脑科学和脑功能MR成像

目的:在对大脑认知功能进行脑功能成像研究之中,随着磁共振成像技术的发展,人们现在可以对脑的认知功能,如视觉、运动、语言和记忆等功能中枢进行成像.本文首先介绍了脑科学的发展历程,并从脑功能MR成像的方法出发,分析了其成像机理,探讨了用脑功能MR成像为手段对脑科学-认知科学进行的方法研究,最后对脑功能MR成像应用于脑科学的研究作了展望.     

光学相干成像技术对神经及脑的成像

神经与脑的成像作为最具挑战性的课题之一,得到越来越多的关注.对神经与脑部的成像,能够对神经系统及脑部形态、结构以及功能量化,不仅有助于更加深入地了解脑及神经系统.并且可以提高临床诊疗的效率.光学相干成像技术(OCT)是一种新型的成像技术,已被广泛用于生物与医学领域.光学相干成像技术在对神经及脑的成像研究中,最为人们所关注,其该技术的发展也最为迅速.该技术为解决神经及脑的成像问题提供了新的思路和方法,其发展潜力还有待发掘.概述了光学相干成像技术在神经和脑成像领域的最新技术以及成果,讨论了其在神经和脑成像领域的优缺点以及其未来的发展趋势.     

基于静息状态的功能磁共振成像

基于静息状态的功能磁共振成像已经成为当前人脑功能研究的重要手段之一.本文首先介绍了基于静息状态功能磁共振成像人脑功能研究的历史和现状,包括对正常人脑功能的研究和对病理状态下的人脑功能异常研究.然后介绍了基于静息状态功能磁共振成像的两种主要的数据分析方法:功能连接分析和慢波振荡特性分析.     

生物电阻抗脑功能成像研究

在脑科学研究和大脑疾病的临床诊疗过程中，脑功能的连续监测，特别是脑功能的二维图像连续监测，对于人类深入地认识大脑和临床脑疾病患者的及时治疗都是十分重要的。本文主要讨论了脑疾病、脑神经活动ＥＩＴ成像的生物物理基础；脑疾病、脑神经活动的ＥＩＴ成像研究；脑ＥＩＴ成像的测量技术研究；脑ＥＩＴ成像的算法和脑计算模型研究以及目前脑ＥＩＴ成像存在的问题和研究方向。     

新的成像方法为观察大脑提供更好条件

近年来，利用成像技术开展对人类大脑功能的研究受到人们的关注。本文对应用功能性磁共振成像技术（ｆＭＲＩ）、正电子发射断层扫描技术（ＰＥＴ），以及这些技术与脑电图（ＥＥＧ）及脑磁图（ＥＭＧ）联用进行的脑功能成像研究的进展作一综述。并对新的成像方法用于脑功能研究的前景进行了展望     

生物电阻抗脑成像研究

在脑和大脑疾病的临床诊疗过程中，脑功能的连续监测，特别是脑功能的二维图像连续监测，对于人类深入地认识大脑和临床脑疾病患者的及时治疗都是十分重要的。本文主要讨论了脑疾病、脑神经活动ＥＩＴ成像的生理物理基础。脑疾病、脑神经活动的ＥＩＴ成像研究；脑ＥＩＴ成像的测量技术研究；脑ＥＩＴ成像的算法和脑计算模型研究以及目前脑ＥＩＴ成像存在的问题和研究方向。     

脑功能光学成像技术及医学进展

本文较全面论述了目前发展中的脑功能光学成像技术:脑功能的内禀光学成像、神经元活动相关信号方法、光学相干层析成像、无损伤脑功能内禀光学成像等方法的原理、成像特性及相关最新医学研究进展.     

生物电阻抗脑功能成像研究现状

生物电阻抗成像技术在脑功能和脑疾病检测与监护中具有潜在的应用价值,并且具有无创伤、功能性、价格低、操作简便等优点,是目前生物医学工程的研究热点。本文主要介绍了生物电阻抗成像技术在脑功能和脑疾病成像的研究现状,并着重讨论了EIT(electrical impedance tomography,生物电阻抗断层成像)、MIT(magnetic induction tomography,磁感应电阻抗成像)、MREIT(magnetic resonanceelectrical impedance tomography,磁共振电阻抗成像)、MAT-MI(magnetoacoustic tomography with magneticinduction,磁感应磁声成像)技术在成像过程中的区别及今后有待近一步解决的理论与技术难题。     

