Splenium of Corpus Callosum: Patterns of Interhemispheric Interaction in Children and Adults

The splenium of the corpus callosum connects the posterior cortices with fibers varying in size from thin late-myelinating axons in the anterior part, predominantly connecting parietal and temporal areas, to thick early-myelinating fibers in the posterior part, linking primary and secondary visual areas. In the adult human brain, the function of the splenium in a given area is defined by the specialization of the area and implemented via excitation and/or suppression of the contralateral homotopic and heterotopic areas at the same or different level of visual hierarchy. These mechanisms are facilitated by interhemispheric synchronization of oscillatory activity, also supported by the splenium. In postnatal ontogenesis, structural MRI reveals a protracted formation of the splenium during the first two decades of human life. In doing so, the slow myelination of the splenium correlates with the formation of interhemispheric excitatory influences in the extrastriate areas and the EEG synchronization, while the gradual increase of inhibitory effects in the striate cortex is linked to the local inhibitory circuitry. Reshaping interactions between interhemispherically distributed networks under various perceptual contexts allows sparsification of responses to superfluous information from the visual environment, leading to a reduction of metabolic and structural redundancy in a child's brain.

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Encephalometry on the medial face of the human brain hemisphere: a necropsy study

Arquivos de Neuro-Psiquiatria ◽

10.1590/s0004-282x2005000300013 ◽

2005 ◽

Vol 63 (2b) ◽

pp. 430-436 ◽

Cited By ~ 2

Author(s):

Paula J. Ribeiro ◽

Serafim V. Cricenti V. ◽

Carmen L.P. Lancellotti

Keyword(s):

Corpus Callosum ◽

Human Brain ◽

Frontal Cortex ◽

Anterior Part ◽

Average Distance ◽

Posterior Part ◽

Cerebral Hemispheres ◽

Frontal Pole ◽

Occipital Pole ◽

The Right

This study aims to evaluate the dimensions of the human brain, specifically in the frontal cortex, helping the analysis of neuroimaging. A form was made to register and describe encephalic measurements and 81 cerebral hemispheres (CH) were analyzed. Male individuals showed larger CH length; wider superior frontal gyrus in the right CH; bigger encephalic weight and corpus callosum (CC) width. The proportion of measurement from the frontal pole to the most anterior part of the CC genu, related to the CH length gets smaller with aging, whereas the average distance from the most posterior part of the splenum of the CC to the occipital pole was bigger in both male CHs and there was a tendency of decrease in this difference with aging.

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Identification of the key role of white matter alteration in the pathogenesis of Huntington's Disease

10.1101/2021.06.21.449242 ◽

2021 ◽

Author(s):

Jean-Baptiste Perot ◽

Marina Celestine ◽

Marco Palombo ◽

Marc Dhenain ◽

Sandrine Humbert ◽

...

Keyword(s):

White Matter ◽

Corpus Callosum ◽

Neurodegenerative Disorder ◽

Diffusion Tensor ◽

Chemical Exchange ◽

Anterior Part ◽

Magnetization Transfer ◽

Structural Mri ◽

Chemical Exchange Saturation Transfer

Pathogenesis of the inherited neurodegenerative disorder Huntington s Disease (HD) is complex and progressive, with a long presymptomatic phase in which subtle changes occur in the brain of gene carriers up to 15 years before the onset of symptoms. Thus, there is a need of early, functional biomarker to better understand disease progression and to evaluate treatment efficacy far from onset. In particular, recent studies have shown that white matter may be affected early in HD. In this study, we scanned longitudinally Ki140CAG mice with structural MRI, Diffusion Tensor Imaging (DTI), Chemical Exchange Saturation Transfer of glutamate (gluCEST) and Magnetization Transfer (MT) imaging, in order to assess white matter integrity over the life of this very progressive mouse model. Our results show early defects of diffusion properties in the anterior part of the corpus callosum, preceding gluCEST defects in the same region (-10.8% at 8 months, -19% at 12 months) that spread to adjacent regions. At 12 months, frontal (-7.3%) and piriform (-16.7%) cortices showed reduced gluCEST, as well as the pallidum (-21.0%). MT imaging showed reduced signal in the septum (-21.7%) at 12 months. Cortical and striatal atrophy then appear at 18 months. Vulnerability of the striatum and motor cortex, combined with alterations of anterior corpus callosum, seems to point out the pivotal role of white matter, in the pathogenesis of HD and the pertinence of gluCEST and DTI as biomarkers in HD.

