Nucleus accumbens D2/3 receptors predict trait impulsivity and cocaine reinforcement

Stimulant addiction is often linked to excessive risk taking, sensation seeking, and impulsivity, but in ways that are poorly understood. We report here that a form of impulsivity in rats predicts high rates of intravenous cocaine self-administration and is associated with changes in dopamine (DA) function before drug exposure. Using positron emission tomography, we demonstrated that D2/3 receptor availability is significantly reduced in the nucleus accumbens of impulsive rats that were never exposed to cocaine and that such effects are independent of DA release. These data demonstrate that trait impulsivity predicts cocaine reinforcement and that D2 receptor dysfunction in abstinent cocaine addicts may, in part, be determined by premorbid influences.     

Damage to the insula disrupts addiction to cigarette smoking

A number of brain systems have been implicated in addictive behavior, but none have yet been shown to be necessary for maintaining the addiction to cigarette smoking. We found that smokers with brain damage involving the insula, a region implicated in conscious urges, were more likely than smokers with brain damage not involving the insula to undergo a disruption of smoking addiction, characterized by the ability to quit smoking easily, immediately, without relapse, and without persistence of the urge to smoke. This result suggests that the insula is a critical neural substrate in the addiction to smoking.     

Factors that predict individual vulnerability to amphetamine self-administration

Clinical observations show that there is considerable individual variability in the response to the addictive properties of drugs. This individual variability needs to be taken into account in animal models of addiction. Like humans, only some rats readily self-administer low doses of psychostimulants. The individual animals at risk can be identified on the basis of their response to environmental or pharmacological challenges. This predisposition to develop self-administration can be induced by repeated treatment with amphetamine. These results may help elucidate the neurobiological basis of addiction liability observed in both rats and humans.     

抗热应激几种中草药添加剂应用效果比较

利用人工气候室模拟北京地区夏季高温条件研究了北京红鸡几个主要生产性能指标及血液理化指标的变化趋势，并建立了一系列回归方程对进一步研究蛋鸡热应激进程中自身理化指标的变化规律以及确认抗热应激添加剂的添加效果都将具有指导意义．     

Evidence for addiction-like behavior in the rat

Although the voluntary intake of drugs of abuse is a behavior largely preserved throughout phylogeny, it is currently unclear whether pathological drug use ("addiction") can be observed in species other than humans. Here, we report that behaviors that resemble three of the essential diagnostic criteria for addiction appear over time in rats trained to self-administer cocaine. As in humans, this addiction-like behavior is present only in a small proportion of subjects using cocaine and is highly predictive of relapse after withdrawal. These findings provide a new basis for developing a true understanding and treatment of addiction.     

预期想象影响延迟折扣的内在机制: 情绪的作用——高、 低冲动特质的分离效应

采用跨期选择任务考察了积极、中性、消极情绪效价的预期想象对高、低冲动者的延迟折扣的改变机制.结果发现:(1)总体而言,积极预期想象显著降低了被试的延迟折扣,消极预期想象显著增加了被试的延迟折扣,而中性预期想象对延迟折扣则没有明显影响;(2)具体而言,积极预期想象明显降低了高、低冲动性2组被试的延迟折扣,但消极预期想象只显著增加了高冲动组的延迟折扣,对低冲动组的影响则不显著.结果支持了"情境预期-情绪假说"理论,即预期想象通过预期情绪调节延迟折扣改变的方向;消极预期想象显著增加了高冲动组的延迟折扣而对低冲动组没有明显影响,可能是低冲动组具有更好的自我控制能力.     

Abnormal brain structure implicated in stimulant drug addiction

Addiction to drugs is a major contemporary public health issue, characterized by maladaptive behavior to obtain and consume an increasing amount of drugs at the expense of the individual's health and social and personal life. We discovered abnormalities in fronto-striatal brain systems implicated in self-control in both stimulant-dependent individuals and their biological siblings who have no history of chronic drug abuse; these findings support the idea of an underlying neurocognitive endophenotype for stimulant drug addiction.     

