Topological organization of the human brain functional connectome across the lifespan

Human brain function undergoes complex transformations across the lifespan. We employed resting-state functional MRI and graph-theory approaches to systematically chart the lifespan trajectory of the topological organization of human whole-brain functional networks in 126 healthy individuals ranging in age from 7 to 85 years. Brain networks were constructed by computing Pearson's correlations in blood-oxygenation-level-dependent temporal fluctuations among 1024 parcellation units followed by graph-based network analyses. We observed that the human brain functional connectome exhibited highly preserved non-random modular and rich club organization over the entire age range studied. Further quantitative analyses revealed linear decreases in modularity and inverted-U shaped trajectories of local efficiency and rich club architecture. Regionally heterogeneous age effects were mainly located in several hubs (e.g., default network, dorsal attention regions). Finally, we observed inverse trajectories of long- and short-distance functional connections, indicating that the reorganization of connectivity concentrates and distributes the brain's functional networks. Our results demonstrate topological changes in the whole-brain functional connectome across nearly the entire human lifespan, providing insights into the neural substrates underlying individual variations in behavior and cognition. These results have important implications for disease connectomics because they provide a baseline for evaluating network impairments in age-related neuropsychiatric disorders.     

Tracking cerebral white matter changes across the lifespan: insights from diffusion tensor imaging studies

Delineating the normal development of brain white matter (WM) over the human lifespan is crucial to improved understanding of underlying WM pathology in neuropsychiatric and neurological conditions. We review the extant literature concerning diffusion tensor imaging studies of brain WM development in healthy individuals available until October 2012, summarise trends of normal development of human brain WM and suggest possible future research directions. Temporally, brain WM maturation follows a curvilinear pattern with an increase in fractional anisotropy (FA) from newborn to adolescence, decelerating in adulthood till a plateau around mid-adulthood, and a more rapid decrease of FA from old age onwards. Spatially, brain WM tracts develop from central to peripheral regions, with evidence of anterior-to-posterior maturation in commissural and projection fibres. The corpus callosum and fornix develop first and decline earlier, whilst fronto-temporal WM tracts like cingulum and uncinate fasciculus have protracted maturation and decline later. Prefrontal WM is most vulnerable with greater age-related FA reduction compared with posterior WM. Future large scale studies adopting longitudinal design will better clarify human brain WM changes over time.     

Quantitative evaluation of brain development using anatomical MRI and diffusion tensor imaging

The development of the brain is structure-specific, and the growth rate of each structure differs depending on the age of the subject. Magnetic resonance imaging (MRI) is often used to evaluate brain development because of the high spatial resolution and contrast that enable the observation of structure-specific developmental status. Currently, most clinical MRIs are evaluated qualitatively to assist in the clinical decision-making and diagnosis. The clinical MRI report usually does not provide quantitative values that can be used to monitor developmental status. Recently, the importance of image quantification to detect and evaluate mild-to-moderate anatomical abnormalities has been emphasized because these alterations are possibly related to several psychiatric disorders and learning disabilities. In the research arena, structural MRI and diffusion tensor imaging (DTI) have been widely applied to quantify brain development of the pediatric population. To interpret the values from these MR modalities, a “growth percentile chart,” which describes the mean and standard deviation of the normal developmental curve for each anatomical structure, is required. Although efforts have been made to create such a growth percentile chart based on MRI and DTI, one of the greatest challenges is to standardize the anatomical boundaries of the measured anatomical structures. To avoid inter- and intra-reader variability about the anatomical boundary definition, and hence, to increase the precision of quantitative measurements, an automated structure parcellation method, customized for the neonatal and pediatric population, has been developed. This method enables quantification of multiple MR modalities using a common analytic framework. In this paper, the attempt to create an MRI- and a DTI-based growth percentile chart, followed by an application to investigate developmental abnormalities related to cerebral palsy, Williams syndrome, and Rett syndrome, have been introduced. Future directions include multimodal image analysis and personalization for clinical application.     

