静息状态默认脑活动网络的初步检验——视觉呈现语言任务

目的：利用fMRI技术初步检验静息状态人脑默认活动假说及其脑区网络组成与刺激呈现通道的关系。方法：13名健康成年志愿者参加实验。每位受试者进行2次fMRI实验，任务通过视觉呈现。实验1（简单任务）任务期要求受试者注视无意义假词并默述；实验2（复杂任务）要求受试者完成动词产生任务。注视显示器上交替出现的“＋”及“＋＋＋”作为控制任务。利用SPM99软件进行数据处理。先分析单个被试，然后行组间比较。采用反减法获得负激活图，对有关脑区的反应特性做进一步分析。结果：实验1和实验2负激活脑区大部分相同，主要包括扣带回后部／楔前叶（BA31／30）、扣带回前部（BA24／32）、右侧颞上回（BA8）、左侧颞上回（BA8）、右颞下回前部（BA20）、左颞下回前部（BA20）、右侧顶下小叶（BA39／40）、左侧顶下小叶（BA39／40）。这些脑区的BOLD反应曲线呈负性变化，扣带回后部的负激活强度复杂任务时强于简单任务。结论：本研究初步验证了静息状态人脑默认活动假说及其负激活程度与任务难度的相关性。     

正常老年人静息状态脑功能磁共振的默认网络研究

目的 探讨正常老年人静息状态下的功能磁共振(fMRI)默认网络结构及意义.方法 正常健康老年受试者18人,接受静息fMRI扫描;通过时程相关方法检测fMRI数据低频波动信号中以后扣带回为种子区的默认网络,经SPM2软件单样本t检验,激活脑区周值设为经校正的P<0.001,激活像素范围>5.结果 与后扣带回相关的静息状态网络连接的脑区有:前额叶内侧区、海马、颞极、颞中上回、丘脑枕部、楔叶及楔前叶、部分视皮层、顶下小叶.海马区和顶下小叶呈侧化性激活.结论 正常老年人存在基本完整的静息状态fMRI默认网络结构,其部分呈侧化性可能是与老年期脑功能重塑有关.     

麻醉大鼠皮层及纹状体静息态脑功能网络连接

目的 以功能连接分析方法探讨大鼠麻醉状态和呼吸、心跳消失早期状态不同脑部位静息态自主性BOLD低频振荡(LFBF)信号的变化。 方法 对SD大鼠20只,于吸入麻醉后应用7.0T小动物磁共振仪行MRI,采集鼠脑解剖及功能成像数据;处死大鼠,呼吸、心跳停止5 min后以相同方法行鼠脑MRI;分别以大脑皮层和纹状体为ROI,以功能连接分析方法行脑功能相关性分析。 结果 麻醉状态下皮层相关性强于纹状体,信号差异范围以皮层为主;呼吸、心跳停止早期皮层与纹状体相关性差异变小,信号差异以皮层之外的区域为主;相应ROI内两种状态相关系数差异有统计学意义。 结论 麻醉状态下大鼠脑功能活动网络依然存在。LFBF信号蕴含着神经活动的生理性信息,可能为研究局限性脑缺血早期脑神经活动变化及预后评估提供一种新的技术。     

帕金森病静息态脑默认状态网络的观察

目的 应用功能连接MR成像技术观察帕金森病(PD)患者静息态脑默认状态网络的改变.方法 选择14例PD患者和14名健康志愿者,以双侧后扣带回作为种子点,分别进行静息态脑功能磁共振扫描,分析PD患者与健康志愿者的脑功能连接情况和差异. 结果与健康志愿组相比,PD患者的一些脑区存在异常功能连接,具体表现为:左顶下小叶、右侧楔前叶、前额叶中内侧、左侧颞上回等脑区与后扣带回功能连接减低;左侧小脑半球、左侧中央后回、左侧顶上小叶、左侧楔前叶、右侧颞下回、右侧楔叶、右侧舌回、左侧颞中回等脑区与后扣带回功能连接增强. 结论 静息态下帕金森病患者默认状态网络内脑区间的连接功能存在异常.     

