Backward spreading of memory-retrieval signal in the primate temporal cortex

Bidirectional signaling between neocortex and limbic cortex has been hypothesized to contribute to the retrieval of long-term memory. We tested this hypothesis by comparing the time courses of perceptual and memory-retrieval signals in two neighboring areas in temporal cortex, area TE (TE) and perirhinal cortex (PRh), while monkeys were performing a visual pair-association task. Perceptual signal reached TE before PRh, confirming its forward propagation. In contrast, memory-retrieval signal appeared earlier in PRh, and TE neurons were then gradually recruited to represent the sought target. A reasonable interpretation of this finding is that the rich backward fiber projections from PRh to TE may underlie the activation of TE neurons that represent a visual object retrieved from long-term memory.     

Unsupervised natural experience rapidly alters invariant object representation in visual cortex

Object recognition is challenging because each object produces myriad retinal images. Responses of neurons from the inferior temporal cortex (IT) are selective to different objects, yet tolerant ("invariant") to changes in object position, scale, and pose. How does the brain construct this neuronal tolerance? We report a form of neuronal learning that suggests the underlying solution. Targeted alteration of the natural temporal contiguity of visual experience caused specific changes in IT position tolerance. This unsupervised temporal slowness learning (UTL) was substantial, increased with experience, and was significant in single IT neurons after just 1 hour. Together with previous theoretical work and human object perception experiments, we speculate that UTL may reflect the mechanism by which the visual stream builds and maintains tolerant object representations.     

Neuronal correlates of subjective visual perception

Neuronal activity in the superior temporal sulcus of monkeys, a cortical region that plays an important role in analyzing visual motion, was related to the subjective perception of movement during a visual task. Single neurons were recorded while monkeys (Macaca mulatta) discriminated the direction of motion of stimuli that could be seen moving in either of two directions during binocular rivalry. The activity of many neurons was dictated by the retinal stimulus. Other neurons, however, reflected the monkeys' reported perception of motion direction, indicating that these neurons in the superior temporal sulcus may mediate the perceptual experience of a moving object.     

Detecting fruits in natural scenes by using spatial-frequency based texture analysis and multiview geometry

This paper describes a computer vision based model for object detection that can serve as a preliminary step in fruit prognosis, which involves the estimation of the number, diameter and yield of apple fruits. In order to overcome the recognition unreliability in uncontrolled environments caused by uneven illumination conditions, partly occluded surfaces, and similar background features, we rely on a combination of the object's colour, texture and 3D shape properties. In our research, we apply colour segmentation to multiple scene snapshots to separate potential regions from the background and verify them first with texture analysis and second by reconstructing them to 3D space. By analysing all three distinct features (colour, texture and 3D shape) of possible areas, we can safely conclude if they represent fruits we are looking for. Once we detect and verify all areas representing fruits, we can measure their size and model estimated fruit yield.     

Functional specialization in rhesus monkey auditory cortex

Neurons in the lateral belt areas of rhesus monkey auditory cortex prefer complex sounds to pure tones, but functional specializations of these multiple maps in the superior temporal region have not been determined. We tested the specificity of neurons in the lateral belt with species-specific communication calls presented at different azimuth positions. We found that neurons in the anterior belt are more selective for the type of call, whereas neurons in the caudal belt consistently show the greatest spatial selectivity. These results suggest that cortical processing of auditory spatial and pattern information is performed in specialized streams rather than one homogeneously distributed system.     

Neural correlates for perception of 3D surface orientation from texture gradient

A goal in visual neuroscience is to reveal how the visual system reconstructs the three-dimensional (3D) representation of the world from two-dimensional retinal images. Although the importance of texture gradient cues in the process of 3D vision has been pointed out, most studies concentrate on the neural process based on binocular disparity. We report the neural correlates of depth perception from texture gradient in the cortex. In the caudal part of the lateral bank of intraparietal sulcus, many neurons were selective to 3D surface orientation defined by texture gradient, and their response was invariant over different types of texture pattern. Most of these neurons were also sensitive to a disparity gradient, suggesting that they integrate texture and disparity gradient signals to construct a generalized representation of 3D surface orientation.     

