Event-related single-shot volumetric functional magnetic resonance inverse imaging of visual processing

Developments in multi-channel radio-frequency (RF) coil array technology have enabled functional magnetic resonance imaging (fMRI) with higher degrees of spatial and temporal resolution. While modest improvement in temporal acceleration has been achieved by increasing the number of RF coils, the maximum attainable acceleration in parallel MRI acquisition is intrinsically limited only by the amount of independent spatial information in the combined array channels. Since the geometric configuration of a large-n MRI head coil array is similar to that used in EEG electrode or MEG SQUID sensor arrays, the source localization algorithms used in MEG or EEG source imaging can be extended to also process MRI coil array data, resulting in greatly improved temporal resolution by minimizing k-space traversal during signal acquisition. Using a novel approach, we acquire multi-channel MRI head coil array data and then apply inverse reconstruction methods to obtain volumetric fMRI estimates of blood oxygenation level dependent (BOLD) contrast at unprecedented whole-brain acquisition rates of 100 ms. We call this combination of techniques magnetic resonance Inverse Imaging (InI), a method that provides estimates of dynamic spatially-resolved signal change that can be used to construct statistical maps of task-related brain activity. We demonstrate the sensitivity and inter-subject reliability of volumetric InI using an event-related design to probe the hemodynamic signal modulations in primary visual cortex. Robust results from both single subject and group analyses demonstrate the sensitivity and feasibility of using volumetric InI in high temporal resolution investigations of human brain function.     

听觉脑功能磁共振成像

听觉脑功能磁共振成像是磁共振功能成像(functionalmagneticresonanceimaging,fMRI)的一种,fMRI是一种安全的影像学检查手段,在完全无创的条件下对人脑进行功能分析,一次成像可同时获得解剖与功能影像,而且对人体无辐射损伤。尽管fMRI技术和方法还在不断发展和完善,但其可靠性和实用性是不容置疑的。它对听觉障碍患者的术前诊断、手术计划的制定、术后患者康复程度的评估,将会发挥越来越重要的作用。     

Information processing in magnetic resonance imaging

Techniques of image processing have been developed for the extraction of information from magnetic resonance images. The response of nuclei to a sequence of magnetic stimulations has been modeled and used to predict the effects of changing magnetic resonance parameters on signal intensity. This allows the calculation of new images from a small set of acquired data without additional acquisition. These images can be used to predict the results of new imaging techniques before actual implementation and to simulate the effects of parameter variations which are unfeasible or impractical, such as variable field strength. New forms of representation, for example, a tissue type map in which each homogeneous tissue category has been identified and labeled, can be used for more direct interpretation.     

Informing brain connectivity with optogenetic functional magnetic resonance imaging

Optogenetic functional magnetic resonance imaging (ofMRI) is a novel approach that combines optogenetic control of neural circuits with high-field functional MRI. Optogenetics is a neuro-modulation technology in which light-activated trans-membrane conductance regulators are introduced into specifically targeted cell types to allow temporally precise, millisecond-scale activity modulation in vivo. By combining optogenetic control with fMRI readout, neural activity arising from specific circuit elements defined by genetic identity, cell body location, and axonal projection targets can be monitored in vivo across the whole brain. These unique features of ofMRI open new vistas for in vivo characterization of the dense plexus of neural connections according to their type and functionality.     

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。     

Item analysis in functional magnetic resonance imaging

Behavioral and neuroimaging studies of cognition frequently test hypotheses regarding mental processing of different stimulus categories (e.g. verbs, faces, animals, scenes, etc.). The conclusions of such studies hinge upon the generalizability of their findings from the specific stimuli used in the experiment to the category as a whole. This type of generalizability is explicitly tested in behavioral studies, using "item analysis". However, generalizability to stimulus categories has up until now been assumed in neuroimaging studies, without employing item analysis for statistical validation. Here we apply item analysis to a functional magnetic resonance imaging study of nouns and verbs, demonstrating its theoretical importance and feasibility. In the subject-wise analysis, a left prefrontal and a left posterior-temporal region of interest showed putative grammatical class effects. An item-wise analysis revealed, however, that only the left posterior-temporal effect was generalizable to the stimulus categories of nouns and verbs. Taken together, the findings of the subject- and item-wise analyses suggest that grammatical-class effects in the left prefrontal cortex depend on the particular word stimuli used, rather than reflecting categorical differences between nouns and verbs. This empirical example illustrates that item analysis not only is sufficiently powered to detect task relevant changes in BOLD signal but also can make theoretically important distinctions between findings that generalize to the item populations, and those that do not.     

