颞叶癫痫脑“默认模式”的fMRI研究

功能磁共振成像(functional magnetic resonance imaging,fMRI)被用于检测静息时脑功能神经网络.作者运用静息fMRI检测海马硬化颞叶癫痫(temporal lobe epilepsy,TLE)脑"默认模式",采用感兴趣区域功能连接分析检测16例TLE患者和16名正常对照静息时脑的"默认模式",并进行组内和组间分析.研究发现,与正常对照相比,TLE静息时海马、颞极、额叶、颞叶、壳核及楔前叶等脑区与后扣带回的功能连接增强.研究结果表明TLE患者的固有脑功能组织模式有可能出现紊乱.这一研究将有助于从脑功能的角度了解癫痫患者某些临床症状的发病机理,为今后癫痫诊治的发展提供一定的帮助.     

功能区胶质瘤患者初级运动皮层激活的偏侧化及运动网络功能连接研究

无运动障碍的功能区胶质瘤患者,其手术风险较高,结合手运动任务态功能磁共振(fMRI)及运动网络功能连接能否更准确的评估手术风险需要进一步探索.本研究收集24例运动功能区胶质瘤且无明显肢体运动功能障碍的患者,非运动功能区胶质瘤患者8例,术前进行fMRI手运动任务态及静息态检查,术后3个月对患者进行随访.计算初级运动皮质(M1)激活的偏侧化指数(lateralization indices,LI).选取运动网络感兴趣区域(ROI),计算双侧M1与各ROI间功能连接系数(FC).运用受试者工作特性曲线(receiver operating characteristic curve,ROC)评估M1激活的LI对术后偏瘫的预测效能.同非运动功能区胶质瘤患者相比,运动功能区胶质瘤患者M1激活LI显著升高(P=0.001).同术后未偏瘫功能区胶质瘤患者相比,术后偏瘫患者M1激活LI值显著升高(P=0.011).ROC曲线下面积(AUC)=0.867,临界点LI=0.31,LI≥0.31对术后偏瘫预测灵敏性为87.5%,特异性为87.5%.以M1激活LI≥0.31将病人分为手术高风险组及低风险组,手术高风险组患者双侧M1与运动网络多个ROI间FC出现显著改变.本研究中功能区胶质瘤患者虽无肢体运动功能障碍,但肿瘤对功能区皮层激活及运动网络FC已有不同程度的破坏;结合任务态及静息态fMRI可以更好地评估手术风险并了解机体功能受损及代偿机制.     

DLPFC在MCI患者和正常老年人归纳推理过程中的作用: 一项fMRI研究

以往对青年人被试的研究发现, 左侧背外侧前额(DLPFC)在归纳推理过程中起着非常重要的作用. 本研究使用功能磁共振成像(fMRI)考查这一脑区是否也在轻度认知障碍(MCI)患者及正常老年人进行归纳推理时被显著激活, 以及MCI患者和正常老年人在激活模式上是否存在差异. 实验结果发现, 与正常老年人相比, MCI患者在行为数据(反应时和正确率)和DLPFC的激活模式上没有差异, 但MCI患者DLPFC的BOLD信号强度低于正常老年人, 双侧DLPFC的功能连接强度显著高于正常老年人. 这可能是由于MCI患者在DLPFC的功能减弱, 因而需要加强与对侧脑区的协同来完成认知加工. 总之, 这一结果表明, 与青年人一样, DLPFC在老年人的归纳推理中也起着重要作用, 而且DLPFC功能的改变可能是一个先于影像学形态结构改变的MCI的早期诊断标记.     

