Effects of stimulus spatial frequency,size, and luminance contrast on orientation tuning of neurons in the dorsal lateral geniculate nucleus of cat

It is generally thought that orientation selectivity first appears in the primary visual cortex (V1), whereas neurons in the lateral geniculate nucleus (LGN), an input source for V1, are thought to be insensitive to stimulus orientation. Here we show that increasing both the spatial frequency and size of the grating stimuli beyond their respective optimal values strongly enhance the orientation tuning of LGN neurons. The resulting orientation tuning was clearly contrast-invariant. Furthermore, blocking intrathalamic inhibition by iontophoretically administering γ-aminobutyric acid (GABA)_A receptor antagonists, such as bicuculline and GABAzine, slightly but significantly weakened the contrast invariance. Our results suggest that orientation tuning in the LGN is caused by an elliptical classical receptive field and orientation-tuned surround suppression, and that its contrast invariance is ensured by local GABA_A inhibition. This contrast-invariant orientation tuning in LGN neurons may contribute to the contrast-invariant orientation tuning seen in V1 neurons.     

Bottom-up guidance to grouped items in conjunction search: evidence for color grouping

Previous studies have demonstrated that observers can search through a subset of items carrying a minority feature to find a conjunction target (Sobel & Cave, 2002). We examined whether subset search takes place when participants have less specific foreknowledge of the target (when the target is one of two possible items), measuring eye movements as well as reaction times. When there were unequal ratios of distractors, fixations were initially directed to the small subset. These initial eye movements were often directed between items with the same feature, suggesting guidance from pooled feature values. There was stronger guidance within color- than orientation-defined groups, although the features were balanced for salience. The results suggest that grouping of items by color operates more globally than grouping in orientation.     

Virtual environment navigation with look-around mode to explore new real spaces by people who are blind

Background: This paper examines the ability of people who are blind to construct a mental map and perform orientation tasks in real space by using Nintendo Wii technologies to explore virtual environments. The participant explores new spaces through haptic and auditory feedback triggered by pointing or walking in the virtual environments and later constructs a mental map, which can be used to navigate in real space.

Methods: The study included 10 participants who were congenitally or adventitiously blind, divided into experimental and control groups. The research was implemented by using virtual environments exploration and orientation tasks in real spaces, using both qualitative and quantitative methods in its methodology.

Results: The results show that the mode of exploration afforded to the experimental group is radically new in orientation and mobility training; as a result 60% of the experimental participants constructed mental maps that were based on map model, compared with only 30% of the control group participants.

Conclusions: Using technology that enabled them to explore and to collect spatial information in a way that does not exist in real space influenced the ability of the experimental group to construct a mental map based on the map model.

• Implications for rehabilitation

• The virtual cane system for the first time enables people who are blind to explore and collect spatial information via the look-around mode in addition to the walk-around mode.

• People who are blind prefer to use look-around mode to explore new spaces, as opposed to the walking mode.

• Although the look-around mode requires users to establish a complex collecting and processing procedure for the spatial data, people who are blind using this mode are able to construct a mental map as a map model.

• For people who are blind (as for the sighted) construction of a mental map based on map model offers more flexibility in choosing a walking path in a real space, accounting for changes that occur in the space.

     

年龄相关性脑白质改变患者认知功能障碍及其特点的研究

目的 探讨年龄相关性脑白质改变(age-related white matter changes,ARWMC)与认知功能之间的关系,以及ARWMC患者认知功能障碍的特点,对老年人认知功能障碍的早期防治提供理论依据. 方法 病例组为ARWMC患者50例,根据CT或MRI影像学的诊断,并采用ARWMC评分系统将其分为轻中度组(ARWMC评分1～10分)26例和重度组(ARWMC评分＞10分)24例;对照组选择同期健康体检老年人20例.采用蒙特利尔认知评估量表(北京版)(MontrealCognitive Assessment,MoCA)测定研究对象的认知功能,比较不同程度ARWMC患者以及正常对照组的认知功能评分,分析ARWMC严重程度与认知功能的相关性,以及ARWMC患者认知功能障碍的特点. 结果 ARWMC患者认知功能MoCA评分较正常对照组下降[正常对照组(26.60±1.23)分、轻中度组(23.19±2.62)分、重度组(19.83±3.09)分,F=39.930,P=0.000],ARWMC严重程度与MoCA评分呈负相关(r=-0.476,P=0.000).ARWMC患者认知功能障碍主要表现在视空间及执行功能(F=13.189,P＜0.05)、延迟回忆(F=32.340,P＜0.05)、定向力(F=15.813,P＜0.05)等方面. 结论 ARWMC与认知功能损害有关,ARWMC程度越重,认知功能损害越明显.     

Choosing between alternative wrist postures: Action planning needs perception

When normal subjects grasp with their right hand a rectangular object placed at different orientations in the horizontal plane, they change from a ‘thumb left’ (clockwise) to a ‘thumb right’ (anti-clockwise) grasp when the orientation exceeds about 110°, with respect to the mid-sagittal plane. This suggests planning of the final grip orientation at, or before the start of the prehension movement. The current study assessed performance of two visual agnosic patients (SB and DF) on a grasping task requiring the planning of final grip posture. Five healthy subjects were also tested. Subjects were required to grasp a triangular-section block, which was presented at one of seven different orientations (80-140°). The healthy subjects showed a consistent relation between object orientation and hand orientation just before contact. In addition, they consistently used a clockwise grasp when object orientation was less than 100°, and an anti-clockwise grasp when it was more than 110°, with a sharply defined switch-point being identifiable for each subject. For both visual agnosic patients, hand orientation was also reliably related to object orientation. However, the selection of grasp posture was markedly abnormal: they did not consistently switch between clockwise and anti-clockwise grasps within the normal orientation range, and the switch, when it did occur, was not at all sharply defined. These results suggest that the planning of hand orientation during a grasp depends on a perceptually based judgement of the awkwardness of alternative movements. This would presumably involve ventral stream processing, which is disrupted in the visual agnosic patients.     

