从不平衡的视觉输入到不平衡的视觉注意：探寻短时程眼优势可塑性的神经机制

在个体视觉系统的发展过程中,视觉系统的结构与功能会受到视觉经验和内外部环境的影响而发生改变,这被称为视觉可塑性。视觉可塑性在出生后的发育关键期内达到峰值。虽然成年期视皮层神经环路的结构功能趋于稳定,但有越来越多的研究表明成年人视皮层中仍保留着一定程度的可塑性,其中的典型代表就是眼优势的可塑性。最近十几年的研究发现,短时程操控成年人的各种视觉输入信息,乃至调节两眼间注意资源的分配,都可以引起成年人眼优势发生偏移。然而,两者调节眼优势的神经机制可能并不相同。视觉输入对成年人眼优势的调节可能主要反映了视觉皮层的稳态可塑性机制;而注意对眼优势的影响则是一种高级加工对初级视觉皮层的反馈调节,目前可以用拮抗神经元的适应机制来作解释。未来研究可以寻找更加直接的证据来支持这一解释,此外也应重点关注注意与视觉输入之间会如何交互影响成年人眼优势。     

视知觉学习的认知与神经机制研究

知觉学习是指由于训练或经验而引起的长期稳定的知觉变化,是一种内隐性的学习。近20年来,视知觉学习的大量研究结果提示大脑皮层的各个区域,甚至包括初级感觉皮层,在成熟之后仍然具有一定的可塑性。该文根据近年来的研究进展,对视知觉学习在大脑的什么地方,什么时候,以何种方式发生等热点问题进行了探讨。研究提示,视知觉学习涉及了包括初级视皮层在内的多个大脑皮层,并且存在一种自上而下的调控机制;视知觉学习可以在不同的时间尺度上发生,快速学习之后将伴随着慢速学习;通过视知觉学习,人们对于复杂物体的表征将从高级皮层区域移向低级皮层区域,任务执行也将趋于自动化     

双侧梭状回面孔区在面孔加工中的功能分工与协作

梭状回面孔区(fusiform face area,FFA)是视觉皮层上专门加工面孔的区域。然而,双侧FFA在面孔加工中的功能分工与协作还存在争议。在特异性刺激的加工上,右侧FFA主要负责人类面孔类别的知觉,而左侧FFA的功能与面孔精细特征的感知有关;在皮层可塑性上,右侧FFA主要参与青少年的社会适应学习,而左侧FFA负责成年人的知觉学习;在面孔网络中,二者与不同区域的连接用以适应不同的认知需求;他们之间的有向协作具有任务特定性。未来研究需要回答三个问题:左侧FFA的可塑性程度及这一可塑性是否是认知特定的、左侧FFA及其形成的网络连接的认知意义,双侧FFA在面孔网络中的连接有向性等问题。     

聋人唇读的大脑机制研究

特定区域整合模型与信息传输接替模型提供了聋人唇读不同的大脑机制,前者认为聋人唇读是由特定大脑皮层(如TSS．后扣带回等)加工的结果,听觉皮层并未参与视觉语言认知加工;后者认为聋人唇读的大脑机制与正常人无声唇读的大脑机制基本相似,是通过皮层下的连接区域(如屏状核)激活了视觉皮层、听觉皮层等。但更多的证据支持信息传输接替模型。聋人的听觉皮层具有可塑性,早期的语言经验对言语加工神经通路的建立具有很大的影响。     

面孔吸引力的整体表征及其动态性增强

面孔作为一种高级的视觉刺激,在人际交往中有着无可替代的作用。其中,面孔吸引力更是影响着日常生活的重要社交决策,如择偶、交友、求职、社会交换等。长久以来,研究者们从面孔特征、社会信息和观察者因素等角度不断探索着人们对静态面孔吸引力的感知,且多从进化角度加以解释。但是,人们如何表征面孔吸引力以及其动态性增强机制仍未可知。本项目通过两个研究,分别从面孔吸引力的整体表征,以及面孔动态性通过影响整体加工、影响对整体信息和特征信息的注意、以及影响社会信息来增强吸引力,从这两个角度尝试回答这一问题。在研究1中,本项目从整体加工的角度探索了面孔吸引力的认知表征。研究1.1通过评分任务和适应范式探索高空间频率（更多局部特征）和低空间频率（更多整体特征）对面孔吸引力的影响,旨在从空间频率探讨面孔吸引力的整体表征。研究1.2通过操纵面孔对称性和面孔常态性探索面孔常态性在面孔对称性和面孔吸引力间的中介作用,探讨面孔吸引力的常态构型表征。研究1.3引入“三庭五眼”这一中国传统面孔审美理论,通过评分任务和适应范式研究“三庭五眼” 构型是否符合中国人对高吸引力中国面孔的表征,以此探讨面孔吸引力的整体表征。研究1.4通过评分任务和适应范式考察局部面孔遮挡是否促进整体面孔吸引力,以及这种促进作用是否由于人们通过局部特征“脑补”出了完整面孔。研究2从整体加工、注意和生命力的角度探讨面孔吸引力的动态性增强机制。研究2.1使用合成效应范式测量动态面孔吸引力的整体加工,探索动静态面孔的吸引力差异是否源于其整体加工程度的不同。研究2.2使用注意分散范式,并结合眼动技术,探讨人们对动静态面孔的注视模式是否存在差异,这种差异是否能解释动态面孔吸引力的增强。研究2.3结合问卷法、实验法和结构方程模型,考察了生命力这一社会因素对动静态面孔吸引力的影响。本项目探讨了面孔吸引力的认知表征以及其动态性增强机制,有助于我们进一步理解人们对面孔吸引力的认知加工以及人类欣赏美这一高级智能。同时,本项目的结果对于日常人际交往和面孔吸引力相关算法的优化等方面也有潜在的应用价值。     