功能磁共振在神经外科中的应用

功能磁共振(fMRI)是一种被广泛接受的成像手段,近年来已用于多种临床实践中,特别是在指导神经外科手术方面有了很大的进展.本文就fMRI基本原理和技术及其在有效性评估、指导神经外科手术和术后患者随访方面的作用予以综述.     

胎盘功能磁共振成像研究进展

胎盘是维持胎儿在子宫内发育的重要器官。MRI越来越多地用于胎儿及胎盘的解剖成像。随着影像技术的发展,功能MRI广泛应用于科研及临床,亦是评估胎盘功能重要的工具。本文对胎盘功能MRI的主要研究进展进行综述。     

Lateralisation of nociceptive processing in the human brain: a functional magnetic resonance imaging study

Nociceptive processing within the human brain takes place within two distinct and parallel systems: the lateral and medial pain systems. Current knowledge indicates that the lateral system is involved in processing the sensory-discriminative aspects of pain, and that the medial system is involved in processing the affective-motivational aspects of pain. Hemispheric differences in brain activation (lateralisation) during nociceptive processing were studied to further clarify the division of function between the lateral and medial pain systems. Hemispheric lateralisation was studied by applying painful CO(2) laser stimuli of 3-s duration sequentially to the left and right medial lower calves of five normal right-handed human subjects. The resultant brain activity was measured using 3-T functional magnetic resonance imaging, by determining significant changes in blood oxygen level dependent (BOLD) signal and applying a general linear modelling approach. Volumes of interest were defined for the primary and secondary somatosensory cortices (SI and SII), the insular cortex, and the thalamus, on individual subjects' high-resolution structural scans. Hemispheric lateralisation was quantified by comparing the level of activation between brain hemispheres within each volume of interest. In SII, no significant hemispheric difference in activation was detected. In the insula, activation was significantly greater in the left hemisphere than the right. In both SI and the thalamus, activation in response to painful stimulation was significantly greater in the hemisphere contralateral to the stimulus, which is consistent with these areas being involved in processing the sensory-discriminative aspects of pain.     

亚急性脑卒中患者静息态功能磁共振成像

目的 探讨应用静息态功能磁共振成像(rs-fMRI)对缺血性脑卒中患者病灶区进行检测的可行性。方法 收集14例亚急性缺血性脑卒中患者,分析其rs-fMRI数据,包括病灶区和正常对照区平均信号的低频振幅、两区域间相位延迟前后的功能连接和相位延迟3项主要指标。结果 ①低频振幅分析:4例患者病灶区低频振幅增强,10例病灶区低频振幅减弱;14例患者病灶区和正常对照区低频振幅的差异无统计学意义(t=-1.6290,P=0.1273)。②功能连接分析:42.86%(6/14)的患者病灶区与正常区的功能信号存在相位差异。③相位延迟分析:对于正常区,6例患者与全脑信号无相位差异,4例相位超前,4例相位落后;对于病灶区,8例相位超前,6例相位落后。14例患者两侧区域相对全脑的时间延迟值差异无统计学意义(t=0.6288,P=0.5404)。结论 缺血性脑卒中会引起rs-fMRI相关特异性指标的改变,但各指标个体差异明显,一致性不高。     

Evidence for premotor cortex activity during dynamic visuospatial imagery from single-trial functional magnetic resonance imaging and event-related slow cortical potentials

