How did brains evolve?

Three reports on mammalian brain evolution analyse the same comparative data on brain component volumes but come to partially conflicting conclusions. Clark et al. conclude from their analysis of volumetric brain proportions ("cerebro-types") that cerebellum size is invariant across mammalian taxonomic groups, the neocortex and cerebellum do not co-vary in size (in contradiction to ref. 1), and cerebrotype-based measures identify directional changes in brain architecture. Here I provide evidence that calls each of these conclusions into question. The failure of the cerebrotype measure to identify species differences in brain architecture that are independent of gross brain size undermines the proposal by Clark et al. that it could be useful for detecting evolutionary patterns and phylogenetic relationships.     

Scalable architecture in mammalian brains

Comparison of mammalian brain parts has often focused on differences in absolute size, revealing only a general tendency for all parts to grow together. Attempts to find size-independent effects using body weight as a reference variable obscure size relationships owing to independent variation of body size and give phylogenies of questionable significance. Here we use the brain itself as a size reference to define the cerebrotype, a species-by-species measure of brain composition. With this measure, across many mammalian taxa the cerebellum occupies a constant fraction of the total brain volume (0.13 +/- 0.02), arguing against the hypothesis that the cerebellum acts as a computational engine principally serving the neocortex. Mammalian taxa can be well separated by cerebrotype, thus allowing the use of quantitative neuroanatomical data to test evolutionary relationships. Primate cerebrotypes have progressively shifted and neocortical volume fractions have become successively larger in lemurs and lorises, New World monkeys, Old World monkeys, and hominoids, lending support to the idea that primate brain architecture has been driven by directed selection pressure. At the same time, absolute brain size can vary over 100-fold within a taxon, while maintaining a relatively uniform cerebrotype. Brains therefore constitute a scalable architecture.     

Growth patterns in the developing brain detected by using continuum mechanical tensor maps

The dynamic nature of growth and degenerative disease processes requires the design of sensitive strategies to detect, track and quantify structural change in the brain in its full spatial and temporal complexity. Although volumes of brain substructures are known to change during development, detailed maps of these dynamic growth processes have been unavailable. Here we report the creation of spatially complex, four-dimensional quantitative maps of growth patterns in the developing human brain, detected using a tensor mapping strategy with greater spatial detail and sensitivity than previously obtainable. By repeatedly scanning children (aged 3-15 years) across time spans of up to four years, a rostro-caudal wave of growth was detected at the corpus callosum, a fibre system that relays information between brain hemispheres. Peak growth rates, in fibres innervating association and language cortices, were attenuated after puberty, and contrasted sharply with a severe, spatially localized loss of subcortical grey matter. Conversely, at ages 3-6 years, the fastest growth rates occurred in frontal networks that regulate the planning of new actions. Local rates, profiles, and principal directions of growth were visualized in each individual child.     

Sperm competition: motility and the midpiece in primates

In animals with multiple-partner mating systems, the gametes of two or more males must compete to fertilize a given set of ova. Here we show that the volume of the midpiece in individual sperm is significantly greater in primate species in which the females mate with multiple partners, and in which males have larger testes in relation to their body weight, than in those species that mate with only one partner and have relatively small testes. Our results indicate that sexual selection by sperm competition has influenced the evolution of a specific component of male-gamete morphology, the volume of the sperm midpiece.     

Evolutionary radiations and convergences in the structural organization of mammalian brains

The sizes of mammalian brain components seem to be mostly related to the sizes of the whole brain (and body), suggesting a one-dimensional scale of encephalization. Previous multivariate study of such data concludes that evolutionary selection for enlargement of any one brain part is constrained to selection for a concerted enlargement of the whole brain. However, interactions between structurally related pairs of brain parts confirm reports of differential change in brain nuclei, and imply mosaic rather than concerted evolution. Here we analyse a large number of variables simultaneously using multi-dimensional methods. We show that the relative proportions of different systems of functionally integrated brain structures vary independently between different mammalian orders, demonstrating separate evolutionary radiations in mammalian brain organization. Within each major order we identify clusters of unrelated species that occupy similar behavioural niches and have convergently evolved similar brain proportions. We conclude that within orders, mosaic brain organization is caused by selective adaptation, whereas between orders it suggests an interplay between selection and constraints.     

模拟5000米低氧大鼠脑内信息物质含量变化初探

利用减压舱模拟海拔５０００米低氧并采用放射免疫的方法，观察了大鼠大脑皮层和小脑内信息物质浓度的变化，并比较了两部位间的含量差异。以西宁地区海拔２２６０米作为对照，发现：高海拔低氧可引起大鼠脑内ｃＡＭＰ含量升高尤以小脑显著。     

Temporal dissociation of parallel processing in the human subcortical outputs.