我国农村居民消费行为的实验研究

为深入研究我国农村居民的消费行为,揭示我国农村居民消费的行为特征及变化趋势,探讨增加农村居民收入、拓展农村消费的政策作用机制。采用经济计量学的研究方法,分别基于一元线性系统和一元非线性系统,构建我国农村居民消费行为的状态空间模型(State Space Model),并基于模型对相关时变参数进行卡尔曼滤波(Kalman filter)估计,详细地分析了我国农村居民1978—2010年间平均消费倾向(APC)和边际消费倾向(MPC)的变动趋势及相互关系;同时,对模型作了序列相关性检验、异方差检验和协整检验,以确保模型的合理性和有效性。通过对状态空间模型时变参数的估计,详细分析了我国农村居民消费行为的静态特征和动态特征及其相互关系,较好地解释了外部环境和内在动机对我国农村居民消费行为的影响机制。研究表明:我国农村居民消费行为的状态空间模型是合理的、有效的;农村居民消费行为表现为消费心理预期波动上行,消费倾向偏离趋于缩小,符合我国农村社会经济发展的客观现实。     

Impulsive choice induced in rats by lesions of the nucleus accumbens core

Impulsive choice is exemplified by choosing a small or poor reward that is available immediately, in preference to a larger but delayed reward. Impulsive choice contributes to drug addiction, attention-deficit/hyperactivity disorder, mania, and personality disorders, but its neuroanatomical basis is unclear. Here, we show that selective lesions of the nucleus accumbens core induce persistent impulsive choice in rats. In contrast, damage to two of its afferents, the anterior cingulate cortex and medial prefrontal cortex, had no effect on this capacity. Thus, dysfunction of the nucleus accumbens core may be a key element in the neuropathology of impulsivity.     

Drug abuse control: policy turns toward rehabilitation

Heroin addiction is the most difficult to control and the most socially destructive form of addiction in America today. Heroin is a fact of life and a cause of death among an increasing number of citizens in America, and it is heroin addiction that must command priority in the struggle against drugs.-President Nixon in his drug message to Congress on 17 June.     

Addiction as a computational process gone awry

Addictive drugs have been hypothesized to access the same neurophysiological mechanisms as natural learning systems. These natural learning systems can be modeled through temporal-difference reinforcement learning (TDRL), which requires a reward-error signal that has been hypothesized to be carried by dopamine. TDRL learns to predict reward by driving that reward-error signal to zero. By adding a noncompensable drug-induced dopamine increase to a TDRL model, a computational model of addiction is constructed that over-selects actions leading to drug receipt. The model provides an explanation for important aspects of the addiction literature and provides a theoretic view-point with which to address other aspects.     

Protein kinase C overactivity impairs prefrontal cortical regulation of working memory

The prefrontal cortex is a higher brain region that regulates thought, behavior, and emotion using representational knowledge, operations often referred to as working memory. We tested the influence of protein kinase C (PKC) intracellular signaling on prefrontal cortical cognitive function and showed that high levels of PKC activity in prefrontal cortex, as seen for example during stress exposure, markedly impair behavioral and electrophysiological measures of working memory. These data suggest that excessive PKC activation can disrupt prefrontal cortical regulation of behavior and thought, possibly contributing to signs of prefrontal cortical dysfunction such as distractibility, impaired judgment, impulsivity, and thought disorder.     

Drug policy: striking the right balance

Drug policy should strike the right balance between reducing the harm done by psychoactive drugs and reducing the harm that results from strict legal prohibitions and their enforcement. It is concluded, from a cost-benefit analysis based on pharmacologic, toxicologic, sociologic, and historical facts, that radical steps to repeal the prohibitions on presently illicit drugs would be likely, on balance, to make matters worse rather than better. Specific recommendations are offered for ameliorating the dangers to users and to society that are posed by each addictive drug.     

