Visual control of action but not perception requires analytical processing of object shape

The visual perception of object shape depends on 'holistic' processing in which a given dimension cannot be perceptually isolated from the other dimensions of the object. The visual control of action (such as grasping an object), however, which is mediated by cortical areas that are largely independent of those mediating conscious perception, must take into account only the most action-relevant dimension of an object without being misled by other non-relevant object features. Here we report the results of two experiments showing that vision for perception and vision for action deal with objects in a fundamentally different manner. We tested participants' ability to make perceptual judgements of the width of different rectangular objects or to grasp them across their width, while in both cases ignoring length. Participants could not ignore length when making perceptual judgements of width but they could completely ignore length when grasping the same objects. These results suggest that in situations in which the elementary dimensions of an object's shape are perceived in a holistic manner, the same dimensions are treated analytically when a visually guided action is directed at that same object.     

Neural subsystems for object knowledge.

Critical issues in the cognitive neuroscience of language are whether there are multiple systems for the representation of meaning, perhaps organized by processing system (such as vision or language), and whether further subsystems are distinguishable within these larger ones. We describe here a patient (K.R.) with cerebral damage whose pattern of acquired deficits offers direct evidence for a major division between visually based and language-based higher-level representations, and for processing subsystems within language. K.R. could not name animals regardless of the type of presentation (auditory or visual), but had no difficulty naming other living things and objects. When asked to describe verbally the physical attributes of animals (for example, 'what colour is an elephant?'), she was strikingly impaired. Nevertheless, she could distinguish the correct physical attributes of animals when they were presented visually (she could distinguish animals that were correctly coloured from those that were not). Her knowledge of input stimulus. To explain this selective deficit, these data mandate the existence of two distinct representations of such properties in normal individuals, one visually based and one language-based. Furthermore, these data establish that knowledge of physical attributes is strictly segregated from knowledge of other properties in the language system.     

Body image as a visuomotor transformation device revealed in adaptation to reversed vision

People adapt with remarkable flexibility to reversal of the visual field caused by prism spectacles. With sufficient time, this adaptation restores visually guided behaviour and perceptual harmony between the visible and tactile worlds. Although it has been suggested that seeing one's own body is crucial for adaptation, the underlying mechanisms are unclear. Here we show that a new representation of visuomotor mapping with respect to the hands emerges in a month during adaptation to reversed vision. The subjects become bi-perceptual, or able to use both new and old representations. In a visual task designed to assess the new hand representation, subjects identified visually presented hands as left or right by matching the picture to the representation of their own hands. Functional magnetic resonance imaging showed brain activity in the left posterior frontal cortex (Broca's area) that was unique to the new hand representations of both hands, together with activation in the intraparietal sulcus and prefrontal cortex. The emergence of the new hand representation coincided with the adaptation of perceived location of visible objects in space. These results suggest that the hand representation operates as a visuomotor transformation device that provides an arm-centred frame of reference for space perception.     

Electrophysiological measurement of rapid shifts of attention during visual search.

The perception of natural visual scenes that contain many objects poses computational problems that are absent when objects are perceived in isolation. Vision researchers have captured this attribute of real-world perception in the laboratory by using visual search tasks, in which subjects search for a target object in arrays containing varying numbers of non-target distractor objects. Under many conditions, the amount of time required to detect a visual search target increases as the number of objects in the stimulus array increases, and some investigators have proposed that this reflects the serial application of attention to the individual objects in the array. However, other investigators have argued that this pattern of results may instead be due to limitations in the processing capacity of a parallel processing system that identifies multiple objects concurrently. Here we attempt to address this longstanding controversy by using an electrophysiological marker of the moment-by-moment direction of attention-the N2pc component of the event-related potential waveform--to show that attention shifts rapidly among objects during visual search.     

