视神经脊髓炎患者功能连接密度变化的静息态fMRI研究

目的利用基于体素的功能连接密度(functional connectivity density,FCD)图方法观察视神经脊髓炎(neuromyelitis optica,NMO)患者静息状态下脑网络水平各脑区重要程度的异常改变,并评价其与临床评分、病程等的相关性。材料与方法搜集20例NMO患者及20例年龄、性别相匹配的健康志愿者静息态功能磁共振(resting state functional MRI,rs-f MRI)数据,所得数据利用基于Matlab平台的DPARSFA软件进行图像预处理,然后利用其度中心度(degree centrality,DC)选项计算出FCD值,用SPM8软件进行平滑处理,得到二值化的平均FCD值,组间进行双样本t检验比较两组之间FCD有差异的脑区,分析有差异的脑区FCD值与临床扩展残疾评分量表(expanded disability status scale,EDSS)评分及病程的相关性。结果与健康对照组相比,NMO患者FCD增加的脑区以左侧小脑半球(下半月小叶)为主;FCD减低的脑区主要包括双侧额叶(BA11)、左侧舌回、双侧小脑半球(方形小叶后部)(P0.001,未校正,体素30)。NMO患者的病程与左侧小脑半球(下半月小叶)FCD呈正相关(r=0.6,P=0.005)。结论 NMO患者脑功能网络连接属性存在异常,表现为多个脑功能区FCD增高或减低,可能与NMO患者肢体及认知功能障碍发生的神经病理机制有关。     

基于静息态功能成像的遗忘型轻度认知障碍患者核心脑网络变化研究

目的探索遗忘型轻度认知障碍(amnestic mild cognitive impairment,a MCI)患者的神经影像学指标。材料与方法采用镜像同伦功能连接(voxelmirrored homotopic connectivity,VMHC)和格兰杰因果分析(Granger causality analysis,GCA)技术对30例阿尔茨海默病(Alzheimer's disease,AD)患者、14例aMCI患者和18例健康对照(healthy controls,HC)的静息态f MRI数据进行处理。结果使用VMHC和GCA技术,发现三组中默认网络(default-mode network,DMN)、突显网络(salience network,SN)和执行控制网络(executive control network,ECN)三个核心脑网络的连接差异。在三个核心脑网络内,VMHC显示AD组中的连接性较HC和aMCI组显著降低,但是在aMCI和HC组之间没有显著差异。从GCA获得的有向功能连接可以区分AD、aMCI和HC组。结论在三个核心脑网络中观察到的变化可以作为aMCI患者的神经影像学指标,用于区分AD、aMCI患者及HC。     

帕金森病静息状态下纹状体功能连接的fMRI研究

目的应用血氧水平依赖的功能性磁共振成像研究帕金森病(Parkinson's disease,PD)静息状态下功能连接的改变。材料与方法对35例符合PD诊断标准的患者及20名健康者行静息态脑功能性磁共振成像,选双侧纹状体(striaum,STR)为感兴趣区,采用双样本t检验分别比较左侧STR(L-STR)、右侧STR(R-STR)在两组间的脑功能连接的差异。结果 (1)以L-STR为种子点时,PD组右侧前额叶背外侧部、双侧后扣带回皮质、左侧中央前后回、顶下小叶、左侧楔前叶、左侧缘上回等脑区的正连接较正常组减弱(P0.05,Alpha Sim校正),额下回、海马旁回、左侧海马、左侧岛叶正连接增强(P0.05,Alpha Sim校正)。(2)以R-STR为种子点时,PD组右侧前额叶背外侧部、双侧后扣带回皮质等脑区正连接较正常组减弱(P0.05,Alpha Sim校正),右侧舌回、岛叶、海马旁回、双侧海马、左侧丘脑等脑区正连接增强(P0.05,Alpha Sim校正)。结论静息状态下PD患者的脑功能连接网络存在异常。     

