Symmetry perception in an insect

Symmetrical visual patterns have a salient status in human perception, as evinced by their prevalent occurrence in art, and also in animal perception, where they may be an indicator of phenotypic and genotypic quality. Symmetry perception has been demonstrated in humans, birds, dolphins and apes. Here we show that bees trained to discriminate bilaterally symmetrical from non-symmetrical patterns learn the task and transfer it appropriately to novel stimuli, thus demonstrating a capacity to detect and generalize symmetry or asymmetry. We conclude that bees, and possibly flower-visiting insects in general, can acquire a generalized preference towards symmetrical or, alternatively, asymmetrical patterns depending on experience, and that symmetry detection is preformed or can be learned as perceptual category by insects, because it can be extracted as an independent visual pattern feature. Bees show a predisposition for learning and generalized symmetry because, if trained to it, they choose it more frequently, come closer to and hover longer in front of the novel symmetrical stimuli than the bees trained for asymmetry do for the novel asymmetrical stimuli. Thus, even organisms with comparatively small nervous systems can generalize about symmetry, and favour symmetrical over asymmetrical patterns.     

Practising orientation identification improves orientation coding in V1 neurons

The adult brain shows remarkable plasticity, as demonstrated by the improvement in fine sensorial discriminations after intensive practice. The behavioural aspects of such perceptual learning are well documented, especially in the visual system. Specificity for stimulus attributes clearly implicates an early cortical site, where receptive fields retain fine selectivity for these attributes; however, the neuronal correlates of a simple visual discrimination task remained unidentified. Here we report electrophysiological correlates in the primary visual cortex (V1) of monkeys for learning orientation identification. We link the behavioural improvement in this type of learning to an improved neuronal performance of trained compared to naive neurons. Improved long-term neuronal performance resulted from changes in the characteristics of orientation tuning of individual neurons. More particularly, the slope of the orientation tuning curve that was measured at the trained orientation increased only for the subgroup of trained neurons most likely to code the orientation identified by the monkey. No modifications of the tuning curve were observed for orientations for which the monkey had not been trained. Thus training induces a specific and efficient increase in neuronal sensitivity in V1.     

扩大篮球运动员视野的实验研究

篮球运动员视野大小直接关系到其运用篮球技术、战术的合理性与有效性。文章采用对照实验法,通过对对照组不施加任何实验因素,对三个实验组分别施加不同的实验因素,探求扩大篮球运动员视野的可能性及其程度。结果表明:篮球运动员的视野不是一成不变而是可以扩大的;采用多种手段比单一手段能更有效地扩大篮球运动员的视野。     

Neural correlates of short-term perceptual learning in orientation discrimination indexed by event-related potentials

The current work investigated the neural correlates of visual perceptual learning in grating orientation discrimination by recording event-related potentials (ERPs) from human adults. Subjects were trained with a discrimination task of grating orientation in three consecutive training sessions within 2 h. While reaction times (RTs) were shortened gradually across training sessions, the N1 was decreased and the P2 was increased over the parietal and occipital areas. A broadly distributed P3 was increased along with more practices. In addition, the time course of learning reflected in the P2 and P3 amplitudes was in line with the changes of reaction times and exhibited a stable level during later training. The impli- cations of these results to the neural mechanisms subserving perceptual learning were discussed.     

培养少年篮球运动员的三步曲

优秀少年篮球运动员培养的实践表明，科学选材、全面扎实的基本技术和身体素质训练、以及从小养成良好的打篮球习惯是成功必不可少的三步曲。     

开放实验室培养本科学生能力的初步探索

开放实验室是本科生能力培养的重要途径,本文根据几年来开放实验室工作的实践,论述了通过开放实验促进本科学生基本技能和创新能力培养的意义和方法。初步探索的结果证明:开放实验室研学不仅能使学生基本技能、科研能力和创新能力得到培养,而且能使本科生在开放实验室的研学中获得创新学分,促进考研和就业。     

足球启蒙训练应从运控球技术开始学习

足球是世界第一运动,由于它的对抗性强,竞争激烈,场上变化莫测,从而使众多青少年儿童对足球产生了浓厚的兴趣,纵观世界足球发展史,高水平的足球运动员都是从青少年开始训练,所以,我们必须从娃娃抓起,这样才能使我国的足球运动水平跻身世界强国之列.初学足球的少年、儿童怎样培养这是我们乔老师、教练员共同关心研究的问题.我认为青少年儿童足球训练应从运控球技术开始学习,才能取得最佳的训练效果.     