杜夫海纳审美对象理论述评

杜夫海纳的审美对象理论是在批判和继承现象学美学家的有关理论的基础上建立起来的。他将审美对象看作是一种知觉对象，认为审美对象是一个层级性的结构性存在，是由自在的存在、自为的存在和为我们的存在相互关联而构成的一个整体。他企图从根本上纠正现象学此前的审美对象理论主观化的错误，恢复意向性在审美对象理论中的应有之义。     

Dissociable neural mechanisms supporting visual short-term memory for objects

Using visual information to guide behaviour requires storage in a temporary buffer, known as visual short-term memory (VSTM), that sustains attended information across saccades and other visual interruptions. There is growing debate on whether VSTM capacity is limited to a fixed number of objects or whether it is variable. Here we report four experiments using functional magnetic resonance imaging that resolve this controversy by dissociating the representation capacities of the parietal and occipital cortices. Whereas representations in the inferior intra-parietal sulcus (IPS) are fixed to about four objects at different spatial locations regardless of object complexity, those in the superior IPS and the lateral occipital complex are variable, tracking the number of objects held in VSTM, and representing fewer than four objects as their complexity increases. These neural response patterns were observed during both VSTM encoding and maintenance. Thus, multiple systems act together to support VSTM: whereas the inferior IPS maintains spatial attention over a fixed number of objects at different spatial locations, the superior IPS and the lateral occipital complex encode and maintain a variable subset of the attended objects, depending on their complexity. VSTM capacity is therefore determined both by a fixed number of objects and by object complexity.     

fMRI evidence for objects as the units of attentional selection.

Contrasting theories of visual attention emphasize selection by spatial location, visual features (such as motion or colour) or whole objects. Here we used functional magnetic resonance imaging (fMRI) to test key predictions of the object-based theory, which proposes that pre-attentive mechanisms segment the visual array into discrete objects, groups, or surfaces, which serve as targets for visual attention. Subjects viewed stimuli consisting of a face transparently superimposed on a house, with one moving and the other stationary. In different conditions, subjects attended to the face, the house or the motion. The magnetic resonance signal from each subject's fusiform face area, parahippocampal place area and area MT/MST provided a measure of the processing of faces, houses and visual motion, respectively. Although all three attributes occupied the same location, attending to one attribute of an object (such as the motion of a moving face) enhanced the neural representation not only of that attribute but also of the other attribute of the same object (for example, the face), compared with attributes of the other object (for example, the house). These results cannot be explained by models in which attention selects locations or features, and provide physiological evidence that whole objects are selected even when only one visual attribute is relevant.     

Masking unveils pre-amodal completion representation in visual search

When one object is partly occluded by another, its occluded parts are perceptually 'filled in', that is, the occluded object appears to continue behind its occluder. This process is known as amodal completion. The completion of a partially occluded object takes about 200 ms, and pre-completion information (that is, information from before amodal completion has occurred) exists in the visual system for that duration. It has been suggested, however, that observers cannot make use of this information, even when it is beneficial to do so: visual search for a target that appears to be partly occluded, for example, is slower than for a target that does not undergo occlusion, despite both targets being physically identical. Here we show that visual search does have access to pre-completion representations, but only for a limited time that depends on the size of the occluded region.     

Involvement of visual cortex in tactile discrimination of orientation.

The primary sense modalities (vision, touch and so on) are generally thought of as distinct. However, visual imagery is implicated in the normal tactile perception of some object properties, such as orientation, shape and size. Furthermore, certain tactile tasks, such as discrimination of grating orientation and object recognition, are associated with activity in areas of visual cortex. Here we show that disrupting function of the occipital cortex using focal transcranial magnetic stimulation (TMS) interferes with the tactile discrimination of grating orientation. The specificity of this effect is illustrated by its time course and spatial restriction over the scalp, and by the failure of occipital TMS to affect either detection of an electrical stimulus applied to the fingerpad or tactile discrimination of grating texture. In contrast, TMS over the somatosensory cortex blocked discrimination of grating texture as well as orientation. We also report that, during tactile discrimination of grating orientation, an evoked potential is recorded over posterior scalp regions with a latency corresponding to the peak of the TMS interference effect (about 180 ms). The findings indicate that visual cortex is closely involved in tactile discrimination of orientation. To our knowledge, this is the first demonstration that visual cortical processing is necessary for normal tactile perception.     

虚概念生成机制再探

虚概念是逻辑学概念论的重要组成部分。从认知信息加工角度，我们可以将虚概念的生成过程解析为若干环节；将虚概念理解为以感知表象、心理意念等认知组块，通过联想、想象等匹配机制产生的无现实反映对象的思维产品。匹配有不同的角度，虚概念有不同的类型，如有属性型、表象型与综合型等。     

Learning the parts of objects by non-negative matrix factorization.