Parallel and serial neural mechanisms for visual search in macaque area V4

To find a target object in a crowded scene, a face in a crowd for example, the visual system might turn the neural representation of each object on and off in a serial fashion, testing each representation against a template of the target item. Alternatively, it might allow the processing of all objects in parallel but bias activity in favor of those neurons that represent critical features of the target, until the target emerges from the background. To test these possibilities, we recorded neurons in area V4 of monkeys freely scanning a complex array to find a target defined by color, shape, or both. Throughout the period of searching, neurons gave enhanced responses and synchronized their activity in the gamma range whenever a preferred stimulus in their receptive field matched a feature of the target, as predicted by parallel models. Neurons also gave enhanced responses to candidate targets that were selected for saccades, or foveation, reflecting a serial component of visual search. Thus, serial and parallel mechanisms of response enhancement and neural synchrony work together to identify objects in a scene. To find a target object in a crowded scene, a face in a crowd for example, the visual system might turn the neural representation of each object on and off in a serial fashion, testing each representation against a template of the target item. Alternatively, it might allow the processing of all objects in parallel but bias activity in favor of those neurons that represent critical features of the target, until the target emerges from the background. To test these possibilities, we recorded neurons in area V4 of monkeys freely scanning a complex array to find a target defined by color, shape, or both. Throughout the period of searching, neurons gave enhanced responses and synchronized their activity in the gamma range whenever a preferred stimulus in their receptive field matched a feature of the target, as predicted by parallel models. Neurons also gave enhanced responses to candidate targets that were selected for saccades, or foveation, reflecting a serial component of visual search. Thus, serial and parallel mechanisms of response enhancement and neural synchrony work together to identify objects in a scene.     

Single neurons in the monkey hippocampus and learning of new associations

The medial temporal lobe is crucial for the ability to learn and retain new declarative memories. This form of memory includes the ability to quickly establish novel associations between unrelated items. To better understand the patterns of neural activity during associative memory formation, we recorded the activity of hippocampal neurons of macaque monkeys as they learned new associations. Hippocampal neurons signaled learning by changing their stimulus-selective response properties. This change in the pattern of selective neural activity occurred before, at the same time as, or after learning, which suggests that these neurons are involved in the initial formation of new associative memories.     

Visual receptive fields of neurons in inferotemporal cortex of the monkey

Neurons in inferotemporal cortex (area TE) of the monkey had visual receptive fields which were very large (greater than 10 by 10 degrees) and almost always included the fovea. Some extended well into both halves of the visual field, while others were confined to the ipsilateral or contralateral side. These neurons were differentially sensitive to several of the following dimensions of the stimulus: size and shape, color, orientation, and direction of movement.     

Lentivirus Mediated Gene Manipulation in Trophectoderm of Porcine Embryos

Development of tools that can manipulate gene expression specifically and efficiently in the trophectoderm（TE） lineage would greatly aid understanding the roles of different genetic pathways in TE versus embryonic lineages. Here, we showed first time that short-term lentivirus infection of porcine blastocysts could lead to rapid expression of transgene specifically in TE cells. Efficient TE-specific gene knockdown could also be achieved by lentivirus-mediated pol III-driven short hairpin RNA（shRNA） and TE-specific gene expression could be temporal controlled efficiently by combining this system with Tet-On system. This lentivirus lineage-specific infection system would facilitate gene function studies in porcine pre-implatation embryos by specifically knockdown or overexpression of these genes in TE.     

Integrating what and when across the primate medial temporal lobe

Episodic memory or memory for the detailed events in our lives is critically dependent on structures of the medial temporal lobe (MTL). A fundamental component of episodic memory is memory for the temporal order of items within an episode. To understand the contribution of individual MTL structures to temporal-order memory, we recorded single-unit activity and local field potential from three MTL areas (hippocampus and entorhinal and perirhinal cortex) and visual area TE as monkeys performed a temporal-order memory task. Hippocampus provided incremental timing signals from one item presentation to the next, whereas perirhinal cortex signaled the conjunction of items and their relative temporal order. Thus, perirhinal cortex appeared to integrate timing information from hippocampus with item information from visual sensory area TE.     

柿AFLP银染技术体系的建立

通过对各主要影响因素的研究,建立了适于柿AFLP分析的银染技术体系:酶切体系20μL总体积中含纯化后的DNA450ng,EcoRI和MseI各3U,37℃酶切4h;酶切完成后加入连接液,37℃连接10h(或过夜),然后65℃变性10min;连接产物稀释5倍用于预扩增,预扩增体系中EcoRI和MseI引物均不含选择性碱基;预扩增产物稀释5倍用于选择性扩增,选择性扩增体系中EcoRI和MseI引物均含3个选择性碱基,选择性扩增完成后,加入10μLLoadingbuffer,95℃变性10min,立即冰浴;取6 5μL变性后的选择性扩增产物在6%变性聚丙烯酰胺凝胶上电泳,电泳完毕后,对胶板进行固定、脱色、水洗、银染、冲洗、显影、定影及干燥等银染程序。     

