您现在的位置:首页>美国卫生研究院文献>Brain Connectivity

期刊信息

  • 期刊名称:

    -

  • 刊频: Bimonthly
  • NLM标题:
  • iso缩写: -
  • ISSN: -

年度选择

更多>>

  • 排序:
  • 显示:
  • 每页:
全选(0
<13/16>
308条结果
  • 机译 视觉搜索过程中的额枕连接
    摘要:Although expectation- and attention-related interactions between ventral and medial prefrontal cortex and stimulus category-selective visual regions have been identified during visual detection and discrimination, it is not known if similar neural mechanisms apply to other tasks such as visual search. The current work tested the hypothesis that high-level frontal regions, previously implicated in expectation and visual imagery of object categories, interact with visual regions associated with object recognition during visual search. Using functional magnetic resonance imaging, subjects searched for a specific object that varied in size and location within a complex natural scene. A model-free, spatial-independent component analysis isolated multiple task-related components, one of which included visual cortex, as well as a cluster within ventromedial prefrontal cortex (vmPFC), consistent with the engagement of both top-down and bottom-up processes. Analyses of psychophysiological interactions showed increased functional connectivity between vmPFC and object-sensitive lateral occipital cortex (LOC), and results from dynamic causal modeling and Bayesian Model Selection suggested bidirectional connections between vmPFC and LOC that were positively modulated by the task. Using image-guided diffusion-tensor imaging, functionally seeded, probabilistic white-matter tracts between vmPFC and LOC, which presumably underlie this effective interconnectivity, were also observed. These connectivity findings extend previous models of visual search processes to include specific frontal–occipital neuronal interactions during a natural and complex search task.
  • 机译 脊柱裂的半球有效和功能性皮层连通性特征与os异常一致
    摘要:The impact of the posterior callosal anomalies associated with spina bifida on interhemispheric cortical connectivity is studied using a method for estimating cortical multivariable autoregressive models from scalp magnetoencephalography data. Interhemispheric effective and functional connectivity, measured using conditional Granger causality and coherence, respectively, is determined for the anterior and posterior cortical regions in a population of five spina bifida and five control subjects during a resting eyes-closed state. The estimated connectivity is shown to be consistent over the randomly selected subsets of the data for each subject. The posterior interhemispheric effective and functional connectivity and cortical power are significantly lower in the spina bifida group, a result that is consistent with posterior callosal anomalies. The anterior interhemispheric effective and functional connectivity are elevated in the spina bifida group, a result that may reflect compensatory mechanisms. In contrast, the intrahemispheric effective connectivity is comparable in the two groups. The differences between the spina bifida and control groups are most significant in the θ and α bands.
  • 机译 功能磁共振成像相位同步作为动态功能连接的一种量度
    摘要:Functional brain activity and connectivity have been studied by calculating intersubject and seed-based correlations of hemodynamic data acquired with functional magnetic resonance imaging (fMRI). To inspect temporal dynamics, these correlation measures have been calculated over sliding time windows with necessary restrictions on the length of the temporal window that compromises the temporal resolution. Here, we show that it is possible to increase temporal resolution by using instantaneous phase synchronization (PS) as a measure of dynamic (time-varying) functional connectivity. We applied PS on an fMRI dataset obtained while 12 healthy volunteers watched a feature film. Narrow frequency band (0.04–0.07 Hz) was used in the PS analysis to avoid artifactual results. We defined three metrics for computing time-varying functional connectivity and time-varying intersubject reliability based on estimation of instantaneous PS across the subjects: (1) seed-based PS, (2) intersubject PS, and (3) intersubject seed-based PS. Our findings show that these PS-based metrics yield results consistent with both seed-based correlation and intersubject correlation methods when inspected over the whole time series, but provide an important advantage of maximal single-TR temporal resolution. These metrics can be applied both in studies with complex naturalistic stimuli (e.g., watching a movie or listening to music in the MRI scanner) and more controlled (e.g., event-related or blocked design) paradigms. A MATLAB toolbox FUNPSY () is openly available for using these metrics in fMRI data analysis.
