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Results for “cortical structure”

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At least 19 recordsLinked to original sources

PubMed2006

A knowledge-guided active model method of cortical structure segmentation on pediatric MR images.

PURPOSE: To develop an automated method for quantification of cortical structures on pediatric MR images. MATERIALS AND METHODS: A knowledge-guided active model (KAM) approach was proposed with a novel object function similar to the Gibbs free energy function. Triangular mesh models were transformed to images of a given subject by maximizing entropy, and then actively slithered to boundaries of structures by minimizing enthalpy. Volumetric results and image similarities of 10 different cortical structures segmented by KAM were compared with those traced manually. Furthermore, the segmentation performances of KAM and SPM2, (statistical parametric mapping, a MATLAB software package) were compared. RESULTS: The averaged volumetric agreements between KAM- and manually-defined structures (both 0.95 for structures in healthy children and children with medulloblastoma) were higher than the volumetric agreement for SPM2 (0.90 and 0.80, respectively). The similarity measurements (kappa) between KAM- and manually-defined structures (0.95 and 0.93, respectively) were higher than those for SPM2 (both 0.86). CONCLUSION: We have developed a novel automatic algorithm, KAM, for segmentation of cortical structures on MR images of pediatric patients. Our preliminary results indicated that when segmenting cortical structures, KAM was in better agreement with manually-delineated structures than SPM2. KAM can potentially be used to segment cortical structures for conformal radiation therapy planning and for quantitative evaluation of changes in disease or abnormality.

Algorithms↗

PubMed2004

Deformable registration of cortical structures via hybrid volumetric and surface warping.

Registration of cortical structures across individuals is a very important step for quantitative analysis of the human brain cortex. This paper presents a method for deformable registration of cortical structures across individuals, using hybrid volumetric and surface warping. In the first step, a feature-based volumetric registration algorithm is used to warp a model cortical surface to the individual's space. This step greatly reduces the variation between the model and individual, thus providing a good initialization for the next step of surface warping. In the second step, a surface registration method, based on matching geometric attributes, warps the model surface to the individual. Point correspondences are also established at this step. The attribute vector, as the morphological signature of surface, was designed to be as distinctive as possible, so that each vertex on the model surface can find its correspondence on the individual surface. Experimental results on both synthesized and real brain data demonstrate the performance of the proposed method in the registration of cortical structures across individuals.

Artifacts↗

PubMedDate not supplied

[Effect of furosemide on intact and ischemic rat kidney cortical structures].

Biomicroscopy and microphotography of cortical structures of rat kidneys have shown that furosemide produces a significant increase in the internal and external diameters of the tubules without substantial change in the wall thickness and width of intertubular space. In renal ischemia, the wall thickness and external diameter of the tubules progressively increase. The majority of the tubules show the disappearance of the lumen. In the course of the blood flow recovery, the wall thickening remains unchanged. Ligation of the renal vessels in the presence of furosemide administration also leads to the collapse of the tubules. However, the thickness of the tubular wall decreases while the lumen rises during ischemia. The role of the hydrodynamic effect in the mechanism of anti-ischemic action of furosemid is discussed.

Animals↗

PubMedDate not supplied

Cortical structure predicts the pattern of corticocortical connections.

Cortical areas are linked through pathways which originate and terminate in specific layers. The factors underlying which layers are involved in specific connections are not well understood. Here we tested whether cortical structure can predict the pattern as well as the relative distribution of projection neurons and axonal terminals in cortical layers, studied with retrograde and anterograde tracers. We used the prefrontal cortices in the rhesus monkey as a model system because their laminar organization varies systematically, ranging from areas that have only three identifiable layers, to those that have six layers. We rated each prefrontal area based on the number and definition of its cortical layers (level 1, lowest; level 5, highest). The structural model accurately predicted the laminar pattern of connections in approximately 80% of the cases. Thus, projection neurons from a higher-level cortex originated mostly in the upper layers and their axons terminated predominantly in the deep layers (4-6) of a lower-level cortex. Conversely, most projection neurons from a lower-level area originated in the deep layers and their axons terminated predominantly in the upper layers (1-3) of a higher-level area. In addition, the structural model accurately predicted that the proportion of projection neurons or axonal terminals in the upper to the deep layers would vary as a function of the number of levels between the connected cortices. The power of this structural model lies in its potential to predict patterns of connections in the human cortex, where invasive procedures are precluded.