Many tasks require rapid and fine-tuned adjustment of motor performance based on incoming sensory information. This process of sensorimotor adaptation engages two parallel subcorticocortical neural circuits, involving the cerebellum and basal ganglia, respectively. How these distributed circuits are functionally coordinated has not been shown in humans. The cerebellum and basal ganglia show very similar convergence of input-output organization, which presents an ideal neuroimaging model for the study of parallel processing at a systems level. Here we used functional magnetic resonance imaging to measure the temporal coherence of brain activity during a tactile discrimination task. We found that, whereas the prefrontal cortex maintained a high level of activation, output activities in the cerebellum and basal ganglia showed different phasic patterns. Moreover, cerebellar activity significantly correlated with the activity of the supplementary motor area but not with that of the primary motor cortex; in contrast, basal ganglia activity was more strongly associated with the activity of the primary motor cortex than with that of the supplementary motor area. These results demonstrate temporally partitioned activity in the cerebellum and basal ganglia, implicating functional independence in the parallel subcortical outputs. This further supports the idea of task-related dynamic reconfiguration of large-scale neural networks.     

自闭谱系障碍的大脑功能性连接研究进展

自闭谱系障碍是一种以早期社会交往上的广泛性异常、缺乏与人进行沟通的能力、异常局限的兴趣以及刻板重复性行为为特征的复杂的神经发育障碍．自闭谱系障碍的大脑功能性连接研究表明,自闭谱系障碍存在着大脑功能性连接的显著降低,这种神经同步性活动的异常与自闭谱系障碍的社交和沟通障碍的严重程度呈负相关．实验研究采用功能性近红外光谱成像技术,对自闭谱系障碍儿童静息状态下大脑皮层的功能性连接性进行测量,结果发现,自闭谱系障碍儿童的额叶和颞叶左右半球之间的功能性连接是显著降低的,而额叶和颞叶在语言加工和社会认知过程中起着重要作用．功能性近红外光谱成像技术作为一种光学脑成像技术,能够有效且可靠地揭示自闭谱系障碍的大脑异常功能性活动．     

基于复杂网络构建与分析技术的语音响度差异神经处理机制研究

相关分析能够找出研究现象之间的依存关系、相关方向以及相关程度,可以发现大数据集里隐藏的关联网络.本文面向语音响度变化认知问题,提出“差异度”的概念,利用相关分析构建大脑功能的复杂网络,探索深层的神经处理机制与脑认知新规律.提出一种短时窗分析方法,构建不同认知阶段的脑网络;基于不同刺激下节点度的拓扑特征,构建基于差异度的脑地形图,实现脑区之间数据关系的可视化表达和动态演化过程表达.结果发现,前额叶、右额颞区和右后颞区分别在听觉处理的早期、中期和晚期对声音响度变化具有显著响应.研究表明脑复杂网络构建与分析技术可以成为研究神经处理机制与认知规律的有效工具.     

山地樟子松生长特性及林分密度对其生长的影响

 樟子松是中国北方地区主要造林树种,影响其林分生长的主导因子之一是密度。研究樟子松生长特性及其与密度的相关性,对引种栽培和林分抚育管理等都有重要意义。选取内蒙古中部地区那日斯台林场为试验地,通过对高密度（>3000株/hm²）、中密度（2000~3000株/hm²）、低密度（1000~2000株/hm²）3个不同密度组被选的8个样地每木检尺和解析木分析,结果显示,各年龄段3个密度组之间在树高生长量上没有大的分化,而在胸径、单株材积和蓄积量具有较大的分化。研究表明,密度对山地樟子松的胸径、单株材积和蓄积量有显著影响,而对树高生长量影响不明显;随着密度的增加,林分胸径和单株材积减少,蓄积增加;20龄高密度组和低密度组胸径总生长量相差10 cm、材积总生长量相差0.9 m³。密度愈大,材积迅速生长开始期的树龄愈大。     

三维多相头部脑组织形变特性仿真

基于头部脑组织多相结构解剖图,建立多相非线性脑组织形变仿真计算模型,包括大脑、小脑、脑干、胼胝体以及脑脊液等材料属性各异的6个组成部分.小脑组织本构方程为非线性,其它各个相组织的本构方程均为线性.计算了转动惯性载荷下多相非线性脑组织的变形状况.计算结果表明,脑组织各相交界处应变较大,最大剪应力出现在大脑额叶侧,为257 Pa,脑组织各部分变形差别显著,这会导致脑组织的撕裂和弥漫性轴索损伤(DAI).     

