[Evolution of human brain and intelligence].

Science.gov (United States)

Lakatos, László; Janka, Zoltán

2008-07-30

The biological evolution, including human evolution is mainly driven by environmental changes. Accidental genetic modifications and their innovative results make the successful adaptation possible. As we know the human evolution started 7-8 million years ago in the African savannah, where upright position and bipedalism were significantly advantageous. The main drive of improving manual actions and tool making could be to obtain more food. Our ancestor got more meat due to more successful hunting, resulting in more caloric intake, more protein and essential fatty acid in the meal. The nervous system uses disproportionally high level of energy, so better quality of food was a basic condition for the evolution of huge human brain. The size of human brain was tripled during 3.5 million years, it increased from the average of 450 cm3 of Australopithecinae to the average of 1350 cm3 of Homo sapiens. A genetic change in the system controlling gene expression could happen about 200 000 years ago, which influenced the development of nervous system, the sensorimotor function and learning ability for motor processes. The appearance and stabilisation of FOXP2 gene structure as feature of modern man coincided with the first presence and quick spread of Homo sapiens on the whole Earth. This genetic modification made opportunity for human language, as the basis of abrupt evolution of human intelligence. The brain region being responsible for human language is the left planum temporale, which is much larger in left hemisphere. This shows the most typical human brain asymmetry. In this case the anatomical asymmetry means a clearly defined functional asymmetry as well, where the brain hemispheres act differently. The preference in using hands, the lateralised using of tools resulted in the brain asymmetry, which is the precondition of human language and intelligence. However, it cannot be held anymore, that only humans make tools, because our closest relatives, the chimpanzees are

The evolution of the brain, the human nature of cortical circuits and intellectual creativity

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Javier eDeFelipe

2011-05-01

Full Text Available The tremendous expansion and the differentiation of the neocortex constitute two major events in the evolution of the mammalian brain. The increase in size and complexity of our brains opened the way to a spectacular development of cognitive and mental skills. This expansion during evolution facilitated the addition of archetypical microcircuits, which increased the complexity of the human brain and contributed to its uniqueness. However, fundamental differences even exist between distinct mammalian species. Here, we shall discuss the issue of our humanity from a neurobiological and historical perspective.

Reconsidering the evolution of brain, cognition and behaviour in birds and mammals

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Romain eWillemet

2013-07-01

Full Text Available Despite decades of research, some of the most basic issues concerning the extraordinarily complex brains and behaviour of birds and mammals, such as the factors responsible for the diversity of brain size and composition, are still unclear. This is partly due to a number of conceptual and methodological issues. Determining species and group differences in brain composition requires accounting for the presence of taxon-cerebrotypes and the use of precise statistical methods. The role of allometry in determining brain variables should be revised. In particular, bird and mammalian brains appear to have evolved in response to a variety of selective pressures influencing both brain size and composition. Brain and cognition are indeed meta-variables, made up of the variables that are ecologically relevant and evolutionarily selected. External indicators of species differences in cognition and behaviour are limited by the complexity of these differences. Indeed, behavioural differences between species and individuals are caused by cognitive and affective components. Although intra-species variability forms the basis of species evolution, some of the mechanisms underlying individual differences in brain and behaviour appear to differ from those between species. While many issues have persisted over the years because of a lack of appropriate data or methods to test them; several fallacies, particularly those related to the human brain, reflect scientists’ preconceptions. The theoretical framework on the evolution of brain, cognition and behaviour in birds and mammals should be reconsidered with these biases in mind.

Brain Evolution and Human Neuropsychology: The Inferential Brain Hypothesis

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Koscik, Timothy R.; Tranel, Daniel

2013-01-01

Collaboration between human neuropsychology and comparative neuroscience has generated invaluable contributions to our understanding of human brain evolution and function. Further cross-talk between these disciplines has the potential to continue to revolutionize these fields. Modern neuroimaging methods could be applied in a comparative context, yielding exciting new data with the potential of providing insight into brain evolution. Conversely, incorporating an evolutionary base into the theoretical perspectives from which we approach human neuropsychology could lead to novel hypotheses and testable predictions. In the spirit of these objectives, we present here a new theoretical proposal, the Inferential Brain Hypothesis, whereby the human brain is thought to be characterized by a shift from perceptual processing to inferential computation, particularly within the social realm. This shift is believed to be a driving force for the evolution of the large human cortex. PMID:22459075

Evolution of brain and culture: the neurological and cognitive journey from Australopithecus to Albert Einstein.

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Falk, Dean

2016-06-20

Fossil and comparative primatological evidence suggest that alterations in the development of prehistoric hominin infants kindled three consecutive evolutionary-developmental (evo-devo) trends that, ultimately, paved the way for the evolution of the human brain and cognition. In the earliest trend, infants' development of posture and locomotion became delayed because of anatomical changes that accompanied the prolonged evolution of bipedalism. Because modern humans have inherited these changes, our babies are much slower than other primates to reach developmental milestones such as standing, crawling, and walking. The delay in ancestral babies' physical development eventually precipitated an evolutionary reversal in which they became increasing unable to cling independently to their mothers. For the first time in prehistory, babies were, thus, periodically deprived of direct physical contact with their mothers. This prompted the emergence of a second evo-devo trend in which infants sought contact comfort from caregivers using evolved signals, including new ways of crying that are conserved in modern babies. Such signaling stimulated intense reciprocal interactions between prehistoric mothers and infants that seeded the eventual emergence of motherese and, subsequently, protolanguage. The third trend was for an extreme acceleration in brain growth that began prior to the last trimester of gestation and continued through infants' first postnatal year (early "brain spurt"). Conservation of this trend in modern babies explains why human brains reach adult sizes that are over three times those of chimpanzees. The fossil record of hominin cranial capacities together with comparative neuroanatomical data suggest that, around 3 million years ago, early brain spurts began to facilitate an evolutionary trajectory for increasingly large adult brains in association with neurological reorganization. The prehistoric increase in brain size eventually caused parturition to become

Reconstructing the ups and downs of primate brain evolution: implications for adaptive hypotheses and Homo floresiensis

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Barton Robert A

2010-01-01

Full Text Available Abstract Background Brain size is a key adaptive trait. It is often assumed that increasing brain size was a general evolutionary trend in primates, yet recent fossil discoveries have documented brain size decreases in some lineages, raising the question of how general a trend there was for brains to increase in mass over evolutionary time. We present the first systematic phylogenetic analysis designed to answer this question. Results We performed ancestral state reconstructions of three traits (absolute brain mass, absolute body mass, relative brain mass using 37 extant and 23 extinct primate species and three approaches to ancestral state reconstruction: parsimony, maximum likelihood and Bayesian Markov-chain Monte Carlo. Both absolute and relative brain mass generally increased over evolutionary time, but body mass did not. Nevertheless both absolute and relative brain mass decreased along several branches. Applying these results to the contentious case of Homo floresiensis, we find a number of scenarios under which the proposed evolution of Homo floresiensis' small brain appears to be consistent with patterns observed along other lineages, dependent on body mass and phylogenetic position. Conclusions Our results confirm that brain expansion began early in primate evolution and show that increases occurred in all major clades. Only in terms of an increase in absolute mass does the human lineage appear particularly striking, with both the rate of proportional change in mass and relative brain size having episodes of greater expansion elsewhere on the primate phylogeny. However, decreases in brain mass also occurred along branches in all major clades, and we conclude that, while selection has acted to enlarge primate brains, in some lineages this trend has been reversed. Further analyses of the phylogenetic position of Homo floresiensis and better body mass estimates are required to confirm the plausibility of the evolution of its small brain

Estrogen regulation of microcephaly genes and evolution of brain sexual dimorphism in primates.

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Shi, Lei; Lin, Qiang; Su, Bing

2015-06-30

Sexual dimorphism in brain size is common among primates, including humans, apes and some Old World monkeys. In these species, the brain size of males is generally larger than that of females. Curiously, this dimorphism has persisted over the course of primate evolution and human origin, but there is no explanation for the underlying genetic controls that have maintained this disparity in brain size. In the present study, we tested the effect of the female hormone (estradiol) on seven genes known to be related to brain size in both humans and nonhuman primates, and we identified half estrogen responsive elements (half EREs) in the promoter regions of four genes (MCPH1, ASPM, CDK5RAP2 and WDR62). Likewise, at sequence level, it appears that these half EREs are generally conserved across primates. Later testing via a reporter gene assay and cell-based endogenous expression measurement revealed that estradiol could significantly suppress the expression of the four affected genes involved in brain size. More intriguingly, when the half EREs were deleted from the promoters, the suppression effect disappeared, suggesting that the half EREs mediate the regulation of estradiol on the brain size genes. We next replicated these experiments using promoter sequences from chimpanzees and rhesus macaques, and observed a similar suppressive effect of estradiol on gene expression, suggesting that this mechanism is conserved among primate species that exhibit brain size dimorphism. Brain size dimorphism among certain primates, including humans, is likely regulated by estrogen through its sex-dependent suppression of brain size genes during development.

Human brain expansion during evolution is independent of fire control and cooking

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Alianda Maira Cornélio

2016-04-01

Full Text Available What makes humans unique? This question has fascinated scientists and philosophers for centuries and it is still a matter of intense debate. Nowadays, human brain expansion during evolution has been acknowledged to explain our empowered cognitive capabilities. The drivers for such accelerated expansion remain, however, largely unknown. In this sense, studies have suggested that the cooking of food could be a pre-requisite for the expansion of brain size in early hominins. However, this appealing hypothesis is only supported by a mathematical model suggesting that the increasing number of neurons in the brain would constrain body size among primates due to a limited amount of calories obtained from diets. Here, we show, by using a similar mathematical model, that a tradeoff between body mass and the number of brain neurons imposed by dietary constraints during hominin evolution is unlikely. Instead, the predictable number of neurons in the hominin brain varies much more in function of foraging efficiency than body mass. We also review archeological data to show that the expansion of the brain volume in the hominin lineage is described by a linear function independent of evidences of fire control, and therefore, thermal processing of food does not account for this phenomenon. Finally, we report experiments in mice showing that thermal processing of meat does not increase its caloric availability in mice. Altogether, our data indicate that cooking is neither sufficient nor necessary to explain hominin brain expansion.

Human Brain Expansion during Evolution Is Independent of Fire Control and Cooking.

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Cornélio, Alianda M; de Bittencourt-Navarrete, Ruben E; de Bittencourt Brum, Ricardo; Queiroz, Claudio M; Costa, Marcos R

2016-01-01

What makes humans unique? This question has fascinated scientists and philosophers for centuries and it is still a matter of intense debate. Nowadays, human brain expansion during evolution has been acknowledged to explain our empowered cognitive capabilities. The drivers for such accelerated expansion remain, however, largely unknown. In this sense, studies have suggested that the cooking of food could be a pre-requisite for the expansion of brain size in early hominins. However, this appealing hypothesis is only supported by a mathematical model suggesting that the increasing number of neurons in the brain would constrain body size among primates due to a limited amount of calories obtained from diets. Here, we show, by using a similar mathematical model, that a tradeoff between body mass and the number of brain neurons imposed by dietary constraints during hominin evolution is unlikely. Instead, the predictable number of neurons in the hominin brain varies much more in function of foraging efficiency than body mass. We also review archeological data to show that the expansion of the brain volume in the hominin lineage is described by a linear function independent of evidence of fire control, and therefore, thermal processing of food does not account for this phenomenon. Finally, we report experiments in mice showing that thermal processing of meat does not increase its caloric availability in mice. Altogether, our data indicate that cooking is neither sufficient nor necessary to explain hominin brain expansion.

Brain size and encephalization in early to Mid-Pleistocene Homo.

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Rightmire, G Philip

2004-06-01

Important changes in the brain have occurred during the course of human evolution. Both absolute and relative size increases can be documented for species of Homo, culminating in the appearance of modern humans. One species that is particularly well-represented by fossil crania is Homo erectus. The mean capacity for 30 individuals is 973 cm(3). Within this group there is substantial variation, but brain size increases slightly in specimens from later time periods. Other Middle Pleistocene crania differ from those of Homo erectus. Characters of the facial skeleton, vault, and cranial base suggest that fossils from sites such as Arago Cave in France, the Sima de los Huesos in Spain, Bodo in Ethiopia, Broken Hill in Zambia, and perhaps Dali in China belong to the taxon Homo heidelbergensis. Ten of these mid-Quaternary hominins have brains averaging 1,206 cm(3) in volume, and many fall beyond the limits of size predicted for Homo erectus of equivalent age. When orbit height is used to construct an index of relative brain size, it is apparent that the (significant) increase in volume documented for the Middle Pleistocene individuals is not simply a consequence of larger body mass. Encephalization quotient values confirm this finding. These changes in absolute and relative brain size can be taken as further corroborative evidence for a speciation event, in which Homo erectus produced a daughter lineage. It is probable that Homo heidelbergensis originated in Africa or western Eurasia and then ranged widely across the Old World. Archaeological traces indicate that these populations differed in their technology and behavior from earlier hominins. Copyright 2003 Wiley-Liss, Inc.

A fossil brain from the Cretaceous of European Russia and avian sensory evolution.

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Kurochkin, Evgeny N; Dyke, Gareth J; Saveliev, Sergei V; Pervushov, Evgeny M; Popov, Evgeny V

2007-06-22

Fossils preserving traces of soft anatomy are rare in the fossil record; even rarer is evidence bearing on the size and shape of sense organs that provide us with insights into mode of life. Here, we describe unique fossil preservation of an avian brain from the Volgograd region of European Russia. The brain of this Melovatka bird is similar in shape and morphology to those of known fossil ornithurines (the lineage that includes living birds), such as the marine diving birds Hesperornis and Enaliornis, but documents a new stage in avian sensory evolution: acute nocturnal vision coupled with well-developed hearing and smell, developed by the Late Cretaceous (ca 90Myr ago). This fossil also provides insights into previous 'bird-like' brain reconstructions for the most basal avian Archaeopteryx--reduction of olfactory lobes (sense of smell) and enlargement of the hindbrain (cerebellum) occurred subsequent to Archaeopteryx in avian evolution, closer to the ornithurine lineage that comprises living birds. The Melovatka bird also suggests that brain enlargement in early avians was not correlated with the evolution of powered flight.

Human Brain Expansion during Evolution Is Independent of Fire Control and Cooking

OpenAIRE

Corn?lio, Alianda M.; de Bittencourt-Navarrete, Ruben E.; de Bittencourt Brum, Ricardo; Queiroz, Claudio M.; Costa, Marcos R.

2016-01-01

What makes humans unique? This question has fascinated scientists and philosophers for centuries and it is still a matter of intense debate. Nowadays, human brain expansion during evolution has been acknowledged to explain our empowered cognitive capabilities. The drivers for such accelerated expansion remain, however, largely unknown. In this sense, studies have suggested that the cooking of food could be a pre-requisite for the expansion of brain size in early hominins. However, this appeal...

Size Evolution and Stochastic Models: Explaining Ostracod Size through Probabilistic Distributions

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Krawczyk, M.; Decker, S.; Heim, N. A.; Payne, J.

2014-12-01

The biovolume of animals has functioned as an important benchmark for measuring evolution throughout geologic time. In our project, we examined the observed average body size of ostracods over time in order to understand the mechanism of size evolution in these marine organisms. The body size of ostracods has varied since the beginning of the Ordovician, where the first true ostracods appeared. We created a stochastic branching model to create possible evolutionary trees of ostracod size. Using stratigraphic ranges for ostracods compiled from over 750 genera in the Treatise on Invertebrate Paleontology, we calculated overall speciation and extinction rates for our model. At each timestep in our model, new lineages can evolve or existing lineages can become extinct. Newly evolved lineages are assigned sizes based on their parent genera. We parameterized our model to generate neutral and directional changes in ostracod size to compare with the observed data. New sizes were chosen via a normal distribution, and the neutral model selected new sizes differentials centered on zero, allowing for an equal chance of larger or smaller ostracods at each speciation. Conversely, the directional model centered the distribution on a negative value, giving a larger chance of smaller ostracods. Our data strongly suggests that the overall direction of ostracod evolution has been following a model that directionally pushes mean ostracod size down, shying away from a neutral model. Our model was able to match the magnitude of size decrease. Our models had a constant linear decrease while the actual data had a much more rapid initial rate followed by a constant size. The nuance of the observed trends ultimately suggests a more complex method of size evolution. In conclusion, probabilistic methods can provide valuable insight into possible evolutionary mechanisms determining size evolution in ostracods.

The correlated evolution of antipredator defences and brain size in mammals.

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Stankowich, Theodore; Romero, Ashly N

2017-01-11

Mammals that possess elaborate antipredator defences such as body armour, spines and quills are usually well protected, intermediate in size, primarily insectivorous and live in simple open environments. The benefits of such defences seem clear and may relax selection on maintaining cognitive abilities that aid in vigilance and predator recognition, and their bearers may accrue extensive production and maintenance costs. Here, in this comparative phylogenetic analysis of measurements of encephalization quotient and morphological defence scores of 647 mammal species representing nearly every order, we found that as lineages evolve stronger defences, they suffer a correlated reduction in encephalization. The only exceptions were those that live in trees-a complex three-dimensional world probably requiring greater cognitive abilities. At the proximate level, because brain tissue is extremely energetically expensive to build, mammals may be trading off spending more on elaborate defences and saving by building less powerful brains. At the ultimate level, having greater defences may also reduce the need for advanced cognitive abilities for constant assessment of environmental predation risk, especially in simple open environments. © 2017 The Author(s).

The correlated evolution of antipredator defences and brain size in mammals

Science.gov (United States)

Romero, Ashly N.

2017-01-01

Mammals that possess elaborate antipredator defences such as body armour, spines and quills are usually well protected, intermediate in size, primarily insectivorous and live in simple open environments. The benefits of such defences seem clear and may relax selection on maintaining cognitive abilities that aid in vigilance and predator recognition, and their bearers may accrue extensive production and maintenance costs. Here, in this comparative phylogenetic analysis of measurements of encephalization quotient and morphological defence scores of 647 mammal species representing nearly every order, we found that as lineages evolve stronger defences, they suffer a correlated reduction in encephalization. The only exceptions were those that live in trees—a complex three-dimensional world probably requiring greater cognitive abilities. At the proximate level, because brain tissue is extremely energetically expensive to build, mammals may be trading off spending more on elaborate defences and saving by building less powerful brains. At the ultimate level, having greater defences may also reduce the need for advanced cognitive abilities for constant assessment of environmental predation risk, especially in simple open environments. PMID:28077771

Genome Size Dynamics and Evolution in Monocots

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Ilia J. Leitch

2010-01-01

Full Text Available Monocot genomic diversity includes striking variation at many levels. This paper compares various genomic characters (e.g., range of chromosome numbers and ploidy levels, occurrence of endopolyploidy, GC content, chromosome packaging and organization, genome size between monocots and the remaining angiosperms to discern just how distinctive monocot genomes are. One of the most notable features of monocots is their wide range and diversity of genome sizes, including the species with the largest genome so far reported in plants. This genomic character is analysed in greater detail, within a phylogenetic context. By surveying available genome size and chromosome data it is apparent that different monocot orders follow distinctive modes of genome size and chromosome evolution. Further insights into genome size-evolution and dynamics were obtained using statistical modelling approaches to reconstruct the ancestral genome size at key nodes across the monocot phylogenetic tree. Such approaches reveal that while the ancestral genome size of all monocots was small (1C=1.9 pg, there have been several major increases and decreases during monocot evolution. In addition, notable increases in the rates of genome size-evolution were found in Asparagales and Poales compared with other monocot lineages.

Extreme sexual brain size dimorphism in sticklebacks: a consequence of the cognitive challenges of sex and parenting?

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Alexander Kotrschal

Full Text Available Selection pressures that act differently on males and females produce numerous differences between the sexes in morphology and behaviour. However, apart from the controversial report that males have slightly heavier brains than females in humans, evidence for substantial sexual dimorphism in brain size is scarce. This apparent sexual uniformity is surprising given that sexually distinct selection pressures are ubiquitous and that brains are one of the most plastic vertebrate organs. Here we demonstrate the highest level of sexual brain size dimorphism ever reported in any vertebrate: male three-spined stickleback of two morphs in an Icelandic lake have 23% heavier brains than females. We suggest that this dramatic sexual size dimorphism is generated by the many cognitively demanding challenges that males are faced in this species, such as an elaborate courtship display, the construction of an ornate nest and a male-only parental care system. However, we consider also alternative explanations for smaller brains in females, such as life-history trade-offs. Our demonstration of unprecedented levels of sexual dimorphism in brain size in the three-spined stickleback implies that behavioural and life-history differences among the sexes can have strong effects also on neural development and proposes new fields of research for understanding brain evolution.

On the Evolution of the Mammalian Brain.

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Torday, John S; Miller, William B

2016-01-01

Hobson and Friston have hypothesized that the brain must actively dissipate heat in order to process information (Hobson et al., 2014). This physiologic trait is functionally homologous with the first instantation of life formed by lipids suspended in water forming micelles- allowing the reduction in entropy (heat dissipation). This circumvents the Second Law of Thermodynamics permitting the transfer of information between living entities, enabling them to perpetually glean information from the environment, that is felt by many to correspond to evolution per se. The next evolutionary milestone was the advent of cholesterol, embedded in the cell membranes of primordial eukaryotes, facilitating metabolism, oxygenation and locomotion, the triadic basis for vertebrate evolution. Lipids were key to homeostatic regulation of calcium, forming calcium channels. Cell membrane cholesterol also fostered metazoan evolution by forming lipid rafts for receptor-mediated cell-cell signaling, the origin of the endocrine system. The eukaryotic cell membrane exapted to all complex physiologic traits, including the lung and brain, which are molecularly homologous through the function of neuregulin, mediating both lung development and myelinization of neurons. That cooption later exapted as endothermy during the water-land transition (Torday, 2015a), perhaps being the functional homolog for brain heat dissipation and conscious/mindful information processing. The skin and brain similarly share molecular homologies through the "skin-brain" hypothesis, giving insight to the cellular-molecular "arc" of consciousness from its unicellular origins to integrated physiology. This perspective on the evolution of the central nervous system clarifies self-organization, reconciling thermodynamic and informational definitions of the underlying biophysical mechanisms, thereby elucidating relations between the predictive capabilities of the brain and self-organizational processes.

Joint evolution of predator body size and prey-size preference.

NARCIS (Netherlands)

Troost, T.A.; Kooi, B.W.; Dieckmann, U.