Animals↗

PubMed1997

Three-dimensional imaging of cortical structure, function and glioma for tumor resection.

UNLABELLED: A three-dimensional brain imaging protocol with PET and MRI was used to visualize the cortical structure in relation to brain function and glioma infiltration to determine tumor resectability. METHODS: Sixteen patients with glioma had a PET scan with 11C-methionine to visualize tumor infiltration. The PET images were co-registered to the patients' own MRI reconstructed to the three-dimensional brain surface images to indicate the gyral structure and the extent of tumor infiltration. Thirteen patients, who bore tumors adjacent to the language or motor cortex, had H2 15O activation study to locate the eloquent cortex. The area of tumor infiltration was superimposed on the brain surface images together with the language and/or motor cortex. RESULTS: When a tumor was located within a single gyrus without influencing surface cortical gyrus pattern, the motor and language areas were identified morphologically by three-dimensional surface image alone. However, when the tumor caused swelling and deformation of cortical structure, functional mapping with H2(15)O activation technique was essential in locating them correctly. In such cases, the combined mapping of the facial motor area with oral movement and the language area with word repetition was the most useful method to identify the parasylvian structure in the dominant hemisphere. Total or near total resection of low-grade glioma in eight patients and the effective decompression of the active part of the malignant glioma in four patients was completed without causing functional neurological deterioration. CONCLUSION: The three-dimensional expression of cortical structure and function combined with PET glioma imaging with 11C-methionine is useful for radical resection of cerebral glioma.

Adult↗

PubMed2004

[Stereologic analysis of renal cortical structures during compensatory hypertrophy in rats].

The qualitative and quantitative study of renal cortical structures was performed seven days after unilateral nephrectomy. Adult Wistar rats (10 male and 10 female) were ether-anaesthetized and the kidneys were removed by dorsolateral approach. Renal hypertrophy was determined by measurement of kidney dry mass. The samples of renal tissue were embedded in paraffin, sectioned at 6 microns and stained by azan and haematoxylineosin methods. The volume densities of renal corpuscles, the epithelium of tubules, luminal space of tubules and cortical interstitial structures were calculated using Weibel's multipurpose test system M 42. The qualitative analysis was performed to determine possible structural sex differences of cortical parenchyma during compensatory hypertrophy. There was no significant difference in volume densities of renal corpuscles and distal tubules between control and hypertrophic kidney. The volume density of the epithelium of proximal tubules and interstitial blood vessels were statistically significant increased in hypertrophic kidney compared to the values determined in control kidney. The volume density of luminal space of proximal tubules and interstitial tissues were statistically significant decreased in hypertrophy compared to control kidney. The data from present studies shows that the increase in epithelial volume of proximal tubules and interstitial blood vessels volume have the primary role in compensatory kidney enlargement after unilateral nephrectomy, while renal corpuscles do not participate significantly.

Adaptation, Physiological↗

PubMed1991

Time-dependent sequential increases in [14C]2-deoxyglucose uptake in subcortical and cortical structures during memory consolidation of an operant training in mice.

Previous results have suggested that memory processing may involve the sequential activation of subcortical and cortical structures. To study this phenomenon, we have examined the immediate (15 min) and delayed (220 min) metabolic changes produced in BALB/c mice by a partial training session in a bar-pressing appetitive task, using the [14C]-2-deoxyglucose (2-DG) relative glucose uptake method. These relative metabolic changes were compared to the ones produced in several control groups: untrained animals, sham-conditioned animals, overtrained animals, and animals forced to walk on a moving belt (immediate and delayed condition). Animals were given a single intrajugular injection (5 microCi) of 2-DG either 5 min before or 3 h (delayed condition) after the second training session. Forty minutes after the 2-DG injection, the animals were sacrificed and their brains processed for autoradiography. At the 15-min delay, a large 2-DG labeling increase was found in partially trained animals for various subcortical areas (septum, diagonal band, hippocampus, thalamus, and mammillary bodies) while a much smaller increase was found in four cortical areas (frontal, cingulate, parietal, and sensory motor cortices). At the 220-min delay, we observed a large 2-DG labeling increase in cortical (frontal, pyriform, and cingulate cortices) and subicular areas while a moderate 2-DG labeling increase was observed in entorhinal cortex and the diagonal band. These results show that, shortly after training, subcortical structures are preferentially activated while cortical structures are much less activated. Three hours later, at a time when retention performances have been shown to improve spontaneously in the same strain of mice and in the same task, cortical structures are highly activated.