研究报告: 大鼠感觉运动系统静息态脑网络研究

为了理解啮齿类动物的脑功能连接,本文利用9.4T fMRI获得轻度麻醉状态下大鼠静息状态及刺激激活的数据,通过互相关分析构建节点之间的相关系数矩阵并计算相应的网络参数．结果发现：给予前爪电刺激时,刺激对侧初级感觉皮层(S1)、丘脑(Tha)有较强的正激活,双侧尾状壳核(CPu)有较强的负激活．静息状态时大鼠感觉/运动皮层内部、丘脑内部的连接性较强,而感觉/运动皮层与丘脑之间的连接较弱,双侧感觉运动系统之间存在较强的同步低频振荡,感觉运动系统在静息态时的脑网络具有小世界属性．结果提示,啮齿类动物在大脑信息处理中的功能分离和整合可能与人类存在某些相似性,支持哺乳动物中枢神经系统的基本功能存在遗传保守性的观点．     

国人汉语Stroop任务的大脑激活模式研究

目的:采用功能磁共振成像(functional MRI,fMRI)方法考察汉语Slroop任务大脑激活模式.方法:对8例正常汉族人进行了汉语Stroop色词任务实验测试,同时采用Siemens Sonata 1.5 T成像系统,采集其脑部的BOLD-fMRI数据,通过AFNI软件进行统计分析得到脑功能活动的图像,分析不同脑区的激活模式.结果:汉语Slroop任务主要激活双侧额中回、额下回、前扣带回和顶后区,双侧额上回、中央前回、基底节区和颞叶也有不同程度激活.结论:汉语Stroop任务有固定的大脑激活模式,是一种研究大脑高级认知的良好的神经心理学任务.     

计算任务男女性别差异的fMRI研究

目的:用功能磁共振(functional Magnetic Resonance Imaging,FMRI)探讨男女不同性别在计算任务时脑活动的差异。方法:对10例男性、8例女性正常年青受试者进行简单及复杂任务的功能MRI扫描,采用SPM2软件进行数据分析和脑功能区定位。结果:计算任务中男女主要激活区域均为额前区、顶叶、枕叶及小脑,男性额前区及顶叶等计算功能区激活范围较女性广,其中以复杂计算为著。结论:相同的计算任务,男性激活的脑功能区范围多于女性。     

经颅电刺激对睡眠剥夺后双侧后扣带回皮质功能连接紊乱干预作用的初步研究*

目的: 探讨经颅电刺激对睡眠剥夺后双侧后扣带回皮质功能连接紊乱的干预作用。方法: 研究采用自身前后对照的试验设计。16名受试者均接受2次24 h睡眠剥夺,2次睡眠剥夺间隔3周,受试者分别于第1次正常睡眠后、24 h睡眠剥夺后、经颅电刺激(真或假刺激)干预后(真、假刺激电流大小均为1 mA,电流作用时间分别为20 min、2 s,干预实验均持续20 min)及第2次经颅电刺激(假或真刺激)干预后采集静息态磁共振成像数据。以睡眠剥夺前收集静息态功能磁共振数据作为基线,选取双侧后扣带回皮质作为种子点进行全脑功能连接分析,观察睡眠剥夺前后及经颅电刺激真、假刺激后大脑的功能连接变化。结果: 与正常睡眠后相比,24 h睡眠剥夺后双侧后扣带回皮质与双侧丘脑间的功能连接上升(P＜0.01),与右侧楔前叶、海马旁回以及双侧岛叶间的功能下降(P＜0.01)。与假刺激相比,给予真刺激后左侧后扣带回皮质与右侧楔前叶功能连接上升(P＜0.01);与双侧丘脑、岛叶及右侧大脑皮质功能连接下降(P＜0.01)。右侧后扣带回皮质与全脑的功能连接在双侧丘脑、右侧岛叶及大脑皮层间也存在下降(P＜0.01)。结论: 24 h睡眠剥夺可引起双侧后扣带回功能连接紊乱,而经颅电刺激可在一定程度上改善睡眠剥夺后的功能连接紊乱。     

未服药精神分裂症患者视觉刺激的功能磁共振成像研究

目的:探讨未服药精神分裂症患者和健康对照视觉刺激的脑区激活的差异.方法:对10例未服药精神分裂症患者(患者组)和10名年龄、教育程度和性别匹配的健康人(对照组)进行视觉信息处理过程的检查,应用功能磁共振成像(fMRI)技术,采用组块设计,以翻转棋盘格为视觉信息输入,以"十"型为对照,比较两组脑区激活区域的差异.结果:两组在中枢视觉区都有激活.但与对照组相比,患者组在视觉刺激时左侧顶下小叶激活增高.结论:精神分裂症患者视觉刺激后,左侧顶下小叶的异常激活,可能反映精神分裂症患者的代偿性,是其视觉信息加工受损的影像学证据.     