2007-01-01

We studied the joint evolution of predator body size and prey-size preference based on dynamic energy budget theory. The predators' demography and their functional response are based on general eco-physiological principles involving the size of both predator and prey. While our model can account for

Joint evolution of predator body size and prey-size preference

NARCIS (Netherlands)

Troost, Tineke; Kooi, Bob; Dieckmann, Ulf

2007-01-01

We studied the joint evolution of predator body size and prey-size preference based on dynamic energy budget theory. The predators’ demography and their functional response are based on general eco-physiological principles involving the size of both predator and prey. While our model can account

On the evolution of the mammalian brain

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John Steven Torday

2016-04-01

Full Text Available Hobson and Friston have hypothesized that the brain must actively dissipate heat in order to process information (Virtual reality and consciousness inference in dreaming. Front Psychol. 2014 Oct 9;5:1133.. This physiologic trait is functionally homologous with the first instantation of life formed by lipids suspended in water forming micelles- allowing the reduction in entropy (heat dissipation, circumventing the Second Law of Thermodynamics permitting the transfer of information between living entities, enabling them to perpetually glean information from the environment (= evolution. The next evolutionary milestone was the advent of cholesterol, embedded in the cell membranes of primordial eukaryotes, facilitating metabolism, oxygenation and locomotion, the triadic basis for vertebrate evolution. Lipids were key to homeostatic regulation of calcium, forming calcium channels. Cell membrane cholesterol also fostered metazoan evolution by forming lipid rafts for receptor-mediated cell-cell signaling, the origin of the endocrine system. The eukaryotic cell membrane exapted to all complex physiologic traits, including the lung and brain, which are molecularly homologous through the function of neuregulin, mediating both lung development and myelinization of neurons. That cooption later exapted as endothermy during the water-land transition (Torday JS. A Central Theory of Biology. Med Hypotheses. 2015 Jul;85(1:49-57, perhaps being the functional homolog for brain heat dissipation and consciousness/mind. The skin and brain similarly share molecular homologies through the ‘skin-brain’ hypothesis, giving insight to the cellular-molecular ‘arc’ of consciousness from its unicellular origins to integrated physiology. This perspective on the evolution of the central nervous system clarifies self-organization, reconciling thermodynamic and informational definitions of the underlying biophysical mechanisms, thereby elucidating relations between the

Brain size and urbanization in birds

Institute of Scientific and Technical Information of China (English)

Anders; Pape; M?ller; Johannes; Erritz?e

2015-01-01

Background: Brain size may affect the probability of invasion of urban habitats if a relatively larger brain entails superior ability to adapt to novel environments. However, once urbanized urban environments may provide poor quality food that has negative consequences for normal brain development resulting in an excess of individuals with small brains.Methods: Here we analyze the independent effects of mean, standard deviation and skewness in brain mass for invasion of urban habitats by 108 species of birds using phylogenetic multiple regression analyses weighted by sample size.Results: There was no significant difference in mean brain mass between urbanized and non-urbanized species or between urban and rural populations of the same species, and mean brain mass was not significantly correlated with time since urbanization. Bird species that became urbanized had a greater standard deviation in brain mass than non-urbanized species, and the standard deviation in brain mass increased with time since urbanization. Brain mass was significantly left skewed in species that remained rural, while there was no significant skew in urbanized species. The degree of left skew was greater in urban than in rural populations of the same species, and successfully urbanized species decreased the degree of left skew with time since urbanization. This is consistent with the hypothesis that sub-optimal brain development was more common in rural habitats resulting in disproportionately many individuals with very smal brains.Conclusions: These findings do not support the hypothesis that large brains promote urbanization, but suggest that skewness has played a role in the initial invasion of urban habitats, and that variance and skew in brain mass have increased as species have become urbanized.

Brain size and urbanization in birds

Institute of Scientific and Technical Information of China (English)

Anders Pape Mller; Johannes Erritze

2015-01-01

Background:Brain size may affect the probability of invasion of urban habitats if a relatively larger brain entails superior ability to adapt to novel environments. However, once urbanized urban environments may provide poor quality food that has negative consequences for normal brain development resulting in an excess of individuals with small brains. Methods:Here we analyze the independent effects of mean, standard deviation and skewness in brain mass for invasion of urban habitats by 108 species of birds using phylogenetic multiple regression analyses weighted by sample size. Results:There was no significant difference in mean brain mass between urbanized and non-urbanized species or between urban and rural populations of the same species, and mean brain mass was not significantly correlated with time since urbanization. Bird species that became urbanized had a greater standard deviation in brain mass than non-urbanized species, and the standard deviation in brain mass increased with time since urbanization. Brain mass was significantly left skewed in species that remained rural, while there was no significant skew in urbanized species. The degree of left skew was greater in urban than in rural populations of the same species, and successfully urbanized species decreased the degree of left skew with time since urbanization. This is consistent with the hypothesis that sub-optimal brain development was more common in rural habitats resulting in disproportionately many individuals with very smal brains. Conclusions:These findings do not support the hypothesis that large brains promote urbanization, but suggest that skewness has played a role in the initial invasion of urban habitats, and that variance and skew in brain mass have increased as species have become urbanized.

Rate of evolution in brain-expressed genes in humans and other primates.

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Hurng-Yi Wang

2007-02-01

Full Text Available Brain-expressed genes are known to evolve slowly in mammals. Nevertheless, since brains of higher primates have evolved rapidly, one might expect acceleration in DNA sequence evolution in their brain-expressed genes. In this study, we carried out full-length cDNA sequencing on the brain transcriptome of an Old World monkey (OWM and then conducted three-way comparisons among (i mouse, OWM, and human, and (ii OWM, chimpanzee, and human. Although brain-expressed genes indeed appear to evolve more rapidly in species with more advanced brains (apes > OWM > mouse, a similar lineage effect is observable for most other genes. The broad inclusion of genes in the reference set to represent the genomic average is therefore critical to this type of analysis. Calibrated against the genomic average, the rate of evolution among brain-expressed genes is probably lower (or at most equal in humans than in chimpanzee and OWM. Interestingly, the trend of slow evolution in coding sequence is no less pronounced among brain-specific genes, vis-à-vis brain-expressed genes in general. The human brain may thus differ from those of our close relatives in two opposite directions: (i faster evolution in gene expression, and (ii a likely slowdown in the evolution of protein sequences. Possible explanations and hypotheses are discussed.

The significance of the subplate for evolution and developmental plasticity of the human brain.

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Judaš, Miloš; Sedmak, Goran; Kostović, Ivica

2013-01-01

The human life-history is characterized by long development and introduction of new developmental stages, such as childhood and adolescence. The developing brain had important role in these life-history changes because it is expensive tissue which uses up to 80% of resting metabolic rate (RMR) in the newborn and continues to use almost 50% of it during the first 5 postnatal years. Our hominid ancestors managed to lift-up metabolic constraints to increase in brain size by several interrelated ecological, behavioral and social adaptations, such as dietary change, invention of cooking, creation of family-bonded reproductive units, and life-history changes. This opened new vistas for the developing brain, because it became possible to metabolically support transient patterns of brain organization as well as developmental brain plasticity for much longer period and with much greater number of neurons and connectivity combinations in comparison to apes. This included the shaping of cortical connections through the interaction with infant's social environment, which probably enhanced typically human evolution of language, cognition and self-awareness. In this review, we propose that the transient subplate zone and its postnatal remnant (interstitial neurons of the gyral white matter) probably served as the main playground for evolution of these developmental shifts, and describe various features that makes human subplate uniquely positioned to have such a role in comparison with other primates.

THE SIGNIFICANCE OF THE SUBPLATE FOR EVOLUTION AND DEVELOPMENTAL PLASTICITY OF THE HUMAN BRAIN

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MILOS eJUDAS

2013-08-01

Full Text Available The human life-history is characterized by long development and introduction of new developmental stages, such as childhood and adolescence. The developing brain had important role in these life-history changes because it is expensive tissue which uses up to 80% of resting metabolic rate in the newborn and continues to use almost 50% of it during the first 5 postnatal years. Our hominid ancestors managed to lift-up metabolic constraints to increase in brain size by several interrelated ecological, behavioral and social adaptations, such as dietary change, invention of cooking, creation of family-bonded reproductive units, and life-history changes. This opened new vistas for the developing brain, because it became possible to metabolically support transient patterns of brain organization as well as developmental brain plasticity for much longer period and with much greater number of neurons and connectivity combinations in comparison to apes. This included the shaping of cortical connections through the interaction with infant's social environment, which probably enhanced typically human evolution of language, cognition and self-awareness. In this review, we propose that the transient subplate zone and its postnatal remnant (interstitial neurons of the gyral white matter probably served as the main playground for evolution of these developmental shifts, and describe various features that makes human subplate uniquely positioned to have such a role in comparison with other primates.

Ecological correlates of relative brain size in some South African ...

African Journals Online (AJOL)

Relative brain size (size of the brain once body size effects have been removed) has been calculated for 16 species of rodent from South Africa and is shown to vary with six species having a positive RBS (that is a brain larger than expected) and 10 a negative RBS. Arboreal species such as Paraxerus cepapi and ...

Optimizing full-brain coverage in human brain MRI through population distributions of brain size

NARCIS (Netherlands)

Mennes, M.; Jenkinson, M.; Valabregue, R.; Buitelaar, J.K.; Beckmann, C.F.; Smith, S.

2014-01-01

When defining an MRI protocol, brain researchers need to set multiple interdependent parameters that define repetition time (TR), voxel size, field-of-view (FOV), etc. Typically, researchers aim to image the full brain, making the expected FOV an important parameter to consider. Especially in 2D-EPI

Toward the Language-Ready Brain: Biological Evolution and Primate Comparisons.

Science.gov (United States)

Arbib, Michael A

2017-02-01

The approach to language evolution suggested here focuses on three questions: How did the human brain evolve so that humans can develop, use, and acquire languages? How can the evolutionary quest be informed by studying brain, behavior, and social interaction in monkeys, apes, and humans? How can computational modeling advance these studies? I hypothesize that the brain is language ready in that the earliest humans had protolanguages but not languages (i.e., communication systems endowed with rich and open-ended lexicons and grammars supporting a compositional semantics), and that it took cultural evolution to yield societies (a cultural constructed niche) in which language-ready brains could become language-using brains. The mirror system hypothesis is a well-developed example of this approach, but I offer it here not as a closed theory but as an evolving framework for the development and analysis of conflicting subhypotheses in the hope of their eventual integration. I also stress that computational modeling helps us understand the evolving role of mirror neurons, not in and of themselves, but only in their interaction with systems "beyond the mirror." Because a theory of evolution needs a clear characterization of what it is that evolved, I also outline ideas for research in neurolinguistics to complement studies of the evolution of the language-ready brain. A clear challenge is to go beyond models of speech comprehension to include sign language and models of production, and to link language to visuomotor interaction with the physical and social world.

Brain Size, IQ, and Racial-Group Differences: Evidence from Musculoskeletal Traits.

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Rushton, J. Philippe; Rushton, Elizabeth W.

2003-01-01

Correlated brain size differences with 37 musculoskeletal variables shown in evolutionary textbooks to change with brain size. Findings from a sample of more than 6,000 U.S. military personnel indicate that racial differences in brain size are securely established and are the most likely biological mediators of race differences in intelligence.…

Evolution of the human brain: design without a designer.

NARCIS (Netherlands)

Hofman, M.A.; Kaas, John

2017-01-01

The evolutionary expansion of the brain is among the most distinctive morphological features of mammals. During the past decades, considerable progress has been made in explaining brain evolution in terms of physical and adaptive principles. The objective of this chapter is to present current

The evolution of modern human brain shape

Science.gov (United States)

Neubauer, Simon; Hublin, Jean-Jacques; Gunz, Philipp

2018-01-01

Modern humans have large and globular brains that distinguish them from their extinct Homo relatives. The characteristic globularity develops during a prenatal and early postnatal period of rapid brain growth critical for neural wiring and cognitive development. However, it remains unknown when and how brain globularity evolved and how it relates to evolutionary brain size increase. On the basis of computed tomographic scans and geometric morphometric analyses, we analyzed endocranial casts of Homo sapiens fossils (N = 20) from different time periods. Our data show that, 300,000 years ago, brain size in early H. sapiens already fell within the range of present-day humans. Brain shape, however, evolved gradually within the H. sapiens lineage, reaching present-day human variation between about 100,000 and 35,000 years ago. This process started only after other key features of craniofacial morphology appeared modern and paralleled the emergence of behavioral modernity as seen from the archeological record. Our findings are consistent with important genetic changes affecting early brain development within the H. sapiens lineage since the origin of the species and before the transition to the Later Stone Age and the Upper Paleolithic that mark full behavioral modernity. PMID:29376123

The evolution of modern human brain shape.

Science.gov (United States)

Neubauer, Simon; Hublin, Jean-Jacques; Gunz, Philipp

2018-01-01

Modern humans have large and globular brains that distinguish them from their extinct Homo relatives. The characteristic globularity develops during a prenatal and early postnatal period of rapid brain growth critical for neural wiring and cognitive development. However, it remains unknown when and how brain globularity evolved and how it relates to evolutionary brain size increase. On the basis of computed tomographic scans and geometric morphometric analyses, we analyzed endocranial casts of Homo sapiens fossils ( N = 20) from different time periods. Our data show that, 300,000 years ago, brain size in early H. sapiens already fell within the range of present-day humans. Brain shape, however, evolved gradually within the H. sapiens lineage, reaching present-day human variation between about 100,000 and 35,000 years ago. This process started only after other key features of craniofacial morphology appeared modern and paralleled the emergence of behavioral modernity as seen from the archeological record. Our findings are consistent with important genetic changes affecting early brain development within the H. sapiens lineage since the origin of the species and before the transition to the Later Stone Age and the Upper Paleolithic that mark full behavioral modernity.

Evolution of extreme body size disparity in monitor lizards (Varanus).

Science.gov (United States)

Collar, David C; Schulte, James A; Losos, Jonathan B

2011-09-01

Many features of species' biology, including life history, physiology, morphology, and ecology are tightly linked to body size. Investigation into the causes of size divergence is therefore critical to understanding the factors shaping phenotypic diversity within clades. In this study, we examined size evolution in monitor lizards (Varanus), a clade that includes the largest extant lizard species, the Komodo dragon (V. komodoensis), as well as diminutive species that are nearly four orders of magnitude smaller in adult body mass. We demonstrate that the remarkable body size disparity of this clade is a consequence of different selective demands imposed by three major habitat use patterns-arboreality, terrestriality, and rock-dwelling. We reconstructed phylogenetic relationships and ancestral habitat use and applied model selection to determine that the best-fitting evolutionary models for species' adult size are those that infer oppositely directed adaptive evolution associated with terrestriality and rock-dwelling, with terrestrial lineages evolving extremely large size and rock-dwellers becoming very small. We also show that habitat use affects the evolution of several ecologically important morphological traits independently of body size divergence. These results suggest that habitat use exerts a strong, multidimensional influence on the evolution of morphological size and shape disparity in monitor lizards. © 2011 The Author(s).

Evolution of the brain and phylogenetic development of Mrican ...

African Journals Online (AJOL)

Evolution of the brain and phylogenetic development of Mrican Bovidae. Henriette Oboussier. Zoological Institute and Museum, University of Hamburg. Evidence drawn from the study of 270 brains of 54 species and subspecies of African Bovidae makes it possible to base phylogenetic relationships on the similarities in the ...

Relative brain size and morphology of some South African bats ...

African Journals Online (AJOL)

Measures of relative brain size and brain macromorphology are described for four species of Microchiroptera, two from the Vespertilionidae and two from the Rhinolophidae, and two species from the Pteropodidae (Megachiroptera). Four brain parameters (brain length, hemisphere length, brain width and brain height) were ...

The tempo and mode of evolution: body sizes of island mammals.

Science.gov (United States)

Raia, Pasquale; Meiri, Shai

2011-07-01

The tempo and mode of body size evolution on islands are believed to be well known. It is thought that body size evolves relatively quickly on islands toward the mammalian modal value, thus generating extreme cases of size evolution and the island rule. Here, we tested both theories in a phylogenetically explicit context, by using two different species-level mammalian phylogenetic hypotheses limited to sister clades dichotomizing into an exclusively insular and an exclusively mainland daughter nodes. Taken as a whole, mammals were found to show a largely punctuational mode of size evolution. We found that, accounting for this, and regardless of the phylogeny used, size evolution on islands is no faster than on the continents. We compared different selection regimes using a set of Ornstein-Uhlenbeck models to examine the effects of insularity of the mode of evolution. The models strongly supported clade-specific selection regimes. Under this regime, however, an evolutionary model allowing insular species to evolve differently from their mainland relatives performs worse than a model that ignores insularity as a factor. Thus, insular taxa do not experience statistically different selection from their mainland relatives. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.

Phylogeny suggests nondirectional and isometric evolution of sexual size dimorphism in argiopine spiders.

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Cheng, Ren-Chung; Kuntner, Matjaž

2014-10-01

Sexual dimorphism describes substantial differences between male and female phenotypes. In spiders, sexual dimorphism research almost exclusively focuses on size, and recent studies have recovered steady evolutionary size increases in females, and independent evolutionary size changes in males. Their discordance is due to negative allometric size patterns caused by different selection pressures on male and female sizes (converse Rensch's rule). Here, we investigated macroevolutionary patterns of sexual size dimorphism (SSD) in Argiopinae, a global lineage of orb-weaving spiders with varying degrees of SSD. We devised a Bayesian and maximum-likelihood molecular species-level phylogeny, and then used it to reconstruct sex-specific size evolution, to examine general hypotheses and different models of size evolution, to test for sexual size coevolution, and to examine allometric patterns of SSD. Our results, revealing ancestral moderate sizes and SSD, failed to reject the Brownian motion model, which suggests a nondirectional size evolution. Contrary to predictions, male and female sizes were phylogenetically correlated, and SSD evolution was isometric. We interpret these results to question the classical explanations of female-biased SSD via fecundity, gravity, and differential mortality. In argiopines, SSD evolution may be driven by these or additional selection mechanisms, but perhaps at different phylogenetic scales. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

The Co-evolution of Language and the Brain: A Review of Two Contrastive Views (Pinker & Deacon)

DEFF Research Database (Denmark)

Christensen, Ken Ramshøj

2001-01-01

in a larger symbolic computational chain controlled by regions in the frontal parts of the brain. To Deacon, a symbolic learning algorithm drives language acquisition. The increase in size of the human brain in relation to the body may be due to a “cognitive arms race”. Both Pinker and Deacon agree......This article is a review of two contrastive views on the co-evolution of language and the brain – The Language Instinct by Steven Pinker (1994) and The Symbolic Species by Terrence Deacon (1997). As language is a trait unique to mankind it can not be equated with nonlinguistic communication – human...... or nonhuman. This points to a special human brain architecture. Pinker’s claim is that certain areas on the left side of the brain constitute a language organ and that language acquisition is instinctual. To Deacon, however, those areas are non-language-specific computational centers. Moreover, they are parts...

The Evolution of Clutch Size in Hosts of Avian Brood Parasites.

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Medina, Iliana; Langmore, Naomi E; Lanfear, Robert; Kokko, Hanna

2017-11-01

Coevolution with avian brood parasites shapes a range of traits in their hosts, including morphology, behavior, and breeding systems. Here we explore whether brood parasitism is also associated with the evolution of host clutch size. Several studies have proposed that hosts of highly virulent parasites could decrease the costs of parasitism by evolving a smaller clutch size, because hosts with smaller clutches will lose fewer progeny when their clutch is parasitized. We describe a model of the evolution of clutch size, which challenges this logic and shows instead that an increase in clutch size (or no change) should evolve in hosts. We test this prediction using a broad-scale comparative analysis to ask whether there are differences in clutch size within hosts and between hosts and nonhosts. Consistent with our model, this analysis revealed that host species do not have smaller clutches and that hosts that incur larger costs from raising a parasite lay larger clutches. We suggest that brood parasitism might be an influential factor in clutch-size evolution and could potentially select for the evolution of larger clutches in host species.

Comparative support for the expensive tissue hypothesis: Big brains are correlated with smaller gut and greater parental investment in Lake Tanganyika cichlids.

Science.gov (United States)

Tsuboi, Masahito; Husby, Arild; Kotrschal, Alexander; Hayward, Alexander; Buechel, Séverine D; Zidar, Josefina; Løvlie, Hanne; Kolm, Niclas

2015-01-01

The brain is one of the most energetically expensive organs in the vertebrate body. Consequently, the energetic requirements of encephalization are suggested to impose considerable constraints on brain size evolution. Three main hypotheses concerning how energetic constraints might affect brain evolution predict covariation between brain investment and (1) investment into other costly tissues, (2) overall metabolic rate, and (3) reproductive investment. To date, these hypotheses have mainly been tested in homeothermic animals and the existing data are inconclusive. However, there are good reasons to believe that energetic limitations might play a role in large-scale patterns of brain size evolution also in ectothermic vertebrates. Here, we test these hypotheses in a group of ectothermic vertebrates, the Lake Tanganyika cichlid fishes. After controlling for the effect of shared ancestry and confounding ecological variables, we find a negative association between brain size and gut size. Furthermore, we find that the evolution of a larger brain is accompanied by increased reproductive investment into egg size and parental care. Our results indicate that the energetic costs of encephalization may be an important general factor involved in the evolution of brain size also in ectothermic vertebrates. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

Optimized temporal pattern of brain stimulation designed by computational evolution.

Science.gov (United States)

Brocker, David T; Swan, Brandon D; So, Rosa Q; Turner, Dennis A; Gross, Robert E; Grill, Warren M

2017-01-04

Brain stimulation is a promising therapy for several neurological disorders, including Parkinson's disease. Stimulation parameters are selected empirically and are limited to the frequency and intensity of stimulation. We varied the temporal pattern of deep brain stimulation to ameliorate symptoms in a parkinsonian animal model and in humans with Parkinson's disease. We used model-based computational evolution to optimize the stimulation pattern. The optimized pattern produced symptom relief comparable to that from standard high-frequency stimulation (a constant rate of 130 or 185 Hz) and outperformed frequency-matched standard stimulation in a parkinsonian rat model and in patients. Both optimized and standard high-frequency stimulation suppressed abnormal oscillatory activity in the basal ganglia of rats and humans. The results illustrate the utility of model-based computational evolution of temporal patterns to increase the efficiency of brain stimulation in treating Parkinson's disease and thereby reduce the energy required for successful treatment below that of current brain stimulation paradigms. Copyright © 2017, American Association for the Advancement of Science.

COSMIC EVOLUTION OF SIZE AND VELOCITY DISPERSION FOR EARLY-TYPE GALAXIES

International Nuclear Information System (INIS)

Fan, L.; Lapi, A.; Bressan, A.; De Zotti, G.; Danese, L.; Bernardi, M.

