国外最新研究动态：视觉觉知的神经机制

Pessoa L, Ungerleider L G. Neural Correlates ofChange Detection and Change Blindness in aWorking Memory Task. Cerebral Cortex, 2004,14:511-520     

视觉意识及其神经机制

视觉意识的神经机制是当前认知神经科学研究的热点问题之一。过去普遍认为视觉信息加工主要有两条通路:腹侧通路和背侧通路;而新近的研究表明还存在不经过初级视觉皮层(V1区)的第三条通路。高级视觉皮层、V1区和皮层下结构都对意识觉知的产生起到了相应的作用。已有的实验证据表明,意识的产生过程异常复杂,仍有很多问题值得继续深入讨论和研究。     

意识、觉知与反思

一、引言在日常的意识体验中,体验总有特定的体验内容。然而,意识不但关指某物,它也与特定的我粘连着。例如,你正在看一本书,你一边阅读一边建构着你读到的文本的意思;但对文本的知觉和对文本意思的理解并没有涵盖你心智中发生的一切。除了这些感知和体验的内容之外,在你的心     

视觉搜索中多目标追踪的研究

在视觉信息的选择加工过程中 ,只有很少信息能够通过注意系统得到进一步的认知加工 ,其中视觉搜索起着十分重要的作用。本研究基于动态视觉信息注意追踪的研究 ,采用 3× 2× 2的实验设计 ,从如下三方面对注意追踪的规律进行了探讨 :(1)分心物数量 (1,5和 9)的变化对多目标注意追踪的影响 ;(2 )目标的显著性 (特征变化和特征不变 )对多目标注意追踪的影响 ;(3)目标运动形式 (目标随机运动和目标运动形式不变 )对多目标注意追踪的影响。研究结果表明 :(1)分心物数量的增加对目标的注意识别没有抑制作用 ;(2 )特征变化目标的注意识别速度显著高于特征不变的目标 ;(3)运动形式不变的目标较运动形式变化目标的注意识别速度快。     

多目标视觉追踪的现象、规律和认知加工机制

传统注意研究多基于单个注意焦点和采用静态视觉信息。由Pylyshyn(1988)提出的多目标追踪范式则基于动态场景,是研究同时追踪多个目标的容量有限的注意机制比较常用的范式。在多目标追踪基础上发展起来的多身份追踪范式中的对象带有身份信息,涉及到较复杂的认知机制,如注意、视觉工作记忆等。探讨以上两种视觉追踪的认知加工机制对真实或模拟情境中动态信息的认知加工活动有重要的理论价值和实践指导意义。     

视觉情绪知觉需要注意和意识吗？困惑及其原因

一些研究者通过操纵刺激知觉条件或者被试注意资源的分配方式来改变意识水平,他们报告视觉情绪刺激可以在没有进入意识的条件下知觉。但最近采用更为客观的方法揭示先前研究中所用的测量意识觉知的标准并不客观有效,这些以信号检测论为基础的研究显示,视觉情绪知觉离不开注意,注意通过自上而下和自下而上两种方式调控情绪知觉,除此之外还发现,个性变量,比如焦虑特质的差异也会影响到情绪知觉     

正念注意觉知量表儿童版~MAAS-C在中国城市及农村儿童中使用的信效度检验

目的:修订中文版正念注意觉知量表儿童版(the Mindful Attention Awareness Scale—Children,MAAS-C),考察其在中国文化背景下的适用性及信效度。方法:城市及农村地区共619名小学4-6年级学生参与研究。对数据进行项目分析、探索性因素分析、验证性因素分析、信度分析、效标关联效度分析、性别及城乡地区等值性检验。结果:中文版MAAS-C为单维结构,具有良好的结构效度、效标效度及信度。测量不变性检验表明,该量表在不同性别儿童间达到严格等值,城乡地区儿童间达到弱等值。结论:正念觉知量表儿童版的中文版本各项心理测量学指标良好,适宜在我国儿童群体中使用。     