植物三维形态交互式设计软件需求分析探讨

数字植物是当前植物学研究的热点问题之一,植物三维形态结构建模是数字植物研究面临的首要问题,三维形态交互式设计是实现数字植物形态结构建模的重要技术手段之一。而面向科学研究、高校教学、品种推广、技术培训、虚拟仿真不同应用领域,对植物三维形态交互式设计软件产生不同的需求。本文对植物三维形态交互式设计任务和目标进行分析,并结合现有研究成果和应用实例,对相应的植物三维形态设计系统软件的系统设置、形态设计、动态模拟、可视化展示与计算等方面的需求进行探讨,以期为植物三维形态设计乃至植物虚拟仿真技术提供技术参考。     

Selective attention gates visual processing in the extrastriate cortex

Single cells were recorded in the visual cortex of monkeys trained to attend to stimuli at one location in the visual field and ignore stimuli at another. When both locations were within the receptive field of a cell in prestriate area V4 or the inferior temporal cortex, the response to the unattended stimulus was dramatically reduced. Cells in the striate cortex were unaffected by attention. The filtering of irrelevant information from the receptive fields of extrastriate neurons may underlie the ability to identify and remember the properties of a particular object out of the many that may be represented on the retina.     

保持双向等价关系的变换半群的若干结果

设X为任意集合,E是X上的一个等价关系.TX表示X上的全变换半群.令TE*(X)={f∈TX:对任意x,y∈X,(x,y)∈E当且仅当(f(x),f(y))∈E},则TE*(X)是TX的一个子半群.文章研究了TE*(X)是富足半群的条件,并描述了使得在半群TE*(X)中有D=J的X上的等价关系E.     

大型斜式轴流泵站进水流道的优化设计

本文建立了表达大型泵站进水流道三维可变形状的数学模型,并对各种不同形状斜式边水流道内的流场进行了有限元计算,以流道出口断面的流速不均匀度最小为优化设计的目标,在流道主要线性尺寸一定的前提下,获得最佳的斜式进水流道型线。     

Representation of perceived object shape by the human lateral occipital complex

The human lateral occipital complex (LOC) has been implicated in object recognition, but it is unknown whether this region represents low-level image features or perceived object shape. We used an event-related functional magnetic resonance imaging adaptation paradigm in which the response to pairs of successively presented stimuli is lower when they are identical than when they are different. Adaptation across a change between the two stimuli in a pair provides evidence for a common neural representation invariant to that change. We found adaptation in the LOC when perceived shape was identical but contours differed, but not when contours were identical but perceived shape differed. These data indicate that the LOC represents not simple image features, but rather higher level shape information.     

Surface-plasmon holography with white-light illumination

The recently emerging three-dimensional (3D) displays in the electronic shops imitate depth illusion by overlapping two parallax 2D images through either polarized glasses that viewers are required to wear or lenticular lenses fixed directly on the display. Holography, on the other hand, provides real 3D imaging, although usually limiting colors to monochrome. The so-called rainbow holograms--mounted, for example, on credit cards--are also produced from parallax images that change color with viewing angle. We report on a holographic technique based on surface plasmons that can reconstruct true 3D color images, where the colors are reconstructed by satisfying resonance conditions of surface plasmon polaritons for individual wavelengths. Such real 3D color images can be viewed from any angle, just like the original object.     

Three-dimensional structure identified from single sections

Errors in the identification of objects have been made frequently because of faulty interpretation of their flat images or sections. Such errors are perpetuated through a strange psychological chain reaction. 1) The first author who observes sections of an object, although presenting faithful pictures of sections of it, identifies its shape incorrectly. Such an initial mistake may be due to identification of the flat image with the object itself or to failure to consider the shape of the image as a function of the shape of the real object and the angle and level of cutting. 2) The first author describes verbally his personal concept of the object. 3) The reader reads the text of a publication before or without examining the pictorial evidence. 4) The reader's belief in the authority of the printed word immunizes him against critical evaluation of the evidence. 5) The reader regards a published opinion as a "fact." 6) A mechanism of suppression of new evidence is set up in the brain of the reader in favor of previously published, verbalized concepts. His brain unconsciously rejects new concepts that might arise intracerebrally. The printed word supersedes visual evidence. 7) A secondary mechanism parallels steps 3 to 6. An observer notices an unfamiliar figure in the microscope. Following established procedures for scientific investigations, he refrains from forming an opinion about his observation. Instead he rushes to the library searching for similar, published observations. If he finds a previous report about a similar shape, he accepts it as a "fact" and he "confirms" the previously printed viewpoint. Let me interject a personal experience concerning this mechanism. I investigated the arrangement of blood vessels in the human liver by means of corrosion preparations. The work was divided between an assistant and me. He was assigned the task of preparing drawings of two specimens. In his drawings he showed a structure which was absent from the specimens but had been described in a previous publication. This article shows simple ways for correct initial identification of shape and structure and for the breaking of the reverberating circuit of erroneous thinking.