Working memory impairment in people with Williams syndrome: Effects of delay, task and stimuli

Williams syndrome (WS) is a neurodevelopmental disorder associated with impaired visuospatial representations subserved by the dorsal stream and relatively strong object recognition abilities subserved by the ventral stream. There is conflicting evidence on whether this uneven pattern in WS extends to working memory (WM). The present studies provide a new perspective, testing WM for a single stimulus using a delayed recognition paradigm in individuals with WS and typically developing children matched for mental age (MA matches). In three experiments, participants judged whether a second stimulus ‘matched’ an initial sample, either in location or identity. We first examined memory for faces, houses and locations using a 5 s delay (Experiment 1) and a 2 s delay (Experiment 2). We then tested memory for human faces, houses, cat faces, and shoes with a 2 s delay using a new set of stimuli that were better controlled for expression, hairline and orientation (Experiment 3). With the 5 s delay (Experiment 1), the WS group was impaired overall compared to MA matches. While participants with WS tended to perform more poorly than MA matches with the 2 s delay, they also exhibited an uneven profile compared to MA matches. Face recognition was relatively preserved in WS with friendly faces (Experiment 2) but not when the faces had a neutral expression and were less natural looking (Experiment 3). Experiment 3 indicated that memory for object identity was relatively stronger than memory for location in WS. These findings reveal an overall WM impairment in WS that can be overcome under some conditions. Abnormalities in the parietal lobe/dorsal stream in WS may damage not only the representation of spatial location but may also impact WM for visual stimuli more generally.     

道路交通标志中对称结构效应的眼动研究

本研究考察了道路交通标志中路名信息对称结构效应的眼动模式。实验采用眼动跟踪技术和视觉搜索范式,共有16名被试参加。实验结果表明：（1）在对称结构路名信息的视觉搜索中,被试的反应正确率明显优于非对称结构条件下的正确率;（2）对称结构条件下,被试的注视点和回扫次数明显较少,凝视时间明显较短;（3）在以道路交通标志为视觉搜索材料时,搜索区有无路名目标对视觉搜索绩效没有影响。可以认为：在道路交通标志中存在对称结构效应;眼动模式的差异是引起对称结构效应的认知机制。     

Local rather than global processing of visual arrays in numerosity discrimination by pigeons (Columba livia)

A series of experiments investigated which stimulus properties pigeons use when they discriminate pairs of visual arrays that differ in numerosity. Transfer tests with novel stimuli confirmed that the birds’ choices were based on relative differences in numerosity. However, pigeons differed from other species in the non-numerical cues that affected their choices. In human and non-human primates, numerical discrimination is often influenced by continuous variables such as surface area or overall stimulus brightness. Pigeons showed little evidence of using those cues, even when summed area and brightness had been correlated with numerosity differences and reward outcome. But when array-element sizes were asymmetrically distributed across numerosities, the birds readily utilized information about item sizes as an additional discriminative cue. These novel results are discussed in relation to pigeons’ tendency to focus on local, rather than global dimensions when they process other non-numerical complex visual stimuli. The findings suggest there may be inter-specific differences in the type of perceptual information that provides the input stage for mechanisms underlying numerical processing. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

视觉表象扫描的概念控制

将表象扫描和概念提示范式相结合, 在三个实验中通过考察概念控制下表象扫描加工中的参照系冲突效应以及概念参照系的优先性, 进而揭示表象扫描加工中的自上而下控制机制。结果发现：(1) 正立或旋转方位汉字提示下表象扫描加工中出现了参照轴效应, 箭头提示下不存在这种效应, 表明不同提示引发了不同空间关系计算过程; (2) 在表象扫描概念控制过程中, 概念参照系、环境(重力)参照系及提示汉字内在参照系同时被激活, 它们可能处于不同冲突状态, 解决这些冲突具有不同认知代价; (3) 在解决不同参照系冲突过程中, 反映自上而下加工的概念参照系总能通过抑制其它参照系而取得优先地位, 表明人的认知系统能够对表象加工进行自上而下的主动控制, 这种主动控制反映了一种执行功能。     

大脑视觉词形区及其在阅读神经网络中的作用

大脑梭状回中部被认为是视觉词形加工区(Visual Word Form Area, VWFA)。近年来的研究对VWFA的功能提出了质疑, 研究者开始关注VWFA作为复杂阅读网络的一部分与其它脑区的动态联结机制, 主要集中在三个方面：一是梭状回中部对于视觉词形选择性敏感的本质; 二是它在词汇阅读的神经网络中的作用; 最后是语言经验对于VWFA认知神经功能的塑造作用。结合以上研究的最新进展, 文中指明从动态神经网络的角度揭示大脑功能成为今后认知神经科学研究的最新取向。     

识别电位认知功能探析

识别电位(Recognition Potential, RP)是被试看到可识别视觉刺激时, 在200~250ms内达到峰值的脑电反应。识别电位的研究正处于理论探讨阶段, 有两种主要观点用于解释RP。一种观点强调RP反映了视知觉分析成分; 另一种观点强调RP反映了语义或概念加工成分。两种观点至今未达成一致。最近, 针对两种观点质疑, 研究者们提出了类别特征加工的观点, 这一新观点在理论上符合大脑经济性的原则, 具有一定的优越性, 但尚需要更多的实证研究的支持。未来的RP研究应从实验材料的多样化、多研究方法结合、类别特征加工能力的习得机制等方面展开。     