  • 机译 基于高角度分辨率扩散成像的集成框架-基于结构连通性的研究
    摘要:Structural connectivity models hold great promise for expanding what is known about the ways information travels throughout the brain. The physiologic interpretability of structural connectivity models depends heavily on how the connections between regions are quantified. This article presents an integrated structural connectivity framework designed around such an interpretation. The framework provides three measures to characterize the structural connectivity of a subject: (1) the structural connectivity matrix describing the proportion of connections between pairs of nodes, (2) the nodal connection distribution (nCD) characterizing the proportion of connections that terminate in each node, and (3) the connection density image, which presents the density of connections as they traverse through white matter (WM). Individually, each possesses different information concerning the structural connectivity of the individual and could potentially be useful for a variety of tasks, ranging from characterizing and localizing group differences to identifying novel parcellations of the cortex. The efficiency of the proposed framework allows the determination of large structural connectivity networks, consisting of many small nodal regions, providing a more detailed description of a subject's connectivity. The nCD provides a gray matter contrast that can potentially aid in investigating local cytoarchitecture and connectivity. Similarly, the connection density images offer insight into the WM pathways, potentially identifying focal differences that affect a number of pathways. The reliability of these measures was established through a test/retest paradigm performed on nine subjects, while the utility of the method was evaluated through its applications to 20 diffusion datasets acquired from typically developing adolescents.
  • 机译 通过脑电图,功能磁共振成像和弥散张量成像将不同时间范围内的大脑连通性联系起来
    摘要:Structural and functional connectivity are intrinsic properties of the human brain and represent the amount of cognitive capacities of individual subjects. These connections are modulated due to development, learning, and disease. Momentary adaptations in functional connectivity alter the structural connections, which in turn affect the functional connectivity. Thus, structural and functional connectivity interact on a broad timescale. In this study, we aimed to explore distinct measures of connectivity assessed by functional magnetic resonance imaging and diffusion tensor imaging and their association to the dominant electroencephalogram oscillatory property at rest: the individual alpha frequency (IAF). We found that in 21 healthy young subjects, small intraindividual temporal IAF fluctuations were correlated to increased blood oxygenation level-dependent signal in brain areas associated to working memory functions and to the modulation of attention. These areas colocalized with functionally connected networks supporting the respective functions. Furthermore, subjects with higher IAF show increased fractional anisotropy values in fascicles connecting the above-mentioned areas and networks. Hence, due to a multimodal approach a consistent functionally and structurally connected network related to IAF was observed.
  • 机译 麻烦之处:全局信号回归后,相关模式和组差异如何失真
    摘要:Resting-state functional magnetic resonance imaging (RS-FMRI) holds the promise of revealing brain functional connectivity without requiring specific tasks targeting particular brain systems. RS-FMRI is being used to find differences between populations even when a specific candidate target for traditional inferences is lacking. However, the problem with RS-FMRI is a lacking definition of what constitutes noise and signal. RS-FMRI is easy to acquire but is not easy to analyze or draw inferences from. In this commentary we discuss a problem that is still treated lightly despite its significant impact on RS-FMRI inferences; global signal regression (GSReg), the practice of projecting out signal averaged over the entire brain, can change resting-state correlations in ways that dramatically alter correlation patterns and hence conclusions about brain functional connectedness. Although Murphy et al. in 2009 demonstrated that GSReg negatively biases correlations, the approach remains in wide use. We revisit this issue to argue the problem that GSReg is more than negative bias or the interpretability of negative correlations. Its usage can fundamentally alter interregional correlations within a group, or their differences between groups. We used an illustrative model to clearly convey our objections and derived equations formalizing our conclusions. We hope this creates a clear context in which counterarguments can be made. We conclude that GSReg should not be used when studying RS-FMRI because GSReg biases correlations differently in different regions depending on the underlying true interregional correlation structure. GSReg can alter local and long-range correlations, potentially spreading underlying group differences to regions that may never have had any. Conclusions also apply to substitutions of GSReg for denoising with decompositions of signals aggregated over the network's regions to the extent they cannot separate signals of interest from noise. We touch on the need for careful accounting of nuisance parameters when making group comparisons of correlation maps.
  • 机译 儿童叙事理解的大脑连接网络的光谱图形模型方法
    摘要:Narrative comprehension is a fundamental cognitive skill that involves the coordination of different functional brain regions. We develop a spectral graphical model with model averaging to study the connectivity networks underlying these brain regions using fMRI data collected from a story comprehension task. Based on the spectral density matrices in the frequency domain, this model captures the temporal dependency of the entire fMRI time series between brain regions. A Bayesian model averaging procedure is then applied to select the best directional links that constitute the brain network. Using this model, brain networks of three distinct age groups are constructed to assess the dynamic change of network connectivity with respect to age.
