基于功能性近红外光谱技术的儿童与成人视皮层区功能活动研究

目的　应用功能性近红外光谱技术（fNIRS）探讨儿童与成人视皮层区功能活动的变化。方法　本研究共纳入了46位健康志愿者。将志愿者分为两组,其中儿童组28人,年龄为（9±3）岁;成人组18人,年龄为（23±4）岁。fNIRS设备采用日立ETG-4000近红外脑功能成像仪,通过端口将fNIRS设备与呈现视觉任务的控制电脑进行连接并保证在受试者接受视觉刺激时fNIRS可以同步地检测到视皮层血红蛋白含量的实时变化。视觉刺激任务为黑白棋盘格翻转刺激。将氧合血红蛋白的数据通过Matlab软件分析得出β值,每个通道均包括基线期β值和刺激期β值,利用SPSS 21.0分析软件分别对儿童组以及成人组内受试者单通道的基线期与刺激期β值进行配对样本t检验。Δβ=β值_刺激期-β值_基线期。结果　除了儿童组中的通道12外,01至11通道两组受试者刺激期β值均显著高于基线期,差异均有统计学意义（均为P<0.05）,儿童组受试者与视觉刺激同步的双侧初级视皮层的Δβ值均显著高于成人组（均为P<0.05）;儿童组受试者与视觉刺激同步的双侧次级视皮层的Δβ值也均显著高于成人组（均为P<0.05）。结论　在同样的视觉刺激下,儿童的视皮层功能活动反应程度要明显高于成人。     

视觉皮层功能检测中旋转光栅作为刺激方式的临床研究

目的:观察旋转光栅刺激下皮层功能核磁共振的成像情况,探讨视皮层功能测定中有效便捷的视觉刺激方式。方法:以旋转光栅作为视觉刺激,采用组块设计方式,以1.5T磁共振成像系统采集17例视力正常者和9例弱视患者的视皮层BOLD-fMRI数据。观察分析不同任务/控制状态下对应皮层的成像部位。结果:旋转光栅含有多种视觉刺激成分,所有受检者均获得了与相应视觉刺激对应的视觉皮层反应脑图,且各组反应趋势基本一致。结论:旋转光栅是视皮层功能测定中良好便捷的视觉刺激方式。     

屈光不正性弱视皮层功能损伤的磁共振成像研究

目的 研究屈光不正性弱视患者皮层功能损伤情况.方法 分别利用组块任务模式及事件相关任务模式,对屈光不正性弱视组及正常对照组在不同颜色棋盘格刺激下的脑皮层活动进行了BOLD-fMRI研究.结果 组块任务模式的棋盘格刺激主要激活视觉皮层区;事件相关任务模式的棋盘格刺激还可激活额叶、扣带回、海马旁回、中央前回、颞叶等与视觉注意和视觉意识有关的脑功能区,弱视组与对照组在视皮层及这些视觉注意及意识调控区的激活强度存在显著差异;屈光不正性弱视患者对不同颜色的敏感性减弱,但程度不同.结论 屈光不正性弱视患者视觉皮层及视觉注意和意识调控区的激活减弱可能与这些区域神经细胞的同步放电活动减弱有关.     

视觉正常人简单图形视觉刺激的视皮层功能定位及定量研究

目的 利用功能磁共振成像的方法定位、定量研究视觉正常人简单图形视觉刺激时的视皮层反应模式,为视皮层假体的刺激位置和强度提供参考.方法 对3名视觉正常成年志愿者进行圆环形棋盘格视觉任务的功能磁共振成像实验,同一任务对每位志愿者重复3次,以SPM2脑功能专业分析软件包作后期处理,显示视皮层反应模式.结果 3名受试者均较好完成视觉任务,平均体素反应总数为5217.3±1110.6.反应最强点坐标 x值为(-4.3±8.7)mm,y值为(-83.3±3.7)mm,z值为(-4.0±4.7)mm.平均最大反应强度为15.99±1.58,最大反应脑区为双侧的Brodmann 18区即初级视皮层V2区.解剖上的舌回附近.结论 利用功能磁共振成像的方法可以定位、定量的研究视皮层反应模式,这些反应模式信息可以为视皮层假体的刺激位置、强度等参数提供参考.     

磁共振成像在眼科常见疾病患者脑功能与结构研究中的应用

磁共振成像已被广泛应用于神经科学,可用来评估健康和疾病时个体脑的功能和结构改变.许多眼病患者常伴有视力下降和视野缺损的表现,当视觉信号出现异常后,其视觉通路和视皮层的功能和结构也会随之发生异常变化.本文对磁共振成像在眼科常见疾病患者脑功能与结构研究中的应用做一综述.     

