全面性棘慢复合波相关神经网络的EEG-fMRI研究

全面性癫痫的脑电图(EEG)呈全面性棘慢复合波放电(GSWDs),近来研究表明GSWDs并非"全面地"累及整个大脑,而是与特异的神经网络相关。同步脑电图联合功能磁共振(EEG-fMRI)技术可无创、高时空分辨率地了解痫性电活动时各脑区的代谢功能变化。EEG-fMRI研究已发现丘脑-基底节-皮质网络在GSWDs的产生与维持中起重要作用。与GSWDs相关的功能磁共振(fMRI)信号变化规律:前额叶、额顶叶、后扣带回、楔前叶出现相似的负激活(deactivation)信号,丘脑出现较为一致的激活(activation)信号,基底节出现负激活信号。进一步研究发现,fMRI信号随GSWDs出现的时程动态变化,皮质神经元活动可能先于丘脑出现,但不同EEG-fMRI研究的皮质激活部位存在个体化表现,散在地分布于额叶、顶叶等皮质区域。进一步发展更加复杂的分析方法揭示fMRI信号的时程变化规律,研究GSWDs产生的起始、传导和维持涉及的神经网络,揭示全面性癫痫的行为表现、药物治疗反应与神经网络的关系是未来EEG-fMRI研究的方向。     

基于局部一致性(ReHo)方法的慢性吸烟静息状态功能磁共振(fMRI)研究

目的:探讨慢性吸烟者静息状态下的脑功能活动情况。方法:采用局部一致性(ReHo)方法,对44名慢性吸烟者和44名与之相匹配的不吸烟的健康志愿者在静息状态下脑功能活动情况进行比较分析。结果:与不吸烟者相比,慢性吸烟者静息状态右侧额下回BOLD信号ReHo降低,左侧顶上回BOLD信号ReHo增强(P<0.05,纠正后,cluster水平)。结论:研究结果提示慢性吸烟会导致额叶和顶叶脑区功能活动的改变。     

健康成人吞咽活动脑功能区的功能磁共振成像研究

目的 利用脑功能磁共振成像(fMRI)技术研究健康成人不同吞咽任务时激活脑区的特点.方法 8名健康志愿者参与实验性自主和反射性吞咽任务的fMRI研究.采用SPM2软件对功能成像数据进行处理及图像显示.配对t检验用于比较2种吞咽任务激活脑区的容积及信号值大小.结果 自主吞咽任务激活脑区有双侧初级感觉运动皮质、运动前区、前扣带回等.反射性吞咽任务相关脑区有双侧初级感觉皮层、双侧额盖、双侧顶后区.自主性吞咽激活双侧半球容积(体素)分别为1213±110(左)、1969±133(右).反射吞咽激活双侧半球容积(体素)分别为488±45(左)、398±35(右).自主性咽水双侧感觉运动区信号增加值分别为4.4±0.4(左)、4.1±0.2(右);双侧岛叶容积为1.2±0.5(左)、1.5±0.6(右).反射性咽水双侧感觉运动区信号增加值分别为2.6±0.3(左)、2.5±1.2(右);双侧岛叶信号增加值为0.6±0.4(左)、0.2±0.1(右).自主吞咽激活双侧半球容积、感觉运动区及岛叶信号值均大于反射性吞咽(均为P<0.05).两种吞咽任务的偏侧性指数(LI)值分别为(-16±9)%和(11±5)%.结论 自主吞咽任务激活脑区数量及容积大于反射性吞咽任务.两种吞咽任务激活脑区的不同与自主吞咽过程中计划、发动、情感等多种高级脑活动有关.     

基于fMRI的原发全面性癫痫脑活动的局域一致性研究

癫痫是一种以神经活动同步性异常增高为特征的中枢神经系统疾病.我们利用基于局域一致性(regional homogeneity,ReHo)分析方法的功能磁共振成像(functional Magnetic Resonance Imaging, fMRI)技术对原发全面性癫痫(idiopathic generalized epilepsy, IGE)进行研究.观察IGE患者相比正常对照组局域一致性的改变情况.结果表明:在静息状态下,患者大脑的局域一致性在某些脑区较正常人低,主要集中在楔前叶、内侧前额叶、双侧颞叶、双侧额中回;另外,在某些脑区较正常人高,主要集中在底丘脑等中缝核团.提示该方法可检出癫痫活动造成的局部脑组织血氧水平依赖(blood oxygen level dependent, BOLD)信号同步性的改变,从而有助于原发全面性癫痫的病理生理机制的探索.     