面孔空想性错视及其神经机制

面孔空想性错视, 是指在不存在面孔的物体或抽象图案上看到面孔, 例如在月球表面看到面孔。它受到自下而上信息与自上而下加工的共同影响。近年来, 研究者通过行为实验、事件相关电位技术以及脑成像技术对不同的空想性错视影响因素进行研究。结果发现, 面孔空想性错视的产生取决于刺激是否包含类似面孔结构, 内部面孔模板是否能与当前刺激匹配, 以及有无面孔相关背景。同时也受到个体差异与情绪状态影响。脑成像研究发现, 在发生空想性错视时, 来自额叶区与枕叶视觉区的信息会在FFA进行整合。未来研究可以致力于探索面孔空想性错视中个体差异的行为与神经机制, 以及不同类型的自上而下调节之间的相互影响及其神经机制。     

面孔知觉中面孔性别与情绪表情的相互作用

面孔知觉中, 面孔性别与表情的加工有不同的机制。Bruce和Young (1986)及Haxby, Hoffman和Gobbini (2000)的面孔知觉理论虽然对表情加工也较为关注, 但对面孔性别加工机制的解释却较少, 也未能明确面孔性别与表情的相互关系。当前关于两者是否独立加工尚无明确结论, 但更多证据支持它们相互影响。我们认为, Garner范式下面孔性别与表情加工的研究可能忽略了面孔熟悉性因素。同时, 面孔适应范式为该研究领域提供了新的思路。此外, 文章对于两者相互作用的机制也进行了一定的探讨。     

躯体表情与面部表情加工进程比较

躯体和面孔是个体情绪识别的敏感线索。与面部表情的早期视觉加工相似, P1成分对恐惧、愤怒等负性躯体表情更加敏感, 反映了对躯体威胁信息快速且无意识的加工。情绪躯体和面孔还有着类似的构型加工, 表现为二者都能诱发颞枕区视觉皮层相似的N170成分, 但涉及的神经基础并不完全相同。在构型编码加工中, 面部表情的N170与顶中正成分(Vertex Positive Potential, VPP)较躯体表情的N170、VPP更加明显。在面部表情和躯体表情的后期加工阶段, 早期后部负波(Early Posterior Negativity, EPN)反映了面孔和躯体视觉编码的注意指向加工, 随后出现的P3与晚期正成分(Late Positive Component, LPC)代表了顶额皮层对复杂情绪信息的高级认知加工。躯体表情还存在与外纹状皮层躯体区相关的N190成分, 其对躯体的情绪和动作信息敏感。今后的研究应进一步探讨动作对情绪知觉的影响、动态面孔−躯体情绪的加工机制等。     

情绪面孔的意识神经相关物及其无意识自动加工：来自事件相关电位的证据

意识的神经相关物尚有争议, 且个体能否无意识自动检测视觉环境变化尚不清楚。本研究采用非注意视盲范式操控视觉意识, 并引入具有社会信息的情绪面孔, 探讨意识的神经相关物以及视觉意识与自动检测变化机制的关系。在A阶段, 部分被试对任务无关的情绪面孔处于无意识水平; 在B阶段, 所有被试对任务无关的情绪面孔处于意识水平; 在C阶段, 所有被试对任务相关的情绪面孔处于意识水平。结果显示, 任务无关的情绪面孔的意识过程诱发视觉意识负波(visual awareness negativity, VAN)、晚期正成分(late positivity, LP)和晚期枕区正成分(late occipital positivity, LOP)。此外, 无意识的情绪面孔能诱发视觉失匹配负波(visual mismatch negativity, vMMN), 且其幅值不受意识影响, 但是受任务相关性调制。这些结果提示对情绪面孔的视觉意识在不同的时间进程上有不同的ERP指标——VAN反映早期知觉经验, 而LP和LOP反映晚期意识过程, 而且面孔情绪信息的自动加工独立于视觉意识, 但是受视觉注意调制。     