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Fine structure of the rectal papillae of the oriental fruuit fly, Dacus dorsalis Hendel (Tephritidae, Diptera Insecta)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100160042 ◽

1990 ◽

Vol 48 (3) ◽

pp. 498-499

Author(s):

Len Wen-Yung ◽

Mei-Jung Lin

Keyword(s):

Fine Structure ◽

Cell Membrane ◽

Intercellular Space ◽

Anterior Part ◽

Apical Cell ◽

Posterior Part ◽

Apical Cell Membrane ◽

Dacus Dorsalis ◽

Radial Cell ◽

Circular Base

Four cone-shaped rectal papillae locate at the anterior part of the rectum in Dacus dorsalis fly. The circular base of the papilla protrudes into the haemolymph (Fig. 1,2) and the rest cone-shaped tip (Fig. 2) inserts in the rectal lumen. The base is surrounded with the cuticle (Fig. 5). The internal structure of the rectal papilla (Fig. 3) comprises of the cortex with the columnar epithelial cells and a rod-shaped medulla. Between them, there is the infundibular space and many trabeculae connect each other. Several tracheae insert into the papilla through the top of the medulla, then run into the cortical epithelium and locate in the intercellular space. The intercellular sinuses distribute in the posterior part of the rectal papilla.The cortex of the base divides into about thirty segments. Between segments there is a radial cell (Fig. 4). Under the cuticle, the apical cell membrane of the cortical epithelium is folded into a regular border of leaflets (Fig. 5).

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Collicular Vision Guides Nonconscious Behavior

Journal of Cognitive Neuroscience ◽

10.1162/jocn.2009.21225 ◽

2010 ◽

Vol 22 (5) ◽

pp. 888-902 ◽

Cited By ~ 84

Author(s):

Marco Tamietto ◽

Franco Cauda ◽

Luca Latini Corazzini ◽

Silvia Savazzi ◽

Carlo A. Marzi ◽

...

Keyword(s):

Visual Experience ◽

Striate Cortex ◽

Visual Signals ◽

Visually Guided ◽

Visuomotor Integration ◽

Motor Processing ◽

Pupillary Responses ◽

Cortex Area ◽

Extrastriate Areas

Following destruction or deafferentation of primary visual cortex (area V1, striate cortex), clinical blindness ensues, but residual visual functions may, nevertheless, persist without perceptual consciousness (a condition termed blindsight). The study of patients with such lesions thus offers a unique opportunity to investigate what visual capacities are mediated by the extrastriate pathways that bypass V1. Here we provide evidence for a crucial role of the collicular–extrastriate pathway in nonconscious visuomotor integration by showing that, in the absence of V1, the superior colliculus (SC) is essential to translate visual signals that cannot be consciously perceived into motor outputs. We found that a gray stimulus presented in the blind field of a patient with unilateral V1 loss, although not consciously seen, can influence his behavioral and pupillary responses to consciously perceived stimuli in the intact field (implicit bilateral summation). Notably, this effect was accompanied by selective activations in the SC and in occipito-temporal extrastriate areas. However, when instead of gray stimuli we presented purple stimuli, which predominantly draw on S-cones and are thus invisible to the SC, any evidence of implicit visuomotor integration disappeared and activations in the SC dropped significantly. The present findings show that the SC acts as an interface between sensory and motor processing in the human brain, thereby providing a contribution to visually guided behavior that may remain functionally and anatomically segregated from the geniculo-striate pathway and entirely outside conscious visual experience.

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The genus Gennadas (Benthesicymidae: Decapoda): morphology of copulatory characters, phylogeny and coevolution of genital structures

Royal Society Open Science ◽

10.1098/rsos.171288 ◽

2017 ◽

Vol 4 (12) ◽

pp. 171288 ◽

Cited By ~ 5

Author(s):

Alexander L. Vereshchaka ◽

Anastasia A. Lunina ◽

Jørgen Olesen

Keyword(s):