脑功能成像技术的研究

利用医学成像技术研究人类大脑功能是近年来发展最为迅速的领域之一。本文全面地综述了功能性磁共振成像术（ＦＭＲＩ）、正电子发射断层扫描术（ＰＥＴ）及其与脑电磁检测技术（ＥＥＴ、ＭＥＧ）联合应用，开展的脑功能实时成像的研究进展，同时就新的成像理论及方法进行了论述，并指明脑功能成像技术的研究将为探索人类的认知与思维活动带来新的前景     

用MRI直接检测神经电磁场的研究

随着医学影像学的发展,基于脑内血氧水平变化的功能磁共振成像(fMRI)技术逐渐成为研究人脑功能的最主要的手段之一,但它的时间分辨率低.近年提出的神经电流磁共振成像(nc-MRI)是一种利用磁共振成像(MRI)技术对神经活动产生的电磁场直接成像的新方法.在原理上,nc-MRI是一种无创伤且同时具有高时间和空间分辨率特性的技术.因此,它的出现有可能会极大地推进脑功能的研究.探讨了nc-MRI信号的产生机制,包括神经磁场的理论模型和nc-MRI信号源及nc-MRI信号的模拟计算,其中包括对树突分支磁场的模拟以及nc-MRI的实验研究进展:展望了nc-MRI的未来发展方向.     

Rodent functional and anatomical imaging of pain

Human brain imaging has provided much information about pain processing and pain modulation, but brain imaging in rodents can provide information not attainable in human studies. First, the short lifespan of rats and mice, as well as the ability to have homogenous genetics and environments, allows for longitudinal studies of the effects of chronic pain on the brain. Second, brain imaging in animals allows for the testing of central actions of novel pharmacological and nonpharmacological analgesics before they can be tested in humans. The two most commonly used brain imaging methods in rodents are magnetic resonance imaging (MRI) and positron emission tomography (PET). MRI provides better spatial and temporal resolution than PET, but PET allows for the imaging of neurotransmitters and non-neuronal cells, such as astrocytes, in addition to functional imaging. One problem with rodent brain imaging involves methods for keeping the subject still in the scanner. Both anesthetic agents and restraint techniques have potential confounds. Some PET methods allow for tracer uptake before the animal is anesthetized, but imaging a moving animal also has potential confounds. Despite the challenges associated with the various techniques, the 31 studies using either functional MRI or PET to image pain processing in rodents have yielded surprisingly consistent results, with brain regions commonly activated in human pain imaging studies (somatosensory cortex, cingulate cortex, thalamus) also being activated in the majority of these studies. Pharmacological imaging in rodents shows overlapping activation patterns with pain and opiate analgesics, similar to what is found in humans. Despite the many structural imaging studies in human chronic pain patients, only one study has been performed in rodents, but that study confirmed human findings of decreased cortical thickness associated with chronic pain. Future directions in rodent pain imaging include miniaturized PET for the freely moving animal, as well as new MRI techniques that enable ongoing chronic pain imaging.     

From nociception to pain perception: imaging the spinal and supraspinal pathways

Functional imaging techniques have allowed researchers to look within the brain, and revealed the cortical representation of pain. Initial experiments, performed in the early 1990s, revolutionized pain research, as they demonstrated that pain was not processed in a single cortical area, but in several distributed brain regions. Over the last decade, the roles of these pain centres have been investigated and a clearer picture has emerged of the medial and lateral pain system. In this brief article, we review the imaging literature to date that has allowed these advances to be made, and examine the new frontiers for pain imaging research: imaging the brainstem and other structures involved in the descending control of pain; functional and anatomical connectivity studies of pain processing brain regions; imaging models of neuropathic pain-like states; and going beyond the brain to image spinal function. The ultimate goal of such research is to take these new techniques into the clinic, to investigate and provide new remedies for chronic pain sufferers.     

用于疼痛感知与评估的功能性近红外光谱成像研究进展

疼痛是一种涉及感觉、运动和认知的复杂体验。传统的疼痛评估方法有主观偏倚性较强的特点,但激发了人们对客观疼痛评估成像技术的兴趣。研究表明,在体时大脑痛觉可被定量评估,其中的功能性近红外光谱(fNIRS)技术,因其具有时间分辨率高、成本低、便携等特点,及其可在复杂临床环境中可实时观测疼痛的优势,已被疼痛研究所关注。为了进一步揭示疼痛在临床环境中的潜在皮质作用机制,以构建优化的实验范式设计为基础,综述了与疼痛相关的脑部区域、fNIRS探针定位和数据处理算法的研究进展,特别是现有fNIRS技术在疼痛研究中的主要发现;探讨fNIRS成像与人工智能算法相结合用于疼痛研究和客观评估的相关进展,并对未来发展方向和尚待优化的问题提出建议。     