利用功能磁共振研究记忆功能的研究进展

功能磁共振成像(fMRI)作为一种无创伤,可反复实验的成像技术,已被广泛地应用于各项脑功能的研究。用fMRI进行脑功能研究的主要依据是血流敏感性和BOLD对比增强原理。记忆是人脑的高级功能,其过程分为编码加工、固化、存储和提取几个阶段。大脑皮质、海马、乳头体、丘脑是参与记忆的主要解剖结构。记忆的刺激方式对各个脑区的激活是具有差异性的,记忆功能的测量和分析方法也在不断的改进。年龄和性别的不同都会对记忆能力产生影响,同时激活的脑区也会有相应的改变。此外,情感和记忆的关系正越来越受到人们的关注。本文阐述利用功能磁共振成像研究记忆功能的最新进展。     

汉字字形认知研究的刺激源设计及在fMRI研究中的应用

目的:评估汉字字形刺激源在汉字认知fMRI研究中的有效性,并对参与汉字处理的脑皮层区域进行定位及初步的量化分析。方法:选择母语为汉语、经利手测试后为右利手且裸眼视力正常(大于等于1．0)的在校大学生10例(男6例,女4例)作为被试。试验任务采用组块设计,将汉字(非字、假字、真字)投射到屏幕上,受试者接受汉字字形图片的视觉刺激,按非字-假字-真字-非字-假字-真字顺序呈现,共6个block。数据处理及统计分析采用国际通用的AFNI软件。结果:左额叶上、中、下回(包括Broca's area)、左中央前回(BA6)、左顶上小叶及顶下小叶(包括缘上回及角回)及双侧枕叶、楔前叶显著激活;左颞叶梭状回(BA37)、右额下回及双侧颞中、上回及扣带回显著激活,左大脑半球的激活体积明显大于右侧大脑半球。结论:本研究设计的汉字字形刺激源结合功能磁共振成像技术可以对汉字处理的相关大脑皮层区域进行定位,为研究人脑加工处理汉字的神经机制提供了一种有效的无创性影像学方法,并应用fMRI技术进一步证实其优势半球为左半球,且需要多种脑区共同参与完成。本试验模式可望成为一种对语言障碍病人进行脑功能检查的有效手段,从而为指导临床治疗和评价预后提供更丰富的信息。     

A Resting-State Functional Magnetic Resonance Imaging Study of Acute Carbon Monoxide Poisoning in Humans

The objective of this study was to evaluate the brain function characteristics of carbon monoxide poisoning patients using resting-state functional magnetic resonance imaging (fMRI) method. For this purpose, 12 carbon monoxide poisoning patients and healthy controls were subjected to resting-state fMRI scans separately. A regional homogeneity (ReHo) approach was used to analyze the brain function in carbon monoxide poisoning patients. Compared with control group, the value of ReHo in carbon monoxide poisoning group showed distinct decrease in bilateral superior frontal gyrus, middle frontal gyrus, right cuneus, left middle temporal gyrus, right insula, and cerebellum. Therefore, it was concluded that the brain functions in carbon monoxide poisoning patients were abnormal under the resting-state. The cuneate lobe function may indicate the degree of brain hypoxia and strengthening the cerebellar function training may promote the rehabilitation process.     

Identify schizophrenia using resting-state functional connectivity: an exploratory research and analysis

ABSTRACT: BACKGROUND: Schizophrenia is a severe mental illness associated with the symptoms such as hallucination and delusion. The objective of this study was to investigate the abnormal resting-state functional connectivity patterns of schizophrenic patients which could identify furthest patients from healthy controls. METHODS: The whole-brain resting-state fMRI was performed on patients diagnosed with schizophrenia (n=22) and on age- and gender-matched, healthy control subjects (n=22). To differentiate schizophrenic individuals from healthy controls, the multivariate classification analysis was employed. The weighted brain regions were got by reconstruction arithmetic to extract highly discriminative functional connectivity information. RESULTS: The results showed that 93.2% (p<0.001) of the subjects were correctly classified via the leave-one-out cross-validation method. And most of the altered functional connections identified located within the visual cortical-, default-mode-, and sensorimotor network. Furthermore, in reconstruction arithmetic, the fusiform gyrus exhibited the greatest amount of weight. CONCLUSIONS: This study demonstrates that schizophrenic patients may be successfully differentiated from healthy subjects by using whole-brain resting-state fMRI, and the fusiform gyrus may play an important functional role in the physiological symptoms manifested by schizophrenic patients. The brain region of great weight may be the problematic region of information exchange in schizophrenia. Thus, our result may provide insights into the identification of potentially effective biomarkers for the clinical diagnosis of schizophrenia.     