2010-01-01

Massive (stellar mass M * ∼> 3 x 10 10 M sun ), passively evolving galaxies at redshifts z ∼> 1 exhibit on average physical sizes smaller, by factors ∼3, than local early-type galaxies (ETGs) endowed with the same stellar mass. Small sizes are in fact expected on theoretical grounds, if dissipative collapse occurs. Recent results show that the size evolution at z ∼ 1, where both compact and already extended galaxies are observed and the scatter in size is remarkably larger than it is locally. The presence at high redshift of a significant number of ETGs with the same size as their local counterparts, as well as ETGs with quite small size (∼ H (z). We demonstrate that the projected mass of compact, high-redshift galaxies and that of local ETGs within the same physical radius, the nominal half-luminosity radius of high-redshift ETGs, differ substantially in that the high-redshift ETGs are on average significantly denser. This result suggests that the physical mechanism responsible for the size increase should also remove mass from central galaxy regions (r ∼ 1, we predict the local velocity dispersion distribution function. On comparing it to the observed one, we show that velocity dispersion evolution of massive ETGs is fully compatible with the observed average evolution in size at constant stellar mass. Less massive ETGs (with stellar masses M * ∼ 10 M sun ) are expected to evolve less both in size and in velocity dispersion, because their evolution is essentially determined by supernova feedback, which cannot yield winds as powerful as those triggered by quasars. The differential evolution is expected to leave imprints in the size versus luminosity/mass, velocity dispersion versus luminosity/mass, and central black hole mass versus velocity dispersion relationships, as observed in local ETGs.

The evolution of bacterial cell size: the internal diffusion-constraint hypothesis.

Science.gov (United States)

Gallet, Romain; Violle, Cyrille; Fromin, Nathalie; Jabbour-Zahab, Roula; Enquist, Brian J; Lenormand, Thomas

2017-07-01

Size is one of the most important biological traits influencing organismal ecology and evolution. However, we know little about the drivers of body size evolution in unicellulars. A long-term evolution experiment (Lenski's LTEE) in which Escherichia coli adapts to a simple glucose medium has shown that not only the growth rate and the fitness of the bacterium increase over time but also its cell size. This increase in size contradicts prominent 'external diffusion' theory (EDC) predicting that cell size should have evolved toward smaller cells. Among several scenarios, we propose and test an alternative 'internal diffusion-constraint' (IDC) hypothesis for cell size evolution. A change in cell volume affects metabolite concentrations in the cytoplasm. The IDC states that a higher metabolism can be achieved by a reduction in the molecular traffic time inside of the cell, by increasing its volume. To test this hypothesis, we studied a population from the LTEE. We show that bigger cells with greater growth and CO 2 production rates and lower mass-to-volume ratio were selected over time in the LTEE. These results are consistent with the IDC hypothesis. This novel hypothesis offers a promising approach for understanding the evolutionary constraints on cell size.

Social intelligence, innovation, and enhanced brain size in primates

NARCIS (Netherlands)

Reader, S.M.; Laland, K.N.

2002-01-01

Despite considerable current interest in the evolution of intelligence, the intuitively appealing notion that brain volume and ‘‘intelligence’’ are linked remains untested. Here, we use ecologically relevant measures of cognitive ability, the reported incidence of behavioral innovation, social

Evolution of body size in Galapagos marine iguanas.

Science.gov (United States)

Wikelski, Martin

2005-10-07

Body size is one of the most important traits of organisms and allows predictions of an individual's morphology, physiology, behaviour and life history. However, explaining the evolution of complex traits such as body size is difficult because a plethora of other traits influence body size. Here I review what we know about the evolution of body size in a group of island reptiles and try to generalize about the mechanisms that shape body size. Galapagos marine iguanas occupy all 13 larger islands in this Pacific archipelago and have maximum island body weights between 900 and 12 000g. The distribution of body sizes does not match mitochondrial clades, indicating that body size evolves independently of genetic relatedness. Marine iguanas lack intra- and inter-specific food competition and predators are not size-specific, discounting these factors as selective agents influencing body size. Instead I hypothesize that body size reflects the trade-offs between sexual and natural selection. We found that sexual selection continuously favours larger body sizes. Large males establish display territories and some gain over-proportional reproductive success in the iguanas' mating aggregations. Females select males based on size and activity and are thus responsible for the observed mating skew. However, large individuals are strongly selected against during El Niño-related famines when dietary algae disappear from the intertidal foraging areas. We showed that differences in algae sward ('pasture') heights and thermal constraints on large size are causally responsible for differences in maximum body size among populations. I hypothesize that body size in many animal species reflects a trade-off between foraging constraints and sexual selection and suggest that future research could focus on physiological and genetic mechanisms determining body size in wild animals. Furthermore, evolutionary stable body size distributions within populations should be analysed to better

Re-evaluating the link between brain size and behavioural ecology in primates.

Science.gov (United States)

Powell, Lauren E; Isler, Karin; Barton, Robert A

2017-10-25

Comparative studies have identified a wide range of behavioural and ecological correlates of relative brain size, with results differing between taxonomic groups, and even within them. In primates for example, recent studies contradict one another over whether social or ecological factors are critical. A basic assumption of such studies is that with sufficiently large samples and appropriate analysis, robust correlations indicative of selection pressures on cognition will emerge. We carried out a comprehensive re-examination of correlates of primate brain size using two large comparative datasets and phylogenetic comparative methods. We found evidence in both datasets for associations between brain size and ecological variables (home range size, diet and activity period), but little evidence for an effect of social group size, a correlation which has previously formed the empirical basis of the Social Brain Hypothesis. However, reflecting divergent results in the literature, our results exhibited instability across datasets, even when they were matched for species composition and predictor variables. We identify several potential empirical and theoretical difficulties underlying this instability and suggest that these issues raise doubts about inferring cognitive selection pressures from behavioural correlates of brain size. © 2017 The Author(s).

Evidence of size-selective evolution in the fighting conch from prehistoric subsistence harvesting.

Science.gov (United States)

O'Dea, Aaron; Shaffer, Marian Lynne; Doughty, Douglas R; Wake, Thomas A; Rodriguez, Felix A

2014-05-07

Intensive size-selective harvesting can drive evolution of sexual maturity at smaller body size. Conversely, prehistoric, low-intensity subsistence harvesting is not considered an effective agent of size-selective evolution. Uniting archaeological, palaeontological and contemporary material, we show that size at sexual maturity in the edible conch Strombus pugilis declined significantly from pre-human (approx. 7 ka) to prehistoric times (approx. 1 ka) and again to the present day. Size at maturity also fell from early- to late-prehistoric periods, synchronous with an increase in harvesting intensity as other resources became depleted. A consequence of declining size at maturity is that early prehistoric harvesters would have received two-thirds more meat per conch than contemporary harvesters. After exploring the potential effects of selection biases, demographic shifts, environmental change and habitat alteration, these observations collectively implicate prehistoric subsistence harvesting as an agent of size-selective evolution with long-term detrimental consequences. We observe that contemporary populations that are protected from harvesting are slightly larger at maturity, suggesting that halting or even reversing thousands of years of size-selective evolution may be possible.

The evolution of test size in the Planktic Foraminifera

Science.gov (United States)

Fraass, A.; Huber, B. T.; Kelly, D. C.

2017-12-01

Planktic foraminifera are vital tools for understanding paleoceanography, paleoclimate, and evolution. A dataset of measurements from all planktic foraminiferal species is used here to investigate how their size changes through the late Jurassic to Recent. The mean test size of planktic foraminifera increases in the Cretaceous and the Cenozoic, with substantial drops at the Aptian/Albian boundary, in the Coniacian and Santonian, with the end-Cretaceous extinction, and across the Paleocene/Eocene boundary. The Oligocene contains only a small drop in mean size, which is surprising given the substantial extinction of planktic foraminifera at that boundary. There is a qualitative connection between mean and median size and paleoceanographic events, but several key issues remain before rigorous quantitative interrogation of the dataset can be undertaken. In general, species that originate early in a family's range are smaller than those evolving later, though this is a weak relationship. Individual families do not always conform to that finding, however, and have both increasing and decreasing family age-size relationships. The 'three faunas' concept for foraminiferal evolution fails with respect to mean and median size; each diversification has a unique rate of increase and character. Lastly, through comparison with the Schmidt et al. (2004) population-level test size dataset, the size response to climate in the low-latitudes is at the species-level. In the high-latitude regions, however, the response to climate is at the population level. Thus, methods for uncovering climate responses in planktic foraminifera must be specific to the region. Taxonomic or macroevolutionary responses dominate the tropics and global signals, while the polar regions appear to have a unique, and more microevolutionary response.Schmidt, D., Thierstein, H., Bollmann, J., & Schiebel, R. (2004). Abiotic Forcing of Plankton Evolution in the Cenozoic. Science, 303(5655), 207-210.

Multiple determinants of whole and regional brain volume among terrestrial carnivorans.

Directory of Open Access Journals (Sweden)

Eli M Swanson

Full Text Available Mammalian brain volumes vary considerably, even after controlling for body size. Although several hypotheses have been proposed to explain this variation, most research in mammals on the evolution of encephalization has focused on primates, leaving the generality of these explanations uncertain. Furthermore, much research still addresses only one hypothesis at a time, despite the demonstrated importance of considering multiple factors simultaneously. We used phylogenetic comparative methods to investigate simultaneously the importance of several factors previously hypothesized to be important in neural evolution among mammalian carnivores, including social complexity, forelimb use, home range size, diet, life history, phylogeny, and recent evolutionary changes in body size. We also tested hypotheses suggesting roles for these variables in determining the relative volume of four brain regions measured using computed tomography. Our data suggest that, in contrast to brain size in primates, carnivoran brain size may lag behind body size over evolutionary time. Moreover, carnivore species that primarily consume vertebrates have the largest brains. Although we found no support for a role of social complexity in overall encephalization, relative cerebrum volume correlated positively with sociality. Finally, our results support negative relationships among different brain regions after accounting for overall endocranial volume, suggesting that increased size of one brain regions is often accompanied by reduced size in other regions rather than overall brain expansion.

Virtual endocasts of Eocene Paramys (Paramyinae): oldest endocranial record for Rodentia and early brain evolution in Euarchontoglires.

Science.gov (United States)

Bertrand, Ornella C; Amador-Mughal, Farrah; Silcox, Mary T

2016-01-27

Understanding the pattern of brain evolution in early rodents is central to reconstructing the ancestral condition for Glires, and for other members of Euarchontoglires including Primates. We describe the oldest virtual endocasts known for fossil rodents, which pertain to Paramys copei (Early Eocene) and Paramys delicatus (Middle Eocene). Both specimens of Paramys have larger olfactory bulbs and smaller paraflocculi relative to total endocranial volume than later occurring rodents, which may be primitive traits for Rodentia. The encephalization quotients (EQs) of Pa. copei and Pa. delicatus are higher than that of later occurring (Oligocene) Ischyromys typus, which contradicts the hypothesis that EQ increases through time in all mammalian orders. However, both species of Paramys have a lower relative neocortical surface area than later rodents, suggesting neocorticalization occurred through time in this Order, although to a lesser degree than in Primates. Paramys has a higher EQ but a lower neocortical ratio than any stem primate. This result contrasts with the idea that primates were always exceptional in their degree of overall encephalization and shows that relative brain size and neocortical surface area do not necessarily covary through time. As such, these data contradict assumptions made about the pattern of brain evolution in Euarchontoglires. © 2016 The Author(s).

Evolution of the human brain : when bigger is better

NARCIS (Netherlands)

Hofman, Michel A

2014-01-01

Comparative studies of the brain in mammals suggest that there are general architectural principles governing its growth and evolutionary development. We are beginning to understand the geometric, biophysical and energy constraints that have governed the evolution and functional organization of the

Is the social brain theory applicable to human individual differences? Relationship between sociability personality dimension and brain size.

Science.gov (United States)

Horváth, Klára; Martos, János; Mihalik, Béla; Bódizs, Róbert

2011-06-17

Our study intends to examine whether the social brain theory is applicable to human individual differences. According to the social brain theory primates have larger brains as it could be expected from their body sizes due to the adaptation to a more complex social life. Regarding humans there were few studies about the relationship between theory of mind and frontal and temporal brain lobes. We hypothesized that these brain lobes, as well as the whole cerebrum and neocortex are in connection with the Sociability personality dimension that is associated with individuals' social lives. Our findings support this hypothesis as Sociability correlated positively with the examined brain structures if we control the effects of body size differences and age. These results suggest that the social brain theory can be extended to human interindividual differences and they have some implications to personality psychology too.

Evidence of size-selective evolution in the fighting conch from prehistoric subsistence harvesting

OpenAIRE

O'Dea, Aaron; Shaffer, Marian Lynne; Doughty, Douglas R.; Wake, Thomas A.; Rodriguez, Felix A.

2014-01-01

Intensive size-selective harvesting can drive evolution of sexual maturity at smaller body size. Conversely, prehistoric, low-intensity subsistence harvesting is not considered an effective agent of size-selective evolution. Uniting archaeological, palaeontological and contemporary material, we show that size at sexual maturity in the edible conch Strombus pugilis declined significantly from pre-human (approx. 7 ka) to prehistoric times (approx. 1 ka) and again to the present day. Size at mat...

A biometric analysis of brain size in micrencephalics.

Science.gov (United States)

Hofman, M A

1984-01-01

Brain weight and head circumference in micrencephalic patients were analysed as a function of age, height and sex in relation to normal human standards. A quantitative definition of micrencephaly is proposed, which is based on these analyses. Evidence is presented, furthermore, that micrencephalics have a significantly lower brain weight in adolescence than in early childhood, and that this cerebral dystrophy continues throughout adulthood, leading to death in more than 85% of the males and 78% of the females before they reach the age of 30 years. Since this decline in brain weight after approximately 3-5 years of age is not accompanied by a similar reduction in head circumference, the brains of elderly micrencephalic patients no longer occupy the entire cranial cavity. It is evident, therefore, that head circumference in the case of micrencephaly is an unsuitable parameter for estimating brain size.

ON THE SIZE AND COMOVING MASS DENSITY EVOLUTION OF EARLY-TYPE GALAXIES

International Nuclear Information System (INIS)

Van der Wel, Arjen; Bell, Eric F.; Van den Bosch, Frank C.; Gallazzi, Anna; Rix, Hans-Walter

2009-01-01

We present a simple, empirically motivated model that simultaneously predicts the evolution of the mean size and the comoving mass density of massive (>10 11 M sun ) early-type galaxies from z = 2 to the present. First, we demonstrate that some size evolution of the population can be expected simply due to the continuous emergence of early-type galaxies. The Sloan Digital Sky Survey (SDSS) data reveal that in the present-day universe more compact early-type galaxies with a given dynamical mass have older stellar populations. This implies that with increasing look-back time, the more extended galaxies will be more and more absent from the population. In contrast, at a given stellar velocity dispersion, SDSS data show that there is no relation between size and age, which implies that the velocity dispersion can be used to estimate the epoch at which galaxies stopped forming stars, turning into early-type galaxies. Based on this, we define an empirically motivated, redshift-dependent velocity dispersion threshold above which galaxies do not form stars at a significant rate, which we associate with the transformation into early-type galaxies. Applying this 'formation' criterion to a large sample of nearby early-type galaxies, we predict the redshift evolution in the size distribution and the comoving mass density. The resulting evolution in the mean size is roughly half of the observed evolution. Then we include a prescription for the merger histories of galaxies between the 'formation' redshift and the present, based on cosmological simulations of the assembly of dark matter halos. Such mergers after the transformation into an early-type galaxy are presumably dissipationless ('dry'), where the increase in size is expected to be approximately proportional to the increase in mass. This model successfully reproduces the observed evolution since z ∼ 2 in the mean size and in the comoving mass density of early-type galaxies with mass M > 10 11 M sun . We conclude that

Female brain size affects the assessment of male attractiveness during mate choice.

Science.gov (United States)

Corral-López, Alberto; Bloch, Natasha I; Kotrschal, Alexander; van der Bijl, Wouter; Buechel, Severine D; Mank, Judith E; Kolm, Niclas

2017-03-01

Mate choice decisions are central in sexual selection theory aimed to understand how sexual traits evolve and their role in evolutionary diversification. We test the hypothesis that brain size and cognitive ability are important for accurate assessment of partner quality and that variation in brain size and cognitive ability underlies variation in mate choice. We compared sexual preference in guppy female lines selected for divergence in relative brain size, which we have previously shown to have substantial differences in cognitive ability. In a dichotomous choice test, large-brained and wild-type females showed strong preference for males with color traits that predict attractiveness in this species. In contrast, small-brained females showed no preference for males with these traits. In-depth analysis of optomotor response to color cues and gene expression of key opsins in the eye revealed that the observed differences were not due to differences in visual perception of color, indicating that differences in the ability to process indicators of attractiveness are responsible. We thus provide the first experimental support that individual variation in brain size affects mate choice decisions and conclude that differences in cognitive ability may be an important underlying mechanism behind variation in female mate choice.

Smaller beaks for colder winters: Thermoregulation drives beak size evolution in Australasian songbirds.

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Friedman, Nicholas R; Harmáčková, Lenka; Economo, Evan P; Remeš, Vladimír

2017-08-01

Birds' beaks play a key role in foraging, and most research on their size and shape has focused on this function. Recent findings suggest that beaks may also be important for thermoregulation, and this may drive morphological evolution as predicted by Allen's rule. However, the role of thermoregulation in the evolution of beak size across species remains largely unexplored. In particular, it remains unclear whether the need for retaining heat in the winter or dissipating heat in the summer plays the greater role in selection for beak size. Comparative studies are needed to evaluate the relative importance of these functions in beak size evolution. We addressed this question in a clade of birds exhibiting wide variation in their climatic niche: the Australasian honeyeaters and allies (Meliphagoidea). Across 158 species, we compared species' climatic conditions extracted from their ranges to beak size measurements in a combined spatial-phylogenetic framework. We found that winter minimum temperature was positively correlated with beak size, while summer maximum temperature was not. This suggests that while diet and foraging behavior may drive evolutionary changes in beak shape, changes in beak size can also be explained by the beak's role in thermoregulation, and winter heat retention in particular. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

Effects of grain size evolution on mantle dynamics

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Schulz, Falko; Tosi, Nicola; Plesa, Ana-Catalina; Breuer, Doris

2016-04-01

The rheology of planetary mantle materials is strongly dependent on temperature, pressure, strain-rate, and grain size. In particular, the rheology of olivine, the most abundant mineral of the Earth's upper mantle, has been extensively studied in the laboratory (e.g., Karato and Wu, 1993; Hirth and Kohlstedt, 2003). Two main mechanisms control olivine's deformation: dislocation and diffusion creep. While the former implies a power-law dependence of the viscosity on the strain-rate that leads to a non-Newtonian behaviour, the latter is sensitively dependent on the grain size. The dynamics of planetary interiors is locally controlled by the deformation mechanism that delivers the lowest viscosity. Models of the dynamics and evolution of planetary mantles should thus be capable to self-consistently distinguish which of the two mechanisms dominates at given conditions of temperature, pressure, strain-rate and grain size. As the grain size can affect the viscosity associated with diffusion creep by several orders of magnitude, it can strongly influence the dominant deformation mechanism. The vast majority of numerical, global-scale models of mantle convection, however, are based on the use of a linear diffusion-creep rheology with constant grain-size. Nevertheless, in recent studies, a new equation has been proposed to properly model the time-dependent evolution of the grain size (Austin and Evens, 2007; Rozel et al., 2010). We implemented this equation in our mantle convection code Gaia (Hüttig et al., 2013). In the framework of simple models of stagnant lid convection, we compared simulations based on the fully time-dependent equation of grain-size evolution with simulations based on its steady-state version. In addition, we tested a number of different parameters in order to identify those that affects the grain size to the first order and, in turn, control the conditions at which mantle deformation is dominated by diffusion or dislocation creep. References Austin

Are rates of species diversification and body size evolution coupled in the ferns?

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Testo, Weston L; Sundue, Michael A

2018-03-01

Understanding the relationship between phenotypic evolution and lineage diversification is a central goal of evolutionary biology. To extend our understanding of the role morphological evolution plays in the diversification of plants, we examined the relationship between leaf size evolution and lineage diversification across ferns. We tested for an association between body size evolution and lineage diversification using a comparative phylogenetic approach that combined a time-calibrated phylogeny and leaf size data set for 2654 fern species. Rates of leaf size change and lineage diversification were estimated using BAMM, and rate correlations were performed for rates obtained for all families and individual species. Rates and patterns of rate-rate correlation were also analyzed separately for terrestrial and epiphytic taxa. We find no significant correlation between rates of leaf area change and lineage diversification, nor was there a difference in this pattern when growth habit is considered. Our results are consistent with the findings of an earlier study that reported decoupled rates of body size evolution and diversification in the Polypodiaceae, but conflict with a recent study that reported a positive correlation between body size evolution and lineage diversification rates in the tree fern family Cyatheaceae. Our findings indicate that lineage diversification in ferns is largely decoupled from shifts in body size, in contrast to several other groups of organisms. Speciation in ferns appears to be primarily driven by hybridization and isolation along elevational gradients, rather than adaptive radiations featuring prominent morphological restructuring. The exceptional diversity of leaf morphologies in ferns appears to reflect a combination of ecophysiological constraints and adaptations that are not key innovations. © 2018 Botanical Society of America.

Smart moves: effects of relative brain size on establishment success of invasive amphibians and reptiles.

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Amiel, Joshua J; Tingley, Reid; Shine, Richard

2011-04-06

Brain size relative to body size varies considerably among animals, but the ecological consequences of that variation remain poorly understood. Plausibly, larger brains confer increased behavioural flexibility, and an ability to respond to novel challenges. In keeping with that hypothesis, successful invasive species of birds and mammals that flourish after translocation to a new area tend to have larger brains than do unsuccessful invaders. We found the same pattern in ectothermic terrestrial vertebrates. Brain size relative to body size was larger in species of amphibians and reptiles reported to be successful invaders, compared to species that failed to thrive after translocation to new sites. This pattern was found in six of seven global biogeographic realms; the exception (where relatively larger brains did not facilitate invasion success) was Australasia. Establishment success was also higher in amphibian and reptile families with larger relative brain sizes. Future work could usefully explore whether invasion success is differentially associated with enlargement of specific parts of the brain (as predicted by the functional role of the forebrain in promoting behavioural flexibility), or with a general size increase (suggesting that invasion success is facilitated by enhanced perceptual and motor skills, as well as cognitive ability).

Friends with Social Benefits: Host-Microbe Interactions as a Driver of Brain Evolution and Development?

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Roman M Stilling

2014-10-01

Full Text Available The tight association of the human body with trillions of colonizing microbes that we observe today is the result of a long evolutionary history. Only very recently have we started to understand how this symbiosis also affects brain function and behaviour. Here in this hypothesis and theory article, we propose how host-microbe associations potentially influenced mammalian brain evolution and development. In particular, we explore the integration of human brain development with evolution, symbiosis, and RNA biology, which together represent a ‘social triangle’ that drives human social behaviour and cognition. We argue that, in order to understand how inter-kingdom communication can affect brain adaptation and plasticity, it is inevitable to consider epigenetic mechanisms as important mediators of genome-microbiome interactions on an individual as well as a transgenerational time scale. Finally, we unite these interpretations with the hologenome theory of evolution. Taken together, we propose a tighter integration of neuroscience fields with host-associated microbiology by taking an evolutionary perspective.