正常中老年人词语联想任务功能磁共振成像研究

目的 采用功能磁共振成像(fMRI)技术对正常中老年人进行研究,检测与词语联想功能相关脑区的激活特点.方法 采用GE 1.5 T磁共振扫描仪对23例(男12例,女11例)正常中老年人行组块设计的词语联想任务fMRI研究.采用SPM 2软件进行数据处理和统计分析,通过组分析获得平均脑激活图,观察脑激活区的部位和激活强度.结果 12例符合入组条件,激活脑区为运动前区(PMC)、双侧额下回后部(Broca区及Broca镜像区)、双侧辅助运动区(SMA)、左侧顶后皮层、双侧岛叶、双侧扣带回前部、双侧基底节、左侧丘脑以及右侧小脑半球.全脑以左侧PMC激活强度最大.激活强度左侧大于右侧的脑区为额下回后部、背侧PMC及SMA;右侧大于左侧的脑区为腹侧PMC、岛叶、扣带回前部、基底节.结论 中老年人参与运动性语言表达的脑区,由包括Broca区在内的多个脑区组成复杂的神经网络,且相关脑区存在偏侧化现象,以左侧大脑半球和右侧小脑半球激活为主.     

基于ICA的颞叶癫痫背侧注意网络的研究

很多fMRI研究表明部分癫痫患者缺省模式网络存在中断现象,而对于颞叶癫痫背侧注意网络的研究几乎没有涉及。本研究尝试运用独立成分分析(independent component analysis,ICA)分离出16例单侧颞叶癫痫(temporal lobe epilepsy,TLE)患者和20例正常对照的背侧注意网络,并采用拟合度值(goodness-of-fit scores)分析对感兴趣成分进行挑选,将其结果进行组内分析和组间分析。结果表明:背侧注意网络分布于双侧顶内沟、额中回、额眼区、右侧小脑后叶等区域;颞叶癫痫患者的背侧注意网络相比正常人,大部分区域功能连接度下降,以双侧顶内沟、额中回、右侧小脑后叶区域显著,这可能是由于颞叶癫痫患者的大脑功能内源性组织发生破坏。拟合度值下降表明背侧注意网络激活区域为单侧TLE患者提供了一个灵敏的生物信号特征。     

视觉刺激状态下正常成人电针光明穴的脑功能性磁共振研究

目的:对比研究针刺足少阳胆经光明穴(GB37)与视觉刺激后引起的人脑血液动力学反应,探讨分析视觉刺激状态下针刺对脑功能活动区的影响。方法:25例健康志愿者随机分为无视觉刺激电针组(10例)与视觉刺激状态电针组(15例)。视觉刺激状态电针组15例健康自愿者中12例取得成功,并在2种不同的刺激模式(包括视觉刺激任务与视觉刺激状态下针刺光明穴)状态下进行血氧水平依赖性功能磁共振(BOLD-fMRI)实验;应用闪烁棋盘方格为视觉刺激任务,频率8Hz,最后以图像数据重组方法,检测受试者在接受视觉刺激任务与针刺状态时的大脑响应功能区的激活,并进行分析比较。结果:视觉刺激任务时见脑干、小脑后叶大面积激活、及边缘叶、海马、颞中回、颞下回激活;针刺状态时见顶叶中央后回、顶下小叶、顶叶楔前叶、额中回激活。在视觉刺激下时电针光明穴见额上回,额下回、顶叶楔前叶及枕叶舌回激活。结论:功能性磁共振技术可看出针刺后脑功能响应功能区的激活情况;视觉刺激的参与导致针刺脑激活区改变,且该变化具有重要的意义;针刺足少阳胆经光明穴对视觉系统转导通路整合有一定影响;此外,外界的刺激亦对针刺疗效可能有着显著的影响。     

精神分裂症静息状态下的功能磁共振成像研究

目的：利用功能磁共振成像（fMRI）和局部一致性（regional homogeneity，ReHo）方法探测精神分裂症患者在静息状态下是否存在脑功能异常。方法：对18例精神分裂症患者和18例正常对照进行静息状态的fMRI检查，应用ReHo方法处理fMRI数据。结果：与正常人相比，精神分裂症患者静息状态下脑的BOLD信号的ReHo普遍降低（P〈0．05）。ReHo降低的脑区有双侧额叶内侧回、颞上回、颞下回、枕中回、枕下回和小脑后叶；左侧扣带回前部、海马回、颞中回、中央后回和脑桥；右侧额上回、顶上小叶、楔前叶、中央旁小叶、中央前回和小脑蚓部。结论：精神分裂症患者在静息状态下即可能存在脑功能异常，ReHo可能有助于精神分裂症静息状态的理解。     

