroventral Thalamus to the Granular Retrosplenial Cortex  [PDF]
Saori Odagiri,Yoshiya Asano,Noritaka Ichinohe
Frontiers in Neuroanatomy , 2011, DOI: 10.3389/fnana.2011.00063
Abstract: The granular retrosplenial cortex (GRS) in the rat has a distinct microcolumn-type structure. The apical tufts of dendritic bundles at layer I, which are formed by layer II neurons, co-localize with patches of thalamic terminations from anteroventral (AV) thalamic nucleus. To further understand this microcolumn-type structure in the GRS, one of remaining questions is whether this structure extends into other layers, such as layers III/IV. Other than layer I, previous tracer injection study showed that AV thalamic nucleus also projects to layer III/IV in the GRS. In this study, we examined the morphology of branches in the GRS from the AV thalamus in single axon branch resolution in order to determine whether AV axon branches in layer III/IV are branches of axons with extensive branch in layer I, and, if so, whether the extent of these arborizations in layer III/IV vertically matches with that in layer I. For this purpose, we used a small volume injection of biotinylated dextran-amine into the AV thalamus and reconstructing labeled single axon branches in the GRS. We found that the AV axons consisted of heterogeneous branching types. Type 1 had extensive arborization occurring only in layer Ia. Type 2 had additional branches in III/IV. Types 1 and 2 had extensive ramifications in layer Ia, with lateral extensions within the previously reported extensions of tufts from single dendritic bundles (i.e., 30–200 μm; mean 78 μm). In type 2 branches, axon arborizations in layer III/IV were just below to layer Ia ramifications, but much wider (148–533 μm: mean, 341 μm) than that in layer Ia axon branches and dendritic bundles, suggesting that layer-specific information transmission spacing existed even from the same single axons from the AV to the GRS. Thus, microcolumn-type structure in the upper layer of the GRS was not strictly continuous from layer I to layer IV. How each layer and its components interact each other in different spatial scale should be solved future.
Retrosplenial Cortex Codes for Permanent Landmarks  [PDF]
Stephen D. Auger, Sinéad L. Mullally, Eleanor A. Maguire
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0043620
Abstract: Landmarks are critical components of our internal representation of the environment, yet their specific properties are rarely studied, and little is known about how they are processed in the brain. Here we characterised a large set of landmarks along a range of features that included size, visual salience, navigational utility, and permanence. When human participants viewed images of these single landmarks during functional magnetic resonance imaging (fMRI), parahippocampal cortex (PHC) and retrosplenial cortex (RSC) were both engaged by landmark features, but in different ways. PHC responded to a range of landmark attributes, while RSC was engaged by only the most permanent landmarks. Furthermore, when participants were divided into good and poor navigators, the latter were significantly less reliable at identifying the most permanent landmarks, and had reduced responses in RSC and anterodorsal thalamus when viewing such landmarks. The RSC has been widely implicated in navigation but its precise role remains uncertain. Our findings suggest that a primary function of the RSC may be to process the most stable features in an environment, and this could be a prerequisite for successful navigation.
Laws of Conservation as Related to Brain Growth, Aging, and Evolution: Symmetry of the Minicolumn  [PDF]
Manuel F. Casanova
Frontiers in Neuroanatomy , 2011, DOI: 10.3389/fnana.2011.00066
Abstract: Development, aging, and evolution offer different time scales regarding possible anatomical transformations of the brain. This article expands on the perspective that the cerebral cortex exhibits a modular architecture with invariant properties in regards to these time scales. These properties arise from morphometric relations of the ontogenetic minicolumn as expressed in Noether’s first theorem, i.e., that for each continuous symmetry there is a conserved quantity. Whenever minicolumnar symmetry is disturbed by either developmental or aging processes the principle of least action limits the scope of morphometric alterations. Alternatively, local and global divergences from these laws apply to acquired processes when the system is no longer isolated from its environment. The underlying precepts to these physical laws can be expressed in terms of mathematical equations that are conservative of quantity. Invariant properties of the brain include the rotational symmetry of minicolumns, a scaling proportion or “even expansion” between pyramidal cells and core minicolumnar size, and the translation of neuronal elements from the main axis of the minicolumn. It is our belief that a significant portion of the architectural complexity of the cerebral cortex, its response to injury, and its evolutionary transformation, can all be captured by a small set of basic physical laws dictated by the symmetry of minicolumns. The putative preservations of parameters related to the symmetry of the minicolumn suggest that the development and final organization of the cortex follows a deterministic process.
