Semantic processing of living and nonliving concepts across the cerebral hemispheres

Studies of patients with category-specific semantic deficits suggest that the right and left cerebral hemispheres may be differently involved in the processing of living and nonliving domains concepts. In this study, we investigate whether there are hemisphere differences in the semantic processing of these domains in healthy volunteers. Based on the neuropsychological findings, we predicted a disadvantage for nonliving compared to living concepts in the right hemisphere. Our prediction was supported, in that semantic decisions to nonliving concepts were significantly slower and more error-prone when presented to the right hemisphere. In contrast there were no hemisphere differences for living concepts. These findings are consistent with either differential representation or processing of concepts across right and left hemispheres. However, we also found a disadvantage for nonliving things compared to living things in the left hemisphere, which is not consistent with a simple representation account. We discuss these findings in terms of qualitatively different semantic processing in right and left hemispheres within the framework of a distributed model of conceptual representation.     

Attentional balance and intelligence

Recent studies of neuroimaging during cognitive tasks suggest that most tasks involve the activity of widespread areas in both cerebral hemispheres. In many cases, information must be shared between the two hemispheres. The coordination of these areas involves the brain's attentional networks. Unilateral brain damage often causes asymmetries in attention and reduced speed of processing. Based on these findings it was hypothesized that mental processing in normals will be more efficient when normal people can shift attention to either hemisphere with equal efficiency. Attentional balance was measured by the degree of asymmetry found during the covert visual-orienting task. Intelligence was measured by the Raven Standard Progressive Matrices. Data from two experiments suggest that low asymmetry in attention shifting is associated with higher intelligence.     

数字加工的认知神经基础

数学作为人类最重要的发明,越来越引起认知神经科学家的重视与关注,究竟什么才是人类数学知识的脑基础？脑成像的研究已经证实了一个参与数学运算加工的神经网络,包括顶叶皮质、侧前额叶皮质、内前额叶皮质、和小脑。实验证明：人脑对于数字具有一种模拟表达,类似于将数量在脑内部作为一种内心的数字线上的点来操作。神经心理学的研究证实数字加工的这种数量表达分布于两半球,其优势区位于下顶叶皮质区。     

Gender differences in the recognition of laterally presented affective nouns

Evidence suggests that the cerebral hemispheres are differentially specialised for the processing of positively and negatively valenced affective material. The present study examined the consequences of this for the availability in each hemisphere of lexical entries related to positive, neutral, and negative affect. A threshold recognition task was used to assess the identification of positive, neutral, and negative emotionally toned nouns projected to the right or left visual field. A strong lateral asymmetry in favour of right visual field recognition of nouns was observed. Whereas women showed no evidence of changes in lateral asymmetry as a function of affect, lateral asymmetry in men was significantly greater for positive nouns. This finding points to a difference in the representation of affective material in the left and right lexicons of the male brain, and provides support for the notion that gender may be one of the keys to reconciling some of the contradictory findings that characterise this area of research.     

汉语加工脑神经机制研究的新进展

随着脑科学研究手段的改进．人们对汉语加工的脑神经机制有了更多、更深入的了解。大量研究表明,汉语加工有不同于拼音语言加工的脑机制,在加工汉语时．激活的脑区和在加工拼音语言时激活的脑区不同．母语为汉语的人和母语为拼音语言的人在脑的形态结构上也存在显著差异。对汉语加工脑机制的研究有利于对音素和音节加工的皮层表征的分离,有助于揭示语言加工脑机制的普遍性和特殊性。     

Hemispheric differences in indexical specificity effects in spoken word recognition

Variability in talker identity, one type of indexical variation, has demonstrable effects on the speed and accuracy of spoken word recognition. Furthermore, neuropsychological evidence suggests that indexical and linguistic information may be represented and processed differently in the 2 cerebral hemispheres, and is consistent with findings from the visual domain. For example, in visual word recognition, changes in font affect processing differently depending on which hemisphere initially processes the input. The present study examined whether hemispheric differences exist in spoken language as well. In 4 long-term repetition-priming experiments, the authors examined responses to stimuli that were primed by stimuli that matched or mismatched in talker identity. The results demonstrate that indexical variability can affect participants' perception of spoken words differently in the 2 hemispheres.     

