基于极限学习机(ELM)的视线落点估计方法

基于极限学习机(ELM)所具有的训练速度快、适合多分类的特点,提出一种新的单摄像机视线追踪系统视线落点估计方法.在初始标定阶段,将多视线参数作为ELM输入,将视线在屏幕上的落点区域作为输出,将非线性多项式作为激活函数,通过初始标定获取ELM训练数据,建立视线特征参数和视线屏幕落点之间的映射模型.实验结果表明,通过对不同角度分布的视线落点进行估计和改变隐层单元数量进行训练,基于ELM的视线落点估计方法无论视线落点精度还是稳定性均优于传统的非线性多项式拟合方法.     

The role of disparity-sensitive cortical neurons in signalling the direction of self-motion

Movement of an observer through the environment generates motion on the retina. This optic flow provides information about the direction of self-motion, but only if it contains differential motion of elements at different depths. If the observer tracks a stationary object while moving in a direction different from his line of sight, the images of objects in the foreground and in the background move in opposite directions. We have found neurons in the cerebral cortex of monkeys that prefer one direction of motion when the disparity of a stimulus corresponds to foreground motion and prefer the opposite direction when the disparity corresponds to background motion. We propose that these neurons contribute a signal about the direction of self-motion.     

Topography and synaptic shaping of direction selectivity in primary auditory cortex

The direction of frequency-modulated (FM) sweeps is an important temporal cue in animal and human communication. FM direction-selective neurons are found in the primary auditory cortex (A1), but their topography and the mechanisms underlying their selectivity remain largely unknown. Here we report that in the rat A1, direction selectivity is topographically ordered in parallel with characteristic frequency (CF): low CF neurons preferred upward sweeps, whereas high CF neurons preferred downward sweeps. The asymmetry of 'inhibitory sidebands', suppressive regions flanking the tonal receptive field (TRF) of the spike response, also co-varied with CF. In vivo whole-cell recordings showed that the direction selectivity already present in the synaptic inputs was enhanced by cortical synaptic inhibition, which suppressed the synaptic excitation of the non-preferred direction more than that of the preferred. The excitatory and inhibitory synaptic TRFs had identical spectral tuning, but with inhibition delayed relative to excitation. The spectral asymmetry of the synaptic TRFs co-varied with CF, as had direction selectivity and sideband asymmetry, and thus suggested a synaptic mechanism for the shaping of FM direction selectivity and its topographic ordering.     

Moving visual stimuli rapidly induce direction sensitivity of developing tectal neurons

During development of the visual system, the pattern of visual inputs may have an instructive role in refining developing neural circuits. How visual inputs of specific spatiotemporal patterns shape the circuit development remains largely unknown. We report here that, in the developing Xenopus retinotectal system, the receptive field of tectal neurons can be 'trained' to become direction-sensitive within minutes after repetitive exposure of the retina to moving bars in a particular direction. The induction of direction-sensitivity depends on the speed of the moving bar, can not be induced by random visual stimuli, and is accompanied by an asymmetric modification of the tectal neuron's receptive field. Furthermore, such training-induced changes require spiking of the tectal neuron and activation of a NMDA (N-methyl-D-aspartate) subtype of glutamate receptors during training, and are attributable to an activity-induced enhancement of glutamate-mediated inputs. Thus, developing neural circuits can be modified rapidly and specifically by visual inputs of defined spatiotemporal patterns, in a manner consistent with predictions based on spike-time-dependent synaptic modification.     

Peripheral modulation of mechano-sensitivity in primary afferent neurons

Considerable attention has centered recently on the changes in neuron excitability and synaptic efficacy caused by certain biogenic amines and neuropeptides. These neuromodulators act at a wide variety of both central and peripheral targets, and bring about diverse biological results. In sensory pathways, modulation occurs at central input synapses of the primary afferents and at peripheral terminals of efferents. This study was undertaken to look at non-synaptic modulation of membrane potentials in peripheral sensory endings of identifiable receptors. Using intracellular recording from the three primary afferent fibres of a recently described simple crustacean stretch receptor, which lacks centrifugal control, we observed in vitro modulation of the sensory response by three neuroactive substances known to be present in vivo. Two neuroamines, serotonin and octopamine, depressed receptor potentials and impulse discharge whereas the pentapeptide proctolin enhanced both these components of the sensory response. The peripheral sensory modulation reported here for a lobster mechano-receptor may occur in many animal groups and sensory systems.     