A strong correspondence has been repeatedly observed between actually performed and mentally imagined object rotation. This suggests an overlap in the brain regions involved in these processes. Functional neuroimaging studies have consistently revealed parietal and occipital cortex activity during dynamic visuospatial imagery. However, results concerning the involvement of higher-order cortical motor areas have been less consistent. We investigated if and when premotor structures are active during processing of a three-dimensional cube comparison task that requires dynamic visuospatial imagery. In order to achieve a good temporal and spatial resolution, single-trial functional magnetic resonance imaging (fMRI) and scalp-recorded event-related slow cortical potentials (SCPs) were recorded from the same subjects in two separate measurement sessions. In order to reduce inter-subject variability in brain activity due to individual differences, only male subjects (n = 13) with high task-specific ability were investigated. Functional MRI revealed consistent bilateral activity in the occipital (Brodmann area BA18/19) and parietal cortex (BA7), in lateral and medial premotor areas (BA6), the dorsolateral prefrontal cortex (BA9), and the anterior insular cortex. The time-course of SCPs indicated that task-related activity in these areas commenced approximately 550-650 ms after stimulus presentation and persisted until task completion. These results provide strong and consistent evidence that the human premotor cortex is involved in dynamic visuospatial imagery.     

偏头痛的功能MRI研究进展

偏头痛是一种以疼痛反复发作为特点的慢性功能障碍性疾病。近年来学者应用功能MRI技术对偏头痛进行了大量研究,作者拟从偏头痛的疾病机制、静息态脑功能网络异常和中医针刺干预等三个方面对偏头痛的功能MRI研究进展进行综述。     

功能磁共振成像在语言障碍研究中的应用

功能磁共振成像被广泛的应用于神经语言学的研究中。本文主要介绍功能磁共振成像在语言障碍研究中取得的进展,同时阐述该技术面临的挑战,探讨了其发展前景。     

功能磁共振成像临床应用及进展

近几十年来,多种模态的功能磁共振技术飞速发展,为临床医学的发展产生了重要影响,也为精神影像学的发展提供了重要手段,极大的深化了人类对神经系统疾病和疾病的认知.本文就功能磁共振的成像及图像后处理技术,及其在反映疾病亚临床阶段的功能改变、实时活体的个体化脑功能定位、探索中枢神经系统药物机制等方面的临床应用和进展进行了述评,同时阐明其技术缺陷及未来发展方向.     

疼痛的脑功能MRI研究进展

功能MRI(f MRI)是一种无创性的功能成像技术,近年来被广泛应用于疼痛方面的研究,使得人们对疼痛的生理有了进一步的认识。作者通过对不同类型疼痛的分析,从痛觉中枢的定位、临床疼痛的f MRI研究及疼痛治疗等方面综述了近年关于疼痛的脑f MRI研究进展。     

Brain processing of visual sexual stimuli in healthy men: a functional magnetic resonance imaging study

The brain plays a central role in sexual motivation. To identify cerebral areas whose activation was correlated with sexual desire, eight healthy male volunteers were studied with functional magnetic resonance imaging (fMRI). Visual stimuli were sexually stimulating photographs (S condition) and emotionally neutral photographs (N condition). Subjective responses pertaining to sexual desire were recorded after each condition. To image the entire brain, separate runs focused on the upper and the lower parts of the brain. Statistical Parametric Mapping was used for data analysis. Subjective ratings confirmed that sexual pictures effectively induced sexual arousal. In the S condition compared to the N condition, a group analysis conducted on the upper part of the brain demonstrated an increased signal in the parietal lobes (superior parietal lobules, left intraparietal sulcus, left inferior parietal lobule, and right postcentral gyrus), the right parietooccipital sulcus, the left superior occipital gyrus, and the precentral gyri. In addition, a decreased signal was recorded in the right posterior cingulate gyrus and the left precuneus. In individual analyses conducted on the lower part of the brain, an increased signal was found in the right and/or left middle occipital gyrus in seven subjects, and in the right and/or left fusiform gyrus in six subjects. In conclusion, fMRI allows to identify brain responses to visual sexual stimuli. Among activated regions in the S condition, parietal areas are known to be involved in attentional processes directed toward motivationally relevant stimuli, while frontal premotor areas have been implicated in motor preparation and motor imagery. Further work is needed to identify those specific features of the neural responses that distinguish sexual desire from other emotional and motivational states.     