Smart Moves: Effects of Relative Brain Size on Establishment Success of Invasive Amphibians and Reptiles

Science.gov (United States)

Amiel, Joshua J.; Tingley, Reid; Shine, Richard

2011-01-01

Brain size relative to body size varies considerably among animals, but the ecological consequences of that variation remain poorly understood. Plausibly, larger brains confer increased behavioural flexibility, and an ability to respond to novel challenges. In keeping with that hypothesis, successful invasive species of birds and mammals that flourish after translocation to a new area tend to have larger brains than do unsuccessful invaders. We found the same pattern in ectothermic terrestrial vertebrates. Brain size relative to body size was larger in species of amphibians and reptiles reported to be successful invaders, compared to species that failed to thrive after translocation to new sites. This pattern was found in six of seven global biogeographic realms; the exception (where relatively larger brains did not facilitate invasion success) was Australasia. Establishment success was also higher in amphibian and reptile families with larger relative brain sizes. Future work could usefully explore whether invasion success is differentially associated with enlargement of specific parts of the brain (as predicted by the functional role of the forebrain in promoting behavioural flexibility), or with a general size increase (suggesting that invasion success is facilitated by enhanced perceptual and motor skills, as well as cognitive ability). PMID:21494328

Smart moves: effects of relative brain size on establishment success of invasive amphibians and reptiles.

Directory of Open Access Journals (Sweden)

Joshua J Amiel

2011-04-01

Full Text Available Brain size relative to body size varies considerably among animals, but the ecological consequences of that variation remain poorly understood. Plausibly, larger brains confer increased behavioural flexibility, and an ability to respond to novel challenges. In keeping with that hypothesis, successful invasive species of birds and mammals that flourish after translocation to a new area tend to have larger brains than do unsuccessful invaders. We found the same pattern in ectothermic terrestrial vertebrates. Brain size relative to body size was larger in species of amphibians and reptiles reported to be successful invaders, compared to species that failed to thrive after translocation to new sites. This pattern was found in six of seven global biogeographic realms; the exception (where relatively larger brains did not facilitate invasion success was Australasia. Establishment success was also higher in amphibian and reptile families with larger relative brain sizes. Future work could usefully explore whether invasion success is differentially associated with enlargement of specific parts of the brain (as predicted by the functional role of the forebrain in promoting behavioural flexibility, or with a general size increase (suggesting that invasion success is facilitated by enhanced perceptual and motor skills, as well as cognitive ability.

Evolution of Brain Tumor and Stability of Geometric Invariants

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K. Tawbe

2008-01-01

Full Text Available This paper presents a method to reconstruct and to calculate geometric invariants on brain tumors. The geometric invariants considered in the paper are the volume, the area, the discrete Gauss curvature, and the discrete mean curvature. The volume of a tumor is an important aspect that helps doctors to make a medical diagnosis. And as doctors seek a stable calculation, we propose to prove the stability of some invariants. Finally, we study the evolution of brain tumor as a function of time in two or three years depending on patients with MR images every three or six months.

Tipping the scales: Evolution of the allometric slope independent of average trait size.

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Stillwell, R Craig; Shingleton, Alexander W; Dworkin, Ian; Frankino, W Anthony

2016-02-01

The scaling of body parts is central to the expression of morphology across body sizes and to the generation of morphological diversity within and among species. Although patterns of scaling-relationship evolution have been well documented for over one hundred years, little is known regarding how selection acts to generate these patterns. In part, this is because it is unclear the extent to which the elements of log-linear scaling relationships-the intercept or mean trait size and the slope-can evolve independently. Here, using the wing-body size scaling relationship in Drosophila melanogaster as an empirical model, we use artificial selection to demonstrate that the slope of a morphological scaling relationship between an organ (the wing) and body size can evolve independently of mean organ or body size. We discuss our findings in the context of how selection likely operates on morphological scaling relationships in nature, the developmental basis for evolved changes in scaling, and the general approach of using individual-based selection experiments to study the expression and evolution of morphological scaling. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Human brain evolution, theories of innovation, and lessons from the ...

Indian Academy of Sciences (India)

Home; Journals; Journal of Biosciences; Volume 29; Issue 3. Human brain evolution, theories of innovation, and lessons from the history of technology. Alfred Gierer. Perspectives Volume 29 Issue 3 September 2004 pp 235-244. Fulltext. Click here to view fulltext PDF. Permanent link:

The genetic basis of natural variation in mushroom body size in Drosophila melanogaster.

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Zwarts, Liesbeth; Vanden Broeck, Lies; Cappuyns, Elisa; Ayroles, Julien F; Magwire, Michael M; Vulsteke, Veerle; Clements, Jason; Mackay, Trudy F C; Callaerts, Patrick

2015-12-11

Genetic variation in brain size may provide the basis for the evolution of the brain and complex behaviours. The genetic substrate and the selective pressures acting on brain size are poorly understood. Here we use the Drosophila Genetic Reference Panel to map polymorphic variants affecting natural variation in mushroom body morphology. We identify 139 genes and 39 transcription factors and confirm effects on development and adult plasticity. We show correlations between morphology and aggression, sleep and lifespan. We propose that natural variation in adult brain size is controlled by interaction of the environment with gene networks controlling development and plasticity.

Long-term evolution of cerebral hemodynamics after brain irradiation in the rat

International Nuclear Information System (INIS)

Keyeux, A.; Ochrymowicz-Bemelmans, D.

1985-01-01

Long-term evolution of radioisotope indices, evaluating respectively the cerebral blood flow (CBF), the cerebral blood volume (CBV) and the cephalic specific distribution space of iodoantipyrine (ΔIAP) of rat, was studied after brain irradiation at 20 Gy. Radioinduced hemodynamic alterations evidenced by this approach are biphasic and support the prominent role of circulation impairment in the genesis of delayed brain radionecrosis [fr

Evolution in linear sizes and the Faraday effects in radio sources

International Nuclear Information System (INIS)

Anene, G.; Ugwoke, A.C.

2001-05-01

It is still a matter of conjecture whether the observed depolarization in radio sources originate from an external Faraday screen lying in our line of sight, or is largely due to internal processes occurring within these sources. This paper argues for an external origin. By applying recent evidences from the evolution of linear sizes while allowing for selection effects, it is shown that the density parameters within radio sources do not depend on redshift, implying that the observed depolarizations is epoch independent and may therefore, be largely external in origin. We also show that the observed low correlation between λ 1/2 and linear size(D) cannot be improved much even when allowance is made for evolution in D. (author)

A conceptual framework for clutch size evolution in songbirds

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Martin, Thomas E.

2014-01-01

Causes of evolved differences in clutch size among songbird species remain debated. I propose a new conceptual framework that integrates aspects of traditional life history theory, while including novel elements, to explain evolution of clutch size among songbirds. I review evidence that selection by nest predation on length of time that offspring develop in the nest creates a gradient in offspring characteristics at nest-leaving (fledging), including flight mobility, spatial dispersion, and self-feeding rate. I postulate that this gradient has consequences for offspring mortality rates and parental energy expenditure per offspring. These consequences then determine how reproductive effort is partitioned among offspring, while reproductive effort evolves from age-specific mortality effects. Using data from a long-term site in Arizona, as well as from the literature, I provide support for hypothesized relationships. Nestling development period consistently explains fledgling mortality, energy expenditure per offspring, and clutch size while accounting for reproductive effort (i.e., total energy expenditure) to thereby support the framework. Tests in this paper are not definitive, but they document previously unrecognized relationships and address diverse traits (developmental strategies, parental care strategies, energy requirements per offspring, evolution of reproductive effort, clutch size) that justify further investigations of hypotheses proposed here.

Handedness- and brain size-related efficiency differences in small-world brain networks: a resting-state functional magnetic resonance imaging study.

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Li, Meiling; Wang, Junping; Liu, Feng; Chen, Heng; Lu, Fengmei; Wu, Guorong; Yu, Chunshui; Chen, Huafu

2015-05-01

The human brain has been described as a complex network, which integrates information with high efficiency. However, the relationships between the efficiency of human brain functional networks and handedness and brain size remain unclear. Twenty-one left-handed and 32 right-handed healthy subjects underwent a resting-state functional magnetic resonance imaging scan. The whole brain functional networks were constructed by thresholding Pearson correlation matrices of 90 cortical and subcortical regions. Graph theory-based methods were employed to further analyze their topological properties. As expected, all participants demonstrated small-world topology, suggesting a highly efficient topological structure. Furthermore, we found that smaller brains showed higher local efficiency, whereas larger brains showed higher global efficiency, reflecting a suitable efficiency balance between local specialization and global integration of brain functional activity. Compared with right-handers, significant alterations in nodal efficiency were revealed in left-handers, involving the anterior and median cingulate gyrus, middle temporal gyrus, angular gyrus, and amygdala. Our findings indicated that the functional network organization in the human brain was associated with handedness and brain size.

Early-stage evolution of particle size distribution with Johnson's SB function due to Brownian coagulation

International Nuclear Information System (INIS)

Tang Hong; Lin Jianzhong

2013-01-01

The moment method can be used to determine the time evolution of particle size distribution due to Brownian coagulation based on the general dynamic equation (GDE). But the function form of the initial particle size distribution must be determined beforehand for the moment method. If the assumed function type of the initial particle size distribution has an obvious deviation from the true particle population, the evolution of particle size distribution may be different from the real evolution tendency. Thus, a simple and general method is proposed based on the moment method. In this method, the Johnson's S B function is chosen as a general distribution function to fit the initial distributions including the log normal (L-N), Rosin–Rammler (R-R), normal (N-N) and gamma distribution functions, respectively. Meanwhile, using the modified beta function to fit the L-N, R-R, N-N and gamma functions is also conducted as a comparison in order to present the advantage of the Johnson's S B function as the general distribution function. And then, the time evolution of particle size distributions using the Johnson's S B function as the initial distribution can be obtained by several lower order moment equations of the Johnson's S B function in conjunction with the GDE during the Brownian coagulation process. Simulation experiments indicate that fairly reasonable results of the time evolution of particle size distribution can be obtained with this proposed method in the free molecule regime, transition regime and continuum plus near continuum regime, respectively, at the early time stage of evolution. The Johnson's S B function has the ability of describing the early time evolution of different initial particle size distributions. (paper)

Whole brain CT perfusion in acute anterior circulation ischemia: coverage size matters

International Nuclear Information System (INIS)

Emmer, B.J.; Rijkee, M.; Walderveen, M.A.A. van; Niesten, J.M.; Velthuis, B.K.; Wermer, M.J.H.

2014-01-01

Our aim was to compare infarct core volume on whole brain CT perfusion (CTP) with several limited coverage sizes (i.e., 3, 4, 6, and 8 cm), as currently used in routine clinical practice. In total, 40 acute ischemic stroke patients with non-contrast CT (NCCT) and CTP imaging of anterior circulation ischemia were included. Imaging was performed using a 320-multislice CT. Average volumes of infarct core of all simulated partial coverage sizes were calculated. Infarct core volume of each partial brain coverage was compared with infarct core volume of whole brain coverage and expressed using a percentage. To determine the optimal starting position for each simulated CTP coverage, the percentage of infarct coverage was calculated for every possible starting position of the simulated partial coverage in relation to Alberta Stroke Program Early CT Score in Acute Stroke Triage (ASPECTS 1) level. Whole brain CTP coverage further increased the percentage of infarct core volume depicted by 10 % as compared to the 8-cm coverage when the bottom slice was positioned at the ASPECTS 1 level. Optimization of the position of the region of interest (ROI) in 3 cm, 4 cm, and 8 cm improved the percentage of infarct depicted by 4 % for the 8-cm, 7 % for the 4-cm, and 13 % for the 3-cm coverage size. This study shows that whole brain CTP is the optimal coverage for CTP with a substantial improvement in accuracy in quantifying infarct core size. In addition, our results suggest that the optimal position of the ROI in limited coverage depends on the size of the coverage. (orig.)

Whole brain CT perfusion in acute anterior circulation ischemia: coverage size matters

Energy Technology Data Exchange (ETDEWEB)

Emmer, B.J. [Erasmus Medical Centre, Department of Radiology, Postbus 2040, Rotterdam (Netherlands); Rijkee, M.; Walderveen, M.A.A. van [Leiden University Medical Centre, Department of Radiology, Leiden (Netherlands); Niesten, J.M.; Velthuis, B.K. [University Medical Centre Utrecht, Department of Radiology, Utrecht (Netherlands); Wermer, M.J.H. [Leiden University Medical Centre, Department of Neurology, Leiden (Netherlands)

2014-12-15

Our aim was to compare infarct core volume on whole brain CT perfusion (CTP) with several limited coverage sizes (i.e., 3, 4, 6, and 8 cm), as currently used in routine clinical practice. In total, 40 acute ischemic stroke patients with non-contrast CT (NCCT) and CTP imaging of anterior circulation ischemia were included. Imaging was performed using a 320-multislice CT. Average volumes of infarct core of all simulated partial coverage sizes were calculated. Infarct core volume of each partial brain coverage was compared with infarct core volume of whole brain coverage and expressed using a percentage. To determine the optimal starting position for each simulated CTP coverage, the percentage of infarct coverage was calculated for every possible starting position of the simulated partial coverage in relation to Alberta Stroke Program Early CT Score in Acute Stroke Triage (ASPECTS 1) level. Whole brain CTP coverage further increased the percentage of infarct core volume depicted by 10 % as compared to the 8-cm coverage when the bottom slice was positioned at the ASPECTS 1 level. Optimization of the position of the region of interest (ROI) in 3 cm, 4 cm, and 8 cm improved the percentage of infarct depicted by 4 % for the 8-cm, 7 % for the 4-cm, and 13 % for the 3-cm coverage size. This study shows that whole brain CTP is the optimal coverage for CTP with a substantial improvement in accuracy in quantifying infarct core size. In addition, our results suggest that the optimal position of the ROI in limited coverage depends on the size of the coverage. (orig.)

Adaptive evolution of body size subject to indirect effect in trophic cascade system.

Science.gov (United States)

Wang, Xin; Fan, Meng; Hao, Lina

2017-09-01

Trophic cascades represent a classic example of indirect effect and are wide-spread in nature. Their ecological impact are well established, but the evolutionary consequences have received even less theoretical attention. We theoretically and numerically investigate the trait (i.e., body size of consumer) evolution in response to indirect effect in a trophic cascade system. By applying the quantitative trait evolutionary theory and the adaptive dynamic theory, we formulate and explore two different types of eco-evolutionary resource-consumer-predator trophic cascade model. First, an eco-evolutionary model incorporating the rapid evolution is formulated to investigate the effect of rapid evolution of the consumer's body size, and to explore the impact of density-mediate indirect effect on the population dynamics and trait dynamics. Next, by employing the adaptive dynamic theory, a long-term evolutionary model of consumer body size is formulated to evaluate the effect of long-term evolution on the population dynamics and the effect of trait-mediate indirect effect. Those models admit rich dynamics that has not been observed yet in empirical studies. It is found that, both in the trait-mediated and density-mediated system, the body size of consumer in predator-consumer-resource interaction (indirect effect) evolves smaller than that in consumer-resource and predator-consumer interaction (direct effect). Moreover, in the density-mediated system, we found that the evolution of consumer body size contributes to avoiding consumer extinction (i.e., evolutionary rescue). The trait-mediate and density-mediate effects may produce opposite evolutionary response. This study suggests that the trophic cascade indirect effect affects consumer evolution, highlights a more comprehensive mechanistic understanding of the intricate interplay between ecological and evolutionary force. The modeling approaches provide avenue for study on indirect effects from an evolutionary perspective

A basal dromaeosaurid and size evolution preceding avian flight.

Science.gov (United States)

Turner, Alan H; Pol, Diego; Clarke, Julia A; Erickson, Gregory M; Norell, Mark A

2007-09-07

Fossil evidence for changes in dinosaurs near the lineage leading to birds and the origin of flight has been sparse. A dinosaur from Mongolia represents the basal divergence within Dromaeosauridae. The taxon's small body size and phylogenetic position imply that extreme miniaturization was ancestral for Paraves (the clade including Avialae, Troodontidae, and Dromaeosauridae), phylogenetically earlier than where flight evolution is strongly inferred. In contrast to the sustained small body sizes among avialans throughout the Cretaceous Period, the two dinosaurian lineages most closely related to birds, dromaeosaurids and troodontids, underwent four independent events of gigantism, and in some lineages size increased by nearly three orders of magnitude. Thus, change in theropod body size leading to flight's origin was not unidirectional.

Discrete hierarchical organization of social group sizes.

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Zhou, W-X; Sornette, D; Hill, R A; Dunbar, R I M

2005-02-22

The 'social brain hypothesis' for the evolution of large brains in primates has led to evidence for the coevolution of neocortical size and social group sizes, suggesting that there is a cognitive constraint on group size that depends, in some way, on the volume of neural material available for processing and synthesizing information on social relationships. More recently, work on both human and non-human primates has suggested that social groups are often hierarchically structured. We combine data on human grouping patterns in a comprehensive and systematic study. Using fractal analysis, we identify, with high statistical confidence, a discrete hierarchy of group sizes with a preferred scaling ratio close to three: rather than a single or a continuous spectrum of group sizes, humans spontaneously form groups of preferred sizes organized in a geometrical series approximating 3-5, 9-15, 30-45, etc. Such discrete scale invariance could be related to that identified in signatures of herding behaviour in financial markets and might reflect a hierarchical processing of social nearness by human brains.

The evolution of body size and shape in the human career

Science.gov (United States)

Grabowski, Mark; Hatala, Kevin G.; Richmond, Brian G.

2016-01-01

Body size is a fundamental biological property of organisms, and documenting body size variation in hominin evolution is an important goal of palaeoanthropology. Estimating body mass appears deceptively simple but is laden with theoretical and pragmatic assumptions about best predictors and the most appropriate reference samples. Modern human training samples with known masses are arguably the ‘best’ for estimating size in early bipedal hominins such as the australopiths and all members of the genus Homo, but it is not clear if they are the most appropriate priors for reconstructing the size of the earliest putative hominins such as Orrorin and Ardipithecus. The trajectory of body size evolution in the early part of the human career is reviewed here and found to be complex and nonlinear. Australopith body size varies enormously across both space and time. The pre-erectus early Homo fossil record from Africa is poor and dominated by relatively small-bodied individuals, implying that the emergence of the genus Homo is probably not linked to an increase in body size or unprecedented increases in size variation. Body size differences alone cannot explain the observed variation in hominin body shape, especially when examined in the context of small fossil hominins and pygmy modern humans. This article is part of the themed issue ‘Major transitions in human evolution’. PMID:27298459

Measuring size evolution of distant, faint galaxies in the radio regime

Science.gov (United States)

Lindroos, L.; Knudsen, K. K.; Stanley, F.; Muxlow, T. W. B.; Beswick, R. J.; Conway, J.; Radcliffe, J. F.; Wrigley, N.

2018-05-01

We measure the evolution of sizes for star-forming galaxies as seen in 1.4 GHz continuum radio for z = 0-3. The measurements are based on combined VLA+MERLIN data of the Hubble Deep Field, and using a uv-stacking algorithm combined with model fitting to estimate the average sizes of galaxies. A sample of ˜1000 star-forming galaxies is selected from optical and near-infrared catalogues, with stellar masses M⊙ ≈ 1010-1011 M⊙ and photometric redshifts 0-3. The median sizes are parametrized for stellar mass M* = 5 × 1010 M⊙ as R_e = A× {}(H(z)/H(1.5))^{α _z}. We find that the median radio sizes evolve towards larger sizes at later times with αz = -1.1 ± 0.6, and A (the median size at z ≈ 1.5) is found to be 0.26^'' ± 0.07^'' or 2.3±0.6 kpc. The measured radio sizes are typically a factor of 2 smaller than those measure in the optical, and are also smaller than the typical H α sizes in the literature. This indicates that star formation, as traced by the radio continuum, is typically concentrated towards the centre of galaxies, for the sampled redshift range. Furthermore, the discrepancy of measured sizes from different tracers of star formation, indicates the need for models of size evolution to adopt a multiwavelength approach in the measurement of the sizes star-forming regions.

Evolution of students’ friendship networks: Examining the influence of group size

Directory of Open Access Journals (Sweden)

Valentina Sokolovska

2017-01-01

Full Text Available  The main aim of this study was to examine the effect of the network size on formation and evolution of students’ friendship relations. Data was collected from two groups of sociology freshmen: a group from the University of Belgrade, which represents a larger group, and a group from the University of Novi Sad, which represents a smaller group. The data was collected in three periods of one academic year. We analyzed the structural features of students’ networks and constructed a stochastic model of network evolution in order to explore how friendships form and change during one year. The results showed that structural features of the larger and the smaller group differ in each stage of friendship formation. At the beginning of group forming, small world structure was noticeable in the larger group, although full small world structure was not confirmed in both groups. Furthermore, transitivity of triads had effect on the evolution of the larger network, while balance or structural equivalence had effect on the evolution of the smaller network. Results of the structural analysis are in line with findings of the network evolution model and together they provide an insight into how friendship evolves in groups of different sizes.

The art of being small : brain-body size scaling in minute parasitic wasps

NARCIS (Netherlands)

Woude, van der Emma

2017-01-01

Haller’s rule states that small animals have relatively larger brains than large animals. This brain-body size relationship may enable small animals to maintain similar levels of brain performance as large animals. However, it also causes small animals to spend an exceptionally large proportion

Evolution of brain-computer interfaces: going beyond classic motor physiology

Science.gov (United States)

Leuthardt, Eric C.; Schalk, Gerwin; Roland, Jarod; Rouse, Adam; Moran, Daniel W.

2010-01-01

The notion that a computer can decode brain signals to infer the intentions of a human and then enact those intentions directly through a machine is becoming a realistic technical possibility. These types of devices are known as brain-computer interfaces (BCIs). The evolution of these neuroprosthetic technologies could have significant implications for patients with motor disabilities by enhancing their ability to interact and communicate with their environment. The cortical physiology most investigated and used for device control has been brain signals from the primary motor cortex. To date, this classic motor physiology has been an effective substrate for demonstrating the potential efficacy of BCI-based control. However, emerging research now stands to further enhance our understanding of the cortical physiology underpinning human intent and provide further signals for more complex brain-derived control. In this review, the authors report the current status of BCIs and detail the emerging research trends that stand to augment clinical applications in the future. PMID:19569892

Allometry in primates, with emphasis on scaling and the evolution of the brain.