  • 机译 低至中等组织的精神分裂症的弥散异常
    摘要:Increasing evidence suggests that abnormal white matter is central to the pathophysiology and, potentially, the pathogenesis of schizophrenia (SCZ). The spatial distribution of observed abnormalities and the type of white matter involved remain to be elucidated. Seventeen chronically ill individuals with SCZ and 17 age- and gender-matched controls were studied using a 3T magnetic resonance imaging diffusion tensor imaging protocol designed to examine the abnormalities of white matter by region and by level of architectural infrastructure as assessed by fractional anisotropy (FA) in native space. After assessing whole-brain FA, FA was divided into quartiles, capturing all brain regions with FA values from 0 to 0.25, 0.25 to 0.5, 0.5 to 0.75, and 0.75 to 1.0. Mean whole-brain FA was 4.6% smaller in the SCZ group than in healthy controls. This difference was largely accounted for by FA values from the second quartile (between 0.25 and 0.5). Second quartile FA was decreased in all 130 brain regions of the template in the SCZ group, with the difference reaching statistical significance in 41 regions. Correspondingly, the amount of brain tissue with an FA of ∼0.4 was significantly reduced in the SCZ group, while the amount of brain tissue falling in the lowest quartile of FA was increased. These findings strongly imply a diffuse loss of white matter integrity in SCZ. Our finding that the loss of integrity disproportionately involves white matter of low to moderate organization suggests an approach to the specificity of white matter abnormalities in SCZ based on microstructure rather than spatial distribution.
  • 机译 小世界网络的普遍性
    摘要:Small-world networks, according to Watts and Strogatz, are a class of networks that are “highly clustered, like regular lattices, yet have small characteristic path lengths, like random graphs.” These characteristics result in networks with unique properties of regional specialization with efficient information transfer. Social networks are intuitive examples of this organization, in which cliques or clusters of friends being interconnected but each person is really only five or six people away from anyone else. Although this qualitative definition has prevailed in network science theory, in application, the standard quantitative application is to compare path length (a surrogate measure of distributed processing) and clustering (a surrogate measure of regional specialization) to an equivalent random network. It is demonstrated here that comparing network clustering to that of a random network can result in aberrant findings and that networks once thought to exhibit small-world properties may not. We propose a new small-world metric, ω (omega), which compares network clustering to an equivalent lattice network and path length to a random network, as Watts and Strogatz originally described. Example networks are presented that would be interpreted as small-world when clustering is compared to a random network but are not small-world according to ω. These findings have important implications in network science because small-world networks have unique topological properties, and it is critical to accurately distinguish them from networks without simultaneous high clustering and short path length.
  • 机译 自闭症风险基因CNTNAP2的健康携带者的结构性大脑连接性改变。
    摘要:Recently, carriers of a common variant in the autism risk gene, CNTNAP2, were found to have altered functional brain connectivity using functional MRI. Here, we scanned 328 young adults with high-field (4-Tesla) diffusion imaging, to test the hypothesis that carriers of this gene variant would have altered structural brain connectivity. All participants (209 women, 119 men, age: 23.4±2.17 SD years) were scanned with 105-gradient high-angular-resolution diffusion imaging (HARDI) at 4 Tesla. After performing a whole-brain fiber tractography using the full angular resolution of the diffusion scans, 70 cortical surface-based regions of interest were created from each individual's co-registered anatomical data to compute graph metrics for all pairs of cortical regions. In graph theory analyses, subjects homozygous for the risk allele (CC) had lower characteristic path length, greater small-worldness and global efficiency in whole-brain analyses, and lower eccentricity (maximum path length) in 60 of the 70 nodes in regional analyses. These results were not reducible to differences in more commonly studied traits such as fiber density or fractional anisotropy. This is the first study that links graph theory metrics of brain structural connectivity to a common genetic variant linked with autism and will help us understand the neurobiology of the circuits implicated in the risk for autism.
