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视知觉学习的文1.1视知觉学习的文1.156、空间位置等）以及复杂刺激（879（izan行为短暂变化。知觉学习不同于其他类型学习：不同于陈述性记忆的学习（declarativelearning）需要一个中间的巩固储存器（如海马11,12（specificity皮层如V1和V2。而认知学习、策略选择、程序性学习一般被认为是一种高级的（generalization程缓慢，一般需较长时间的训练；（4）RamachandranBraddick13，他们训45RamachandranBraddick13，他们训45º倾斜线条组成的立体图形，经过一段时间的练习，被试的操作能力得以大大提高，但如果立体图形的倾斜线条变为135º，被试的能力回到训Piggio等人在游标（vernier）任务上也发现类似的结果14，他们要求被试判断呈90º，要求判断右边的线4-9,13-20，1Sowden17图1：朝向和位置特异性学习的刺激和结果示..表1：知觉学习具有朝向特异性的研训练和变朝向差迁移果学习任表1：知觉学习具有朝向特异性的研训练和变朝向差迁移果学习任出注立体Ramachandran&Braddick,Fiorentini&Berardi,1980Poggioetal.,1992Cristetal.,1997Fahle,1993Fahle,Schoupsetal.,无45º和135º不能迁无0º和90º不能互相迁游标辨光栅朝向0º和90º不能互相迁无大于45度很少迁Karni&Sagi,无质地检texture视觉搜对比度检Ahissar&Hochstein,1996,Sigman&Gilbert,2000Sowdenetal.,全图4,5,8,9,15,17,18,21-2930,31表2：知觉学习具有位置特异性的研究汇总，引学习任出注立体Ramachandran,无/没有测量表2：知觉学习具有位置特异性的研究汇总，引学习任出注立体Ramachandran,无/没有测量Cristetal.,1997Ahissar&Hochstein,无/立体pop-out无/经过训练的被试有Fahle,1994;Fahle,Edelman&Poggio,1995Beard,Levi,&Reich,Karni&Sagi,游标辨无质地检texture图形辨部无Nazir&O’Regan,1990;Dill&Fahle,1997Sowdenetal.,无亮度对比度检无线段朝向Shui&Pashler,无光栅朝向Schoupsetal.,无/Juttner&Rentschler,Rentschleretal.,Ball&Sekuler,Gaborpatch部中线相似位置可以迁运动方向部中线相似位置可以迁空间相位Berardi&Fiorentini,无/27实验让被试遮盖一眼用单眼4-6,26,33,34单细胞记录研究发现初级视觉皮层细胞的感受野在视野中只有大约单细胞记录研究发现初级视觉皮层细胞的感受野在视野中只有大约1º的直径，V2V4细胞感受野的直径会有几度，而前下颞叶（anteriorinferotemporal，AIT）20º36。因此这种对刺激朝向、位置的特2.2比较容易（SOA较长或目标元素与背景元素的朝向差别较大图图2：训练任务的难度与特异性的....或除中央注视点外的任意位置。目标元素和背景元素的朝向差别决定了任务难度。d..-30º）能够迁移到邻近位置（0.7º或2.1º），而右图对困难任务（2pos-16º）表现出很强的置特异性8AhissarHochstein的结果，Jeter等人指出确切地说应该是“迁移任务的难度（而非训练任务的难度）决定了知觉学习的特异性”37。他们训练刺激（-35º或55º）的朝向偏差区分，分困难和容易任务（偏差分别为±5º和±12º，图3a。训练阶段刺激始终呈现在以注视点为中心的某对角线上，测试阶段刺激的位置换到另一对角线了，同时朝向也改变了（3b。结果发现不管训练容易或困难任务，均能迁移到简单任务上（图3c，而迁移不到困难任务上（图图3：迁移任务的难图3：迁移任务的难度与特异性的a.实验刺激。困难和容易任务的测试刺激与被试内在的参照刺激（-35º55º）声（上图）和高噪声（下图）条件下的结果一致；d.不管训练任务容易还是困难，学习Liu和Weinshall发现即使是先前发现存在特异性的学习中，其实也具有迁38。他们让被试进行随机点运动方向辨别的学习，任务分容易和困难的（运外，容易任务的学习能普遍迁移到其他运动方向的容易任务上，这与Ahissar和Jeter等人的结果一致8,37。研究同时发现在某一方向充分训练容易任务，再在另一（insight3.3.1早期阶段：早期选择理论和回馈网络模型（Recurrent20,3.3.1早期阶段：早期选择理论和回馈网络模型（Recurrent20,39theoryHebbian突触学习的计算模型中，AdiniTsodyks提出一个对比度辨别学习的回馈网络模型（RecurrentModel）41。他们的实验发现中央刺激的对比度辨别只在周边有线索刺激的条件下才能发生（Yu3，423.2中层阶段：通道重新赋权模型（Rewighting习的机制16,43-45，信号增强可以表现为神经元数目增加、反应增益增强4443,45,46DosherLu的工作，提出了知觉学习模板模型（PTMModel）4247，认为知觉学习可能存在三种不同机制：（1）信号增强（内部噪音减少导致在零或低噪声下的阈限降低（图4b（2）外部噪声去除（模板匹配能力增强导致高外部噪声的阈限降低（图4c（3）乘法噪声降低（增益控制增加有外部噪声条件下都能观察到阈限降低（4d。他们的实验验证了前两种，基于此结果提出“通道重新赋Model生在早期视觉表征区域（V生在早期视觉表征区域（V1），如果基本的视觉通道发生改变，那么学习V1图4：知觉模板模型和知觉学习三种机制的a.知觉模板模型；b-d.学习前后对比度检测阈值与添加噪音强度关系的变化。..