发展性阅读障碍的脑区连接异常

过去几十年中, 研究者基于脑区功能定位的思想对发展性阅读障碍的神经机制进行了大量的研究, 揭示出阅读障碍者在特定脑区的异常。近些年, 考虑到阅读加工过程的复杂性以及需要多脑区协同参与的特点, 越来越多的研究者从脑区连接的角度探讨阅读障碍的神经机制。结果发现阅读障碍者在阅读相关脑区间的白质结构连接和功能连接上均表现出异常, 这说明阅读技能受损和脑区连接异常之间存在着密切的联系。未来的研究还需进一步探讨脑区连接异常和特定脑区异常之间的关系, 以及结合基因、脑、行为和环境等多个因素探寻阅读障碍的发生机制。     

发展性阅读障碍的注意缺陷研究现状

近年来,发展性阅读障碍的注意缺陷研究逐渐受到重视.行为实验发现,阅读障碍者有多种注意缺陷现象,主要表现为“视野不对称性”和“注意转换延迟”.脑电研究表明,阅读障碍的注意缺陷与大脑后顶叶皮层功能异常有关.大细胞通路假设认为,阅读障碍的视知觉缺陷来源于视觉大细胞受损,大细胞通路所加工的信息主要投射到靠近颞枕顶联合区的V5MT区,这个脑区为后顶叶皮层提供大量投射.因此,阅读障碍的注意缺陷与大细胞通路受损存在一定关系.     

动作视频游戏对发展性阅读障碍者阅读技能的影响及其内在机制

发展性阅读障碍是一种在获得阅读技能方面的特殊困难, 这种障碍会严重影响个体的发展, 如何帮助发展性阅读障碍者改善其阅读技能是近年来研究的焦点。传统的干预方法主要针对发展性阅读障碍者的语音缺陷, 这类方法存在一些问题, 如费时费力、给阅读障碍者带来阅读压力等。近年来, 大部分研究表明通过趣味性的动作视频游戏训练可以显著地提高发展性阅读障碍者的阅读技能, 但是其背后的机制尚不明确。基于大细胞通路缺陷理论框架, 从视觉空间注意、注意跨通道转换、视觉运动加工等方面来梳理动作视频游戏与阅读之间的关系, 揭示了动作视频游戏训练对阅读效率影响的可能内在机制。未来的研究可以在大细胞通路缺陷理论的框架下, 深入分析动作视频游戏改善阅读的神经机制, 并尝试开发更适合发展性阅读障碍者的干预程序。     

发展性阅读障碍的生理基础

发展性阅读障碍是关系人类健康和发展的重要课题,对其产生机制的探讨有利于寻找适当的治疗方法.文章在简要回顾阅读障碍的界定、研究内容和有关理论争论基础上,重点介绍了阅读障碍的神经基础和遗传机制.文章从大脑结构和功能单侧化、完成认知任务时大脑的激活模式、激活时间进程以及视觉巨细胞等方面介绍了发展性阅读障碍者与正常读者之间存在的差异.文章还指出许多双生子研究都发现同孪双生子的阅读障碍同现率高于异孪双生子,尤其是近期的遗传学研究鉴定出几个与阅读障碍有关的染色体,如6号和15号染色体与语音障碍和拼写障碍有关.这些研究结果说明发展性阅读障碍有一定的脑神经基础和遗传基础.     

发展性阅读障碍风险儿童的大脑异常及阅读障碍的早期神经标记

考察发展性阅读障碍风险儿童的神经异常有助于找到阅读障碍的早期神经标记物,对实现阅读障碍早期预测和干预具有重要意义。基于风险儿童的横向研究显示,其大脑的功能和结构存在异常。具体表现在风险儿童感知语音及非语音诱发的失匹配波(MMR,MismatchResponse)波幅更小,潜伏期更长,在阅读的腹侧和背侧通路功能和结构存在异常。相比于学龄前横向比较,追踪到学龄后的研究可以发现与阅读发展相关的神经变化,揭示阅读障碍的早期神经标记。纵向研究显示,语音加工诱发的MMR、左侧颞顶区、视觉词形区功能异常及左侧弓状束结构异常是阅读障碍的早期生物学标记。此外,风险儿童大脑异常的纵向研究相对稀少,同时较小的样本量也会降低结果的可信度。未来需要强调更大样本量的纵向研究,同时关注汉语风险儿童的大脑异常,探究汉语阅读障碍认知神经风险因素的特殊性和普遍性。     

发展性阅读障碍的视觉注意广度技能

发展性阅读障碍在许多任务中都出现同时性加工多个视觉刺激的困难, 即视觉注意广度缺陷.本文分别综述了国内外探查阅读障碍视觉注意广度的研究.目前, 相关研究结果仍存争议, 这可能与背景语言的正字法深度以及被试年龄发展差异有关.未来研究还需利用干预,跨语言比较等方法进一步探讨阅读障碍与视觉注意广度之间的关系, 并结合脑电,脑成像技术探究汉语阅读障碍视觉注意广度的内在神经机制.     

