Control of behavior by presentation of an imprinted stimulus

When presentation of an imprinted stimulus is contingent upon an arbitrarily chosen response, the rate of emission of this response increases. This control of responding requires a moving imprinted stimulus and does not require a following response by the duck.     

Primary afferent depolarization evoked by a painful stimulus

Pulses of intense radiant heat applied to the plantar pad of unanesthetized spinal cats produced negative dorsal root potentials, increased excitability of cutaneous A fibers, and marked activation of ipsilateral flexor motoneurons. The same effects were obtained during cold block of A fiber conduction in the appropriate peripheral nerve. We conclude that adequate noxious activation of cutaneous C fibers depolarizes cutaneous A fibers.     

Punishment by response-contingent withdrawal of an imprinted stimulus

Newly hatched ducklinigs were exposed to a moving, imprinted stiulullls; if they followed it, the stimnulus was withdrawn briefly. The tendency to follow gradually declined durinig punishment periods, but it returned to prepunishment amounts whlen punishmnent terminated. This finding attests to the efficacy of withdrawal of reinforcement as a techniquie for behavioral control.     

Rule learning by rats

Using rules extracted from experience to solve problems in novel situations involves cognitions such as analogical reasoning and language learning and is considered a keystone of humans' unique abilities. Nonprimates, it has been argued, lack such rule transfer. We report that Rattus norvegicus can learn simple rules and apply them to new situations. Rats learned that sequences of stimuli consistent with a rule (such as XYX) were different from other sequences (such as XXY or YXX). When novel stimuli were used to construct sequences that did or did not obey the previously learned rule, rats transferred their learning. Therefore, rats, like humans, can transfer structural knowledge from sequential experiences.     

Recovery of masked visual targets by inhibition of the masking stimulus

Theories of visual backward masking all assume that a masked target is eliminated from the visual system. Experiments on reaction time to masked signals suggest otherwise, as does a recent demonstration that a masked target can be restored to phenomenal awareness by backward masking of the target's mask. Two experiments are reported here that substantiate the possibility of recovering a masked target, by using different stimulus materials and a more elaborate design than was employed in the first demonstration of this effect.     

Glycolipid antigen processing for presentation by CD1d molecules

The requirement for processing glycolipid antigens in T cell recognition was examined with mouse CD1d-mediated responses to glycosphingolipids (GSLs). Although some disaccharide GSL antigens can be recognized without processing, the responses to three other antigens, including the disaccharide GSL Gal(alpha1-->2)GalCer (Gal, galactose; GalCer, galactosylceramide), required removal of the terminal sugars to permit interaction with the T cell receptor. A lysosomal enzyme, alpha-galactosidase A, was responsible for the processing of Gal(alpha1-->2)GalCer to generate the antigenic monosaccharide epitope. These data demonstrate a carbohydrate antigen processing system analogous to that used for peptides and an ability of T cells to recognize processed fragments of complex glycolipids.     

Sodium: stimulus for puddling behavior by tiger swallowtail butterflies, Papilio glaucus

Male Papilio glaucus butterflies are attracted to sand soaked with dillute aqueous solutions of sodium salts. A sodium ion concentration of 10(-3) molar is sufficient to stimulate puddling behavior. Acqlisition of sodiumn mnay be the main ecological function of pudding behavior.     

Predicting human interactive learning by regret-driven neural networks

Much of human learning in a social context has an interactive nature: What an individual learns is affected by what other individuals are learning at the same time. Games represent a widely accepted paradigm for representing interactive decision-making. We explored the potential value of neural networks for modeling and predicting human interactive learning in repeated games. We found that even very simple learning networks, driven by regret-based feedback, accurately predict observed human behavior in different experiments on 21 games with unique equilibria in mixed strategies. Introducing regret in the feedback dramatically improved the performance of the neural network. We show that regret-based models provide better predictions of learning than established economic models.     

Maternal influence in learning by observation in kittens

Kittens who observed their mothers perform a stimulus-controlled response (lever pressing to a visual stimulus for food) acquired and discriminated that response sooner than kittens who observed a strange female cat's performance. Kittens exposed to a trial and error condition never acquired the response. Initial differences in attentiveness to demonstrator performances disappeared by the second day. "Altruism" (food sharing) and other forms of social behavior were exhibited by both mother and stranger demonstrators.     

Instrumental learning of vasomotor responses by rats: learning to respond differentially in the two ears

Curarized and artificially respirated rats were rewarded by electrical stimulation of the brain for changes in the balance of vasomotor activity between the two ears. They learned vasomotor responses in one ear that were independent of those in the other ear, in either forepaw, or in the tail, or of changes in heart rate or temperature. In addition to implications for learning theory and psychosomatic medicine, these results indicate a greater specificity of action in the sympathetic nervous system than is usually attributed to it.     

