精子介导转基因技术的进展与争论

随着生物医学的不断发展,精子介导转基因技术正成为有希望的转基因方法。与其他基因转移方法相比,精子介导具有简单、高效、低廉、安全的特点。我们探讨精子结合外源DNA和DNA内化的分子模型,介绍精子介导转基因技术的改进方法,并指出存在的问题和伦理学争论,旨在推动该技术在生物技术领域的进一步发展。     

A derived transfer of functions and the implicit association test

Participants were trained in a series of interrelated conditional discriminations that aimed to establish four 4-member equivalence classes (i.e., A1-B1-C1-D1, A2-B2-C2-D2, A3-B3-C3-D3, A4-B4-C4-D4). During this training, the four A stimuli (i.e., A1, A2, A3, and A4) were compounded with pictures containing positive or negative evaluative functions (A1/A2 negative & A3/A4 positive). The transfer of evaluative functions to directly and indirectly related members of the equivalence classes (i.e., B, C, and D stimuli) was measured using an Implicit Association Test (IAT). During consistent test blocks, participants were required to press the same response key for target words that were related to those A stimuli that possessed similar evaluative functions (A1/A2-left key & A3/A4-right key). During inconsistent test blocks, target words that were related to those A stimuli with different evaluative functions were assigned to the same response key (A1/A4-left key & A2/A3-right key). Results showed that all 8 participants, who passed a matching-to-sample equivalence test following the IAT, responded more rapidly on consistent relative to inconsistent test blocks. This typical IAT effect was not observed for those participants who did not pass the equivalence test. The results suggest that the IAT effect may arise from formally untested derived relations, and supports the argument that such relations could provide a valid behavioral model of semantic categories in natural language.     

材料规则难度对内隐与外显协同学习的影响

选取两种规则难度的人工语法字母串.采用强分离的实验程序,探索了材料规则难度对内隐学习、内隐与外显的协同学习的影响.结果显示: (1)规则难度较大的限定状态人工语法学习中,内隐学习成绩显著好于外显学习;而在难度较小的双条件语法学习中,外显学习显著好于内隐学习. (2)在两种规则难度的材料学习中,内隐与外显的协同学习成绩均好于单独的内隐或者外显学习,具有优势效应. (3)内隐学习获得的规则知识具有可迁移性.     

名人广告效果的制约因素研究述评

系统回顾了影响名人广告效果的因素,指出名人广告的效果受名人可信度的影响,名人可信度包括吸引力、专业性与可靠性3个要素,专业性与可靠性对名人广告的效果具有积极的影响,吸引力对广告效果的影响受名人与商品的一致性以及消费者的精细加工水平的制约,精细加工可能性模型与意义迁移模型进一步说明了名人广告对消费者产生影响的具体过程,在名人广告中名人形象与商品形象的一致性是影响广告效果的决定性因素。     

文章结构因素对问题解决迁移影响的研究

探讨阅读过程中文章结构因素对问题解决迁移效果的影响。实验1是在两篇源文章问题解决原理相同条件下探讨其结构类似与否对目标文章的问题解决迁移的影响。结果表明,源文章间结构越不类似,越能促进目标作业问题解决的迁移。实验2是探讨实验1中时间顺序和地理位置两种文章结构在问题解决中是否存在偏性,从而考察实验1的结论是否得以成立。结果证明,时间顺序和地理位置两种文章的组织结构不存在偏性。因而结果可初步表明,文章信息的不同的组织结构方式能促进相同原理条件下的问题解决的迁移。     

规则多边图形的离散度与图形信号认知绩效的关系

用实验方法研究规则多边图形的离散度与图形信号认知绩效的关系。实验的自变量是图形的离散度参数,因变量是单位时间图形信号的视觉通道信息传递量。实验的刺激材料是２５个离散度为０．３～０．７的规则多边图形。刺激材料的呈现与被试的反应记录都由计算机控制。结果表明：离散度适中（０．５左右）及偏小的图形信号认知绩效较高,离散度从０．５增大到０．６,认知绩效迅速下降,离散度继续增大,认知绩效仍有下降,但趋势平缓。     

Transfer of hue matching in pigeons.