基于功能性近红外光谱技术的屈光不正性弱视患儿视皮层功能研究

目的　应用功能性近红外光谱技术（fNIRS）比较屈光不正性弱视患儿与正常儿童视皮层血红蛋白含量的差异,探讨屈光不正性弱视患儿视皮层功能是否存在异常。方法　选取在山东中医药大学附属眼科医院2019年至2020年就诊的19例（38眼）临床确诊为双眼屈光不正性弱视的患儿作为弱视组,年龄为6～12周岁;另选19例（38眼）年龄相似视力正常的健康儿童作为正常组。在给予最佳矫正视力的情况下,对受试者进行单眼棋盘格翻转刺激的fNIRS检测。采用上海心果光电科技有限公司针对 Polhemus 公司的三维定位仪研发的可视化头部三维定位信息实时记录系统（VPen 1.0）对受试者各通道测量点位置进行定位记录,依据3D定位仪的解剖标记和重叠比例可得第11、12、15、16、17、20、21号通道为fNIRS感兴趣区域通道。将单眼注视黑白棋盘格翻转刺激时段作为刺激期,将此时段fNIRS感兴趣区域通道的β均值用于表示双侧视皮层血红蛋白的含量变化。记录两组受试者年龄、性别、最佳矫正视力、血红蛋白β均值等指标,采用SPSS 23.0软件对所得数据进行统计学分析。结果　弱视组患儿与正常组儿童最佳矫正视力（logMAR）分别为0.20±0.14和-0.02±0.04,两组间差异有统计学意义（t=-8.990,P<0.001）。弱视组患儿氧合血红蛋白β均值低于正常组,差异有统计学意义（P<0.05）;脱氧血红蛋白β均值高于正常组,但差异无统计学意义（P>0.05）。弱视组患儿受试眼同侧视皮层氧合血红蛋白β均值较正常组儿童受试眼同侧视皮层、对侧视皮层β均值均显著减小,差异均有统计学意义（P=0.009、0.003）;弱视组患儿受试眼对侧视皮层氧合血红蛋白β均值较正常组儿童受试眼同侧视皮层、对侧视皮层亦均显著减小,差异均有统计学意义（P=0.016、0.005）。弱视组患儿的最佳矫正视力与其视皮层氧合血红蛋白含量的相关系数r=-0.039（P=0.815）,二者无线性相关关系。结论　fNIRS可以作为测量弱视患者初级视皮层血红蛋白含量的新方法,屈光不正性弱视患儿视皮层存在功能异常。     

视觉信息加工的神经机制

外界信息的80%是经视觉系统传人大脑,视觉系统与脑的许多高级功能密切相关,对视觉信息加工机制的研究成为神经科学、认知科学的热门课题.随着脑科学的发展,视觉信息加工机制的研究进入一个崭新阶段.就视觉通道、等级加工、功能特异化、选择性注意、视皮层细胞的同步振荡等进行综述.     

病理性近视患者空间频率相关的大脑视皮层功能活动变化

目的 应用功能性近红外光谱成像技术(fNIRS)研究不同级别病理性近视(PM)患者在高、低两种空间频率棋盘格视觉刺激任务下的大脑视皮层活动.方法 受试者分为3组:PM-A组(PM患者中合并2级、3级近视性黄斑病变)17眼、PM-B组(PM患者中合并4级近视性黄斑病变)11眼及正常对照组(NC组)16眼.受试者于安静、昏...     

弱视与视觉系统可塑性

弱视是一种发育性眼科疾病,其发病与视觉系统发育关键期内的异常视觉经验密切相关。传统的弱视治疗方法对已超过视觉发育关键期的大龄儿童和成年弱视患者几乎没有效果。知觉学习指经过感知觉训练引起的知觉任务成绩的特异性提高,其生理学基础是神经系统的可塑性。近年来的研究表明,视知觉学习可以显著提高正常人以及诸多高等动物的视知觉功能,并且可以显著改善弱视等视觉系统功能受损患者的视觉功能。动物电生理学研究表明视知觉学习导致了视皮层内神经元调谐特性的改善。这些研究提示我们,即使超过了视觉系统发育的关键期,视觉神经系统仍然存在一定的可塑性。     

功能性磁共振成像在视觉科学研究中的应用进展

磁共振成像是目前较为普及的影像学检查手段之一,传统的磁共振成像及增强成像在眼科临床诊疗中已得到广泛应用.功能性磁共振成像技术包括血氧水平依赖的功能磁共振成像、磁共振波谱成像和弥散张量成像在内,在视觉皮层定位、视神经炎、弱视、青光眼、眼眶肿瘤以及视觉中枢白质纤维重建研究中显示了独特的价值.本文就功能性磁共振成像技术在上述方面的研究进展作一综述.     