复发性孤立性视神经炎患者初级视觉皮层功能连接的静息态fMRI

目的 采用静息态功能磁共振成像（rs-fMRI）技术,观察复发性孤立性视神经炎（RION）患者初级视觉皮层（V1）与全脑功能连接的改变。方法 收集45例RION患者（RION组）及45名年龄、性别相匹配的健康志愿者（正常对照组）的临床资料,并行常规头部MRI及rs-fMRI,选取V1为种子点,采用统计参数图5（SPM5）分析其与全脑的功能连接,比较两组数据的差异,并将RION组功能连接异常的脑区与其视力、病程及认知功能评分（PASAT）进行相关性分析。结果 与正常对照组相比,RION组左侧额中回、双侧枕叶舌回、右侧颞中回及右侧顶下小叶与V1的功能连接明显减低;双侧楔前叶、右侧额前回、左侧顶下小叶及右侧岛叶与V1的功能连接明显增强,且差异均有统计学意义（P均<0.01）。右侧顶下小叶及右侧额前回的功能连接异常与PASAT评分呈正相关;左侧额中回的功能连接异常与患者视力呈正相关。结论 rs-fMRI可检测出RION患者与V1区功能连接异常的脑区,并且显示与视力、病程及认知功能评分相关的脑区,可为临床探索RION功能连接异常提供客观依据。     

基于静息态功能磁共振尼古丁依赖者小脑-皮层间功能连接的研究

目的本研究采用静息态功能磁共振成像(resting-state functional magnetic resonance imaging,rs-fMRI)的技术,分析尼古丁依赖者在静息状态下小脑-皮层间功能连接(functional connectivity,FC)的异常改变.材料与方法通过网络平台招募117例尼古丁依赖者和52名年龄和教育程度相匹配的不吸烟志愿者并采集静息状态功能磁共振成像数据.通过回顾性研究,选取双侧小脑CruspⅠ为感兴趣区(region of interest,ROI),计算ROI与全脑的功能连接,探究两组小脑-皮层间功能连接的差异.结果与健康对照组相比,尼古丁依赖者左侧小脑CrusⅠ与默认网络(default mode network,DMN)、运动协调和感觉相关的脑区之间的功能连接显著增高(t=3.56,团块体素≥20).尼古丁依赖者右侧小脑CrusⅠ与皮层的功能连接较健康对照组无显著差异.结论与健康对照组相比,尼古丁依赖者存在多个小脑-皮层间功能连接的异常,强调了小脑的非运动功能,说明小脑参与尼古丁依赖的神经生物学机制并发挥了作用,并在一定程度上解释了尼古丁依赖者自动吸烟行为和认知、注意的缺陷.     

前注意视觉皮层脑功能磁共振成像

目的 探讨前注意视觉皮层的非注意视觉偏差刺激自动加工脑功能解剖的分布及意义。方法 对20名健康右利手男性,采用经典oddball被动范式给予非注意视觉刺激,标准刺激为红色方块,概率为80%,偏差刺激为绿色方块,概率为20%,观察功能MRI影像学表现。结果 最终分析15名被试,fMRI检查前、中、后的按键正确率均≥95%,反应时间差异无统计学意义(P=0.470)。fMRI显示右侧梭状回(枕颞内侧回)、右侧部分颞叶、枕叶及海马旁回,左侧枕叶,双侧额上回、双侧额中回及左侧中央前回/后回脑激活区BOLD信号在偏差刺激出现后明显升高。结论 fMRI可以清楚显示前注意视觉皮层功能解剖分布,为临床诊断前注意视觉皮层受损情况提供更加直观的检查方式,为疾病研究提供相应的参考信息。     

脑白质疏松患者静息态脑网络磁共振成像的研究

目的观察脑白质疏松(LA)患者与健康人静息态脑网络的差异。方法分别对根据临床诊断的31例LA患者及27名年龄匹配的健康对照者进行静息态功能磁共振扫描,采用独立成分分析法分离静息状态专属性功能脑网络。结果患者组及对照组中均发现与以往文献报道相同的静息网络。两者的脑激活区域基本一致,但患者组网络成分的激活程度均较对照组低,包括楔前叶、扣带回后部、颞上回、顶上回、中央前回、中央后回、岛叶、前额叶皮质等。结论 LA患者与健康人在脑静息网络激活程度上存在显著差异。     

静息态功能磁共振成像观察正常人听觉皮层功能

目的 探讨正常人听觉皮层与全脑的正相关及负相关的功能连接.方法 采用静息态下平面回波成像技术采集44名健康受试者fMRI数据,分别以左侧及右侧AⅠ区为种子点,用功能连接的方法观察左、右大脑初级听觉皮层与全脑的正相关及负相关功能连接脑图.结果 分别以双侧AⅠ区为种子点时,正激活的脑网络主要包含双侧AⅠ、AⅡ、岛叶、辅助运动区及扣带回,以同侧为主;与右侧AⅠ区相关的正激活脑区还包括同侧背侧丘脑.与双侧AⅠ区相关的负激活脑网络与脑默认网络大体一致,主要包括双侧后扣带回/楔前叶、额叶内侧回、顶下小叶,双侧小脑半球可见明显激活.结论 静息态磁共振功能连接可满意显示听觉皮层的连接脑图.正相关功能连接主要局限在听觉系统内,负相关功能连接类似于默认网络.     

