错觉图形组成成分间的亮度对比和颜色对比对错觉程度的影响

用定量的心理物理测量方法,研究了错觉图形组成成分间的亮度对比和颜色对比方位错觉、长度觉及面积错觉幅度的影响。测试结果表明：与通常的错觉效应相比,当错觉图形组成成分间存在亮度对比或颜色对比（等亮度）时,受试者的错觉程度明显降低;其中,当存在颜色对比时,方位错觉的下降幅度更为显著,达到６９．３％。此外还观察到,在单纯亮度对比条件下,只需１．８％和５．３％的低对比度即可分别产生轮廓和边缘错觉;但在等亮度     

自由飞行蜜蜂对静止目标形状和颜色的综合识别能力

研究了蜜蜂对相同颜色和不同颜色目标图对的形状以及颜色的综合识别能力实验过程中,蜜蜂始终处于自由飞行状态.做为刺激目标使用的图对分别有相同颜色不同几何形状、相同颜色不同拓扑结构和不同颜色几何形状三组.主要结果有三点:(1)在相同颜色的条件下,蜜蜂可以分辨出图形的几何形状,并且识别能力与图对的相似程度成反比(2)在刺激图形为环形时,蜜蜂对图形平均亮度敏感;在平均亮度相同的情况下,对环形细节变和尺寸大小不敏感.(3)在不同颜色不同几何形状的刺激条件下.蜜蜂视觉信息加工过程中颜色因素会抑制几何形状因素而起主要作用.这三个结果可以视为深入研究颜色加工通道和几何形状加工通道之间内在关系的基础.     

猕猴在自由或限制条件下的视觉或听觉分辨学习

本工作观察了猕猴在自由或限制条件下学习视觉或听觉分辨的规律。在WGTA内动物对颜色分辨学习有很大的个体差异,主要表现为学习初期正确反应率在机率水平波动的持续时间的不同。猴在WGTA内完成亮暗、物体及图形分辨学习,以及在限制椅上完成颜色分辨学习也有类似情况。从同一只猴在WGTA内进行不同的视觉分辨任务的学习所得的结果表明,物体分辨和亮暗分辨学习比之颜色分辨学习要容易些,图形分辨学习则相对地比较困难。猴在限制椅上学习颜色分辨比在WGTA内需要更多的测试数。动物在限制椅上学习纯音音调分辨似乎更为困难。这些结果对神经精神药理学、心理生理学以及神经生理学研究中选择合适的动物实验模型有一定的参考价值。     

视动震颤(OKN)眼动控制系统中的颜色通道

用亮度相等的不同颜色构成的等亮度彩色运动条纹(Isoluminant chromatic moving gratings)来进行OKN眼动跟踪实验,探讨它是否与由亮度差别构成的黑白运动条纹图象一样引起OKN反应。实验结果表明在等亮度彩色运动条纹图象(没有亮度差别只有颜色差别)刺激下,视动系统可产生与黑白运动条纹刺激下同样的OKN反应,并且与各单原色运动条纹刺激下的OKN反应也一致。说明0KN眼动跟踪中的运动检测存在颜色通道。本文并提出了一种基于颜色的运动检测模型。     

朝向和对比度同时快速变化条件下的分辨能力

在自然的视觉中,投射到视网膜上的视觉图像总是在不停地变化,而人类的感知系统依然可以准确高效地识别物体.因此,人类的感知系统有相应的快速处理机制以应对这种动态变化．然而,前人的实验都是在相对稳定的刺激条件下研究人类被试的感知系统对一个刺激参数的反应,比如在固定对比度下测试朝向分辨能力,或在固定朝向测定对比度分辨能力,而朝向和对比度同时变化时,人类对这两个参数的分辨能力仍然缺乏研究．因此,在本实验中,我们使用朝向和对比度同时变化的刺激,研究了人类被试对朝向和对比度的分辨能力．结果表明,在这种动态变化的条件下,被试对朝向和对比度的分辨阈值都有显著性的降低．而且,朝向分辨阈值降低的幅度与在固定对比度参数条件下的分辨阈值成负相关,即在固定对比度条件下朝向分辨阈值较高的被试,在朝向和对比度同时变化条件下,其朝向分辨阈值降低的幅度相对要大,朝向分辨能力也就相对地提高更大．对比度分辨能力也呈现同样的规律．这些结果说明,朝向和对比度的同时变化提高了被试对朝向和对比度的分辨能力,一个参数变化时其分辨能力越低的被试,两个参数变化时其分辨能力提高的幅度就越大．揭示了视觉系统处理这种多刺激参量信息变化的能力和机制,对人类视觉系统在真实的视觉过程中如何处理朝向和对比度信息提供了认识．     