Activation of a C. elegans Antennapedia homologue in migrating cells controls their direction of migration.

Anterior-posterior patterning in insects, vertebrates and nematodes involves members of conserved Antennapedia-class homeobox gene clusters (HOM-C) that are thought to give specific body regions their identities. The effects of these genes on region-specific body structures have been described extensively, particularly in Drosophila, but little is known about how HOM-C genes affect the behaviours of cells that migrate into their domains of function. In Caenorhabditis elegans, the Antennapedia-like HOM-C gene mab-5 not only specifies postembryonic fates of cells in a posterior body region, but also influences the migration of mesodermal and neural cells that move through this region. Here we show that as one neuroblast migrates into this posterior region, it switches on mab-5 gene expression; mab-5 then acts as a developmental switch to control the migratory behaviour of the neuroblast descendants. HOM-C genes can therefore not only direct region-specific patterns of cell division and differentiation, but can also act within migrating cells to programme region-specific migratory behaviour.     

Glycine potentiates the NMDA response in cultured mouse brain neurons

Transmitters mediating 'fast' synaptic processes in the vertebrate central nervous system are commonly placed in two separate categories that are believed to exhibit no interaction at the receptor level. The 'inhibitory transmitters' (such as glycine and GABA) are considered to act only on receptors mediating a chloride conductance increase, whereas 'excitatory transmitters' (such as L-glutamate) are considered to activate receptors mediating a cationic conductance increase. The best known excitatory receptor is that specifically activated by N-methyl-D-aspartate (NMDA) which has recently been characterized at the single channel level. The response activated by NMDA agonists is unique in that it exhibits a voltage-dependent Mg block. We report here that this response exhibits another remarkable property: it is dramatically potentiated by glycine. This potentiation is not mediated by the inhibitory strychnine-sensitive glycine receptor, and is detected at a glycine concentration as low as 10 nM. The potentiation can be observed in outside-out patches as an increase in the frequency of opening of the channels activated by NMDA agonists. Thus, in addition to its role as an inhibitory transmitter, glycine may facilitate excitatory transmission in the brain through an allosteric activation of the NMDA receptor.     

CRMPs对神经元突起生长的调控

神经元突起是建立神经网络的物质基础,其生长为生长信号启动胞内信号促使神经元不断极化的过程.作为Rho GTPases的下游信号,CRMPs富集于神经系统,参与神经元的发育过程,可作为不同信号通路的共同受体后分子,通过改变细胞骨架的运动调控突起生长.其不同亚基的功能分化、不同亲和性特点显示其具有突起生长调控的分子开关特征...     

Inhibition of neurite polarity by tau antisense oligonucleotides in primary cerebellar neurons

Neurons in culture can have fundamentally distinct morphologies which permit their cytological identification and the recognition of their neurites as axons or dendrites. Microtubules may have a role in determining morphology by the selective stabilization of spatially distinct microtubule subsets. The plasticity of a neurite correlates inversely with the stability of its component microtubules: microtubules in growth cones are very dynamic, and in initial neurites there is continuous incorporation of labelled subunits, whereas in mature neurites, microtubules are highly stabilized. The binding of microtubule-associated proteins to the microtubules very probably contributes to this stability. Cerebellar neurons in dissociated culture initially extend exploratory neurites and, after a relatively constant interval, become polarized. Polarity becomes evident when a single neurite exceeds the others in length. These stable neurites cease to undergo the retractions and extensions characteristic of initial neurites and assume many features of axons and dendrites. We have now studied the role of the neuronal microtubule-associate protein tau in neurite polarization by selectively inhibiting tau expression by the addition of antisense oligonucleotides to the culture media. Although the extension of initial exploratory neurites occurred normally, neurite asymmetry was inhibited by the failure to elaborate an axon.     

