Activation of specific interneurons improves V1 feature selectivity and visual perception

Inhibitory interneurons are essential components of the neural circuits underlying various brain functions. In the neocortex, a large diversity of GABA (γ-aminobutyric acid) interneurons has been identified on the basis of their morphology, molecular markers, biophysical properties and innervation pattern. However, how the activity of each subtype of interneurons contributes to sensory processing remains unclear. Here we show that optogenetic activation of parvalbumin-positive (PV+) interneurons in the mouse primary visual cortex (V1) sharpens neuronal feature selectivity and improves perceptual discrimination. Using multichannel recording with silicon probes and channelrhodopsin-2 (ChR2)-mediated optical activation, we found that increased spiking of PV+ interneurons markedly sharpened orientation tuning and enhanced direction selectivity of nearby neurons. These effects were caused by the activation of inhibitory neurons rather than a decreased spiking of excitatory neurons, as archaerhodopsin-3 (Arch)-mediated optical silencing of calcium/calmodulin-dependent protein kinase IIα (CAMKIIα)-positive excitatory neurons caused no significant change in V1 stimulus selectivity. Moreover, the improved selectivity specifically required PV+ neuron activation, as activating somatostatin or vasointestinal peptide interneurons had no significant effect. Notably, PV+ neuron activation in awake mice caused a significant improvement in their orientation discrimination, mirroring the sharpened V1 orientation tuning. Together, these results provide the first demonstration that visual coding and perception can be improved by increased spiking of a specific subtype of cortical inhibitory interneurons.     

Dynamics of travelling waves in visual perception

Nonlinear wave propagation is ubiquitous in nature, appearing in chemical reaction kinetics, cardiac tissue dynamics, cortical spreading depression and slow wave sleep. The application of dynamical modelling has provided valuable insights into the mechanisms underlying such nonlinear wave phenomena in several domains. Wave propagation can also be perceived as sweeping waves of visibility that occur when the two eyes view radically different stimuli. Termed binocular rivalry, these fluctuating states of perceptual dominance and suppression are thought to provide a window into the neural dynamics that underlie conscious visual awareness. Here we introduce a technique to measure the speed of rivalry dominance waves propagating around a large, essentially one-dimensional annulus. When mapped onto visual cortex, propagation speed is independent of eccentricity. Propagation speed doubles when waves travel along continuous contours, thus demonstrating effects of collinear facilitation. A neural model with reciprocal inhibition between two layers of units provides a quantitative explanation of dominance wave propagation in terms of disinhibition. Dominance waves provide a new tool for investigating fundamental cortical dynamics.     

基于人眼视觉系统的运动图像视觉感知模拟

讨论了人眼在观看平板显示屏上运动图像时视觉失真的产生原因,并通过视觉感知实验对已有的视觉感知模型进行了修正,提出了将空间积分的影响加入到视觉感知模型中的改进方法.本文还利用该模型对一些显示屏上运动图像的视觉感知过程进行了模拟,结果表明,采用本文提出的模型获得的运动图像的视觉感知效果图更加接近人眼实际所观测到的图像.本文提出的视觉感知模型以及相关的软件模拟结果为进一步优化显示器件的驱动方法提供了评估手段.     

视知觉在建筑造型中的应用

建筑属于视觉感知的艺术,从本质上讲是建筑对象内在关系及其和谐程度的表现形式。本文拟就景观建筑造型、视觉信息传达与人的心理效应间的深层联系进行一些初浅的探索。     

整体拓扑性质的视知觉与计算

提出了一个早期视觉的可能的计算模型，把几何特征分为局部特征与全局特征，认为早期视觉中感知局部几何性质和全局拓扑性质先天运动感知，先于形状感知。模型本质上虽然仍然是读物上，但已不是的传统的ｖｏｎ Ｎｅｕｍａｎｎ的顺序计算，而是非ｖｏｎ Ｎｅｕｍａｎｎ的平行计算，它为计算理论和拓扑性质检测问题之间的矛盾提供了一个可能的解决方法。     

Preserved figure-ground segregation and symmetry perception in visual neglect.

A central controversy in current research on visual attention is whether figures are segregated from their background preattentively, or whether attention is first directed to unstructured regions of the image. Here we present neurological evidence for the former view from studies of a brain-injured patient with visual neglect. His attentional impairment arises after normal segmentation of the image into figures and background has taken place. Our results indicate that information which is neglected and unavailable to higher levels of visual processing can nevertheless be processed by earlier stages in the visual system concerned with segmentation.     

A computational theory for the perception of coherent visual motion

When we see motion, our perception of how one image feature moves depends on the behaviour of other features nearby. In particular, the Gestaltists proposed the law of shared common fate, in which features tend to be perceived as moving together, that is, coherently. Recent psychophysical findings, such as the cooperativity of the motion system and motion capture, support this law. Computationally, coherence is a sensible assumption, because if two features are close then they probably belong to the same object and thus tend to move together. Moreover, the measurement of local motion may be inaccurate and so the integration of motion information over large areas may help to improve the performance. Present theories of visual motion, however, do not account fully for these coherent motion percepts. We propose here a theory that does account for these phenomena and also provides a solution to the aperture problem, where the local information in the image flow is insufficient to specify the motion uniquely.     