Changes of Functional Brain Networks in Major Depressive Disorder: A Graph Theoretical Analysis of Resting-State fMRI

Recent developments in graph theory have heightened the need for investigating the disruptions in the topological structure of functional brain network in major depressive disorder (MDD). In this study, we employed resting-state functional magnetic resonance imaging (fMRI) and graph theory to examine the whole-brain functional networks among 42 MDD patients and 42 healthy controls. Our results showed that compared with healthy controls, MDD patients showed higher local efficiency and modularity. Furthermore, MDD patients showed altered nodal centralities of many brain regions, including hippocampus, temporal cortex, anterior cingulate gyrus and dorsolateral prefrontal gyrus, mainly located in default mode network and cognitive control network. Together, our results suggested that MDD was associated with disruptions in the topological structure of functional brain networks, and provided new insights concerning the pathophysiological mechanisms of MDD.     

Reduction in inter-hemispheric connectivity in disorders of consciousness

Clinical diagnosis of disorders of consciousness (DOC) caused by brain injury poses great challenges since patients are often behaviorally unresponsive. A promising new approach towards objective DOC diagnosis may be offered by the analysis of ultra-slow (<0.1 Hz) spontaneous brain activity fluctuations measured with functional magnetic resonance imaging (fMRI) during the resting-state. Previous work has shown reduced functional connectivity within the "default network", a subset of regions known to be deactivated during engaging tasks, which correlated with the degree of consciousness impairment. However, it remains unclear whether the breakdown of connectivity is restricted to the "default network", and to what degree changes in functional connectivity can be observed at the single subject level. Here, we analyzed resting-state inter-hemispheric connectivity in three homotopic regions of interest, which could reliably be identified based on distinct anatomical landmarks, and were part of the "Extrinsic" (externally oriented, task positive) network (pre- and postcentral gyrus, and intraparietal sulcus). Resting-state fMRI data were acquired for a group of 11 healthy subjects and 8 DOC patients. At the group level, our results indicate decreased inter-hemispheric functional connectivity in subjects with impaired awareness as compared to subjects with intact awareness. Individual connectivity scores significantly correlated with the degree of consciousness. Furthermore, a single-case statistic indicated a significant deviation from the healthy sample in 5/8 patients. Importantly, of the three patients whose connectivity indices were comparable to the healthy sample, one was diagnosed as locked-in. Taken together, our results further highlight the clinical potential of resting-state connectivity analysis and might guide the way towards a connectivity measure complementing existing DOC diagnosis.     

Changes in Thalamic Connectivity in the Early and Late Stages of Amnestic Mild Cognitive Impairment: A Resting-State Functional Magnetic Resonance Study from ADNI

We used resting-state functional magnetic resonance imaging (fMRI) to investigate changes in the thalamus functional connectivity in early and late stages of amnestic mild cognitive impairment. Data of 25 late stages of amnestic mild cognitive impairment (LMCI) patients, 30 early stages of amnestic mild cognitive impairment (EMCI) patients and 30 well-matched healthy controls (HC) were analyzed from the Alzheimer’s disease Neuroimaging Initiative (ADNI). We focused on the correlation between low frequency fMRI signal fluctuations in the thalamus and those in all other brain regions. Compared to healthy controls, we found functional connectivity between the left/right thalamus and a set of brain areas was decreased in LMCI and/or EMCI including right fusiform gyrus (FG), left and right superior temporal gyrus, left medial frontal gyrus extending into supplementary motor area, right insula, left middle temporal gyrus (MTG) extending into middle occipital gyrus (MOG). We also observed increased functional connectivity between the left/right thalamus and several regions in LMCI and/or EMCI including left FG, right MOG, left and right precuneus, right MTG and left inferior temporal gyrus. In the direct comparison between the LMCI and EMCI groups, we obtained several brain regions showed thalamus-seeded functional connectivity differences such as the precentral gyrus, hippocampus, FG and MTG. Briefly, these brain regions mentioned above were mainly located in the thalamo-related networks including thalamo-hippocampus, thalamo-temporal, thalamo-visual, and thalamo-default mode network. The decreased functional connectivity of the thalamus might suggest reduced functional integrity of thalamo-related networks and increased functional connectivity indicated that aMCI patients could use additional brain resources to compensate for the loss of cognitive function. Our study provided a new sight to understand the two important states of aMCI and revealed resting-state fMRI is an appropriate method for exploring pathophysiological changes in aMCI.     

