人类视觉对比度分辨率的非线性补偿

将在暗视觉条件下获得的人类视觉不能分辨的不同灰度的信息,放在恰可分辨的灰度水平上,对暗视觉条件下人类视觉的低对比度分辨率进行非线性补偿.经过对暗视觉条件下人类视觉的低对比度分辨率进行非线性补偿后,原来人类视觉不能分辨的不同灰度的信息就清楚可辨.结果提示暗视觉条件下人类视觉的对比度分辨率的非线性补偿方法,可显著改善暗视觉条件下人类视觉的对比度分辨率.该方法可用于提高微光夜视系统和反隐形系统的功能.     

人格特质与注意偏向研究进展

人类的视觉系统对资源加工的有限性要求必须对要加工的信息进行选择和取舍.通过注意选择,对与任务、目的相关的信息进行比较、抑制、整合,排除无关信息的干扰,以简洁、灵活的方式实现特定的目标.     

图命名的视觉语言加工双流模型

正三十多年前,Ungerleider和Mishkin根据恒河猴颞叶下部和顶叶损伤的不同行为,提出颞枕腹侧进行视觉物体识别,而背侧顶叶进行空间视觉加工的视觉双流模型~([1])。在人类,Duffau等~([2])在神经外科手术中实施直接电刺激的同时,让清醒患者图命名时观察到图命名产生的语义错语与视觉腹     

人类大脑皮层对人物肖像和风景识别的fMRI研究

目的探讨人类大脑对物体的识别功能区集中在大脑皮层的位置.方法使用了三种黑白图片:人物肖像、自然风景和打乱的图片给9例均为右利手的正常人观看,同时用1.5 T MRI仪采集实验对象的解剖像、三维全脑结构像和功能像.实验结果用功能神经成像分析软件 (AFNI)进行数据处理及分析.结果在腹侧颞叶(梭状回)后部存在两个相邻的区域分别对风景和人物敏感,其中靠内侧的区域对风景刺激的反应更强烈,靠外侧的区域则对人物刺激的反应更强;而且风景相关区域和人物相关区域呈现出从内侧到外侧的一种渐变过渡的分布.结论尽管参与人物视觉加工的脑区和参与风景视觉加工的脑区对不同的两种刺激的反应强度有所不同,但两个脑区并不截然分开,而是连续分布并相互重叠的.     

人工视觉假体映像信息处理模型

人工视觉是目前生物医学工程、组织工程及计算机科学等领域的热门研究课题.通过在视觉通路的不同部位植入视觉假体使盲人恢复部分视觉功能是目前人工视觉领域主要的研究方法.尽管已有人工视觉相关的研究成果发表,但往往只是粗略地说明由视景图像进行编码给出微电极刺激信号,几乎没有对信息处理模型部分的具体介绍.视觉映像的信息处理机制是人工视觉研究中最重要的基础工作和核心技术之一,提出一个能根据反馈信息进行自适应调整的视觉信息处理系统模型尤为重要.文章在阐述人类视觉信息获取及处理原理的基础上,提出一种人工视觉映像信息处理模型.然后详细阐述这一模型在学习训练阶段和应用阶段的系统结构和关键技术.     

人体感觉机制的模型化与数字化

本文阐述了人体感觉系统原理,提出感觉机制的模型框图,并以视觉系统为例,探讨了视觉系统模型的数字化方法.感觉机制模型化和数字化可作为情绪、意识、认知等行为机制建模的基础.     

人类色觉过程连通线路框图的研究

<正>色盲和色弱是危害人类健康的视觉疾病,虽然现不少研究者根据视觉的三通道模型建立了色盲患者视觉的模型[1,2],提出了多种矫正方法[3-5],但人类色觉机理和色觉异常发病原因至今不明,至今尚未能建立色觉信息系统各层次的信息接收、信息转换、信息传递到视觉形成的"人类色觉过程连通线路框图",致使色觉研究进程缓慢。本研究依据人类色觉过程的机能解剖学和各层次的生理机能,采用实验     