吸烟者静息态fMRI脑功能连接研究

目的 采用静息态fMRI分数低频振幅技术（fALFF）及功能连接方法分析吸烟者脑功能活动。方法 收集53名吸烟者（吸烟组）和53名不吸烟者（对照组）的静息态fMRI资料,并将吸烟组分为少量吸烟亚组与大量吸烟亚组、轻度成瘾亚组与重度成瘾亚组,计算受检者fALFF值,观察2组及不同亚组间fALFF值、全脑功能连接差异。结果 与对照组相比,吸烟组左侧边缘叶等脑区fALFF值增加,右侧颞上回等脑区fALFF值下降;与少量吸烟亚组相比,大量吸烟亚组右侧颞上回等脑区fALFF值升高,双侧边缘叶等脑区fALFF值下降;与轻度成瘾亚组相比,重度成瘾亚组双侧额中回等脑区fALFF值增加,左侧边缘叶等脑区fALFF值下降。吸烟组较对照组可见多发功能连接增强和减低的脑区。结论 吸烟者与成瘾相关脑区活动增强、情绪控制脑区活动减弱,且部分脑区活动改变与吸烟量及烟瘾程度有关。     

静息态fMRI评价进食前后脑默认网络变化

目的 采用静息态fMRI评价进食前后脑默认网络（DMN）的变化。方法 选取15名健康志愿者,均进食标准实验早餐,于空腹、早餐后、餐后2 h及午餐前4个时间段接受静息态fMRI检查。采用独立成分分析方法提取DMN。将提取的4个时间段DMN数据进行重复测量方差分析,获得差异有统计学意义的脑区,再将其作为蒙片,提取差异脑区的功能连接Z值,并进行统计学分析。结果 4个不同时间段时,前扣带回与内侧前额叶眶回的功能连接差异有统计学意义（P<0.001,体素数目>85个）。与空腹比较,早餐后及餐后2 h前扣带回与内侧前额叶眶回的功能连接Z值较小（P均<0.05）;与午餐前比较,早餐后及餐后2 h功能连接Z值亦较小（P<0.05）;余时间段两两比较,前扣带回与内侧前额叶眶回的功能连接Z值差异均无统计学意义（P均>0.05）。结论 进食前后前扣带回和内侧前额叶眶回的功能连接发生相应变化。     

正常人脑静息态功能磁共振的脑功能连接

目的探讨正常人脑静息状态下的不同专属脑网络间的连接强度及其意义。方法选取36名健康受试者进行静息态功能磁共振(rs-fMRI)扫描,采用独立成分分析(ICA)方法分离静息状态五大专属性功能脑网络,将五大脑网络分别作为感兴趣区,并采用多变量Granger因果分析方法(GCA)分析相关脑网络之间的功能因果连接的强度关系。采用SPM5.0软件进行分析处理。结果应用ICA方法得到5个经典的正常人静息态脑网络成分,分别为默认网络(DMN)、记忆网络(MeN)、运动网络(MoN)、听觉网络(AN)和执行控制网络(ECN)。GCA分析表明,DMN和其余4个网络之间、MeN和ECN之间、AN和MoN之间、ECN和AN之间均存在显著的因果联系。结论正常人在静息状态下存在特定的脑功能连接网络,且这些网络之间有着显著的因果联系。     

首发轻中度抑郁症脑局部一致性静息态fMRI应用研究

目的通过静息态功能磁共振成像(resting-state functional MRI,rs-fMRI)技术探讨首发轻中度抑郁症患者异常脑区的功能状态,为抑郁症病因的探索及临床治疗提供新的思路。材料与方法对14例首发轻中度抑郁症患者(符合汉密尔顿抑郁量表评分17~24分)和14名相匹配的健康被试行rs-fMRI扫描。基于局部一致性(regional homogeneity,ReHo)方法计算体素的肯德尔和谐系数(Kendall's coefficient of concordance,KCC),得出全脑每个体素的ReHo值。统计分析采用SPM8软件包完成。结果患者组双侧梭状回、双侧扣带回及右侧小脑脚2区、右侧丘脑、右侧颞中回及左侧丘脑内侧背核等脑区的ReHo显著高于对照组,而在双侧内侧额上回及左侧额中回、左侧额内侧回、左侧枕中回、左侧枕下回及左侧中央旁小叶等脑区ReHo显著减低(P0.05,K10)。结论抑郁症患者局部脑区血氧水平依赖信号的改变,可以间接反映功能相关脑区内神经元时间同步性的变化,有助于对抑郁症患者早期有效的筛选以及情绪异常活动性脑区的定位检测。     

磁共振功能成像在胎盘中的应用进展

胎盘功能的评估对理解和诊断胎盘疾病至关重要。近年来,磁共振功能成像越来越多地应用于胎盘的动物实验和临床研究,能够提供胎盘的血流灌注、氧合状态、组织扩散和代谢等功能信息,具有较高的研究价值和良好的临床应用前景。     