The Retrosplenial Cortex: Intrinsic Connectivity and Connections with the (Para)Hippocampal Region in the Rat. An Interactive Connectome  [PDF]
J?rgen Sugar,Menno P. Witter,Niels M. van Strien,Natalie L. M. Cappaert
Frontiers in Neuroinformatics , 2011, DOI: 10.3389/fninf.2011.00007
Abstract: A connectome is an indispensable tool for brain researchers, since it quickly provides comprehensive knowledge of the brain’s anatomical connections. Such knowledge lies at the basis of understanding network functions. Our first comprehensive and interactive account of brain connections comprised the rat hippocampal–parahippocampal network. We have now added all anatomical connections with the retrosplenial cortex (RSC) as well as the intrinsic connections of this region, because of the interesting functional overlap between these brain regions. The RSC is involved in a variety of cognitive tasks including memory, navigation, and prospective thinking, yet the exact role of the RSC and the functional differences between its subdivisions remain elusive. The connectome presented here may help to define this role by providing an unprecedented interactive and searchable overview of all connections within and between the rat RSC, parahippocampal region and hippocampal formation.
Large interneurons of granular layer of cerebellar cortex  [PDF]
Stepanenko A.Yu.
Морфолог?я , 2009,
Abstract: Large interneurons of cerebellar cortex are described. Golgi Cells lie mostly in vestibulocerebellum. Their dendrites contact with parallel fibers and mossy fibers, axons terminate in glomerules. Golgi Cells inhibit granule cells and induce their synchronic rhythmic activity. Lugaro Cells lie in horizontal plane under ganglionic layer, form clasters and more frequent in paleocerebellum. Dendrites contact with collaterals Purkinje and basket cells axones; axones terminate on basket and stellate cell. Lugaro Cells stimulate Purkinje Cells by inhibiting of inhibitory stellate and basket cells. Candelabrum Cells are inhibitory interneurons which lie between Purkinje cells bodies. Axon forms horizontal branches in parasagittal plane in molecular layer, and vertical ones which resemble candelabrum. Unipolar brush cells – excitatory interneuron of the cerebel-lum, form system of intrinsic mossy fibers. Single axon forms numerous brush-like branches – dendrioles, which end in one common glomerules, axon collaterals terminate in another one. Synamortic neurons contact with neurons of cerebellar nuclei and another region of the cortex. Perivascular neurons regulate local blood flow.
Cerebellar Cortex Granular Layer Interneurons in the Macaque Monkey Are Functionally Driven by Mossy Fiber Pathways through Net Excitation or Inhibition  [PDF]
Jean Laurens, Shane A. Heiney, Gyutae Kim, Pablo M. Blazquez
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0082239
Abstract: The granular layer is the input layer of the cerebellar cortex. It receives information through mossy fibers, which contact local granular layer interneurons (GLIs) and granular layer output neurons (granule cells). GLIs provide one of the first signal processing stages in the cerebellar cortex by exciting or inhibiting granule cells. Despite the importance of this early processing stage for later cerebellar computations, the responses of GLIs and the functional connections of mossy fibers with GLIs in awake animals are poorly understood. Here, we recorded GLIs and mossy fibers in the macaque ventral-paraflocculus (VPFL) during oculomotor tasks, providing the first full inventory of GLI responses in the VPFL of awake primates. We found that while mossy fiber responses are characterized by a linear monotonic relationship between firing rate and eye position, GLIs show complex response profiles characterized by “eye position fields” and single or double directional tunings. For the majority of GLIs, prominent features of their responses can be explained by assuming that a single GLI receives inputs from mossy fibers with similar or opposite directional preferences, and that these mossy fiber inputs influence GLI discharge through net excitatory or inhibitory pathways. Importantly, GLIs receiving mossy fiber inputs through these putative excitatory and inhibitory pathways show different firing properties, suggesting that they indeed correspond to two distinct classes of interneurons. We propose a new interpretation of the information flow through the cerebellar cortex granular layer, in which mossy fiber input patterns drive the responses of GLIs not only through excitatory but also through net inhibitory pathways, and that excited and inhibited GLIs can be identified based on their responses and their intrinsic properties.