Is perception of the whole based on perception of its parts? There is psychological and physiological evidence for parts-based representations in the brain, and certain computational theories of object recognition rely on such representations. But little is known about how brains or computers might learn the parts of objects. Here we demonstrate an algorithm for non-negative matrix factorization that is able to learn parts of faces and semantic features of text. This is in contrast to other methods, such as principal components analysis and vector quantization, that learn holistic, not parts-based, representations. Non-negative matrix factorization is distinguished from the other methods by its use of non-negativity constraints. These constraints lead to a parts-based representation because they allow only additive, not subtractive, combinations. When non-negative matrix factorization is implemented as a neural network, parts-based representations emerge by virtue of two properties: the firing rates of neurons are never negative and synaptic strengths do not change sign.     

Object-based attention determines dominance in binocular rivalry

A question of long-standing interest to philosophers, psychologists and neuroscientists is how the brain selects which signals enter consciousness. Binocular rivalry and attention both involve selection of visual stimuli, but affect perception quite differently. During binocular rivalry, awareness alternates between two different stimuli presented to the two eyes. In contrast, attending to one of two different stimuli impairs discrimination of the ignored stimulus, but without causing it to disappear from consciousness. Here we show that despite this difference, attention and rivalry rely on shared object-based selection mechanisms. We cued attention to one of two superimposed transparent surfaces and then deleted the image of one surface from each eye, resulting in rivalry. Observers usually reported seeing only the cued surface. They were also less accurate in judging unpredictable changes in the features of the uncued surface. Our design ensured that selection of the cued surface could not have resulted from spatial, ocular or feature-based mechanisms. Rather, attention was drawn to one surface, and this caused the other surface to be perceptually suppressed during rivalry. These results raise the question of how object representations compete during these two forms of perceptual selection, even as the features of those objects change unpredictably over time.     

Efficient and Robust Feature Model for Visual Tracking

Long duration visual tracking of targets is quite challenging for computer vision,because the environments may be cluttered and distracting.Illumination variations and partial occlusions are two main difficulties in real world visual tracking.Existing methods based on hostile appearance information cannot solve these problems effectively.This paper proposes a feature-based dynamic tracking approach that can track objects with partial occlusions and varying illumination.The method represents the tracked o...     

Perceived luminance depends on temporal context

Brightness--the perception of an object's luminance--arises from complex and poorly understood interactions at several levels of processing. It is well known that the brightness of an object depends on its spatial context, which can include perceptual organization, scene interpretation, three-dimensional interpretation, shadows, and other high-level percepts. Here we present a new class of illusion in which temporal relations with spatially neighbouring objects can modulate a target object's brightness. When compared with a nearby patch of constant luminance, a brief flash appears brighter with increasing onset asynchrony. Simultaneous contrast, retinal effects, masking, apparent motion and attentional effects cannot account for this illusory enhancement of brightness. This temporal context effect indicates that two parallel streams--one adapting and one non-adapting--encode brightness in the visual cortex.     

理性烛照下的心理分析--施蛰存小说浅议

从施蛰存小说创作的具体内容来看，无论是在选取文学表现对象的原则上，还是在文学把握现实的方式上．施蛰存都没有走向现代主义的非理性的极端，而是本着鲜明的理性精神来选取对象和把握现实的。他描写人物的内在心理活动，并不是因为他否认外部世界的可知性、可把握性，而恰恰是因为他希望通过对人内在心理世界的分析描写来获取探索人类心灵奥秘把握人的真实的本质的一种方式，以便更好地揭示生活的真相。     

视障青少年体育锻炼行为研究

本研究采用问卷调查法、访谈法、数理统计法,选择北京市2所学校13~23周岁的90名视障学生作调查对象,研究他们的体育锻炼情况,将数据进行统计分析,得出视障青少年体育锻炼的问题:主观上存在怕受伤、恐讥笑等顾虑;客观上存在着学校体育基础薄弱、家庭体育活动较少、社会锻炼条件不足等.提出的治理对策是,政府和社会要保障残障人的体育权利,加大对残疾人体育方面人财物的投入,创建无障碍运动环境,让残疾人享受体育锻炼带来的红利;学校要进行健康教育,让残疾人体会运动的乐趣;家长要带领残疾子女共同运动,使他们享受亲情的温暖.     