小脑经颅直流电刺激技术提升运动表现的应用

小脑是脑皮层下的一个重要运动调节中枢,它与大脑不同皮层区域在解剖和功能上紧密连接,配合大脑皮层完成机体的运动功能和运动学习。经颅直流电刺激(transcranial direct current stimulation, tDCS)是一种非侵入性的脑刺激技术,通过电极将微弱的电流作用于小脑能有效地提升皮层脊髓兴奋性和调控小脑与大脑皮层间的功能连接。本文系统梳理近20年国内外关于tDCS刺激小脑对提升人类运动表现影响的相关文献,研究结果表明tDCS刺激小脑可以改善人体的运动表现,如姿势控制、运动适应与运动学习、肌肉力量表现等。然而,tDCS刺激小脑的生理机制和刺激强度、刺激时间、刺激时间间隔等参数的选择有待进一步研究。未来的体育科学研究中,如何将tDCS刺激小脑的技术应用于运动训练,帮助运动员突破现有的运动能力仍有待深入探究。     

Energetics and the evolution of human brain size

The human brain stands out among mammals by being unusually large. The expensive-tissue hypothesis explains its evolution by proposing a trade-off between the size of the brain and that of the digestive tract, which is smaller than expected for a primate of our body size. Although this hypothesis is widely accepted, empirical support so far has been equivocal. Here we test it in a sample of 100 mammalian species, including 23 primates, by analysing brain size and organ mass data. We found that, controlling for fat-free body mass, brain size is not negatively correlated with the mass of the digestive tract or any other expensive organ, thus refuting the expensive-tissue hypothesis. Nonetheless, consistent with the existence of energy trade-offs with brain size, we find that the size of brains and adipose depots are negatively correlated in mammals, indicating that encephalization and fat storage are compensatory strategies to buffer against starvation. However, these two strategies can be combined if fat storage does not unduly hamper locomotor efficiency. We propose that human encephalization was made possible by a combination of stabilization of energy inputs and a redirection of energy from locomotion, growth and reproduction.     

不同足球水平女大学生反应抑制能力的差异及其脑结构基础

采用磁共振成像技术,结合Stop-Signal任务范式测评不同足球训练水平女大学生反应抑制能力的差异并探究其脑结构基础．34名被试按照足球训练水平分为对照组（CG）、业余组(AG)和专业组(PG),采用Stop-Signal任务评估反应抑制能力;基于体素形态学对T1结构像进行组间差异分析,并进行FDR校正;采用相关分析探究反应抑制能力和差异脑区之间的关系．结果表明:1）与CG相比,PG和AG的反应时分别缩短48和44 ms（P<0.05）;PG、AG较CG的停止信号反应时分别减少116和96 ms（P<0.05）,PG较AG停止信号反应时显著减少10 ms（P<0.05）;PG(57%)抑制正确率显著高于CG(55%)（P<0.05）．2）与CG相比,PG右侧小脑Crus1、丘脑、中央前后回及小脑蚓部Ⅷ,左侧小脑Crus1、苍白球、丘脑,灰质体积显著增大（P<0.05, FDR）;PG较AG右侧梭状回、中央前回、左侧扣带中回灰质体积显著增大（P<0.001）;AG较CG在双侧苍白球灰质体积显著增大（P<0.001）．3）小脑蚓部Ⅷ灰质密度和反应时存在显著负相关（P<0.05, r= ?0.12）;停止信号反应时与右侧丘脑(P<0.05, r= ?0.41)、左侧苍白球(P<0.01, r= ?0.49)呈显著负相关;抑制正确率与右侧梭状回(P<0.05, r=0.46)、左侧苍白球（P<0.01, r=0.47）呈显著正相关．长期足球训练显著提高女大学生反应抑制能力,且反应抑制能力与小脑蚓部Ⅷ、左侧苍白球、右侧丘脑、右侧梭状回灰质密度显著相关．推测长期足球训练通过诱导基底神经节、小脑灰质体积的变化来调节反应抑制能力的提升．因为本文采用了横断面研究,不能得出反应抑制和足球训练之间的直接因果关系,但在一定程度上表明二者之间存在显著相关关系．因此,后续还需要更多纵向对照研究,进一步确定因果关系．      

MISCIBILITY BEHAVIOR AND PRESSURE DEPENDENCE OF THE SYSTEMS POLYSTYRENE/CYCLOPENTANE AND POLYSTYRENE/1-PHENYLDECANE ACCORDING TO A MODIFIED HOLE THEORY

The influence of pressure on miscibility behavior of the systems polystyrene/cyclopentan(?)and polystyrene/1-phenyldecane is studied with a modified hole theory.It is found that the pres-sure dependence of excess volume is responsible for the different kinds of behavior of these two sys-tems.Furthermore,the excess volume is decomposed into two separatc parts,one from the contri-bution of cell volume expansion and the other from the change of hole fraction,and their relation-ship with pressure dependence of the miscibility behavior is analysed.     