基于fMRI的屈光参差性弱视静息视觉网络的研究

利用静息功能磁共振成像技术,对屈光参差性弱视(anisometropic amblyopia)患者静息态视觉网络进行研究,分析此类患者大脑视觉皮层功能受到的影响。采用独立成分分析(independent component analysis, ICA)这一数据驱动方法对8名屈光参差性弱视患者和11名正常对照的静息数据进行分离,并采用拟合度值(goodness-of-fit scores)分析挑选出静息视觉网络,将结果进行组内分析和组间分析。结果表明,屈光参差性弱视的静息视觉网络中,多级视觉皮层均发生了明显的功能损害,其功能连接度的范围与强度显著低于正常组,而且,高级别纹外皮层比低级别纹状皮层损害更加明显。静息fMRI为深入研究弱视初、高级视觉皮层功能损害的发病机制提供了新的方法。     

Alterations in Cortical Sensorimotor Connectivity following Complete Cervical Spinal Cord Injury: A Prospective Resting-State fMRI Study

Functional magnetic resonance imaging (fMRI) studies have demonstrated alterations during task-induced brain activation in spinal cord injury (SCI) patients. The interruption to structural integrity of the spinal cord and the resultant disrupted flow of bidirectional communication between the brain and the spinal cord might contribute to the observed dynamic reorganization (neural plasticity). However, the effect of SCI on brain resting-state connectivity patterns remains unclear. We undertook a prospective resting-state fMRI (rs-fMRI) study to explore changes to cortical activation patterns following SCI. With institutional review board approval, rs-fMRI data was obtained in eleven patients with complete cervical SCI (>2 years post injury) and nine age-matched controls. The data was processed using the Analysis of Functional Neuroimages software. Region of interest (ROI) based analysis was performed to study changes in the sensorimotor network using pre- and post-central gyri as seed regions. Two-sampled t-test was carried out to check for significant differences between the two groups. SCI patients showed decreased functional connectivity in motor and sensory cortical regions when compared to controls. The decrease was noted in ipsilateral, contralateral, and interhemispheric regions for left and right precentral ROIs. Additionally, the left postcentral ROI demonstrated increased connectivity with the thalamus bilaterally in SCI patients. Our results suggest that cortical activation patterns in the sensorimotor network undergo dynamic reorganization following SCI. The presence of these changes in chronic spinal cord injury patients is suggestive of the inherent neural plasticity within the central nervous system.     

Pattern classification of large-scale functional brain networks: identification of informative neuroimaging markers for epilepsy

The accurate prediction of general neuropsychiatric disorders, on an individual basis, using resting-state functional magnetic resonance imaging (fMRI) is a challenging task of great clinical significance. Despite the progress to chart the differences between the healthy controls and patients at the group level, the pattern classification of functional brain networks across individuals is still less developed. In this paper we identify two novel neuroimaging measures that prove to be strongly predictive neuroimaging markers in pattern classification between healthy controls and general epileptic patients. These measures characterize two important aspects of the functional brain network in a quantitative manner: (i) coordinated operation among spatially distributed brain regions, and (ii) the asymmetry of bilaterally homologous brain regions, in terms of their global patterns of functional connectivity. This second measure offers a unique understanding of brain asymmetry at the network level, and, to the best of our knowledge, has not been previously used in pattern classification of functional brain networks. Using modern pattern-recognition approaches like sparse regression and support vector machine, we have achieved a cross-validated classification accuracy of 83.9% (specificity: 82.5%; sensitivity: 85%) across individuals from a large dataset consisting of 180 healthy controls and epileptic patients. We identified significantly changed functional pathways and subnetworks in epileptic patients that underlie the pathophysiological mechanism of the impaired cognitive functions. Specifically, we find that the asymmetry of brain operation for epileptic patients is markedly enhanced in temporal lobe and limbic system, in comparison with healthy individuals. The present study indicates that with specifically designed informative neuroimaging markers, resting-state fMRI can serve as a most promising tool for clinical diagnosis, and also shed light onto the physiology behind complex neuropsychiatric disorders. The systematic approaches we present here are expected to have wider applications in general neuropsychiatric disorders.     