DNA序列的“双符三阶”图形编码

DNA的图形编码是在几何意义下,在不同位置,用不同的标记符号及不同的方向线段,对DNA的序列进行编码．DNA图形编码相对于DNA的字符编码而言,具有直观、简明、形象和便于比较局部DNA序列的相似性等特点。在分析已知各类：DNA的图形表示模式的基础上,提出一种DNA序列的“双符三阶”图形编码,并以此对一些特异DNA编码序列进行分析。DNA图形编码与DNA字符编码呈一一对应关系,具有简便易行、编译方便、形象丰富、便于比较等优点。适用于DNA短序列的相似性检测与分析,在生物信息学上有一定的应用前景。     

基于图像几何变换映射的色盲矫正方法

为了提高色盲患者分辨色彩的能力,提出了基于图像几何变换映射的色盲矫正方法。首先根据图像中颜色面两侧的颜色比例对颜色空间各个平面进行相应的几何变换,进而划分不同的颜色映射区域,通过颜色变换,生成色盲患者较易分辨颜色的图像。实验表明,该方法可以改善色盲患者对原本难以区分的颜色的分辨能力,同时计算速度快,有望满足实时处理的需要,性能上优于已有的方法。     

同心圆感受野去抑制特性的数学模拟

以感受野外周区内各亚区之间的抑制性相互作用为基础,提出了一个能描述视网膜神经节细胞传输特性的数学模型,此模型能很好地解释传统感受野外大范围去抑制区产生的机制。当用来处理亮度对比边缘时,它既能很好地增强边缘对比,又可有效地提升被传统感受野中心／外周拮抗机制所滤除了的区域亮度对比和亮度梯度信息。本文也用不同空间频率的光栅和真实图像检验了模型的空间频率传递特性,并与其它模型进行了比较。     

高浓度葡萄糖对C57小鼠视网膜神经节细胞的视觉反应特性的影响——一项离体生理研究

本研究旨在观察视网膜神经节细胞在高浓度葡萄糖下的视觉反应特性.实验中,视杯平铺于记录腔,Ames缓冲液灌流,单细胞外记录小鼠(Mus musculus)视网膜神经节细胞.实验结果表明,高糖条件下,ON神经节细胞的平均感受野大小(34.1±2.9,n=14)明显小于OFF神经节细胞的(49.3±0.3,n=12)(P0.0001).高渗条件下,可以观察到类似的模式,即ON神经节细胞的平均感受野大小小于OFF的(P0.0001).ON神经节细胞的平均亮度阈值在高糖(P0.0001)或者高渗(P0.0002)条件下明显升高.OFF神经节细胞的平均亮度阈值在相同条件下(高糖:P0.01;高渗:P0.0002)也有升高.在高渗条件下,ON神经节细胞的平均对比增益明显低于OFF神经节细胞的(P0.015).而在高糖条件下,ON神经节细胞的平均增益明显高于OFF神经节细胞的(P0.0001).这些结果表明,高糖可缩小神经节细胞的感受野,降低亮度敏感度,减弱对比增益.高糖对ON和OFF神经节细胞的影响可能是通过不同的机制进行的.     

酵母各属间颜色反应、尿素酶活性和发酵力的比较

本文对比了28个属、37个种、74株酵母的颜色反应、分解尿素能力以及发酵力的关系,并讨论了这些特性与其它特征(如DNA碱基组成等)的一致性。这种一致性说明了一些无孢子酵母的亲缘关系。     

On the contours of apparent motion: A new perspective on visual space-time

Previous results on the perception of motion indicate that perceived motion paths cannot be explained solely in terms of simple feature-specific analyzers. This is particularly true of apparent (phi) motion. In this paper we develop a dynamic network, with simple filtering and summation properties, which can predict the geometric paths of apparent motion in various spatio-temporal configurations. The network assumptions predict a non-Euclidean metric for the visual space-time of motion perception and we consider the implications of such distortions for various visual displays, including illusions.     