同类图片命名中信息处理的脑磁图研究

目的:应用脑磁图(MEG)检查,探讨同类图片命名任务中大脑的时空激活模式,为临床言语治疗提供依据。方法:选取健康成年右利手受试者10例(男性5例,女性5例)。实验任务为出声命名相同类别的图片。应用磁共振(MRI)获取个体大脑结构图像,通过脑磁图(MEG)检测图片命名过程中,全脑在不同时间窗内的激活水平。结果:在特征提取和语义编码时间窗内,视觉系统和腹侧颞叶联合系统的激活水平显著高于内侧默认模式系统(P0.01),其中腹侧颞叶联合系统的左侧半球的激活水平显著高于右侧半球(P0.05);在语音编码及发音发声时间窗内,腹侧颞叶联合系统、额-顶系统、扣带回-岛盖系统、注意系统、视觉系统以及听觉系统的激活水平均显著高于内侧默认模式系统(P0.01),其中腹侧颞叶联合系统、额-顶系统和听觉系统的左侧半球的激活水平显著低于右侧半球(P0.05)。结论:同类图片命名任务中,大脑随时间出现偏侧化优势激活。左偏侧化出现在信息处理过程的前期,与视觉特征提取和语义加工有关;右偏侧化出现在信息处理过程的后期,与语音加工有关。语义腹侧流和语音背侧流的时空分离现象为临床精准治疗提供了依据。     

应用汉语失语症心理语言评价探查视觉性失语症伴纯失读的语言加工损害

目的:明确视觉性失语症伴纯失读患者的语言加工损害水平。方法:对1例视觉性失语症患者采用汉语失语症心理语言评价及其他相关检查进行语言评价。结果:①患者的基本视知觉、不同视点物体匹配的结构表征检查正常;②从视觉输入通达到详尽的语义受损,表现为视觉图命名障碍和视觉图—图联系困难;③将视觉词形转换为对应的语音表征受损,表现为视觉输入词朗读障碍;④将视觉词形映射到语义较听觉语音映射到语义受损更为显著,即字形输入词典到语义系统的联系受损更为严重,表现为视觉词—图匹配较听觉词—图匹配显著受损。结论:该例视觉性失语症患者的语言加工损害主要为从视觉输入(事物)通达到详尽的语义受损,以及将视觉字形通达到语义和语音表征受损。     

人工视觉系统的集成神经网络模型研究

以分析为基础,以综合为手段,借鉴图像处理、模式识别与计算机视觉的研究成果,提出视觉系统模型的实现方法,研究了由多个局部神经网络组装的复杂功能系统的设计和工作原理,从整体的定量的角度建立了视觉信息处理系统的集成人工神经网络模型.     

Functional activation of the infant cortex during object processing

A great deal is known about the functional organization of the neural structures that mediate visual object processing in the adult observer. These findings have contributed significantly to our conceptual models of object recognition and identification and provided unique insight into the nature of object representations extracted from visual input. In contrast, little is known about the neural basis of object processing in the infant. The current research used near-infrared spectroscopy (NIRS) as a neuroimaging tool to investigate functional activation of the infant cortex during an object processing task that has been used extensively with infants. The neuroimaging data revealed that the infant cortex is functionally specialized for object processing (i.e., individuation-by-feature) early in the first year but that patterns of activation also change between 3 and 12 months. These changes may reflect functional reorganization of the immature cortex or age-related differences in the cognitive processes engaged during the task.     

Neural correlates of perceptual completion of an artificial scotoma in human visual cortex measured using functional MRI

When a featureless achromatic target is placed on a textured pattern and steadily viewed in peripheral vision, after a few seconds it seems to fill-in with the surrounding texture, similar to the perceptual experience of patients with scotomas from damage to the visual pathways. Such “artificial scotomas” are thought to arise early in visual processing, but their neural basis in humans has not been fully explored. Here we used functional MRI to show that perceptual completion of an artificial scotoma is associated with selective reductions in activity in the retinotopic representation of the target in human primary visual cortex (V1) and area V2. Moreover, the persistence of signals associated with the target, even after perceptual completion had been reported, indicate the presence of a persistent representation of the now invisible target.     