低（增益控制增强），在所有外部噪声条件下都能观察到阈限降低图5：“通道重新赋权模图5：“通道重新赋权模型”（RewightingModel）示意3.3高级到低级：反转层次理论（Reverse-hierarchytheoryAhissar和Hochstein根据实验数据（图2）（Reverse-hierarchytheory,RHT3.4高级阶段：Mollon&Danilova样描述的：“Indirectly,viathecentralsignalstowhichhehasaccessthesubjectbelearningaboutopticalfeaturesofhisretinalimage;belearningaboutopticalfeaturesofhisretinalimage;aboutthelocaltopographyofhisreceptormosaic;andaboutthespecificwiringofindividualneuronswithinhisvisual50,4.控（如“顿（insight）觉学习中起重要作用52,53。注意可能不仅仅起到调控作用，它可能就是知觉学习的机制。Goldstone提出知觉学习的机制之一就是注意权重的改变54，它可以通过增加分配在重要的知觉维度和特征上的注意和55Karni和Sagi提出56，知觉学习可分为“快速学习”（fastlearning）和“慢速学 图7：质地检测任务（Texture图7：质地检测任务（Texturediscriminationtask）学习.变短。c.快速学习在最初一天内的几组训练中就表现出来，而慢速学习则持续知觉学习中反馈起到什么作用？ShuiPashler3之间也不会互相迁移61，表明高级视觉信息加工以及自上而各自的学习（disruption。Seitz2005年报道了一种特异于任务对知觉学习4.1.4多刺激学习—— 63。随后我们提出了知觉学习的“刺激4.2知觉学习不需要注意的参与也能发生。Watanabe55,4.2知觉学习不需要注意的参与也能发生。Watanabe55,65报告了一种“任learninglearning8b能力的提高66图8：无注意条件下的..5.（15.1675.1.1SchoupsOrban等人训练猴子进行光栅朝向辨别68，行为学结果显示朝向学习存在位置和朝向特异性（9a图9：光栅朝向辨别行为和神经元图9：光栅朝向辨别行为和神经元.位置（绿色），被动呈现刺激的位置（红色，passive）。行为学结果表明学习存在置和朝向特异性。b.来自V1的第2～3层，5～6层数据的汇总68V1V2感小但是结果还是显著的。他们没有从生理学水平（至少在V1或V2）发现神经并不一4,28,68。可能的原因有：（1）尽管使用相似的实验参数，如训练朝向、网膜位置，Ghose3～8º，而Schoups文章训练后的值仅有0.6～1.2º，有没有可能是因为其中包含了策略性的学learninggaborYangMausellGhose70YangMausellGhose70RaiguelOrban7169。相反地，Yang等人265.1.2Crist，LiGibert的工作也发现训练并没有改变初级视觉皮层的感受野特性（如位置、大小、朝向选择性皮层放大系数60。有趣的是，他effect训练任务（两分任务）V1神经元的背景调节（contextualeffect）图10：训练两分任务（图10：训练两分任务（bisection）改变背景调节（contextual（11上V1神经元的活动。结果发现即使刺激相似，但执行任务不同，V1神经元的反应特性也可以被特异地动态改变（图图11：任务调控神经元反图11：任务调控神经元反..5.1.374最近，LawGold75，研究者训练猴子进行视觉运动MTIPS区的神经元活动，MT主要表征解决任务的74最近，LawGold75，研究者训练猴子进行视觉运动MTIPS区的神经元活动，MT主要表征解决任务的LIPMT信号改变的（invariance）的机制，感受野对物体位置也具有选择性，物体不变性并非与生俱来的，经过训练的8082（168,69，即V455.2ERP的研究报道了知觉学习引起早5.2ERP的研究报道了知觉学习引起早期成分的变87-90，SkrandiesERP幅值增大，潜伏期减少，这些变化主要发生91。DingSong92，行为学表现出朝向特异性，脑电数据在顶区的N1（140ms左右）波幅表现出朝向迁移P2（200ms左右）波幅上表现出朝向特异性。虽然特异性学习5.310年知觉学习的脑成像研究随着技术手段的成熟而发展起来，目前的研imaging，fMRI颅磁刺激TMS（TranscranialmagneticstimulationTMSPE（Positronemission5.2.1Schiltz1999PET技术比较被试进行朝向分辨训练前后的血流水外的区域，如右距状沟（rightcalcarinesulcus，左舌回（leftlingualgyrus，左中枕（leftmiddleociitlgyrusSchwartz2002fMRI2794结果发现在早期视觉皮层等网膜拓扑区域（如V1、V2），训练眼相较于非训练Furmanski2004fMRIV195BOLDFurmanski2004fMRIV195BOLD信号的变化。训斜朝向诱发的信号增强了V1（2fMRNeary2005TMS96。Mukai2007fMRI工作提出根据大脑视觉和注意相关区域的活动Brodman18、19区）FG（fusiformgyrus）及一些跟注sulcusFE（frontalIPSFEF图12：“学习组”和“无学习图12：“学习组”和“无学习组”数.（ROI.93。针对这一矛盾的结果，Yotsumoto93。针对这一矛盾的结果，Yotsumoto水平（13A，post3pre相比图13：训练位置引起脑区活动变化指.sulcusSP（superiorgyrusMF（middlegyrus5.3.2传统观点认为，复杂图形的表征在相对高级的大脑区域完成。