面孔审美加工的神经机制及个体差异

外显和内隐的面孔审美加工的脑成像研究表明,美的面孔比不美的面孔导致眶额皮层、伏隔核、杏仁核等奖赏脑区更大的激活。脑电研究则发现了与面孔审美加工有关的早期负波和晚期正成分。面孔审美加工有关的脑区活动也受到性别、生理周期等个体因素的调节。未来的研究需要比较美的面孔与其它奖赏刺激加工的神经机制,探讨面孔审美加工的不同阶段及时间进程,在面孔知觉的框架下形成合理的面孔审美加工的神经模型。     

The motion aftereffect

The motion aftereffect is a powerful illusion of motion in the visual image caused by prior exposure to motion in the opposite direction. For example, when one looks at the rocks beside a waterfall they may appear to drift upwards after one has viewed the flowing water for a short period-perhaps 60 seconds. The illusion almost certainly originates in the visual cortex, and arises from selective adaptation in cells tuned to respond to movement direction. Cells responding to the movement of the water suffer a reduction in responsiveness, so that during competitive interactions between detector outputs, false motion signals arise. The result is the appearance of motion in the opposite direction when one later gazes at the rocks. The adaptation is not confined to just one population of cells, but probably occurs at several cortical sites, reflecting the multiple levels of processing involved in visual motion analysis. The effect is unlikely to be caused by neural fatigue; more likely, the MAE and similar adaptation effects provide a form of error-correction or coding optimization, or both.     

Gamma神经振荡和信息整合加工

Gamma神经振荡是一种基础神经活动。它的特性使其与“信息整合加工”产生了潜在联系。已有研究显示, 自下而上的跨通道信息整合与感觉皮层的Gamma振荡同步化有关; 单通道自上而下的信息整合与高级皮层的Gamma振荡增强有关。现有的“神经耦合理论”和“匹配利用模型”分别描述了Gamma振荡如何在“自下而上”及“自上而下”的信息整合中发挥作用。Gamma振荡虽与整合加工密切相关, 但作为指标需谨慎。对于Gamma振荡在复杂情景整合加工中的作用仍待探究。     

Orientation-selective adaptation to crowded illusory lines

Visual adaptation has been successfully used as a psychophysical tool for studying the functional organisation of visual awareness. It has been shown that orientation-selective adaptation to a grating pattern occurs in crowded conditions. In such conditions, simultaneous presentation of flanking distractors pushes the target stimulus out of conscious perception and severely impairs orientation discrimination in the periphery of the visual field. In the present study, orientation-selective adaptation to illusory lines induced by two line gratings abutting each other with a phase shift was examined in crowded and non-crowded conditions. To rule out the effects of lower level adaptations we used an animation paradigm in which the orientations of the two line gratings were altered repeatedly during adaptation phase without any change in the orientation of the resulting illusory line. Although performance of subjects in reporting the orientation of crowded illusory lines was at chance level, orientation-selective adaptation was preserved for crowded as well as non-crowded adapting targets. Two control experiments demonstrated that adaptation to endpoints of real lines at the location of abutting grating lines had minimal effect on the adaptation to illusory lines; and changes in the configuration of endpoints could not be responsible for better performance when adapting and test stimuli were different. We conclude that a crowding effect occurs after illusory lines have been processed in the visual stream. Since illusory lines seem to be represented at relatively early stages of visual processing (e.g. area V2), adaptation to crowded illusory stimuli suggests that neuronal activation in those early stages is not necessarily correlated with conscious perception.     

Selection from perceptual and conceptual representations

The lateral prefrontal cortex has been implicated in a wide variety of functions that guide our behavior, and one such candidate function is selection. Selection mechanisms have been described in several domains spanning different stages of processing, from visual attention to response execution. Here, we consider two such mechanisms: selecting relevant information from the perceptual world (e.g., visual selective attention) and selecting relevant information from conceptual representations (e.g., selecting a specific attribute about an object from long-term memory). Although the mechanisms involved in visual selective attention have been well characterized, much less is known about the latter case of selection. In this article, we review the relevant literature from the attention domain as a springboard to understanding the mechanisms involved in conceptual selection.     