Pigeons were trained on a modified three-key matching-to-sample procedure, in which only one comparison key (rather than two) was lighted after an observing response to the center-key standard. Pecks on keys of matching comparison hues were reinforced. When non-matching hues appeared as the initially lighted comparisons, the nonmatching hue terminated and the matching hue appeared on the other side key only if the pigeon did not peck the nonmatching comparison for 4.8 sec. Pecks to the nonmatching hue reset the 4.8-sec delay interval. Three hues were used during acquisition. During transfer tests, two novel hues were substituted individually or together for one or two of the training hues. Latencies to the novel side-key hue were shortest when a novel matching hue appeared as the standard on the center key, and were essentially identical to baseline matching latencies. In contrast, when a novel hue appeared as either a standard or comparison in a nonmatching combination, latencies increased with increasing separation between the noevel hue and the nonmatching hue. These transfer data demonstrate the concept of hue matching.     

Acquisition and maintenance of autoshaped key pecking as a function of food stimulus and key stimulus similarity.

The results of a number of recent studies suggest that acquisitions of autoshaped key pecking in pigeons is affected by the similarity of the grain-hopper stimulus and response-key stimulus. In Experiment 1 this hypothesis was tested by training independent groups of pigeons to key peck under six different hopper-stimulus and key-stimulus similarity conditions, and three procedures containing either immediate reinforcement, variable delay of reinforcement, or omission of reinforcement for key pecking. Number of trials to acquisition was found to be related to the similarity variable. Maintained responding was affected by the response-reinforcer contingency. This effect was found both within and between subjects. Under two of the contingencies (automaintenance and omission), maintained responding continued to be affected by the similarity of the hopper stimulus and key stimulus. In Experiment 2 pigeons were given omission training with a hopper light on or off. Both acquisition and maintenance of key pecking were facilitated by the presence of the hopper light. The present findings suggest that much of the responding reported in various automatic shaping and training procedures may reflect the effects of key stimulus/food stimulus similarity.     

GENERALIZATION AND TRANSFER BETWEEN COMPREHENSION AND PRODUCTION: A COMPARISON OF RETARDED AND NONRETARDED PERSONS

The study compared the acquisition, generalization, transfer, and maintenance of language comprehension and production responses by persons at two IQ levels: mentally retarded (N = 10) and nonretarded (N = 10). The two levels of the IQ Level factor were combined factorially with two levels of a Training Condition factor: Comprehension-Production and Production Only. Participants in the former groups were trained sequentially to (a) comprehend coin labels by pointing, and then (b) produce verbally the correct coin label. Participants in the Production Only groups were trained on the latter response only. A three-factor mixed design with one repeated measure plus a multiple baseline across coin responses was employed. Results indicated that both mentally retarded and nonretarded subjects attained a high level of acquisition and maintained their performance on 1- and 4-week follow-up tests. No difference occurred between mentally retarded and nonretarded participants in magnitude of acquisition, but the mentally retarded groups took approximately three times as many trials to complete training. Data also suggested, contrary to past research, that generalization from comprehension to production was bidirectional, with no difference in magnitude between mentally retarded and nonretarded subjects. Transfer from comprehension to production occurred in both nonretarded and retarded subjects; comprehension training facilitated a savings of trials in production training. These results show that language differences between retarded and nonretarded persons are quantitative rather than qualitative as some past research may have suggested.     

Computerized cognitive training during physical inactivity improves executive functioning in older adults

The hippocampus is closely tied to spatial navigation, a central component in cognitive functioning, and critically involved in age-associated cognitive decline and dementia. This study evaluated a novel, cognitive computerized spatial navigation training (CSNT) program targeting the hippocampus, with expectation of mitigating possible cognitive decline with bed rest (BR). During a 14-day BR study with 16 healthy, older men (mean age = 60 ± 3, range = 55–65 years), half received CSNT for 12 days in 50-min sessions and half were controls (watching documentaries). This design uniquely controlled diet, sleep, and other personal and environmental activities. Although there were no cognitive declines in controls post-BR, CSNT participants demonstrated significant increases in executive/attention ability and processing speed, and continued spatial navigation testing showed improvement to 400 days post-BR. This intervention may prove useful to mitigate cognitive declines known to occur in long periods of immobilization and could have broader implications in protecting against age-related cognitive decline.