超复数变换域的视感知内容数字水印算法

针对彩色图像内容保护问题,提出一种具有视觉感知属性的超复数频域图像水印嵌入算法.该算法首先用傅氏谱残差方法,在HSI颜色空间提取多分辨率彩色载体图像的归一化显著性区域,再对版权水印混沌置乱加密后,将其嵌入至显著性区域所在的超复数颜色矢量中频段系数中,最终实现对彩色图像显著性内容的盲水印保护.实验表明,该方法能够有效抵抗...     

一种基于小波变换的模糊视觉感知水印算法

为了进一步提高目前小波数字水印算法的抗干扰能力,本文提出了一种改进后的小波变换视觉感知模型,设计了一种基于高斯函数的方差和均值的模糊推理规则并将其引入到小波视觉感知模型中,通过上述方法改善了小波视觉感知模型数字水印的抗干扰性能,特别是明显改善了抗压缩攻击的性能。实验结果证明：该算法可进一步提高小波视觉感知数字水印的抗干扰性能,改善其鲁棒性。     

基于生态学专业的研究性实验“公众参与调查”设计及教学实践

以研究性实验＂公众参与调查＂教学设计为例,探索了将理论方法转化为具体实验教学方法的途径,介绍了将该实验方法应用于具体的教学实践过程,阐释了实验教学各环节和具体过程,尤其是将问卷调查法融入具体教学,列举了部分实验结果,总结了教学过程反馈的若干问题。     

Insect motion detectors matched to visual ecology

To detect motion, primates, birds and insects all use local detectors to correlate signals sampled at one location in the image with those sampled after a delay at adjacent locations. These detectors can adapt to high image velocities by shortening the delay. To investigate whether they use long delays for detecting low velocities, we compared motion-sensitive neurons in ten species of fast-flying insects, some of which encounter low velocities while hovering. Neurons of bee-flies and hawkmoths, which hover, are tuned to lower temporal frequencies than those of butterflies and bumblebees, which do not. Tuning to low frequencies indicates longer delays and extends sensitivity to lower velocities. Hoverflies retain fast temporal tuning but use their high spatial acuity for sensing low-velocity motion. Thus an unexpectedly wide range of spatio-temporal tuning matches motion detection to visual ecology.     

Parallel colour-opponent pathways to primary visual cortex

The trichromatic primate retina parses the colour content of a visual scene into 'red/green' and 'blue/yellow' representations. Cortical circuits must combine the information encoded in these colour-opponent signals to reconstruct the full range of perceived colours. Red/green and blue/yellow inputs are relayed by the lateral geniculate nucleus (LGN) of thalamus to primary visual cortex (V1), so understanding how cortical circuits transform these signals requires understanding how LGN inputs to V1 are organized. Here we report direct recordings from LGN afferent axons in muscimol-inactivated V1. We found that blue/yellow afferents terminated exclusively in superficial cortical layers 3B and 4A, whereas red/green afferents were encountered only in deeper cortex, in lower layer 4C. We also describe a distinct cortical target for 'blue-OFF' cells, whose afferents terminated in layer 4A and seemed patchy in organization. The more common 'blue-ON' afferents were found in 4A as well as lower layer 2/3. Chromatic information is thus conveyed to V1 by parallel, anatomically segregated colour-opponent systems, to be combined at a later stage of the colour circuit.     

视觉文化对当代美术教育的启示

从视觉文化角度出发,分析视觉文化在今天的地位和作用和对美术教育的影响.立足于美术教育的特性,将美术教育置放在新的社会语境下,关注社会需求,探索符合中国实情的美术教育手段,提高教学质量,为社会培养输送高素质的创意人才.     

大气流作用下鼻腔振动发声特性

人体内包含有许多大小形态各异的软管系统,这些软管系统在大气流作用下,会产生各种各样的声信号。Fant,F1angann等人研究了语音信号产生的声学模型,阐明了来自于肺内的气流作用于声门、声道,产生语音信号的过程。Grotberg等人研究了肺中气道在气流作用下,哮喘音(wheezes)产生的声学模型,描述了哮喘音产生与气流流率之间的关系。这两类声信号主要源于管道与管内气流的相互作用。中国导引吐纳功在呼     

提高小提琴音质途径探析

分析了小提琴琴体部分声学功能及琴体受力状况,提出小提琴的面板要在适当的弦马压力下,才能产生良好的振动,发出优美的声音.为了能调节弦马对面板压力的大小,设计制作了＂小提琴尾枕微调器＂.可在一定限度内调节弦马对面板的压力,提高小提琴的音质.     

机器人听觉定位跟踪声源的研究与进展

从基于麦克风阵列和基于人耳听觉机理两个方面综述了当前机器人听觉定位跟踪声源目标的研究动态和发展方向.首先回顾了机器人听觉定位声源的研究历史;其次讨论了两种系统的优缺点;最后指出了未来机器人听觉定位跟踪声源的发展趋势.基于麦克风阵列的声源定位系统,盲波束形成技术是未来进一步研究内容.而基于人耳听觉机理的声源定位系统,运用计算听觉场景分析建立声源定位模型将是未来热点研究内容.