拓扑差异物体的构型处理：一项脑电研究

根据陈霖的拓扑知觉理论,在视觉感知中,拓扑差异的检测要快于局部特征的检测.本研究组认为,这一现象可能是对有＂洞＂图形和无＂洞＂图形的感知差异所造成的.本文旨在检验这两类图形所存在的知觉差异究竟是什么.利用脑电（ERP）技术,测量＂洞＂和＂非洞＂图形所引起的视觉诱发电位（VEP）,探究＂洞＂和＂非洞＂的区别.两类图形引起的VEP区别体现在N170上,＂洞＂图形的反转使得N170的潜伏期显著变化,而＂非洞＂图形的反转不会引起N170潜伏期的变化.人脸与非人脸物体的反转引起的N170变化与本结果相似.本研究认为,对＂洞＂的感知更偏向于整体加工,而对于＂非洞＂则更偏向于特征加工.     

视觉交变现象的神经动力学方程解释

视觉交变现象是视觉感知研究中一个有趣而至今尚未得到圆满解释的问题。多数学者认为交变感知的出现是由于图形-背景之间的交替。Dodcoell认为,象Necker立方体、Schroder梯子、Mach书和蜂窝图之类交变图产生的交变感知,是由于视觉系统中“边”或“线”之类特征检察器疲劳(衰退)引起的。而Vickers认为交变现象是视觉系统中对图形-背景的一种决策过程。本文从神经动力学方程出发,构造一个理论模型,解释视觉感知中的交变现象。设视觉系统由三层不同功能的神经细胞组     

拓扑不变性质在运动诱发视盲现象中的作用

知觉物体的定义是认知科学领域富有争议的中心问题之一．本研究通过运动诱发视盲(MIB)现象的研究发现：a．两个图形当它们是连通的,或位于同一个洞中,或是具有相同的洞的个数,更倾向于整体共同消失或重现;b．前景图形和背景图形的拓扑性质差异,较之非拓扑性质差异,显著地削弱MIB现象;c．相对于其他各种几何性质的变化,拓扑性质的变化能更快地被知觉到返回意识状态．这些结果揭示了拓扑性质定义的知觉物体是MIB过程操作的基本单元,提示了拓扑性质改变产生新知觉物体的表征可能是意识下的过程,进一步支持了知觉物体的拓扑学定义．     

连续闪现抑制下对洞的无意识知觉

大量收敛一致的实验证据表明,图形的大范围性质可以由拓扑性质来描述,并且其检测发生在视觉过程的最早期,这些证据几乎全部来自对意识上知觉的研究,而拓扑性质的意识下加工机制尚有待发掘.意识下知觉是人的感官系统客观上接受刺激呈现但主观上没有察觉的知觉,其机制和应用长期以来一直是知觉研究的热点.本文采用了一种双眼竞争的变式——连续闪现抑制,将待检测的刺激图形掩蔽,使之处于意识下状态,考察意识下知觉中拓扑性质的加工."洞的个数"作为一种拓扑性质是本文的研究对象.通过量度被抑制图形从发生变化到被知觉的被抑制时间,或者被试对被抑制的变化图形的正确检测率,我们发现,相比于不变或者各种非拓扑性质变化,意识下知觉中的拓扑性质(洞的个数)的变化会使图形更快、更容易被检测到.本研究揭示了拓扑性质(洞的个数)在意识下知觉中的优先性,将拓扑知觉理论从意识上知觉领域拓展到了意识下知觉领域,为拓扑性质加工的早期性提供了有力的证据;另一方面,本研究也提示了拓扑性质经由皮层下视通路加工处理的可能性.     

高速LED背光速视器揭示拓扑性质的快速加工

灵长类视觉系统能够非常有效地从环境中提取稳定的不变性特征,而不受各种变换与干扰的影响.这种不变性知觉的时间与动态过程为视觉理论提供了重要的约束.我们开发了一种高速发光二极管(LED)背光速视器,能够短暂呈现1 ms的视觉刺激,并以亚毫秒级精度调整刺激呈现时间.这使得我们可以通过控制视觉输入的可获取时间,估计感觉线索积累的心理物理曲线,从而研究在图形结构优势效应任务中,拓扑、射影、仿射和欧氏不变性的相对加工速度.实验结果表明拓扑不变性所需要的呈现时间最短,这与大范围首先理论的预测相一致.     