Science.gov (United States)

Gould, S J

1975-01-01

Allometry should be defined broadly as the study of size and its consequences, not narrowly as the application of power functions to the data of growth. Variation in size may be ontogenetic, static or phyletic. Errors of omission and treatment have plagued the study of allometry in primates. Standard texts often treat brain size as an independent measure, ignoring its allometric relation with body size - on this basis, gracile australopithecines have been accorded the mental status of gorillas. Intrinsic allometries of the brain/body are likewise neglected: many authors cite cerebral folding as evidence of man's mental superiority, but folding is a mechanical correlate of brain size itself. Confusion among types of scaling heads errors of treatment in both historical primacy [Dubois' ontogenetic inferences from interspecific curves] and current frequency. The predicted parameters of brain-body plots differ greatly for ontogenetic, intrapopulational, interspecific and phyletic allometries. I then discuss basic trends in bivariate allometry at the ordinal level for internal organ weights, skeletal dimensions, lifespan and fetal weight. In considering the causes of basic bivariate allometries, I examine the reason for differences among types of scaling in brain-body relationships. The interspecific exponent of 0.66 strongly suggests a relationship to body surfaces, but we have no satisfactory explanation for why this should be so. The tripartite ontogenetic plot is a consequence of patterns in neuronal differentiation. We do not know why intraspecific exponents fall between 0.2 and 0.4; several partial explanations have been offered. Multivariate techniques have transcended the pictorial representation of transformed coordinates and offer new, powerful approaches to total allometric patterns. Allometry is most often used as a 'criterion for subtraction'. In order to assess the nature and purpose of an adaptation, we must be able to identify and isolate the aspect of

Sibling rivalry among paralogs promotes evolution of the human brain.

Science.gov (United States)

Tyler-Smith, Chris; Xue, Yali

2012-05-11

Geneticists have long sought to identify the genetic changes that made us human, but pinpointing the functionally relevant changes has been challenging. Two papers in this issue suggest that partial duplication of SRGAP2, producing an incomplete protein that antagonizes the original, contributed to human brain evolution. Copyright © 2012 Elsevier Inc. All rights reserved.

Spectral properties of the temporal evolution of brain network structure.

Science.gov (United States)

Wang, Rong; Zhang, Zhen-Zhen; Ma, Jun; Yang, Yong; Lin, Pan; Wu, Ying

2015-12-01

The temporal evolution properties of the brain network are crucial for complex brain processes. In this paper, we investigate the differences in the dynamic brain network during resting and visual stimulation states in a task-positive subnetwork, task-negative subnetwork, and whole-brain network. The dynamic brain network is first constructed from human functional magnetic resonance imaging data based on the sliding window method, and then the eigenvalues corresponding to the network are calculated. We use eigenvalue analysis to analyze the global properties of eigenvalues and the random matrix theory (RMT) method to measure the local properties. For global properties, the shifting of the eigenvalue distribution and the decrease in the largest eigenvalue are linked to visual stimulation in all networks. For local properties, the short-range correlation in eigenvalues as measured by the nearest neighbor spacing distribution is not always sensitive to visual stimulation. However, the long-range correlation in eigenvalues as evaluated by spectral rigidity and number variance not only predicts the universal behavior of the dynamic brain network but also suggests non-consistent changes in different networks. These results demonstrate that the dynamic brain network is more random for the task-positive subnetwork and whole-brain network under visual stimulation but is more regular for the task-negative subnetwork. Our findings provide deeper insight into the importance of spectral properties in the functional brain network, especially the incomparable role of RMT in revealing the intrinsic properties of complex systems.

Breaking Haller's rule: brain-body size isometry in a minute parasitic wasp.

NARCIS (Netherlands)

Woude, van der E.; Smid, H.M.; Chittka, L.; Huigens, M.E.

2013-01-01

Throughout the animal kingdom, Haller's rule holds that smaller individuals have larger brains relative to their body than larger-bodied individuals. Such brain-body size allometry is documented for all animals studied to date, ranging from small ants to the largest mammals. However, through

Evolution and maintenance of sexual size dimorphism: Aligning phylogenetic and experimental evidence

Directory of Open Access Journals (Sweden)

Matjaz eKuntner

2014-06-01

Full Text Available Integrating the insights derived from both phylogenetic and experimental approaches offers a more complete understanding of evolutionary patterns and processes, yet it is rarely a feature of investigations of the evolutionary significance of trait variation. We combine these approaches to reinterpret the patterns and processes in the evolution of female biased sexual size dimorphism in Nephilidae, a spider lineage characterized by the most extreme sexual size dimorphism among terrestrial animals. We use a molecular phylogeny to reconstruct the size evolution for each sex and reveal a case of sexually dimorphic gigantism: both sexes steadily outgrow their ancestral sizes, but the female and male slopes differ, and hence sexual size dimorphism steadily increases. A review of the experimental evidence reveals a predominant net selection for large size in both sexes, consistent with the phylogenetic pattern for females but not for males. Thus, while sexual size dimorphism in spiders most likely originates and is maintained by fecundity selection on females, it is unclear what selection pressures prevent males from becoming as large as females. This integrated approach highlights the dangers of inferring evolutionary significance from experimental studies that isolate the effects of single selection pressures.

Handedness- and Brain Size-Related Efficiency Differences in Small-World Brain Networks: A Resting-State Functional Magnetic Resonance Imaging Study

OpenAIRE

Li, Meiling; Wang, Junping; Liu, Feng; Chen, Heng; Lu, Fengmei; Wu, Guorong; Yu, Chunshui; Chen, Huafu

2015-01-01

The human brain has been described as a complex network, which integrates information with high efficiency. However, the relationships between the efficiency of human brain functional networks and handedness and brain size remain unclear. Twenty-one left-handed and 32 right-handed healthy subjects underwent a resting-state functional magnetic resonance imaging scan. The whole brain functional networks were constructed by thresholding Pearson correlation matrices of 90 cortical and subcortical...

Staff size evolution at the Spanish nuclear power plants

International Nuclear Information System (INIS)

Ibanez, M.

2001-01-01

This paper describes the main characteristics on the Spanish nuclear electricity sector with an installed capacity of 7580 MW from three different generations, commissioned between 1968 and 1988 and with good plant performance. The analysis of the operation and maintenance cost contributors, made in this paper, shows that the cost of the personnel (own staff plus permanent contractors) amount to around the 80% of the total O and M cost. The paper will describe the evolution of the staff size for all the Spanish NPPs during the last years. In more detail the experience of Garona NPP, a single unit BWR 460 MW(e) commissioned in 1971, and Trillo NPP, a single unit PWR 1066 MW(e) commissioned in 1988, will be presented with the evolution of the following parameters: number of utility employees, number of permanent contractors, O and M costs versus kWh produced. The evolution of the staffing size is correlated with internal organization improvements, managerial policies, regulatory requirements, emergent activities, future projects, etc. The paper will include future reactors considerations that will operate in a competitive environment with other sources of energy and with a high level of safety standards. The strong influence of the personnel in the O and M cost will mean that actions related to reduce or optimize the plant staff will be based on design, organizational and regulatory considerations. (author)

Relative brain size and morphology of some South African bats

African Journals Online (AJOL)

1987-04-03

Apr 3, 1987 ... closely related to basal metabolic rate than ecological factors (Hofman 1983 .... CBS values for the two rhinolophid species, and a single value for the ..... Relative brain size and demographic strategies in didelphid marsupials.

Sexual selection on male size drives the evolution of male-biased sexual size dimorphism via the prolongation of male development.

Science.gov (United States)

Rohner, Patrick T; Blanckenhorn, Wolf U; Puniamoorthy, Nalini

2016-06-01

Sexual size dimorphism (SSD) arises when the net effects of natural and sexual selection on body size differ between the sexes. Quantitative SSD variation between taxa is common, but directional intraspecific SSD reversals are rare. We combined micro- and macroevolutionary approaches to study geographic SSD variation in closely related black scavenger flies. Common garden experiments revealed stark intra- and interspecific variation: Sepsis biflexuosa is monomorphic across the Holarctic, while S. cynipsea (only in Europe) consistently exhibits female-biased SSD. Interestingly, S. neocynipsea displays contrasting SSD in Europe (females larger) and North America (males larger), a pattern opposite to the geographic reversal in SSD of S. punctum documented in a previous study. In accordance with the differential equilibrium model for the evolution of SSD, the intensity of sexual selection on male size varied between continents (weaker in Europe), whereas fecundity selection on female body size did not. Subsequent comparative analyses of 49 taxa documented at least six independent origins of male-biased SSD in Sepsidae, which is likely caused by sexual selection on male size and mediated by bimaturism. Therefore, reversals in SSD and the associated changes in larval development might be much more common and rapid and less constrained than currently assumed. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Evolution, brain, and the nature of language.

Science.gov (United States)

Berwick, Robert C; Friederici, Angela D; Chomsky, Noam; Bolhuis, Johan J

2013-02-01

Language serves as a cornerstone for human cognition, yet much about its evolution remains puzzling. Recent research on this question parallels Darwin's attempt to explain both the unity of all species and their diversity. What has emerged from this research is that the unified nature of human language arises from a shared, species-specific computational ability. This ability has identifiable correlates in the brain and has remained fixed since the origin of language approximately 100 thousand years ago. Although songbirds share with humans a vocal imitation learning ability, with a similar underlying neural organization, language is uniquely human. Copyright © 2012 Elsevier Ltd. All rights reserved.

Size Effect on Acoustic Emission Characteristics of Coal-Rock Damage Evolution

Directory of Open Access Journals (Sweden)

Zhijie Wen

2017-01-01

Full Text Available Coal-gas outburst, rock burst, and other mine dynamic disasters are closely related to the instability and failure of coal-rock. Coal-rock is the assemblies of mineral particles of varying sizes and shapes bonded together by cementing materials. The damage and rupture process of coal-rock is accompanied by acoustic emission (AE, which can be used as an effective means to monitor and predict the instability of coal-rock body. In this manuscript, considering the size effect of coal-rock, the influence of different height to diameter ratio on the acoustic emission characteristics of coal-rock damage evolution was discussed by microparticle flow PFC2D software platform. The results show that coal-rock size influences the uniaxial compressive strength, peak strain, and elastic modulus of itself; the size effect has little effect on the acoustic emission law of coal-rock damage and the effects of the size of coal-rock samples on acoustic emission characteristics are mainly reflected in three aspects: the triggering time of acoustic emission, the strain range of strong acoustic emission, and the intensity of acoustic emission; the damage evolution of coal-rock specimen can be divided into 4 stages: initial damage, stable development, accelerated development, and damage.

Cross-species correlation between queen mating numbers and worker ovary sizes suggests kin conflict may influence ovary size evolution in honeybees

Science.gov (United States)

Rueppell, Olav; Phaincharoen, Mananya; Kuster, Ryan; Tingek, Salim

2011-09-01

During social evolution, the ovary size of reproductively specialized honey bee queens has dramatically increased while their workers have evolved much smaller ovaries. However, worker division of labor and reproductive competition under queenless conditions are influenced by worker ovary size. Little comparative information on ovary size exists in the different honey bee species. Here, we report ovariole numbers of freshly dissected workers from six Apis species from two locations in Southeast Asia. The average number of worker ovarioles differs significantly among species. It is strongly correlated with the average mating number of queens, irrespective of body size. Apis dorsata, in particular, is characterized by numerous matings and very large worker ovaries. The relation between queen mating number and ovary size across the six species suggests that individual selection via reproductive competition plays a role in worker ovary size evolution. This indicates that genetic diversity, generated by multiple mating, may bear a fitness cost at the colony level.

Body size evolution in an old insect order: No evidence for Cope's Rule in spite of fitness benefits of large size.

Science.gov (United States)

Waller, John T; Svensson, Erik I

2017-09-01

We integrate field data and phylogenetic comparative analyses to investigate causes of body size evolution and stasis in an old insect order: odonates ("dragonflies and damselflies"). Fossil evidence for "Cope's Rule" in odonates is weak or nonexistent since the last major extinction event 65 million years ago, yet selection studies show consistent positive selection for increased body size among adults. In particular, we find that large males in natural populations of the banded demoiselle (Calopteryx splendens) over several generations have consistent fitness benefits both in terms of survival and mating success. Additionally, there was no evidence for stabilizing or conflicting selection between fitness components within the adult life-stage. This lack of stabilizing selection during the adult life-stage was independently supported by a literature survey on different male and female fitness components from several odonate species. We did detect several significant body size shifts among extant taxa using comparative methods and a large new molecular phylogeny for odonates. We suggest that the lack of Cope's rule in odonates results from conflicting selection between fitness advantages of large adult size and costs of long larval development. We also discuss competing explanations for body size stasis in this insect group. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

The evolution of vertebrate eye size across an environmental gradient: phenotype does not predict genotype in a Trinidadian killifish.

Science.gov (United States)

Beston, Shannon M; Wostl, Elijah; Walsh, Matthew R

2017-08-01

Vertebrates exhibit substantial variation in eye size. Eye size correlates positively with visual capacity and behaviors that enhance fitness, such as predator avoidance. This foreshadows a connection between predation and eye size evolution. Yet, the conditions that favor evolutionary shifts in eye size, besides the well-known role for light availability, are unclear. We tested the influence of predation on the evolution of eye size in Trinidadian killifish, Rivulus hartii. Rivulus are located across a series of communities where they coexist with visually oriented piscivores ("high predation" sites), and no predators ("Rivulus-only" sites). Wild-caught Rivulus from high predation sites generally exhibited a smaller relative eye size than communities that lack predators. Yet, such differences were inconsistent across rivers. Second-generation common garden reared fish revealed repeatable decreases in eye size in Rivulus from high predation sites. We performed additional experiments that tested the importance of light and resources on eye size evolution. Sites that differ in light or resource availability did not differ in eye size. Our results argue that differences in predator-induced mortality underlie genetically-based shifts in vertebrate eye size. We discuss the drivers of eye size evolution in light of the nonparallel trends between the phenotypic and common garden results. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

The Small Nuclear Genomes of Selaginella Are Associated with a Low Rate of Genome Size Evolution.

Science.gov (United States)

Baniaga, Anthony E; Arrigo, Nils; Barker, Michael S

2016-06-03

The haploid nuclear genome size (1C DNA) of vascular land plants varies over several orders of magnitude. Much of this observed diversity in genome size is due to the proliferation and deletion of transposable elements. To date, all vascular land plant lineages with extremely small nuclear genomes represent recently derived states, having ancestors with much larger genome sizes. The Selaginellaceae represent an ancient lineage with extremely small genomes. It is unclear how small nuclear genomes evolved in Selaginella We compared the rates of nuclear genome size evolution in Selaginella and major vascular plant clades in a comparative phylogenetic framework. For the analyses, we collected 29 new flow cytometry estimates of haploid genome size in Selaginella to augment publicly available data. Selaginella possess some of the smallest known haploid nuclear genome sizes, as well as the lowest rate of genome size evolution observed across all vascular land plants included in our analyses. Additionally, our analyses provide strong support for a history of haploid nuclear genome size stasis in Selaginella Our results indicate that Selaginella, similar to other early diverging lineages of vascular land plants, has relatively low rates of genome size evolution. Further, our analyses highlight that a rapid transition to a small genome size is only one route to an extremely small genome. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Rates and modes of body size evolution in early carnivores and herbivores: a case study from Captorhinidae

Directory of Open Access Journals (Sweden)

Neil Brocklehurst

2016-01-01

Full Text Available Body size is an extremely important characteristic, impacting on a variety of ecological and life-history traits. It is therefore important to understand the factors which may affect its evolution, and diet has attracted much interest in this context. A recent study which examined the evolution of the earliest terrestrial herbivores in the Late Carboniferous and Early Permian concluded that in the four herbivorous clades examined there was a trend towards increased body size, and that this increase was more substantial than that observed in closely related carnivorous clades. However, this hypothesis was not based on quantitative examination, and phylogenetic comparative methods provide a more robust means of testing such hypotheses. Here, the evolution of body size within different dietary regimes is examined in Captorhinidae, the most diverse and longest lived of these earliest high fibre herbivores. Evolutionary models were fit to their phylogeny to test for variation in rate and mode of evolution between the carnivorous and herbivorous members of this clade, and an analysis of rate variation throughout the tree was carried out. Estimates of ancestral body sizes were calculated in order to compare the rates and direction of evolution of lineages with different dietary regimes. Support for the idea that the high fibre herbivores within captorhinids are being drawn to a higher adaptive peak in body size than the carnivorous members of this clade is weak. A shift in rates of body size evolution is identified, but this does not coincide with the evolution of high-fibre herbivory, instead occurring earlier in time and at a more basal node. Herbivorous lineages which show an increase in size are not found to evolve at a faster rate than those which show a decrease; in fact, it is those which experience a size decrease which evolve at higher rates. It is possible the shift in rates of evolution is related to the improved food processing ability of

Adaptive evolution and effective population size in wild house mice

Czech Academy of Sciences Publication Activity Database

Phifer-Rixey, M.; Bonhomme, F.; Boursot, P.; Churchill, G. A.; Piálek, Jaroslav; Tucker, P.; Nachman, M.

2012-01-01

Roč. 29, č. 10 (2012), s. 2949-2955 ISSN 0737-4038 R&D Projects: GA ČR GA206/08/0640 Institutional support: RVO:68081766 Keywords : substitution * adaptation * evolution * effective population size * house mouse Subject RIV: EG - Zoology Impact factor: 10.353, year: 2012

Evolution of genome size and complexity in the rhabdoviridae.

Directory of Open Access Journals (Sweden)

Peter J Walker

2015-02-01

Full Text Available RNA viruses exhibit substantial structural, ecological and genomic diversity. However, genome size in RNA viruses is likely limited by a high mutation rate, resulting in the evolution of various mechanisms to increase complexity while minimising genome expansion. Here we conduct a large-scale analysis of the genome sequences of 99 animal rhabdoviruses, including 45 genomes which we determined de novo, to identify patterns of genome expansion and the evolution of genome complexity. All but seven of the rhabdoviruses clustered into 17 well-supported monophyletic groups, of which eight corresponded to established genera, seven were assigned as new genera, and two were taxonomically ambiguous. We show that the acquisition and loss of new genes appears to have been a central theme of rhabdovirus evolution, and has been associated with the appearance of alternative, overlapping and consecutive ORFs within the major structural protein genes, and the insertion and loss of additional ORFs in each gene junction in a clade-specific manner. Changes in the lengths of gene junctions accounted for as much as 48.5% of the variation in genome size from the smallest to the largest genome, and the frequency with which new ORFs were observed increased in the 3' to 5' direction along the genome. We also identify several new families of accessory genes encoded in these regions, and show that non-canonical expression strategies involving TURBS-like termination-reinitiation, ribosomal frame-shifts and leaky ribosomal scanning appear to be common. We conclude that rhabdoviruses have an unusual capacity for genomic plasticity that may be linked to their discontinuous transcription strategy from the negative-sense single-stranded RNA genome, and propose a model that accounts for the regular occurrence of genome expansion and contraction throughout the evolution of the Rhabdoviridae.

Evolution of genome size and complexity in the rhabdoviridae.

Science.gov (United States)

Walker, Peter J; Firth, Cadhla; Widen, Steven G; Blasdell, Kim R; Guzman, Hilda; Wood, Thomas G; Paradkar, Prasad N; Holmes, Edward C; Tesh, Robert B; Vasilakis, Nikos

2015-02-01

RNA viruses exhibit substantial structural, ecological and genomic diversity. However, genome size in RNA viruses is likely limited by a high mutation rate, resulting in the evolution of various mechanisms to increase complexity while minimising genome expansion. Here we conduct a large-scale analysis of the genome sequences of 99 animal rhabdoviruses, including 45 genomes which we determined de novo, to identify patterns of genome expansion and the evolution of genome complexity. All but seven of the rhabdoviruses clustered into 17 well-supported monophyletic groups, of which eight corresponded to established genera, seven were assigned as new genera, and two were taxonomically ambiguous. We show that the acquisition and loss of new genes appears to have been a central theme of rhabdovirus evolution, and has been associated with the appearance of alternative, overlapping and consecutive ORFs within the major structural protein genes, and the insertion and loss of additional ORFs in each gene junction in a clade-specific manner. Changes in the lengths of gene junctions accounted for as much as 48.5% of the variation in genome size from the smallest to the largest genome, and the frequency with which new ORFs were observed increased in the 3' to 5' direction along the genome. We also identify several new families of accessory genes encoded in these regions, and show that non-canonical expression strategies involving TURBS-like termination-reinitiation, ribosomal frame-shifts and leaky ribosomal scanning appear to be common. We conclude that rhabdoviruses have an unusual capacity for genomic plasticity that may be linked to their discontinuous transcription strategy from the negative-sense single-stranded RNA genome, and propose a model that accounts for the regular occurrence of genome expansion and contraction throughout the evolution of the Rhabdoviridae.

Evolution of Genome Size and Complexity in the Rhabdoviridae

Science.gov (United States)

Walker, Peter J.; Firth, Cadhla; Widen, Steven G.; Blasdell, Kim R.; Guzman, Hilda; Wood, Thomas G.; Paradkar, Prasad N.; Holmes, Edward C.; Tesh, Robert B.; Vasilakis, Nikos

2015-01-01

RNA viruses exhibit substantial structural, ecological and genomic diversity. However, genome size in RNA viruses is likely limited by a high mutation rate, resulting in the evolution of various mechanisms to increase complexity while minimising genome expansion. Here we conduct a large-scale analysis of the genome sequences of 99 animal rhabdoviruses, including 45 genomes which we determined de novo, to identify patterns of genome expansion and the evolution of genome complexity. All but seven of the rhabdoviruses clustered into 17 well-supported monophyletic groups, of which eight corresponded to established genera, seven were assigned as new genera, and two were taxonomically ambiguous. We show that the acquisition and loss of new genes appears to have been a central theme of rhabdovirus evolution, and has been associated with the appearance of alternative, overlapping and consecutive ORFs within the major structural protein genes, and the insertion and loss of additional ORFs in each gene junction in a clade-specific manner. Changes in the lengths of gene junctions accounted for as much as 48.5% of the variation in genome size from the smallest to the largest genome, and the frequency with which new ORFs were observed increased in the 3’ to 5’ direction along the genome. We also identify several new families of accessory genes encoded in these regions, and show that non-canonical expression strategies involving TURBS-like termination-reinitiation, ribosomal frame-shifts and leaky ribosomal scanning appear to be common. We conclude that rhabdoviruses have an unusual capacity for genomic plasticity that may be linked to their discontinuous transcription strategy from the negative-sense single-stranded RNA genome, and propose a model that accounts for the regular occurrence of genome expansion and contraction throughout the evolution of the Rhabdoviridae. PMID:25679389

Scaling of brain metabolism with a fixed energy budget per neuron: implications for neuronal activity, plasticity and evolution.