Serotonin modulates behavioral reactions to unfairness

Serotonin (5-HT) has long been implicated in social behavior and impulsivity, but the mechanisms through which it modulates self-control remain unclear. We observed the effects of manipulating 5-HT function on behavior in the ultimatum game, where players must decide whether to accept or reject fair or unfair monetary offers from another player. Participants with depleted 5-HT levels rejected a greater proportion of unfair offers, but not fair offers, without showing changes in mood, fairness judgment, basic reward processing, or response inhibition. Our results suggest that 5-HT plays a critical role in regulating emotion during social decision-making.     

Temporally unstable recurrence of earthquakes due to breaks in fractal scaling

Observed sequences of large earthquakes are not consistent in either recurrence time or energy release; long-term prediction has been impossible even in areas, such as Parkfield, with well-defined recurrence intervals. The seismic gap hypothesis, which predicts characteristic earthquakes in areas of the circum-Pacific belt that have not produced recent great earthquakes, has also failed to predict the observed clustering of high-energy events. Models in which fractal scaling is broken at high magnitude predict that characteristic events and recurrence behavior will be unstable in time. The central predictions of these models are supported by recent observations at Landers and Big Bear in California.     

Relapse to cocaine-seeking after hippocampal theta burst stimulation

Treatment efforts for cocaine addiction are hampered by high relapse rates. To map brain areas underlying relapse, we used electrical brain stimulation and intracranial injection of pharmacological compounds after extinction of cocaine self-administration behavior in rats. Electrical stimulation of the hippocampus containing glutamatergic fibers, but not the medial forebrain bundle containing dopaminergic fibers, elicited cocaine-seeking behavior dependent on glutamate in the ventral tegmental area. This suggests a role for glutamatergic neurotransmission in relapse to cocaine abuse. The medial forebrain bundle electrodes supported intense electrical self-stimulation. These findings suggest a dissociation of neural systems subserving positive reinforcement (self-stimulation) and incentive motivation (relapse).     

根系分泌物在不同播种模式中的化感效应研究

通过发芽试验研究了不同作物根系分泌物在不同浓度、不同组合方式下对单播和混播作物根干重和芽干重造成的化感效应。结果表明,鹰咀豆根分泌物苯甲醛是一种自毒型化感物质,小麦根分泌物间甲酚和玉米根分泌物邻苯二甲酸是他感型化感物质。间甲酚和苯甲醛组成的混合溶液,以及由3种物质组成的混合溶液对小麦、玉米、鹰咀豆根干重无明显的累加化感作用,但对芽干重具有累加化感作用。与单作相比混播能够弱化高浓度化感物质的负效应,同时可以减小化感物质对芽干重的化感作用。     

国内外不同教育体制对青少年网络成瘾的影响

随着互联网的发展,网络成瘾症对青少年学生身心的危害日益受到社会各界的关注。已有调查表明,尽管西方国家互联网的普及程度远远高于我国,而且青少年也是主要的使用者,但上网成瘾却并没有成为青少年教育和管理中的一个突出问题。为此,在详细分析国内外教育体制因素的基础上,提出了青少年学生网络成瘾的应对策略。     

身份融合对农民工就业的影响——基于倾向得分匹配的研究

身份融合是理解农民工经济行为的重要概念。基于2013年浙江省的农民工调研数据,本研究探讨了身份融合对农民工就业的影响。为了解决可能存在的自选择问题,采用倾向得分匹配法进行实证分析。结果表明:身份融合对农民工的劳动参与有显著影响,身份融合对农民工自我雇佣和工作强度的影响并不显著;身份融合对农民工就业的影响存在明显的代际差异、性别差异以及户籍地差异。本研究获得的政策启示在于:促进农民工的城市融入有利于稳定他们的就业预期,实现劳动供给的可持续发展,对中国经济的发展具有重要作用。     

中古社会的容止观与士人服石之风

士人服石之风曾是汉末魏晋南北朝人们精神自由、个性解放的一种象征。然士人服石与中古社会的容止观,其中特别是人物审美日益趋向病态化或女性化有关。由于这种容止观影响到了当时的选官择仕标准,使得许多士族人物通过“服石”这一极端方式来“改容姿”,从而造成了士人服石之风。