Neuroanatomy: brain asymmetry and long-term memory

The asymmetrical positioning of neural structures on the left or right side of the brain in vertebrates and in invertebrates may be correlated with brain laterality, which is associated with cognitive skills. But until now this has not been illustrated experimentally. Here we describe an asymmetrically positioned brain structure in the fruitfly Drosophila and find that the small proportion of wild-type flies that have symmetrical brains with two such structures lack a normal long-term memory, although their short-term memory is intact. Our results indicate that brain asymmetry may be required for generating or retrieving long-term memory.     

Neuronal correlate of visual associative long-term memory in the primate temporal cortex

In human long-term memory, ideas and concepts become associated in the learning process. No neuronal correlate for this cognitive function has so far been described, except that memory traces are thought to be localized in the cerebral cortex; the temporal lobe has been assigned as the site for visual experience because electric stimulation of this area results in imagery recall and lesions produce deficits in visual recognition of objects. We previously reported that in the anterior ventral temporal cortex of monkeys, individual neurons have a sustained activity that is highly selective for a few of the 100 coloured fractal patterns used in a visual working-memory task. Here I report the development of this selectivity through repeated trials involving the working memory. The few patterns for which a neuron was conjointly selective were frequently related to each other through stimulus-stimulus association imposed during training. The results indicate that the selectivity acquired by these cells represents a neuronal correlate of the associative long-term memory of pictures.     

Time-dependent reorganization of brain circuitry underlying long-term memory storage.

Retrograde amnesia observed following hippocampal lesions in humans and animals is typically temporally graded, with recent memory being impaired while remote memories remain intact, indicating that the hippocampal formation has a time-limited role in memory storage. However, this claim remains controversial because studies involving hippocampal lesions tell us nothing about the contribution of the hippocampus to memory storage if this region was present at the time of memory retrieval. We therefore used non-invasive functional brain imaging using (14C)2-deoxyglucose uptake to examine how the brain circuitry underlying long-term memory storage is reorganized over time in an intact brain. Regional metabolic activity in the brain was mapped in mice tested at different times for retention of a spatial discrimination task. Here we report that increasing the retention interval from 5 days to 25 days resulted in both decreased hippocampal metabolic activity during retention testing and a loss of correlation between hippocampal metabolic activity and memory performance. Concomitantly, a recruitment of certain cortical areas was observed. These results indicate that there is a time-dependent reorganization of the neuronal circuitry underlying long-term memory storage, in which a transitory interaction between the hippocampal formation and the neocortex would mediate the establishment of long-lived cortical memory representations.     

Role for a cortical input to hippocampal area CA1 in the consolidation of a long-term memory

A dialogue between the hippocampus and the neocortex is thought to underlie the formation, consolidation and retrieval of episodic memories, although the nature of this cortico-hippocampal communication is poorly understood. Using selective electrolytic lesions in rats, here we examined the role of the direct entorhinal projection (temporoammonic, TA) to the hippocampal area CA1 in short-term (24 hours) and long-term (four weeks) spatial memory in the Morris water maze. When short-term memory was examined, both sham- and TA-lesioned animals showed a significant preference for the target quadrant. When re-tested four weeks later, sham-lesioned animals exhibited long-term memory; in contrast, the TA-lesioned animals no longer showed target quadrant preference. Many long-lasting memories require a process called consolidation, which involves the exchange of information between the cortex and hippocampus. The disruption of long-term memory by the TA lesion could reflect a requirement for TA input during either the acquisition or consolidation of long-term memory. To distinguish between these possibilities, we trained animals, verified their spatial memory 24 hours later, and then subjected trained animals to TA lesions. TA-lesioned animals still exhibited a deficit in long-term memory, indicating a disruption of consolidation. Animals in which the TA lesion was delayed by three weeks, however, showed a significant preference for the target quadrant, indicating that the memory had already been adequately consolidated at the time of the delayed lesion. These results indicate that, after learning, ongoing cortical input conveyed by the TA path is required to consolidate long-term spatial memory.     

Neural activity predicts individual differences in visual working memory capacity

Contrary to our rich phenomenological visual experience, our visual short-term memory system can maintain representations of only three to four objects at any given moment. For over a century, the capacity of visual memory has been shown to vary substantially across individuals, ranging from 1.5 to about 5 objects. Although numerous studies have recently begun to characterize the neural substrates of visual memory processes, a neurophysiological index of storage capacity limitations has not yet been established. Here, we provide electrophysiological evidence for lateralized activity in humans that reflects the encoding and maintenance of items in visual memory. The amplitude of this activity is strongly modulated by the number of objects being held in the memory at the time, but approaches a limit asymptotically for arrays that meet or exceed storage capacity. Indeed, the precise limit is determined by each individual's memory capacity, such that the activity from low-capacity individuals reaches this plateau much sooner than that from high-capacity individuals. Consequently, this measure provides a strong neurophysiological predictor of an individual's capacity, allowing the demonstration of a direct relationship between neural activity and memory capacity.     