Science.gov (United States)

Herculano-Houzel, Suzana

2011-03-01

It is usually considered that larger brains have larger neurons, which consume more energy individually, and are therefore accompanied by a larger number of glial cells per neuron. These notions, however, have never been tested. Based on glucose and oxygen metabolic rates in awake animals and their recently determined numbers of neurons, here I show that, contrary to the expected, the estimated glucose use per neuron is remarkably constant, varying only by 40% across the six species of rodents and primates (including humans). The estimated average glucose use per neuron does not correlate with neuronal density in any structure. This suggests that the energy budget of the whole brain per neuron is fixed across species and brain sizes, such that total glucose use by the brain as a whole, by the cerebral cortex and also by the cerebellum alone are linear functions of the number of neurons in the structures across the species (although the average glucose consumption per neuron is at least 10× higher in the cerebral cortex than in the cerebellum). These results indicate that the apparently remarkable use in humans of 20% of the whole body energy budget by a brain that represents only 2% of body mass is explained simply by its large number of neurons. Because synaptic activity is considered the major determinant of metabolic cost, a conserved energy budget per neuron has several profound implications for synaptic homeostasis and the regulation of firing rates, synaptic plasticity, brain imaging, pathologies, and for brain scaling in evolution.

Scaling of brain metabolism with a fixed energy budget per neuron: implications for neuronal activity, plasticity and evolution.

Directory of Open Access Journals (Sweden)

Suzana Herculano-Houzel

Full Text Available It is usually considered that larger brains have larger neurons, which consume more energy individually, and are therefore accompanied by a larger number of glial cells per neuron. These notions, however, have never been tested. Based on glucose and oxygen metabolic rates in awake animals and their recently determined numbers of neurons, here I show that, contrary to the expected, the estimated glucose use per neuron is remarkably constant, varying only by 40% across the six species of rodents and primates (including humans. The estimated average glucose use per neuron does not correlate with neuronal density in any structure. This suggests that the energy budget of the whole brain per neuron is fixed across species and brain sizes, such that total glucose use by the brain as a whole, by the cerebral cortex and also by the cerebellum alone are linear functions of the number of neurons in the structures across the species (although the average glucose consumption per neuron is at least 10× higher in the cerebral cortex than in the cerebellum. These results indicate that the apparently remarkable use in humans of 20% of the whole body energy budget by a brain that represents only 2% of body mass is explained simply by its large number of neurons. Because synaptic activity is considered the major determinant of metabolic cost, a conserved energy budget per neuron has several profound implications for synaptic homeostasis and the regulation of firing rates, synaptic plasticity, brain imaging, pathologies, and for brain scaling in evolution.

Scaling of Brain Metabolism with a Fixed Energy Budget per Neuron: Implications for Neuronal Activity, Plasticity and Evolution

Science.gov (United States)

Herculano-Houzel, Suzana

2011-01-01

It is usually considered that larger brains have larger neurons, which consume more energy individually, and are therefore accompanied by a larger number of glial cells per neuron. These notions, however, have never been tested. Based on glucose and oxygen metabolic rates in awake animals and their recently determined numbers of neurons, here I show that, contrary to the expected, the estimated glucose use per neuron is remarkably constant, varying only by 40% across the six species of rodents and primates (including humans). The estimated average glucose use per neuron does not correlate with neuronal density in any structure. This suggests that the energy budget of the whole brain per neuron is fixed across species and brain sizes, such that total glucose use by the brain as a whole, by the cerebral cortex and also by the cerebellum alone are linear functions of the number of neurons in the structures across the species (although the average glucose consumption per neuron is at least 10× higher in the cerebral cortex than in the cerebellum). These results indicate that the apparently remarkable use in humans of 20% of the whole body energy budget by a brain that represents only 2% of body mass is explained simply by its large number of neurons. Because synaptic activity is considered the major determinant of metabolic cost, a conserved energy budget per neuron has several profound implications for synaptic homeostasis and the regulation of firing rates, synaptic plasticity, brain imaging, pathologies, and for brain scaling in evolution. PMID:21390261

The Dramatic Size and Kinematic Evolution of Massive Early-type Galaxies

Science.gov (United States)

Lapi, A.; Pantoni, L.; Zanisi, L.; Shi, J.; Mancuso, C.; Massardi, M.; Shankar, F.; Bressan, A.; Danese, L.

2018-04-01

We aim to provide a holistic view on the typical size and kinematic evolution of massive early-type galaxies (ETGs) that encompasses their high-z star-forming progenitors, their high-z quiescent counterparts, and their configurations in the local Universe. Our investigation covers the main processes playing a relevant role in the cosmic evolution of ETGs. Specifically, their early fast evolution comprises biased collapse of the low angular momentum gaseous baryons located in the inner regions of the host dark matter halo; cooling, fragmentation, and infall of the gas down to the radius set by the centrifugal barrier; further rapid compaction via clump/gas migration toward the galaxy center, where strong heavily dust-enshrouded star formation takes place and most of the stellar mass is accumulated; and ejection of substantial gas amount from the inner regions by feedback processes, which causes a dramatic puffing-up of the stellar component. In the late slow evolution, passive aging of stellar populations and mass additions by dry merger events occur. We describe these processes relying on prescriptions inspired by basic physical arguments and by numerical simulations to derive new analytical estimates of the relevant sizes, timescales, and kinematic properties for individual galaxies along their evolution. Then we obtain quantitative results as a function of galaxy mass and redshift, and compare them to recent observational constraints on half-light size R e , on the ratio v/σ between rotation velocity and velocity dispersion (for gas and stars) and on the specific angular momentum j ⋆ of the stellar component; we find good consistency with the available multiband data in average values and dispersion, both for local ETGs and for their z ∼ 1–2 star-forming and quiescent progenitors. The outcomes of our analysis can provide hints to gauge sub-grid recipes implemented in simulations, to tune numerical experiments focused on specific processes, and to plan

Socially induced brain development in a facultatively eusocial sweat bee Megalopta genalis (Halictidae)

OpenAIRE

Smith, Adam R.; Seid, Marc A.; Jiménez, Lissette C.; Wcislo, William T.

2010-01-01

Changes in the relative size of brain regions are often dependent on experience and environmental stimulation, which includes an animal's social environment. Some studies suggest that social interactions are cognitively demanding, and have examined predictions that the evolution of sociality led to the evolution of larger brains. Previous studies have compared species with different social organizations or different groups within obligately social species. Here, we report the first intraspeci...

Oxygen no longer plays a major role in Body Size Evolution

Science.gov (United States)

Datta, H.; Sachson, W.; Heim, N. A.; Payne, J.

2015-12-01

When observing the long-term relationship between atmospheric oxygen and the maximum size in organisms across the Geozoic (~3.8 Ga - present), it appears that as oxygen increases, organism size grows. However, during the Phanerozoic (541 Ma - Present) oxygen levels varied, so we set out to test the hypothesis that oxygen levels drive patterns marine animal body size evolution. Expected decreases in maximum size due to a lack of oxygen do not occur, and instead, body size continues to increase regardless. In the oxygen data, a relatively low atmospheric oxygen percentage can support increasing body size, so our research tries to determine whether lifestyle affects body size in marine organisms. The genera in the data set were organized based on their tiering, motility, and feeding, such as a pelagic, fully-motile, predator. When organisms fill a certain ecological niche to take advantage of resources, they will have certain life modes, rather than randomly selected traits. For example, even in terrestrial environments, large animals have to constantly feed themselves to support their expensive terrestrial lifestyle which involves fairly consistent movement, and the structural support necessary for that movement. Only organisms with access to high energy food sources or large amounts of food can support themselves, and that is before they expend energy elsewhere. Organisms that expend energy frugally when active or have slower metabolisms in comparison to body size have a more efficient lifestyle and are generally able to grow larger, while those who have higher energy demands like predators are limited to comparatively smaller sizes. Therefore, in respect to the fossil record and modern measurements of animals, the metabolism and lifestyle of an organism dictate its body size in general. With this further clarification on the patterns of evolution, it will be easier to observe and understand the reasons for the ecological traits of organisms today.

Comments on "Brain Size and Cerebral Glucose Metabolic Rate in Nonspecific Mental Retardation and Down Syndrome."

Science.gov (United States)

Willerman, Lee; Schultz, Robert T.

1995-01-01

The relationship between mental retardation and brain size is discussed. Research suggests that a common path for many otherwise idiopathic mild retardation cases (genetic or environmental) could be small brain size, indicating reduced information processing capacity. Suggestions are made for further research on neuron number. (SLD)

Is the evolution of clutch size limited by incubation ability in shorebirds?

OpenAIRE

Beatty, Jessica Lynne

2015-01-01

Incubation is a crucial aspect of avian life history where differences in incubation techniques and investments can have long lasting effects on offspring and parental well- being and reproductive success. The factors limiting why some birds, such as shorebirds, have fixed clutch sizes has intrigued life history theorist to propose different hypotheses about the evolution of clutch size. Lack's "incubation limitation hypothesis," suggesting that clutch size is limited by the amount of eggs a ...

A simple rule governs the evolution and development of hominin tooth size.

Science.gov (United States)

Evans, Alistair R; Daly, E Susanne; Catlett, Kierstin K; Paul, Kathleen S; King, Stephen J; Skinner, Matthew M; Nesse, Hans P; Hublin, Jean-Jacques; Townsend, Grant C; Schwartz, Gary T; Jernvall, Jukka

2016-02-25

The variation in molar tooth size in humans and our closest relatives (hominins) has strongly influenced our view of human evolution. The reduction in overall size and disproportionate decrease in third molar size have been noted for over a century, and have been attributed to reduced selection for large dentitions owing to changes in diet or the acquisition of cooking. The systematic pattern of size variation along the tooth row has been described as a 'morphogenetic gradient' in mammal, and more specifically hominin, teeth since Butler and Dahlberg. However, the underlying controls of tooth size have not been well understood, with hypotheses ranging from morphogenetic fields to the clone theory. In this study we address the following question: are there rules that govern how hominin tooth size evolves? Here we propose that the inhibitory cascade, an activator-inhibitor mechanism that affects relative tooth size in mammals, produces the default pattern of tooth sizes for all lower primary postcanine teeth (deciduous premolars and permanent molars) in hominins. This configuration is also equivalent to a morphogenetic gradient, finally pointing to a mechanism that can generate this gradient. The pattern of tooth size remains constant with absolute size in australopiths (including Ardipithecus, Australopithecus and Paranthropus). However, in species of Homo, including modern humans, there is a tight link between tooth proportions and absolute size such that a single developmental parameter can explain both the relative and absolute sizes of primary postcanine teeth. On the basis of the relationship of inhibitory cascade patterning with size, we can use the size at one tooth position to predict the sizes of the remaining four primary postcanine teeth in the row for hominins. Our study provides a development-based expectation to examine the evolution of the unique proportions of human teeth.

The effects of laboratory housing and spatial enrichment on brain size and metabolic rate in the eastern mosquitofish, Gambusia holbrooki

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Mischa P. Turschwell

2016-03-01

Full Text Available It has long been hypothesised that there is a functional correlation between brain size and metabolic rate in vertebrates. The present study tested this hypothesis in wild-caught adult mosquitofish Gambusia holbrooki by testing for an intra-specific association between resting metabolic rate (RMR and brain size while controlling for variation in body size, and through the examination of the effects of spatial enrichment and laboratory housing on body mass-independent measures of brain size and RMR. Controlling for body mass, there was no relationship between brain size and RMR in wild-caught fish. Contrary to predictions, spatial enrichment caused a decrease in mass-independent brain size, highlighting phenotypic plasticity in the adult brain. As expected, after controlling for differences in body size, wild-caught fish had relatively larger brains than fish that had been maintained in the laboratory for a minimum of six weeks, but wild-caught fish also had significantly lower mass-independent RMR. This study demonstrates that an organisms' housing environment can cause significant plastic changes to fitness related traits including brain size and RMR. We therefore conclude that current standard laboratory housing conditions may cause captive animals to be non-representative of their wild counterparts, potentially undermining the transferability of previous laboratory-based studies of aquatic ectothermic vertebrates to wild populations.

Brain Size and Cerebral Glucose Metabolic Rate in Nonspecific Retardation and Down Syndrome.

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Haier, Richard J.; And Others

1995-01-01

Brain size and cerebral glucose metabolic rate were determined for 10 individuals with mild mental retardation (MR), 7 individuals with Down syndrome (DS), and 10 matched controls. MR and DS groups both had brain volumes of about 80% compared to controls, with variance greatest within the MR group. (SLD)

Cross-linked structure of network evolution

International Nuclear Information System (INIS)

Bassett, Danielle S.; Wymbs, Nicholas F.; Grafton, Scott T.; Porter, Mason A.; Mucha, Peter J.

2014-01-01

We study the temporal co-variation of network co-evolution via the cross-link structure of networks, for which we take advantage of the formalism of hypergraphs to map cross-link structures back to network nodes. We investigate two sets of temporal network data in detail. In a network of coupled nonlinear oscillators, hyperedges that consist of network edges with temporally co-varying weights uncover the driving co-evolution patterns of edge weight dynamics both within and between oscillator communities. In the human brain, networks that represent temporal changes in brain activity during learning exhibit early co-evolution that then settles down with practice. Subsequent decreases in hyperedge size are consistent with emergence of an autonomous subgraph whose dynamics no longer depends on other parts of the network. Our results on real and synthetic networks give a poignant demonstration of the ability of cross-link structure to uncover unexpected co-evolution attributes in both real and synthetic dynamical systems. This, in turn, illustrates the utility of analyzing cross-links for investigating the structure of temporal networks

Cross-linked structure of network evolution

Energy Technology Data Exchange (ETDEWEB)

Bassett, Danielle S., E-mail: dsb@seas.upenn.edu [Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Department of Physics, University of California, Santa Barbara, California 93106 (United States); Sage Center for the Study of the Mind, University of California, Santa Barbara, California 93106 (United States); Wymbs, Nicholas F.; Grafton, Scott T. [Department of Psychology and UCSB Brain Imaging Center, University of California, Santa Barbara, California 93106 (United States); Porter, Mason A. [Oxford Centre for Industrial and Applied Mathematics, Mathematical Institute, University of Oxford, Oxford OX2 6GG (United Kingdom); CABDyN Complexity Centre, University of Oxford, Oxford, OX1 1HP (United Kingdom); Mucha, Peter J. [Carolina Center for Interdisciplinary Applied Mathematics, Department of Mathematics, University of North Carolina, Chapel Hill, North Carolina 27599 (United States); Department of Applied Physical Sciences, University of North Carolina, Chapel Hill, North Carolina 27599 (United States)

2014-03-15

We study the temporal co-variation of network co-evolution via the cross-link structure of networks, for which we take advantage of the formalism of hypergraphs to map cross-link structures back to network nodes. We investigate two sets of temporal network data in detail. In a network of coupled nonlinear oscillators, hyperedges that consist of network edges with temporally co-varying weights uncover the driving co-evolution patterns of edge weight dynamics both within and between oscillator communities. In the human brain, networks that represent temporal changes in brain activity during learning exhibit early co-evolution that then settles down with practice. Subsequent decreases in hyperedge size are consistent with emergence of an autonomous subgraph whose dynamics no longer depends on other parts of the network. Our results on real and synthetic networks give a poignant demonstration of the ability of cross-link structure to uncover unexpected co-evolution attributes in both real and synthetic dynamical systems. This, in turn, illustrates the utility of analyzing cross-links for investigating the structure of temporal networks.

Social polyandry, parental investment, sexual selection, and evolution of reduced female gamete size.

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Andersson, Malte

2004-01-01

Sexual selection in the form of sperm competition is a major explanation for small size of male gametes. Can sexual selection in polyandrous species with reversed sex roles also lead to reduced female gamete size? Comparative studies show that egg size in birds tends to decrease as a lineage evolves social polyandry. Here, a quantitative genetic model predicts that female scrambles over mates lead to evolution of reduced female gamete size. Increased female mating success drives the evolution of smaller eggs, which take less time to produce, until balanced by lowered offspring survival. Mean egg size is usually reduced and polyandry increased by increasing sex ratio (male bias) and maximum possible number of mates. Polyandry also increases with the asynchrony (variance) in female breeding start. Opportunity for sexual selection increases with the maximum number of mates but decreases with increasing sex ratio. It is well known that parental investment can affect sexual selection. The model suggests that the influence is mutual: owing to a coevolutionary feedback loop, sexual selection in females also shapes initial parental investment by reducing egg size. Feedback between sexual selection and parental investment may be common.

A simple non-invasive method for measuring gross brain size in small live fish with semi-transparent heads

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Joacim Näslund

2014-09-01

Full Text Available This paper describes a non-invasive method for estimating gross brain size in small fish with semi-transparent heads, using system camera equipment. Macro-photographs were taken from above on backlit free-swimming fish undergoing light anaesthesia. From the photographs, the width of the optic tectum was measured. This measure (TeO-measure correlates well with the width of the optic tectum as measured from out-dissected brains in both brown trout fry and zebrafish (Pearson r > 0.90. The TeO-measure also correlates well with overall brain wet weight in brown trout fry (r = 0.90, but less well for zebrafish (r = 0.79. A non-invasive measure makes it possible to quickly assess brain size from a large number of individuals, as well as repeatedly measuring brain size of live individuals allowing calculation of brain growth.

Limited male incubation ability and the evolution of egg size in shorebirds.

Science.gov (United States)

Lislevand, Terje; Thomas, Gavin H

2006-06-22

In bird species where males incubate but are smaller than females, egg size may be constrained by male body size, and hence ability to incubate the eggs. Using data from 71 such shorebird species, we show that egg size decreases as the degree of female-biased sexual size dimorphism increases, after controlling for female body mass. Relative egg size was not related to mean clutch size. However, when controlling for mating system, the relationship between female-biased sexual size dimorphism and relative egg size was only significant in polyandrous species. The relatively small eggs of socially polyandrous shorebirds have previously been explained as an energy-saving strategy associated with the production of multiple clutches. Our findings suggest that egg size evolution is better explained by male incubation limitation in these birds.

Size evolution of ultrafine particles: Differential signatures of normal and episodic events

International Nuclear Information System (INIS)

Joshi, Manish; Khan, Arshad; Anand, S.; Sapra, B.K.

2016-01-01

The effect of fireworks on the aerosol number characteristics of atmosphere was studied for an urban mega city. Measurements were made at 50 m height to assess the local changes around the festival days. Apart from the increase in total number concentration and characteristic accumulation mode, short-term increase of ultrafine particle concentration was noted. Total number concentration varies an order of magnitude during the measurement period in which peak occurs at a frequency of approximately one per day. On integral scale, it seems not possible to distinguish an episodic (e.g. firework bursting induced aerosol emission) and a normal (ambient atmospheric changes) event. However these events could be differentiated on the basis of size evolution analysis around number concentration peaks. The results are discussed relative to past studies and inferences are drawn towards aerosol signatures of firework bursting. The short-term burst in ultrafine particle concentration can pose an inhalation hazard. - Highlights: • Effect of firework emissions on atmospheric aerosol characteristics was studied. • Significant increase in ultrafine particle concentration was observed during firework bursting. • Size distribution evolution analysis of number concentration peaks has been performed. • Differential signatures of normal and episodic event were noted. - Notable increase in ultrafine particle concentration during firework bursting was seen. Normal and episodic event could be differentiated on the basis of size evolution analysis.

Evolution of the sedimentation technique for particle size distribution analysis

International Nuclear Information System (INIS)

Maley, R.

1998-01-01

After an introduction on the significance of particle size measurements, sedimentation methods are described, with emphasis on the evolution of the gravitational approach. The gravitational technique based on mass determination by X-ray adsorption allows fast analysis by automation and easy data handling, in addition to providing the accuracy required by quality control and research applications [it

Rates of ecological divergence and body size evolution are correlated with species diversification in scaly tree ferns

Science.gov (United States)

Ramírez-Barahona, Santiago; Barrera-Redondo, Josué; Eguiarte, Luis E.

2016-01-01

Variation in species richness across regions and between different groups of organisms is a major feature of evolution. Several factors have been proposed to explain these differences, including heterogeneity in the rates of species diversification and the age of clades. It has been frequently assumed that rapid rates of diversification are coupled to high rates of ecological and morphological evolution, leading to a prediction that remains poorly explored for most species: the positive association between ecological niche divergence, morphological evolution and species diversification. We combined a time-calibrated phylogeny with distribution, ecological and body size data for scaly tree ferns (Cyatheaceae) to test whether rates of species diversification are predicted by the rates at which clades have evolved distinct ecological niches and body sizes. We found that rates of species diversification are positively correlated with rates of ecological and morphological evolution, with rapidly diversifying clades also showing rapidly evolving ecological niches and body sizes. Our results show that rapid diversification of scaly tree ferns is associated with the evolution of species with comparable morphologies that diversified into similar, yet distinct, environments. This suggests parallel evolutionary pathways opening in different tropical regions whenever ecological and geographical opportunities arise. Accordingly, rates of ecological niche and body size evolution are relevant to explain the current patterns of species richness in this ‘ancient’ fern lineage across the tropics. PMID:27412279

Rates of ecological divergence and body size evolution are correlated with species diversification in scaly tree ferns.

Science.gov (United States)

Ramírez-Barahona, Santiago; Barrera-Redondo, Josué; Eguiarte, Luis E

2016-07-13

Variation in species richness across regions and between different groups of organisms is a major feature of evolution. Several factors have been proposed to explain these differences, including heterogeneity in the rates of species diversification and the age of clades. It has been frequently assumed that rapid rates of diversification are coupled to high rates of ecological and morphological evolution, leading to a prediction that remains poorly explored for most species: the positive association between ecological niche divergence, morphological evolution and species diversification. We combined a time-calibrated phylogeny with distribution, ecological and body size data for scaly tree ferns (Cyatheaceae) to test whether rates of species diversification are predicted by the rates at which clades have evolved distinct ecological niches and body sizes. We found that rates of species diversification are positively correlated with rates of ecological and morphological evolution, with rapidly diversifying clades also showing rapidly evolving ecological niches and body sizes. Our results show that rapid diversification of scaly tree ferns is associated with the evolution of species with comparable morphologies that diversified into similar, yet distinct, environments. This suggests parallel evolutionary pathways opening in different tropical regions whenever ecological and geographical opportunities arise. Accordingly, rates of ecological niche and body size evolution are relevant to explain the current patterns of species richness in this 'ancient' fern lineage across the tropics. © 2016 The Author(s).

Brain size regulations by cbp haploinsufficiency evaluated by in-vivo MRI based volumetry

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Ateca-Cabarga, Juan C.; Cosa, Alejandro; Pallarés, Vicente; López-Atalaya, José P.; Barco, Ángel; Canals, Santiago; Moratal, David

2015-11-01

The Rubinstein-Taybi Syndrome (RSTS) is a congenital disease that affects brain development causing severe cognitive deficits. In most cases the disease is associated with dominant mutations in the gene encoding the CREB binding protein (CBP). In this work, we present the first quantitative analysis of brain abnormalities in a mouse model of RSTS using magnetic resonance imaging (MRI) and two novel self-developed automated algorithms for image volumetric analysis. Our results quantitatively confirm key syndromic features observed in RSTS patients, such as reductions in brain size (-16.31%, p < 0.05), white matter volume (-16.00%, p < 0.05), and corpus callosum (-12.40%, p < 0.05). Furthermore, they provide new insight into the developmental origin of the disease. By comparing brain tissues in a region by region basis between cbp+/- and cbp+/+ littermates, we found that cbp haploinsufficiency is specifically associated with significant reductions in prosencephalic tissue, such us in the olfactory bulb and neocortex, whereas regions evolved from the embryonic rhombencephalon were spared. Despite the large volume reductions, the proportion between gray-, white-matter and cerebrospinal fluid were conserved, suggesting a role of CBP in brain size regulation. The commonalities with holoprosencephaly and arhinencephaly conditions suggest the inclusion of RSTS in the family of neuronal migration disorders.