The p66shc adaptor protein controls oxidative stress response and life span in mammals

Gene mutations in invertebrates have been identified that extend life span and enhance resistance to environmental stresses such as ultraviolet light or reactive oxygen species. In mammals, the mechanisms that regulate stress response are poorly understood and no genes are known to increase individual life span. Here we report that targeted mutation of the mouse p66shc gene induces stress resistance and prolongs life span. p66shc is a splice variant of p52shc/p46shc (ref. 2), a cytoplasmic signal transducer involved in the transmission of mitogenic signals from activated receptors to Ras. We show that: (1) p66shc is serine phosphorylated upon treatment with hydrogen peroxide (H2O2) or irradiation with ultraviolet light; (2) ablation of p66shc enhances cellular resistance to apoptosis induced by H2O2 or ultraviolet light; (3) a serine-phosphorylation defective mutant of p66shc cannot restore the normal stress response in p66shc-/- cells; (4) the p53 and p21 stress response is impaired in p66shc-/- cells; (5) p66shc-/- mice have increased resistance to paraquat and a 30% increase in life span. We propose that p66shc is part of a signal transduction pathway that regulates stress apoptotic responses and life span in mammals.     

大鼠海马神经元neurobasal无血清的原代培养方法

目的:建立纯度和活力较高的无血清原代培养海马神经元的方法。方法:新生SD大鼠海马,用neuro-basal培养基培养,免疫荧光鉴定神经元纯度,MTT法检测其活力。结果:神经元接种12~24 h后贴壁,并长出细小突起,3 d具有典型神经元形态特征,4 d突起形成稀疏的神经纤维网络,8 d后神经元5~10个聚集成团,突起密集,生长稳定,12 d后出现细胞碎片。Tubulin荧光染色显示清晰的神经元,突起绵长且相互交织,占细胞总数的66.7%;GFAP荧光染色的细胞数量少,突起短粗,占33.7%。培养1~5 d MTT代谢率逐渐上升,6~11 d处于平台期,11 d后下降。结论:neurobasal无血清培养获得的神经元纯度大于60%,6~11 d的细胞适于细胞学实验。     

视线追踪系统中基于黎曼几何的落点补偿方法研究

针对非接触式视线跟踪系统中注视点估计算法鲁棒性差的问题,对单相机双光源的视线追踪系统进行了改进.在空间相似三角形注视点估计算法的基础上,提出一种基于黎曼几何的视线落点补偿方法.在眼球模型结构的基础上分析了眼球角膜曲面对视线落点偏差的影响.根据人类眼球生理特点,在黎曼几何中对眼球曲面结构进行建模,提出以最短测地线长度为边长构造平面三角形,以补偿欧式几何中直线距离造成的视线落点的误差.利用非线性多项式模型对眼球视轴和光轴之间的偏差进行拟合,得到最终的视线落点.实验证明,该方法在水平和垂直方向上最大误差均小于1 cm,对视线落点补偿具有显著效果.     

The Translatology Process of the Word ‘Gaze’ in Chinese Context

With reference to the concept of ‘cultural studies’ and certain modern theories in translation studies,this essay makes a general analysis of the translation and introduction of the ‘gaze’ concept in China.On the basis of this analysis,it explores how this concept spread to China and why,this concept was explained and rewritten through translation and interpretation in the course of the spread;and what responses and reflections we should bear during the process.     

Optical gain in silicon nanocrystals

Adding optical functionality to a silicon microelectronic chip is one of the most challenging problems of materials research. Silicon is an indirect-bandgap semiconductor and so is an inefficient emitter of light. For this reason, integration of optically functional elements with silicon microelectronic circuitry has largely been achieved through the use of direct-bandgap compound semiconductors. For optoelectronic applications, the key device is the light source--a laser. Compound semiconductor lasers exploit low-dimensional electronic systems, such as quantum wells and quantum dots, as the active optical amplifying medium. Here we demonstrate that light amplification is possible using silicon itself, in the form of quantum dots dispersed in a silicon dioxide matrix. Net optical gain is seen in both waveguide and transmission configurations, with the material gain being of the same order as that of direct-bandgap quantum dots. We explain the observations using a model based on population inversion of radiative states associated with the Si/SiO2 interface. These findings open a route to the fabrication of a silicon laser.