Increased Cell Fusion in Cerebral Cortex May Contribute to Poststroke Regeneration  [PDF]
Alexander Paltsyn,Svetlana Komissarova,Ivan Dubrovin,Aslan Kubatiev
Stroke Research and Treatment , 2013, DOI: 10.1155/2013/869327
Abstract: In this study, we used a model of a hemorrhagic stroke in a motor zone of the cortex in rats at the age of 3 months The report shows that cortical neurons can fuse with oligodendrocytes. In formed binuclear cells, the nucleus of an oligodendrocyte undergoes neuron specific reprogramming. It can be confirmed by changes in chromatin structure and in size of the second nucleus, by expression of specific neuronal markers and increasing total transcription rate. The nucleus of an oligodendrocyte likely transforms into a second neuronal nucleus. The number of binuclear neurons was validated with quantitative analysis. Fusion of neurons with oligodendrocytes might be a regenerative process in general and specifically following a stroke. The appearance of additional neuronal nuclei increases the functional outcome of the population of neurons. Participation of a certain number of binuclear cells in neuronal function might compensate for a functional deficit that arises from the death of a subset of neurons. After a stroke, the number of binuclear neurons increased in cortex around the lesion zone. In this case, the rate of recovery of stroke-damaged locomotor behavior also increased, which indicates the regenerative role of fusion. 1. Introduction Protection, rehabilitation, and stroke outcome are determined by the extent of the preserved neuronal tissue. Thus, the maintenance and regeneration of stroke-injured neurons is a prominent topic on which there are many publications, all of which represent neuronal regeneration exclusively as a result of neurogenesis. This tendency can be justified only in one case, when a stroke occurs in the dentate gyrus (fascia dentata hippocampus) or in the olfactory bulb. These two zones are reasonably considered neurogenic because they are sites of the replacement of granular neurons. Granular neurons are formed in two other neurogenic zones: the subgranular layer of the dentate gyrus [1–5] and the subventricular layer of the cerebral ventricles [6–8]. Neuroblasts migrate from these zones to the granular layer of the dentate gyrus [9–11] and to the olfactory bulbs [8, 12], where they differentiate into granular neurons. Reports of neurogenesis in other brain regions, as in the review of Gould [13], contradict other experiments [14–17]. Therefore, scientific consensus purports that, in other brain regions, neurogenesis does not occur. According to one hypothesis, neurogenesis does not normally occur in the cortex but appears after stroke [18, 19]. However, some publications do not confirm this point of view [20]. These issues
Pyramidal Cells in Prefrontal Cortex of Primates: Marked Differences in Neuronal Structure Among Species  [PDF]
Guy N. Elston,Paul R. Manger,Javier DeFelipe
Frontiers in Neuroanatomy , 2011, DOI: 10.3389/fnana.2011.00002
Abstract: The most ubiquitous neuron in the cerebral cortex, the pyramidal cell, is characterized by markedly different dendritic structure among different cortical areas. The complex pyramidal cell phenotype in granular prefrontal cortex (gPFC) of higher primates endows specific biophysical properties and patterns of connectivity, which differ from those in other cortical regions. However, within the gPFC, data have been sampled from only a select few cortical areas. The gPFC of species such as human and macaque monkey includes more than 10 cortical areas. It remains unknown as to what degree pyramidal cell structure may vary among these cortical areas. Here we undertook a survey of pyramidal cells in the dorsolateral, medial, and orbital gPFC of cercopithecid primates. We found marked heterogeneity in pyramidal cell structure within and between these regions. Moreover, trends for gradients in neuronal complexity varied among species. As the structure of neurons determines their computational abilities, memory storage capacity and connectivity, we propose that these specializations in the pyramidal cell phenotype are an important determinant of species-specific executive cortical functions in primates.