发展性阅读障碍与小脑异常：小脑的功能和两者的因果关系

发展性阅读障碍(下文简称为“阅读障碍”)不仅会影响个人的终身发展, 还会对社会造成沉重的经济负担, 深入探讨相关的神经机制, 对实现阅读障碍的早期预测和干预十分重要。以往关于阅读障碍神经机制的模型多集中于大脑, 近些年的研究发现, 阅读障碍也与小脑异常有关, 但到目前为止我们仍不清楚两者的关系。通过总结最新的研究进展, 我们发现小脑在阅读障碍中可能发挥着多种功能, 且小脑异常与阅读障碍可能互为因果。在此基础之上, 我们提出了“阅读中小脑与大脑的功能映射假说”, 旨在从一个全新的角度揭示小脑与阅读的关系, 以及两者与大脑的关系。相关内容对全面揭示阅读障碍的神经机制, 以及小脑在高级认知加工中的作用, 具有重要的启示意义。     

汉语发展性阅读障碍儿童视觉同时性加工技能子成分的发展及其与阅读的关系

通过分别以高频汉字(实验1)和图形非言语材料(实验2)为刺激的两个联合视觉注意任务, 并采用基于Budensen视觉注意理论的参数估计方法, 系统地探查小学三~六年级汉语发展性阅读障碍儿童的视觉同时性加工技能缺陷的内在机制。以43名汉语发展性阅读障碍儿童和46名生理年龄匹配典型发展儿童为被试, 每类被试均被分为小学中年级组(三、四年级)和高年级组(五、六年级)。两个实验均发现不同年级组的阅读障碍儿童在知觉加工速度参数上显著小于控制组儿童。在空间注意分布权重参数上, 实验1的结果显示, 不同于控制组儿童向左侧化发展的注意分布模式, 两个年级组的阅读障碍儿童均表现为无偏的注意分布; 而实验2未发现显著组别差异。且这两种同时性加工子技能分别与不同水平的汉语阅读技能密切相关。结果表明, 汉语阅读障碍儿童在同时加工多个视觉刺激时存在持续的知觉加工速度缓慢的问题, 在同时加工言语类刺激时还表现出异常的空间注意分布模式。本研究有助于从基础认知层面揭示汉语发展性阅读障碍儿童的缺陷机理, 为进一步设计相关的提高阅读效率的干预方案提供理论依据。     

孤独症谱系障碍者的视觉-空间工作记忆缺陷及脑机制

孤独症谱系障碍(ASD)个体存在视觉-空间工作记忆加工缺陷,主要表现在4个方面,即随认知负荷增大而缺陷加重、工作记忆容量不足、工作记忆加工过程中的注意功能失调和对刺激进行整体组织的能力缺乏。神经机制研究显示,ASD个体存在明显的额-顶工作记忆网络激活异常,以及相关脑区的脑结构、白质连接异常。另外,作为基础性的认知加工过程,ASD个体的视觉-空间工作记忆各加工环节与言语工作记忆、执行功能、社会认知等因素均存在交互影响。纵观目前研究成果,未来研究可从研究手段、机制探究和干预训练三方面入手,着眼于研究方法的生态化和多元化,揭示客体和空间工作记忆的机制分离,并着力开发更具针对性的干预训练模式。     

汉语发展性阅读障碍儿童的不同视野注意能力

以某城市小学三至五年级的学生为研究对象,筛选出发展性阅读障碍和同年龄对照组两组儿童,采用不同视角的刺激探测任务初步探查了汉语发展性阅读障碍儿童的不同视野注意能力及特点。研究使用圆点、数字和汉字三种刺激类型并设置了3°,12°,17°三种视角条件。结果发现,在数字和汉字条件下,汉语发展性阅读障碍儿童对刺激探测的反应时显著长于同年龄对照组儿童,说明在加工复杂刺激时,汉语发展性阅读障碍儿童可能存在知觉加工迟缓的缺陷。但是,汉语发展性阅读障碍儿童并没有表现出扩散的视觉空间注意模式,即更多地注意外侧视野的信息。汉语发展性阅读障碍儿童的视觉空间注意模式与正常儿童相似,表现为随着视角的增加,正确率降低,反应时延长。     

