Haibao Wang

Contribution of the hemodynamics of A1 dysplasia or hypoplasia to anterior communicating artery aneurysms: a 3-dimensional numerical simulation study.

Objective To explore the association between the hemodynamics and formation, growth, and rupture of aneurysms in anterior communicating arteries (ACoA) with A1 dysplasia or hypoplasia. Methods A series of 3-dimensional numerical simulation models of the anterior communicating artery complex (ACoAC) were designed geometrically. The diameter of A1 was fixed on one side and decreased gradually on the other side. Three groups of ACoA aneurysm model growth were constructed with different positions to the dominant bifurcation. Blood flow was modeled as an incompressible Newtonian fluid described by the unsteady Navier-Stokes equations. Vessel walls were assumed to be rigid; no slip boundary conditions were applied at the walls. Results Wall shear stress (WSS), flow velocity, and pressure were influenced by the dynamic variations of A1 diameter. When the diameter of the nondominant A1 gradually decreased, WSS and flow velocity dynamically increased in the dominant bifurcation and pressure decreased. Wall shear stress differences were significant between the dominant and nondominant bifurcations (t = 6.543; P < 0.05). With aneurysm growth, WSS and flow velocity gradually decreased, and turbulence appeared. Wall shear stress was lower at the bifurcation than that 0.02 mm and 0.1 mm to the bifurcation, whereas flow velocity and turbulent flow were more obvious. Conclusions A1 dysplasia/hypoplasia is a potential risk factor in the formation of ACoA aneurysms. Wall shear stress increase may contribute to aneurysm formation. Wall shear stress decrease and turbulent flow may be responsible for the growth and rupture of ACoA aneurysms. The hemodynamic mechanism in the growth and rupture of aneurysms in different locations might be different.

Circulating endothelial progenitor cells are involved in VEGFR-2-related endothelial differentiation in glioma

Endothelial progenitor cells (EPCs) play important roles in maintaining endothelial integrity and tumor vascularization. However, the differentiation of EPCs in the neoangiogenesis of gliomas has not yet been fully elucidated. The purpose in this study was to investigate the profile of EPC differentiation in rat C6 glioma using magnetic resonance imaging (MRI), a non-invasive monitoring assay. To achieve this goal, we isolated EPCs from rat bone marrow and identified them by detecting CD34, CD133, and VEGFR-2, the markers of EPCs. Coexpression of Ac-LDL and UEA-1 in EPCs was also determined. To dynamically monitor the migration of circulating cells, the EPCs were labeled with ultrasmall superparamagnetic iron oxidexa0(USPIO) and injected by tail vein into rats bearing C6 glioma. MRI was performed at 24, 48, and 96xa0h after injection. The distribution and differentiation of EPCs were confirmed by histology. We found that the USPIO-labeled EPCs appeared at the tumor periphery where a large number of CD105-positive cells appeared at 24xa0h after injection by using MRI scanning. Ninety-six hours after injection, immunohistochemistry and Prussian blue staining were used to observe the labeled EPCs in the tumor tissue. We found that many of the labeled EPCs were overlapped with VEGFR-2-positive endothelial cells, but not CD105- or CD34-positive cells. These results suggest that EPCs can cross the blood-brain barrier from peripheral blood and home to tumors, where they differentiate into endothelial cells, including VEGFR-2-positive endothelial cells. MRI is a useful method for dynamically tracking the migration of USPIO-labeled EPCs.

Aberrant Functional Connectivity and Structural Atrophy in Subcortical Vascular Cognitive Impairment: Relationship with Cognitive Impairments

Abnormal structures in the cortical and subcortical regions have been identified in subcortical vascular cognition impairment (SVCI). However, little is known about the functional alterations in SVCI, and no study refers to the functional connectivity in the prefrontal and subcortical regions in this context. The medial prefrontal cortex (MPFC) is an important region of the executive network and default mode network, and the subcortical thalamus plays vital roles in mediating or modulating these two networks. To investigate both thalamus- and MPFC-related functional connectivity as well as its relationship with cognition in SVCI, 32 SVCI patients and 23 control individuals were administered neuropsychological assessments. They also underwent structural and functional magnetic resonance imaging scans. Voxel-based morphometry and functional connectivity analysis were performed to detect gray matter (GM) atrophy and to characterize the functional alterations in the thalamus and the MPFC. For structural data, we observed that GM atrophy was distributed in both cortical regions and subcortical areas. For functional data, we observed that the thalamus functional connectivity in SVCI was significantly decreased in several cortical regions [i.e., the orbitofrontal lobe (OFL)], which are mainly involved in executive function and memory function. However, connectivity was increased in several frontal regions (i.e., the inferior frontal gyrus), which may be induced by the compensatory recruitment of the decreased functional connectivity. The MPFC functional connectivity was also decreased in executive- and memory-related regions (i.e., the anterior cingulate cortex) along with a motor region (i.e., the supplementary motor area). In addition, the cognitive performance was closely correlated with functional connectivity between the left thalamus and the left OFL in SVCI. The present study, thus, provides evidence for an association between structural and functional alterations, and sheds light on the underlying neural mechanisms of executive dysfunction in SVCI.

