人脑运动皮层功能磁共振成像研究

目的采用功能用磁共振成像（fMRI）回波平面（EPI）技术,研究人脑运动皮质血氧水平依赖（BOLD）的功能磁共振成像。方法27名正常健康志愿者,右手挤压橡皮圈,在运动和静止两种对比条件下,采集运动皮层的回波平面图像（BOLD-fMRI）。分析运动状态和非运动状态信号对比的脑功能图像。结果fMRI图像显示运动刺激下脑功能活动激活区主要位于对侧感觉运动皮质区、辅助运动区等。结论fMRI可用于研究活体人脑各功能区的活动,fMRI可对运动刺激下的人脑运动皮质进行初步定位。     

情感反应中杏仁核激活的磁共振功能成像

杏仁核是脑深部的灰质核团，在脑的情感加工过程中发挥重要作用，杏仁核在情感反应中的作用机制及与其它脑区之间的相互作用和联系是当前研究的热点，其研究价值在于指导情感障碍患者的治疗。当前杏仁核与情感关系的fMRI研究多采用面孔识别等视觉刺激方法，本研究拟以轻音乐和恐怖音乐作为刺激内容，通过声音刺激途径引起脑的正负情感反应，观察杏仁核的激活情况，分析其在情感加工中的作用机制。     

人脑视觉皮质功能磁共振成像研究

目的研究人脑视觉皮质血氧水平依赖（BOLD）的功能磁共振成像。方法18名正常健康志愿者，在光刺激和非刺激的两种对比条件下，采用EP1技术，采集视觉皮质血氧水平依赖（BOLD）图像。t检验分析得出光刺激状态和非刺激状态信号对比的脑功能图像。结果fMRI图像显示光刺激下脑功能活动激活区主要位于双侧视觉皮质区。结论fMRI可用于在活体人脑上研究各功能区活动，光刺激下的fMRI可对人脑视觉皮质进行定位。     

人脑视觉皮层功能磁共振成像原理及临床应用

随着磁共振技术的发展,人们不仅限于对传统解剖形态学定位的认识,而且能借助于磁共振这种无创的检查方法来了解人类神经系统的反应机制,从而在活体上描绘出人类个体所特有的功能区定位,为进一步了解中枢神经系统的作用机制和避免手术对各功能区造成的损伤提供了可资参考的信息。脑的磁共振功能成像(ｆｕｎｃｔｉｏｎａｌｍａｇｎｅｔｉｃｒｅｓｏｎａｎｃｅｉｍａｇｉｎｇ;ｆＭＲＩ)是通过一定的刺激使大脑皮层各功能区在磁共振设备上成像的方法,它结合了功能、影像和解剖三方面的要素,是一种在活体人脑定位各功能区的有效方法。近年来国内…     

视觉皮层对视觉刺激反应的研究———脑功能磁共振成像及磁共振波谱的联合应用

目的对视觉中枢进行BOLD-f MRI及MRS综合应用的研究。方法10例健康受试者,男7例,女3例,年龄26~45岁(平均33岁),常规头颅磁共振检查未发现颅内病变。所有受试者均接受一次f MRI及两次MRS检查。f MRI检查采用组块化设计,活动期通过Goggle系统给予以10Hz闪烁的黑白棋盘格刺激,静息期给予黑屏刺激。f MRI检查结束后,利用MR扫描仪上所带RTIP软件找出兴奋灶的层面,然后在这个层面中进行MRS检查。在第一次MRS检查中,给予黑屏刺激。在第二次MRS检查中给予受试者和f MRI检查中相同的黑白棋盘格刺激。f MRI数据使用SPM99处理,MRS数据使用Functool2处理。结果在f MRI实验中,双侧枕叶有较明显的激活,双侧距状回则更加明显,激活最强点位于右侧距状回。MRS实验中,可发现给予视觉刺激后NAA峰高有一定程度的增高,Cho峰高有一定程度的降低,所以在距状回层面,双侧枕叶发现较明显的NAA/Cho增高区。刺激前后NAA/Cho增加54.28%(2.103±0.014versus3.200±0.061,P0.05,配对t检验)。而且f MRI所得兴奋区与MRS所得NAA/Cho增加区基本吻合。结论视皮层的功能磁共振及磁共振波谱联合研究是可行的,其二者所得结果有一定的相关性和一致性。     

气味的刺激大脑嗅觉功能磁共振成像研究

目的 采用血氧水平依赖功能磁共振成像技术(BOLD-fMRI)研究香臭气味刺激对不同健康志愿者嗅觉功能激活区的分布特点.方法 对22名无嗅觉障碍的健康志愿者,利用愉快的香草醛和非愉快的硫化氢两种气体分别以组块设计进行刺激实验,采用单次激发梯度回波EPI序列扫描,使用MRIcro软件及SPM2软件数据后处理.结果 愉快气...     