Sigman2005年的工作表明视觉学习可能会导致人们对复杂物体的表征从高级皮层区域5.3.2传统观点认为，复杂图形的表征在相对高级的大脑区域完成。Sigman2005年的工作表明视觉学习可能会导致人们对复杂物体的表征从高级皮层区域 著性图形（low-salienceshapes）的学习从V1到高级视觉区域信号都增强了，学习通过调节LOC的联系以编码主要特征。异，发现训练提高了对错觉轮廓的反应。行为学结果表明学习效果可以保持10deBeeck105107？对一些知觉任务来说，学习在一些107？对一些知觉任务来说，学习在一些相关感觉皮层就能发生6.（mbla108-114。例Ploat2004年的研究报道108，研究者通过训练成人弱视进行对比度检测任务（刺激见14a左下角，训练提高了对比度检测能力，使得对比度敏感函数曲线大大提高14b（crowding）也大大减小，这一结果提示弱视知觉学习可以从简单的对比度110。但关于弱视知觉学习的机制目前尚不清楚，LiLevi112,115图14：成人弱视训练a．训练对比图14：成人弱视训练a．训练对比度检测任务（左下角示意图。训练前后比较对比度敏感函数曲线7.差异等原因所导致的。例如，Fine和Jacobs比较了从朝向辨别到图形识别的一系列心理物理学的研究116，将训练效果均转换成d'进行比较，发现综述参Merzenich,M.M.&Sameshima,K.Corticalplasticityandmemory.综述参Merzenich,M.M.&Sameshima,K.Corticalplasticityandmemory.CurrOpin3,187-96Gibson,E.J.Perceptuallearning.AnnuRevPsychol14,29-56Yu,C.,Klein,S.A.&Levi,D.M.Perceptuallearningincontrastdiscriminationandthe(minimal)roleofcontext.JVis4,169-82(2004).Schoups,A.A.,Vogels,R.&Orban,G.A.Humanperceptuallearninginidentifyingtheobliqueorientation:retinotopy,orientationspecificityandmonocularity.JPhysiol483(Pt3),797-810(1995).27,953-65Fiorentini,A.&Berardi,N.Perceptuallearningspecificfororientationandspatialfrequency.Nature287,43-44(1980).McKee,S.P.&Westheimer,G.Improvementinvernieracuitywithpractice.PerceptPsychophys24,258-62(1978).Ahissar,M.&Hochstein,S.TaskdifficultyandthespecificityofperceptualNature387,401-6Sigman,M.&Gilbert,C.D.Learningtofindashape.NatNeurosci3,264-9(2000).Bruce,V.,Burton,A.M.inPerceptualLearning(eds.Fahle,M.&Poggio,T.)ix-xx(MITPress,Cambridge,MA,USA,2002).Fahle,M.inPerceptualLearning(eds.Fahle,M.&Poggio,T.)ix-xx(MITPress,Cambridge,MA,USA,2002).Fahle,M.Perceptuallearning:specificityversusgeneralization.CurrOpinNeurobiol15,154-60(2005).Ramachandran,V.S.&Braddick,O.Orientation-specificlearninginstereopsis.2,371-6Poggio,T.,Fahle,M.&Edelman,S.Fastperceptuallearninginvisualhyperacuity.256,1018-21Ahissar,M.&Hochstein,S.Learningpop-outdetection:specificitiestostimuluscharacteristics.VisionRes36,3487-500(1996).Folta,K.NeuralfinetuningduringVernieracuitytraining?VisionRes43,1177-85(2003).Sowden,P.T.,Rose,D.&Davies,I.R.Perceptuallearningofluminancecontrastdetection:specificforspatialfrequencyandretinallocationbutnotorientation.VisionResearch42,1249-58(2002).Crist,R.E.,Kapadia,M.K.,Westheimer,G.&Gilbert,C.D.Perceptuallearningofspatiallocalization:specificityfororientation,position,andcontext.JNeurophysiol78,2889-94Ball,K.&Sekuler,R.Aspecificandenduringimprovementinvisualmotiondiscrimination.Science218,697-8(1982).Fahle,M.Visuallearninginthehyperacuityrangeinadults.GerJOphthalmol2,83-6Ramachandran,V.S.Learning-likephenomenainstereopsis.Nature262,382-4O'Toole,A.J.