腹侧通路与背侧通路在词汇阅读中的作用

腹侧通路与背侧通路是视觉加工的两条通路。随着认知神经科学的发展,研究发现腹侧和背侧通路与词汇阅读有关。其中腹侧通路与词汇识别有关,背侧通路与阅读的关系比较复杂。本文简要回顾了两条通路在词汇阅读中的作用。     

羽毛球运动重塑成年早期的大脑灰质和白质结构

以往研究发现, 球类运动员视知觉脑区的结构不同于非运动员, 但这些脑区结构的差异是训练经历引起还是天生结构不同所导致的, 尚未可知。本研究拟采用纵向设计, 以处于成年早期的成人非运动员为被试(23~27岁), 随机分成实验组和对照组, 实验组参加12周的羽毛球运动训练, 对照组在此期间不进行任何有规律的运动训练, 采集干预实验前后所有被试的结构像和弥散张量成像数据。结果发现, 实验组训练后左下枕叶、颞中回、颞下回灰质体积增加, 双侧内囊后肢、上放射冠各向异性分数(FA)增加, 进一步分析发现, FA增加的原因是径向扩散系数(RD)下降。提示羽毛球运动可增加成人与视运动知觉有关脑区的灰质容量, 增加纤维束的髓鞘厚度。     

汉语发展性阅读障碍儿童的视觉大细胞-背侧通路功能

发展性阅读障碍是一种在获得阅读技能方面的特殊困难,其致病原因一直是该领域的核心问题。越来越多的研究表明视觉大细胞-背侧通路功能与阅读技能之间存在紧密联系。视觉大细胞-背侧通路缺陷可能是导致阅读障碍的主要原因之一。一些研究发现汉语阅读障碍儿童同样存在视觉大细胞-背侧通路缺陷。本文将回顾近些年汉语发展性阅读障碍儿童视觉大细胞-背侧通路功能的相关研究成果,并对该领域未来的发展方向做出展望。     

汉语声调认知加工的脑机制及语言经验的影响

汉语母语者对汉语声调的认知加工可分为亚词汇和词汇两种加工水平。亚词汇水平涉及对汉语声调的声学和语音加工,当无需主动注意参与时,现有研究在左右半球优势上尚未取得明确结论;当需要主动注意参与时,优势主要表现为左侧化,涉及左侧的布洛卡区、前运动区、前部脑岛、顶叶、顶枕联合区以及双侧听皮层附近脑区,这与语言加工双通路模型(HickokPoeppel,2007)中的背侧通路有很大重合。词汇水平涉及对汉语声调的识别,由双侧半球参与,顶叶、颞叶等部分脑区左侧优势更加明显,同时涉及颞中回等语言加工腹侧通路的核心区域。此外,个体对汉语声调认知加工的脑机制会受到语言经验的影响。     

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。     

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。     

加工需求驱动下词汇阅读神经通路的动态协作机制

建构统一的认知和神经生理模型是词汇阅读认知神经科学研究面临的核心问题。阅读的认知理论模型一致认为阅读是语音和语义加工通路分工协作的结果,认知神经科学研究也表明词汇阅读是背侧和腹侧神经通路动态协作的结果。为了系统地阐述阅读网络的这种动态协作机制,结合神经功能和生理基础两个层面,从以下三个方面对最新研究进展进行系统疏理：首先,指出潜在的加工需求是背/腹侧神经通路动态协作的实质;然后进一步阐明潜在加工需求驱动了不同正字法深度下背/腹侧神经通路的分工合作模式;最后,深入剖析了潜在加工如何通过语言经验塑造了神经通路间的动态协作。从而揭示出阅读神经通路动态协作的实质可能是特定任务下加工需求驱动的结果,这种动态协作可能成为跨语言普遍的词汇阅读理论模型。     