Defective presentation of endogenous antigen by a cell line expressing class I molecules

Cytotoxic T lymphocytes (CTLs) recognize class I major histocompatibility complex (MHC) molecules associated with antigenic peptides derived from endogenously synthesized proteins. Binding to such peptides is a requirement for class I assembly in the endoplasmic reticulum (ER). A mutant human cell line, T2, assembles and transports to its surface some, but not all, class I MHC molecules. The class I molecules expressed on the surface of T2 do not present peptides derived from cytosolic antigens, although they can present exogenously added peptides to CTL. The transported class I molecules may interact weakly with an unknown retaining factor in the ER such that they can assemble despite the relative shortage of peptides.     

Associative learning in egglaying site selection by apple maggot flies

Evidence is presented demonstrating that associative learning during oviposition in Crataegus or apple hosts can significantly influence the propensity of apple maggot flies to accept or reject these hosts in future encounters. The data suggest that within resource patches of a given host type there may be an enhancement of foraging efficiency.     

Leucine-tRNA initiates at CUG start codons for protein synthesis and presentation by MHC class I

Effective immune surveillance by cytotoxic T cells requires newly synthesized polypeptides for presentation by major histocompatibility complex (MHC) class I molecules. These polypeptides are produced not only from conventional AUG-initiated, but also from cryptic non-AUG-initiated, reading frames by distinct translational mechanisms. Biochemical analysis of ribosomal initiation complexes at CUG versus AUG initiation codons revealed that cells use an elongator leucine-bound transfer RNA (Leu-tRNA) to initiate translation at cryptic CUG start codons. CUG/Leu-tRNA initiation was independent of the canonical initiator tRNA (AUG/Met-tRNA(i)(Met)) pathway but required expression of eukaryotic initiation factor 2A. Thus, a tRNA-based translation initiation mechanism allows non-AUG-initiated protein synthesis and supplies peptides for presentation by MHC class I molecules.     

非英语专业本科生英语词汇学习策略的研究

通过问卷调查、课堂观察和访谈,运用定量分析的方法,研究了240名福建农林大学非英语专业一年级学生英语词汇学习策略使用的总体状况,并对文理科大学生英语词汇学习策略使用差异进行对比分析。研究结果显示：被调查的非英语专业本科生是成熟的字典使用者,但仍然坚持传统的死记硬背和孤立使用单词表背单词。选择注意、猜测、联想、构词法等策略频繁被使用,但是其他元认知策略和社会、情感策略不常被使用。大部分被调查的学生对课堂记笔记不积极,尤其忽视分类、想象和社会策略。被调查的文理科大学生在语义联想、猜测、字典详尽使用和情感策略等4个方面存在显著差异,其诱因是不同的学习特点和学习风格。     

By carrot or by stick: cognitive reinforcement learning in parkinsonism

To what extent do we learn from the positive versus negative outcomes of our decisions? The neuromodulator dopamine plays a key role in these reinforcement learning processes. Patients with Parkinson's disease, who have depleted dopamine in the basal ganglia, are impaired in tasks that require learning from trial and error. Here, we show, using two cognitive procedural learning tasks, that Parkinson's patients off medication are better at learning to avoid choices that lead to negative outcomes than they are at learning from positive outcomes. Dopamine medication reverses this bias, making patients more sensitive to positive than negative outcomes. This pattern was predicted by our biologically based computational model of basal ganglia-dopamine interactions in cognition, which has separate pathways for "Go" and "NoGo" responses that are differentially modulated by positive and negative reinforcement.     

Extended culture of mouse embryo cells without senescence: inhibition by serum

Mouse embryo cells cultured in vitro in serum-supplemented media undergo growth crisis, resulting in the loss of genomically normal cells prior to the appearance of established, aneuploid cell lines. Mouse embryo cells established and maintained for multiple passages in the absence of serum did not exhibit growth crisis or gross chromosomal aberration. Cells cultured under these conditions were dependent on epidermal growth factor for survival. Proliferation was reversibly inhibited by serum or platelet-free plasma, suggesting that mouse embryo cultures maintained by conventional procedures are under the influence of inhibitory factors.     

借鉴国外经验 加快图书馆数字化建设

将图书馆馆藏文献实施数字化处理是实现数字化图书馆的一项重要内容，本文就这个问题进行了探讨。文章简要介绍了美国国会图书馆、日本国会图书馆国、荷兰皇家图书馆等国家图书馆实施馆藏文献数字化的方法、技术、内容等几个方面的情况，并就本单位图书馆实施馆藏文献数字化工作提出几点看法。     

借鉴国内外经验,探索本科职业教育

阐述了美国、德国、日本等国家本科职业教育的发展历史、办学模式和形式;介绍了国内本科应用型人才培养的基本情况,国家对应用型人才的需求,高职院校培养职业技术型人才的经验。从职业规划课程的设置,实施新的人才培养模式,加强"双师型"教师培养,建立实践实训基地等方面介绍了西昌学院探索本科职业教育的作法。