Attentional modulation of perceptual comparison for feature binding

We investigated the neural correlates of attentional modulation in the perceptual comparison process for detecting feature-binding changes in an event-related functional magnetic resonance imaging (fMRI) experiment. Participants performed a variant of a cued change detection task. They viewed a memory array, a spatial retro-cue, and later a probe array. Their task was to judge whether the cued item had changed between the two arrays. Change type was manipulated to be a color-location binding or a color feature change. The retro-cue onset time in the retention interval was manipulated to be early or late. As a consequence of strong inter-item competition, we found strong prefrontal activation for late cues when contrasting the binding-change with the color-change condition. In contrast, we observed a comparable behavioral and neural effect between the two types of change detection when retro-cue was presented early. More importantly, we demonstrated a significant inter-regional correlation between the prefrontal and parietal regions in both binding- and color-change conditions for late cues. In addition, extensive prefrontal–parietal–visual functional connectivity was showed for detecting binding changes in the late-cueing condition. These results support the critical role in prefrontal–parietal–visual functional coupling for resolving strong inter-item competition during the comparison process in the binding-change condition. We provide direct evidence that attention modulates neural activity associated with perceptual comparison, biasing competition in favour of the task-relevant information in order to detect binding changes.     

Emotion regulation and amygdala-precuneus connectivity: Focusing on attentional deployment

Attentional deployment is an emotion regulation strategy that involves shifting attentional focus. Deploying attention to non-arousing, compared to arousing, regions of unpleasant images has been associated with reduced negative affect, reduced amygdala activation, and increased activity in fronto-parietal control networks. The current study examined neural correlates and functional connectivity associated with using attentional deployment to increase negative affect (deploying attention towards arousing unpleasant information) or to decrease negative affect (deploying attention away from arousing unpleasant information), compared to naturally viewing unpleasant images, in 42 individuals while concurrently monitoring eye movements. Directing attention to both arousing and non-arousing regions resulted in enhanced fronto-parietal activation compared to natural viewing, but only directing attention to non-arousing regions was associated with changes in amygdala activation. There were no significant differences in connectivity between naturally viewing unpleasant images and focusing on arousing regions. However, naturally viewing unpleasant images, relative to focusing on non-arousing regions, was associated with increased connectivity between the amygdala and visual cortex, while focusing on non-arousing regions of unpleasant images, compared to natural viewing, was associated with increased connectivity between the amygdala and the precuneus. Amygdala-precuneus connectivity correlated positively with eye-tracking measures of attentional deployment success and with trait reappraisal. Deploying attention away from arousing unpleasant information, then, may depend upon functional relationships between the amygdala and parietal regions implicated in attentional control. Furthermore, these relationships might relate to the ability to successfully implement attentional deployment, and the predisposition to utilize adaptive emotion regulation strategies.     

多目标追踪的神经机制

多目标追踪任务是研究动态场景中视觉注意加工机制常用的范式。自1998年开始对多目标追踪神经机制的影像学研究以来, 研究者采用ERP和fMRI等技术对多目标注意追踪所涉及的神经电生理活动和脑功能区激活方面开展了大量研究。ERP研究发现, 追踪过程持续的ERP脑电成分如N2pc、CDA的波幅与注意追踪负荷有关, 并且出现在目标与非目标上的探测刺激诱发的脑电成分如N1、P1波幅的差异可反映注意资源的分配, 具体为目标在追踪过程中得到了激活, 而非目标受到了抑制。fMRI研究比较一致地发现了顶叶(包括前顶内沟、后顶内沟、顶上小叶)、背外侧额叶皮层等在注意追踪中的强烈激活。其中顶内沟主要与注意负荷有关, 顶内沟的活动水平直接决定了观察者注意追踪的行为表现。而顶上小叶可能更多的负责注意转移。背外侧额叶皮层可能负责追踪时的感觉运动预测过程。     

Functional connectivity in an fMRI study of semantic and phonological processes and the effect of L-Dopa

We describe an fMRI experiment examining the functional connectivity (FC) between regions of the brain associated with semantic and phonological processing. We wished to explore whether L-Dopa administration affects the interaction between language network components in semantic and phonological categorization tasks, as revealed by FC. We hypothesized that L-Dopa would decrease FC due to restriction of the semantic network. During two test sessions (placebo and L-Dopa) each participant performed two fMRI runs, involving phonological and semantic processing. A number of brain regions commonly activated by the two tasks were chosen as regions if interest: left inferior frontal, left posterior temporal and left fusiform gyri, and left parietal cortex. FC was calculated and further analyzed for effects of either the drug or task. No main effect for drug was found. A significant main effect for task was found, with a greater average correlation for the phonological task than for the semantic task. These findings suggest that language areas are activated in a more synchronous manner for phonological than for semantic tasks. This may relate to the fact that phonological processes are mediated to a greater extent within language areas, whereas semantic tasks likely require greater interaction outside of the language areas. Alternatively, this may be due to differences in the attentional requirements of the two tasks.     