静息态脑功能磁共振成像的研究进展

人脑是目前所知的最完善、最复杂的动态信息处理系统。脑功能磁共振成像（fonctional Magnetic Resonance Imaging,f MRI）是一种新型的髙效的无辐射非介入性损伤的成像技术,现已广泛应用于脑功能研究[1]。近年来静息态脑功能磁共振成像（resting-state functional MRI,rf MRI）日益受到大家的关注,广泛应用于神经心理学和神经系统疾病影像学方面的基础与临床研究。     

Functional connectivity mapping of the human precuneus by resting state fMRI

Precuneus responds to a wide range of cognitive processes. Here, we examined how the patterns of resting state connectivity may define functional subregions in the precuneus. Using a K-means algorithm to cluster the whole-brain “correlograms” of the precuneus in 225 adult individuals, we corroborated the dorsal-anterior, dorsal-posterior, and ventral subregions, each involved in spatially guided behaviors, mental imagery, and episodic memory as well as self-related processing, with the ventral precuneus being part of the default mode network, as described extensively in earlier work. Furthermore, we showed that the lateral/medial volumes of dorsal anterior and dorsal posterior precuneus are each connected with areas of motor execution/attention and motor/visual imagery, respectively. Compared to the ventral precuneus, the dorsal precuneus showed greater connectivity with occipital and posterior parietal cortices, but less connectivity with the medial superior frontal and orbitofrontal gyri, anterior cingulate cortex as well as the parahippocampus. Compared to dorsal-posterior and ventral precuneus, the dorsal-anterior precuneus showed greater connectivity with the somatomotor cortex, as well as the insula, supramarginal, Heschl's, and superior temporal gyri, but less connectivity with the angular gyrus. Compared to ventral and dorsal-anterior precuneus, dorsal-posterior precuneus showed greater connectivity with the middle frontal gyrus. Notably, the precuneus as a whole has negative connectivity with the amygdala and the lateral and inferior orbital frontal gyri. Finally, men and women differed in the connectivity of precuneus. Men and women each showed greater connectivity with the dorsal precuneus in the cuneus and medial thalamus, respectively. Women also showed greater connectivity with ventral precuneus in the hippocampus/parahippocampus, middle/anterior cingulate gyrus, and middle occipital gyrus, compared to men. Taken together, these new findings may provide a useful platform upon which to further investigate sex-specific functional neuroanatomy of the precuneus and to elucidate the pathology of many neurological illnesses.     

Investigating the consistency of brain activation using individual trial analysis of high-resolution fMRI in the human primary visual cortex

Conventional functional magnetic resonance imaging using blood oxygenation level dependent contrast requires signal averaging and statistical methods to detect activation. Signal averaging implicitly assumes that brain activation in response to a stimulus is reproducible on the scale of the imaging voxel. This assumption is examined in the absence of averaging by analyzing individual trials of individual voxels that approach the size of the functional unit, the cortical column, in the human primary visual cortex. In the absence of spatial and temporal averaging, even highly active voxels demonstrate inconsistent activation to the same repeated stimulus despite consistent behavioral responses. This observation implies a variable selection of suitable cortical columns from a population of available functional units to produce consistent perception of the stimulus. The implication of this observation for neuroplasticity and behavioral consistency at the level of functional units is discussed.     

Differential effects of distraction during working memory on delay-period activity in the prefrontal cortex and the visual association cortex

Maintaining relevant information for later use is a critical aspect of working memory (WM). The lateral prefrontal cortex (PFC) and posterior sensory cortical areas appear to be important in supporting maintenance. However, the relative and unique contributions of these areas remain unclear. We have designed a WM paradigm with distraction to probe the contents of maintenance representations in these regions. During delayed recognition trials of faces, selective interference was evident behaviorally with face distraction leading to significantly worse performance than with scene distraction. Event-related fMRI of the human brain showed that maintenance activity in the lateral PFC, but not in visual association cortex (VAC), was selectively disrupted by face distraction. Additionally, the functional connectivity between the lateral PFC and the VAC was perturbed during these trials. We propose a hierarchical and distributed model of active maintenance in which the lateral PFC codes for abstracted mnemonic information, while sensory areas represent specific features of the memoranda. Furthermore, persistent coactivation between the PFC and sensory areas may be a mechanism by which information is actively maintained.     