Neural adaptation across viewpoint and exemplar in fusiform cortex

The visual system has the remarkable ability to generalize across different viewpoints and exemplars to recognize abstract categories of objects, and to discriminate between different viewpoints and exemplars to recognize specific instances of particular objects. Behavioral experiments indicate the critical role of the right hemisphere in specific-viewpoint and -exemplar visual form processing and the left hemisphere in abstract-viewpoint and -exemplar visual form processing. Neuroimaging studies indicate the role of fusiform cortex in these processes, however results conflict in their support of the behavioral findings. We investigated this inconsistency in the present study by examining adaptation across viewpoint and exemplar changes in the functionally defined fusiform face area (FFA) and in fusiform regions exhibiting adaptation. Subjects were adapted to particular views of common objects and then tested with objects appearing in four critical conditions: same-exemplar, same-viewpoint adapted, same-exemplar, different-viewpoint adapted, different-exemplar adapted, and not adapted. In line with previous results, the FFA demonstrated a release from neural adaptation for repeated different viewpoints and exemplars of an object. In contrast to previous work, a (non-FFA) right medial fusiform area also demonstrated a release from neural adaptation for repeated different viewpoints and exemplars of an object. Finally, a left lateral fusiform area demonstrated neural adaptation for repeated different viewpoints, but not exemplars, of an object. Test-phase task demands did not affect adaptation in these regions. Together, results suggest that dissociable neural subsystems in fusiform cortex support the specific identification of a particular object and the abstract recognition of that object observed from a different viewpoint. In addition, results suggest that areas within fusiform cortex do not support abstract recognition of different exemplars of objects within a category.     

Age differences in processing fluctuations in postural control across trials and across days

Postural control performances of 18 younger and 18 older adults were repeatedly measured on 45 weekdays with five trials per day. This design made it possible to dissociate between long-term trends and processing fluctuations in the sensorimotor domain at moment-to-moment, trial-to-trial, and day-to-day levels. Older adults fluctuated more than younger adults at all timescales. Age differences in trial-to-trial and day-to-day processing fluctuations were reduced but remained statistically significant when controlling for fluctuations on faster timescales. We concluded that age differences in intraindividual fluctuations at the longer timescales are in part related to age differences in low-level system robustness, suggesting a cascade of effects across multiple timescales.     

Kinematic Analyses of Manual Asymmetries in Visual Aiming Movements

The right hand advantage has been thought to arise from the greater efficiency of the right hand/left hemisphere system in processing visual feedback information. This hypothesis was examined using kinematic analyses of aiming performance, focusing particularly on time after peak velocity which has been shown to be sensitive to visual feedback processing demands. Eight right-handed subjects pointed at two targets with their left and right hands with or without vision available and either as accurately or as fast as possible. Pointing errors and movement time were found to be smaller with the right hand. Analyses of the temporal componenets of movement time revealed that the hands differed only in time after peak velocity (in deceleration), with the right hand spending significantly less time. This advantage for the right hand, however, was apparent whether or not vision was available and only when accuracy was emphasized in performance. These findings suggest that the right hand system may be more efficient at processing feedback information whether this be visual or nonvisual (e.g., proprioceptive).     

Internally augmented displays: contingent aftereffects as performance aids

Previous research on visual contingent aftereffects has been concerned with examining the effects of various parameters (e.g., spatial frequency and luminance) on the adaptation to, and decay of, contingent aftereffects. The current study tested the viability of using visual contingent aftereffects in a display context. Using established characteristics of contingent aftereffects, a program of contingent aftereffect adaptation was designed. Studies were conducted to determine if subjects who were adapted to see visual contingent aftereffects invoked by a visual display could achieve more rapid or certain identification of a display under low luminance conditions. The results confirmed (a) that contingent aftereffects can improve performance on a visual discrimination task requiring information from a display and (b) that contingent aftereffects are more enhanced at low levels of illumination.     

Selective visual attention modulates the direct tilt aftereffect

One's being able to allocate attention to particular regions or properties of the visual field is fundamental to visual information processing. Visual attention determines what input is carefully analyzed and what input is more or less ignored. But at what stage of the visual system is this process evident? We describe three experiments that demonstrate an effect of voluntary spatial attention and voluntary object-based attention on an orientation illusion (the tilt aftereffect) that is believed to take place in primary visual cortex. This finding, in which selective visual attention influences adaptation to visual orientation information, contributes to mounting evidence for a view of visual perception in which mutual interaction takes place between high-level and low-level subsystems.     

The many directions of time

Event duration perception is fundamental to cognitive functioning. Recent research has shown that localized sensory adaptation compresses perceived duration of brief visual events in the adapted location; however, there is disagreement on whether the source of these temporal distortions is cortical or pre-cortical. The current study reveals that spatially localized duration compression can also be direction contingent, in that duration compression is induced when adapting and test stimuli move in the same direction but not when they move in opposite directions. Because of its direction-contingent nature, the induced duration compression reported here is likely to be cortical in origin. A second experiment shows that the adaptation processes driving duration compression can occur at or beyond human cortical area MT+, a specialized motion center located upstream from primary visual cortex. The direction-specificity of these temporal mechanisms, in conjunction with earlier reports of pre-cortical temporal mechanisms driving duration perception, suggests that our encoding of subsecond event duration is driven by activity at multiple levels of processing.