牵引器放置方位对骨-牵引器界面生物力学影响的三维有限元分析

目的：建立双侧下颌骨牵引成骨的三维有限元模型，探讨牵引器不同放置方位对骨一牵引器界面的生物力学影响。方法：模拟牵引器放置平行于下颌骨体部及平行于牵引轴方向两种状况，分析下颌骨牵引延长不同工况下骨一牵引器界面位移、综合应力情况。结果：牵引器放置平行于下颌骨体部时，骨一牵引器界面侧向位移、综合应力均大于牵引器放置平行于牵引轴方向的情况。结论：实验结果提示牵引器应尽量放置平行于牵引轴方向，避免可能发生的不良并发症。     

Application of neurite orientation dispersion and density imaging or diffusion tensor imaging to quantify the severity of cervical spondylotic myelopathy and to assess postoperative neurologic recovery

Background Context

Surgical outcome and the severity of cervical spondylotic myelopathy (CSM) are unpredictable and cannot be estimated by conventional anatomical magnetic resonance imaging (MRI). The utility of diffusion tensor imaging (DTI) to quantify the severity of CSM and to assess postoperative neurologic recovery has been investigated. However, whether conventional DTI should be applied in a clinical setting remains controversial. Neurite orientation dispersion and density imaging (NODDI) is a recently introduced model-based diffusion-weighted MRI technique that quantifies specific microstructural features related directly to neuronal morphology. However, there are as yet few clinical applications of NODDI reported. Indeed, there are no reports to indicate NODDI is useful for diagnosing CSM.

我国社区护理学发展的思考与展望

社区护理学是护理学专业发展的重要领域之一,在我国护理学科成为一级学科的大背景下,需要重新审视和分析社区护理学的发展现状,对学科的发展趋势进行深入的思考和探讨.本文结合我国社区卫生服务的发展形势和国际社区护理学的发展经验,深入剖析了目前我国社区护理学科发展中存在的现实问题,并进一步展望了我国社区护理学的发展方向,提出了明确学科定位、完善服务内涵与外延、建立人才培养体系等展望和建议,以促进社区护理学的良性健康发展.     

Three-dimensional visual feature representation in the primary visual cortex

In the cat primary visual cortex, it is accepted that neurons optimally responding to similar stimulus orientations are clustered in a column extending from the superficial to deep layers. The cerebral cortex is, however, folded inside a skull, which makes gyri and fundi. The primary visual area of cats, area 17, is located on the fold of the cortex called the lateral gyrus. These facts raise the question of how to reconcile the tangential arrangement of the orientation columns with the curvature of the gyrus.In the present study, we show a possible configuration of feature representation in the visual cortex using a three-dimensional (3D) self-organization model. We took into account preferred orientation, preferred direction, ocular dominance and retinotopy, assuming isotropic interaction. We performed computer simulation only in the middle layer at the beginning and expanded the range of simulation gradually to other layers, which was found to be a unique method in the present model for obtaining orientation columns spanning all the layers in the flat cortex. Vertical columns of preferred orientations were found in the flat parts of the model cortex. On the other hand, in the curved parts, preferred orientations were represented in wedge-like columns rather than straight columns, and preferred directions were frequently reversed in the deeper layers. Singularities associated with orientation representation appeared as warped lines in the 3D model cortex. Direction reversal appeared on the sheets that were delimited by orientation-singularity lines. These structures emerged from the balance between periodic arrangements of preferred orientations and vertical alignment of the same orientations. Our theoretical predictions about orientation representation were confirmed by multi-slice, high-resolution functional MRI in the cat visual cortex. We obtained a close agreement between theoretical predictions and experimental observations. The present study throws a doubt about the conventional columnar view of orientation representation, although more experimental data are needed.     

猪霍乱沙门菌疫苗株C500毒力致弱的主要原因是rpoS基因的缺失

目的 猪霍乱沙门菌疫苗株C500在我国应用于仔猪副伤寒的防控已长达50多年,然而由于C500是通过化学诱变法获得,因此其遗传背景仍不清楚。本文从基因组水平揭示C500疫苗株毒力致弱的主要原因。方法 利用MOH-SSH方法比较了强毒株C78-2与C500之间的基因组差异,结合荧光定量PCR与动物实验检测缺失基因对疫苗株毒力的影响。结果 发现C500缺失了6个基因(asr、ydgF、ydgD、ydgE、rpoS和ptsG)。其中,作为调控基因的rpoS在沙门菌致病过程中发挥着重要的作用。荧光定量PCR检测发现rpoS调控的基因在C500中的表达出现不同程度的下调。此外,动物实验结果 显示rpoS缺失的C78-2 突变株C78-2ΔrpoS毒力下降了100 000倍。结论 rpoS基因的缺失是导致C500致弱的主要因素。