可操作物体识别过程中的两种操作动作表征

已有大量研究表明, 视觉背侧通路中的背侧−背侧通路和腹侧−背侧通路分别表征与物体相关的抓握和使用动作, 形成结构性和功能性操作动作表征。这两种操作动作表征在神经基础、激活条件、时间进程, 以及与长时记忆的联系方面都存在差异, 并且共同参与到可操作物体的识别过程中。关于结构性和功能性操作动作表征的研究不仅证明了操作动作信息对于可操作物体识别的重要性, 而且对于深入研究物体如何在大脑中表征具有重要意义。     

左侧角回在词汇语义加工中的作用

大脑左侧角回是语言认知神经科学研究发现的一个重要语义加工脑区。该脑区在词汇语义加工中的具体功能还没有得到统一的认识,成为研究者广泛关注的热点和焦点问题。结构上,角回位于颞叶、枕叶和顶叶交接区,并且具有广泛的白质纤维束连接,这决定了它可能具有跨区域信息整合的功能。它在高水平语义表征、模态和特征信息联合表征、语义关系表征以及语义整合加工中参与激活,可能是语义表征和加工的信息“聚合区”。然而,左侧角回在语义表征枢纽、语义执行控制加工、默认模式网络的语义加工三方面还存在功能争论,未来研究需要综合考虑左侧角回的解剖结构基础及其与广泛脑区连接的特点,对角回子区域的功能进行深入细致地探讨。     

多巴胺系统基因对注意网络的调控作用

多巴胺是脑内重要的神经递质之一,与注意活动紧密相关。本文选取作用于突触前膜、间隙和后膜的多巴胺系统基因——多巴胺转运蛋白基因、儿茶酚氧化甲基转移酶基因和多巴胺受体基因,整合影像遗传学研究,探讨多巴胺基因对注意网络的调控。元分析发现背侧和腹侧注意网络的主要脑区均有较大的基因调控效应,且腹侧网络的效应值显著大于背侧网络,表明多巴胺系统基因在全脑范围内调控注意网络,且对腹侧网络的调控作用更强于背侧网络。     

DEVELOPMENTAL SEX DIFFERENCES IN THE RELATION OF NEUROANATOMICAL CONNECTIVITY TO INTELLIGENCE

Recent neuroimaging research has shown sex-related differences in the relationship between brain structure and cognitive function. Anatomical studies have shown a greater reliance for cognitive function on white matter structure in adult females, and a greater reliance on gray matter structure in adult males. Functional neuroimaging studies have also shown a greater correlation between brain connectivity and cognitive function in females. However, this relationship is not present in young childhood (5 years old) but appears during the developmental period. Here sex differences in structure–function relationships and their developmental trajectory are investigated using diffusion tensor imaging (DTI) on a large cohort of over 100 normal children ages 5–18. Significant sex–X–IQ interactions on fractional anisotropy (FA), a marker for white matter organization, were seen in the left frontal lobe, in fronto-parietal areas bilaterally, and in the arcuate fasciculus bilaterally, with girls showing positive correlations of FA with IQ, and boys showing a negative correlation. Significant sex–X–IQ–X–age interactions on FA were also seen in the left frontal lobe and in fronto-parietal areas bilaterally, showing a developmental effect. These results strongly corroborate previous findings regarding sex differences in structure–function relationships regarding intelligence. Results also indicate that a naïve interpretation of “more is better” with respect to FA may not be accurate, especially in adult males.     

Frontotemporal neural systems supporting semantic processing in Alzheimer’s disease

We hypothesized that semantic memory for object concepts involves both representations of visual feature knowledge in modality-specific association cortex and heteromodal regions that are important for integrating and organizing this semantic knowledge so that it can be used in a flexible, contextually appropriate manner. We examined this hypothesis in an fMRI study of mild Alzheimer’s disease (AD). Participants were presented with pairs of printed words and asked whether the words matched on a given visual–perceptual feature (e.g., guitar, violin: SHAPE). The stimuli probed natural kinds and manufactured objects, and the judgments involved shape or color. We found activation of bilateral ventral temporal cortex and left dorsolateral prefrontal cortex during semantic judgments, with AD patients showing less activation of these regions than healthy seniors. Moreover, AD patients showed less ventral temporal activation than did healthy seniors for manufactured objects, but not for natural kinds. We also used diffusion-weighted MRI of white matter to examine fractional anisotropy (FA). Patients with AD showed significantly reduced FA in the superior longitudinal fasciculus and inferior frontal-occipital fasciculus, which carry projections linking temporal and frontal regions of this semantic network. Our results are consistent with the hypothesis that semantic memory is supported in part by a large-scale neural network involving modality-specific association cortex, heteromodal association cortex, and projections between these regions. The semantic deficit in AD thus arises from gray matter disease that affects the representation of feature knowledge and processing its content, as well as white matter disease that interrupts the integrated functioning of this large-scale network.     

