Geographic spatial autocorrelation and United States suicide patterns

Research on aggregated geographical data in such fields as genetics and epidemiology have produced inefficient findings when spatial autocorrelation is present. This inefficiency results from the bias in the standard errors of the regression coefficients for multi-variate studies. It is unclear as to whether the numerous suicide studies that utilize geographical units of analysis am also flawed. The present study employs Odland's test for spatial autocorrelation to ascertain whether this error is present in geographical suicide studies. Two typical studies that employ state and county (parish) data art examined to decide whether spatial autocorrelation limits the findings of these studies. Using a conservative randomization test with Moran's I, it is concluded that for these studies spatial autocorrelation is not a serious problem. However, other weight matrices, and less conservative tests are needed to further support the findings of this paper.     

Differential contributions of dorsal hippocampal subregions to memory acquisition and retrieval in contextual fear-conditioning

The hippocampus is an essential neural structure in developing contextual memory in a situation in which rapid development of associative learning should occur. We tested a subregion-specific contribution in the hippocampus to memory acquisition and retrieval, using the contextual fear-conditioning paradigm. The current results suggest that all three subregions (i.e., CA3, CA1, and dentate gyrus) of the hippocampus contribute to rapid acquisition of contextual memory in the initial phase of acquisition. The involvement of CA3 seems to be important at the earliest stage of acquisition, presumably for developing instant representation of a context. The role of CA3, however, was minimal in retrieving contextual memory after a long time period (i.e., 24 h), whereas the other subregions (i.e., CA1 and dentate gyrus) were critically involved. The results indicate time-dependent differential contributions of the hippocampal subregions to memory acquisition and retrieval in contextual fear-conditioning.     

Hermann Zingerle's "Impaired perception of the own body due to organic brain disorders". 1913. An introductory comment, and an abridged translation

In the late 1970's Edoardo Bisiach and his coworkers provided definitive evidence that spatial unilateral neglect involves a disorder of the internal representation of extra-personal space. A few years later Bisiach and Berti (1987) revived the so far neglected contribution of an Austrian neurologist, Hermann Zingerle (1913). Ninety years ago Zingerle had described the symptom-complex of two right-brain-damaged patients, who showed left hemisomatoagnosia, unawareness of left hemiplegia, and left motor neglect. In addition to the detailed case reports, Zingerle had put forward a unitary interpretation of these deficits in terms of a disordered representation of one side of the body (dyschiria). A unitary representational account of these unilateral impairments was conspicuously absent in the contemporary neurological literature (Anton, Pick, Babinski), and attracted Bisiach's interest. An abridged translation of Zingerle's paper is provided. The clinical case reports and Zingerle's conclusions are discussed, with reference both to Bisiach's views, and to present knowledge of unilateral spatial neglect.     

Overexpression of calbindin D(28k) in dentate gyrus granule cells alters mossy fiber presynaptic function and impairs hippocampal-dependent memory

Calcium is a key signaling ion for induction of synaptic plasticity processes that are believed to influence cognition. Mechanisms regulating activity-induced increases in neuronal calcium and related synaptic modifications are not fully understood. Moreover, involvement of specific synapses in discrete aspects of spatial learning remains to be elucidated. We used herpes simplex amplicons to overexpress calbindin D(28k) (CaBP) selectively in dentate gyrus (DG) granule cells. We then examined the effects on hippocampal network activity by recording evoked synaptic responses in vivo and in vitro and analyzing hippocampal-dependent behavior. Relative to Lac-Z- and sham-infected controls, CaBP overexpression increased mossy fiber (MF-CA3) excitatory postsynaptic potentials and reduced paired-pulse facilitation (PPF), suggesting an increase in presynaptic strength. Additionally, CaBP overexpression reduced long-term potentiation (LTP), caused a frequency-dependent inhibition of post-tetanic potentiation (PTP), and impaired spatial navigation. Thus, increasing CaBP levels selectively in the DG disrupts MF-CA3 presynaptic function and impairs spatial cognition. The results demonstrate the power of gene delivery in the study of the neural substrates of learning and memory and suggest that mossy fiber synaptic plasticity is critical for long-term spatial memory.     

Sensorimotor effects on central space representation: prism adaptation influences haptic and visual representations in normal subjects

Prism adaptation improves visual and haptic manifestations of left neglect, and can induce a small but reliable simulation of left visual neglect in normal individuals. Here, we present two experiments in which the effects of prism adaptation on the representation of space were explored. In Experiment 1, normal subjects were required to locate the centre of a haptically explored circle, before and after adaptation to leftward displacing prisms. In Experiment 2, a visual circle centring task was used. In both tasks, prism adaptation induced a significant rightward shift of performance. In addition, in both experiments, three classical measures of visuo-manual adaptation were taken: the visual shift, the proprioceptive shift and the total shift. The effects found on the haptic and visual tasks did not correlate with any of these measures. This suggests that the effects of prism adaptation on the circle centring tasks did not depend directly on the sensorimotor consequences of the adaptation. These results imply that prism adaptation can affect noetic levels of space representation in normal subjects, supporting the hypothesis that this low-level sensorimotor intervention can exert a bottom-up structuring influence on higher levels of cognitive integration.     