Functional Connectivity Estimated from Resting-State fMRI Reveals Selective Alterations in Male Adolescents with Pure Conduct Disorder

Conduct disorder (CD) is characterized by a persistent pattern of antisocial behavior and aggression in childhood and adolescence. Previous task-based and resting-state functional magnetic resonance imaging (fMRI) studies have revealed widespread brain regional abnormalities in adolescents with CD. However, whether the resting-state networks (RSNs) are altered in adolescents with CD remains unknown. In this study, resting-state fMRI data were first acquired from eighteen male adolescents with pure CD and eighteen age- and gender-matched typically developing (TD) individuals. Independent component analysis (ICA) was implemented to extract nine representative RSNs, and the generated RSNs were then compared to show the differences between the CD and TD groups. Interestingly, it was observed from the brain mapping results that compared with the TD group, the CD group manifested decreased functional connectivity in four representative RSNs: the anterior default mode network (left middle frontal gyrus), which is considered to be correlated with impaired social cognition, the somatosensory network (bilateral supplementary motor area and right postcentral gyrus), the lateral visual network (left superior occipital gyrus), and the medial visual network (right fusiform, left lingual gyrus and right calcarine), which are expected to be relevant to the perceptual systems responsible for perceptual dysfunction in male adolescents with CD. Importantly, the novel findings suggested that male adolescents with pure CD were identified to have dysfunctions in both low-level perceptual networks (the somatosensory network and visual network) and a high-order cognitive network (the default mode network). Revealing the changes in the functional connectivity of these RSNs enhances our understanding of the neural mechanisms underlying the modulation of emotion and social cognition and the regulation of perception in adolescents with CD.     

Disrupted functional brain connectivity in partial epilepsy: a resting-state fMRI study

Examining the spontaneous activity to understand the neural mechanism of brain disorder is a focus in recent resting-state fMRI. In the current study, to investigate the alteration of brain functional connectivity in partial epilepsy in a systematical way, two levels of analyses (functional connectivity analysis within resting state networks (RSNs) and functional network connectivity (FNC) analysis) were carried out on resting-state fMRI data acquired from the 30 participants including 14 healthy controls(HC) and 16 partial epilepsy patients. According to the etiology, all patients are subdivided into temporal lobe epilepsy group (TLE, included 7 patients) and mixed partial epilepsy group (MPE, 9 patients). Using group independent component analysis, eight RSNs were identified, and selected to evaluate functional connectivity and FNC between groups. Compared with the controls, decreased functional connectivity within all RSNs was found in both TLE and MPE. However, dissociating patterns were observed within the 8 RSNs between two patient groups, i.e, compared with TLE, we found decreased functional connectivity in 5 RSNs increased functional connectivity in 1 RSN, and no difference in the other 2 RSNs in MPE. Furthermore, the hierarchical disconnections of FNC was found in two patient groups, in which the intra-system connections were preserved for all three subsystems while the lost connections were confined to intersystem connections in patients with partial epilepsy. These findings may suggest that decreased resting state functional connectivity and disconnection of FNC are two remarkable characteristics of partial epilepsy. The selective impairment of FNC implicated that it is unsuitable to understand the partial epilepsy only from global or local perspective. We presumed that studying epilepsy in the multi-perspective based on RSNs may be a valuable means to assess the functional changes corresponding to specific RSN and may contribute to the understanding of the neuro-pathophysiological mechanism of epilepsy.