Disrupted thalamocortical connectivity in PSP: a resting-state fMRI, DTI, and VBM study

Progressive supranuclear palsy (PSP) is associated with pathological changes along the dentatorubrothalamic tract and in premotor cortex. We aimed to assess whether functional neural connectivity is disrupted along this pathway in PSP, and to determine how functional changes relate to changes in structure and diffusion. Eighteen probable PSP subjects and 18 controls had resting-state (task-free) fMRI, diffusion tensor imaging and structural MRI. Functional connectivity was assessed between thalamus and the rest of the brain, and within the basal ganglia, salience and default mode networks (DMN). Patterns of atrophy were assessed using voxel-based morphometry, and patterns of white matter tract degeneration were assessed using tract-based spatial statistics. Reduced in-phase functional connectivity was observed between the thalamus and premotor cortex including supplemental motor area (SMA), striatum, thalamus and cerebellum in PSP. Reduced connectivity in premotor cortex, striatum and thalamus were observed in the basal ganglia network and DMN, with subcortical salience network reductions. Tract degeneration was observed between cerebellum and thalamus and in superior longitudinal fasciculus, with grey matter loss in frontal lobe, premotor cortex, SMA and caudate nucleus. SMA functional connectivity correlated with SMA volume and measures of cognitive and motor dysfunction, while thalamic connectivity correlated with degeneration of superior cerebellar peduncles. PSP is therefore associated with disrupted thalamocortical connectivity that is associated with degeneration of the dentatorubrothalamic tract and the presence of cortical atrophy.     

青少年抑郁症的功能磁共振研究进展

近年来功能磁共振成像在成人抑郁症中的研究较为深入,而对于青少年抑郁症的研究则相对有限,故本文就目前功能性磁共振在青少年抑郁症中的研究进展作一综述。     

Abnormal baseline brain activity in patients with neuromyelitis optica: A resting-state fMRI study

Purpose

Recent immunopathologic and MRI findings suggest that tissue damage in neuromyelitis optica (NMO) is not limited to spinal cord and optic nerve, but also in brain. Baseline brain activity can reveal the brain functional changes to the tissue damages and give clues to the pathophysiology of NMO, however, it has never been explored by resting-state functional MRI (fMRI). We used regional amplitude of low frequency fluctuation (ALFF) as an index in resting-state fMRI to investigate how baseline brain activity changes in patients with NMO.

Methods

Resting-state fMRIs collected from seventeen NMO patients and seventeen age- and sex-matched normal controls were compared to investigate the ALFF difference between the two groups. The relationships between ALFF in regions with significant group differences and the EDSS (Expanded Disability Status Scale), disease duration were further explored.

Results

Our results showed that NMO patients had significantly decreased ALFF in precuneus, posterior cingulate cortex (PCC) and lingual gyrus; and increased ALFF in middle frontal gyrus, caudate nucleus and thalamus, compared to normal controls. Moderate negative correlations were found between the EDSS and ALFF in the left middle frontal gyrus (r = −0.436, p = 0.040) and the left caudate (r = −0.542, p = 0.012).

Conclusion

The abnormal baseline brain activity shown by resting-state fMRI in NMO is relevant to cognition, visual and motor systems. It implicates a complex baseline brain status of both functional impairments and adaptations caused by tissue damages in these systems, which gives clues to the pathophysiology of NMO.     

Large-scale directional connections among multi resting-state neural networks in human brain: a functional MRI and Bayesian network modeling study

This study examined the large-scale connectivity among multiple resting-state networks (RSNs) in the human brain. Independent component analysis was first applied to the resting-state functional MRI (fMRI) data acquired from 12 healthy young subjects for the separation of RSNs. Four sensory (lateral and medial visual, auditory, and sensory-motor) RSNs and four cognitive (default-mode, self-referential, dorsal and ventral attention) RSNs were identified. Gaussian Bayesian network (BN) learning approach was then used for the examination of the conditional dependencies among these RSNs and the construction of the network-to-network directional connectivity patterns. The BN based results demonstrated that sensory networks and cognitive networks were hierarchically organized. Specially, we found the sensory networks were highly intra-dependent and the cognitive networks were strongly intra-influenced. In addition, the results depicted dominant bottom-up connectivity from sensory networks to cognitive networks in which the self-referential and the default-mode networks might play respectively important roles in the process of resting-state information transfer and integration. The present study characterized the global connectivity relations among RSNs and delineated more characteristics of spontaneous activity dynamics.     