目标和干扰子之间的拓扑性质差异可以削弱拥挤效应

"拥挤效应"被认为是外周视觉物体辨认过程中的一个重要瓶颈.它是指当目标被干扰子包围,在外周视野呈现时,观察者辨认目标的能力被大大削弱,尤其是当目标和干扰子之间存在某种相似性时.许多研究分别试图在不同层次上提出解释这一现象的机制.本文通过三个实验,使用了不同的视觉刺激图形的辨认任务(例如,三角形和箭头的朝向判断、数字和字母的辨认以及S形图形的朝向辨认),测量了目标和干扰子之间中心距离的阈值,结果一致地发现,当目标和干扰子之间存在拓扑性质差异(洞的个数差异)时,拥挤效应会显著降低,并且排除了目标和干扰子之间的主观相似性、形状和面积差异等可能的因素.从知觉组织的角度验证了当目标和干扰子之间存在拓扑性质差异时,拥挤效应会显著降低,这是首次发现的一个影响拥挤效应的新的维度.本文结果不仅为拥挤效应的机制提供了一个新的解释,也为大范围首先拓扑知觉在知觉物体形成中的作用提供了支持性证据.     

主观轮廓感知在运动中的增强

主观轮廓现象的研究对于探讨人类视觉系统中物体识别的形成机制有着重要的意义. 众多研究表明, 在运动和体视中形成的主观轮廓, 是由于存在着不能匹配的部分而产生的. 通过心理物理实验的研究, 试图说明Kanizsa类型主观轮廓同样产生于不能匹配的信息. 实验中采用了不同运动方式(包括水平运动和收缩扩张运动)的Kanizsa主观轮廓. 结果表明, 无论在哪种运动方式下, 当图形和背景单独运动时, 主观轮廓的感知都得到了增强, 并且两种运动间没有产生明显的感知强度差异, 而在图形和背景同时运动的情况下, 则没有产生主观轮廓增强的现象. 通过分析发现, 运动中的主观轮廓增强效应是由于不能匹配信息的增强而产生的. 这就间接地表明, 视觉系统对于不能匹配信息的处理是主观轮廓形成过程中关键的步骤.     

铜绿丽金龟对圆偏振光的行为和视网膜电位反应

圆偏振光在地球环境中是很少见的, 来自珠宝金龟甲体壁反射圆偏振光是稀有的自然资源之一。铜绿丽金龟Anomala corpulenta Motschulsky与其他珠宝金龟甲一样其体壁能够反射左旋圆偏振光。为了解铜绿丽金龟对圆偏振光的感知能力, 本研究利用室内行为、 田间诱集与视网膜电位(electroretinogram, ERG)等方法研究了铜绿丽金龟对圆偏振光的响应。室内行为研究结果表明, 铜绿丽金龟对左旋圆偏振光与右旋圆偏振光的趋光反应明显低于非偏振光, 避光反应明显大于非偏振光, 且对左旋圆偏振光的趋、 避光反应均大于右旋圆偏振光。田间选择试验结果显示, 铜绿丽金龟对左旋和右旋圆偏振光的选择明显低于非偏振光, 且右旋大于左旋圆偏振光。电生理学研究结果表明, 左旋和右旋圆偏振光与非偏振光一样, 均能引发铜绿丽金龟的ERG反应, 且无明显差异。这些研究结果表明铜绿丽金龟体壁能够反射产生左旋圆偏振光, 且能够感知和区分左旋和右旋圆偏振光, 说明铜绿丽金龟存在偏振视觉, 具有圆偏振光敏感性。     

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.     

初级视皮层神经元集群对拓扑特征响应的可视化表征

神经元集群响应的高维特性是脑机制研究面临的主要困难之一.拓扑特征是图像的基本特征之一,为了有效表征高维的神经元集群响应的拓扑特征特性,提出了一种基于三维自组织映射网络采用RGB颜色特征表征神经元集群响应的动态可视化方法,分析多通道微电极阵列采集的大鼠初级视觉皮层(V1区)神经元集群信号,进而研究了V1区神经元集群对图形拓扑特征的响应特性.通过与主成分分析(PCA)方法进行对比发现:该方法能够有效表征V1区神经元集群对拓扑结构的时序动态响应特征,表征方式形象直观,具有一定的优越性.     