多目标视觉追踪中物体属性加工的眼动研究*

采用多目标视觉追踪任务(MOT),探讨物体颜色特征对视觉追踪的影响,同时记录被试的眼动情况,探讨追踪过程中颜色特征对眼动模式的影响。结果发现,视觉追踪机制能够对物体的颜色特征进行加工,但加工程度受制于目标物与分心物之间的特征竞争关系。在物体颜色特征条件下,视觉系统采用知觉组织加工策略,以被追踪目标构成的多边形中心为注意中心。在对物体颜色特征的加工中,内源性注意与外源性注意相互影响。     

目标大小变化对多目标视觉追踪的影响

采用多目标追踪任务（MOT）对追踪过程中被试（16名）的眼动进行记录,探讨目标特征变化对视觉追踪的影响。结果表明：视觉追踪机制能够对物体的特征属性进行编码加工,但加工程度受制于目标物与分心物之间的特征竞争关系;追踪过程中,视觉系统采用知觉组织加工策略,以被追踪目标构成的多边形中心为注意中心;物体大小特征没有引起较多的外源性注意,在物体大小特征的变化条件下,视觉追踪主要是内源性的注意控制加工过程。     

自闭症儿童视觉动态信息的注意加工特点——来自多目标追踪任务的证据

为了考察中低功能自闭症儿童在动态条件下的多目标注意加工特点,研究采用多目标追踪实验范式,具体追踪任务采用多目标随机运动和碰撞反弹算法。实验设计为两因素混合设计,组间变量为年龄和性别匹配的中低功能自闭症和正常儿童组,组内变量为追踪目标数量（分别为1、2、3、4个目标）,因变量为被试在多目标追踪任务中的追踪正确率和追踪容量。结果发现：（1）中低功能自闭症儿童在目标数量为1到目标数量为4时的正确率均明显低于正常儿童,且标准差变异较大,中低功能自闭症儿童的多目标的持续追踪能力和稳定性存在一定的缺陷;（2）当目标数量为1时,正常组儿童与中低功能自闭症儿童的追踪容量差异不显著;目标为2、3、4时,两组追踪容量差异均显著。不同目标数量情况下中低功能自闭症儿童平均的注意容量为0.83~1.24个（平均容量约为1个）明显低于正常儿童的0.95~3.72个（最大容量接近4个）。中低功能自闭症儿童在多目标追踪上表现为单焦点注意加工的特点,存在一定程度的注意转移缺陷。     

不相关言语对视觉觉察的影响

前人多在记忆层面探讨不相关言语效应(the Irrelevant Speech Effect, ISE), 而本文选择在意识觉察(conscious awareness)阶段观察这一现象。所有实验均采用视觉掩蔽及听觉输入不相关声音的视听交互方式。实验1在安静、纯音及不相关言语3种听觉背景下让被试对简单图片做视觉觉察判断, 结果发现不相关言语干扰了视觉觉察, 而纯音则未产生干扰。实验2在相同的3种听觉背景下要求被试对复杂图片做视觉觉察判断, 结果同实验1。实验3采用事件相关电位技术, 在同样的3种听觉背景下观察被试对简单图片做视觉觉察判断时的脑电变化, 结果发现不相关言语干扰了视觉觉察负波的形成, 验证了行为学研究的结果。本文结果表明不相干言语在视觉意识觉察阶段就对被试的行为产生了干扰。     

Balancing awareness: Vestibular signals modulate visual consciousness in the absence of awareness

The processing of visual and vestibular information is crucial for perceiving self-motion. Visual cues, such as optic flow, have been shown to induce and alter vestibular percepts, yet the role of vestibular information in shaping visual awareness remains unclear. Here we investigated if vestibular signals influence the access to awareness of invisible visual signals. Using natural vestibular stimulation (passive yaw rotations) on a vestibular self-motion platform, and optic flow masked through continuous flash suppression (CFS) we tested if congruent visual–vestibular information would break interocular suppression more rapidly than incongruent information. We found that when the unseen optic flow was congruent with the vestibular signals perceptual suppression as quantified with the CFS paradigm was broken more rapidly than when it was incongruent. We argue that vestibular signals impact the formation of visual awareness through enhanced access to awareness for congruent multisensory stimulation.     

