Perception of apparent motion in the common toad

A simple and inexpensive apparatus makes possible the feeding of nonliving objects to the toad. The device is used to demonstrate the perception of apparent or "induced" motion. Two methods are successful: (i) toad and food moving together at a constatnt velocity in a stationary environment; (ii) toad and food stationary with the environment moving. The phenomena are similar to those found in human beings.     

Fast backprojections from the motion to the primary visual area necessary for visual awareness

Much is known about the pathways from photoreceptors to higher visual areas in the brain. However, how we become aware of what we see or of having seen at all is a problem that has eluded neuroscience. Recordings from macaque V1 during deactivation of MT+/V5 and psychophysical studies of perceptual integration suggest that feedback from secondary visual areas to V1 is necessary for visual awareness. We used transcranial magnetic stimulation to probe the timing and function of feedback from human area MT+/V5 to V1 and found its action to be early and critical for awareness of visual motion.     

Moving visual scenes influence the apparent direction of gravity

When an observer views a wide-angled display rotating around his line of sight, he both feels his body tilted and sees a vertical straight edge tilted opposite to the moving stimulus. Displacement of the perceived vertical increases with stimulus speed to reach a maximum (averaging 15 degrees) at 30 degrees per second.     

Optomotor response in human infants to apparent motion: evidence of innateness

Human infants were placed inside a stationary cylinder containing a columnar pattern like that used to elicit the optokinetic reflex. By sequential illumnination of the columns, the pattern was made to appear to rotate. Optokinetic nystagmus was clearly evoked in 64.7 percent of the subjects, with a weak-positive response in an additional 11.8 percent.     

Effect of interruption of the visual pathway on the response to geniculate stimulation

Optic nerve section or destruction of the lateral geniculate nucleus increased the amplitude and elevated the recovery cycle of the cortical response to lateral geniculate radiation stimulation in cats. The lesions may have acted by eliminating tonic inhibitory or occlusive volleys originating in the retina, or both.     

Measurement of a visual motion aftereffect in the rhesus monkey

A monkey was trained to discriminate between a shrinking and expanding test figure presented after steady fixation of the center of a rotating spiral. Differential shifts in the animal's perception of size constancy were found for clockwise and counter-clockwise rotation of the spiral. The magnitude of the aftereffect was within the range found in human subjects.     

Representation of visual gravitational motion in the human vestibular cortex

How do we perceive the visual motion of objects that are accelerated by gravity? We propose that, because vision is poorly sensitive to accelerations, an internal model that calculates the effects of gravity is derived from graviceptive information, is stored in the vestibular cortex, and is activated by visual motion that appears to be coherent with natural gravity. The acceleration of visual targets was manipulated while brain activity was measured using functional magnetic resonance imaging. In agreement with the internal model hypothesis, we found that the vestibular network was selectively engaged when acceleration was consistent with natural gravity. These findings demonstrate that predictive mechanisms of physical laws of motion are represented in the human brain.     

Multiple spectral inputs improve motion discrimination in the Drosophila visual system

Color and motion information are thought to be channeled through separate neural pathways, but it remains unclear whether and how these pathways interact to improve motion perception. In insects, such as Drosophila, it has long been believed that motion information is fed exclusively by one spectral class of photoreceptor, so-called R1 to R6 cells; whereas R7 and R8 photoreceptors, which exist in multiple spectral classes, subserve color vision. Here, we report that R7 and R8 also contribute to the motion pathway. By using electrophysiological, optical, and behavioral assays, we found that R7/R8 information converge with and shape the motion pathway output, explaining flies' broadly tuned optomotor behavior by its composite responses. Our results demonstrate that inputs from photoreceptors of different spectral sensitivities improve motion discrimination, increasing robustness of perception.     