Visual discrimination of cues differing as for their number of elements, their shape or their orientation, by the ant Myrmica sabuleti

Using operant conditioning as a method, we study if Myrmica sabuleti workers can discriminate figures made of different numbers of the same element, different filled shapes or hollow forms and elements differently oriented. The ants effectively discriminate figures containing different numbers of the same element but without counting the elements: their distinguishing is based on the global aspect (dimensions, area) of the figures. They distinguish filled shapes as well as hollow forms when these look different if seen with convexity. For instance, they differentiate well between concave filled shapes or concave hollow forms. They see distinctly an element and the same one rotated if this element, seen with convexity, looks different after its rotation. They perceive until a 30° rotation of a vertical segment and until a 15° rotation of a horizontal segment. In conclusion, M. sabuleti workers are sensitive to the number of elements, dimension, shape, form and orientation of visual cues with the restriction that they probably see them with convexity.     

The visual perception of the ant Myrmica ruginodis (Hymenoptera: Formicidae)

Myrmica ruginodis workers are able to distinguish black or white circles from black or white squares, black or white ellipses from black or white rectangles as well as hollow circles or ellipses from hollow squares or rectangles. They can also distinguish differently oriented elements as well as objects containing a various number of elements. These workers are also able to perceive and discriminate transparent cues on a black background and even small luminous spots on a black ceiling. Such visual abilities are in agreement with the species?? eye morphology and system of navigation: the eyes are rather large with a well-developed posterio-dorsal part, and the foragers rely exclusively on cues located above them, neglecting odorous elements as long as visual perception is possible. Probably, they might use cues located in the canopy and the sky to travel in certain circumstances.     

Discrimination of coloured patterns by honeybees through chromatic and achromatic cues

We investigated pattern discrimination by worker honeybees, Apis mellifera, focusing on the roles of spectral cues and the angular size of patterns. Free-flying bees were trained to discriminate concentric patterns in a Y-maze. The rewarded pattern could be composed of either a cyan and a yellow colour, which presented both different chromatic and achromatic L-receptor contrast, or an orange and a blue colour, which presented different chromatic cues, but the same L-receptor contrast. The non-rewarded alternative was either a single-coloured disc with the colour of the central disc or the surrounding ring of the pattern, a checkerboard pattern with non-resolvable squares, the reversed pattern, or the elements of the training pattern (disc or ring alone). Bees resolved and learned both colour elements in the rewarded patterns and their spatial properties. When the patterns subtended large visual angles, this discrimination used chromatic cues only. Patterns with yellow or orange central discs were generalised toward the yellow and orange colours, respectively. When the patterns subtended a visual angle close to the detection limit and L-receptor contrast was mediating discrimination, pattern perception was reduced: bees perceived only the pattern element with higher contrast.     

Visual discrimination abilities in the gray bamboo shark (Chiloscyllium griseum)

This study assessed visual discrimination abilities in bamboo sharks (Chiloscyllium griseum). In a visual discrimination task using two-dimensional (2D) geometric stimuli, sharks learned to distinguish between a square, being the positive (rewarded) stimulus, and several negative stimuli, such as two differently sized triangles, a circle, a rhomboid and a cross. Although the amount of sessions to reach the learning criterion and the average trial time needed to solve each new task did not vary significantly, the number of correct choices per session increased significantly with on-going experiments. The results indicate that the sharks did not simply remember the positive stimulus throughout the different training phases. Instead, individuals also seemed to learn each negative symbol and possibly had to “relearn” at least some aspects of the positive stimulus during each training phase. The sharks were able to distinguish between the 2D stimulus pairs at a learning rate corresponding to that found in teleosts. As expected, it took the sharks longer to learn a reversal task (with the positive stimulus now being the negative one) than to discriminate between the other stimulus pairs. Nevertheless, the present results suggest that bamboo sharks can learn visual discrimination tasks, succeed in a reversal task and probably retain (some) information about a previously learned task when progressing to a new one.     