Pain response measured with arterial spin labeling

The majority of functional MRI studies of pain processing in the brain use the blood oxygenation level‐dependent (BOLD) imaging approach. However, the BOLD signal is complex as it depends on simultaneous changes in blood flow, vascular volume and oxygen metabolism. Arterial spin labeling (ASL) perfusion imaging is another imaging approach in which the magnetically labeled arterial water is used as an endogenous tracer that allows for direct measurement of cerebral blood flow. In this study, we assessed the pain response in the brain using a pulsed‐continuous arterial spin labeling (pCASL) approach and a thermal stimulation paradigm. Using pCASL, response to noxious stimulation was detected in somatosensory cortex, anterior cingulate cortex, anterior insula, hippocampus, amygdala, thalamus and precuneus, consistent with the pain response activation patterns detected using the BOLD imaging approach. We suggest that pCASL is a reliable alternative for functional MRI pain studies in conditions in which blood flow, volume or oxygen extraction are altered or compromised. Copyright © 2013 John Wiley & Sons, Ltd.     

Pain intensity processing within the human brain: a bilateral, distributed mechanism.

Functional imaging studies of human subjects have identified a diverse assortment of brain areas that are engaged in the processing of pain. Although many of these brain areas are highly interconnected and are engaged in multiple processing roles, each area has been typically considered in isolation. Accordingly, little attention has been given to the global functional organization of brain mechanisms mediating pain processing. In the present investigation, we have combined positron emission tomography with psychophysical assessment of graded painful stimuli to better characterize the multiregional organization of supraspinal pain processing mechanisms and to identify a brain mechanism subserving the processing of pain intensity. Multiple regression analysis revealed statistically reliable relationships between perceived pain intensity and activation of a functionally diverse group of brain regions, including those important in sensation, motor control, affect, and attention. Pain intensity-related activation occurred bilaterally in the cerebellum, putamen, thalamus, insula, anterior cingulate cortex, and secondary somatosensory cortex, contralaterally in the primary somatosensory cortex and supplementary motor area, and ipsilaterally in the ventral premotor area. These results confirm the existence of a highly distributed, bilateral supraspinal mechanism engaged in the processing of pain intensity. The conservation of pain intensity information across multiple, functionally distinct brain areas contrasts sharply with traditional views that sensory-discriminative processing of pain is confined within the somatosensory cortex and can account for the preservation of conscious awareness of pain intensity after extensive cerebral cortical lesions.     

Methods on Skull Stripping of MRI Head Scan Images—a Review

The high resolution magnetic resonance (MR) brain images contain some non-brain tissues such as skin, fat, muscle, neck, and eye balls compared to the functional images namely positron emission tomography (PET), single photon emission computed tomography (SPECT), and functional magnetic resonance imaging (fMRI) which usually contain relatively less non-brain tissues. The presence of these non-brain tissues is considered as a major obstacle for automatic brain image segmentation and analysis techniques. Therefore, quantitative morphometric studies of MR brain images often require a preliminary processing to isolate the brain from extra-cranial or non-brain tissues, commonly referred to as skull stripping. This paper describes the available methods on skull stripping and an exploratory review of recent literature on the existing skull stripping methods.     

Changes in the symmetry of rapid movements Effects of velocity and viscosity

Investigations of pain using functional imaging techniques have revealed an extensive central network associated with nociception. This network includes the thalamus, insula, prefrontal cortex and anterior cingulate cortex (ACC) as well as the somatosensory cortices. Positron emission tomography (PET) of regional cerebral blood flow (rCBF) has demonstrated activation of the ACC during cognitively challenging tasks such as the Stroop interference task and divided attention. One interpretation of this research is that ACC is involved in the general features of attention and that it does not play a specific role in pain processing per se. Three-dimensional PET imaging provides a method for assessments of rCBF in a single individual during multiple tasks. In addition, coregistration of PET and magnetic resonance (MR) images allows for better localisation of the PET signals so that differences in cortical activation sites can be more accurately determined. This approach was used to assess rCBF during the experience of pain by subtracting images collected during heat from those during noxious heat stimulation. Two regions of the ACC had elevated rCBF, one in the perigenual region and one in the mid-rostrocaudal region (i.e. midcingulate cortex). During the execution of the Stroop task, the group result showed the midcingulate region overlapping with the site seen during the experience of pain. This group result, however, was not confirmed in the individual subject analysis, which revealed widespread and independent areas of ACC response to pain and Stroop. It is concluded that the ACC contributes to multiple cognitive procedures. It is inadequate to describe the primary contribution of ACC to pain processing as “attention” because it is unlikely that the multiple small and independent activation sites produced by pain and Stroop subserve attentive processing throughout the brain. Received: 22 July 1996 / Accepted: 28 May 1997     