Sex determination compared in Drosophila and Caenorhabditis

Fruitflies and nematodes show many similarities in the general organization of the gene networks that control sexual dimorphism and dosage compensation. In contrast, the underlying molecular mechanisms appear to be very different in these two species. Developmental processes such as sex determination need not be strongly conserved in evolution.     

Mosaic evolution of brain structure in mammals

The mammalian brain comprises a number of functionally distinct systems. It might therefore be expected that natural selection on particular behavioural capacities would have caused size changes selectively, in the systems mediating those capacities. It has been claimed, however, that developmental constraints limited such mosaic evolution, causing co-ordinated size change among individual brain components. Here we analyse comparative data to demonstrate that mosaic change has been an important factor in brain structure evolution. First, the neocortex shows about a fivefold difference in volume between primates and insectivores even after accounting for its scaling relationship with the rest of the brain. Second, brain structures with major anatomical and functional links evolved together independently of evolutionary change in other structures. This is true at the level of both basic brain subdivisions and more fine-grained functional systems. Hence, brain evolution in these groups involved complex relationships among individual brain components.     

Past temperature and delta18O of surface ocean waters inferred from foraminiferal Mg/Ca ratios

Determining the past record of temperature and salinity of ocean surface waters is essential for understanding past changes in climate, such as those which occur across glacial-interglacial transitions. As a useful proxy, the oxygen isotope composition (delta18O) of calcite from planktonic foraminifera has been shown to reflect both surface temperature and seawater delta18O, itself an indicator of global ice volume and salinity. In addition, magnesium/calcium (Mg/Ca) ratios in foraminiferal calcite show a temperature dependence due to the partitioning of Mg during calcification. Here we demonstrate, in a field-based calibration experiment, that the variation of Mg/Ca ratios with temperature is similar for eight species of planktonic foraminifera (when accounting for Mg dissolution effects). Using a multi-species record from the Last Glacial Maximum in the North Atlantic Ocean we found that past temperatures reconstructed from Mg/Ca ratios followed the two other palaeotemperature proxies: faunal abundance and alkenone saturation. Moreover, combining Mg/Ca and delta18O data from the same faunal assemblage, we show that reconstructed surface water delta18O from all foraminiferal species record the same glacial-interglacial change--representing changing hydrography and global ice volume. This reinforces the potential of this combined technique in probing past ocean-climate interactions.     

Parallel evolution of domesticated Caenorhabditis species targets pheromone receptor genes

Evolution can follow predictable genetic trajectories, indicating that discrete environmental shifts can select for reproducible genetic changes. Conspecific individuals are an important feature of an animal's environment, and a potential source of selective pressures. Here we show that adaptation of two Caenorhabditis species to growth at high density, a feature common to domestic environments, occurs by reproducible genetic changes to pheromone receptor genes. Chemical communication through pheromones that accumulate during high-density growth causes young nematode larvae to enter the long-lived but non-reproductive dauer stage. Two strains of Caenorhabditis elegans grown at high density have independently acquired multigenic resistance to pheromone-induced dauer formation. In each strain, resistance to the pheromone ascaroside C3 results from a deletion that disrupts the adjacent chemoreceptor genes serpentine receptor class g (srg)-36 and -37. Through misexpression experiments, we show that these genes encode redundant G-protein-coupled receptors for ascaroside C3. Multigenic resistance to dauer formation has also arisen in high-density cultures of a different nematode species, Caenorhabditis briggsae, resulting in part from deletion of an srg gene paralogous to srg-36 and srg-37. These results demonstrate rapid remodelling of the chemoreceptor repertoire as an adaptation to specific environments, and indicate that parallel changes to a common genetic substrate can affect life-history traits across species.     

NOS在甲状腺功能低下小鼠脑中含量变化的研究

本文研究了甲状腺激素减少时,小鼠的大脑、小脑、海马、嗅脑等脑组织中一氧化氮合酶（NOS）含量的变化.采用丙硫氧嘧啶（PTU）持续灌注20日龄左右雌性昆明小鼠造成甲减模型.采用NOS的生化测定法检测甲减小鼠的大脑、小脑、嗅脑、海马等中的NOS含量;检测指标包括组织中总一氧化氮合酶（TNOS）活性,以及诱导型一氧化氮合酶（iNOS）及结构型一氧化氮合酶（cNOS）两种分型酶的活性.生化测定法显示,甲状腺功能低下小鼠NOS含量与对照组比较在大脑、小脑和嗅脑中均出现了下降,cNOS在大脑、小脑、海马、嗅脑部位也均出现了下调.而iNOS含量在甲状腺功能低下小鼠的大脑、小脑、海马、嗅脑中却出现了上调.由此可得出,甲状腺激素的分泌异常会造成NOS含量的异常,NO信号系统可能参与甲状腺激素缺乏所致的脑损害过程.