打击乐器演奏教学法初探

打击乐器演奏是幼儿学习音乐的重要途径之一。但是，教师们普遍感到打击乐器演奏教学难以进行。文章主要从教师的角度阐述打击乐器演奏的教学方法，有效地提高打击乐器演奏的教学质量，使枯燥、困难的打击乐器演奏教学变得轻松、愉快而富有乐趣。     

Self-organizing neural network that discovers surfaces in random-dot stereograms.

The standard form of back-propagation learning is implausible as a model of perceptual learning because it requires an external teacher to specify the desired output of the network. We show how the external teacher can be replaced by internally derived teaching signals. These signals are generated by using the assumption that different parts of the perceptual input have common causes in the external world. Small modules that look at separate but related parts of the perceptual input discover these common causes by striving to produce outputs that agree with each other. The modules may look at different modalities (such as vision and touch), or the same modality at different times (for example, the consecutive two-dimensional views of a rotating three-dimensional object), or even spatially adjacent parts of the same image. Our simulations show that when our learning procedure is applied to adjacent patches of two-dimensional images, it allows a neural network that has no prior knowledge of the third dimension to discovery depth in random dot stereograms of curved surfaces.     

Attentional modulation in visual cortex depends on task timing

Paying attention to a stimulus selectively increases the ability to process it. For example, when subjects attend to a specific region of a visual scene, their sensitivity to changes at that location increases. A large number of studies describe the behavioural consequences and neurophysiological correlates of attending to spatial locations. There has, in contrast, been little study of the allocation of attention over time. Because subjects can anticipate predictable events with great temporal precision, it seems probable that they might dynamically shift their attention when performing a familiar perceptual task whose constraints changed over time. We trained monkeys to respond to a stimulus change where the probability of occurrence changed over time. Recording from area V4 of the visual cortex in these animals, we found that the modulation of neuronal responses changed according to the probability of the change occurring at that instant. Thus, we show that the attentional modulation of sensory neurons reflects a subject's anticipation of the timing of behaviourally relevant events.     

Context-enabled learning in the human visual system

Training was found to improve the performance of humans on a variety of visual perceptual tasks. However, the ability to detect small changes in the contrast of simple visual stimuli could not be improved by repetition. Here we show that the performance of this basic task could be modified after the discrimination of the stimulus contrast was practised in the presence of similar laterally placed stimuli, suggesting a change in the local neuronal circuit involved in the task. On the basis of a combination of hebbian and anti-hebbian synaptic learning rules compatible with our results, we propose a mechanism of plasticity in the visual cortex that is enabled by a change in the context.     

方位辨别知觉学习的眼传递及空间频率调谐特性

为了研究方位辨别知觉学习的神经机制,采用心理物理的方法,研究了方位辨别知觉学习的空间频率调谐与眼传递特性.通过对9个被试在固定空间频率（周期/度）进行方位辨别的训练,并于训练前后在多个空间频率（0.5, 1, 2, 4, 8, 16和32周期/度）测量方位辨别的阈值,发现被试在训练空间频率的方位辨别阈值平均下降了7.01 dB,并且这种学习效应可显著传递到非训练眼.学习效应可分为两个部分：一部分可传递到其他空间频率（4.10 dB）,另外一部分则特异于训练空间频率（2.95 dB）.这些结果说明方位辨别学习可能发生在双眼信息汇聚之后的视皮层,且可能有多种机制参与其中.     

谷氨酸AMPA受体拮抗剂CNQX对大鼠颠倒学习的影响

研究利用旋转T迷宫装置,通过食物强化,分别训练大鼠视觉辨别学习和颠倒学习任务;每次训练前均向动物腹腔注射20μg/kg的谷氨酸AMPA受体拮抗剂CNQX,以考察其对大鼠学习能力的影响.结果发现,CNQX并不影响正常学习,但对于颠倒学习,CNQX注射组的学习次数较控制组显著增加,说明CNQX可以对大鼠的认知灵活性造成损害.     

Visual place learning in Drosophila melanogaster

The ability of insects to learn and navigate to specific locations in the environment has fascinated naturalists for decades. The impressive navigational abilities of ants, bees, wasps and other insects demonstrate that insects are capable of visual place learning, but little is known about the underlying neural circuits that mediate these behaviours. Drosophila melanogaster (common fruit fly) is a powerful model organism for dissecting the neural circuitry underlying complex behaviours, from sensory perception to learning and memory. Drosophila can identify and remember visual features such as size, colour and contour orientation. However, the extent to which they use vision to recall specific locations remains unclear. Here we describe a visual place learning platform and demonstrate that Drosophila are capable of forming and retaining visual place memories to guide selective navigation. By targeted genetic silencing of small subsets of cells in the Drosophila brain, we show that neurons in the ellipsoid body, but not in the mushroom bodies, are necessary for visual place learning. Together, these studies reveal distinct neuroanatomical substrates for spatial versus non-spatial learning, and establish Drosophila as a powerful model for the study of spatial memories.     