  • 机译 作为复杂系统的大脑:使用网络科学作为了解大脑的工具
    摘要:Although graph theory has been around since the 18th century, the field of network science is more recent and continues to gain popularity, particularly in the field of neuroimaging. The field was propelled forward when Watts and Strogatz introduced their small-world network model, which described a network that provided regional specialization with efficient global information transfer. This model is appealing to the study of brain connectivity, as the brain can be viewed as a system with various interacting regions that produce complex behaviors. In practice, graph metrics such as clustering coefficient, path length, and efficiency measures are often used to characterize system properties. Centrality metrics such as degree, betweenness, closeness, and eigenvector centrality determine critical areas within the network. Community structure is also essential for understanding network organization and topology. Network science has led to a paradigm shift in the neuroscientific community, but it should be viewed as more than a simple “tool du jour.” To fully appreciate the utility of network science, a greater understanding of how network models apply to the brain is needed. An integrated appraisal of multiple network analyses should be performed to better understand network structure rather than focusing on univariate comparisons to find significant group differences; indeed, such comparisons, popular with traditional functional magnetic resonance imaging analyses, are arguably no longer relevant with graph-theory based approaches. These methods necessitate a philosophical shift toward complexity science. In this context, when correctly applied and interpreted, network scientific methods have a chance to revolutionize the understanding of brain function.
  • 机译 对象的工作记忆性能取决于额枕筋膜的微观结构
    摘要:Re-entrant circuits involving communication between the frontal cortex and other brain areas have been hypothesized to be necessary for maintaining the sustained patterns of neural activity that represent information in working memory, but evidence has so far been indirect. If working memory maintenance indeed depends on such temporally precise and robust long-distance communication, then performance on a delayed recognition task should be highly dependent on the microstructural integrity of white-matter tracts connecting sensory areas with prefrontal cortex. This study explored the effect of variations in white-matter microstructure on working memory performance in two separate groups of participants: patients with multiple sclerosis and age- and sex-matched healthy adults. Functional magnetic resonance imaging was performed to reveal cortical regions involved in spatial and object working memory, which, in turn, were used to define specific frontal to extrastriate white-matter tracts of interest via diffusion tensor tractography. After factoring out variance due to age and the microstructure of a control tract (the corticospinal tract), the number of errors produced in the object working memory task was specifically related to the microstructure of the inferior frontal-occipital fasciculus. This result held for both groups, independently, providing a within-study replication with two different types of white-matter structural variability: multiple sclerosis–related damage and normal variation. The results demonstrate the importance of interactions between specific regions of the prefrontal cortex and sensory cortices for a nonspatial working memory task that preferentially activates those regions.
  • 机译 地域学:我们从这里去哪里?
    摘要:Diffusion tractography offers enormous potential for the study of human brain anatomy. However, as a method to study brain connectivity, tractography suffers from limitations, as it is indirect, inaccurate, and difficult to quantify. Despite these limitations, appropriate use of tractography can be a powerful means to address certain questions. In addition, while some of tractography's limitations are fundamental, others could be alleviated by methodological and technological advances. This article provides an overview of diffusion magnetic resonance tractography methods with a focus on how future advances might address challenges in measuring brain connectivity. Parts of this review are somewhat provocative, in the hope that they may trigger discussions possibly lacking in a field where the apparent simplicity of the methods (compared to their functional magnetic resonance imaging counterparts) can hide some fundamental issues that ultimately hinder the interpretation of findings, and cast doubt as to what tractography can really teach us about human brain anatomy.
  • 机译 聆听不听:功能连接揭示了基本声音处理过程中多个非听觉网络的参与
    摘要:The present functional magnetic resonance imaging (fMRI) study presents data challenging the traditional view that sound is processed almost exclusively in the classical auditory pathway unless imbued with behavioral significance. In a first experiment, subjects were presented with broadband noise in on/off fashion as they performed an unrelated visual task. A conventional analysis assuming predictable sound-evoked responses demonstrated a typical activation pattern that was confined to classical auditory centers. In contrast, spatial independent component analysis (sICA) disclosed multiple networks of acoustically responsive brain centers. One network comprised classical auditory centers, but four others included nominally “nonauditory” areas: cingulo-insular cortex, mediotemporal limbic lobe, basal ganglia, and posterior orbitofrontal cortex, respectively. Functional connectivity analyses confirmed the sICA results by demonstrating coordinated activity between the involved brain structures. In a second experiment, fMRI data obtained from unstimulated (i.e., resting) subjects revealed largely similar networks. Together, these two experiments suggest the existence of a coordinated system of multiple acoustically responsive intrinsic brain networks, comprising classical auditory centers but also other brain areas. Our results suggest that nonauditory centers play a role in sound processing at a very basic level, even when the sound is not intertwined with behaviors requiring the well-known functionality of these regions.