Afterimages: a tool for defining the neural correlate of visual consciousness

Our visual system not only mediates information about the visual environment but is capable of generating pictures of nonexistent worlds: afterimages, illusions, phosphenes, etc. We are "aware" of these pictures just as we are aware of the images of natural, physical objects. This raises the question: is the neural correlate of consciousness (NCC) of such images the same as that of images of physical objects? Images of natural objects have some properties in common with afterimages (e.g., stability of verticality) but there are also obvious differences (e.g., images maintain size constancy, whereas afterimages follow Emmert's Law: when seen while screens at different distances are observed, an afterimage looks larger, the greater the distance of the screen). The differences can be explained by differences in the retinal extent of images and afterimages, which favors the view that both have the same NCC. It seems reasonable to assume that before neural activity can produce awareness, all the computations necessary for a veridical representation of, e.g., an object, must be completed within the neural substrate and that information characteristic of a particular object must be available within the NCC. Given these assumptions, it can be shown that no retinotopic (in a strict sense) cortical areas can serve as the NCC, although some type of topographic representation is necessary. It seems also to be unlikely that neurons classified as cardinal cells alone can serve as NCC.     

Different subjective awareness measures demonstrate the influence of visual identification on perceptual awareness ratings

We compare four subjective awareness measures in the context of a visual identification task and investigate quantitative differences in terms of scale use and correlation with task performance. We also analyse the effect of identification task decisions on subsequent subjective reports. Results show that awareness ratings strongly predict accuracy for all scale types, although the type of awareness measure may influence the reported level of perceptual awareness. Surprisingly, the overall relationship between awareness ratings and performance was weaker when participants rated their awareness before providing identification responses. Furthermore, the Perceptual Awareness Scale was most exhaustive only when used after the identification task, whereas confidence ratings were most exhaustive when used before the identification task. We conclude that the type of subjective measure applied may influence the reports on visual awareness. We also propose that identification task decisions may affect subsequent awareness ratings.     

Gradedness of visual awareness depends on attentional scope: Global perception is more graded than local perception

The gradedness or discreteness of our visual awareness has been debated. Here, we investigate the influence of spatial scope of attention on the gradedness of visual awareness. We manipulated scope of attention using hierarchical letter-based tasks (global: broad scope; local: narrow scope). Participants reported the identity of a masked hierarchical letter either at the global level or at the local level. We measured subjective awareness using the perceptual awareness scale ratings and objective performance. The results indicate more graded visual awareness (lesser slope for the awareness rating curve) at the global level compared to the local level. Graded perception was also observed in visibility ratings usage with global level task showing higher usage of the middle PAS ratings. Our results are in line with the prediction of level of processing hypothesis and show that global/local attentional scope and contextual endogenous factors influence the graded nature of our visual awareness.     

Interactions of reading and semantics along the ventral visual processing stream

Converging evidence supports a distributed-plus-hub view of semantic processing, in which there are distributed modular semantic sub-systems (e.g., for shape, colour, and action) connected to an amodal semantic hub. Furthermore, object semantic processing of colour and shape, and lexical reading and identification, are processed mainly along the ventral stream, while action semantic processing occurs mainly along the dorsal stream. In Experiment 1, participants read a prime word that required imagining either the object or action referent, and then named a lexical word target. In Experiments 2 and 3, participants performed a lexical decision task (LDT) with the same targets as in Experiment 1, in the presence of foils that were legal nonwords (NW; Experiment 2) or pseudohomophones (PH; Experiment 3). Semantic priming was similar in effect size regardless of prime type for naming, but was greater for object primes than action primes for the LDT with PH foils, suggesting a shared-stream advantage when the task demands focus on orthographic lexical processing. These experiments extend the distributed-plus-hub model, and provide a novel paradigm for further research.