Dynamic decorrelation as a unifying principle for explaining a broad range of brightness phenomena

The visual system is highly sensitive to spatial context for encoding luminance patterns. Context sensitivity inspired the proposal of many neural mechanisms for explaining the perception of luminance (brightness). Here we propose a novel computational model for estimating the brightness of many visual illusions. We hypothesize that many aspects of brightness can be explained by a dynamic filtering process that reduces the redundancy in edge representations on the one hand, while non-redundant activity is enhanced on the other. The dynamic filter is learned for each input image and implements context sensitivity. Dynamic filtering is applied to the responses of (model) complex cells in order to build a gain control map. The gain control map then acts on simple cell responses before they are used to create a brightness map via activity propagation. Our approach is successful in predicting many challenging visual illusions, including contrast effects, assimilation, and reverse contrast with the same set of model parameters.     

Neural model of disinhibitory interactions in the modified Poggendorff illusion

Visual illusions can be strengthened or weakened with the addition of extra visual elements. For example, in the Poggendorff illusion, with an additional bar added, the illusory skew in the perceived angle can be enlarged or reduced. In this paper, we show that a nontrivial interaction between lateral inhibitory processes in the early visual system (i.e., disinhibition) can explain such an enhancement or degradation of the illusory effect. The computational model we derived successfully predicted the perceived angle in the Poggendorff illusion task that was modified to include an extra thick bar. The concept of disinhibition employed in the model is general enough that we expect it can be further extended to account for other classes of geometric illusions.     

Suppressed patterns alter vision during binocular rivalry

Binocular rivalry occurs when incongruent patterns are presented to corresponding regions of the retinas, leading to fluctuations of awareness between the patterns . One attribute of a stimulus may rival whereas another may combine between the eyes , but it is typically assumed that the dominant features are perceived veridically. Here, we show this is not necessarily the case and that a suppressed visual feature can alter dominant perception. The cortical representations of oriented gratings can interact even when one of them is perceptually suppressed, such that the perceived orientation of the dominant grating is systematically biased depending on the orientation of the suppressed grating. A suppressed inducing pattern has the same qualitative effect as a visible one, but suppression reduces effective contrast by a factor of around six. A simple neural model quantifies and helps explain these illusions. These results demonstrate that binocular rivalry suppression operates in a graded fashion across multiple sites in the visual hierarchy rather than truncating processing at a single site and that suppressed visual information can alter dominant vision in real-time.     

What are lightness illusions and why do we see them?

Lightness illusions are fundamental to human perception, and yet why we see them is still the focus of much research. Here we address the question by modelling not human physiology or perception directly as is typically the case but our natural visual world and the need for robust behaviour. Artificial neural networks were trained to predict the reflectance of surfaces in a synthetic ecology consisting of 3-D “dead-leaves” scenes under non-uniform illumination. The networks learned to solve this task accurately and robustly given only ambiguous sense data. In addition—and as a direct consequence of their experience—the networks also made systematic “errors” in their behaviour commensurate with human illusions, which includes brightness contrast and assimilation—although assimilation (specifically White's illusion) only emerged when the virtual ecology included 3-D, as opposed to 2-D scenes. Subtle variations in these illusions, also found in human perception, were observed, such as the asymmetry of brightness contrast. These data suggest that “illusions” arise in humans because (i) natural stimuli are ambiguous, and (ii) this ambiguity is resolved empirically by encoding the statistical relationship between images and scenes in past visual experience. Since resolving stimulus ambiguity is a challenge faced by all visual systems, a corollary of these findings is that human illusions must be experienced by all visual animals regardless of their particular neural machinery. The data also provide a more formal definition of illusion: the condition in which the true source of a stimulus differs from what is its most likely (and thus perceived) source. As such, illusions are not fundamentally different from non-illusory percepts, all being direct manifestations of the statistical relationship between images and scenes.     

A possible explanation of the low-level brightness–contrast illusions in the light of an extended classical receptive field model of retinal ganglion cells

The low-level brightness–contrast illusions constitute a special class within visual illusions. Speculations exist that these illusions may be processed through the filtering action of the retinal ganglion cells without necessitating much intervention from higher order processes of visual perception. Concept of the classical receptive field of the ganglion cell, derived from early physiological studies, prompted the idea that a Difference of Gaussian (DoG) model might explain the low-level illusions. In spite of its many successes, the DoG model fails to explain some of these illusions. It has been shown in this paper that it is possible to simulate those illusions with a model that takes into cognizance the role of the extended classical receptive field     

The plasticity of correspondence: After-effects,illusions and horopter shifts in depth perception