Critical period for cross-modal plasticity in blind humans: a functional MRI study

The primary visual cortex (V1) in congenitally blind humans has been shown to be involved in tactile discrimination tasks, indicating that there is a shift in function of this area of cortex, but the age dependency of the reorganization is not fully known. To investigate the reorganized network, we measured the change of regional cerebral blood flow using 3.0 Tesla functional MRI during passive tactile tasks performed by 15 blind and 8 sighted subjects. There was increased activity in the postcentral gyrus to posterior parietal cortex and decreased activity in the secondary somatosensory area in blind compared with sighted subjects during a tactile discrimination task. This suggests that there is a greater demand for shape discrimination processing in blind subjects. Blind subjects, irrespective of the age at onset of blindness, exhibited higher activity in the visual association cortex than did sighted subjects. V1 was activated in blind subjects who lost their sight before 16 years of age, whereas it was suppressed in blind subjects who lost their sight after 16 years of age during a tactile discrimination task. This suggests that the first 16 years of life represent a critical period for a functional shift of V1 from processing visual stimuli to processing tactile stimuli. Because of the age-dependency, V1 is unlikely to be the "entry node" of the cortex for the redirection of tactile signals into visual cortices after blinding. Instead, the visual association cortex may mediate the circuitry by which V1 is activated during tactile stimulation.     

局灶性脑损害患者视觉注意环路的小世界网络属性分析

摘要 目的：探讨局灶性脑损害患者视觉注意网络的连通性及其小世界特征。 方法：对2例局灶性后顶叶损害、2例背外侧前额叶损害、2例颞叶损害（其中1例为手术前后）和1例锥体束损害患者进行静息态fMRI检测,然后进行功能网络建立和小世界属性分析。 结果：所有局灶性脑损害患者的脑功能网络在给定阈值范围（0.05—0.5）内都具有小世界属性。局灶性后顶叶、背外侧前额叶、颞叶和锥体束损害患者之间,Gamma系数差异（P<0.05）和Sigma系数差异（P<0.01）均具有显著性意义。 结论：小世界网络分析为视觉注意网络的连通性研究提供了一个非常有价值的方法。我们推测,小世界网络检测方法应该可以作为局灶性脑损害神经功能损害的影像学生物标记。     

弱视磁共振成像研究进展

弱视长久以来被认为是一种皮质疾病,而非单纯眼部疾病,其发病机制仍未完全明确。磁共振成像(MRI)已广泛应用于神经科学研究,以评估疾病所致脑结构和功能的变化。利用MRI,研究人员可以非侵入性地检查视觉传入减少对整个视觉通路的影响,包括外侧膝状核、纹状体和纹外皮层。本文旨在综述应用MRI研究弱视的结构、化学和功能的影响。结构MRI已显示出在视觉和非视觉区域,弱视患者在灰质和白质密度存在明显的异常,枕叶与其他脑叶的网络连接也存在有异常。功能核MRI研究也为视觉丧失后整个视觉通路功能变化提供了广泛的证据。磁共振波谱成像(MRS)也在弱视中得到更多的应用。在未来,MRI很可能在评估弱视对视觉通路的影响以及病情如何进展方面发挥重要作用。     

Asymmetrical activation of human visual cortex demonstrated by functional MRI with monocular stimulation

We have demonstrated asymmetric activation patterns in the visual cortices of normal humans who have undergone functional MRI with monocular photic stimulation. The contralateral hemisphere is activated more strongly and to a greater spatial extent than the ipsilateral hemisphere when either eye is stimulated. This asymmetry can be explained by nasotemporal asymmetries which have been described in anatomical studies of the visual system in primates and humans. In part, the representation of the monocular crescent of the temporal hemifield of either eye, which exists only in the crossed projection, may explain this. In addition, within the binocular field, there is a biased crossed projection of nasal retinal ganglion cells which drive the contralateral ocular dominance columns in V1. Finally, the blind spot representation in the ipsilateral visual cortex may also contribute to the observed asymmetries. Our study may in effect provide a functional correlate of the anatomical asymmetries that have been observed in humans and animals.     