Dwinna Rahmi
Makara Seri Sains , 2010,
Abstract: Chelating resin-packed minicolumn preconcentration was used for multielement determination of trace metals inseawater by inductively coupled plasma mass spectrometry (ICP-MS). The chelating resin-packed minicolumn wasconstructed with two syringe filters (DISMIC 13HP and Millex-LH) and an iminodiacetate chelating resin (Chelex 100,200-400 mesh), with which trace metals in 50 mL of original seawater sample were concentrated into 0.50 mL of 2 Mnitric acid, and then 100-fold preconcentration of trace metals was achieved. Then, 0.50 mL analysis solution wassubjected to the multielement determination by ICP-MS equipped with a MicroMist nebulizer for micro-samplingintroduction. The preconcentration and elution parameters such as the sample-loading flow rate, the amount of 1 Mammonium acetate for elimination of matrix elements and the amount of 2 M nitric acid for eluting trace metals wasoptimized to obtain good recoveries and analytical detection limits for trace metals. The analytical results for V, Mn, Co,Ni, Cu, Zn, Mo, Cd, Pb, and U in three kinds of seawater certified reference materials (CRMs; CASS-3, NASS-4, andNASS-5) agreed well with their certified values. The observed values of rare earth elements (REEs) in the aboveseawater CRMs were also consistent with the reference values. Therefore, the compiled reference values for theconcentrations of REEs in CASS-3, NASS-4, and NASS-5 were proposed based on the observed values and referencedata for REEs in these CRMs
Screening for genes that wire the cerebral cortex
Ludmilla Lokmane, Sonia Garel
BMC Biology , 2011, DOI: 10.1186/1741-7007-9-1
Abstract: See research article: http://www.neuraldevelopment.com/content/6/1/3/abstract webciteUnderstanding how the brain becomes wired-up during development is essential not only to gain insight into its normal functioning, but also to progress in the comprehension of neurological and psychiatric disease. Indeed, there is increasing evidence that defects occurring during embryonic development lead to impaired functioning of the cerebral cortex, and that such defects may underlie the etiology of several human pathologies, including schizophrenia and autism spectrum disorders. Genetic studies in both humans and mice have enabled clinicians and neurobiologists to dissect molecular cascades that govern the formation of the cerebral cortex, in particular those directing the generation and migration of different populations of cortical neurons. However, similar large-scale unbiased studies have yet to be developed to study the formation of the major axonal tracts that wire the cerebral cortex.The dorsal thalamus is a sensory gateway of the brain that receives visual, somatosensory and auditory information. Thalamocortical axons convey this sensory information from the dorsal thalamus to the cerebral cortex and hence are essential to brain function. They follow a long and complex path to reach their final cortical targets, making successive changes in direction as they navigate from one intermediate target to another (Figure 1). Indeed, from embryonic day 13 (E13) in mice, dorsal thalamus axons extend ventrally, turn laterally close to the hypothalamus to cross the boundary between embryonic diencephalon and telencephalon, enter the ventral telencephalon, grow in the internal capsule, and fan out into smaller axonal bundles before crossing the cortico-striatal boundary at E15. The axons then turn dorsally into the intermediate zone of the cerebral cortex, where they interact with cells of the cortical subplate before extending collateral branches to reach their final target in lay
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