Signal but not noise changes with perceptual learning

Perceptual discrimination improves with practice. This 'perceptual learning' is often specific to the stimuli presented during training, indicating that practice may alter the response characteristics of cortical sensory neurons. Although much is known about how learning modifies cortical circuits, it remains unclear how these changes relate to behaviour. Different theories assume that practice improves discrimination by enhancing the signal, diminishing internal noise or both. Here, to distinguish among these alternatives, we fashioned sets of faces and textures whose signal strength could be varied, and we trained observers to identify these patterns embedded in noise. Performance increased by up to 400% across several sessions over several days. Comparisons of human performance to that of an ideal discriminator showed that learning increased the efficiency with which observers encoded task-relevant information. Observer response consistency, measured by a double-pass technique in which identical stimuli are shown twice in each experimental session, did not change during training, showing that learning had no effect on internal noise. These results indicate that perceptual learning may enhance signal strength, and provide important constraints for theories of learning.     

Perceptual learning of dot pattern

Dot pattern is a type of pattern defined by specific spatial relationship among some dots. As a compensation for concrete and meaningful visual stimuli, meaningless dot pattern can be used as stimuli in learning tasks. We performed an experiment for exploring the perceptual learning process of dot pattern against random-dot background. Participants were required to learn two types of dot patterns (9-dot and 11-dot). They were assigned to two groups: participants in Group 1 learned 9-dot pattern first and 11-dot pattern later, while those in Group 2 learned 11-dot pattern first and 9-dot pattern later. The results showed that participants could acquire the spatial relationship of dot pattern through perceptual learning in relatively short learning time. In comparison with 9-dot pattern, learning time of 11-dot pattern was slightly longer and its accuracy rate lower, but there was significant positive transfer effect from 11-dot pattern learning to 9-dot learning.     

Perceptual learning of dot pattern

Dot pattern is a type of pattern defined by specific spatial relationship among some dots. As a compensation for concrete and meaningful visual stimuli, meaningless dot pattern can be used as stimuli in learning tasks. We performed an experiment for exploring the perceptual learning process of dot pattern against random-dot background. Participants were required to learn two types of dot patterns (9-dot and 11-dot). They were assigned to two groups: participants in Group 1 learned 9-dot pattern first and 11-dot pattern later, while those in Group 2 learned 11-dot pattern first and 9-dot pattern later. The results showed that participants could acquire the spatial relationship of dot pattern through perceptual learning in relatively short learning time. In comparison with 9-dot pattern, learning time of 11-dot pattern was slightly longer and its accuracy rate lower, but there was significant positive transfer effect from 11-dot pattern learning to 9-dot learning.     

Eye-specific effects of binocular rivalry in the human lateral geniculate nucleus

When dissimilar images are presented to the two eyes, they compete for perceptual dominance so that each image is visible in turn for a few seconds while the other is suppressed. Such binocular rivalry is associated with relative suppression of local, eye-based representations that can also be modulated by high-level influences such as perceptual grouping. However, it is currently unclear how early in visual processing the suppression of eye-based signals can occur. Here we use high-resolution functional magnetic resonance imaging (fMRI) in conjunction with a new binocular rivalry stimulus to show that signals recorded from the human lateral geniculate nucleus (LGN) exhibit eye-specific suppression during rivalry. Regions of the LGN that show strong eye-preference independently show strongly reduced activity during binocular rivalry when the stimulus presented in their preferred eye is perceptually suppressed. The human LGN is thus the earliest stage of visual processing that reflects eye-specific dominance and suppression.     

钢琴曲《水的嬉戏》演奏技术的内容分析与弹奏方法研究

《水的嬉戏》是拉威尔早期创作的代表作品之一,是拉威尔钢琴音乐风格形成过程中一部里程碑式的作品,自称之为“一切创新的起源”。这是一首音画式的描述性作品,拉威尔运用了各种音型织体来描述“水”的形象。笔者主要对作品演奏技术与弹奏方法进行分析研究,试图通过总结表现音乐所需要的技巧和归纳演奏这首作品的要点和难点,展现这首音乐作品的艺术内涵,给演奏者提供有参考价值的建议。