  • 机译 基于功能性磁共振成像网络的神经元群体持续进行的内在活动对定量神经成像的作用
    摘要:A primary objective in neuroscience is to determine how neuronal populations process information within networks. In humans and animal models, functional magnetic resonance imaging (fMRI) is gaining increasing popularity for network mapping. Although neuroimaging with fMRI—conducted with or without tasks—is actively discovering new brain networks, current fMRI data analysis schemes disregard the importance of the total neuronal activity in a region. In task fMRI experiments, the baseline is differenced away to disclose areas of small evoked changes in the blood oxygenation level-dependent (BOLD) signal. In resting-state fMRI experiments, the spotlight is on regions revealed by correlations of tiny fluctuations in the baseline (or spontaneous) BOLD signal. Interpretation of fMRI-based networks is obscured further, because the BOLD signal indirectly reflects neuronal activity, and difference/correlation maps are thresholded. Since the small changes of BOLD signal typically observed in cognitive fMRI experiments represent a minimal fraction of the total energy/activity in a given area, the relevance of fMRI-based networks is uncertain, because the majority of neuronal energy/activity is ignored. Thus, another alternative for quantitative neuroimaging of fMRI-based networks is a perspective in which the activity of a neuronal population is accounted for by the demanded oxidative energy (CMRO2). In this article, we argue that network mapping can be improved by including neuronal energy/activity of both the information about baseline and small differences/fluctuations of BOLD signal. Thus, total energy/activity information can be obtained through use of calibrated fMRI to quantify differences of ΔCMRO2 and through resting-state positron emission tomography/magnetic resonance spectroscopy measurements for average CMRO2.
  • 机译 电舌刺激可以使平衡受损的受试者的运动敏感型大脑网络内的活动正常化,如独立于组的成分分析所揭示的那样
    摘要:Multivariate analysis of functional magnetic resonance imaging (fMRI) data allows investigations into network behavior beyond simple activations of individual regions. We apply group independent component analysis to fMRI data collected in a previous study looking at the sustained neuromodulatory effects of electrical tongue stimulation in balance-impaired individuals. Twelve subjects with balance disorders viewed optic flow in an fMRI scanner before and after 5 days of electrical tongue stimulation. Nine healthy controls also viewed the visual stimuli but did not receive any stimulation. Multiple regression of the 47 estimated components found two that were modulated by the visual stimuli. Component 7, comprised primarily of the primary visual cortex (V1), responded to all visual stimuli and showed no difference in task-related activity between the healthy controls and the balance-impaired subjects before or after stimulation. Component 11 responded only to motion in the visual field and contained multiple cortical and subcortical regions involved in processing information pertinent to balance. Two-sample t-tests of the calculated signal change revealed that the task-related activity of this network is greater in balance-impaired subjects compared with controls before stimulation (p=0.02), but that this network hypersensitivity decreases after electrical tongue stimulation (p=0.001).
  • 机译 负功能连接性及其对静止状态人脑中正网络最短路径长度的依赖性
    摘要:It is suggested that structurally segregated and functionally specialized brain regions are mediated by synchrony over large-scale networks in order to provide the formation of dynamic links and integration functions. The existence of negative synchrony, or negative functional connectivity (NFC), however, has been a subject of debate in terms of its origin, interpretation, relationship with structural connectivity, and possible neurophysiological function. The present study, which incorporated 20 cognitively healthy elderly human subjects, focused on testing the hypothesis that NFC significantly correlates with the shortest path length (SPL) in the human brain network. Our theoretical calculation, simulated data, and human study results support this hypothesis. In the human study, we find that (1) the percentage of NFC connections among all connections between brain regions significantly correlates with spatial Euclidian distance; (2) the strength of the NFC between the right amygdala and the left dorsolateral prefrontal cortex is significantly correlated with the SPL across the 20 human subjects; (3) such a significant relationship between the NFC and SPL exists in all the NFC connections in the whole brain; and (4) the correlations between the NFC and SPL also are frequency bandwidth dependent. These results suggest that an accumulated phased delay gives rise to the NFC, along the shortest path in the large-scale brain functional network. It is suggested that our study can be extended to examine a variety of neurological diseases and psychiatric disorders by measuring the changes of SPL and functional reorganization in the brain.