静息态fMRI观察轻、中度阿尔茨海默病患者脑区功能连接异常

目的 探讨轻、中度阿尔茨海默病（AD）患者全脑功能连接改变及差异。方法 对轻、中度AD患者（轻、中度AD组,各25例）及25名健康体检者（对照组,25名）行静息态fMRI。计算全脑116个脑区的功能连接,以单因素方差分析3组功能连接的差异,采用双样本t检验比较2组间功能连接对的差异。结果 与轻度AD组比较,中度AD组小脑内部及后扣带回与颞叶海马等的功能连接减低,双侧海马间、后扣带回与内侧眶部额上回等脑区功能连接增加。与对照组比较,轻度AD组双侧海马间、小脑蚓部间功能连接增加,后扣带回与颞部海马、眶部额中回及背外侧额上回等脑区功能连接减低;中度AD组表现为小脑内部以及后扣带回与颞部海马、眶部额中回等脑区功能连接减低,后扣带回与内侧眶部额上回以及双侧海马等脑区功能连接增加（P均< 0.05）。结论 中度与轻度AD患者脑功能连接异常存在差异,包括小脑内、双侧海马间连接异常,后扣带回连接减低以及微弱代偿。     

颞叶癫痫患者静息态fMRI功能连接强度的研究

目的采用基于全脑体素水平的静息态功能磁共振成像(restingstate functional magnetic resonance imaging,rs-f MRI)功能连接强度(functional connectivity strength,FCS)方法分析颞叶癫痫(temporal lobe epilepsy,TLE)患者脑网络水平改变。材料与方法对30例TLE患者(TLE组)和27名年龄、性别和受教育程度相匹配的健康志愿者(正常对照组)进行rs-f MRI数据采集及行为学测评。对rs-f MRI数据后处理,得到全脑FCS图。两组被试间年龄、受教育年限等各项临床基本资料以及各项神经心理学测评结果的差异采用双样本t检验进行比较,两组间性别的差异采用卡方检验进行比较。采用一般线性模型比较TLE组与正常对照组全脑FCS的差异。采用线性相关分析评价组间差异脑区的FCS值与行为学评分的关系。结果与正常对照组相比,TLE组在左侧颞上回、右侧颞上回、右侧额上回以及右侧额中回等脑区FCS值显著减低(P0.05,错误发现率法校正)。TLE患者贝克抑郁自评量表评分与右侧额上回FCS值呈负相关(r=-0.433,P=0.024);特质焦虑问卷评分与左侧颞上回FCS呈负相关(r=-0.434,P=0.024)。结论本研究发现TLE患者多个脑区的全脑功能连接强度明显降低,有助于进一步揭示颞叶癫痫发病的神经机制。     

Anticorrelated resting-state functional connectivity in awake rat brain

Resting-state functional connectivity (RSFC) measured by functional magnetic resonance imaging has played an essential role in understanding neural circuitry and brain diseases. The vast majority of RSFC studies have been focused on positive RSFC, whereas our understanding about its conceptual counterpart - negative RSFC (i.e. anticorrelation) - remains elusive. To date, anticorrelated RSFC has yet been observed without the commonly used preprocessing step of global signal correction. However, this step can induce artifactual anticorrelation (Murphy et al., 2009), making it difficult to determine whether the observed anticorrelation in humans is a processing artifact (Fox et al., 2005). In this report we demonstrated robust anticorrelated RSFC in a well characterized frontolimbic circuit between the infralimbic cortex (IL) and amygdala in the awake rat. This anticorrelation was anatomically specific, highly reproducible and independent of preprocessing methods. Interestingly, this anticorrelated relationship was absent in anesthetized rats even with global signal correction, further supporting its functional significance. Establishing negative RSFC independent of data preprocessing methods will significantly enhance the applicability of RSFC in better understanding neural circuitries and brain networks. In addition, combining the neurobiological data of the IL-amygdala circuit in rodents, the finding of the present study will enable further investigation of the neurobiological basis underlying anticorrelation.     