静息状态默认脑活动网络的初步检验——听觉呈现语言任务

目的利用fMRI技术,通过听觉呈现语言任务,探讨刺激呈现通道对负激活脑区的影响,进一步检验静息状态人脑默认活动假说。方法13名健康成年志愿者参加实验。进行2次fMRI实验。实验1（简单任务）任务期要求受试者听无意义假词;实验2（复杂任务）要求受试者听真词并作词语属性判断（具体或抽象）。静息期要求受试者闭眼、静卧,不要做任何主动思维活动。利用SPM2软件进行数据处理。先分析单个被试,然后行组间比较。采用反减法获得负激活图。并把本次实验结果与以往视觉呈现任务结果进行比较。结果初级视觉皮层与初级听觉皮层的负激活存在明显的通道依赖性,听觉呈现刺激引起视觉皮层负激活,视觉呈现刺激时听觉皮层表现为负激活。非任务依赖性负激活脑区包括扣带回后部/楔前叶（BA31/30）、扣带回前部（BA24/32）、两侧颞上回（BA8）、两颞下回前部（BA20）、两侧顶下小叶（BA39/40）。这些区域的负激活与刺激呈现通道方式及特定刺激任务无关。该负激活脑区模式与人类默认脑活动网络基本一致。结论刺激呈现通道是影响任务依赖性负激活的因素之一,探讨负激活问题时应该考虑到这一因素。同时,本研究进一步验证了静息状态时人脑默认活动假说。     

Attentional modulation of stimulus representation in human fronto-parietal cortex

Evidence from primates suggests that prefrontal and parietal regions selectively represent information that is relevant for current behavior. In humans, whilst functional imaging has shown that fronto-parietal areas are activated by a range of different cognitive demands, the actual content of representation remains unclear. The current report describes two studies designed to address this issue using fMRI adaptation. In both studies, participants completed a delayed matching task where they attended to either the color or the shape of a series of sample stimuli and indicated whether occasional test stimuli matched the preceding sample on the attended dimension. Whole brain contrasts showed that changes to the value of the currently attended dimension produced significantly greater responses in frontal and parietal areas than events where the value was repeated. In addition, prefrontal and parietal regions of interest showed strong interactions between the currently attended dimension and the type of stimulus change, reflecting an attentional modulation of responses to stimulus change. Further comparisons suggested that the differences between attended changes and stimulus repetitions carried information about specific stimulus values, and did not simply reflect a generic response to attended changes.     

Anticorrelations in resting state networks without global signal regression

Anticorrelated relationships in spontaneous signal fluctuation have been previously observed in resting-state functional magnetic resonance imaging (fMRI). In particular, it was proposed that there exists two systems in the brain that are intrinsically organized into anticorrelated networks, the default mode network, which usually exhibits task-related deactivations, and the task-positive network, which usually exhibits task-related activations during tasks that demands external attention. However, it is currently under debate whether the anticorrelations observed in resting state fMRI were valid or were instead artificially introduced by global signal regression, a common preprocessing technique to remove physiological and other noise in resting-state fMRI signal. We examined positive and negative correlations in resting-state connectivity using two different preprocessing methods: a component base noise reduction method (CompCor, Behzadi et al., 2007), in which principal components from noise regions-of-interest were removed, and the global signal regression method. Robust anticorrelations between a default mode network seed region in the medial prefrontal cortex and regions of the task-positive network were observed under both methods. Specificity of the anticorrelations was similar between the two methods. Specificity and sensitivity for positive correlations were higher under CompCor compared to the global regression method. Our results suggest that anticorrelations observed in resting-state connectivity are not an artifact introduced by global signal regression and might have biological origins, and that the CompCor method can be used to examine valid anticorrelations during rest.     

Characterizing dynamic functional connectivity in the resting brain using variable parameter regression and Kalman filtering approaches

The cognitive activity of the human brain benefits from the functional connectivity of multiple brain regions that form specific, functional brain networks. Recent studies have indicated that the relationship between brain regions can be investigated by examining the temporal interaction (known as functional connectivity) of spontaneous blood oxygen level-dependent (BOLD) signals derived from resting-state functional MRI. Most of these studies plausibly assumed that inter-regional interactions were temporally stationary. However, little is known about the dynamic characteristics of resting-state functional connectivity (RSFC). In this study, we thoroughly examined this question within and between multiple functional brain networks. Twenty-two healthy subjects were scanned in a resting state. Several of the RSFC networks observed, including the default-mode, motor, attention, memory, auditory, visual, language and subcortical networks, were first identified using a conventional voxel-wise correlation analysis with predefined region of interests (ROIs). Then, a variable parameter regression model combined with the Kalman filtering method was employed to detect the dynamic interactions between each ROI and all other brain voxels within each of the RSFC maps extracted above. Experimental results revealed that the functional interactions within each RSFC map showed time-varying properties, and that approximately 10-20% of the voxels within each RSFC map showed significant functional connectivity to each ROI during the scanning session. This dynamic pattern was also observed for the interactions between different functional networks. In addition, the spatial pattern of dynamic connectivity maps obtained from neighboring time points had a high similarity. Overall, this study provides insights into the dynamic properties of resting-state functional networks.     