Animals↗

PubMed2025

Asthma causally affects the brain cortical structure: a Mendelian randomization study.

OBJECTIVE: The potential causal relationship between asthma and brain structures remains uncertain. We performed a two-sample Mendelian randomization to investigate the causal effects of various asthma phenotypes - unspecified asthma, moderate-to-severe asthma, childhood-onset asthma, and adult-onset asthma (AOA) - on cerebral cortex structure. METHODS: We utilized phenotype data derived from genome-wide association studies (GWASs). The ENIGMA Consortium GWAS provided outcome variables for surface area (SA) and thickness across the whole brain and 34 region-specific areas of the cerebral cortex. Using the inverse variance-weighted method as our primary estimation approach, we employed several techniques, including Cochran's Q statistic, the MR-PRESSO global test, MR-Egger, and weighted median, to assess heterogeneity and pleiotropy, thereby ensuring the robustness of our findings. Additionally, we conducted enrichment analyses of gene sets with causal effects on cortical structure and applied bioinformatics techniques to construct interaction networks and identify hub nodes. RESULTS: At the global level, AOA was associated with a significant reduction in full cortical SA (β = -58.49 mm2, p = 0.017). In regional analyses, moderate-to-severe asthma exhibited a more pronounced impact on the cerebral cortex compared to other phenotypes. Enrichment analysis revealed that pathways implicated in brain morphology among asthma patients were primarily linked to immune and inflammation-driven pathways. CONCLUSIONS: Our findings provide new evidence supporting a causal relationship between asthma and alterations in cortical structure, offering potential explanations for cognitive and psychiatric impairments observed in individual post-asthma.

Humans↗

PubMed2006

Analysis of synchrony demonstrates 'pain networks' defined by rapidly switching, task-specific, functional connectivity between pain-related cortical structures.

Imaging studies indicate that experimental pain is processed in multiple cortical areas which are often characterized as a network. However, the functional connectivity within the network and the other properties of the network is poorly understood. Substantial evidence demonstrates that synchronous oscillations between two cortical areas may indicate functional connectivity between those areas. We test the hypothesis that cortical areas with pain-related activity are functionally connected during attention to a painful stimulus. We stimulated with a painful, cutaneous, laser stimulus and recorded the response directly from the cortical surface (electrocorticography--ECoG) over primary somatosensory (SI), parasylvian (PS), and medial frontal (MF) cortex through subdural electrodes implanted for treatment of epilepsy. The results demonstrate synchrony of ECoGs between cortical structures receiving input from nociceptors, as indicated by the occurrence of laser-evoked potentials (LEPs) and/or event-related desynchronization (ERD). Prior to the stimulus, directed attention to the painful stimulus consistently increased the degree of synchrony between SI and PS regions, as the subject anticipated the stimulus. After the laser stimulus, directed attention to the painful stimulus consistently increased the degree of synchrony between SI and MF cortex, as the subject responded by counting the stimulus. Therefore, attention to painful stimuli always enhanced synchrony between cortical pain-related structures. The pattern of this synchrony changed as the patient switched tasks from anticipation of the stimulus to counting the stimulus. These results are the first compelling evidence of pain networks characterized by rapidly switching, task-specific functional connectivity.

Adult↗

PubMedDate not supplied

Quantitative morphology of renal cortical structures during compensatory hypertrophy.