Altered lateralization of dorsal language tracts in 6‐week‐old infants at risk for autism

Altered structural connectivity has been identified as a possible biomarker of autism spectrum disorder (ASD) risk in the developing brain. Core features of ASD include impaired social communication and early language delay. Thus, examining white matter tracts associated with language may lend further insight into early signs of ASD risk and the mechanisms that underlie language impairments associated with the disorder. Evidence of altered structural connectivity has previously been detected in 6‐month‐old infants at high familial risk for developing ASD. However, as language processing begins in utero, differences in structural connectivity between language regions may be present in the early infant brain shortly after birth. Here we investigated key white matter pathways of the dorsal language network in 6‐week‐old infants at high (HR) and low (LR) risk for ASD to identify atypicalities in structural connectivity that may predict altered developmental trajectories prior to overt language delays and the onset of ASD symptomatology. Compared to HR infants, LR infants showed higher fractional anisotropy (FA) in the left superior longitudinal fasciculus (SLF); in contrast, in the right SLF, HR infants showed higher FA than LR infants. Additionally, HR infants showed more rightward lateralization of the SLF. Across both groups, measures of FA and lateralization of these pathways at 6 weeks of age were related to later language development at 18 months of age as well as ASD symptomatology at 36 months of age. These findings indicate that early differences in the structure of language pathways may provide an early predictor of future language development and ASD risk.     

Skilled anticipation in real-world tasks: measurement of attentional demands in the domain of tennis

Anticipatory skills are characteristic of expert performance in a range of dynamic domains. However, models of the processes underlying such skilled anticipation remain limited. This study describes the construction and validation of a video-based test of anticipation in tennis and examined whether video test performance is less attentionally demanding for expert tennis players than for novices. Expert players performed the anticipation test more effectively than novices and were less vulnerable to dual-task decrement. This article discusses these findings in relation to models of skilled anticipation. The video test could be used for both selection and identification of training needs.     

Pure optic ataxia and visual hemiagnosia – extending the dual visual hypothesis

Goodale and Milner's two visual system hypothesis is an influential model for the understanding of the primate visual system. Lesions of either the ventral (occipito‐temporal) or the dorsal (occipito‐parietal) stream produce distinct and dissociated syndromes in humans: visual agnosia is typical for ventral damage, whereas optic ataxia (OA) for dorsal damage. We studied the case of a 59‐year‐old left‐handed woman with a circumscribed lesion around the left posterior occipital sulcus, extending to the underlying white matter. Initially, she presented with a central visual field OA, which regressed to an OA to the right visual hemifield during the 3 months observation period. In addition, tachistoscopic experiments showed visual hemiagnosia to the right visual hemifield. In line with the findings of the neuropsychological experiments, the analysis of the structural MR data by means of a trackwise hodologic probabilistic approach revealed damage to the left superior longitudinal fasciculus and to the left inferior longitudinal fasciculus, indicating an impairment of both the dorsal and the ventral stream. The combination of OA and visual hemiagnosia in the same patient has never been previously described. The present case study thus provides further insights for the understanding of visual processing.     

The advantage of being left-handed in interactive sports

As compared with their prevalence in the general population, left-handers are overrepresented in the expert domain of many interactive sports. This study examined to what extent this is due to negative perceptual frequency effects—that is, whether the greater frequency of tennis matches with right-handed opponents makes it possible to discriminate the stroke movements of right-handed players more precisely. Fifty-four right-handed and 54 left-handed males in three equal-sized groups of varying levels of tennis expertise (national league experts, local league intermediates, and novices) completed a tennis anticipation test in which they had to predict the subsequent direction of an opponent’s temporally occluded tennis strokes on a computer screen. The results showed that all three groups were better at predicting the direction of strokes by right-handed players. This supports the hypothesis that the overrepresentation of left-handers in the expert domain is partly due to perceptual frequency effects.     