基于Granger因果分析的癫痫发作间歇期EEG在δ频段的功能连接模式

目的 应用频域Granger因果分析方法,研究颞叶癫痫发作间歇期16导脑电图(EEG)在与癫痫发作相关的δ频段的过度放电功能连接特性.方法 实验数据来自颞叶癫痫9例患者(6例左颞叶癫痫,3例右颞叶癫痫),9例正常对照受试者.记录每例颞叶癫痫受试者在发作间歇期的痫样放电、非痫样放电以及正常对照组的共3个状态的16导EEG;每个状态下各记录10个EEG数据段,每个数据段长度为20s,采样频率为200 Hz;应用带通滤波提取EEG的δ分量(1～4 Hz).应用频域Granger因果分析方法,分别计算痫样放电组、非痫样放电组和正常组10次记录的16通道EEGδ频段分量之间的频域因果度量平均值Iδ;分析以上3个组颞叶区(左颞叶癫痫:T3、T5,右颞叶癫痫:T4、T6)与额区(Fp1、Fp2、F3、F4)和顶区(C3、C4)之间EEG在δ频段的功能连接模式.结果 痫样放电组:下颞叶区(左下颞叶区T5,右下颞叶区T6)与额区、顶区之间Iδ在0.1323±0.0329～0.1670±0.0289;非痫样放电组:下颞叶区与额区、顶区之间的Iδ在0.0300±0.0130～0.0420±0.0072;正常对照组:下颞叶区与额区、顶区之间的Iδ在0.0153±0.0028～0.0193±0.0057.统计结果表明:痫样放电组下颞叶区与额区、顶区之间的Iδ值与非痫样放电组相比差异有统计学意义(P＜0.05),与正常对照组相比差异有统计学意义(P＜0.01);非痫样放电组下颞叶区与额叶、顶叶之间的Iδ值和正常对照组相比差异无统计学意义(P＞0.05).结论 颞叶癫痫发作间歇期在痫样放电状态下,EEGδ频段在下颞叶区与额区、顶区之间存在较强连接,过度放电从下颞叶区传递到额区和顶区.非痫样放电组和正常组的EEGδ频段,下颞叶区与额叶、顶叶之间连接弱,下颞叶区不是EEG信号传导的起始区.     

血氧水平依赖脑功能磁共振在精神障碍疾病中的应用

脑功能磁共振成像(fMRI)最主要的形式是血氧水平依赖磁共振成像(】BOLD-fMRI),根据神经元兴奋后局部氧耗与血流增幅不一致,用BOLD效应机制成像,间接显示神经元活动。BOLD-fMRI通过静息态和任务态两种模式,对精神疾病的研究已经不仅局限于研究特定脑区激活程度的差异,更逐渐关注分析各脑区间的神经环路和功能网络连接的变化。本文综述BOLD-fMRI成像原理、应用模式及在研究精神分裂症等常见精神障碍疾病脑区神经活动的相关性及功能连接。     

Brain areas activated in fMRI during self-regulation of slow cortical potentials (SCPs)

In humans, surface-negative slow cortical potentials (SCPs) originating in the apical dendritic layers of the neocortex reflect synchronized depolarization of large groups of neuronal assemblies. They are recorded during states of behavioural or cognitive preparation and during motivational states of apprehension and fear. Surface positive SCPs are thought to indicate reduction of cortical excitation of the underlying neural networks and appear during behavioural inhibition and motivational inertia (e.g. satiety). SCPs at the cortical surface constitute summated population activity of local field potentials (LFPs). SCPs and LFPs may share identical neural substrates. In this study the relationship between negative and positive SCPs and changes in the BOLD signal of the fMRI were examined in ten subjects who were trained to successfully self-regulate their SCPs. FMRI revealed that the generation of negativity (increased cortical excitation) was accompanied by widespread activation in central, pre-frontal, and parietal brain regions as well as the basal ganglia. Positivity (decreased cortical excitation) was associated with widespread deactivations in several cortical sites as well as some activation, primarily in frontal and parietal structures as well as insula and putamen. Regression analyses revealed that cortical positivity was predicted with high accuracy by pallidum and putamen activation and supplementary motor area (SMA) and motor cortex deactivation, while differentiation between cortical negativity and positivity was revealed primarily in parahippocampal regions. These data suggest that negative and positive electrocortical potential shifts in the EEG are related to distinct differences in cerebral activation detected by fMRI and support animal studies showing parallel activations in fMRI and neuroelectric recordings.Supported by the Deutsche Forschungsgemeinschaft (DFG)     