人脑对事件相关食物视觉刺激反应的功能磁共振成像的初步研究

目的通过功能磁共振成像(fMRI)初步研究人脑对事件相关食物视觉刺激反应.方法本研究利用fMRI技术具有时间分辨率高、对人体无创并且可以对单例数据处理分析的优势,采用平面回波成像(EPI)序列,检测在饥饿状态下,人脑对事件相关食物视觉刺激反应.实验中2名健康志愿受试者,选择事件相关任务模式禁食12 h后扫描.扫描的同时接受随机播放的食物图片、非食物图片和空白模糊图片的视觉刺激.用SPM 2软件处理功能成像数据,对由三类图片所引发的感兴趣区(ROI)做相关t检验统计.结果与食物渴求相关的脑区分布在杏仁核、眶额皮质以及枕叶皮质,与既往的正电子放射扫描成像(PET)实验结果相符.结论确定与食物渴求相关的奖赏通路,对于了解人类在饥饿状态下对食物渴求的复杂认知规律,为进一步寻找有效调控人类摄食行为的手段有重要意义.     

fMRI resting state networks define distinct modes of long-distance interactions in the human brain

Functional magnetic resonance imaging (fMRI) studies of the human brain have suggested that low-frequency fluctuations in resting fMRI data collected using blood oxygen level dependent (BOLD) contrast correspond to functionally relevant resting state networks (RSNs). Whether the fluctuations of resting fMRI signal in RSNs are a direct consequence of neocortical neuronal activity or are low-frequency artifacts due to other physiological processes (e.g., autonomically driven fluctuations in cerebral blood flow) is uncertain. In order to investigate further these fluctuations, we have characterized their spatial and temporal properties using probabilistic independent component analysis (PICA), a robust approach to RSN identification. Here, we provide evidence that: i. RSNs are not caused by signal artifacts due to low sampling rate (aliasing); ii. they are localized primarily to the cerebral cortex; iii. similar RSNs also can be identified in perfusion fMRI data; and iv. at least 5 distinct RSN patterns are reproducible across different subjects. The RSNs appear to reflect "default" interactions related to functional networks related to those recruited by specific types of cognitive processes. RSNs are a major source of non-modeled signal in BOLD fMRI data, so a full understanding of their dynamics will improve the interpretation of functional brain imaging studies more generally. Because RSNs reflect interactions in cognitively relevant functional networks, they offer a new approach to the characterization of state changes with pathology and the effects of drugs.     

Retinotopic maps and hemodynamic delays in the human visual cortex measured using arterial spin labeling

Cortical representations of the visual field are organized retinotopically, such that nearby neurons have receptive fields at nearby locations in the image. Many studies have used blood oxygenation level-dependent (BOLD) fMRI to non-invasively construct retinotopic maps in humans. The accuracy of the maps depends on the spatial extent of the metabolic and hemodynamic changes induced by the neural activity. Several studies using gradient-echo MRI at 1.5 T and 3 T showed that most of the BOLD signal originates from veins, which might lead to a spatial displacement from the actual site of neuronal activation, thus reducing the specificity of the functional localization. In contrast to BOLD signal, cerebral blood flow (CBF) as measured using arterial spin labeling (ASL) is less or not at all affected by remote draining veins, and therefore spatially and temporally more closely linked to the underlying neural activity. In the present study, we determined retinotopic maps in the human brain using CBF as well as using BOLD signal in order to compare their spatial relationship and the temporal delays of each imaging modality for visual areas V1, V2, V3, hV4 and V3AB. We tested the robustness and reproducibility of the maps across different sessions, calculated the overlap as well as signal delay times across visual areas. While area boundaries were relatively well preserved, we found systematic differences of response latencies between CBF and the BOLD signal between areas. In summary, CBF data obtained using ASL allows reliable retinotopic maps to be constructed; this approach is, therefore, suitable for studying visual areas especially in close proximity to large veins where the BOLD signal is spatially inaccurate.