The compensatory hypertrophy in different renal cortical structures was studied in rats 10 and 21 days after unilateral nephrectomy (UNX). Quantitative morphological/stereological analysis revealed significant increases in total renal cortical volume--33% on day 10 and 48% on day 21--after UNX. These changes were paralleled by significant increments in the volumes of proximal convoluted tubule (PCT, 55%), distal convoluted tubule (DCT, 114%), and cortical collecting duct (CCD, 106%) segments on day 10. The corresponding changes on day 21 were 76, 122, and 212%, respectively. These alterations were accompanied by increases in segment length; 3% PCT, 23% DCT, and 50% CCD on day 10 and 9% PCT, 30% DCT, and 142% CCD on day 21 after UNX. The total luminal and basolateral cell membrane surface areas also exhibited a time-dependent increase after UNX. The increments in both luminal and basolateral membrane domains in PCT and DCT after 10 days were not significant, but reached significance after 21 days (PCT: luminal membrane 21%, basolateral membrane 63%; DCT: luminal membrane 98%, basolateral membrane 63%). In contrast, CCD membrane areas had increased substantially already 10 days after UNX (luminal membrane 92%, basolateral membrane 71%). It declined subsequently by day 21 (luminal membrane 57%, basolateral membrane 32%). The cell rubidium concentration after a 30-second rubidium infusion, an index of Na-K-ATPase activity, as well as sodium concentrations were unaltered in cells of all nephron segments investigated. Altogether the stereological analysis shows that the compensatory increase in organ volume can be attributed primarily to an increase in nephron epithelial volume. The PCT responds with 'radial' hypertrophy (thickening of the tubular epithelial wall), while the DCT undergoes 'length' hypertrophy (increase of tubular length without thickening of the tubular wall and without an increase in number of cells). This type of hypertrophy is especially prominent on day 21 after UNX for the CCD which doubles in length. Only on day 10 does the CCD seem to respond with hyperplasia. Adaptive changes in response to UNX develop gradually. Only a few of the morphological parameters studied had completed their change by 10 days, the majority required longer.

Adaptation, Physiological↗

PubMed1997

Evaluation of the cortical structure in high resolution CT images of lumbar vertebrae by analysing low bone mineral density clusters and cortical profiles.

The structural classification of trabecular bone is of considerable clinical importance for the diagnosis of osteoporosis. Assessment of the cortical bone mineral density (BMD) and analysis of cortical structure is necessary because the cortex is also affected by osteoporosis. We describe a method for the automatic classification of the cortex from its structure on high resolution (HR) CT images. The method is based on the distribution of areas with low BMD in the cortex. Two different approaches are presented; one uses the grey scale profile of the cortical ridge, and the other one evaluates the distribution of connected regions (clusters) of low BMD. i.e. areas that lie below a certain threshold value. In HRCT images from 22 lumbar vertebrae, the number of intersections of the cortical intensity profile with a horizontal line was determined at various positions of this threshold line. At a certain position, there was a local maximum in the number of intersections which was 38% higher in the osteoporotic cases. The maximum shows a moderate correlation with the cortical BMD of rni = -0.72 (p < 0.0001). The number nc of connected regions (clusters) with pixel values below a certain threshold value was determined in relation to the threshold value T. The resulting function nc(T) shows a relative maximum slightly below the average grey scale value of the respective image. The curve depends on the degree of osteoporosis: the height of the maximum (i.e. the maximal number of clusters ncmax) allows distinction to be made between different degrees of osteoporosis, and ncmax shows a correlation with the cortical BMD of rnc = -0.84 (p < 0.0001).

Aged↗

PubMed1995

The vegetative micronucleus has a critical role in maintenance of cortical structure in Tetrahymena thermophila.

The vegetative role of the germinal micronucleus of Tetrahymena thermophila was studied. Amicronucleate cells that had spontaneously arisen in star strains (very aged cones with defective micronuclei) were observed in B* as well as in A* and in C* and were found to lack the oral apparatus and to have disordered ciliary rows. To reduce uncertainty given the very small micronucleus and possible effects of aging factors, we induced amicronucleate cells in a young clone by treatment with the antitubulin drug, nocodazole, and observed their cortical structure and nuclei. Amicronucleate cells gradually lost their oral apparatus and then their ciliary rows became disordered, even without cell division, and they became crinkled cells. It can be concluded that the vegetative micronucleus appears to play a critical role in the maintenance of the cortical structure, especially of the oral apparatus.

Animals↗

PubMed2000

Influence of orthotopic placement on the incorporation and mechanical strength of a loaded structural cortical graft: an experimental study in rabbits.