Neural networks involved in mathematical thinking: evidence from linear and non-linear analysis of electroencephalographic activity

Using linear and non-linear methods, electroencephalographic (EEG) signals were measured at various brain regions to provide information regarding patterns of local and coordinated activity during performance of three arithmetic tasks (number comparison, single-digit multiplication, and two-digit multiplication) and two control tasks that did not require arithmetic operations. It was hypothesized that these measures would reveal the engagement of local and increasingly complex cortical networks as a function of task specificity and complexity. Results indicated regionally increased neuronal signalling as a function of task complexity at frontal, temporal and parietal brain regions, although more robust task-related changes in EEG-indices of activation were derived over the left hemisphere. Both linear and non-linear indices of synchronization among EEG signals recorded from over different brain regions were consistent with the notion of more "local" processing for the number comparison task. Conversely, multiplication tasks were associated with a widespread pattern of distant signal synchronizations, which could potentially indicate increased demands for neural networks cooperation during performance of tasks that involve a greater number of cognitive operations.     

Negative BOLD Response to Interictal Epileptic Discharges in Focal Epilepsy

In EEG–fMRI studies, BOLD responses related to interictal epileptic discharges (IEDs) are most often the expected positive response (activation) but sometimes a surprising negative response (deactivation). The significance of deactivation in the region of IED generation is uncertain. The aim of this study was to determine if BOLD deactivation was caused by specific IED characteristics. Among focal epilepsy patients who underwent 3T EEG–fMRI from 2006 to 2011, those with negative BOLD having a maximum t-value in the IED generating region were selected. As controls, subjects with maximum activation in the IED generating region were selected. We established the relationship between the type of response (activation/deactivation) and (1) presence of slow wave in the IEDs, (2) lobe of epileptic focus, (3) occurrence as isolated events or bursts, (4) spatial extent of the EEG discharge. Fifteen patients with deactivation and 15 with activation were included. The IEDs were accompanied by a slow wave in 87 % of patients whose primary BOLD was a deactivation and only in 33 % of patients with activation. In the deactivation group, the epileptic focus was more frequently in the posterior quadrant and involved larger cortical areas, whereas in the activation group it was more frequently temporal. IEDs were more frequently of long duration in the deactivation group. The main factor responsible for focal deactivations is the presence of a slow wave, which is the likely electrographic correlate of prolonged inhibition. This adds a link to the relationship between electrophysiological and BOLD activities.     

正常人参数性数字n-back工作记忆任务的去激活网络:fMRI研究

目的:探讨工作记忆任务诱发去激活(Task induced deactivation,TID)脑区及其意义。方法:正常受试者35名,采用参数性数字n-back任务(n为1、2、3)行fMRI,0back作为对照任务。根据受试者在实验过程中3back任务的行为学表现,将准确率为≥85%的受试者纳入高执行表现正常受试者(High performing normal subjects,HPNS)组。采用SPM2软件进行功能数据预处理、统计分析和结果显示。结果:HPNS中TID脑区包括:前额叶皮层内侧部(medialprefrontal cortex,MPFC);扣带;右侧额下回(BA47);双侧颞叶多个脑区。在2back负载水平之内,随着负载增加,TID脑区去激活程度增加,但在2back负载之后,大多TID脑区的去激活呈平台期表现。结论:TID网络的存在对WM任务的正确执行是必须的。     

Age-related differences of saccade induced cortical activation

Recent functional MRI (fMRI) studies have described the increased task-related brain activation in older subjects during motor, cognitive and perceptual tasks. Age affects the ability to control saccadic eye movements. To investigate the age-related changes of oculomotor control, we studied the representation of saccades in 11 young (median age 29 years) and 11 older (median age 62 years) healthy individuals using fMRI. Brain activation was measured during a visually guided prosaccade trial. Differences in activation between rest and saccades as well as between younger and older subjects were assessed with statistical parametric mapping (SPM). In both age groups, activation of a frontoparietal network was observed. Older subjects showed increased activation compared to younger subjects with overactivation in bilateral parietal eye fields, the right frontal eye field, as well as in the right extrastriate cortex. We conclude that older adults increase activation in an extended oculomotor and visual network to maintain performance during simple prosaccades. This observation also underlines the importance of using appropriate age-matched control groups in fMRI studies after brain lesions.     