斜视患者脑功能与结构异常的研究进展

斜视是一种常见的眼球运动障碍,表现为眼位偏斜,常伴双眼视觉功能受损。正常眼位有赖于参与视觉系统和眼球运动系统的各脑区的正常功能和它们之间的协调配合,其中任一层次的受损都可能引起斜视。早期神经电生理和免疫自显影技术应用于动物实验,发现初级视觉皮层功能损伤,包括双眼视神经元减少、眼优势柱代谢改变。近年来,功能磁共振的发展促进了对人脑皮层功能变化的认识。研究发现斜视患者不仅存在与眼球运动及双眼视觉功能障碍相关的脑皮层及皮层间联系的损伤,还存在与代偿相关的可塑性改变。而基于体素的形态计量学和弥散张量成像技术的应用为斜视患者大脑异常提供了解剖学依据。本文从脑功能与结构异常角度对近几年有关斜视神经机制的研究进展进行综述,以期为进一步研究提供参考。     

A self-supervised deep neural network for image completion resembles early visual cortex fMRI activity patterns for occluded scenes

The promise of artificial intelligence in understanding biological vision relies on the comparison of computational models with brain data with the goal of capturing functional principles of visual information processing. Convolutional neural networks (CNN) have successfully matched the transformations in hierarchical processing occurring along the brain''s feedforward visual pathway, extending into ventral temporal cortex. However, we are still to learn if CNNs can successfully describe feedback processes in early visual cortex. Here, we investigated similarities between human early visual cortex and a CNN with encoder/decoder architecture, trained with self-supervised learning to fill occlusions and reconstruct an unseen image. Using representational similarity analysis (RSA), we compared 3T functional magnetic resonance imaging (fMRI) data from a nonstimulated patch of early visual cortex in human participants viewing partially occluded images, with the different CNN layer activations from the same images. Results show that our self-supervised image-completion network outperforms a classical object-recognition supervised network (VGG16) in terms of similarity to fMRI data. This work provides additional evidence that optimal models of the visual system might come from less feedforward architectures trained with less supervision. We also find that CNN decoder pathway activations are more similar to brain processing compared to encoder activations, suggesting an integration of mid- and low/middle-level features in early visual cortex. Challenging an artificial intelligence model to learn natural image representations via self-supervised learning and comparing them with brain data can help us to constrain our understanding of information processing, such as neuronal predictive coding.     

视感知觉训练对间歇性外斜视患者术后双眼视觉重建的研究进展

间歇性外斜视(IXT)是一种发病率高、斜视角度多变、双眼视觉功能不同程度受损的眼科常见疾病。双眼视觉功能缺损与视觉皮层的改变有关,IXT涉及包括双眼融合相关皮质区域在内的多个脑区的功能改变,部分IXT患者在矫正眼位后,大脑皮层的异常改变依然存在,双眼视觉的恢复仍然困难。针对这些问题,视感知觉训练逐渐应用到IXT患者术后双眼视觉功能的重建中,视感知觉训练从大脑层面修复视觉皮质,通过不断刺激视觉中枢,提高大脑视皮层处理信息的能力,进而修复视觉中枢功能,使患者获得良好的双眼视觉功能,稳定眼位,减少复发。本文就IXT患者双眼视觉损伤机制以及视感知觉训练在IXT治疗中的作用做一综述。希冀为视感知觉训练重建IXT患者术后双眼视觉功能、降低复发率提供更多证据。     

Contralateral monocular dominance in anterior visual cortex confirmed by functional magnetic resonance imaging

PURPOSE: Although it is known that the damage to anterior striate cortex results in temporal peripheral visual field loss of the contralateral eye in patients with cerebral visual disturbance, the monocularity of anterior striate cortex has not been demonstrated in normal living humans. The aim of this study was to investigate whether this could be shown noninvasively using functional magnetic resonance imaging of the human visual cortex. METHODS: Eleven normal volunteers were studied with functional magnetic resonance imaging during alternating monocular visual stimulation using a 1.5 Tesla scanner. The data were motion corrected and spatially normalized to the standard brain. The monocular activation of the visual cortex was compared with the activation by the other eye. RESULTS: In the individual data analysis, contralateral eye dominance was always observed in the anterior striate cortex. In the group analysis from 11 subjects, the area with contralateral eye dominance was found in the most anterior part of primary visual cortex where the calcarine fissure merged with the parieto-occipital sulcus. CONCLUSIONS: This study shows that the contralateral eye dominance of anterior striate cortex can be detected noninvasively with functional magnetic resonance imaging during monocular visual stimulation. The finding confirms that the anterior striate cortex, where the monocular temporal crescent is represented, is primarily monocular, but the fact that greatest density of retinal ganglion cells and photoreceptors is in the nasal hemiretina must also be taken into account when interpreting these results.     