正常人视觉刺激下心算任务的功能磁共振成像研究

目的：采用功能磁共振成像（fMRI）技术对正常人视觉刺激下简单心算任务进行研究，探讨不同计算任务类型相关脑功能区的定位及作用机制，进一步理解人脑高级思维模式。资料与方法：对12名右利手志愿者（男6名，女6名）进行简单加法计算、简单减法计算和退位减法计算任务的fMRI研究。应用组块设计模式，采用GE 1.5T磁共振扫描仪，对所有志愿者行T1WI和fMRI。采用AFNI软件进行数据分析和脑功能区定位，同时记录被试的计算正确率和反应时间。结果：12名被试中共获取10人的行为学数据。3种心算任务模式随计算难度的增加，平均反应时间延长，计算正确率下降。男女间比较复杂减法任务计算正确率存在差异，女性低于男性（P<0.05）。3种计算任务存在共同激活脑区，额叶为减法任务主要相关脑区。随任务难度加深，脑总体激活体积增大。结论：fMRI可以简单便捷地定位心算相关脑功能区，心算为多个脑功能区协同工作的复杂过程。     

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。     

功能磁共振成像在视觉系统研究中的应用进展

血氧水平依赖功能磁共振成像(BOLD-fMRI)实现了对人类视觉系统相关脑区的功能定位,在视觉系统的研究中已取得重要成果.本文详细讨论了人类视觉加工的神经过程,即等级加工和平行加工理论.并就fMRI在视觉皮层定位、颜色识别、运动物体视觉感知等方面的应用作一综述.     

功能磁共振成像在人脑数字及汉字认知加工中的初步研究

目的 应用功能磁共振成像(fMRI)对比研究人脑在数字和汉字认知刺激下脑功能活动，探讨其精确脑区定位及其可能机制。方法 母语为汉语的12例右利手健康志愿者(男5例，女7例)进行了数字和汉字的看及默读实验，使用MRI仪以BOLD法采集脑部数据，用SPM99等软件后处理，获得脑功能活动图像。结果 看数字和汉字均能激活双侧纹外视区、枕上回、顶叶及额下回少部分区域；默读数字和汉字额上回及额中回激活较明显：处理汉字比处理数字在额叶激活的面积更大；还发现在汉字的认知加工过程中有豆状核、丘脑及小脑的参与。结论 数字及汉字的认知加工激活脑内不同区域，额叶在汉字的处理过程中起更重要作用。fMRI是研究活体人脑语言功能十分有效的方法。     

Age differences in orbitofrontal activation: an fMRI investigation of delayed match and nonmatch to sample

Several investigations have suggested that the orbitofrontal cortex (OFC) may be particularly vulnerable to the effects of age-related changes. We recently reported behavioral data indicating greater age differences in orbitofrontal tasks when directly compared to tasks tapping dorsolateral prefrontal functions. The present study was designed to investigate the neural underpinnings of age differences in OFC functioning. Event-related functional magnetic resonance imaging (fMRI) was performed during delayed match and nonmatch to sample tasks, previously shown to differentially activate medial and lateral OFC in young adults. Sixteen healthy younger [age = 26.7(5.6)] and 16 healthy older individuals [age = 69.1 + 5.6] with similar levels of education and general cognitive functioning participated in the experiment. Participants chose the stimulus from a pair of stimuli matching a previously viewed target (match to sample) or chose the nontarget item (nonmatch to sample) depending upon a trial-specific instruction word. Consistent with previous studies, SPM99 analyses of the younger age group revealed activation for medial OFC regions during the match task compared to the nonmatch task and lateral OFC activation during the nonmatch task compared to the match task. In contrast, older adults showed prefrontal activation only during the match relative to the nonmatch task and posterior temporal and limbic involvement during the nonmatch relative to the match task. Between-group analyses confirmed within-group results suggesting differential age-related recruitment of prefrontal regions when performing match and nonmatch tasks. Results suggest that OFC recruitment during these cognitive tasks changes with age and should be evaluated within the context of other prefrontal subregions to further define differential age effects on frontal functions.     