Regional alterations of brain microstructure in Parkinson's disease using diffusion tensor imaging

This study tested the hypothesis that diffusion tensor imaging can detect alteration in microscopic integrity of white matter and basal ganglia regions known to be involved in Parkinson's disease (PD) pathology. It was also hypothesized that there is an association between diffusion abnormality and PD severity and subtype. Diffusion tensor imaging at 4 Tesla was obtained in 12 PD and 20 control subjects, and measures of fractional anisotropy and mean diffusivity were evaluated using both region‐of‐interest and voxel‐based methods. Movement deficits and subtypes in PD subjects were assessed using the Motor Subscale (Part III) of the Unified Parkinson's Disease Rating Scale. Reduced fractional anisotropy (P < .05, corrected) was found in PD subjects in regions related to the precentral gyrus, substantia nigra, putamen, posterior striatum, frontal lobe, and the supplementary motor areas. Reduced fractional anisotropy in the substantia nigra correlated (P < .05, corrected) with the increased rating scale motor scores. Significant spatial correlations between fractional anisotropy alterations in the putamen and other PD‐affected regions were also found in the context of PD subtypes index analysis. Our data suggest that microstructural alterations detected with diffusion tensor might serve as a potential biomarker for PD. © 2011 Movement Disorder Society     

Diffusion tensor imaging of the corpus callosum: a cross-sectional study across the lifespan

Previous studies have demonstrated strong developmental trends of white matter using in vivo neuroimaging. However, few studies have examined white matter using diffusion tensor imaging across the lifespan. In the present study we examined fractional anisotropy and volume in the corpus callosum in four groups (children, adolescents, young adults, and elderly). Results revealed a curvilinear relationship in the analysis of the fractional anisotropy values for these four groups, with fractional anisotropy values increasing in childhood and adolescence, reaching their peak in young adulthood, followed by a non-significant decline in the elderly. Volumetric analysis of corpus callosum regions revealed a similar pattern, with an increase in volume from childhood and adolescence through young adulthood, and a non-significant decrease in volume in the elderly group. These results define the microstructural development of the white matter across the lifespan. Future studies are required to examine the neurobehavioral correlates of these neuroimaging indices.     

A diffusion tensor magnetic resonance imaging study of brain tissue from patients with migraine

OBJECTIVE: To measure in vivo, using diffusion tensor magnetic resonance imaging (DT-MRI) the extent of pathological damage of normal appearing brain tissue (NABT) from patients with migraine. METHODS: Dual echo and DT-MRI scans of the brain were acquired from 34 patients with migraine and 17 sex and age matched healthy volunteers. Mean diffusivity (MD) and fractional anisotropy (FA) histograms of the NABT were obtained from all subjects and the histograms' peak heights and average NABT MD and FA measured. When present, average MD and FA values of T2 visible lesions were also measured. RESULTS: In comparison with healthy volunteers, patients with migraine had lower MD histogram peak height (p=0.02) of the NABT. No differences were found in FA histogram derived metrics between migraine patients and healthy subjects. No difference was found for any MD and FA histogram derived metrics between migraine patients with and without brain MRI lesions, and between patients with and without aura. CONCLUSIONS: This study shows that, although brain damage may extend beyond T2 weighted abnormalities in patients with migraine, the severity of these "occult" changes is mild compared with that found in other diseases associated with white matter abnormality.     

High-field diffusion tensor imaging of mouse brain in vivo using single-shot STEAM MRI

Information about the microstructural organization of cerebral white matter that is accessible by magnetic resonance diffusion tensor imaging (DTI) gains increasing importance for studies of animal brain. Particular challenges occur for in vivo conditions as well as at high magnetic fields. Here, we have employed a diffusion-weighted (DW) single-shot STEAM MRI sequence for DTI of mouse brain in vivo at 7 T. The approach exploits the increased longitudinal magnetization and prolonged T1 relaxation times of water protons at higher magnetic field strengths without suffering from susceptibility-induced artifacts. When compared to studies at 2.35 T, half Fourier DW STEAM MRI at 7 T yielded a substantial gain in signal-to-noise ratio (SNR) that could be invested either in a reduction of the measurement time or an increase of the spatial resolution. Thus, for a measurement time of 3h, DTI with a voxel size of 117 microm x 117 microm x 720 microm not only resulted in high-quality maps of the fractional anisotropy and main diffusion direction (MDD), but also allowed for fiber tracking of major mouse brain structures in vivo.     