Effects of check size on visual cortex activation studied by functional magnetic resonance imaging

We studied functional magnetic resonance imaging (fMRI) of visual cortex during checkerboard visual stimulation with three standard check sizes to examine whether activation in the visual cortex varied among these sizes. We acquired fMRI at 1.5 T in 8 normal subjects, each receiving the best refractive correction. Each subject underwent an experiment consisting of four conditions: black and white checkerboards with three check sizes (0.25-, 0.5-, and 1.0-degree) flickering at 8 Hz, and a black screen. SPM96 was used for a group data analysis with a random effects model after each of the subject's data was motion-corrected and spatially normalized to a standard brain. The activation in the visual cortex showed the greatest signal changes with the 0.5-degree check among the three check sizes. When standard check sizes are used to stimulate visual cortex in fMRI experiments, our results suggest that 0.5-degree checks flickering at 8 Hz produce the most vigorous activation in visual cortex.     

Magnetostimulation of vision: direct noninvasive stimulation of the retina and the visual brain

The history of magnetophosphenes and their closely related predecessor, electrophosphenes, is described from the mid-18th century to the present time. The current era of magnetic stimulation started in 1985 with the development of a practical capacitor-discharge electromagnetic stimulator by Barker and his colleagues at the University of Sheffield, and their application of it to the brain with Merton and Morton at the National Hospital, London. The safety of magnetostimulation of the brain is discussed as well as the advantages of magnetostimulation over electrostimulation. Principles of magnetostimulation of nerves and magnetic measurement are considered. Effects on motor and sensory systems of the brain are described including magnetic perceptual suppression in the visual cortex and other pioneering work of Amassian, Cracco and Maccabee at SUNY Health, Brooklyn. Magnetophosphenes from retinal and cortical magnetostimulation are distinguished. Now that visual cortical stimulation is possible with the strong magnetic pulses generated by capacitor-discharge instruments, the functional viability of the visual cortex may be tested directly and noninvasively.     

Imaging retinotopic maps in the human brain

A quarter-century ago visual neuroscientists had little information about the number and organization of retinotopic maps in human visual cortex. The advent of functional magnetic resonance imaging (MRI), a non-invasive, spatially-resolved technique for measuring brain activity, provided a wealth of data about human retinotopic maps. Just as there are differences amongst non-human primate maps, the human maps have their own unique properties. Many human maps can be measured reliably in individual subjects during experimental sessions lasting less than an hour. The efficiency of the measurements and the relatively large amplitude of functional MRI signals in visual cortex make it possible to develop quantitative models of functional responses within specific maps in individual subjects. During this last quarter-century, there has also been significant progress in measuring properties of the human brain at a range of length and time scales, including white matter pathways, macroscopic properties of gray and white matter, and cellular and molecular tissue properties. We hope the next 25 years will see a great deal of work that aims to integrate these data by modeling the network of visual signals. We do not know what such theories will look like, but the characterization of human retinotopic maps from the last 25 years is likely to be an important part of future ideas about visual computations.     

静息态功能磁共振成像在青光眼疾病中的应用研究进展

青光眼是全球第一大不可逆致盲性眼病,是一组以特征性视神经损伤和视野缺损为共同特征的神经眼科疾病。已有多项研究表明,青光眼的损害不仅局限于眼球局部视神经节细胞的凋亡,而且会累及大脑视皮层整个视觉通路,是一种全脑神经退行性疾病。近年来,功能性磁共振成像(functional magnetic resonance imaging,fMRI)技术飞速发展,将神经系统的解剖和功能相结合,使局部脑组织的损伤与脑功能的缺失对应起来,可以实现在无创条件下观察中枢神经系统解剖结构及功能变化,为青光眼病理机制的研究提供了有效证据。而静息态功能磁共振成像(resting-state functional magnetic resonance imaging, rs-fMRI)作为神经影像学的热点研究技术,为探讨青光眼患者视觉相关脑区的解剖结构、代谢以及功能改变提供了影像学支持。本综述主要讨论了rs-fMRI的基本原理以及低频振幅(amplitude of low-frequency fluctuation, ALFF)、局部一致性(regional homogeneity, ReHo)、度中心度(degree centrality, DC)、功能连接(functional connectivity, FC)等几种较为常用的分析方法在青光眼中应用的研究进展。     

Mirror,mirror on the wall,can the brain tell right from left at all?

A reflection on the difficulties associated with the differentiation of right from left in visual space and the way in which these difficulties are changed by looking at a mirror image. This leads to a consideration of how signals from right and left fields are stored in the visual regions of the cerebral cortex and the role of different functional streams in the storage and retrieval of this information. Attention is directed to the way in which the use of mirror images may influence the interpretation of visually‐based behaviour following defects in the functional streams in the brain.