导航下神经内镜与显微手术治疗基底节脑出血的对比研究

目的 探讨导航下神经内镜与显微手术治疗基底节脑出血的疗效及安全性.方法 将60例高血压基底节脑出血患者分为导航内镜组(n=32)和显微手术组(n=28),比较两组患者的临床资料.结果 导航内镜组手术时间(112.1±14.5)min,术中中位失血量100.0(92.5,140.0)mL,血肿清除率(93.6±3.7)％...     

Spatiotemporal flow of information in the early visual pathway

The spatial components of a visual scene are processed neurally in a sequence of coarse features followed by fine features. This coarse‐to‐fine temporal stream was initially considered to be a cortical function, but has recently been demonstrated in the dorsal lateral geniculate nucleus. The goal of this study was to test the hypothesis that coarse‐to‐fine processing is present at earlier stages of visual processing in the retinal ganglion cells that supply lateral geniculate nucleus (LGN) neurons. To compare coarse‐to‐fine processing in the cat's visual system, we measured the visual responses of connected neuronal pairs from the retina and LGN, and separate populations of cells from each region. We found that coarse‐to‐fine processing was clearly present at the ganglion cell layer of the retina. Interestingly, peak and high‐spatial‐frequency cutoff responses were higher in the LGN than in the retina, indicating that there was a progressive cascade of coarse‐to‐fine information from the retina to the LGN to the visual cortex. The analysis of early visual pathway receptive field characteristics showed that the physiological response interplay between the center and surround regions was consistent with coarse‐to‐fine features and may provide a primary role in the underlying mechanism. Taken together, the results from this study provided a framework for understanding the emergence and refinement of coarse‐to‐fine processing in the visual system.     

Predicting episodic and spatial memory performance from hippocampal resting‐state functional connectivity: Evidence for an anterior–posterior division of function

fMRI studies have identified distinct resting‐state functional connectivity (RSFC) networks associated with the anterior and posterior hippocampus. However, the functional relevance of these two networks is still largely unknown. Hippocampal lesion studies and task‐related fMRI point to a role for the anterior hippocampus in nonspatial episodic memory and the posterior hippocampus in spatial memory. We used Relevance Vector Regression (RVR), a machine‐learning method that enables predictions of continuous outcome measures from multivariate patterns of brain imaging data, to test the hypothesis that patterns of whole‐brain RSFC associated with the anterior hippocampus predict episodic memory performance, while patterns of whole‐brain RSFC associated with the posterior hippocampus predict spatial memory performance. Magnetic resonance imaging and memory assessment took place at two separate occasions. The anterior and posterior RSFC largely corresponded with previous findings, and showed no effect of laterality. Supporting the hypothesis, RVR produced accurate predictions of episodic performance from anterior, but not posterior, RSFC, and accurate predictions of spatial performance from posterior, but not anterior, RSFC. In contrast, a univariate approach could not predict performance from resting‐state connectivity. This supports a functional dissociation between the anterior and posterior hippocampus, and indicates a multivariate relationship between intrinsic functional networks and cognitive performance within specific domains, that is relatively stable over time.     

Comparison of a non‐stationary voxelation‐corrected cluster‐size test with TFCE for group‐Level MRI inference

Two powerful methods for statistical inference on MRI brain images have been proposed recently, a non‐stationary voxelation‐corrected cluster‐size test (CST) based on random field theory and threshold‐free cluster enhancement (TFCE) based on calculating the level of local support for a cluster, then using permutation testing for inference. Unlike other statistical approaches, these two methods do not rest on the assumptions of a uniform and high degree of spatial smoothness of the statistic image. Thus, they are strongly recommended for group‐level fMRI analysis compared to other statistical methods. In this work, the non‐stationary voxelation‐corrected CST and TFCE methods for group‐level analysis were evaluated for both stationary and non‐stationary images under varying smoothness levels, degrees of freedom and signal to noise ratios. Our results suggest that, both methods provide adequate control for the number of voxel‐wise statistical tests being performed during inference on fMRI data and they are both superior to current CSTs implemented in popular MRI data analysis software packages. However, TFCE is more sensitive and stable for group‐level analysis of VBM data. Thus, the voxelation‐corrected CST approach may confer some advantages by being computationally less demanding for fMRI data analysis than TFCE with permutation testing and by also being applicable for single‐subject fMRI analyses, while the TFCE approach is advantageous for VBM data. Hum Brain Mapp 38:1269–1280, 2017. © 2016 Wiley Periodicals, Inc.     

基于C型臂手术导航技术的XRⅡ图像中标志物识别及数据提取*☆

XRII图像中标志物的识别及数据提取是基于C型臂手术导航关键技术之一。现有方法可靠性差,检测精度低。本文提出一种混合标志物检测算法。首先通过一种改进CHT法获取参数空间,并获取其横切面二值化图像;而后进行连通分量分析,识别出其中的圆形体并提取其面积及中心坐标数据。改进CHT对掩模及积分算子进行了重新定义;连通分量分析则采用一种新的圆形测度。实验表明所提算法具有更高检测率、检测精度及可靠性。