Visualizing white matter pathways in the living human brain: diffusion tensor imaging and beyond

Biologic connectionism holds as its central tenet that the cognitive, behavioral, and motor functions of the brain are derived from the complex interconnections of simple neural processing units. Much can be learned about the human mind through the study of the brain's connections in normal and diseased states. This article summarizes the essential features of the tensor model of diffusion, outlines newer approaches to overcoming the limitations of the tensor, and provides normal and clinical examples of white matter anatomy derived using diffusion tensor imaging and more sophisticated high angular resolution diffusion imaging methods. Diffusion MR imaging is a powerful adjunct to techniques for studying brain function.     

Age-related degeneration of the fornix in the human brain: a diffusion tensor imaging study

As a part of the Papez circuit, the fornix carries information on episodic memory. Several diffusion tensor imaging (DTI) studies have reported on changes in the fornix that occur with aging; however, these studies have been controversial. Using DTI, we attempted to investigate age-related changes of the fornix in the human brain. Sixty subjects (30 males, 30 females; mean age, 49.2 years; range, 20-78 years) were recruited. We categorized subjects into three groups, including young (20-39 years), middle-aged (40-59 years), and older (60-79 years) adults. DTIs were acquired using a sensitivity-encoding head coil on a 1.5 T. We divided the whole fornix into three parts (column, body, and crus) and constructed tractography for each part. We measured fractional anisotropy (FA), apparent diffusion coefficient (ADC), and tract number for each part of the fornix. In all three parts of the fornix, the FA value and tract number decreased, whereas ADC value increased with aging. In addition, a linear regression model was fitted to all three DTI parameters in each part of the fornix. Degenerative change of the fornix in the human brain appears to have occurred at a near constant rate from the 20s to the30s throughout the lifespan.     

人脑皮质脊髓束的年龄相关变化

We don't have Chinese abstract. However, If you need abstract in Chinese. I'll make the abstract in chinese and attach it     

功能磁共振和弥散张量纤维束成像中的人脑皮质桥小脑束

The anatomical organization of the corticopontocerebellar tract(CPCT) in the human brain remains poorly understood.The present study investigated probabilistic tractography of the CPCT in the human brain using diffusion tensor tractography with functional magnetic resonance imaging.CPCT data was obtained from 14 healthy subjects.CPCT images were obtained from functional magnetic resonance imaging and diffusion tensor tractography,revealing that the CPCT originated from the primary sensorimotor cortex and descended to the pontine nucleus through the corona radiata,the posterior limb of the internal capsule,and the cerebral peduncle.After crossing the pons through the transverse pontine fibers,the CPCT entered the cerebellum via the middle cerebral peduncle.However,some variation was detected in the midbrain(middle cerebral peduncle and/or medial lemniscus) and pons(ventral and/or dorsal transverse pontine fibers).The CPCT was analyzed in 3 dimensions from the cerebral cortex to the cerebellum.These results could be informative for future studies of motor control in the human brain.     

精神分裂症患者全脑白质纤维弥散张量成像的初步研究

目的运用能够提示白质纤维(white matter,WM)完整性的弥散张量成像(diffusion tensor imaging,DTI)技术,探讨精神分裂症患者全脑白质纤维是否受到损害。方法对21例精神分裂症患者(患者组)和21名健康人(对照组)进行全脑DTI扫描,用SPM2(Statistical Parametric Maps,SPM)软件对图像进行处理,采用以像素为基础的分析方法(voxel-based analysis,VBA)对两组的分数各向异性(fractional anisotropy,FA)值进行组间比较。结果患者组下列脑区的FA值显著低于对照组(P<0·001):左侧额眶区和右侧额中回的白质、双侧颞下回白质、双侧顶叶内侧白质、右侧前扣带、双侧海马、双侧大脑脚、双侧岛叶、右侧放射冠和右侧小脑上脚。结论精神分裂症多个部位脑白质纤维的完整性受到破坏。     