视觉表象扫描中的视角大小效应

采用视觉表象的几何距离扫描任务,通过两个实验首次揭示了视觉表象扫描中的视角大小效应。实验一采用3 (视角：2.7°,5.5°和8.2°) × 3 (扫描距离：0.0cm、0.4cm和0.8cm) 组内实验设计,探讨了视角大小这种表象前加工因素是否影响心理扫描的问题;实验二采用8 (视角：2.7°,4.1°,5.5°,6.9°,8.2°,9.6°,12.3°和17.1°) × 2 (扫描距离：0.4cm和0.8cm) 组内实验设计,探讨了视角大小如何影响心理扫描加工过程的问题。结果表明：（1）在视觉表象扫描中,扫描时间会受到表象对应刺激的视角大小影响,即使扫描的几何距离相等,不同视角大小条件下的扫描时间仍存在显著差异;（2）在4°到10°这个视角范围内心理扫描的时间显著短于这个范围之外的扫描时间,6.5°左右是视觉表象扫描的最佳视角。视角大小效应有别于心理扫描的大小效应和距离效应,为Kosslyn的表象计算理论增加了新的内容,具有重要的理论意义。同时它对仪表、图形设计以及棋牌游戏等工作和生活实践具有一定的应用价值     

客体在视觉工作记忆中的存储机制

采用变化觉察范式,通过两个实验对不同类型视觉信息在工作记忆中的存储机制进行了探讨。实验一中要求记忆的客体由颜色和形状两基本特征构成;实验二中的客体为具有不同颜色及开口朝向的兰道环。通过观察检测项变化方式对记忆绩效的影响,获得以下结论:（1）对颜色和形状两基本特征的存储以整合客体为单位;（2）兰道环的颜色与开口朝向信息难以以整合客体方式存储。笔者推测,视觉工作记忆中存储的整合客体并非如现有理论假设的,是在集中注意参与下创建的,而是由并行加工阶段所获信息构成;客体中所含需集中注意提取的细节特征信息难以与其基本特征信息整合于该客体表征     

The effect of frame figure type and frame size on the line and the circle Ponzo illusions

Abstract:   To examine the determinants of the Ponzo illusion, we compared the perceived size of lines and circles presented within three different frames: two converging lines, two circles, and two squares. Twenty stimulus figures, consisting of two types of objects (lines/circles) × three types of frame figures (Ponzo/circles/squares) × three sizes of lower frames (small/medium/large), and two control figures were presented on a personal computer display. Twelve students performed three measurements (upper-object/lower-object/illusion) for each stimulus figure using the method of adjustment. To analyze the relationship between single object perception and the Ponzo illusion, we compared the calculated values of overestimation magnitude differences between the upper and lower objects with the actual obtained illusion values of the six object-frame conditions. The calculated values of the circle and the square frame figures corresponded to the difference between the upper single object and the lower single object. In contrast, the results of the Ponzo figure need an additional factor to explain the differences between the obtained and the calculated values. These results indicate that two factors are involved in the Ponzo illusion: (a) the framing effect affects the perceived size of the individual single objects, and (b) the comparison factor affects the comparison process of the two objects within the converging lines.     

Cortical locus of coherent motion deficits in deaf poor readers

Samar and Parasnis [Samar, V. J., & Parasnis, I. (2005). Dorsal stream deficits suggest hidden dyslexia among deaf poor readers: correlated evidence from reduced perceptual speed and elevated coherent motion detection thresholds. Brain and Cognition, 58, 300-311.] reported that correlated measures of coherent motion detection and perceptual speed predicted reading comprehension in deaf young adults. Because deficits in coherent motion detection have been associated with dyslexia in the hearing population, and because coherent motion detection is strongly dependent on extrastriate cortical area MT, these results are consistent with the claim that hidden dyslexia occurs within the deaf population and is associated with deficits in MT. However, coherent motion detection can also be influenced by subcortical deficits in both magnocellular and parvocellular pathways. To confirm the putative cortical locus of coherent motion perception deficits, we measured contrast thresholds for detecting the direction of movement of drifting sine wave gratings in the same participant group as [Samar, V. J., & Parasnis, I. (2005). Dorsal stream deficits suggest hidden dyslexia among deaf poor readers: correlated evidence from reduced perceptual speed and elevated coherent motion detection thresholds. Brain and Cognition, 58, 300-311.], under stimulus conditions that selectively biased for input from the subcortical magnocellular and parvocellular pathways, respectively. Contrast thresholds were not related to reading comprehension performance under either the magnocellular or parvocellular conditions. Furthermore, the previously reported correlations among reading comprehension, coherent motion thresholds, and perceptual speed remained significant even after contrast thresholds and non-verbal IQ were controlled in partial correlation analyses. In addition, coherent motion detection thresholds were found to correlate specifically with a reading-IQ discrepancy score, one commonly used indicator of dyslexia. These results provide direct psychophysical evidence that the previously reported deficit in coherent motion detection in deaf poor readers does not involve subcortical pathway deficits, but rather is associated with a cortical deficit likely involving area MT. They also strengthen the argument for the existence of hidden dyslexia in the deaf adult population.