Nasonia Parasitic Wasps Escape from Haller's Rule by Diphasic, Partially Isometric Brain-Body Size Scaling and Selective Neuropil Adaptations

NARCIS (Netherlands)

Groothuis, Jitte; Smid, Hans M.

2017-01-01

Haller's rule states that brains scale allometrically with body size in all animals, meaning that relative brain size increases with decreasing body size. This rule applies both on inter- and intraspecific comparisons. Only 1 species, the extremely small parasitic wasp Trichogramma evanescens, is

Colony size evolution and the origin of eusociality in corbiculate bees (Hymenoptera: Apinae.

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Enrique Rodriguez-Serrano

Full Text Available Recently, it has been proposed that the one of the main determinants of complex societies in Hymenoptera is colony size, since the existence of large colonies reduces the direct reproductive success of an average individual, given a decreased chance of being part of the reproductive caste. In this study, we evaluate colony size evolution in corbiculate bees and their relationship with the sociality level shown by these bees. Specifically i the correlation between colony size and level of sociality considering the phylogenetic relationship to evaluate a general evolutionary tendency, and ii the hypothetical ancestral forms of several clades within a phylogeny of corbiculate bees, to address idiosyncratic process occurring at important nodes. We found that the level of social complexity in corbiculate bees is phylogenetically correlated with colony size. Additionally, another process is invoked to propose why colony size evolved concurrently with the level of social complexity. The study of this trait improves the understanding of the evolutionary transition from simple to complex societies, and highlights the importance of explicit probabilistic models to test the evolution of other important characters involved in the origin of eusociality.

A Video Game for Learning Brain Evolution: A Resource or a Strategy?

Science.gov (United States)

Barbosa Gomez, Luisa Fernanda; Bohorquez Sotelo, Maria Cristina; Roja Higuera, Naydu Shirley; Rodriguez Mendoza, Brigitte Julieth

2016-01-01

Learning resources are part of the educational process of students. However, how video games act as learning resources in a population that has not selected the virtual formation as their main methodology? The aim of this study was to identify the influence of a video game in the learning process of brain evolution. For this purpose, the opinions…

Brain response to food cues varying in portion size is associated with individual differences in the portion size effect in children

NARCIS (Netherlands)

Keller, Kathleen L.; English, Laural K.; Fearnbach, S.N.; Lasschuijt, Marlou; Anderson, Kaitlin; Bermudez, Maria; Fisher, Jennifer O.; Rolls, Barbara J.; Wilson, Stephen J.

2018-01-01

Large portions promote intake of energy dense foods (i.e., the portion size effect–PSE), but the neurobiological drivers of this effect are not known. We tested the association between blood oxygen level dependent (BOLD) brain response to food images varied by portion size (PS) and energy density

Rates of molecular evolution in tree ferns are associated with body size, environmental temperature, and biological productivity.

Science.gov (United States)

Barrera-Redondo, Josué; Ramírez-Barahona, Santiago; Eguiarte, Luis E

2018-05-01

Variation in rates of molecular evolution (heterotachy) is a common phenomenon among plants. Although multiple theoretical models have been proposed, fundamental questions remain regarding the combined effects of ecological and morphological traits on rate heterogeneity. Here, we used tree ferns to explore the correlation between rates of molecular evolution in chloroplast DNA sequences and several morphological and environmental factors within a Bayesian framework. We revealed direct and indirect effects of body size, biological productivity, and temperature on substitution rates, where smaller tree ferns living in warmer and less productive environments tend to have faster rates of molecular evolution. In addition, we found that variation in the ratio of nonsynonymous to synonymous substitution rates (dN/dS) in the chloroplast rbcL gene was significantly correlated with ecological and morphological variables. Heterotachy in tree ferns may be influenced by effective population size associated with variation in body size and productivity. Macroevolutionary hypotheses should go beyond explaining heterotachy in terms of mutation rates and instead, should integrate population-level factors to better understand the processes affecting the tempo of evolution at the molecular level. © 2018 The Author(s). Evolution © 2018 The Society for the Study of Evolution.

Why size matters: differences in brain volume account for apparent sex differences in callosal anatomy: the sexual dimorphism of the corpus callosum.

Science.gov (United States)

Luders, Eileen; Toga, Arthur W; Thompson, Paul M

2014-01-01

Numerous studies have demonstrated a sexual dimorphism of the human corpus callosum. However, the question remains if sex differences in brain size, which typically is larger in men than in women, or biological sex per se account for the apparent sex differences in callosal morphology. Comparing callosal dimensions between men and women matched for overall brain size may clarify the true contribution of biological sex, as any observed group difference should indicate pure sex effects. We thus examined callosal morphology in 24 male and 24 female brains carefully matched for overall size. In addition, we selected 24 extremely large male brains and 24 extremely small female brains to explore if observed sex effects might vary depending on the degree to which male and female groups differed in brain size. Using the individual T1-weighted brain images (n=96), we delineated the corpus callosum at midline and applied a well-validated surface-based mesh-modeling approach to compare callosal thickness at 100 equidistant points between groups determined by brain size and sex. The corpus callosum was always thicker in men than in women. However, this callosal sex difference was strongly determined by the cerebral sex difference overall. That is, the larger the discrepancy in brain size between men and women, the more pronounced the sex difference in callosal thickness, with hardly any callosal differences remaining between brain-size matched men and women. Altogether, these findings suggest that individual differences in brain size account for apparent sex differences in the anatomy of the corpus callosum. © 2013.

Differential Temporal Evolution Patterns in Brain Temperature in Different Ischemic Tissues in a Monkey Model of Middle Cerebral Artery Occlusion

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Zhihua Sun

2012-01-01

Full Text Available Brain temperature is elevated in acute ischemic stroke, especially in the ischemic penumbra (IP. We attempted to investigate the dynamic evolution of brain temperature in different ischemic regions in a monkey model of middle cerebral artery occlusion. The brain temperature of different ischemic regions was measured with proton magnetic resonance spectroscopy (1H MRS, and the evolution processes of brain temperature were compared among different ischemic regions. We found that the normal (baseline brain temperature of the monkey brain was 37.16°C. In the artery occlusion stage, the mean brain temperature of ischemic tissue was 1.16°C higher than the baseline; however, this increase was region dependent, with 1.72°C in the IP, 1.08°C in the infarct core, and 0.62°C in the oligemic region. After recanalization, the brain temperature of the infarct core showed a pattern of an initial decrease accompanied by a subsequent increase. However, the brain temperature of the IP and oligemic region showed a monotonously and slowly decreased pattern. Our study suggests that in vivo measurement of brain temperature could help to identify whether ischemic tissue survives.

The evolution of Homo sapiens denisova and Homo sapiens neanderthalensis miRNA targeting genes in the prenatal and postnatal brain.

Science.gov (United States)

Gunbin, Konstantin V; Afonnikov, Dmitry A; Kolchanov, Nikolay A; Derevianko, Anatoly P; Rogaev, Eugeny I

2015-01-01

As the evolution of miRNA genes has been found to be one of the important factors in formation of the modern type of man, we performed a comparative analysis of the evolution of miRNA genes in two archaic hominines, Homo sapiens neanderthalensis and Homo sapiens denisova, and elucidated the expression of their target mRNAs in bain. A comparative analysis of the genomes of primates, including species in the genus Homo, identified a group of miRNA genes having fixed substitutions with important implications for the evolution of Homo sapiens neanderthalensis and Homo sapiens denisova. The mRNAs targeted by miRNAs with mutations specific for Homo sapiens denisova exhibited enhanced expression during postnatal brain development in modern humans. By contrast, the expression of mRNAs targeted by miRNAs bearing variations specific for Homo sapiens neanderthalensis was shown to be enhanced in prenatal brain development. Our results highlight the importance of changes in miRNA gene sequences in the course of Homo sapiens denisova and Homo sapiens neanderthalensis evolution. The genetic alterations of miRNAs regulating the spatiotemporal expression of multiple genes in the prenatal and postnatal brain may contribute to the progressive evolution of brain function, which is consistent with the observations of fine technical and typological properties of tools and decorative items reported from archaeological Denisovan sites. The data also suggest that differential spatial-temporal regulation of gene products promoted by the subspecies-specific mutations in the miRNA genes might have occurred in the brains of Homo sapiens denisova and Homo sapiens neanderthalensis, potentially contributing to the cultural differences between these two archaic hominines.

Coevolving parasites and population size shape the evolution of mating behaviour

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Kerstes Niels AG

2013-02-01

Full Text Available Abstract Background Coevolution with parasites and population size are both expected to influence the evolution of mating rates. To gain insights into the interaction between these dual selective factors, we used populations from a coevolution experiment with the red flour beetle, Tribolium castaneum, and its microsporidian parasite, Nosema whitei. We maintained each experimental population at two different population sizes. We assayed the mating behaviour of both males and females from coevolved and paired non-coevolved control populations after 24 generations of coevolution with parasites. Results Males from large, coevolved populations (i.e. ancestors were exposed to parasites showed a reduced eagerness to mate compared to males from large, non-coevolved populations. But in small populations, coevolution did not lead to decreased male mating rates. Coevolved females from both large and small populations appeared to be more willing to accept mating than non-coevolved females. Conclusions This study provides unique, experimental insights into the combined roles of coevolving parasites and population size on the evolution of mating rate. Furthermore, we find that males and females respond differently to the same environmental conditions. Our results show that parasites can be key determinants of the sexual behaviour of their hosts.

Consolidation of nanometer-sized aluminum single crystals: Microstructure and defects evolutions

KAUST Repository

Afify, N. D.

2014-04-01

Deriving bulk materials with ultra-high mechanical strength from nanometer-sized single metalic crystals depends on the consolidation procedure. We present an accurate molecular dynamics study to quantify microstructure responses to consolidation. Aluminum single crystals with an average size up to 10.7 nm were hydrostatically compressed at temperatures up to 900 K and pressures up to 5 GPa. The consolidated material developed an average grain size that grew exponentially with the consolidation temperature, with a growth rate dependent on the starting average grain size and the consolidation pressure. The evolution of the microstructure was accompanied by a significant reduction in the concentration of defects. The ratio of vacancies to dislocation cores decreased with the average grain size and then increased after reaching a critical average grain size. The deformation mechanisms of poly-crystalline metals can be better understood in the light of the current findings. © 2013 Elsevier B.V. All rights reserved.

Consolidation of nanometer-sized aluminum single crystals: Microstructure and defects evolutions

KAUST Repository

Afify, N. D.; Salem, H. G.; Yavari, A.; El Sayed, Tamer S.

2014-01-01

Deriving bulk materials with ultra-high mechanical strength from nanometer-sized single metalic crystals depends on the consolidation procedure. We present an accurate molecular dynamics study to quantify microstructure responses to consolidation. Aluminum single crystals with an average size up to 10.7 nm were hydrostatically compressed at temperatures up to 900 K and pressures up to 5 GPa. The consolidated material developed an average grain size that grew exponentially with the consolidation temperature, with a growth rate dependent on the starting average grain size and the consolidation pressure. The evolution of the microstructure was accompanied by a significant reduction in the concentration of defects. The ratio of vacancies to dislocation cores decreased with the average grain size and then increased after reaching a critical average grain size. The deformation mechanisms of poly-crystalline metals can be better understood in the light of the current findings. © 2013 Elsevier B.V. All rights reserved.

Curcumin pretreatment attenuates brain lesion size and improves neurological function following traumatic brain injury in the rat.

Science.gov (United States)

Samini, Fariborz; Samarghandian, Saeed; Borji, Abasalt; Mohammadi, Gholamreza; bakaian, Mahdi

2013-09-01

Turmeric has been in use since ancient times as a condiment and due to its medicinal properties. Curcumin, the yellow coloring principle in turmeric, is a polyphenolic and a major active constituent. Besides anti-inflammatory, thrombolytic and anti-carcinogenic activities, curcumin also possesses strong antioxidant property. The neuroprotective effects of curcumin were evaluated in a weight drop model of cortical contusion trauma in rat. Male Wistar rats (350-400 g, n=9) were anesthetized with sodium pentobarbital (60 mg/kg i.p.) and subjected to head injury. Five days before injury, animals randomly received an i.p. bolus of either curcumin (50 and 100 mg/kg/day, n=9) or vehicle (n=9). Two weeks after the injury and drug treatment, animals were sacrificed and a series of brain sections, stained with hematoxylin and eosin (H&E) were evaluated for quantitative brain lesion volume. Two weeks after the injury, oxidative stress parameter (malondialdehyde) was also measured in the brain. Curcumin (100 mg/kg) significantly reduced the size of brain injury-induced lesions (Pcurcumin (100 mg/kg). Curcumin treatment significantly improved the neurological status evaluated during 2 weeks after brain injury. The study demonstrates the protective efficacy of curcumin in rat traumatic brain injury model. © 2013 Elsevier Inc. All rights reserved.

The effect of particle size distributions on the microstructural evolution during sintering

DEFF Research Database (Denmark)

Bjørk, Rasmus; Tikare, V.; Frandsen, Henrik Lund

2013-01-01

Microstructural evolution and sintering behavior of powder compacts composed of spherical particles with different particle size distributions (PSDs) were simulated using a kinetic Monte Carlo model of solid state sintering. Compacts of monosized particles, normal PSDs with fixed mean particle...

MicroCT and microMRI imaging of a prenatal mouse model of increased brain size

Science.gov (United States)

López, Elisabeth K. N.; Stock, Stuart R.; Taketo, Makoto M.; Chenn, Anjen; Ravosa, Matthew J.

2008-08-01

There are surprisingly few experimental models of neural growth and cranial integration. This and the dearth of information regarding fetal brain development detract from a mechanistic understanding of cranial integration and its relevance to the patterning of skull form, specifically the role of encephalization on basicranial flexion. To address this shortcoming, our research uses transgenic mice expressing a stabilized form of β-catenin to isolate the effects of relative brain size on craniofacial development. These mice develop highly enlarged brains due to an increase in neural precursors, and differences between transgenic and wild-type mice are predicted to result solely from variation in brain size. Comparisons of wild-type and transgenic mice at several prenatal ages were performed using microCT (Scanco Medical MicroCT 40) and microMRI (Avance 600 WB MR spectrometer). Statistical analyses show that the larger brain of the transgenic mice is associated with a larger neurocranium and an altered basicranial morphology. However, body size and postcranial ossification do not seem to be affected by the transgene. Comparisons of the rate of postcranial and cranial ossification using microCT also point to an unexpected effect of neural growth on skull development: increased fetal encephalization may result in a compensatory decrease in the level of cranial ossification. Therefore, if other life history factors are held constant, the ontogeny of a metabolically costly structure such as a brain may occur at the expense of other cranial structures. These analyses indicate the benefits of a multifactorial approach to cranial integration using a mouse model.

On The Evolution of Human Jaws and Teeth: A Review

Directory of Open Access Journals (Sweden)

Serhat Yalcin

2011-06-01

Full Text Available The jaws and teeth of Homo sapiens have evolved, from the last common ancestor of chimpanzee and men to their current form. Many factors such as the foods eaten and the processing of foods by fire and tools have effected this evolution course. The evolution of the masticatory complex is related to other anatomical features such as brain size and bipedal posture, and leads to important proceedings like the formation of speech and language. In this review, the evolution of human jaws and teeth and its impact on the general course of human evolution is discussed.

Genome size evolution in Ontario ferns (Polypodiidae): evolutionary correlations with cell size, spore size, and habitat type and an absence of genome downsizing.

Science.gov (United States)

Henry, Thomas A; Bainard, Jillian D; Newmaster, Steven G

2014-10-01

Genome size is known to correlate with a number of traits in angiosperms, but less is known about the phenotypic correlates of genome size in ferns. We explored genome size variation in relation to a suite of morphological and ecological traits in ferns. Thirty-six fern taxa were collected from wild populations in Ontario, Canada. 2C DNA content was measured using flow cytometry. We tested for genome downsizing following polyploidy using a phylogenetic comparative analysis to explore the correlation between 1Cx DNA content and ploidy. There was no compelling evidence for the occurrence of widespread genome downsizing during the evolution of Ontario ferns. The relationship between genome size and 11 morphological and ecological traits was explored using a phylogenetic principal component regression analysis. Genome size was found to be significantly associated with cell size, spore size, spore type, and habitat type. These results are timely as past and recent studies have found conflicting support for the association between ploidy/genome size and spore size in fern polyploid complexes; this study represents the first comparative analysis of the trend across a broad taxonomic group of ferns.

The correlated evolution of antipredator defences and brain size in mammals

OpenAIRE

Stankowich, Theodore; Romero, Ashly N.

2017-01-01

Mammals that possess elaborate antipredator defences such as body armour, spines and quills are usually well protected, intermediate in size, primarily insectivorous and live in simple open environments. The benefits of such defences seem clear and may relax selection on maintaining cognitive abilities that aid in vigilance and predator recognition, and their bearers may accrue extensive production and maintenance costs. Here, in this comparative phylogenetic analysis of measurements of encep...

Socially induced brain development in a facultatively eusocial sweat bee Megalopta genalis (Halictidae).

Science.gov (United States)

Smith, Adam R; Seid, Marc A; Jiménez, Lissette C; Wcislo, William T

2010-07-22

Changes in the relative size of brain regions are often dependent on experience and environmental stimulation, which includes an animal's social environment. Some studies suggest that social interactions are cognitively demanding, and have examined predictions that the evolution of sociality led to the evolution of larger brains. Previous studies have compared species with different social organizations or different groups within obligately social species. Here, we report the first intraspecific study to examine how social experience shapes brain volume using a species with facultatively eusocial or solitary behaviour, the sweat bee Megalopta genalis. Serial histological sections were used to reconstruct and measure the volume of brain areas of bees behaving as social reproductives, social workers, solitary reproductives or 1-day-old bees that are undifferentiated with respect to the social phenotype. Social reproductives showed increased development of the mushroom body (an area of the insect brain associated with sensory integration and learning) relative to social workers and solitary reproductives. The gross neuroanatomy of young bees is developmentally similar to the advanced eusocial species previously studied, despite vast differences in colony size and social organization. Our results suggest that the transition from solitary to social behaviour is associated with modified brain development, and that maintaining dominance, rather than sociality per se, leads to increased mushroom body development, even in the smallest social groups possible (i.e. groups with two bees). Such results suggest that capabilities to navigate the complexities of social life may be a factor shaping brain evolution in some social insects, as for some vertebrates.

How genome size variation is linked with evolution within Chenopodium sensu lato

Czech Academy of Sciences Publication Activity Database

Mandák, Bohumil; Krak, Karol; Vít, Petr; Pavlíková, Zuzana; Lomonosova, M. N.; Habibi, Farzaneh; Lei, Wang; Jellen, E.N.; Douda, Jan

2016-01-01

Roč. 23, DEC 2016 (2016), s. 18-32 ISSN 1433-8319 R&D Projects: GA ČR GA13-02290S Institutional support: RVO:67985939 Keywords : Chenopodium * genome size evolution * flow cytometry Subject RIV: EF - Botanics Impact factor: 3.123, year: 2016

Brain size is correlated with endangerment status in mammals.

Science.gov (United States)

Abelson, Eric S

2016-02-24

Increases in relative encephalization (RE), brain size after controlling for body size, comes at a great metabolic cost and is correlated with a host of cognitive traits, from the ability to count objects to higher rates of innovation. Despite many studies examining the implications and trade-offs accompanying increased RE, the relationship between mammalian extinction risk and RE is unknown. I examine whether mammals with larger levels of RE are more or less likely to be at risk of endangerment than less-encephalized species. I find that extant species with large levels of encephalization are at greater risk of endangerment, with this effect being strongest in species with small body sizes. These results suggest that RE could be a valuable asset in estimating extinction vulnerability. Additionally, these findings suggest that the cost-benefit trade-off of RE is different in large-bodied species when compared with small-bodied species. © 2016 The Author(s).

Reptiles: a new model for brain evo-devo research.

Science.gov (United States)

Nomura, Tadashi; Kawaguchi, Masahumi; Ono, Katsuhiko; Murakami, Yasunori

2013-03-01

Vertebrate brains exhibit vast amounts of anatomical diversity. In particular, the elaborate and complex nervous system of amniotes is correlated with the size of their behavioral repertoire. However, the evolutionary mechanisms underlying species-specific brain morphogenesis remain elusive. In this review we introduce reptiles as a new model organism for understanding brain evolution. These animal groups inherited ancestral traits of brain architectures. We will describe several unique aspects of the reptilian nervous system with a special focus on the telencephalon, and discuss the genetic mechanisms underlying reptile-specific brain morphology. The establishment of experimental evo-devo approaches to studying reptiles will help to shed light on the origin of the amniote brains. Copyright © 2013 Wiley Periodicals, Inc.

Effects of Isometric Brain-Body Size Scaling on the Complexity of Monoaminergic Neurons in a Minute Parasitic Wasp

NARCIS (Netherlands)

Woude, van der Emma; Smid, Hans M.

2017-01-01

Trichogramma evanescens parasitic wasps show large phenotypic plasticity in brain and body size, resulting in a 5-fold difference in brain volume among genetically identical sister wasps. Brain volume scales linearly with body volume in these wasps. This isometric brain scaling forms an exception to

Evolution of bill size in relation to body size in toucans and hornbills (Aves: Piciformes and Bucerotiformes

Directory of Open Access Journals (Sweden)

Austin L. Hughes

2014-06-01

Full Text Available Evidence that the bill of the Toco Toucan, Ramphastos toco Statius Muller, 1776, has a specialized role in heat dissipation suggests a new function for the large and light-weight bill of the toucan family (Piciformes: Ramphastidae. A prediction of this hypothesis is that bill length in toucans will increase with body mass at a rate greater than the isometric expectation. This hypothesis was tested in a phylogenetic context with measurements of skeletal elements in adult males of 21 toucan species. In these species, 64.3% of variance in relative skeletal measurements was accounted for by the contrast between bill and body size. Maxilla length and depth increased with body mass at a greater than isometric rate relative to both body mass and other linear skeletal measures. By contrast, no such trend was seen in a parallel analysis of 24 hornbill species (Bucerotiformes, sometimes considered ecological equivalents of toucans. The unique relationship between bill size and body mass in toucans supports the hypothesis that the evolution of a heat dissipation function has been a persistent theme of bill evolution in toucans.

A universe of dwarfs and giants: genome size and chromosome evolution in the monocot family Melanthiaceae.