胼胝体调节大脑两半球相互作用的机制

胼胝体是哺乳动物脑内最大的白质结构,不仅可以在大脑两半球间传递信息,也能调节半球间的相互作用,“抑制模型”和“兴奋模型”是当前解释胼胝体调节机制的主要模型.前者假设,胼胝体对半球间的信息传递起抑制作用,表现为优势半球的功能增强,非优势半球的活动抑制,因而可以提高半球加工的独立性和功能不对称性;后者则认为,胼胝体对半球间信息传递起促进作用,导致两半球同时性活动,并增强其功能连接性,因而可以降低半球的功能不对称性,有利于半球间的信息共享与功能整合.近期的研究显示,胼胝体并不是一个结构与功能的单一体,而是包含了在空间与时间上既分离又互动的多通道信息加工复合体.抑制与兴奋信息可以通过胼胝体的不同空间通道以不同的速度在半球间进行传递,并受到任务计算类型与复杂性的调节,因此,胼胝体的抑制与兴奋的协同可以调节两半球的动态相互作用.     

惯用语理解的多种心理机制：不同的证据

惯用语的理解机制一直是心理语言学研究的热点问题。来自语言学和神经生理学的证据都表明,对惯用语的加工存在多样化趋势,而且加工策略和手段会随个体卷入社会生活的程度而变化。惯用语的加工受加工者自身的隐喻知识以及惯用语本身性质的影响。另外,惯用语加工激活的脑区表明句法和语义分析在惯用语理解中均发挥重要作用,惯用语并没有词汇化,但是不能使用统一的加工模型来整合惯用语的理解机制。惯用语自身性质的多样化导致惯用语理解的多种心理机制。     

Hemisphere-specific effects in word recognition do not require hemisphere-specific modes of access

Consistent with converging experimental evidence, we assume that foveal information is initially split across the two cerebral hemispheres. We have previously presented the SERIOL model of letter-position coding, which specifies how the resulting two halves of a letter string are integrated into an abstract representation of letter order. This representation is based on ordered pairs of two letters (bigrams); such a representation is created for input occurring at any location in the visual field. Various studies have shown hemisphere-specific effects in lexical access by using unilateral presentation of stimuli. While the hemisphere-independent means of lexical access in the SERIOL model (via bigrams) may seem inconsistent with these findings, we propose that such effects arise from the hemisphere-specific transformations necessary to create the bigram representation. We provide a theoretical account of the finding that high N (lexical neighborhood size) evokes facilitation in the RH, but not the LH (Lavidor & Ellis, 2002a, 2002b); an experiment discussed elsewhere (Whitney & Lavidor, 2003) has verified key predictions of this account. We also discuss the differing effects of word length across visual fields.     

Double take: parallel processing by the cerebral hemispheres reduces attentional blink

Recent data have shown that parallel processing by the cerebral hemispheres can expand the capacity of visual working memory for spatial locations (J. F. Delvenne, 2005) and attentional tracking (G. A. Alvarez & P. Cavanagh, 2005). Evidence that parallel processing by the cerebral hemispheres can improve item identification has remained elusive. The authors used a novel variant of the attentional blink paradigm to show that the attentional blink is reduced if targets are divided between the hemispheres rather than directed to a single hemisphere. Parallel processing by the cerebral hemispheres can thus expand the capacity of processes involved in item identification. The authors also show that prior engagement of the attentional system may compromise the processing of items directed to the right visual field. This pseudoextinction may explain the failures of previous attempts to demonstrate that parallel processing can improve item identification (J. F. Delvenne, 2005; S. J. Luck, S. A. Hillyard, G. R. Mangun, & M. S. Gazzaniga, 1989).     

大脑腹侧视觉通路知觉表征神经机制研究

大脑腹侧视觉通路知觉表征的神经机制是认知神经科学研究面临的基本问题。本文系统介绍了该问题研究中比较有影响力的理论模型,归纳分析了模型之间的分歧与各自的局限。文章分析指出大脑自上而下的调控机制是腹侧视觉通路神经表征机制问题研究的另一重要维度,如何有效整合知觉表征模型与大脑调控机制的相关研究是进一步深化知觉表征神经机制问题研究的关键。     

Cerebral Organization of Motor Imagery: Contralateral Control of Grip Selection in Mentally Represented Prehension

The principle of contralateral organization of the visual and motor systems was exploited to investigate contributions of the cerebral hemispheres to the mental representation of prehension in healthy, right-handed human subjects. Graphically rendered dowels were presented to either the left or right visual field in a variety of different orientations, and times to determine whether an underhand or overhand grip would be preferred for engaging these stimuli were measured. Although no actual reaching movements were performed, a significant advantage in grip-selection time was found when information was presented to the cerebral hemisphere contralateral to the designated response hand. Results are consistent with the position that motor imagery recruits neurocognitive mechanisms involved in movement planning. More precisely, these findings indicate that processes within each cerebral hemisphere participate in mentally representing object-oriented actions of the contralateral hand.     

