Choice-specific sequences in parietal cortex during a virtual-navigation decision task

The posterior parietal cortex (PPC) has an important role in many cognitive behaviours; however, the neural circuit dynamics underlying PPC function are not well understood. Here we optically imaged the spatial and temporal activity patterns of neuronal populations in mice performing a PPC-dependent task that combined a perceptual decision and memory-guided navigation in a virtual environment. Individual neurons had transient activation staggered relative to one another in time, forming a sequence of neuronal activation spanning the entire length of a task trial. Distinct sequences of neurons were triggered on trials with opposite behavioural choices and defined divergent, choice-specific trajectories through a state space of neuronal population activity. Cells participating in the different sequences and at distinct time points in the task were anatomically intermixed over microcircuit length scales (<100 micrometres). During working memory decision tasks, the PPC may therefore perform computations through sequence-based circuit dynamics, rather than long-lived stable states, implemented using anatomically intermingled microcircuits.     

Neural correlates of decision variables in parietal cortex.

Decision theory proposes that humans and animals decide what to do in a given situation by assessing the relative value of each possible response. This assessment can be computed, in part, from the probability that each action will result in a gain and the magnitude of the gain expected. Here we show that the gain (or reward) a monkey can expect to realize from an eye-movement response modulates the activity of neurons in the lateral intraparietal area, an area of primate cortex that is thought to transform visual signals into eye-movement commands. We also show that the activity of these neurons is sensitive to the probability that a particular response will result in a gain. When animals can choose freely between two alternative responses, the choices subjects make and neuronal activation in this area are both correlated with the relative amount of gain that the animal can expect from each response. Our data indicate that a decision-theoretic model may provide a powerful new framework for studying the neural processes that intervene between sensation and action.     

A cholecystokinin-like hormone activates a feeding-related neural circuit in lobster

The peptide hormone cholecystokinin (CCK) contributes to the production of feeding-related behaviour in mammals, but the mechanism by which it exerts its effects remains unclear. The gastric mill neural circuit of lobster is an experimentally accessible model system for studying the hormonal control of feeding-related behaviour. Composed of 11 identified neurons, this circuit produces rhythmic movement of teeth within the stomach. We have previously shown that the gastric mill motor pattern can be modulated by a cholecystokinin-like peptide in vitro. We report here that (1) after feeding, levels of CCK-like peptide in haemolymph increase with the activation of the gastric mill, (2) injections of CCK activate the gastric mill, and (3) a specific CCK antagonist inhibits feeding-induced gastric mill activity. This neatly demonstrates a casual link between in vivo release of a peptide hormone and activation of a neural circuit.     

Cross-modal and cross-temporal association in neurons of frontal cortex

The prefrontal cortex is essential for the temporal integration of sensory information in behavioural and linguistic sequences. Such information is commonly encoded in more than one sense modality, notably sight and sound. Connections from sensory cortices to the prefrontal cortex support its integrative function. Here we present the first evidence that prefrontal cortex cells associate visual and auditory stimuli across time. We gave monkeys the task of remembering a tone of a certain pitch for 10 s and then choosing the colour associated with it. In this task, prefrontal cortex cells responded selectively to tones, and most of them also responded to colours according to the task rule. Thus, their reaction to a tone was correlated with their subsequent reaction to the associated colour. This correlation faltered in trials ending in behavioural error. We conclude that prefrontal cortex neurons are part of integrative networks that represent behaviourally meaningful cross-modal associations. The orderly and timely activation of neurons in such networks is crucial for the temporal transfer of information in the structuring of behaviour, reasoning and language.     

晶闸管电路与触发电路的相互影响

分析了晶闸管及单结晶体管工作时内部载流子运动与外在条件的关系；阐明了晶闸管整流电路与单结晶体管触发电路之间有相互影响，分析其内因、外因；介绍了消除不利影响的办法。     

力学系统与电路系统的某些相似性

根据力学规律与电磁学规律的类比 ,分别了力学系统与电路系统的某些相似性 .     