&Kersten,D.J.Learningtoseerandom-dotstereograms.Perception21,43Westheimer,G.&Truong,T.T.Targetcrowdinginfovealandperipheral43Westheimer,G.&Truong,T.T.Targetcrowdinginfovealandperipheralstereoacuity.AmJOptomPhysiolOpt65,395-9(1988).Fahle,M.Humanpatternrecognition:parallelprocessingandperceptualFahle,M.,Edelman,S.&Poggio,T.Fastperceptuallearninginhyperacuity.VisionRes35,3003-13(1995).Beard,B.L.,Levi,D.M.&Reich,L.N.Perceptuallearninginparafovealvision.Vision35,1679-90Karni,A.&Sagi,D.Wherepracticemakesperfectintexturediscrimination:evidenceforprimaryvisualcortexplasticity.ProcNatlAcadSciUSA88,4966-70.(1991).Shiu,L.P.&Pashler,H.Improvementinlineorientationdiscriminationisretinallylocalbutdependentoncognitiveset.PerceptPsychophys52,582-8(1992).Berardi,N.&Fiorentini,A.Interhemispherictransferofvisualinformationinhumans:spatialcharacteristics.JPhysiol384,633-47(1987).Nazir,T.A.&O'Regan,J.K.Someresultsontranslationinvarianceinthehumanvisualsystem.SpatVis5,81-100(1990).Dill,M.&Fahle,M.Theroleofvisualfieldpositioninpattern-discriminationProcBiolSci264,1031-6Dill,M.inPerceptualLearning(eds.Fahle,M.&Poggio,T.)219-231(MITPress,Cambridge,MA,USA,2002).Fiorentini,A.&Berardi,N.Learningingratingwaveformdiscrimination:specificityfororientationandspatialfrequency.VisionRes21,1149-58(1981).Schoups,A.A.&Orban,G.A.Interoculartransferinperceptuallearningofapop-outdiscriminationtask.ProcNatlAcadSciUSA93,7358-62(1996).Hubel,D.H.&Wiesel,T.N.Receptivefieldsofsingleneuronesinthecat'sstriatecortex.JPhysiol148,574-91(1959).ofmonkeys.CurrBiol5,552-63(1995).Jeter,P.E.,Dosher,B.A.,Petrov,A.&Lu,Z.-L.Taskprecisionattransferdeterminesspecificityofperceptuallearning.JournalofVision9,1-13(2009).Liu,Z.&Weinshall,D.Mechanismsofgeneralizationinperceptuallearning.Vision40,97-109Fahle,M.Perceptuallearning:acaseforearlyselection.JVis4,879-90Paz,R.,Wise,S.P.&Vaadia,E.Viewinganddoing:similarcorticalmechanismsforperceptualandmotorlearning.TrendsNeurosci27,496-503(2004).Adini,Y.,Sagi,D.&Tsodyks,M.Context-enabledlearninginthehumanvisualNature415,790-793Dosher,B.A.&Lu,Z.L.Perceptuallearningreflectsexternalnoisefilteringandinternalnoisereductionthroughchannelreweighting.ProcNatlAcadSciUSA95,13988-93Saarinen,J.&Levi,D.M.PerceptualLearninginVernierAcuity:WhatisLearned?VisionResearch35,519-527(1995).Nature402,176-8Li,R.W.,Levi,D.M.&Klein,S.A.PerceptualNature402,176-8Li,R.W.,Levi,D.M.&Klein,S.A.Perceptuallearningimprovesefficiencybyre-tuningthedecision'template'forpositiondiscrimination.NatNeurosci7,178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