Neural measures reveal individual differences in controlling access to working memory

The capacity of visual short-term memory is highly limited, maintaining only three to four objects simultaneously. This extreme limitation necessitates efficient mechanisms to select only the most relevant objects from the immediate environment to be represented in memory and to restrict irrelevant items from consuming capacity. Here we report a neurophysiological measure of this memory selection mechanism in humans that gauges an individual's efficiency at excluding irrelevant items from being stored in memory. By examining the moment-by-moment contents of visual memory, we observe that selection efficiency varies substantially across individuals and is strongly predicted by the particular memory capacity of each person. Specifically, high capacity individuals are much more efficient at representing only the relevant items than are low capacity individuals, who inefficiently encode and maintain information about the irrelevant items present in the display. These results provide evidence that under many circumstances low capacity individuals may actually store more information in memory than high capacity individuals. Indeed, this ancillary allocation of memory capacity to irrelevant objects may be a primary source of putative differences in overall storage capacity.     

自联想映射存储器——一种新的非线性人工神经网络存储器模型

提出了一种基于图论理论的新的非线性人工神经网络存储器模型—自联想映射存储器。该存储器借助一种特殊的矩阵逻辑异或（ＸＯＲ）运算和存储器结构,可以实现大容量信息的动态存储和自联想记忆功能,具有结构简单,存储容量大和良好的动态特性,是一种理想的实时计算机信息处理系统信息存储器。     

20面体平图的4着色与对偶树的分解

阐明了任意平图的对偶图的4着色的基本思路,提出了借助于对偶图的2棵对偶树T^A和T^B的分解,实现对偶图的4着色方法。介绍了20面体平图的对偶树T^A和T^B的分解及4着色的不同方案。     

军队学习型党组织建设的对策思考

建设马克思主义学习型政党,是提高党建科学化水平的战略抉择,是提高党的执政能力、保持党的先进性的内在要求,是党始终走在时代前列、引领中国发展进步的重要基础,也是推动军队建设科学发展、有效履行使命的现实需要。建设学习型党组织是建设学习型政党的基础工程,必须充分认识建设学习型党组织的重要意义,明确原则和要求,拓展学习内容,创新方法途径,增强学习实效,深入开展建设学习型党组织活动。     

组织变革的方向--建立学习型组织

组织变革是组织生存与发展的永恒主题.建立学习型组织是复杂环境下组织变革的重要趋势.文章讨论了学习型组织产生的背景、组织的知识、组织学习的主要障碍和组织学习的机制,指出促进组织学习的管理规则以及学习型组织的主要特征.     

Evidence for a spin-aligned neutron-proton paired phase from the level structure of (92)Pd

Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work that introduced a strong spin-orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron-proton pairing, in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus (92)Pd. Gamma rays emitted following the (58)Ni((36)Ar,2n)(92)Pd fusion-evaporation reaction were identified using a combination of state-of-the-art high-resolution γ-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron-proton coupling scheme, different from the previous prediction. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron-proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis.     

Synaptic facilitation requires paired activation of convergent pathways in the neocortex

In associative learning, the activated neurones undergo a variety of concomitant functional alterations--increases or decreases of firing activity and modifications of membrane potential or resistance and of synaptic responsiveness. Synaptic transmission which can be strengthened only when there is paired activity in two pathways is of particular interest in relation to mechanisms for associative learning. For the neocortex, there are few observations of the plastic changes, induced by conditioning procedures, in the effectiveness of individual synapses. We now report that various regimes with joint stimulations of convergent excitatory pathways on to intracellularly recorded neurones in the motor cortex of the cat result in synaptic facilitation lasting for up to 30 min.     

细胞神经网络的研究进展

本文综述了细胞神经网络的理论、硬件实现、软件系统以及一些应用。     

《计算机组成原理》(运算器)多媒体模拟实验教学

介绍如何应用计算机设计<计算机组成原理>的实验教学,应用C++编写功能函数来模拟各种芯片的工作,使同学们在学习中更直观的了解芯片的工作.所介绍的程序是对运算功能发生器(74LS181)的模拟编程,完成32种算术逻辑运算实验.     

《计算机组成原理》（运算器）多媒体模拟实验教学

介绍如何应用计算机设计《计算机组成原理》的实验教学，应用C 编写功能函数来模拟各种芯片的工作，使同学们在学习中更直观的了解芯片的工作。所介绍的程序是对运算功能发生器(74LS181)的模拟编程，完成32种算术逻辑运算实验。     

Neural network model for the constitutive relations of soil

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