在记忆过程中额叶与信息粒度的交互作用

采用事件相关的功能磁共振技术(fMRI)研究了记忆与信息粒度的相互关系.实验使用相同的记忆任务-Boolean规则,依据Ebbinghaus范式,要求被试在完全掌握规则后的第1天(短期记忆)和学习训练后的第7天(长期记忆)完成fMRI测试.结果表明,短期记忆任务和长期记忆任务均激活了左侧额下回和额中回,但短期记忆任务相对长期记忆任务激活更多的左侧中央前回和额下小叶、右侧的额上回和额中回,而长期记忆比短期记忆激活了更多的右侧的额下回,这可能与规则中的各个元素之间的聚合程度和记忆的精度有关.因此,额叶对不同信息粒度的规则提取有重要影响.高粒度相对于低粒度的Boolean规则提取需要更短的时间,但是记忆信息提取的正确率不会因高低粒度的不同而表现出差异.虽然信息粒度对长、短期记忆任务的提取的正确率不起决定性作用,但信息粒度作为记忆巩固与否的一种度量标准会对提取时间产生影响;这可能使得规则提取的策略不同,因此,额叶对不同粒度的信息提取起到了至关重要的作用.     

条件判定覆盖和修正条件判定覆盖的差异

条件判定覆盖(Condition／Decision Coverage即C／DC)和修正条件判定覆盖(Modified Condition／Decision Coverage即MC／DC)均是软件测试方法,作者首先介绍了这两种测试方法．之后总结出了两者所存在的不同之处,其中以一些实例来证明两种方法的差异．     

自由基,抗氧化剂与运动能力的关系

旨在探讨不同天然抗氧化剂在机体抗氧化过程中的作用及与运动能力之间的关系。采用综述的方法阐述脂质过氧化及抗氧化剂的概念、主要抗氧化剂的物质形式及作用机制。研究结果显示:天然抗氧化剂在对抗脂质过氧化方面有重要作用,可有效清除自由基,保护细胞完整性,但是对补充抗氧化剂提高运动能力的观点提出质疑。     

氧自由基与妇科肿瘤关系的研究

目的探讨超氧化物歧化酶(SOD)、丙二醛(MDA)、一氧化氮(NO)、谷胱甘肽(GSH-PX)与妇科常见肿瘤的关系.方法1)以20例正常健康人为对照组,子宫肌瘤30例、子宫颈癌20例、卵巢癌22例,分别用生物化学法测定血清中SOD,GSH-PX活性与MDA,NO的含量.2)以子宫肌瘤30例、子宫颈癌20例、卵巢癌22例,分别用生物化学法测定癌组织与癌旁组织、子宫肌瘤核组织与核旁组织中SOD,GSH-PX活性和MDA,NO含量.结果1)血清测定中,肿瘤患者的MDA含量、SOD活性比正常对照组高;GSH-PX活性比正常对照组低;良性肿瘤的NO含量高于正常对照组,恶性肿瘤中的NO含量低于正常组.2)组织测定中,肿瘤组织MDA含量,SOD,GSH-PX活性比肿瘤旁组织高,癌组织中NO含量比肿瘤旁组织低.结论子宫颈癌、卵巢癌、子宫肌瘤组织及血清中有明显的自由基代谢紊乱,而且良恶性肿瘤有明显差异,并且随着肿瘤恶化程度的变化,自由基也呈现规律性变化.     

基于频响分析法的脉冲电源与容性负载间匹配电路设计

为克服传统的基于负载匹配法设计的匹配电路存在导致容性负载上脉冲电压上升率明显降低的不足,提高脉冲电源在容性负载下的应用效果,提出了将频响分析用于设计脉冲电源与容性负载问匹配电路的方法．基于此法设计了一种由电感（Lm）支路和与其并联的阻-容（Rm-Cm）串联支路构成的匹配电路,当Lm、Rm和Cm满足使容性负载上的脉冲电压（u2）与脉冲电源输出的脉冲电压（u1）之比（u2/u1）的频响特性,在脉冲电源输出的脉冲电压的有效频谱范围内接近不失真系统频响特性的条件时,可在容性负载上得到既无振荡,且上升率高的脉冲电压．实验验证该匹配电路是有效的．     