Small-World Brain Network and Dynamic Functional Distribution in Patients with Subcortical Vascular Cognitive Impairment

To investigate the topological properties of the functional connectivity and their relationships with cognition impairment in subcortical vascular cognitive impairment (SVCI) patients, resting-state fMRI and graph theory approaches were employed in 23 SVCI patients and 20 healthy controls. Functional connectivity between 90 brain regions was estimated using bivariate correlation analysis and thresholded to construct a set of undirected graphs. Moreover, all of them were subjected to a battery of cognitive assessment, and the correlations between graph metrics and cognitive performance were further analyzed. Our results are as follows: functional brain networks of both SVCI patients and controls showed small-world attributes over a range of thresholds(0.15≤sparsity≤0.40). However, global topological organization of the functional brain networks in SVCI was significantly disrupted, as indicated by reduced global and local efficiency, clustering coefficients and increased characteristic path lengths relative to normal subjects. The decreased activity areas in SVCI predominantly targeted in the frontal-temporal lobes, while subcortical regions showed increased topological properties, which are suspected to compensate for the inefficiency of the functional network. We also demonstrated that altered brain network properties in SVCI are closely correlated with general cognitive and praxis dysfunction. The disruption of whole-brain topological organization of the functional connectome provides insight into the functional changes in the human brain in SVCI.

Relationship between cerebellar structure and emotional memory in depression

A few studies have been conducted on the relationship between cerebellar volume and emotional memory or clinical severity in major depressive disorder (MDD). In this study, we aimed to compare the volume and density of the cerebellar gray matter (GM) in patients with MDD and in healthy controls (HCs) and explore the association between these cerebellar parameters and measurements of emotional memory and clinical severity.

Impaired White Matter Connections of the Limbic System Networks Associated with Impaired Emotional Memory in Alzheimer's Disease

Background: Discrepancies persist regarding retainment of emotional enhancement of memory (EEM) in mild cognitive impairment (MCI) and early Alzheimers disease (AD) patients.In addition, the neural mechanisms are still poorly understood, little is known about emotional memory related changes in white matter (WM). Objective: To observe whether EEM is absent in amnestic MCI (aMCI) and AD patients, and to investigate if emotional memory is associated with WM connections and gray matters (GM) of the limbic system networks. Methods: Twenty-one AD patients, 20 aMCI patients and 25 normal controls participated in emotional picture recognition tests and MRI scanning. Tract-based spatial statistics (TBSS) and voxel-based morphometry (VBM) methods were used to determine white and gray matter changes of patients. Fourteen regions of interest (ROI) of WM and 20 ROIs of GM were then selected for the correlation analyses with behavioral scores. Results: The EEM effect was lost in AD patients. Both white and gray matter of the limbic system networks were impaired in AD patients. Significant correlations or tendencies between the bilateral uncinate fasciculus, corpus callosum (genu and body), left cingulum bundle, left parahippocampal WM and the recognition sensitivity of emotional valence pictures, and significant correlations or tendencies between the splenium of corpus callosum, left cingulum bundle, left crus of fornix and stria terminalis and the recognition sensitivity of EEM were found. The volume of left amygdala, bilateral insula, medial frontal lobe, anterior and middle cingulum gyrus were positively correlated with the recognition sensitivity of emotional photos, and the right precuneus was positively correlated with the negative EEM effect. However, the affected brain areas of aMCI patients were more localized, and aMCI patients benefited only from positive stimuli. Conclusion: There are impairments of the limbic system networks of AD patients. Damaged WM connections and GM volumes of those networks are associated with impaired emotional memory and EEM effect in AD patients.