Evoked cortical potentials to simple and complex visual signals in children

The analysis of steadily recorded components of evoked potentials (EP) in different areas of cerebral cortex during tachistoscopic presentation of a homogeneous square, checker-board pattern and schematic drawings of human faces (face-pattern) of 6 degrees size was performed in children aged from 6,5 to 7 years. During contour detection, characterized by significant EP differences between responses to a checker-board pattern and a homogeneous square, the most pronounced changes were observed in the visual projection area of the cortex. Reaction to a complex visual stimulus, characterized by differences of EP to fase and checker-board patterns, had maximal manifestation in the temporo-parieto-occipital area. The changes observed during both operations were noted for EP components appearing up to 250 msec following stimulation. It is suggested that they are connected with the activity of cortical receptive fields. The data obtained are discussed on the basis of hypothesis of a difference between cortical mechanisms of single operations involved in visual perception.     

Quantifying Social Motivation in Mice Using Operant Conditioning

In this protocol, social motivation is measured in mice through a pair of operant conditioning paradigms. To conduct the experiments, two-chambered shuttle boxes were equipped with two operant levers (left and right) and a food receptacle in one chamber, which was then divided from the second chamber by an automated guillotine door covered by a wire grid. Different stimulus mice, rotated across testing days, served as a social stimulus behind the wire grid, and were only visible following the opening of the guillotine door. Test mice were trained to lever press in order to open the door and gain access to the stimulus partner for 15 sec. The number of lever presses required to obtain the social reward progressively increased on a fixed schedule of 3. Testing sessions ended after test mice stopped lever pressing for 5 consecutive minutes. The last reinforced ratio or breakpoint can be used as a quantitative measure of social motivation. For the second paradigm, test mice were trained to discriminate between left and right lever presses in order to obtain either a food reward or the social reward. Mice were rewarded for every 3 presses of each respective lever. The number of food and social rewards can be compared as a measurement of the value placed upon each reward. The ratio of each reward type can also be compared between mouse strains and the change in this ratio can be monitored within testing sessions to measure satiation with a given reward type. Both of these operant conditioning paradigms are highly useful for the quantification of social motivation in mouse models of autism and other disorders of social behavior.     

Perceptual grouping of biological motion promotes binocular rivalry

Investigation of perceptual rivalry between conflicting stimuli presented one to each eye can further understanding of the neural underpinnings of conscious visual perception. During rivalry, visual awareness fluctuates between perceptions of the two stimuli. Here, we demonstrate that high-level perceptual grouping can promote rivalry between stimulus pairs that would otherwise be perceived as nonrivalrous. Perceptual grouping was generated with point-light walker stimuli that simulate human motion, visible only as lights placed on the joints. Although such walking figures are unrecognizable when stationary, recognition judgments as complex as gender and identity can accurately be made from animated displays, demonstrating the efficiency with which our visual system can group dynamic local signals into a globally coherent walking figure. We find that point-light walker stimuli presented one to each eye and in different colors and configurations results in strong rivalry. However, rivalry is minimal when the two walkers are split between the eyes or both presented to one eye. This pattern of results suggests that processing animated walker figures promotes rivalry between signals from the two eyes rather than between higher-level representations of the walkers. This leads us to hypothesize that awareness during binocular rivalry involves the integrated activity of high-level perceptual mechanisms in conjunction with lower-level ocular suppression modulated via cortical feedback.     

Pattern recognition in honeybees: chromatic properties of orientation analysis

The spectral properties of the discrimination of pattern orientation in freely flying honeybees (Apis mellifera) were examined. Bees were trained to discriminate between two random black/white gratings oriented perpendicularly to each other, one of which was associated with a reward. Subsequently the bees were tested on two-colour gratings or gratings consisting of grey and coloured stripes, providing a range of different chromatic contrasts, luminance contrasts and specific channel contrasts. The results of these experiments indicate that orientation analysis in the honeybee is mediated almost exclusively by the green receptor channel, although the bee's visual system as a whole is endowed with excellent trichromatic colour vision.     

Configural processing of different topologically structured figures: an ERP Study

According to Chen’s theory, topological differences are perceived faster than feature differences in early visual perception. We hypothesized that topological perception is caused by the sensitivity in discriminating figures with and without “holes”. An ERP experiment was conducted utilizing a passive paradigm to investigate the differences in perceiving figures with “hole” and with “no-hole”. The results showed differences in N170 components between figures with “holes” and with “no-holes”. The inversion of the “hole” could influence the latency of N170, but the inversion of the “no-hole” could not, which indicated that global features are processed first in the “hole” perception whilst local features are given priority to the “no-hole” perception. This result was similar to studies concerning face and non-face objects, suggesting a configural processing of the “hole”.