Functional imaging of visuospatial processing in Alzheimer's disease

Alzheimer's disease (AD) is known to cause a variety of disturbances of higher visual functions that are closely related to the neuropathological changes. Visual association areas are more affected than primary visual cortex. Additionally, there is evidence from neuropsychological and imaging studies during rest or passive visual stimulation that the occipitotemporal pathway is less affected than the parietal pathway. Our goal was to investigate functional activation patterns during active visuospatial processing in AD patients and the impact of local cerebral atrophy on the strength of functional activation. Fourteen AD patients and fourteen age-matched controls were measured with functional magnetic resonance imaging (fMRI) while they performed an angle discrimination task. Both groups revealed overlapping networks engaged in angle discrimination including the superior parietal lobule (SPL), frontal and occipitotemporal (OTC) cortical regions, primary visual cortex, basal ganglia, and thalamus. The most pronounced differences between the two groups were found in the SPL (more activity in controls) and OTC (more activity in patients). The differences in functional activation between the AD patients and controls were partly explained by the differences in individual SPL atrophy. These results indicate that parietal dysfunction in mild to moderate AD is compensated by recruitment of the ventral visual pathway. We furthermore suggest that local cerebral atrophy should be considered as a covariate in functional imaging studies of neurodegenerative disorders.     

肾纤维化功能性MRI的研究进展

肾纤维化可导致肾功能衰竭,是终末期慢性肾病常见的结局,也是肾移植失败的最常见原因。因此,肾纤维化的程度与患者预后密切相关。临床上检测肾纤维化造成肾功能不全的方法有很多,但是目前缺乏一种活体无创性动态监测肾纤维化的可靠手段。f MRI在检测肾功能、评估肾纤维化程度方面近来越来越受到重视。作者回顾和分析了过去几年肾脏的几种f MRI在肾纤维化这一领域的发展。     

胰腺癌磁共振功能成像的最新进展

胰腺癌发病隐匿,进展迅速,死亡率高,预后差。手术虽是主要治疗手段,但术后5年生存率小于5％l^[1]。另外,近85％的患者都是在晚期才得到诊断,丧失了手术机会,而传统的放化疗手段也不能明显改善患者的预后,且疗效不确切。副作用多121。由于极高的软组织对比度、多参数成像及无放射性,MR对于胰腺癌的筛查、诊断、分期及疗效评价起着不可或缺的作用。近年来,随着3．0TMR在临床上的应用推广,其对胰腺癌形态学的评价效果不仅可以与64排CT相媲美,另外在小胰腺癌的筛查诊断和转移灶的发现上甚至要优于64排CT^[1]”,而且MR功能成像可以评价CT所不能提供的肿瘤细胞恶性生物学特征及其微环境的生物信息,为进一步研究胰腺癌的诊断及其疗效评价提供了有效的成像方法,从而有助于提高胰腺癌患者的治疗效果和生存率。肿瘤的MR功能成像通常包括弥散加权成像（Diffusion weighted imaging,DWI）、灌注加权成像（Perfusion weighted imaging,PWI）和磁共振波谱分析（Magnetic resonance spectroscopy,MRS）。DWI是基于水分子布朗运动的不同对组织病理特征进行评价,主要通过显示肿瘤细胞密集程度及间质内纤维含量所导致的水分子受限程度来反映肿瘤组织的病理生物活性状态：PWI是一种无创性研究肿瘤组织的微血管分布及血流灌注情况的一类MR检查技术,反映肿瘤细胞微环境血液动力学方面的信息;MRS是一种无创性研究活体器官组织代谢、生化变化及化合物定量分析的方法,主要反映肿瘤组织内癌细胞及其赖以生存的周围微环境所发生的生物代谢变化。本文就近年来MRDWI、PWI及。^1H-MRS在胰腺癌中的应用作一综述。     

慢性疼痛的功能MRI研究进展

慢性疼痛是一种关乎人体生理和心理的疾病,近年来学者应用功能MRI技术(functional magnetic resonance imaging,fMRI)对慢性疼痛进行了大量研究,作者从慢性疼痛的特点、静息态fMRI对慢性疼痛的研究方法、实验和分析等方面对慢性疼痛的静息态fMRI研究进展进行综述。