  • 机译 异氟烷麻醉下大鼠体感皮层功能性磁共振成像信号中的自发性波动与宽带局域电位相关。
    摘要:Resting-state functional magnetic resonance imaging (fMRI) is widely used for exploring spontaneous brain activity and large-scale networks; however, the neural processes underlying the observed resting-state fMRI signals are not fully understood. To investigate the neural correlates of spontaneous low-frequency fMRI fluctuations and functional connectivity, we developed a rat model of simultaneous fMRI and multiple-site intracortical neural recordings. This allowed a direct comparison to be made between the spontaneous signals and interhemispheric connectivity measured with the two modalities. Results show that low-frequency blood oxygen level-dependent (BOLD) fluctuations (<0.1 Hz) correlate significantly with slow power modulations (<0.1 Hz) of local field potentials (LFPs) in a broad frequency range (1–100 Hz) under isoflurane anesthesia (1%–1.8%). Peak correlation occurred between neural and hemodynamic activity when the BOLD signal was delayed by ∼4 sec relative to the LFP signal. The spatial location and extent of correlation was highly reproducible across studies, with the maximum correlation localized to a small area surrounding the site of microelectrode recording and to the homologous area in the contralateral hemisphere for most rats. Interhemispheric connectivity was calculated using BOLD correlation and band-limited LFP (1–4, 4–8, 8–14, 14–25, 25–40, and 40–100 Hz) coherence. Significant coherence was observed for the slow power changes of all LFP frequency bands as well as in the low-frequency BOLD data. A preliminary investigation of the effect of anesthesia on interhemispheric connectivity indicates that coherence in the high-frequency LFP bands declines with increasing doses of isoflurane, whereas coherence in the low-frequency LFP bands and the BOLD signal increases. These findings suggest that resting-state fMRI signals might be a reflection of broadband LFP power modulation, at least in isoflurane-anesthetized rats.
  • 机译 皮层下结构之间的解剖学连通性
    摘要:Understanding anatomical connectivity is crucial for improving outcomes of deep brain stimulation surgery. Tractography is a promising method for noninvasively investigating anatomical connectivity, but connections between subcortical regions have not been closely examined by this method. As many connections to subcortical regions converge at the internal capsule (IC), we investigate the connectivity through the IC to three subcortical nuclei (caudate, lentiform nucleus, and thalamus) in six macaques. We show that a statistical correction for a known distance-related artifact in tractography results in large changes in connectivity patterns. Our results suggest that care should be taken in using tractography to assess anatomical connectivity between subcortical structures.
  • 机译 默认模式和注意力控制网络之间的连接渐变
    摘要:Functional imaging studies have shown reduced activity within the default mode network during attention-demanding tasks. The network circuitry underlying this suppression remains unclear. Proposed hypotheses include an attentional switch in the right anterior insula and reciprocal inhibition between the default mode and attention control networks. We analyzed resting state blood oxygen level dependent (BOLD) data from 1278 subjects from 26 sites and constructed whole-brain maps of functional connectivity between 7266 regions of interest (ROIs) covering the gray matter at ∼5 mm resolution. ROIs belonging to the default mode network and attention control network were identified based on correlation to six published seed locations. Spatial heterogeneity of correlation between the default mode and attention control networks was observed, with smoothly varying gradients in every hub of both networks that ranged smoothly from weakly but significantly anticorrelated to positively correlated. Such gradients were reproduced in 3 separate groups of subjects. Anticorrelated subregions were identified in major hubs of both networks. Between-network connectivity gradients strengthen with age during late adolescence and early adulthood, with associated sharpening of the boundaries of the default mode network, integration of the insula and cingulate with frontoparietal attentional regions, and decreasing correlation between the default mode and attention control networks with age.

客服邮箱:kefu@zhangqiaokeyan.com

京公网安备:11010802029741号 ICP备案号:京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有
  • 客服微信

  • 服务号