精神疲劳对工作记忆α振荡信息整合的影响

精神疲劳是一定时间内人们进行持续精神注意力的认知活动所体验到的一种生理、心理上的不适。认知活动依赖于大脑多个区域间的信息交流,相位同步作为大脑区域之间信息整合的重要机制,搭起大脑各区域间协同通信的桥梁。α振荡是神经元加工功能抑制的一种主动机制,而主动抑制在工作记忆的注意力分配中起着中心作用。利用自适应N-back实验诱发精神疲劳。采用改进型Sternberg范式作为工作记忆实验,记录精神疲劳前后工作记忆的脑电信号。采用相位同步分析和功率谱分析方法,对精神疲劳前后α振荡工作记忆编码期、保持期和提取期的脑电数据进行分析,研究精神疲劳对大脑信息整合的影响。结果发现, 精神疲劳后,整个工作记忆过程中脑区间的相位同步性显著增大,功率谱值有显著差异。其中,精神疲劳后的3个时期均出现额叶区域间和额枕区域间相位同步性的显著增加,编码期额叶区域间锁相值具有显著性增大的节点对有160个;保持期额叶区域间有222个,额叶、枕顶叶区域之间有65个;提取期额叶区域间有196个,额叶、枕顶叶区域之间有11个。编码期枕顶区出现显著的α振荡事件相关去同步(ERD)(PO8,P=0.048;Oz,P=0.036),额叶区出现α振荡事件相关同步(ERS)的趋势。保持期额叶出现显著的α振荡ERS(Fz,P=0.022),枕顶区有ERS的趋势。提取期额区(Fz,P=0.033)出现α振荡ERS,枕区(Oz,P=0.045)出现α振荡ERD。研究表明,精神疲劳会降低大脑脑区间的信息整合能力,降低大脑内的信息交流,α振荡的相位同步分析对解释精神疲劳对脑区间信息整合的机制有一定的帮助。     

Responses to rare visual target and distractor stimuli using event-related fMRI

Previous studies have found that the P300 or P3 event-related potential (ERP) component is useful in the diagnosis and treatment of many disorders that influence CNS function. However, the anatomic locations of brain regions involved in this response are not precisely known. In the present event-related functional magnetic resonance imaging (fMRI) study, methods of stimulus presentation, data acquisition, and data analysis were optimized for the detection of brain activity in response to stimuli presented in the three-stimulus oddball task. This paradigm involves the interleaved, pseudorandom presentation of single block-letter target and distractor stimuli that previously were found to generate the P3b and P3a ERP subcomponents, respectively, and frequent standard stimuli. Target stimuli evoked fMRI signal increases in multiple brain regions including the thalamus, the bilateral cerebellum, and the occipital-temporal cortex as well as bilateral superior, medial, inferior frontal, inferior parietal, superior temporal, precentral, postcentral, cingulate, insular, left middle temporal, and right middle frontal gyri. Distractor stimuli evoked an fMRI signal change bilaterally in inferior anterior cingulate, medial frontal, inferior frontal, and right superior frontal gyri, with additional activity in bilateral inferior parietal lobules, lateral cerebellar hemispheres and vermis, and left fusiform, middle occipital, and superior temporal gyri. Significant variation in the amplitude and polarity of distractor-evoked activity was observed across stimulus repetitions. No overlap was observed between target- and distractor-evoked activity. These event-related fMRI results shed light on the anatomy of responses to target and distractor stimuli that have proven useful in many ERP studies of healthy and clinically impaired populations.     

Information Transfer During a Transitive Reasoning Task

For about two decades now, the localization of the brain regions involved in reasoning processes is being investigated through fMRI studies, and it is known that for a transitive form of reasoning the frontal and parietal regions are most active. In contrast, less is known about the information exchange during the performance of such complex tasks. In this study, the propagation of brain activity during a transitive reasoning task was investigated and compared to the propagation during a simple memory task. We studied EEG transmission patterns obtained for physiological indicators of brain activity and determined whether there are frequency bands specifically related to this type of cognitive operations. The analysis was performed by means of the directed transfer function. The transmission patterns were determined in the theta, alpha and gamma bands. The results show stronger transmissions in theta and alpha bands from frontal to parietal as well as within frontal regions in reasoning trials comparing to memory trials. The increase in theta and alpha transmissions was accompanied by flows in gamma band from right posterior to left posterior and anterior sites. These results are consistent with previous neuroimaging (fMRI) data concerning fronto-parietal regions involvement in reasoning and working memory processes and also provide new evidence for the executive role of frontal theta waves in organizing the cognition.