Disentangling narrow and coarse semantic networks in the brain: The role of computational models of word meaning

There has been a recent boom in research relating semantic space computational models to fMRI data, in an effort to better understand how the brain represents semantic information. In the first study reported here, we expanded on a previous study to examine how different semantic space models and modeling parameters affect the abilities of these computational models to predict brain activation in a data-driven set of 500 selected voxels. The findings suggest that these computational models may contain distinct types of semantic information that relate to different brain areas in different ways. On the basis of these findings, in a second study we conducted an additional exploratory analysis of theoretically motivated brain regions in the language network. We demonstrated that data-driven computational models can be successfully integrated into theoretical frameworks to inform and test theories of semantic representation and processing. The findings from our work are discussed in light of future directions for neuroimaging and computational research.     

Perceptual categorization in the cerebral hemispheres

The suggestion of a functional hemispheric dissociation in performing perceptual categorization was examined in two tachistoscopic experiments with normal adults. Subjects were required to match physically identical or similar, but nonidentical, pictures of animals. The first experiment showed no hemispheric difference and indicated that both hemispheres could resort to two different types of categorization process as a function of the simultaneous or delayed mode of presentation of the stimuli. In the second experiment, the viewing conditions were manipulated so as to afford a reduced amount of stimulus energy, and a significant left-visual-field advantage was then obtained. The results are discussed with respect to models of information processing in the cerebral hemispheres, and in relation to impairments in object recognition following brain damage.     

Functional Neuroimaging Correlates of Functional Amnesia

Especially in the field of memory encoding and retrieval, the results of functional neuroimaging have provided new insights in anatomico-functional interactions. In particular this holds true for the role of the prefrontal cortex in mnestic information processing, for the contribution and participation of the two hemispheres in various processes of information transmission, and for views on disturbed information processing after organically obvious and so-called psychogenic forms of memory impairments. This report particularly stresses the insights obtained by functional neuroimaging for probably environmentally triggered deficiencies in memory processing and discusses possible subtle neuroanatomical correlates of functional amnesias. It is especially emphasised that stress conditions and depressive states may modify the release of steroids (glucocorticoids) and transmitter agonists at the brain level with the consequence of selective memory disturbances which may manifest as a ‘mnestic block syndrome’.     

Functional neuroimaging correlates of functional amnesia

Especially in the field of memory encoding and retrieval, the results of functional neuroimaging have provided new insights in anatomico-functional interactions. In particular this holds true for the role of the prefrontal cortex in mnestic information processing, for the contribution and participation of the two hemispheres in various processes of information transmission, and for views on disturbed information processing after organically obvious and so-called psychogenic forms of memory impairments. This report particularly stresses the insights obtained by functional neuroimaging for probably environmentally triggered deficiencies in memory processing and discusses possible subtle neuroanatomical correlates of functional amnesias. It is especially emphasised that stress conditions and depressive states may modify the release of steroids (glucocorticoids) and transmitter agonists at the brain level with the consequence of selective memory disturbances which may manifest as a "mnestic block syndrome".     

Multiple resources and brain laterality

Two studies tested the multiple resources model of information processing using tachistoscopically lateralized input. In Exp. 1 37 normal, dextral subjects, 18 men aged 18/21 yr. and 19 women aged 18/22 yr. responded manually to a visuo-spatial and verbal dual-task presented simultaneously to left and right brain or nonlaterally. Both men and women tended to have superior performance with coherent lateral input, however, differences in task difficulty and the possibility of a left-to-right scanning advantage with lateral input made interpretation of the data tenuous. In Exp. 2 the difficulty of the two tasks was more equal and a third viewing condition, having noncoherent lateral input, was included. Normal, dextral subjects, 10 men aged 18/21 yr. and 10 women aged 19/21 yr. were tested under all three viewing conditions. Both men and women had superior performance with coherent lateral input compared to the other two conditions. The results led to speculations that each hemisphere has unique pools of resources, that the resources of one or both hemispheres may be functional in processing a given task, and that in dual-task situations the brain operates most efficiently and accurately with direct access of appropriate tasks to each hemisphere.     

Role of the parietal cortex in long-term representation of spatial information in the rat

The processing of spatial information in the brain requires a network of structures within which the hippocampus plays a prominent role by elaborating an allocentric representation of space. The parietal cortex has long been suggested to have a complementary function. An overview of lesion and unit recording data in the rat indicates that the parietal cortex is involved in different aspects of spatial information processing including allocentric and egocentric processing. More specifically, the data suggest that the parietal cortex plays a fundamental role in combining visual and motion information, a process that would be important for an egocentric-to-allocentric transformation process. Furthermore, the parietal cortex may also have a role in the long-term storage of representation although this possibility needs further evidence. The data overall show that the parietal cortex occupies a unique position in the brain at the interface of perception and representation.