苯丙胺类物质依赖的脑弥散张量成像研究

目的 探讨苯丙胺类物质对脑白质结构的影响.方法 对11例苯丙胺类物质依赖者和6名正常对照进行磁共振弥散张量成像(diffusion tensor imaging,DTI)扫描及脑白质纤维束重建,比较两组的差异;同时分析有精神症状的苯丙胺类物质依赖者(n=7)与正常对照的DTI结果差异.结果 苯丙胺物质依赖组左右两侧皮质脊髓束数量均低于对照组(t=1.25,P<0.01;t=0.04,P=0.03),左侧扣带束FA值高于右侧(t=4.04,P<0.01)且与物质使用时间呈正相关(r=0.69,P<0.01);有精神症状的苯丙胺类物质依赖组左侧皮质脊髓束ADC值高于对照组(t=3.54,P=O.04)、扣带束ADC值左侧小于右侧(t=-2.62,P=0.04);有精神症状的苯丙胺物质依赖组DTI值与阳性和阴性症状量表各因子分无明显相关(P>0.05).结论 苯丙胺类物质依赖者大脑双侧皮质脊髓束及左扣带束受损.且左扣带束纤维受损随物质使用时间延长而加重;未见苯丙胺物质依赖者的精神症状与DTI值相关,但需要进一步证实.     

Three-dimensional high-resolution diffusion tensor imaging and tractography of the developing rabbit brain

Diffusion tensor imaging (DTI) is sensitive to structural ordering in brain tissue particularly in the white matter tracts. Diffusion anisotropy changes with disease and also with neural development. We used high-resolution DTI of fixed rabbit brains to study developmental changes in regional diffusion anisotropy and white matter fiber tract development. Imaging was performed on a 4.7-tesla Bruker Biospec Avance scanner using custom-built solenoid coils and DTI was performed at various postnatal ages. Trace apparent diffusion coefficient, fractional diffusion anisotropy maps and fiber tracts were generated and compared across the ages. The brain was highly anisotropic at birth and white matter anisotropy increased with age. Regional DTI tractography of the internal capsule showed refinement in regional tract architecture with maturation. Interestingly, brains with congenital deficiencies of the callosal commissure showed selectively strikingly different fiber architecture compared to age-matched brains. There was also some evidence of subcortical to cortical fiber connectivity. DTI tractography of the anterior and posterior limbs of the internal capsule showed reproducibly coherent fiber tracts corresponding to known corticospinal and corticobulbar tract anatomy. There was some minor interanimal tract variability, but there was remarkable similarity between the tracts in all animals. Therefore, ex vivo DTI tractography is a potentially powerful tool for neuroscience investigations and may also reveal effects (such as fiber tract pruning during development) which may be important targets for in vivo human studies.     

应用弥散张量成像实现神经纤维追踪的方法*☆

背景：目前的神经纤维追踪方法众说纷纭,不同的追踪方法往往对数据的要求比较严格,格式比较单一,并且在特定的条件下,才能进行纤维追踪,但都没有统一可执行标准。因此需要研究一种简便通用的神经纤维追踪处理方法。 目的：提出一种简便通用,并且可以在不同的数据采集方法情况下,转变为固定的数据采集格式的弥散张量神经纤维追踪方法。 方法：首先采用MRIcro软件在原始DTI图像上,找出梯度因子b值,组成梯度方向文件并把DICOM原始文件软件转换成Analyze格式文件,然后利用SPM软件对格式文件标准化,最后采用DTI-track软件进行神经纤维追踪处理。 结果与结论：通过对DTI图像进行处理,证明该方法能有效的得出扩散梯度因子b值文件,并且能把不同的DTI数据转变为统一的格式进行DTI处理,得到预期的DTI纤维追踪图像,为DTI研究提供了一个简便有效的具体实现方法。 关键词：弥散张量成像;纤维追踪;扩散梯度因子;神经纤维;功能磁共振     

Model-based variational smoothing and segmentation for diffusion tensor imaging in the brain

This article applies a unified approach to variational smoothing and segmentation to brain diffusion tensor image data along user-selected attributes derived from the tensor, with the aim of extracting detailed brain structure information. The application of this framework simultaneously segments and denoises to produce edges and smoothed regions within the white matter of the brain that are relatively homogeneous with respect to the diffusion tensor attributes of choice. This approach enables the visualization of a smoothed, scale invariant representation of the tensor data field in a variety of diverse forms. In addition to known attributes such as fractional anisotropy, these representations include selected directional tensor components and additionally associated continuous valued edge fields that might be used for further segmentation. A comparison is presented of the results of three different data model selections with respect to their ability to resolve white matter structure. The resulting images are integrated to provide better perspective of the model properties (edges, smoothed image, and so forth) and their relationship to the underlying brain anatomy. The improvement in brain image quality is illustrated both qualitatively and quantitatively, and the robust performance of the algorithm in the presence of added noise is shown. Smoothing occurs without loss of edge features because of the simultaneous segmentation aspect of the variational approach, and the output enables better delineation of tensors representative of local and long-range association, projection, and commissural fiber systems.     