静息态脑功能成像与皮层电刺激定位皮质运动区的对照研究

目的 以术中皮层电刺激为对照,评价运动区附近脑肿瘤患者术前运用基于血氧水平依赖(BOLD)的静息态功能磁共振成像(rs-fMRI)方法定位皮质运动区的准确性.方法 选取18例运动区脑肿瘤患者,手术前采用rs-fMRI定位皮质运动区,以术中皮层电刺激作为皮质运动区定位的标准技术,比较两种技术的符合度,以评价rs-fMRI定位皮质运动区的准确性.结果 rs-fMRI与术中皮层电刺激的吻合率为92.9％,肿瘤全切率为77.8％,11例术后肌力不变,4例术后肌力好转,3例术后肌力下降.结论 rs-fMRI具有较高的敏感性和精确度,可作为术前皮质运动区定位的新方法,为手术方案的制定及预后评估提供有价值的信息.     

A geometric view of global signal confounds in resting-state functional MRI

Resting-state functional magnetic resonance imaging (fMRI) is proving to be an effective tool for mapping the long-range functional connections of the brain in both health and disease. One of the primary measures of connectivity is the correlation between the blood oxygenation level dependent (BOLD) time series observed in different brain regions. The computation of the correlation is often dominated by the presence of a strong global component that can introduce significant variability across functional connectivity maps acquired from different experimental scans or subjects. To address this issue, a variety of global signal correction methods have been proposed, but there is currently a lack of a clear consensus on the best approach to use. Furthermore, there has been concern that some global signal correction methods, such as global signal regression, may produce significant negative bias in the correlation values. In this paper we introduce a framework for visualizing the signal structure of resting-state fMRI data and characterizing the properties of the global signal. Using this framework, we demonstrate that a portion of the global signal can be viewed as an additive confound that increases with the mean BOLD amplitude. An approach for minimizing the contribution of this additive confound is presented, and an initial comparison with existing global signal correction methods is provided.     

多发性硬化（MS）患者静息态视觉网络的脑功能研究

目的评价静息态功能磁共振（rfMRI）方法研究多发性硬化患者视觉网络的价值。方法 34例多发性硬化患者及性别、年龄相匹配的34名健康志愿者均接受静息态功能MRI扫描（采用西门子MAGNRTOM3.0T Trio Tim）,基于Mat-lab2009a平台使用独立成分分析法（independent component analysis,ICA）提取并比较两组视觉网络功能成分的差异,数据统计采用统计参数图（SPM8）软件（双样本t检验）。结果与对照组比较,患者组在左侧楔叶、双侧距状裂、双侧枕上回、左侧楔前叶出现神经元活动增强区。说明患者组静息态视觉网络存在一定的代偿。结论 rfMRI是研究脑功能网络的一种有效办法。     

Interaction between aging and neurodegeneration in amyotrophic lateral sclerosis

We assessed the spontaneous blood-oxygen-level-dependent signal fluctuations in the resting-state brain networks of amyotrophic lateral sclerosis patients and their relation to physiologically sensitive and disease modified functional magnetic resonance imaging parameters.     

多发性硬化功能磁共振的研究进展

常规MR检查可以准确显示多发性硬化(MS)病灶的形态学变化,而fMRI能够显示MS病程演变的病理生理过程,为MS研究提供了新的视角.本文就近年来fMRI在MS研究中的应用进行综述.     

垂体腺瘤致视力障碍患者视觉皮层及相关功能网络静息状态局部一致性的改变

目的 探索垂体腺瘤致视力障碍患者视觉皮层及相关功能网络的神经可塑性。 方法 以25例垂体腺瘤致视力障碍患者及25例与之年龄、性别相匹配矫正后视力正常患者为研究对象,进行神经眼科学检查及结构态和静息态功能核磁扫描。分别对两组受试者静息状态视觉皮层及相关功能网络进行局部一致性分析后,再采用双样本t检验进行统计学分析。 结果 与正常人群受试者相比,垂体瘤所致视力障碍患者组双侧V1、V2、V3、枕叶外侧皮层,梭状回、MT+以及丘脑局部一致性显著降低,而双侧楔前回、前额叶、扣带回后部皮层、岛叶、缘上回、辅助运动区局部一致性升高。 结论 垂体腺瘤致前视路功能障碍可引起患者视觉皮层内部脑区神经活动减弱,视觉皮层外默认网络及显著网络内重要脑区神经活动增强。