Retinal disparity is the cue for stereoscopic depth perception. Disparity detection begins with cortical single units driven binocularly from the two eyes. A previous paper (Nelson, 1975) has shown that inhibitory and facilitatory interactions are essential to insure successful disparity detection, particularly with repeating stimulus patterns, and that such a system will display all the appropriate properties of sensory fusion. This paper shows that most depth illusions occur as by-products of the same domain interactions. Such illusion effects fall into two classes: those caused by shifts in the distribution of activity along the appropriate sensory domain (here, the disparity domain) and those caused by changes in the average activity level within the domain. Profile shifts cause depth contrast illusions. The most important profile level change is an activity lowering due to disparity domain inhibition. This adversely affects fusional range (Panum's area). It is postulated that all domain interactions persist following cessation of stimulation. Persistent profile shifts cause depth after-effect illusions; persistent profile lowering is responsible for threshold elevation after-effects.Sensory fusion, the coding errors seen in illusions, the induced effect, and widespread failure to perceive depth from disparity input show that retinal correspondence is not stable in the normal individual. Yet horopter research has attempted to specify one set of retinal points as corresponding. Not surprisingly, horopter research shows systematic shifts in retinal correspondence linked to eye position. Small, simple, tonic modulations of the domain interactions responsible for so many other stereopsis system properties provide a satisfactory cortical mechanism for horopter changes.     

Detailed Analysis of Temporal Features on Contrast Enhanced Ultrasound May Help Differentiate Intrahepatic Cholangiocarcinoma from Hepatocellular Carcinoma in Cirrhosis

Aim

To verify if detailed analysis of temporal enhancement patterns on contrast enhanced ultrasound (CEUS) may help differentiate intrahepatic cholangiocarcinoma (ICC) from hepatocellular carcinoma (HCC) in cirrhosis.

Methods

Thirty three ICC and fifty HCC in cirrhosis were enrolled in this study. The contrast kinetics of ICC and HCC was analyzed and compared.

Results

Statistical analysis did not reveal significant difference between ICC and HCC in the time of contrast first appearance and arterial peak maximum time. ICC displayed much earlier washout than that of HCC (47.93±26.45 seconds vs 90.86±31.26 seconds) in the portal phase, and most ICC (87.9%) showed washout before 60 seconds than HCC (16.0%). Much more ICC (78.8%) revealed marked washout than HCC (12.0%) while most HCC (88.0%) showed mild washout or no washout in late part of the portal phase (90–120 seconds). Twenty six out of thirty three ICC (78.8%) demonstrated both early washout(<60seconds) and marked washout in late part of the portal phase, whereas, only six of fifty HCC (12.0%)showed these temporal enhancement features (p = 0.000).When both early washout and marked washout in the portal phase are taken as diagnostic criterion for ICC, the diagnostic sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 78.8%,88.0%,81.3%,86.3%,and 84.3% respectively by CEUS.

Conclusions

Analysis of detailed temporal enhancement features on CEUS is helpful differentiate ICC from HCC in cirrhosis.If a nodule in cirrhotic liver displays hyper-enhancement in the arterial phase followed by early and marked washout in the portal phase, the nodule is highly suspicious of ICC rather than HCC.     

Characterization of in vitro gutlike organ formed from mouse embryonic stem cells

Using an embryoid body (EB) culture system, we have made a functional organlike cluster: the "gut" from embryonic stem (ES) cells (ES gut). There are many types of ES clusters, because ES cells have a pluripotent ability to develop into a wide range of cell types. Before inducing specific differentiation by exogenously added factors, we characterized comprehensive physiological and morphological properties of ES guts. Each ES gut has a hemispherical (or cystic) structure and exhibits spontaneous contractions [mean frequency: 13.5 ± 8.8 cycles per min (cpm)]. A dense distribution of interstitial cells of Cajal (ICC) was identified by c-Kit immunoreactivity, and specific subcellular structures of ICC and smooth muscle cells were identified with electron microscopy. ICC frequently formed close contacts with the neighboring smooth muscle cells and occasionally formed gap junctions with other ICC. Widely propagating intracellular Ca²⁺ concentration oscillations were generated in the ES gut from the aggregates of c-Kit immunopositive cells. Plateau potentials, possibly pacemaker potentials in ICC, and electrical slow waves were recorded for the first time. These events were nifedipine insensitive, as in the mouse gut. Our present results indicate that the rhythmic pacemaker activity generated in ICC efficiently spreads to smooth muscle cells and drives spontaneous rhythmic contractions of the ES gut. The present characterization of physiological and morphological properties of ES gut paves the way for making appropriate models to investigate the origin of rhythmicity in the gut. intracellular calcium concentration oscillation; interstitial cells of Cajal; peristalsis