Automatized clustering and functional geometry of human parietofrontal networks for language, space, and number

Human functional MRI studies frequently reveal the joint activation of parietal and of lateral and mesial frontal areas during various cognitive tasks. To analyze the geometrical organization of those networks, we used an automatized clustering algorithm that parcels out sets of areas based on their similar profile of task-related activations or deactivations. This algorithm allowed us to reanalyze published fMRI data (Simon, O., Mangin, J.F., Cohen, L., Le Bihan, D., Dehaene, S., 2002. Topographical layout of hand, eye, calculation, and language-related areas in the human parietal lobe. Neuron 33, 475-487) and to reproduce the previously observed geometrical organization of activations for saccades, attention, grasping, pointing, calculation, and language processing in the parietal lobe. Further, we show that this organization extends to lateral and mesial prefrontal regions. Relative to the parietal lobe, the prefrontal functional geometry is characterized by a partially symmetrical anteroposterior ordering of activations, a decreased representation of effector-specific tasks, and a greater emphasis on higher cognitive functions of attention, higher-order spatial representation, calculation, and language. Anatomically, our results in humans are closely homologous to the known connectivity of parietal and frontal regions in the macaque monkey.     

Phase delays within visual cortex shape the response to steady-state visual stimulation

Although the spatial organization of visual areas can be revealed by functional Magnetic Resonance Imaging (fMRI), the synoptic, non-invasive access to the temporal characteristics of the information flow amongst distributed visual processes remains a technical and methodological challenge. Using frequency-encoded steady-state visual stimulation together with a combination of time-resolved functional magnetic source imaging from magnetoencephalography (MEG) and anatomical magnetic resonance imaging (MRI), this study evidences maps of visuotopic sustained oscillatory neural responses distributed across the visual cortex. Our results further reveal relative phase delays across responding striate and extra-striate visual areas, which thereby shape the chronometry of neural processes amongst these regions. The methodology developed in this study points at further developments in time-resolved analyses of distributed visual processes in the millisecond range, and to new ways of exploring the dynamics of functional processes within the human visual cortex non-invasively.     

Locating the functional and anatomical boundaries of human primary visual cortex

The primary visual cortex (V1) can be delineated both functionally by its topographic map of the visual field and anatomically by its distinct pattern of laminar myelination. Although it is commonly assumed that the specialized anatomy V1 exhibits corresponds in location with functionally defined V1, demonstrating this in human has not been possible thus far due to the difficulty of determining the location of V1 both functionally and anatomically in the same individual. In this study we use MRI to measure the anatomical and functional V1 boundaries in the same individual and demonstrate close agreement between them. Functional V1 location was measured by parcellating occipital cortex of 10 living humans into visual cortical areas based on the topographic map of the visual field measured using functional MRI. Anatomical V1 location was estimated for these same subjects using a surface-based probabilistic atlas derived from high-resolution structural MRI of the stria of Gennari in 10 intact ex vivo human hemispheres. To ensure that the atlas prediction was correct, it was validated against V1 location measured using an observer-independent cortical parcellation based on the laminar pattern of cell density in serial brain sections from 10 separate individuals. The close agreement between the independent anatomically and functionally derived V1 boundaries indicates that the whole extent of V1 can be accurately predicted based on cortical surface reconstructions computed from structural MRI scans, eliminating the need for functional localizers of V1. In addition, that the primary cortical folds predict the location of functional V1 suggests that the mechanism giving rise to V1 location is tied to the development of the cortical folds.     

Concurrent CBF and CMRGlc changes during human brain activation by combined fMRI-PET scanning

A novel approach for concurrent measurement of regional cerebral blood flow (CBF) and regional cerebral metabolic rate for glucose consumption (CMRGlc) in humans is proposed and validated in normal subjects during visual stimulation. 18F-labeled fluorodeoxyglucose was administered during the measurement of CBF by continuous arterial spin labeled magnetic resonance imaging (MRI). Subsequent positron emission tomographic (PET) scanning demonstrated the distribution of labeled deoxyglucose during the MRI acquisition. An excellent concordance between regional CBF and regional CMRGlc during visual stimulation was found, consistent with previously published PET findings. Although initially validated using a brief, non-quantitative protocol, this approach can provide quantitative CBF and CMRGlc, with a broad range of potential applications in functional physiology and pathophysiology.