利用静息态功能磁共振成像研究缺血性脑卒中患者康复治疗后运动功能网络连接的变化

目的利用静息态功能磁共振成像技术研究缺血性脑卒中患者康复治疗前后运动功能网络连接变化的特点。方法对2例符合亚急性缺血性脑卒中影像学诊断标准的患者在功能性电刺激康复治疗前后各进行一次静息态功能磁共振扫描,比较两次扫描的运动脑区功能连接的差异。结果康复后患者上肢运动功能改善;与康复治疗前相比,康复治疗后左侧和右侧的运动皮层功能连接均降低,左侧和右侧的运动皮层功能连接系数降低值与脑卒中患者上肢运动功能以及日常生活能力的改善程度相关。结论缺血性脑卒中患者上肢运动功能改善后,即康复后患侧脑区对健侧脑区依赖性减低,并且功能连接系数的降低与脑卒中患者上肢运动功能的改善相关。     

Mapping resting-state functional connectivity using perfusion MRI

Resting-state, low-frequency (<0.08 Hz) fluctuations of blood oxygenation level-dependent (BOLD) magnetic resonance signal have been shown to exhibit high correlation among functionally connected regions. However, correlations of cerebral blood flow (CBF) fluctuations during the resting state have not been extensively studied. The main challenges of using arterial spin labeling perfusion magnetic resonance imaging to detect CBF fluctuations are low sensitivity, low temporal resolution, and contamination from BOLD. This work demonstrates CBF-based quantitative functional connectivity mapping by combining continuous arterial spin labeling (CASL) with a neck labeling coil and a multi-channel receiver coil to achieve high perfusion sensitivity. In order to reduce BOLD contamination, the CBF signal was extracted from the CASL signal time course by high frequency filtering. This processing strategy is compatible with sinc interpolation for reducing the timing mismatch between control and label images and has the flexibility of choosing an optimal filter cutoff frequency to minimize BOLD fluctuations. Most subjects studied showed high CBF correlation in bilateral sensorimotor areas with good suppression of BOLD contamination. Root-mean-square CBF fluctuation contributing to bilateral correlation was estimated to be 29+/-19% (N=13) of the baseline perfusion, while BOLD fluctuation was 0.26+/-0.14% of the mean intensity (at 3 T and 12.5 ms echo time).     

Small-world and scale-free organization of voxel-based resting-state functional connectivity in the human brain

The brain is a complex dynamic system of functionally connected regions. Graph theory has been successfully used to describe the organization of such dynamic systems. Recent resting-state fMRI studies have suggested that inter-regional functional connectivity shows a small-world topology, indicating an organization of the brain in highly clustered sub-networks, combined with a high level of global connectivity. In addition, a few studies have investigated a possible scale-free topology of the human brain, but the results of these studies have been inconclusive. These studies have mainly focused on inter-regional connectivity, representing the brain as a network of brain regions, requiring an arbitrary definition of such regions. However, using a voxel-wise approach allows for the model-free examination of both inter-regional as well as intra-regional connectivity and might reveal new information on network organization. Especially, a voxel-based study could give information about a possible scale-free organization of functional connectivity in the human brain. Resting-state 3 Tesla fMRI recordings of 28 healthy subjects were acquired and individual connectivity graphs were formed out of all cortical and sub-cortical voxels with connections reflecting inter-voxel functional connectivity. Graph characteristics from these connectivity networks were computed. The clustering-coefficient of these networks turned out to be much higher than the clustering-coefficient of comparable random graphs, together with a short average path length, indicating a small-world organization. Furthermore, the connectivity distribution of the number of inter-voxel connections followed a power-law scaling with an exponent close to 2, suggesting a scale-free network topology. Our findings suggest a combined small-world and scale-free organization of the functionally connected human brain. The results are interpreted as evidence for a highly efficient organization of the functionally connected brain, in which voxels are mostly connected with their direct neighbors forming clustered sub-networks, which are held together by a small number of highly connected hub-voxels that ensure a high level of overall connectivity.     

功能磁共振成像评价帕金森患者静息状态下脑功能连接

目的 采用功能磁共振成像(fMRI)评价帕金森病(PD)患者静息状态下脑功能连接的特点. 方法 对14例符合PD诊断标准的患者及14名健康者行静息态脑fMRI,选双侧壳核为感兴趣区,PD患者与正常对照组间脑功能连接的差异用随机效应两样本t检验.结果 与正常对照组相比,PD患者在静息状态下前额叶中内侧、双侧尾状核头部、左侧脑岛、左侧梭状回等脑区功能连接减低;双侧小脑半球、双侧舌回、双侧颞中回、右中央前回、右侧额上回、右侧额下回、右侧扣带回后部、左侧额中回等脑区功能连接增强.结论 PD患者在静息状态下存在异常的脑功能连接网络.     