农业科技期刊标注“作者贡献声明”的必要性探讨

对农业科技期刊中作者署名不规范现象进行总结的基础上,分析了造成署名不规范的原因,提出了农业科技期刊刊出“作者贡献声明”的可行性和必要性,认为“作者贡献声明”可以起到规范作者署名,减少文章刊出后引发的纠纷和撤稿的现象。     

Contributions of bird studies to biology

Birds are widely distributed, highly diversified, and exhibit behavior and social organizations equal in complexity to mammals, yet they are generally more conspicuous and approachable in natural environments. These attributes make birds excellent subjects in many areas of biological research. The topics in which studies on birds have figured prominently include the mechanisms of species formation, the regulation of the distribution and abundance of animals, the effects of the environment on behavior and physiology, the biological and evolutionary significance of variations in social organizations, the encoding of information in animal communication, the sensory basis for migration and navigation, the effects of hormones on nerve cells and behavior, the ontogeny of brain and behavior, and the structure and function of the vertebrate brain. The outstanding record of avian research suggests that birds will continue to provide important models for developing and testing new ideas in various fields of biology.     

Contributions of 1890 schools to rural development

This article concentrates on 1890 land-grant colleges' and universities' contributions to rural development in 16 southern and border states. The author contends that lifting rural dwellens out of ignorance and poverty has been a major objective of 1890 institutions. During the early years the 1890s sent out change-agents to encourage rural dwellers to improve their standard of living through education and self-help programs. These agents went into rural communities and taught farm families to raise better crops and livestock; improve their homes, schools, and community life; and despite inadequate funding of teaching, research, and extension at these schools, the 1890 schools made significant contributions to rural development. Moreover, the writer contends that the 1890 schools are not outmoded, but essential to rural development and to the education of American citizens during the rest of the 1990s and into the 21st century.     

Direct pathway to the brain

Whole-body autoradiographic stuidies demonstrated that, when isotopically labeled glucose is placed in the ligated oropharynx, there is a rapid movement of the isotope directly to the intracranial cavity. This passage involves nonspecific diflision, bypassing all recognized rouctes to the brain.     

Contributions of conventional plant breeding to food production

Within a relatively short geological time frame, Neolithic man, or more probably woman, domesticated all the major cereal grains, legumes, and root crops that the world's people depend on for most of their calories and protein. Until very recently, crop improvement was in the hands of farmers. The cornerstones of modern plant breeding were laid by Darwin and Mendel in the late 19th century. As the knowledge of genetics, plant pathology, and entomology have grown during the 20th century, plant breeders have made enormous contributions to increased food production throughout the world. There have been major plant breeding break-throughs for maize and wheat, and promising research activities to raise yields in marginal production environments are ongoing. Since it is doubtful that significant production benefits will soon be forthcoming from the use of genetic engineering techniques with higher plants, especially polyploid species, most research funds for crop improvement should continue to be allocated for conventional plant breeding research.     

关于提升农业高校科技贡献力的思考

为了完成好科教兴农和社会主义新农村建设的伟大工程,需要充分发挥农业高校的科技贡献力,农业高校的人才,技术和资源优势是显而易见的.但是也应该认识到农业高校科研工作存在的种种不足和问题,主要原因是农业经济弱势的长期影响、教师科研积极不高、人才流失严重、科研条件制约、与企业合作不力等,并相应地从抓机遇、抓管理、抓人才、抓团队、抓合作等五个方面提出了对策和建议,以期对农业高校搞好科研事业,提升科技贡献力有所裨益.     

资本市场对我国经济增长贡献的研究

采用AK模型和因子分析方法研究了我国资本市场和经济增长的关系,发现我国资本市场对经济增长贡献最大的是中长期信贷市场,股票市场和债券市场对我国的经济增长未尽到应有的作用.并发现其原因在于我国股市"为国有大中型企业服务"的畸形定位所造成的股市不规范以及债券市场规模过小,期限结构不合理等.提出了积极稳妥地推进国有股、法人股流通,加快发展证券投资基金,调整债券交易品种和期限结构,实行国有大中型商业银行股份制改造,以促进我国经济增长的政策建议.