Assessment of brain responses to innocuous and noxious electrical forepaw stimulation in mice using BOLD fMRI

Functional magnetic resonance imaging (fMRI) using the blood oxygen level-dependent (BOLD) contrast was used to study sensory processing in the brain of isoflurane-anesthetized mice. The use of a cryogenic surface coil in a small animal 9.4T system provided the sensitivity required for detection and quantitative analysis of hemodynamic changes caused by neural activity in the mouse brain in response to electrical forepaw stimulation at different amplitudes. A gradient echo-echo planar imaging (GE-EPI) sequence was used to acquire five coronal brain slices of 0.5 mm thickness. BOLD signal changes were observed in primary and secondary somatosensory cortices, the thalamus and the insular cortex, important regions involved in sensory and nociceptive processing. Activation was observed consistently bilateral despite unilateral stimulation of the forepaw. The temporal BOLD profile was segregated into two signal components with different temporal characteristics. The maximum BOLD amplitude of both signal components correlated strongly with the stimulation amplitude. Analysis of the dynamic behavior of the somatosensory ‘fast’ BOLD component revealed a decreasing signal decay rate constant k_off with increasing maximum BOLD amplitude (and stimulation amplitude). This study demonstrates the feasibility of a robust BOLD fMRI protocol to study nociceptive processing in isoflurane-anesthetized mice. The reliability of the method allows for detailed analysis of the temporal BOLD profile and for investigation of somatosensory and noxious signal processing in the brain, which is attractive for characterizing genetically engineered mouse models.     

Exposure to appetitive food stimuli markedly activates the human brain

OBJECTIVE: The increased incidence of obesity most likely reflects changes in the environment that had made food more available and palatable. Here we assess the response of the human brain to the presentation of appetitive food stimuli during food presentation using PET and FDG. METHOD: Metabolic changes in response to food presentation were done in 12 healthy normal body weight subjects who were food deprived before the study. RESULTS: Food presentation significantly increased metabolism in the whole brain (24%, P < 0.01) and these changes were largest in superior temporal, anterior insula, and orbitofrontal cortices. The increases in the right orbitofrontal cortex were the ones that correlated significantly with the increases in self-reports of hunger and desire for food. DISCUSSION: The marked increase in brain metabolism by the presentation of food provides evidence of the high sensitivity of the human brain to food stimuli. This high sensitivity coupled with the ubiquitousness of food stimuli in the environment is likely to contribute to the epidemic of obesity. In particular, the activation of the right orbitofrontal cortex, a brain region involved with drive, may underlie the motivation to procure food, which may be subjectively experienced as "desire for food" and "hunger" when exposed to food stimuli.     

正常老化对视皮层静息状态脑活动的影响

目的利用fMRI技术初步探讨年龄对人类视皮层静息状态活动的影响。方法10名健康青年志愿者及10名老年健康志愿者参加实验。任务通过听觉呈现。任务期要求受试者听汉语真词词组并作词语属性判断(具体或抽象)。静息期要求受试者闭眼、静卧,不做任何主动思维活动。利用SPM 2软件进行数据处理,采用反减法获得负激活图。结果两组受试者负激活脑区部位基本一致,主要包括扣带回后部/楔前叶(BA 7),前额叶中内侧(BA 32/10),两侧前额叶背外侧(BA 9),两侧顶下小叶(BA 39/40),两侧枕叶视皮层(BA 18/19),左侧基底节区及两侧岛叶(BA 13)。该负激活脑区模式与Raichle等提出的脑默认活动网络基本一致。进一步组间分析发现,老年人视皮层静息期fMR信号强度明显高于青年人组。结论本研究进一步验证了静息状态人脑默认活动假说,并发现静息状态时老年人视皮层活动比青年人活跃。     

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.     