The biological and mechanical behavior of loaded cortical autografts were evaluated in an experimental study using 40 adult male New Zealand rabbits divided into 4 groups. A double osteotomy was performed on all animals at the mid-diaphysis of the right ulna. The bone segment (5 mm) in between the osteotomies was considered a cortical autograft and fixed with an intramedullary Kirschner wire. The graft was fixed in an orthotopic manner in groups A and C, and rotated 180 degrees in groups B and D. After the animals were sacrificed (at 2 months for groups A and B and at 4 months for groups C and D), bone mineral density, graft cross-sectional geometry, and SSI index were assessed. Mechanical testing of the grafted area was carried out using a three-point bending configuration, and the parameter fracture load was assessed. Graft union and incorporation also was studied in histologic sections. In group C (orthotopic graft placement--4 months), bone specimens showed statistically significantly higher values for fracture load, total cross-sectional area, volumetric total bone mass and density, and polar SSI (P values < or = .05) compared to the other groups. In the same group, union and incorporation of the graft was complete, the cortex showed low porosity, and the collagen fibers were mature and properly oriented. Structural cortical bone autografts placed in an orthotopic manner recognize the new mechanical environment as optimal and thus their biological and mechanical behavior are enhanced. Loaded structural cortical grafts should be placed in an orthotopic manner when used for the management of cortical bone defects.

Analysis of Variance↗

PubMed2002

BetaIII tubulin-expressing neurons reveal enhanced neurogenesis in hippocampal and cortical structures after a contusion trauma in rats.

Neurogenesis is not only restricted to embryonic development, but also occurs in adult mammalian brains, including human. In this study, evidence is provided, that neurogenesis is involved in the repair of hippocampal and cortical structures after CNS injury. Cortical contusion was induced in 8-week-old Wistar rats. This trauma resulted in a primary cortical lesion and ipsilateral distant remote hippocampal damage, involving primarily CA3-pyramidal cells. The progression of injury was followed over a time course of 7 days, using Nissl-staining and a monoclonal antibody against betaIII tubulin-a specific marker for neurogenic cells. Nissl staining showed a partial recovery of damaged cortical and hippocampal cells at day 7. This recovery was accompanied by an increase of neurogenic cells in these structures, particularly in the dentate gyrus and the neocortical areas. Taken together, these findings provide evidence for the involvement of neurogenesis in the repair processes after traumatic brain injury.

Animals↗

PubMed2026

Linking cortical structure and delirium in the elderly: insights from cohort study and shared genetic risk analysis.

BACKGROUND: This study aimed to assess the association between regional cortical changes measured via baseline magnetic resonance imaging (MRI) and the incidence of delirium. METHODS: Observational associations were assessed using a prospective cohort from the UK Biobank and an independent clinical cohort. The population-based study included participants aged 60 years or older who had undergone structural brain MRI since 2014. Regional cortical volume, mean thickness, and surface area were extracted based on the Desikan-Killiany cortical atlas. Delirium was defined using ICD-10 diagnostic codes. Additionally, preoperative brain MRI images from participants in another cohort were collected and automatically segmented using deep learning algorithms to obtain cortical measurements. Logistic analysis was performed to investigate the associations between cerebral cortical structure and delirium risk. Lastly, genome-wide association study data derived from the ENIGMA Consortium and FinnGen Biobank were utilized to conduct conditional/conjunctional false discovery rate (cond/conjFDR) analyses to identify shared genetic loci associated with cortical structures and delirium. RESULTS: This observational analysis included 31,890 participants from the UK Biobank and 152 participants from an independent cohort. In the UK Biobank cohort, decreased cortical thickness in the 17 regions was associated with a significantly increased risk of delirium. Similarly, a preoperative reduction in cortical volume in 7 regions was associated with an increased risk of delirium in the independent cohort. Besides, 100 single-nucleotide polymorphisms (SNPs) were identified as significantly associated with cortical structures when conditioned on delirium. Finally, colocalization analysis demonstrated that these pleiotropic risk loci modulated the expression of NT5C2, RGP1, CCDC25, TPM2, EEF1AKMT2, IQANK1 and LHPP in blood and brain tissues. CONCLUSION: Regional cortical atrophy is associated with an increased risk of delirium in the elderly. Brain MRI examinations may be beneficial for preoperative delirium risk assessment in elderly individuals undergoing elective surgery.