White matter development during adolescence as shown by diffusion MRI

Previous volumetric developmental MRI studies of the brain have shown white matter development continuing through adolescence and into adulthood. This review presents current findings regarding white matter development and organization from diffusion MRI studies. The general trend during adolescence (age 12–18 years) is towards increasing fractional anisotropy (FA) with age and decreasing mean diffusivity (MD) with age, findings primarily due to decreasing radial diffusivity with age. However, results of studies vary as to the regional specificity of such age-related changes, likely due in part to methodological issues. Another general trend is for FA to positively correlate and MD to negatively correlate with cognitive function. This trend is however region-specific, task-specific, and population-specific; some studies have in fact found negative correlations of FA and positive correlations of MD in specific regions with specific measures of cognitive performance. There are also published reports of sexual dimorphism in white matter development, indicating differing developmental trajectories between males and females as well as differing relationships developmentally between white matter architecture and cognitive function. There is a need for more research to further elucidate the development of white matter and its relation to cognitive function during this critical developmental period.     

Sex differences in the IQ-white matter microstructure relationship: A DTI study

Sex differences in the relationship between general intelligence and brain structure are a topic of increasing research interest. Early studies focused mainly on gray and white matter differences using voxel-based morphometry, while more recent studies investigated neural fiber tracts using diffusion tensor imaging (DTI) to analyze the white matter microstructure. In this study we used tract-based spatial statistics (TBSS) on DTI to test how intelligence is associated with brain diffusion indices and to see whether this relationship differs between men and women. 63 Men and women divided into groups of lower and higher intelligence were selected. Whole-brain DTI scans were analyzed using TBSS calculating maps of fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD). The results reveal that the white matter microstructure differs between individuals as a function of intelligence and sex. In men, higher intelligence was related to higher FA and lower RD in the corpus callosum. In women, in contrast, intelligence was not related to the white matter microstructure. The higher values of FA and lower values of RD suggest that intelligence is associated with higher myelination and/or a higher number of axons particularly in men. This microstructural difference in the corpus callosum may increase cognitive functioning by reducing inter-hemispheric transfer time and thus account for more efficient brain functioning in men.     

Anticipation skill in a real-world task: measurement,training, and transfer in tennis

Anticipation skill in tennis was examined using realistic film simulations, movement-based response measures, and a portable eye movement recording system. Skilled players were faster than their less skilled counterparts in anticipating the direction of opponents' tennis strokes, with this superior performance being based, at least in part, on more effective visual search behaviors. The processes mediating superior performance were then modeled in groups of recreational tennis players using video simulation, instruction, and feedback. Players who received perceptual training improved their performance on laboratory- and field-based tests of anticipation when compared with matched placebo and control groups that did not receive any instruction regarding expert performance strategies. The approach used may have practical utility in a variety of performance contexts.     

Course-of-action theory in table tennis: a qualitative analysis of the knowledge used by three elite players during matches

The course-of-action theory (J. Theureau, Le Cours d'action: Analyse Sémiologique, 1992) provided the framework for this study, which described how expert table tennis players' mobilized knowledge in relation with their mode of involvement (exploratory and executory). Matches were videotaped during international meets and the verbalizations of the players as they viewed the tapes were collected a posteriori. The data were processed by transcribing the players' actions and verbalizations, decomposing their activity into elementary units of meaning, labeling the constituents of these units, identifying typical exploratory and executory sequences. The results showed that the knowledge mobilized by the players during the matches differed with their mode of involvement. Knowledge was continuously put into relationship with significant elements in the unfolding situation in order to create interpretive chains, and this contributed to building a meaningful world for the players. The players' cognitive activity was thus revealed to be a permanent construction of meaning aimed at reducing uncertainty in situations of competitive interaction.