Activations related to "mirror" and "canonical" neurones in the human brain: an fMRI study

In the macaque monkey ventral premotor cortex (F5), "canonical neurones" are active when the monkey observes an object and when the monkey grasps that object. In the same area, "mirror neurones" fire both when the monkey observes another monkey grasping an object and when the monkey grasps that object. We used event-related fMRI to investigate where in the human brain activation can be found that reflects both canonical and mirror neuronal activity. There was activation in the intraparietal and ventral limbs of the precentral sulcus when subjects observed objects and when they executed movements in response to the objects (canonical neurones). There was activation in the dorsal premotor cortex, the intraparietal cortex, the parietal operculum (SII), and the superior temporal sulcus when subjects observed gestures (mirror neurones). Finally, activations in the ventral premotor cortex and inferior frontal gyrus (area 44) were found when subjects imitated gestures and executed movements in response to objects. We suggest that in the human brain, the ventral limb of the precentral sulcus may form part of the area designated F5 in the macaque monkey. It is possible that area 44 forms an anterior part of F5, though anatomical studies suggest that it may be a transitional area between the premotor and prefrontal cortices.     

Comparison of BOLD fMRI and MEG characteristics to vibrotactile stimulation

The characteristics of blood oxygenation level-dependent (BOLD) fMRI and magnetoencephalographic (MEG) responses to vibrotactile stimuli in humans were studied and compared. The stimuli, presented with interstimulus intervals (ISIs) ranging from 1 to 5 s, yielded highly reproducible MEG responses, with current dipoles in the primary somatosensory (SI) cortex in all subjects. BOLD fMRI responses to similar stimuli showed substantial intrasubject variation in the activation sites around the SI cortex. BOLD responses were detected in all subjects in the secondary somatosensory (SII) cortices as well, with comparable BOLD response amplitudes to those in the SI cortex. Current dipoles, used to model the MEG signals, were stronger at longer ISIs than shorter ISIs. The BOLD response amplitudes did not show a similar dependence on ISI, but the activated brain area was larger when longer ISIs or longer stimuli were applied. Our results support the view that combined use of brain mapping methods provides complementary information and should be considered in functional brain examinations.     

Gastric distention activates satiety circuitry in the human brain

Gastric distention during meal ingestion activates vagal afferents, which send signals from the stomach to the brain and result in the perception of fullness and satiety. Distention is one of the mechanisms that modulates food intake. We measured regional brain activation during dynamic gastric balloon distention in 18 health subjects using functional magnetic resonance imaging and the blood oxygenation level-dependent (BOLD) responses. The BOLD signal was significantly changed by both inflow and outflow changes in the balloon's volume. For lower balloon volumes, water inflow was associated with activation of sensorimotor cortices and right insula. The larger volume condition additionally activated left posterior amygdala, left posterior insula and the left precuneus. The response in the left amygdala and insula was negatively associated with changes in self-reports of fullness and positively with changes in plasma ghrelin concentration, whereas those in the right amygdala and insula were negatively associated with the subject's body mass index. The widespread activation induced by gastric distention corroborates the influence of vagal afferents on cortical and subcortical brain activity. These findings provide evidence that the left amygdala and insula process interoceptive signals of fullness produced by gastric distention involved in the controls of food intake.     

Working memory dysfunction in schizophrenia compared to healthy controls and patients with depression: evidence from event-related fMRI

Studies on working memory (WM) dysfunction in schizophrenia have reported several functionally aberrant brain areas including the lateral prefrontal cortex, superior temporal areas and the striatum. However, less is known about the relationship of WM-dysfunction, cerebral activation, task-accuracy and diagnostic specificity. Using a novel WM-task and event-related functional magnetic resonance imaging (fMRI), we studied healthy control subjects (n=17) and partially remitted, medicated inpatients meeting DSM-IV criteria for schizophrenia (n=19) and major depressive disorder (n=12). Due to the event-related technique, we excluded incorrectly performed trials, thus controlling for accuracy-related activation confounds. Compared with controls, patients with schizophrenia showed less activation in frontoparietal and subcortical regions at high cognitive load levels. Compared with patients with depression, schizophrenic patients showed less prefrontal activation in left inferior frontal cortex and right cerebellum. In patients with schizophrenia, a lack of deactivation of the superior temporal cortex was found compared to both healthy controls and patients with depression. Thus, we could not confirm previous findings of impaired lateral prefrontal activation during WM performance in schizophrenic patients after the exclusion of incorrectly performed or omitted trials in our functional analysis. However, superior temporal cortex dysfunction in patients with schizophrenia may be regarded as schizophrenia-specific finding in terms of psychiatric diagnosis specificity.     

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.