The effects of task-irrelevant threatening stimuli on orienting- and executive attentional processes under cognitive load

Human visual attention is biased to rapidly detect threats in the environment so that our nervous system can initiate quick reactions. The processes underlying threat detection (and how they operate under cognitive load), however, are still poorly understood. Thus, we sought to test the impact of task-irrelevant threatening stimuli on the salience network and executive control of attention during low and high cognitive load. Participants were exposed to neutral or threatening pictures (with moderate and high arousal levels) as task-irrelevant distractors in near (parafoveal) and far (peripheral) positions while searching for numbers in ascending order in a matrix array. We measured reaction times and recorded eye-movements. Our results showed that task-irrelevant distractors primarily influenced behavioural measures during high cognitive load. The distracting effect of threatening images with moderate arousal level slowed reaction times for finding the first number. However, this slowing was offset by high arousal threatening stimuli, leading to overall shorter search times. Eye-tracking measures showed that participants fixated threatening pictures more later and for shorter durations compared to neutral images. Together, our results indicate a complex relationship between threats and attention that results not in a unitary bias but in a sequence of effects that unfold over time.     

Visual attention capacity: a review of TVA-based patient studies

Psychophysical studies have identified two distinct limitations of visual attention capacity: processing speed and apprehension span. Using a simple test, these cognitive factors can be analyzed by Bundesen's Theory of Visual Attention (TVA). The method has strong specificity and sensitivity, and measurements are highly reliable. As the method is theoretically founded, it also has high validity. TVA-based assessment has recently been used to investigate a broad range of neuropsychological and neurological conditions. We present the method, including the experimental paradigm and practical guidelines to patient testing, and review existing TVA-based patient studies organized by lesion anatomy. Lesions in three anatomical regions affect visual capacity: The parietal lobes, frontal cortex and basal ganglia, and extrastriate cortex. Visual capacity thus depends on large, bilaterally distributed anatomical networks that include several regions outside the visual system. The two visual capacity parameters are functionally separable, but seem to rely on largely overlapping brain areas.     

What is special about the index finger?: The index finger advantage in manipulating reflexive attentional shift1

Pointing with the index finger is a universal behavior. However, the functional significance of indexical pointing has not been examined empirically. We examined the efficacy of various pointing gestures in evoking viewer's attentional shifts. After viewing the gesture cue, observers quickly reported the location of a visual target. With a short cue‐target delay, reaction times were generally shorter for the target at the location where gesture cues pointed, but not with a long cue‐target delay. Moreover, the indexical pointing gesture produced a significantly larger cueing effect than the other gestures. Our control experiments indicated that the index‐finger advantage is tightly linked to the proper morphological shape (i.e. length and position of the index finger) of the indexical pointing and is not explained by the directional discriminability of the gesture. The visual system seems to use mechanisms that are partially independent of the directional discrimination of gestures, in order to quickly modulate the viewer's attention.     

光栅朝向分辨学习中存在关于45°对角线对称的镜像迁

采用光栅朝向分辨任务来探讨视知觉学习中是否存在关于45°对角线对称的镜像迁移现象。训练被试分辨15°或75°朝向3或5天,每天约1小时,训练前后测量15°、75°、45°朝向的分辨阈值。通过训练,训练朝向（15°或75°）的阈值下降,该学习效应没有迁移至45°朝向,但基本迁移到关于45°对称的朝向（75°或15°）上。这提示,视知觉学习可能发生在中间视皮层,该皮层同时具有一定的朝向特异性和关于45°对角线对称的镜像迁移性     

时间隐喻对时距判断的影响作用

本研究考查了反映不同时速的时间隐喻句对时距判断的影响,结果发现时间隐喻表征对时距判断有导向功能,即将移动速度慢的喻体投射于时间时会带来对时距判断的高估,而将移动速度快的喻体投射于时间时会造成对时距判断的低估,这一结果表明语言也会是影响时距判断的因素之一,从而进一步佐证了时间认知的综合观。     

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。     

刺激的知觉辨认难度与大脑两半球间的分布式加工

采用半视野速示术将标准刺激在中间视野呈现,比较刺激以不同偏心视角（3.5°,5°和6.5°）在左或右视野同时呈现,以检查不同偏心视角引起比较刺激知觉辨认难度的改变对汉字大写数字奇－偶概念同/异判断任务在大脑两半球间分布式加工的影响。结果显示：随偏心视角的增大正确反应时和错误百分数均显著提高;三种视角条件下左右手的正确反应时均有明显的右视野（左半球）优势;3.5°视角右视野（左半球）呈现时右手反应明显快于左手,5°视角右视野（左半球）与左视野（右半球）呈现时均为右手反应明显快于左手,6.5°视角右视野（左半球）与左视野（右半球）呈现时均为左手反应明显快于右手。这些结果提示：本研究条件下只有比较刺激在6.5°偏心视角呈现时刺激和反应可能出现大脑两半球间分布式加工,3.5°和5°视角呈现时可能为左半球单独加工。6.5°视角刺激呈现的分布加工明显由于大视角呈现时比较刺激辨认难度与注意要求的提高所致。     

视觉空间注意的事件相关电位研究

视觉空间注意是心理学多年来一直探讨的问题,也是近来多学科共同关注的领域。在脑机制研究中,事件相关电位(ERP)的研究方法具有高时间分辨率的特点,近年来高密度记录技术的发展,也提高了ERP在功能定位方面的作用,因此其应用日益广泛。该文概述了近年来有关ERP在视觉空间注意研究中的实验方法、结果和初步结论,并就今后研究方向提出了几点看法。     

位置提示下视觉注意范围的调控机制

研究视觉空间注意中不同注意范围引起脑内加工时程的动态变化。使用固定位置的、三种不同直径的线圈作为注意范围的位置性提示,祛除空间定位因素的影响,记录反应时和事件相关电位（ERP）数据。结果显示：在同等注意范围时,随着刺激位置远离视野中心,反应时延长,靶刺激诱发的P1、N1不受刺激位置的影响,而其前部N2的波幅明显受到刺激位置的影响;在靶刺激位置相同时,随着注意范围的扩大,反应时缩短,靶刺激诱发的P1、N1不受提示范围大小的影响,而其前部P2的波幅明显受到注意范围的影响。结果说明：①视觉注意范围信息加工与靶刺激诱发的P2成分相关;②视觉注意诱发的P1、N1成分,主要与注意方位相关,而与注意范围大小无关;③注意范围变化引起注意集中度的调节是在一定范围内进行的。     

面孔加工的认知神经科学研究：回顾与展望

面孔加工的认知神经科学研究中的核心问题是,是否存在功能和神经机制上独立的面孔加工模块以及面孔加工系统的组织形式。使用电生理、脑成像以及对脑损伤病人进行神经心理学检查等手段,研究者已经找到选择性地对面孔反应的脑区,即梭状回面孔区（FFA）。文章从面孔加工系统的特异性与多成分性以及面孔识别模型等方面,系统回顾了该领域的主要研究成果。文章最后还简单展望了今后的研究方向。