Humans↗

PubMed2006

The aPKC-PAR-6-PAR-3 cell polarity complex localizes to the centrosome attracting body, a macroscopic cortical structure responsible for asymmetric divisions in the early ascidian embryo.

Posterior blastomeres of 8-cell stage ascidian embryos undergo a series of asymmetric divisions that generate cells of unequal sizes and segregate muscle from germ cell fates. These divisions are orchestrated by a macroscopic cortical structure, the ;centrosome attracting body' (CAB) which controls spindle positioning and distribution of mRNA determinants. The CAB is composed of a mass of cortical endoplasmic reticulum containing mRNAs (the cER-mRNA domain) and an electron dense matrix, but little is known about its precise structure and functions. We have examined the ascidian homologues of PAR proteins, known to regulate polarity in many cell types. We found that aPKC, PAR-6 and PAR-3 proteins, but not their mRNAs, localize to the CAB during the series of asymmetric divisions. Surface particles rich in aPKC concentrate in the CAB at the level of cortical actin microfilaments and form a localized patch sandwiched between the plasma membrane and the cER-mRNA domain. Localization of aPKC to the CAB is dependent on actin but not microtubules. Both the aPKC layer and cER-mRNA domain adhere to cortical fragments prepared from 8-cell stage embryos. Astral microtubules emanating from the proximal centrosome contact the aPKC-rich cortical domain. Our observations indicate that asymmetric division involves the accumulation of the aPKC-PAR-6-PAR-3 complex at the cortical position beneath the pre-existing cER-mRNA domain.

Amino Acid Sequence↗

PubMed2006

Diversity of laminar connections linking periarcuate and lateral intraparietal areas depends on cortical structure.

Lateral prefrontal and intraparietal cortices have strong connectional and functional associations but it is unclear how their common visuomotor, perceptual and working memory functions arise. The hierarchical scheme of cortical processing assumes that prefrontal cortex issues 'feedback' projections to parietal cortex. However, the architectonic heterogeneity of these cortices raises the question of whether distinct areas have laminar-specific interconnections underlying their complex functional relationship. Using quantitative procedures, we showed that laminar-specific connections between distinct prefrontal (areas 46 and 8) and lateral intraparietal (LIPv, LIPd and 7a) areas in Macaca mulatta, studied with neural tracers, varied systematically according to rules determined by the laminar architecture of the linked areas. We found that axons from areas 46 and rostral 8 terminated heavily in layers I-III of all intraparietal areas, as did caudal area 8 to area LIPv, suggesting 'feedback' communication. However, contrary to previous assumptions, axons from caudal area 8 terminated mostly in layers IV-V of LIPd and 7a, suggesting 'feedforward' communication. These laminar patterns of connections were highly correlated with consistent differences in neuronal density between linked areas. When neuronal density in a prefrontal origin was lower than in the intraparietal destination, most terminations were found in layer I with a concomitant decrease in layer IV. The opposite occurred when the prefrontal origin had a higher neuronal density than the target. These findings indicate that the neuronal density of linked areas can reliably predict their laminar connections and may form the basis of understanding the functional complexity of prefrontal-intraparietal interactions in cognition.

Analysis of Variance↗

PubMed2003

Effects of chronic high fat diets on renal function and cortical structure in rats.

Four groups (n = 5) of male Wistar rats were fed with different high-fat diets from 21 days to 18-mo-old: soybean oil (SO), canola oil (CA), lard and egg yolk (LE) or CA+LE. Blood lipids, serum creatinine and proteinuria as well as the cortical stereology were analyzed. The cholesterol, HDL-C and triglycerides were highest in CA group. No significant differences were found among the groups to serum creatinine and proteinuria. The BP was highest in LE group and intermediate in CA+LE group. SO and CA groups showed glomeruli most preserved in number and size. Absolute volume of tubuli was greatest in LE group. Renal cortical interstitium was greatest in SO group and smallest in CA group. Cortical vessels showed smallest indices in LE group and greatest ones in CA group; SO and CA+LE groups were intermediate. Chronic administration of different types of dietetic lipid can significantly alter blood biochemistry, BP and renal cortical structure in rats. Considering these features, canola oil was the more beneficial lipid, while lard and egg yolk mixture was the worst lipid. The addition of canola oil in the LE mixture normally was not efficient to alter the renal damage except in the cortical vessels.

Animals↗