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171.
Flagel SB Clark JJ Robinson TE Mayo L Czuj A Willuhn I Akers CA Clinton SM Phillips PE Akil H 《Nature》2011,469(7328):53-57
Individuals make choices and prioritize goals using complex processes that assign value to rewards and associated stimuli. During Pavlovian learning, previously neutral stimuli that predict rewards can acquire motivational properties, becoming attractive and desirable incentive stimuli. However, whether a cue acts solely as a predictor of reward, or also serves as an incentive stimulus, differs between individuals. Thus, individuals vary in the degree to which cues bias choice and potentially promote maladaptive behaviour. Here we use rats that differ in the incentive motivational properties they attribute to food cues to probe the role of the neurotransmitter dopamine in stimulus-reward learning. We show that intact dopamine transmission is not required for all forms of learning in which reward cues become effective predictors. Rather, dopamine acts selectively in a form of stimulus-reward learning in which incentive salience is assigned to reward cues. In individuals with a propensity for this form of learning, reward cues come to powerfully motivate and control behaviour. This work provides insight into the neurobiology of a form of stimulus-reward learning that confers increased susceptibility to disorders of impulse control. 相似文献
172.
CREBBP mutations in relapsed acute lymphoblastic leukaemia 总被引:2,自引:0,他引:2
173.
174.
Watters TR Leuschen CJ Plaut JJ Picardi G Safaeinili A Clifford SM Farrell WM Ivanov AB Phillips RJ Stofan ER 《Nature》2006,444(7121):905-908
A hemispheric dichotomy on Mars is marked by the sharp contrast between the sparsely cratered northern lowland plains and the heavily cratered southern highlands. Mechanisms proposed to remove ancient crust or form younger lowland crust include one or more giant impacts, subcrustal transport by mantle convection, the generation of thinner crust by plate tectonics, and mantle overturn following solidification of an early magma ocean. The age of the northern lowland crust is a significant constraint on these models. The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument on the European Space Agency's Mars Express spacecraft is providing new constraints on the martian subsurface. Here we show evidence of buried impact basins ranging in diameter from about 130 km to 470 km found over approximately 14 per cent of the northern lowlands. The number of detected buried basins >200 km in diameter indicates that the lowland crust is ancient, dating back to the Early Noachian epoch. This crater density is a lower limit because of the likelihood that not all buried basins in the area surveyed by MARSIS have been detected. An Early Noachian age for the lowland crust has been previously suggested on the basis of a large number of quasi-circular topographic depressions interpreted to be evidence of buried basins. Only a few of these depressions in the area surveyed by MARSIS, however, correlate with the detected subsurface echoes. On the basis of the MARSIS data, we conclude that the northern lowland crust is at least as old as the oldest exposed highland crust. This suggests that the crustal dichotomy formed early in the geologic evolution of Mars. 相似文献
175.
Goldraij A Kondo K Lee CB Hancock CN Sivaguru M Vazquez-Santana S Kim S Phillips TE Cruz-Garcia F McClure B 《Nature》2006,439(7078):805-810
Pollen-pistil interactions are crucial for controlling plant mating. For example, S-RNase-based self-incompatibility prevents inbreeding in diverse angiosperm species. S-RNases are thought to function as specific cytotoxins that inhibit pollen that has an S-haplotype that matches one of those in the pistil. Thus, pollen and pistil factors interact to prevent mating between closely related individuals. Other pistil factors, such as HT-B, 4936-factor and the 120 kDa glycoprotein, are also required for pollen rejection but do not contribute to S-haplotype-specificity per se. Here we show that S-RNase is taken up and sorted to a vacuolar compartment in the pollen tubes. Antibodies to the 120 kDa glycoprotein label the compartment membrane. When the pistil does not express HT-B or 4936-factor, S-RNase remains sequestered, unable to cause rejection. Similarly, in wild-type pistils, compatible pollen tubes degrade HT-B and sequester S-RNase. We suggest that S-RNase trafficking and the stability of HT-B are central to S-specific pollen rejection. 相似文献
176.
少于一半的博士毕业生朝着职业学术研究的方向发展,随着工商业中的机会的增长,他们所学的一系列有用的技能正日益被用于别处,今天的博士毕业生只有少数能真正指望在大学研究工作中长期任职,这已被包括美国国家科学院(NAS)和国家科学基金会(NSF)的研究组织以及英国政府证实。在美国,仅三分之一得到博士学位的人能指望进入学术研究体系。尽管由于其它领域的需求足够有力,从而使博士的总的失业率相对较低。而学生们正相应地调整他们的期望,考虑学术研究领域以外的职业道路。美国科学工程和政府策略委员会(COSEPUP)报告说,… 相似文献