Detection of Alzheimer's Disease using cortical diffusion tensor imaging

The aim of this research was to test a novel in‐vivo brain MRI analysis method that could be used in clinical cohorts to investigate cortical architecture changes in patients with Alzheimer''s Disease (AD). Three cohorts of patients with probable AD and healthy volunteers were used to assess the results of the method. The first group was used as the “Discovery” cohort, the second as the “Test” cohort and the last “ATN” (Amyloid, Tau, Neurodegeneration) cohort was used to test the method in an ADNI 3 cohort, comparing to amyloid and Tau PET. The method can detect altered quality of cortical grey matter in AD patients, providing an additional tool to assess AD, distinguishing between these and healthy controls with an accuracy range between good and excellent. These new measurements could be used within the “ATN” framework as an index of cortical microstructure quality and a marker of Neurodegeneration. Further development may aid diagnosis, patient selection, and quantification of the “Neurodegeneration” component in response to therapies in clinical trials.     

Effects of cardiac pulsation in diffusion tensor imaging of the rat brain

The purpose of this study was to investigate the effects of cardiac pulsation in diffusion tensor imaging (DTI) of the rat brain. DTI data were acquired either with or without different cardiac gating delays. For each case, two sets of identical DTI data were acquired for a bootstrap analysis to measure the uncertainty in estimating mean diffusivity (MD), fractional anisotropy (FA) and the primary eigenvector direction. The 95% confidence interval of the primary eigenvectors was substantially reduced (21-25%) when cardiac gating with triggering delay of 70 ms (～half of R-R peak duration) was used in comparison to studies without gating or when gating with a triggering delay of 0 ms was used. Standard deviations of MD and FA estimates were also reduced by 12-26% and 13-24%, respectively. For voxels with mean FA values larger than 0.15 and smaller than 0.95, the decrease in CI and standard deviations of MD and FA by cardiac gating with triggering delay of 70 ms were significant (p < 0.05). These results demonstrate the importance of cardiac gating in acquisition of in vivo high resolution DTI data.     

Associations of subclinical autistic-like traits with brain structural variation using diffusion tensor imaging and voxel-based morphometry

BackgroundPrevious case–control studies of autistic spectrum disorder (ASD) have identified altered brain structure such as altered frontal and temporal cortex volumes, or decreased fractional anisotropy (FA) within the inferior fronto-occipital fasciculus in patients. It remains unclear whether subclinical autistic-like traits might also be related to variation in these brain structures.MethodsIn this study, we analyzed magnetic resonance imaging (MRI) data of 250 psychiatrically healthy subjects phenotyped for subclinical autistic-like traits using the Autism Spectrum Quotient (AQ). For data analysis, we used voxel-based morphometry of T1-MRIs (Computational Anatomy Toolbox) and tract-based spatial statistics for diffusion tensor imaging data.Results AQ attention switching subscale correlated negatively with FA values in the bilateral uncinate fasciculus as well as the bilateral inferior fronto-occipital fasciculus. Higher AQ attention switching subscale scores were associated with increased mean diffusivity and radial diffusivity values in the uncinate fasciculus, while axial diffusivity values within this tract show a negative correlation. AQ attention to detail subscale correlated positively with gray matter volume in the right pre- and postcentral gyrus.ConclusionsWe demonstrate that individuals with higher levels of autism-spectrum-like features show decreased white matter integrity in tracts associated with higher-level visual processing and increased cortical volume in areas linked to movement sequencing and working memory. Our results resemble regional brain structure alterations found in individuals with ASD. This offers opportunities to further understand the etiology and pathogenesis of the disorder and shows a subclinical continuum perspective.