Disrupted topological organization of the motor execution network in alcohol dependence

Motor function damage is one of the most common symptoms in patients with alcohol dependence (AD). However, relatively little is known about the neuropathology of the motor impairments in AD. The aim of this study was to identify changes in the topological organization of the motor execution network in AD. Here, a total of 39 male individuals, including 19 AD patients and 20 age-matched healthy controls, underwent resting-state functional magnetic resonance imaging (fMRI). The motor execution network was constructed and analyzed using graph theoretical approaches. Topological properties (including global, nodal and edge measures) were compared between the two groups. At the global level, AD patients exhibited increased local specialization (indexed by increased clustering coefficient and local efficiency) relative to healthy controls, indicating that the motor execution network of AD patients shifts toward regularization. At the node level, nodal degree was higher in AD patients in the cerebellum. At the edge level, we observed a cerebello-thalamo-striato-cortical circuit with altered functional connectivity strength in AD patients. These findings suggest that topological architecture of the motor execution network is disrupted in AD patients, which may provide important insights into the neurobiology of the AD-related motor impairments.

Effect of emotional enhancement of memory on recollection process in young adults: the influence factors and neural mechanisms

Emotional enhancement of memory (EEM) is thought to modulate memory recollection rather than familiarity. However, the contributing factors and neural mechanisms are not well understood. To address these issues, we investigated how valence, arousal, and the amount of devoted attention influence the EEM effect on recollection. We also compared the topological properties among hippocampus- and perirhinal and entorhinal cortex-mediated emotional memory processing networks. Finally, we evaluated the correlations between emotional memory/EEM and inherent properties (i.e., amplitude of low-frequency fluctuation and node degree, efficiency, and betweenness) of the hippocampus and perirhinal and entorhinal cortices in 59 healthy young adults by resting-state functional magnetic resonance imaging. EEM was elicited by incidental encoding, negative images, and positive high-arousal images. The hippocampus was correlated with recollection sensitivity and EEM negative-high-arousal . The emotional memory processing network mediated by the hippocampus had higher clustering coefficient, local efficiency, and normalized characteristic path length but lower normalized global efficiency than those mediated by the perirhinal and entorhinal cortices. The entorhinal cortex was associated with both recollection and familiarity sensitivity, but showed different correlation patterns. The perirhinal cortex was highly correlated with familiarity sensitivity of negative low-arousal stimuli. These results demonstrate that the EEM effect on memory recollection is influenced by valence, stimulus arousal, and amount of attention involved during encoding. Moreover, the hippocampus and perirhinal and entorhinal cortices play distinct roles in the recollection and familiarity of emotional memory and the EEM effect.

Resting-state functional connectivity of the dorsal frontal cortex predicts subcortical vascular cognition impairment

Functional magnetic resonance imaging (fMRI) studies have revealed group differences in the frontal area between the subcortical vascular cognition impairment (SVCI) patients and the controls. However, most of the existing research focused on average differences between the two groups, and therefore had limited clinical applicability. The aim of our study was to investigate whether inter-regions functional connectivity of the dorsal frontal cortex (DFC) can be used to discriminate the SVCI from the controls at the level of the individual. Thirty-two SVCI patients and 32 demographically similar healthy individuals underwent resting-state functional magnetic resonance imaging. The DFC, derived from a prior atlas, was divided into 10 clusters. Features based on DFC were obtained through functional connectivity analysis between pairs of DFC. A nonlinear kernel support vector machine was used for classification and validated using 8-fold cross validation. An excellent classification accuracy was obtained from both the left and the right DFC functional connectivity (accuracy=75.07%, sensitivity=81.57% and specificity=61.71%; accuracy=45.38%, sensitivity=60.74% and specificity=39.48%; P<0.001). These findings shed further light on the pathogenesis of SVCI and showed promising classification performance using machine learning analysis based on DFC fMRI data, which may be useful for the differentiation of SVCI.

Computed Tomography and Magnetic Resonance Imaging Characteristics of Peripheral Primitive Neuroectodermal Tumor: A Retrospective Analysis of 16 Cases

Purpose The aim of this study was to analyze the radiological features of peripheral primitive neuroectodermal tumor (pPNET). Materials and Methods The radiological and clinical findings for 16 patients with pPNETs were retrospectively reviewed. The 16 tumors were classified into 4 groups (meninges group, n = 4; spine group, n = 3; bone group, n = 5; soft-tissue group, n = 4), and clinical data, size, and common and unique CT/MRI characteristics were assessed. Results Peripheral primitive neuroectodermal tumors presented as large solid masses with aggressive extension into the neighboring tissue. Most tumors (11/16) presented with necrosis, and 5 of the 16 cases showed signs of hemorrhage. The “dural tail sign” was observed in the meninges and spine groups. The pPNETs of bone demonstrated bony destruction with spiculated periosteal reaction, and small nourishing vessels were found in tumors in the soft-tissue group. Conclusions Peripheral primitive neuroectodermal tumor should be suggested as an important differential diagnosis when the tumor presents as a large, ill-defined solid mass with aggressive extension and significant enhancement.