New Species ◽

Anterior Part ◽

Phylogenetic Analyses ◽

Posterior Part ◽

Key To Species ◽

Internal Part ◽

Species Groups ◽

Aristaeomorpha Foliacea ◽

External Part ◽

Scanning Electron

Species within Gennadas differ from each other largely only in male (petasma) and female (thelycum) copulatory characters, which were restudied in scanning electron microscopy and used as a basis for phylogenetic analyses. Twenty-six petasma characters and 49 thelycum characters were identified. All 16 recognized species of Gennadas and Aristaeomorpha foliacea (outgroup) were included as terminals. Four robust monophyletic clades were retrieved, described and diagnosed as new species groups. The thelycum characters had greater impact on tree topology and supported deeper nodes than did the petasma characters. We hypothesize that features of the thelycum evolved first followed by aspects of the petasma. Relatively more conservative characters include parts of the sternites of the thelycum and of the petasma, while the scuti and protuberances on the thelycum and the shape and subdivisions of the petasma lobes are evolutionarily plastic. We identified two groups of copulatory characters, which are likely coupled functionally and interlinked evolutionarily: (i) the external part of the petasma and the posterior part of the thelycum and (ii) the internal part of the petasma and anterior part of the thelycum. We reconstruct possible mating position during copulation for each of the new species groups presented here. We also present an updated key to genera of Benthesicymidae and key to species of Gennadas .

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Interacting functions of snail, twist and huckebein during the early development of germ layers in Drosophila

Development ◽

10.1242/dev.120.5.1137 ◽

1994 ◽

Vol 120 (5) ◽

pp. 1137-1150 ◽

Cited By ~ 16

Author(s):

R. Reuter ◽

M. Leptin

Keyword(s):

Transcription Factors ◽

Digestive Tract ◽

Early Development ◽

Target Genes ◽

Anterior Part ◽

Posterior Part ◽

Germ Layers ◽

Mesoderm Development ◽

Ventral Furrow

Two zygotic genes, snail (sna) and twist (twi), are required for mesoderm development, which begins with the formation of the ventral furrow. Both twi and sna are expressed ventrally in the blastoderm, encode transcription factors and promote the invagination of the ventral furrow by activating or repressing appropriate target genes. However, sna and twi alone do not define the position of the ventral furrow, since they are also expressed in ventral cells that do not invaginate. We show that huckebein (hkb) sets the anterior and the posterior borders of the ventral furrow, but acts by different modes of regulation. In the posterior part of the blastoderm, hkb represses the expression of sna in the endodermal primordium (which we suggest to be adjacent to the mesodermal primordium). In the anterior part, hkb antagonizes the activation of target genes by twi and sna. Here, bicoid permits the co-expression of hkb, sna and twi, which are all required for the development of the anterior digestive tract. We suggest that mesodermal fate is determined where sna and twi but not hkb are expressed. Anteriorly hkb together with sna determines endodermal fate, and hkb together with sna and twi are required for foregut development.

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A new species of Pista Malmgren, 1866 (Polychaeta, Terebellidae) from the north-western Mediterranean Sea

ZooKeys ◽

10.3897/zookeys.838.28634 ◽

2019 ◽

Vol 838 ◽

pp. 71-84

Author(s):

Céline Labrune ◽

Nicolas Lavesque ◽

Paulo Bonifácio ◽

Pat Hutchings

Keyword(s):

New Species ◽

Mediterranean Sea ◽

Anterior Part ◽

Posterior Part ◽

Western Mediterranean ◽

Single Pair ◽

The North ◽

Western Mediterranean Sea ◽

North Western ◽

A New Species

A new species of Terebellidae, Pistacolinisp. n., has been identified from the harbour of Banyuls-sur-Mer, north-western Mediterranean Sea. This new species was found in very high densities, exclusively in gravelly sand deposited manually, and was not found in the original source habitat of the gravel. This species is characterized by the colour of the ventral shields with pinkish anterior part and a blood red posterior part in live specimens, a pair of unequal-sized plumose branchiae inserted on segment II and anterior thoracic neuropodia with long-handled uncini. The presence of long-handled uncini even in the smallest specimens constitutes the major difference between Pistacolinisp. n. and other Pista species with a single pair of branchiae such as P.lornensis and P.bansei.

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Influence of different orientations and rates of bidirectional distraction osteogenesis of the mandibular corpus: a three-dimensional study.

Journal Of Oral Research ◽

10.17126/joralres.2019.083 ◽

2019 ◽

Vol S (1) ◽

pp. 11-14

Author(s):

Lamiaa A. Hasan ◽

◽

Nada M. Al-Sayagh ◽

Lara R. Al-Banaa ◽

◽

...

