昆虫额神经节的神经网络结构及功能

额神经节是昆虫神经系统中的重要结构,它参与昆虫的羽化、蜕皮等多种生理行为的调节,在昆虫的生理生态中发挥重要的作用。研究额神经节的神经网络结构及功能对理解昆虫的生理学机制有重要科学意义。综述近年来关于额神经节研究的最新研究成果及进展,围绕额神经节神经网络的结构和功能展开,主要论述了额神经节的解剖学位置、形态结构、组织发育、神经元的种类、运动神经元的类型、与其他神经组织的联系的神经网络结构以及调节昼夜节律、控制前肠肌的自律性运动、控制蛋白质的新陈代谢和调控心跳等的各种生理功能。并提示额神经节可能是一个内分泌器官,通过分泌神经调节因子发挥作用,对其神经机制的进一步研究将是额神经节今后的研究方向和发展趋势。     

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.     

The concepts of 'sameness' and 'difference' in an insect

Insects process and learn information flexibly to adapt to their environment. The honeybee Apis mellifera constitutes a traditional model for studying learning and memory at behavioural, cellular and molecular levels. Earlier studies focused on elementary associative and non-associative forms of learning determined by either olfactory conditioning of the proboscis extension reflex or the learning of visual stimuli in an operant context. However, research has indicated that bees are capable of cognitive performances that were thought to occur only in some vertebrate species. For example, honeybees can interpolate visual information, exhibit associative recall, categorize visual information and learn contextual information. Here we show that honeybees can form 'sameness' and 'difference' concepts. They learn to solve 'delayed matching-to-sample' tasks, in which they are required to respond to a matching stimulus, and 'delayed non-matching-to-sample' tasks, in which they are required to respond to a different stimulus; they can also transfer the learned rules to new stimuli of the same or a different sensory modality. Thus, not only can bees learn specific objects and their physical parameters, but they can also master abstract inter-relationships, such as sameness and difference.     

苹果受粉前后子房的生化变化

本文报道了苹果受粉前后子房内Ｐｒ／ＲＮＡ、蛋白水解酶活性及过氧化物同工酶的变化．花开后６ｄ，受粉子房Ｐｒ／ＲＮＡ维持在较高水平，未受粉子房则是在花开３ｄ时比值升高，到６ｄ时该比值又降低；蛋白水解酶活性的变化相似于Ｐｒ／ＲＮＡ值在上述两种材料中的变化情况；与未受粉子房相比，受粉子房在受粉后新出现了两条大分子量的过氧化物同工酶带．本文还对受粉与否所引起不同的发育途径及蛋白水解酶活性、过氧化物同工酶变化与子房发育的关系作了初步探讨．     

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.     

Substrate phosphoprotein availability regulates eclosion hormone sensitivity in an insect CNS

The final step in the moulting of all insects is ecdysis, the shedding of the cuticle of the previous instar, which is triggered in Lepidoptera by the neurosecretory peptide eclosion hormone. This hormone acts directly on the nervous system to release the appropriate motor patterns for larval, pupal and adult ecdysis, but there are only brief periods near the end of each moult when the nervous system is competent to respond to the hormone. Previous experiments have shown that the action of eclosion hormone on the nervous system at pupal ecdysis in the tobacco hornworm, Manduca sexta, is mediated by the second messenger cyclic GMP. Here we report that the hormone-stimulated increase in cGMP results in the phosphorylation of two proteins, each with an apparent relative molecular mass (Mr) of 54,000. Moreover, the brief periods during which the central nervous system (CNS) is responsive to eclosion hormone seem to result from the transient presence of these substrate proteins within the nervous system. This provides a novel mechanism by which hormonal responsiveness can be regulated.