基于多粒度感知SVM的复杂场景人车分类方法

针对复杂场景中的人车分类问题, 提出一种基于多粒度感知SVM (support vector machine)的复杂场景人车分类方法。该方法首先对视频场景进行运动区域分析, 结合角点检测方法提取运动区域视觉感知信息, 在时空域中采用Kalman滤波将感知信息进行关联推理, 去除噪声干扰。 再以运动区域质心点为中心, 构造目标的多粒度感知特征, 最后构造2级SVM分类器, 将目标多粒度感知特征向量集输入SVM分类器进行训练及分类, 得到人车分类结果输出。实验结果表明, 该方法取得了良好的分类效果, 人、车全天候平均分类正确率分别达到93.6%以上, 能有效避免光照、色彩、目标大小等变化导致的误分类问题, 适用于智能交通视频的人车分类应用。     

A neurological dissociation between perceiving objects and grasping them

Studies of the visual capacity of neurological patients have provided evidence for a dissociation between the perceptual report of a visual stimulus and the ability to direct spatially accurate movements toward that stimulus. Some patients with damage to the parietal lobe, for example, are unable to reach accurately towards visual targets that they unequivocally report seeing. Conversely, some patients with extensive damage to primary visual cortex can make accurate pointing movements or saccades toward a stimulus presented in their 'blind' scotoma. But in investigations of visuomotor control in patients with visual disorders, little consideration has been given to complex acts such as manual prehension. Grasping a three-dimensional object requires knowledge not only of the object's spatial location, but also of its form, orientation and size. We have examined a patient with a profound disorder in the perception of such object qualities. Our quantitative analyses demonstrate strikingly accurate guidance of hand and finger movements directed at the very objects whose qualities she fails to perceive. These data suggest that the neural substrates for the visual perception of object qualities such as shape, orientation and size are distinct from those underlying the use of those qualities in the control of manual skills.     

视觉神经表征中底-顶和顶-底的双向激活——来自人与猴的实验证据

长期以来,建立在坚实生理学证据之上的底-顶加工说和特征检测理论在视觉研究中占主导地位。对于顶-底加工人们只能靠一般常识,即知识或经验通过激活记忆中的神经表征影响视觉过程。但是近年来,来自人和猴的研究为顶-底的加工提供了实验证据。 首先位于猴腹侧加工系统内的物体和面孔视觉记忆表征,提供了神经编码是怎样创立、组织和再激活的最佳实验证据。联想性编码是通过学习由一些具有特殊功能的神经元建立的,这些神经元具有将时间性关联刺激的表征联系起来的能力。其次,不仅来自视网膜的底-顶信号,而且来自前额叶的顶-底信号都能触发联想性编码的提取,既可以作为有意识回忆的神经基础,又是顶-底加工影响视觉过程的基础。脑损伤病人研究、具有高时间分辨率的人类功能性核磁共振成像(functional magnetic resonance imaging, fMRI)和猴fMRI研究以及猴细胞电生理分析相结合,将进一步加强人们对视觉脑机制的全面理解。     

基于形态学和盲源分离合成孔径雷达水体提取

采用一种新的基于独立分量分析(independentcomponent analysis,ICA)盲源分离(blind source separation,BSS)和形态学开重构(open reconstruction)的方法实现多极化合成孔径雷达(synthetic aperture radar,SAR)影像相干斑噪声抑制和水体目标快速提取.SAR影像具有强烈乘性相干斑噪声,影像数据为非高斯分布,具体分布形式未知.利用独立分量分析方法,不需要知道SAR影像的具体分布,通过对数量化将相干斑噪声转化为与图像数据相互独立的加性噪声,从多极化SAR影像中自动分离出图像数据与相干斑噪声,并自动选择相干斑指数最小的分量为图像分量.针对SAR影像水体目标的亮度及形状分布特征,进一步采用形态学开重构运算,从分离出的图像分量中提取出水体目标.利用ENVISAT ASAR多极化影像进行了实验,结果表明该方法可以快速准确地提取多极化SAR影像中的水体目标.