Dynamic functional connectivity revealed by resting-state functional near-infrared spectroscopy

The brain is a complex network with time-varying functional connectivity (FC) and network organization. However, it remains largely unknown whether resting-state fNIRS measurements can be used to characterize dynamic characteristics of intrinsic brain organization. In this study, for the first time, we used the whole-cortical fNIRS time series and a sliding-window correlation approach to demonstrate that fNIRS measurement can be ultimately used to quantify the dynamic characteristics of resting-state brain connectivity. Our results reveal that the fNIRS-derived FC is time-varying, and the variability strength (Q) is correlated negatively with the time-averaged, static FC. Furthermore, the Q values also show significant differences in connectivity between different spatial locations (e.g., intrahemispheric and homotopic connections). The findings are reproducible across both sliding-window lengths and different brain scanning sessions, suggesting that the dynamic characteristics in fNIRS-derived cerebral functional correlation results from true cerebral fluctuation.OCIS codes: (170.2655) Functional monitoring and imaging, (170.5380) Physiology, (170.3880) Medical and biological imaging     

Exploring resting-state functional connectivity with total interdependence

Resting-state fMRI has become a powerful tool for studying network mechanisms of normal brain functioning and its impairments by neurological and psychiatric disorders. Analytically, independent component analysis and seed-based cross correlation are the main methods for assessing the connectivity of resting-state fMRI time series. A feature common to both methods is that they exploit the covariation structures of contemporaneously (zero-lag) measured data but ignore temporal relations that extend beyond the zero-lag. To examine whether data covariations across different lags can contribute to our understanding of functional brain networks, a measure that can uncover the overall temporal relationship between two resting-state BOLD signals is needed. In this paper we propose such a measure referred as total interdependence (TI). Comparing TI with zero-lag cross correlation (CC) we report three results. First, when combined with a random permutation procedure, TI can reveal the amount of temporal relationship between two resting-state BOLD time series that is not captured by CC. Second, comparing resting-state data with task-state data recorded in the same scanning session, we demonstrate that the resting-state functional networks constructed with TI match more precisely the networks activated by the task. Third, TI is shown to be more statistically sensitive than CC and provides better feature vectors for network clustering analysis.     

MRI观察精神分裂症静息态下小脑功能连接和解剖连接

目的 应用静息态功能磁共振成像(fMRI)和扩散张量成像(DTI)观察精神分裂症患者与正常人小脑功能连接与解剖连接的差异。方法 分别对10例精神分裂症患者(精神分裂组)及14名健康对照者(正常对照组)行静息态脑fMRI和DTI。对数据进行后处理后得到功能连接的相关系数r值及小脑中脚的平均FA值,应用双样本t检验比较组间差异,并对两种数据进行相关性检验。结果 ①精神分裂组与左侧小脑功能连接改变显著的区域为双侧舌回、右侧额中回、双侧缘上回和左侧小脑(P<0.001,未校正);与右侧小脑功能连接改变显著的区域为双侧舌回、左侧中央前回和左侧缘上回(P<0.001,未校正);②精神分裂组左侧小脑中脚的FA值显著降低(P<0.05);③精神分裂组右侧小脑-右侧舌回的连接强度与右侧小脑中脚的FA值呈显著正相关(r=0.84,P<0.05)。结论 联合运用多种成像方式可能为理解小脑在精神分裂症病理生理学中的作用提供新的方向;精神分裂症患者静息态下小脑与大脑皮层某些区域的连接降低和小脑中脚局部白质纤维完整性受损的同时出现以及二者之间的相关性提示功能连接与解剖解剖之间存在密切关系。     

Addiction related alteration in resting-state brain connectivity

It is widely accepted that addictive drug use is related to abnormal functional organization in the user's brain. The present study aimed to identify this type of abnormality within the brain networks implicated in addiction by resting-state functional connectivity measured with functional magnetic resonance imaging (fMRI). With fMRI data acquired during resting state from 14 chronic heroin users (12 of whom were being treated with methadone) and 13 non-addicted controls, we investigated the addiction related alteration in functional connectivity between the regions in the circuits implicated in addiction with seed-based correlation analysis. Compared with controls, chronic heroin users showed increased functional connectivity between nucleus accumbens and ventral/rostral anterior cingulate cortex (ACC), between nucleus accumbens and orbital frontal cortex (OFC), and between amygdala and OFC and reduced functional connectivity between prefrontal cortex and OFC and between prefrontal cortex and ACC. These observations of altered resting-state functional connectivity suggested abnormal functional organization in the addicted brain and may provide additional evidence supporting the theory of addiction that emphasizes enhanced salience value of a drug and its related cues but weakened cognitive control in the addictive state.