Neurolinguistics: structural plasticity in the bilingual brain

Humans have a unique ability to learn more than one language--a skill that is thought to be mediated by functional (rather than structural) plastic changes in the brain. Here we show that learning a second language increases the density of grey matter in the left inferior parietal cortex and that the degree of structural reorganization in this region is modulated by the proficiency attained and the age at acquisition. This relation between grey-matter density and performance may represent a general principle of brain organization.     

Developmental plasticity in the visual and auditory representations in the mammalian superior colliculus

Environmental factors play an important role in certain aspects of the development of sensory systems. But the way in which the maturation of different sensory modalities is coordinated is poorly understood. We have investigated this question neurophysiologically in the mammalian superior colliculus (SC), which contains topographically aligned maps of visual and auditory space. We report here that an essentially normal auditory map, in approximate register with the visual map, is found in the SC of adult ferrets reared with abnormal binaural localization cues. Also, if, early in life, one eye is deviated laterally, there is a compensatory shift in the auditory map, but early eye rotation totally disorders the auditory representation. These results imply that development of the auditory map is affected by visual activity or by information about eye position and that there is definite, but limited, capacity for the auditory map to reorganize so that it remains aligned with the visual map.     

Analysis of mammalian brain architecture.

The mammalian brain is composed of several distinct parts which show different growth in evolution. Clark, Mitra and Wang found that the two main cortices of the brain - the cerebral (neo-) cortex and the cerebellum - show very different growth, and that whereas the ratio of neocortex volume to total brain volume increases with evolution, the cerebellum occupies a constant proportion in different species. Here I compare the surface areas of the two cortices in different species and find that these show a simple proportionality. Contrary to the conclusion drawn by Clark et al., this linear dependence of size implies that the two major cortices increase their computational capacity in parallel, suggesting a functional dependence of the one upon the other.     

Presynaptic mechanism for long-term potentiation in the hippocampus

Experiments analysing the statistical properties of synaptic transmission, before and after the induction of long-term potentiation (LTP), suggest that expression of LTP largely arises in a presynaptic mechanism--an increased probability of transmitter release.     

Occurrence and extracellular actions of inositol pentakis- and hexakisphosphate in mammalian brain

Although inositol 1,3,4,5,6-pentakisphosphate (InsP5) and hexakisphosphate (InsP6) have been recognized for some time as naturally-occurring metabolites of inositol, their occurrence in mammalian cell types, including one of neural origin, has only recently been documented. This is of interest because of the recognized second messenger role of inositol 1,4,5-trisphosphate (InsP3) in intracellular signalling; coupling surface stimuli to cytoplasmic calcium discharge. The metabolism, existence in normal mature tissues, and possible functional roles of these inositol polyphosphates are unknown. Here we report evidence that InsP5 and InsP6 are synthesized in intact brain after labelling with [3H]inositol in vivo. We also show that local infusion of InsP5 and InsP6 into a discrete brain stem nucleus implicated in cardiovascular regulation, results in dose-dependent changes in heart rate and blood pressure.     

最优联想映射噪声衰减因子的计算

在常见的一些多元分布的情况下,对最优联想映射中的随机噪声Ｖ衰减因子作了研究,结果表明,当随机噪声Ｖ的密度函数可交换时噪声衰减因子为√ｍ／ｎ,而Ｋｏｈｏｎｅｎ等人在「１」,「２」中曾用了大量的篇幅所证得的结论仅为本文所得结果的一种特例。本文对非对称多元正态分布及非对称椭球分布情形下噪声衰减因子的研究表明,此时衰减因子不再是√ｍ／ｎ。     

∧结合BCI-代数的性质

本文确立了A结合BCI-代数的若干性质。     

论联想思维能力的培养

联想思维习惯和能力是创造性人格的重要内涵之一。教师在教学中运用联想思维既可提高教学效率,又可给学生以示范。培养学生的联想思维能力的首要任务是努力培养学生的自信心,还学生以自由思维空间。     

Presynaptic release probability influences the locus of long-term potentiation.

The quantal hypothesis proposes that chemical synaptic transmission involves the probabilistic release of multimolecular packets of transmitter. Analysis of the resulting trial-to-trial fluctuations in postsynaptic response can provide estimates both of the number of quanta released and of the size of their postsynaptic effect. This in turn permits the quantification of the relative contributions of pre- and postsynaptic factors to the strength of a given synapse. Quantal analysis of excitatory synapses in the hippocampus has proved difficult and has led to contradictory conclusions when applied to long-term potentiation. Here we report the use of a combination of quantal analysis procedures to provide evidence that both pre- and postsynaptic changes can contribute substantially to the maintenance of long-term potentiation in the CA1 region of the hippocampus. The initial setting of the presynaptic release mechanism seems to determine their relative importance.     

结合代数的同调与上同调

定义了结合超代数的同调与上同调 ,证明了超代数的同调与上同调的两个同构定理 .讨论了同调与上同调的基本关系