Dyslexia and visual-spatial talents: compensation vs deficit model

There are both theoretical and empirical reasons to support the hypothesis that dyslexia is associated with enhancement of right-hemisphere, visual-spatial skills. However, the neurological evidence is neutral with respect to whether dyslexic visual-spatial abilities should be superior (a compensation model) or inferior (a deficit model). In three studies we tested the hypothesis that dyslexia is associated with superior visual-spatial skills. Individuals with dyslexia not only failed to show superiority on a range of visual-spatial tasks, even when tasks were presented without time constraints, but also demonstrated a deficit on many tasks. Whereas we found attentional problems associated with dyslexia, these did not explain our findings. Results are discussed in terms of the apparent conflict between the failure to find any visual-spatial talent associated with dyslexia and the fact that dyslexia is overrepresented in certain visual-spatial professions.     

孤独症谱系障碍者视觉定向与视觉搜索的特点及神经机制

定向网络是注意网络的重要组成部分, 主要包括视觉定向与视觉搜索两大任务。对于这两大注意任务, 正常个体在神经机制上存在较大的重叠, 然而, 孤独症个体却表现出截然相反的行为证据。研究者从非社会信息的注意视角发现, 一般而言, 在视觉定向上, 孤独症个体注意转移不存在缺陷, 而注意脱离存在困难, 但该结论仍有争议; 在视觉搜索上, 孤独症个体存在视觉搜索优势, 但该优势发生的阶段及原因仍需进一步探究。未来研究应进一步考察孤独症个体在视觉定向任务中左右视野的不对称性、视觉搜索优势的内在机制及两大注意任务之间的相互关系。     

Do multielement visual tracking and visual search draw continuously on the same visual attention resources?

Multielement visual tracking and visual search are 2 tasks that are held to require visual-spatial attention. The authors used the attentional operating characteristic (AOC) method to determine whether both tasks draw continuously on the same attentional resource (i.e., whether the 2 tasks are mutually exclusive). The authors found that observers can search and track within the same trial significantly better than would be predicted if the 2 tasks were mutually exclusive. In fact, the AOC for tracking and search is similar to that for tracking and auditory monitoring. The results of additional experiments support an attention-switching account for this high level of dual-task performance in which a single attentional resource is efficiently switched between the tracking and search. The results provide important constraints for architectures of visual selective attention and the mechanisms of multielement tracking.     

Visual attention as a multilevel selection process

Natural visual scenes are cluttered and contain many different objects that cannot all be processed simultaneously. Therefore, attentional mechanisms are needed to select relevant and to filter out irrelevant information. Evidence from functional brain imaging reveals that attention operates at various processing levels within the visual system and beyond. First, the lateral geniculate nucleus appears to be the first stage in the processing of visual information that is modulated by attention, consistent with the idea that it may play an important role as an early gatekeeper in controlling neural gain. Second, areas at intermediate cortical-processing levels, such as V4 and TEO, appear to be important sites at which attention filters out unwanted information by means of receptive field mechanisms. Third, the attention mechanisms that operate in the visual system appear to be controlled by a distributed network of higher order areas in the frontal and parietal cortex, which generate top-down signals that are transmitted via feedback connections to the visual system. And fourth, the pulvinar of the thalamus may operate by integrating and coordinating attentional functions in concert with the fronto-parietal network, although much needs to be learned about its functional properties. The overall view that emerges from the studies reviewed in this article is that neural mechanisms of selective attention operate at multiple stages in the visual system and beyond and are determined by the visual processing capabilities of each stage. In this respect, attention can be considered in terms of a multilevel selection process.     

The neural circuitry supporting goal maintenance during cognitive control: a comparison of expectancy AX-CPT and dot probe expectancy paradigms

Goal maintenance is an aspect of cognitive control that has been identified as critical for understanding psychopathology according to criteria of the NIMH-sponsored CNTRICS (Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia) and Research Domain Criteria (RDoC) initiatives. CNTRICS proposed the expectancy AX-CPT, and its visual-spatial parallel the dot probe expectancy (DPX), as valid measures of the cognitive and neural processes thought to be relevant for goal maintenance. The goal of this study was to specifically examine the functional neural correlates and connectivity patterns of both goal maintenance tasks in the same subset of subjects to further validate their neural construct validity and clarify our understanding of the nature and function of the neural circuitry engaged by the tasks. Twenty-six healthy control subjects performed both the letter (AX) and dot pattern (DPX) variants of the CPT during fMRI. Behavioral performance was similar between tasks. The 2 tasks engaged the same brain networks including dorsolateral prefrontal cortex (DLPFC) and dorsal parietal regions, supporting their validity as complementary measures of the goal maintenance construct. Interestingly there was greater engagement of the frontal opercular insula region during the expectancy AX-CPT (letter) and greater functional connectivity between the PFC and medial temporal lobe in the DPX (dot pattern). These differences are consistent with differential recruitment of phonological and visual-spatial processes by the two tasks and suggest that additional long-term memory systems may be engaged by the dot probe version.