Keyword(s):

Distraction Osteogenesis ◽

Anterior Part ◽

Three Dimensional ◽

Posterior Part ◽

Von Mises Stress ◽

Occlusal Plane ◽

Three Dimensional Model ◽

Direction Parallel ◽

Inferior Border ◽

Von Mises

Objective: The objective of this study was to evaluate the biomechanical effect of mandibular corpus distraction osteogenesis with different orientations and rates. Materials and Methods: A three-dimensional model of the mandible was created. The vertical surgical cut was made, the force was applied horizontally in a bidirectional manner within two orientations: parallel to the occlusal plane and parallel to the inferior border of the mandible with three rates (0.5mm, 1mm and 1.5mm). Results: The maximum values for von Mises stress when the force was applied parallel to the inferior border of the mandible with all three rates were smaller than those with force direction parallel to the occlusal plane. The displacement in all three directions x, y, and z were not parallel and prominent in the anterior part of the mandible, while the movement at the posterior part is negligible, x and z displacement were bigger when force was applied parallel to the inferior border of the mandible, z displacement was more prominent than x and y displacement, both directions produced upward rotation of the mandible, this rotation was more noticeable when the force was applied parallel to the inferior border of the mandible. Conclusions: A vertical cut can be used in the patient with a long anterior face. This site of distraction achieves more lengthening of mandible than expansion.

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TERMINOLOGY OF PALEOZOIC PLACODERM FISHES (ANTIARCHI) EXOSKELETAL ELEMENTS

THE LIFE OF THE EARTH ◽

10.29003/m2025.0514-7468.2020_43_2/195-201 ◽

2021 ◽

Vol 43 (2) ◽

pp. 195-201

Author(s):

Sergey Moloshnikov ◽

Keyword(s):

Anterior Part ◽

Posterior Part ◽

Shoulder Girdle ◽

Russian Language ◽

Postcranial Skeleton ◽

Incorrect Conclusion ◽

Similar Term ◽

Early Vertebrates ◽

Language Literature ◽

Dorsal Scute

The terminology and morphology of plates of the posterior part of the antiarch head shield (Placodermi, Antiarchi) are discussed. The terms «zatilochnaya» and «bokovaya (kraevaya) zatilochnaya» was previously accepted in antiarch skulls and are suggested for use in Russian-language literature. These terms are more correct and clearly define a position and development of these plates in the head shield of antiarchs. The titles «zagrivkovaya (nuchalnaya)» and «bokovaya zagrivkovaya (paranuchalnaya)», recently applied to them in Russian-language literature may indicate a connection in development with an anterior part of a trunk. A similar term is used for acipenserid exoskeleton. The acipenserid «nuchalnaya kost’» is located posterior to the «verchnezatilochnaya» (after Gurtovoi), and embryonically developed in an anterior part of the trunk over basidorsals and bones of the shoulder girdle. The name «pervaya spinnaya plastinka» (first dorsal scute: after Hilton and others) is also use for this bone. The term «zagrivkovaya plastinka» is used in other vertebrate skeletons, for example, in turtles; this name denotes the unpaired element of a carapace (postcranial skeleton). Using the terms «zagrivkovaya (nuchalnaya)» and «bokovaya zagrivkovaya (paranuchalnaya)» in the morphology of antiarchs and other placoderms may lead confusion in the terminology of skeletal elements at early vertebrates, incorrect conclusion of their homology, structure and development of the head shield of these unusual fishes.

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Hedgehog organises the pattern and polarity of epidermal cells in the Drosophila abdomen

Development ◽

10.1242/dev.124.11.2143 ◽

1997 ◽

Vol 124 (11) ◽

pp. 2143-2154 ◽

Cited By ~ 16

Author(s):

G. Struhl ◽

D.A. Barbash ◽

P.A. Lawrence

Keyword(s):

Anterior Part ◽

Posterior Part ◽

Cell Types ◽

Epidermal Cells ◽

Concentration Gradients ◽

Cell Pattern ◽

Different Cell Types ◽

Adult Drosophila

The abdomen of adult Drosophila, like that of other insects, is formed by a continuous epithelium spanning several segments. Each segment is subdivided into an anterior (A) and posterior (P) compartment, distinguished by activity of the selector gene engrailed (en) in P but not A compartment cells. Here we provide evidence that Hedgehog (Hh), a protein secreted by P compartment cells, spreads into each A compartment across the anterior and the posterior boundaries to form opposing concentration gradients that organize cell pattern and polarity. We find that anteriorly and posteriorly situated cells within the A compartment respond in distinct ways to Hh: they express different combinations of genes and form different cell types. They also form polarised structures that, in the anterior part, point down the Hh gradient and, in the posterior part, point up the gradient - therefore all structures point posteriorly. Finally, we show that ectopic Hh can induce cells in the middle of each A compartment to activate en. Where this happens, A compartment cells are transformed into an ectopic P compartment and reorganise pattern and polarity both within and around the transformed tissue. Many of these results are unexpected and lead us to reassess the role of gradients and compartments in patterning insect segments.

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