Mapping pain activation and connectivity of the human habenula

The habenula, located in the posterior thalamus, is implicated in a wide array of functions. Animal anatomical studies have indicated that the structure receives inputs from a number of brain regions (e.g., frontal areas, hypothalamic, basal ganglia) and sends efferent connections predominantly to the brain stem (e.g., periaqueductal gray, raphe, interpeduncular nucleus). The role of the habenula in pain and its anatomical connectivity are well-documented in animals but not in humans. In this study, for the first time, we show how high-field magnetic resonance imaging can be used to detect habenula activation to noxious heat. Functional maps revealed significant, localized, and bilateral habenula responses. During pain processing, functional connectivity analysis demonstrated significant functional correlations between the habenula and the periaqueductal gray and putamen. Probabilistic tractography was used to assess connectivity of afferent (e.g., putamen) and efferent (e.g., periaqueductal gray) pathways previously reported in animals. We believe that this study is the first report of habenula activation by experimental pain in humans. Since the habenula connects forebrain structures with brain stem structures, we suggest that the findings have important implications for understanding sensory and emotional processing in the brain during both acute and chronic pain.     

Renewal of the neurophysiology of language: functional neuroimaging

Functional neuroimaging methods have reached maturity. It is now possible to start to build the foundations of a physiology of language. The remarkable number of neuroimaging studies performed so far illustrates the potential of this approach, which complements the classical knowledge accumulated on aphasia. Here we attempt to characterize the impact of the functional neuroimaging revolution on our understanding of language. Although today considered as neuroimaging techniques, we refer less to electroencephalography and magnetoencephalography studies than to positron emission tomography and functional magnetic resonance imaging studies, which deal more directly with the question of localization and functional neuroanatomy. This review is structured in three parts. 1) Because of their rapid evolution, we address technical and methodological issues to provide an overview of current procedures and sketch out future perspectives. 2) We review a set of significant results acquired in normal adults (the core of functional imaging studies) to provide an overview of language mechanisms in the "standard" brain. Single-word processing is considered in relation to input modalities (visual and auditory input), output modalities (speech and written output), and the involvement of "central" semantic processes before sentence processing and nonstandard language (illiteracy, multilingualism, and sensory deficits) are addressed. 3) We address the influence of plasticity on physiological functions in relation to its main contexts of appearance, i.e., development and brain lesions, to show how functional imaging can allow fine-grained approaches to adaptation, the fundamental property of the brain. In closing, we consider future developments for language research using functional imaging.     

Clinical neurophysiology of aging brain: from normal aging to neurodegeneration

Physiological brain aging is characterized by a loss of synaptic contacts and neuronal apoptosis that provokes age-dependant decline of sensory processing, motor performance, and cognitive function. Neural redundancy and plastic remodelling of brain networking, also secondary to mental and physical training, promotes maintenance of brain activity in healthy elderly for everyday life and fully productive affective and intellectual capabilities. However, age is the main risk factor for neurodegenerative disorders such as Alzheimer's disease (AD) that impact on cognition. Oscillatory electromagnetic brain activity is a hallmark of neuronal network function in various brain regions. Modern neurophysiological techniques including electroencephalography (EEG), event-related potential (ERP), magnetoencephalography (MEG), and transcranial magnetic stimulation (TMS) can accurately index normal and abnormal brain aging to facilitate non-invasive analysis of cortico–cortical connectivity and neuronal synchronization of firing and coherence of rhythmic oscillations at various frequencies. The present review provides a perspective of these issues by assaying different neurophysiological methods and integrating the results with functional brain imaging findings. It is concluded that discrimination between physiological and pathological brain aging clearly emerges at the group level, with applications at the individual level also suggested. Integrated approaches utilizing neurophysiological techniques together with biological markers and structural and functional imaging are promising for large-scale, low-cost and non-invasive evaluation of at-risk populations. Practical implications of the methods are emphasized.