Different domains of synaptotagmin control the choice between kiss-and-run and full fusion

Exocytosis-the release of the contents of a vesicle--proceeds by two mechanisms. Full fusion occurs when the vesicle and plasma membranes merge. Alternatively, in what is termed kiss-and-run, vesicles can release transmitter during transient contacts with the plasma membrane. Little is known at the molecular level about how the choice between these two pathways is regulated. Here we report amperometric recordings of catecholamine efflux through individual fusion pores. Transfection with synaptotagmin (Syt) IV increased the frequency and duration of kiss-and-run events, but left their amplitude unchanged. Endogenous Syt IV, induced by forskolin treatment, had a similar effect. Full fusion was inhibited by mutation of a Ca2+ ligand in the C2A domain of Syt I; kiss-and-run was inhibited by mutation of a homologous Ca2+ ligand in the C2B domain of Syt IV. The Ca2+ sensitivity for full fusion was 5-fold higher with Syt I than Syt IV, but for kiss-and-run the Ca2+ sensitivities differed by a factor of only two. Syt thus regulates the choice between full fusion and kiss-and-run, with Ca2+ binding to the C2A and C2B domains playing an important role in this choice.     

一种宽带非福斯特电路设计与实现

对一种负阻抗变换器(NIC)来实现宽带非福斯特电路特性进行了理论分析,给出了NIC的稳定性工作条件.以宽带运算放大器为核心设计了宽带非福斯特电路,对电路进行了时域和频域仿真,提出了一种负阻抗等效测试方法.仿真和测试结果都表明,设计的宽带非福斯特电路可以在几十倍频程带宽内实现负阻抗变换,且电路简单,具有很高的稳定性,证实了理论分析的正确性和有效性.     

关于选择函数一致性条件描述的分析

研究了选择函数的一致性条件描述问题。定义选择函数并给出理性选择函数的形式化描述；定义一致性条件并探讨了一致性条件间的相互关系。在此基础上，探讨一致性条件与理性选择函数间的相互关系，得到了选择函数为理性选择函数的充分必要条件。     

烷基黄原酸及其有关化合物的线性自由能关系

本文根据文献报导的数据,对烷基黄原酸的热力学参数及其对应的几种化合物的若干热力学参数间的关系作了考察,发现烷基黄原酸的PK_a值与下列各参数存在着线性自由能关系:烷基黄原酸本身的标准电极电位E~0(v);烷基黄原酸所对应烷基醇的PK_a值和烷基黄原酸的Zn,C_d络合物的稳定常数。并且从理论上推导了这些关系。支链烷基各常数偏离直线关系,用空间位阻效应作了解释。     

Prostaglandins and the synergism between VIP and noradrenaline in the cerebral cortex

We have previously shown that vasoactive intestinal peptide (VIP) and noradrenaline (NA) interact synergistically to increase cyclic AMP levels in mouse cerebral cortical slices. The pharmacological mechanism of this synergism is the potentiation by NA, through alpha 1 adrenergic receptors, of the stimulatory effect of VIP on cAMP formation. A similar interaction has been confirmed in guinea pig cerebral cortex and in discrete nuclei of the rat hypothalamus. Furthermore VIP and NA interact synergistically to depress the spontaneous activity of identified neurons in rat neocortex. At the cellular level, this synergistic interaction suggests that VIP- and NA-containing neuronal systems may converge, at least in part, on the same target cells to increase cAMP levels in the cerebral cortex. At the molecular level, the interaction may occur at various steps in signal transduction, between receptors, intramembrane transduction processes or intracellular effector mechanisms. Here we report that the alpha 1-adrenergic potentiation of the increases in cAMP elicited by VIP involves the formation of arachidonic acid metabolites and is mimicked by prostglandins F2 alpha and E2.     

集团公司财务控制集权与分权选择问题浅探

就集团公司财务控制集权与分权的两难选择做了进一步探析，通过对集团公司集权与分权必然性、本质的探讨及3种方式优缺点的比较，为集团公司的权衡和选择提供了参考。