On the determination of defect dipoles from atomistic simulations using periodic boundary conditions

By solving the problem of a periodic distribution of point defects in general anisotropic media, we give an alternative, more direct proof, of the relatively recent procedure that extracts dipole tensors from the stress acting on the cell of atomistic simulations performed under periodic boundary conditions. Moreover, we show that naive superposition of individual defect fields is not a solution of the problem, though correction terms can be identified; as a byproduct, analysis of the latter allows us to reveal a spurious contribution to the elastic interaction energy as calculated in current literature procedures, that therefore must be subtracted in order to obtain correct results.     

Neural functional organization of hallucinations in schizophrenia: Multisensory dissolution of pathological emergence in consciousness

Although complex hallucinations are extremely vivid, painful symptoms in schizophrenia, little is known about the underlying mechanisms of multisensory integration in such a phenomenon. We investigated the neural basis of these altered states of consciousness in a patient with schizophrenia, by combining state of the art neuroscientific exploratory methods like functional MRI, diffusion tensor imaging, cortical thickness analysis, electrical source reconstruction and trans-cranial magnetic stimulation. The results shed light on the functional architecture of the hallucinatory processes, in which unimodal information from different modalities is strongly functionally connected to higher-order integrative areas.     

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.     

扩散张量成像在弱视中应用的探讨

弱视是儿童常见眼科疾病,发病机制目前尚不完全清楚。扩散张量成像（diffusion tensor imaging,DTI）是MRI技术的一个新应用,将DTI引入弱视发病机制的研究使人们能更加直观地研究弱视患者视路相关结构有否解剖改变。正确运用哲学观点、充分发挥创新能力并灵活选用适宜技术与高新技术以期达到弱视诊断的最优化。     

Brain MR kurtosis imaging study: Contrasting gray and white matter

This paper mainly focuses on characterization of different brain tissues such as White and Gray matter (WM and GM) using the relation between Diffusion Tensor Imaging and Diffusion Kurtosis Imaging parameters. Both Diffusion Tensor Imaging and Diffusion Kurtosis Imaging are the extension of Diffusion Weighted Imaging, which are widely applied for analysing micro fibre structure of human organs non-invasively. Diffusion Tensor Imaging assumes that the water diffusion is in Gaussian nature and Diffusion Kurtosis Imaging accounts the deviation of the Gaussian nature. This study, conducted a correlation and regression analysis between different parametric maps generated from Diffusion Kurtosis Images. For this we have chosen 200 regions of interest pixels drawn from brain MRIs. From the results, it is observed that there is a significant variation in the correlation results between Axial Diffusion and Kurtosis Fractional Anisotropy maps of Gray matter and White matter tissues. This can be employed for enhancing accuracy in MRI segmentation techniques and also as a potential tool for Neuro degenerative disease detection.     

An ecological analysis of knowing by wielding.

The ecological approach to perception, as developed by James Gibson, is described and applied to how one knows, by means of the haptic perceptual system, various properties of hand-held objects. Four sets of experiments are reviewed in which subjects reported on the extent, orientation, shape, and fractional components of unseen objects wielded freely. For each task, an invariant specific to the object property in question is identified in the structured arrays of rotational moments and strains produced by the act of wielding. Results are discussed in relation to the concepts of attention and stimulation, as reformulated by the ecological approach, and the general theory of perception as information pickup.     

Executive function in paediatric medulloblastoma: The role of cerebrocerebellar connections

Executive functions (EFs) are involved in the attainment, maintenance, and integration of information; these functions may play a key role in cognitive and behavioural outcomes in children treated for medulloblastoma (MB). At present, it remains unclear which EFs are most sensitive to the treatment effects for MB and whether damage to cerebrocerebellar circuitry is associated with EF. We completed a comprehensive evaluation of EF in 24 children treated for MB and 20 age‐matched healthy children (HC) and distilled these measures into components. Six components (C1–C6) were extracted from our model, reflecting dissociable constructs of EF: C1 = cognitive efficiency; C2 = planning/problem‐solving; C3 = positive cognitive emotion regulation; C4 = working memory; C5 = negative cognitive emotion regulation; and C6 = mixed cognitive emotion regulation. Group differences were found for C1, C2, C3, and C4; the MB group showed poorer performance on EF tasks and made less use of positive cognitive emotion regulation strategies relative to HC. Compromise to cerebrocerebellar microstructure – cerebro‐ponto‐cerebellar and cerebello‐thalamo‐cerebral pathways – was evident in children treated for MB compared to HC. We found that cerebrocerebellar circuitry has a mediating effect on one component of EF following treatment for MB – working memory.     

弥散张量成像在语言认知神经科学研究中的应用

人类的语言功能不仅仅基于以额叶、颞叶为代表的语言脑区灰质皮层的激活, 更重要的是基于这些脑区之间白质纤维束的连接。随着各种脑成像技术的逐渐成熟, 基于核磁共振的弥散张量成像技术在语言认知领域展现出越来越重要的作用。弥散张量成像在语言认知研究上的应用, 可以将其与行为测查、功能定位成像、功能连接、全脑网络等多种分析方法结合来共同研究语言认知, 进而从脑结构的角度来探究语言与脑的关系。     

Assume a Spherical Chicken: Analytic Constraints,Inertia Tensor Information,and Wielded Rod Length Perception

Information associated with the inertia tensor is the preeminent explanation for haptic perception of object properties, notably wielded rod length. Critics counter that tensorial-based information requires non-tensorial supplementation (mass, torque). However, those critiques omit important constraints. With relevant constraints included, the inertia tensor alone completely specifies rod length. I list constraints inherent (but tacit) in haptic rod length perception, and show that object properties associated with the inertia tensor are invariant, even with constraints removed, by involving (a) longitudinal moment equivalents for rod mass and (b) derivatives of moments with respect to varying rotation axes. Analytic outcomes show tensorial-based information is a robust basis for wielded rod length perception, and suggest open questions for empirical exploration.