Science.gov (United States)

Pellicer, Jaume; Kelly, Laura J; Leitch, Ilia J; Zomlefer, Wendy B; Fay, Michael F

2014-03-01

• Since the occurrence of giant genomes in angiosperms is restricted to just a few lineages, identifying where shifts towards genome obesity have occurred is essential for understanding the evolutionary mechanisms triggering this process. • Genome sizes were assessed using flow cytometry in 79 species and new chromosome numbers were obtained. Phylogenetically based statistical methods were applied to infer ancestral character reconstructions of chromosome numbers and nuclear DNA contents. • Melanthiaceae are the most diverse family in terms of genome size, with C-values ranging more than 230-fold. Our data confirmed that giant genomes are restricted to tribe Parideae, with most extant species in the family characterized by small genomes. Ancestral genome size reconstruction revealed that the most recent common ancestor (MRCA) for the family had a relatively small genome (1C = 5.37 pg). Chromosome losses and polyploidy are recovered as the main evolutionary mechanisms generating chromosome number change. • Genome evolution in Melanthiaceae has been characterized by a trend towards genome size reduction, with just one episode of dramatic DNA accumulation in Parideae. Such extreme contrasting profiles of genome size evolution illustrate the key role of transposable elements and chromosome rearrangements in driving the evolution of plant genomes. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Genome size evolution at the speciation level: the cryptic species complex Brachionus plicatilis (Rotifera).

Science.gov (United States)

Stelzer, Claus-Peter; Riss, Simone; Stadler, Peter

2011-04-07

Studies on genome size variation in animals are rarely done at lower taxonomic levels, e.g., slightly above/below the species level. Yet, such variation might provide important clues on the tempo and mode of genome size evolution. In this study we used the flow-cytometry method to study the evolution of genome size in the rotifer Brachionus plicatilis, a cryptic species complex consisting of at least 14 closely related species. We found an unexpectedly high variation in this species complex, with genome sizes ranging approximately seven-fold (haploid '1C' genome sizes: 0.056-0.416 pg). Most of this variation (67%) could be ascribed to the major clades of the species complex, i.e. clades that are well separated according to most species definitions. However, we also found substantial variation (32%) at lower taxonomic levels--within and among genealogical species--and, interestingly, among species pairs that are not completely reproductively isolated. In one genealogical species, called B. 'Austria', we found greatly enlarged genome sizes that could roughly be approximated as multiples of the genomes of its closest relatives, which suggests that whole-genome duplications have occurred early during separation of this lineage. Overall, genome size was significantly correlated to egg size and body size, even though the latter became non-significant after controlling for phylogenetic non-independence. Our study suggests that substantial genome size variation can build up early during speciation, potentially even among isolated populations. An alternative, but not mutually exclusive interpretation might be that reproductive isolation tends to build up unusually slow in this species complex.

Morpho morphometrics: Shared ancestry and selection drive the evolution of wing size and shape in Morpho butterflies.

Science.gov (United States)

Chazot, Nicolas; Panara, Stephen; Zilbermann, Nicolas; Blandin, Patrick; Le Poul, Yann; Cornette, Raphaël; Elias, Marianne; Debat, Vincent

2016-01-01

Butterfly wings harbor highly diverse phenotypes and are involved in many functions. Wing size and shape result from interactions between adaptive processes, phylogenetic history, and developmental constraints, which are complex to disentangle. Here, we focus on the genus Morpho (Nymphalidae: Satyrinae, 30 species), which presents a high diversity of sizes, shapes, and color patterns. First, we generate a comprehensive molecular phylogeny of these 30 species. Next, using 911 collection specimens, we quantify the variation of wing size and shape across species, to assess the importance of shared ancestry, microhabitat use, and sexual selection in the evolution of the wings. While accounting for phylogenetic and allometric effects, we detect a significant difference in wing shape but not size among microhabitats. Fore and hindwings covary at the individual and species levels, and the covariation differs among microhabitats. However, the microhabitat structure in covariation disappears when phylogenetic relationships are taken into account. Our results demonstrate that microhabitat has driven wing shape evolution, although it has not strongly affected forewing and hindwing integration. We also found that sexual dimorphism of forewing shape and color pattern are coupled, suggesting a common selective force. © 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.

MICRO, SMALL AND MEDIUM-SIZED BUSINESSES IN JALISCO: THEIR EVOLUTION, AND STRATEGIC CHALLENGES

OpenAIRE

Carlos Fong Reynoso; Moisés Alejandro Alarcón Osuna; Luis Ernesto Ocampo Figueroa

2014-01-01

The business structure in Jalisco, Mexico is primarily composed of micro, small and medium-sized enterprises (SMEs). Thus, it is fundamentally necessary to understand the dynamics, evolution and above all, the strategic challenges of this sector in order to understand the state’s economic performance and the possibilities for future development in Jalisco. As a result, this study analyzes the evolution of the SMEs (known as PyME, in Spanish) in Mexico and Jalisco by using data from the Econom...

Mammal body size evolution in North America and Europe over 20 Myr: similar trends generated by different processes.

Science.gov (United States)

Huang, Shan; Eronen, Jussi T; Janis, Christine M; Saarinen, Juha J; Silvestro, Daniele; Fritz, Susanne A

2017-02-22

Because body size interacts with many fundamental biological properties of a species, body size evolution can be an essential component of the generation and maintenance of biodiversity. Here we investigate how body size evolution can be linked to the clade-specific diversification dynamics in different geographical regions. We analyse an extensive body size dataset of Neogene large herbivores (covering approx. 50% of the 970 species in the orders Artiodactyla and Perissodactyla) in Europe and North America in a Bayesian framework. We reconstruct the temporal patterns of body size in each order on each continent independently, and find significant increases of minimum size in three of the continental assemblages (except European perissodactyls), suggesting an active selection for larger bodies. Assessment of trait-correlated birth-death models indicates that the common trend of body size increase is generated by different processes in different clades and regions. Larger-bodied artiodactyl species on both continents tend to have higher origination rates, and both clades in North America show strong links between large bodies and low extinction rate. Collectively, our results suggest a strong role of species selection and perhaps of higher-taxon sorting in driving body size evolution, and highlight the value of investigating evolutionary processes in a biogeographic context. © 2017 The Author(s).

Deformation mechanisms and grain size evolution in the Bohemian granulites - a computational study

Science.gov (United States)

Maierova, Petra; Lexa, Ondrej; Jeřábek, Petr; Franěk, Jan; Schulmann, Karel

2015-04-01

A dominant deformation mechanism in crustal rocks (e.g., dislocation and diffusion creep, grain boundary sliding, solution-precipitation) depends on many parameters such as temperature, major minerals, differential stress, strain rate and grain size. An exemplary sequence of deformation mechanisms was identified in the largest felsic granulite massifs in the southern Moldanubian domain (Bohemian Massif, central European Variscides). These massifs were interpreted to result from collision-related forced diapiric ascent of lower crust and its subsequent lateral spreading at mid-crustal levels. Three types of microstructures were distinguished. The oldest relict microstructure (S1) with large grains (>1000 μm) of feldspar deformed probably by dislocation creep at peak HT eclogite facies conditions. Subsequently at HP granulite-facies conditions, chemically- and deformation- induced recrystallization of feldspar porphyroclasts led to development of a fine-grained microstructure (S2, ~50 μm grain size) indicating deformation via diffusion creep, probably assisted by melt-enhanced grain-boundary sliding. This microstructure was associated with flow in the lower crust and/or its diapiric ascent. The latest microstructure (S3, ~100 μm grain size) is related to the final lateral spreading of retrograde granulites, and shows deformation by dislocation creep at amphibolite-facies conditions. The S2-S3 switch and coarsening was interpreted to be related with a significant decrease in strain rate. From this microstructural sequence it appears that it is the grain size that is critically linked with specific mechanical behavior of these rocks. Thus in this study, we focused on the interplay between grain size and deformation with the aim to numerically simulate and reinterpret the observed microstructural sequence. We tested several different mathematical descriptions of the grain size evolution, each of which gave qualitatively different results. We selected the two most

Can foraging ecology drive the evolution of body size in a diving endotherm?

Directory of Open Access Journals (Sweden)

Timothée R Cook

Full Text Available Within a single animal species, different morphs can allow for differential exploitation of foraging niches between populations, while sexual size dimorphism can provide each sex with access to different resources. Despite being potentially important agents of evolution, resource polymorphisms, and the way they operate in wild populations, remain poorly understood. In this study, we examine how trophic factors can select for different body sizes between populations and sexes in a diving endotherm. Dive depth and duration are positively related to body size in diving birds and mammals, a relationship explained by a lower mass-specific metabolic rate and greater oxygen stores in larger individuals. Based on this allometry, we predict that selection for exploiting resources situated at different depths can drive the evolution of body size in species of diving endotherms at the population and sexual level. To test this prediction, we studied the foraging ecology of Blue-eyed Shags, a group of cormorants with male-biased sexual size dimorphism from across the Southern Ocean. We found that mean body mass and relative difference in body mass between sexes varied by up to 77% and 107% between neighbouring colonies, respectively. Birds from colonies with larger individuals dived deeper than birds from colonies with smaller individuals, when accounting for sex. In parallel, males dived further offshore and deeper than females and the sexual difference in dive depth reflected the level of sexual size dimorphism at each colony. We argue that body size in this group of birds is under intense selection for diving to depths of profitable benthic prey patches and that, locally, sexual niche divergence selection can exaggerate the sexual size dimorphism of Blue-eyed Shags initially set up by sexual selection. Our findings suggest that trophic resources can select for important geographic micro-variability in body size between populations and sexes.

Neuronal tracing of oral nerves in a velvet worm – Implications for the evolution of the ecdysozoan brain

Directory of Open Access Journals (Sweden)

Christine eMartin

2014-02-01

Full Text Available As one of the closest relatives of arthropods, Onychophora plays an important role in understanding the evolution of arthropod body plans. Currently there is controversy surrounding the evolution of the brain among the ecdysozoan clades, which shows a collar-shaped, circumoral organisation in cycloneuralians but a ganglionic architecture in panarthropods. Based on the innervation pattern of lip papillae surrounding the mouth, the onychophoran brain has been interpreted as a circumoral ring, suggesting that this organisation is an ancestral feature of Ecdysozoa. However, this interpretation is inconsistent with other published data. To explore the evolutionary origin of the onychophoran mouth and to shed light on the evolution of the ecdysozoan brains, we analysed the innervation pattern and morphogenesis of the oral lip papillae in the onychophoran Euperipatoides rowelli using DNA labelling, immunocytochemistry and neuronal tracing techniques. Our morphogenetic data revealed that the seven paired and one unpaired oral lip papillae arise from three anterior-most body segments. Retrograde fills show that only the first and the third nerves supplying the lip papillae are associated with cell bodies within the brain, whereas the second nerve exclusively receives fibres from somata of peripheral neurons located in the lip papillae. According to our anterograde fills and immunocytochemical data, the first nerve supplies the anterior-most pair of lip papillae, whereas the second and the third nerves are associated with the second to fifth and second to eighth lip papillae, respectively. These data suggest that the lip papillae of E. rowelli are mainly innervated by the proto- and deutocerebrum, whereas there are only a few additional cell bodies situated posterior to the brain. According to these findings, the overall innervation pattern of the oral lip papillae in E. rowelli is incompatible with the interpretation of the onychophoran brain as a

ALFY-Controlled DVL3 Autophagy Regulates Wnt Signaling, Determining Human Brain Size.

Directory of Open Access Journals (Sweden)

Rotem Kadir

2016-03-01

Full Text Available Primary microcephaly is a congenital neurodevelopmental disorder of reduced head circumference and brain volume, with fewer neurons in the cortex of the developing brain due to premature transition between symmetrical and asymmetrical cellular division of the neuronal stem cell layer during neurogenesis. We now show through linkage analysis and whole exome sequencing, that a dominant mutation in ALFY, encoding an autophagy scaffold protein, causes human primary microcephaly. We demonstrate the dominant effect of the mutation in drosophila: transgenic flies harboring the human mutant allele display small brain volume, recapitulating the disease phenotype. Moreover, eye-specific expression of human mutant ALFY causes rough eye phenotype. In molecular terms, we demonstrate that normally ALFY attenuates the canonical Wnt signaling pathway via autophagy-dependent removal specifically of aggregates of DVL3 and not of Dvl1 or Dvl2. Thus, autophagic attenuation of Wnt signaling through removal of Dvl3 aggregates by ALFY acts in determining human brain size.

Genome size evolution at the speciation level: The cryptic species complex Brachionus plicatilis (Rotifera

Directory of Open Access Journals (Sweden)

Riss Simone

2011-04-01

Full Text Available Abstract Background Studies on genome size variation in animals are rarely done at lower taxonomic levels, e.g., slightly above/below the species level. Yet, such variation might provide important clues on the tempo and mode of genome size evolution. In this study we used the flow-cytometry method to study the evolution of genome size in the rotifer Brachionus plicatilis, a cryptic species complex consisting of at least 14 closely related species. Results We found an unexpectedly high variation in this species complex, with genome sizes ranging approximately seven-fold (haploid '1C' genome sizes: 0.056-0.416 pg. Most of this variation (67% could be ascribed to the major clades of the species complex, i.e. clades that are well separated according to most species definitions. However, we also found substantial variation (32% at lower taxonomic levels - within and among genealogical species - and, interestingly, among species pairs that are not completely reproductively isolated. In one genealogical species, called B. 'Austria', we found greatly enlarged genome sizes that could roughly be approximated as multiples of the genomes of its closest relatives, which suggests that whole-genome duplications have occurred early during separation of this lineage. Overall, genome size was significantly correlated to egg size and body size, even though the latter became non-significant after controlling for phylogenetic non-independence. Conclusions Our study suggests that substantial genome size variation can build up early during speciation, potentially even among isolated populations. An alternative, but not mutually exclusive interpretation might be that reproductive isolation tends to build up unusually slow in this species complex.

Spinal cord evolution in early Homo.

Science.gov (United States)

Meyer, Marc R; Haeusler, Martin

2015-11-01

The discovery at Nariokotome of the Homo erectus skeleton KNM-WT 15000, with a narrow spinal canal, seemed to show that this relatively large-brained hominin retained the primitive spinal cord size of African apes and that brain size expansion preceded postcranial neurological evolution. Here we compare the size and shape of the KNM-WT 15000 spinal canal with modern and fossil taxa including H. erectus from Dmanisi, Homo antecessor, the European middle Pleistocene hominins from Sima de los Huesos, and Pan troglodytes. In terms of shape and absolute and relative size of the spinal canal, we find all of the Dmanisi and most of the vertebrae of KNM-WT 15000 are within the human range of variation except for the C7, T2, and T3 of KNM-WT 15000, which are constricted, suggesting spinal stenosis. While additional fossils might definitively indicate whether H. erectus had evolved a human-like enlarged spinal canal, the evidence from the Dmanisi spinal canal and the unaffected levels of KNM-WT 15000 show that unlike Australopithecus, H. erectus had a spinal canal size and shape equivalent to that of modern humans. Subadult status is unlikely to affect our results, as spinal canal growth is complete in both individuals. We contest the notion that vertebrae yield information about respiratory control or language evolution, but suggest that, like H. antecessor and European middle Pleistocene hominins from Sima de los Huesos, early Homo possessed a postcranial neurological endowment roughly commensurate to modern humans, with implications for neurological, structural, and vascular improvements over Pan and Australopithecus. Copyright © 2015 Elsevier Ltd. All rights reserved.

Size evolution in Goodwin’s small-eared shrew, Cryptotis goodwini

Science.gov (United States)

Woodman, N.; Merritt, J.F.; Churchfield, S.; Hutterer, R.; Sheftel, B.A.

2005-01-01

Fossils of Cryptotis goodwini from Honduras indicate that body sizes of modern individuals average at least 18% larger than among members of the late Pleistocene population of this species. Palynological and other paleoenvironmental studies provide evidence that the Neotropical montane environments that these shrews inhabit were cooler and drier in the late Pleistocene than at present and supported communities of plants without modern analog. Therefore, the most likely cause of this change in size ultimately was related to climatic change at the end of the Pleistocene?but to what specific factors did the species respond? I examined the possibilities that this species changed in size: to accommodate a change in temperature regime; to escape from predators; as a response to a change in intensity of interspecific competition; to take advantage of a newly abundant food resource. Based on evidence from studies of modern communities of shrews and niche partitioning, I hypothesized that size evolution in C. goodwini was directly related to changes in the community of soil and soil-surface invertebrates upon which the species depends, specifically an increase in the availability of earthworms (Annelida).

Male and female brain evolution is subject to contrasting selection pressures in primates

Directory of Open Access Journals (Sweden)

Dunbar Robin IM

2007-05-01

Full Text Available Abstract The claim that differences in brain size across primate species has mainly been driven by the demands of sociality (the "social brain" hypothesis is now widely accepted. Some of the evidence to support this comes from the fact that species that live in large social groups have larger brains, and in particular larger neocortices. Lindenfors and colleagues (BMC Biology 5:20 add significantly to our appreciation of this process by showing that there are striking differences between the two sexes in the social mechanisms and brain units involved. Female sociality (which is more affiliative is related most closely to neocortex volume, but male sociality (which is more competitive and combative is more closely related to subcortical units (notably those associated with emotional responses. Thus different brain units have responded to different selection pressures.

Mammalian life histories: their evolution and molecular-genetic mechanisms

Energy Technology Data Exchange (ETDEWEB)

Sacher, G.A.

1978-01-01

Survival curves for various species of mammals are discussed and a table is presented to show recorded maximum life spans of about 30 species of mammals. The range of longevities is from one year for shrews and moles up to more than 80 years for the fin whale. The constitutional correlates of longevity are discussed with regard to body size, brain weight,metabolic rates, and body temperature. It is concluded that longevity evolved as a positive trait, associated with the evolution of large body size and brain size. Life table data for man, the thorough-bred horse, beagle dogs, and the laboratory rodents, Mus musculus and Peromyscus leucopus are discussed. The data show a pattern of exponential increase of death rate with age. A laboratory model using Mus musculus and Peromyscus leucopus for the study of the longevity-assurance mechanisms is described. (HLW)

Aging, Brain Size, and IQ.

Science.gov (United States)

Bigler, Erin D.; And Others

1995-01-01

Whether cross-sectional rates of decline for brain volume and the Performance Intellectual Quotient of the Wechsler Adult Intelligence Scale-Revised were equivalent over the years 16 to 65 was studied with 196 volunteers. Results indicate remarkably similar rates of decline in perceptual-motor functions and aging brain volume loss. (SLD)

Pharmacologic modulation of cerebral metabolic derangement and excitotoxicity in a porcine model of traumatic brain injury and hemorrhagic shock

DEFF Research Database (Denmark)

Hwabejire, John O; Jin, Guang; Imam, Ayesha M

2013-01-01

Cerebral metabolic derangement and excitotoxicity play critical roles in the evolution of traumatic brain injury (TBI). We have shown previously that treatment with large doses of valproic acid (VPA) decreases the size of brain lesion. The goal of this experiment was to determine whether...

Finite size effects and symmetry breaking in the evolution of networks of competing Boolean nodes

International Nuclear Information System (INIS)

Liu, M; Bassler, K E

2011-01-01

Finite size effects on the evolutionary dynamics of Boolean networks are analyzed. In the model considered, Boolean networks evolve via a competition between nodes that punishes those in the majority. Previous studies have found that large networks evolve to a statistical steady state that is both critical and highly canalized, and that the evolution of canalization, which is a form of robustness found in genetic regulatory networks, is associated with a particular symmetry of the evolutionary dynamics. Here, it is found that finite size networks evolve in a fundamentally different way than infinitely large networks do. The symmetry of the evolutionary dynamics of infinitely large networks that selects for canalizing Boolean functions is broken in the evolutionary dynamics of finite size networks. In finite size networks, there is an additional selection for input-inverting Boolean functions that output a value opposite to the majority of input values. The reason for the symmetry breaking in the evolutionary dynamics is found to be due to the need for nodes in finite size networks to behave differently in order to cooperate so that the system collectively performs as efficiently as possible. The results suggest that both finite size effects and symmetry are fundamental for understanding the evolution of real-world complex networks, including genetic regulatory networks.

Rutile TiO₂ particles exert size and surface coating dependent retention and lesions on the murine brain.

Science.gov (United States)

Zhang, Lili; Bai, Ru; Li, Bai; Ge, Cuicui; Du, Jiangfeng; Liu, Ying; Le Guyader, Laurent; Zhao, Yuliang; Wu, Yanchuan; He, Shida; Ma, Yongmei; Chen, Chunying

2011-11-10

The rising commercial use and large-scale production of engineered nanoparticles (NPs) may lead to unintended exposure to humans. The central nervous system (CNS) is a potential susceptible target of the inhaled NPs, but so far the amount of studies on this aspect is limited. Here, we focus on the potential neurological lesion in the brain induced by the intranasally instilled titanium dioxide (TiO₂) particles in rutile phase and of various sizes and surface coatings. Female mice were intranasally instilled with four different types of TiO₂ particles (i.e. two types of hydrophobic particles in micro- and nano-sized without coating and two types of water-soluble hydrophilic nano-sized particles with silica surface coating) every other day for 30 days. Inductively coupled plasma mass spectrometry (ICP-MS) were used to determine the titanium contents in the sub-brain regions. Then, the pathological examination of brain tissues and measurements of the monoamine neurotransmitter levels in the sub-brain regions were performed. We found significant up-regulation of Ti contents in the cerebral cortex and striatum after intranasal instillation of hydrophilic TiO₂ NPs. Moreover, TiO₂ NPs exposure, in particular the hydrophilic NPs, caused obvious morphological changes of neurons in the cerebral cortex and significant disturbance of the monoamine neurotransmitter levels in the sub-brain regions studied. Thus, our results indicate that the surface modification of the NPs plays an important role on their effects on the brain. In addition, the difference in neurotoxicity of the two types of hydrophilic NPs may be induced by the shape differences of the materials. The present results suggest that physicochemical properties like size, shape and surface modification of the nanomaterials should be considered when evaluating their neurological effects. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Body size and premolar evolution in the early-middle eocene euprimates of Wyoming.

Science.gov (United States)

Jones, Katrina E; Rose, Kenneth D; Perry, Jonathan M G

2014-01-01

The earliest euprimates to arrive in North America were larger-bodied notharctids and smaller-bodied omomyids. Through the Eocene, notharctids generally continued to increase in body size, whereas omomyids generally radiated within small- and increasingly mid-sized niches in the middle Eocene. This study examines the influence of changing body size and diet on the evolution of the lower fourth premolar in Eocene euprimates. The P4 displays considerable morphological variability in these taxa. Despite the fact that most studies of primate dental morphology have focused on the molars, P4 can also provide important paleoecological insights. We analyzed the P4 from 177 euprimate specimens, representing 35 species (11 notharctids and 24 omomyids), in three time bins of approximately equal duration: early Wasatchian, late Wasatchian, and Bridgerian. Two-dimensional surface landmarks were collected from lingual photographs, capturing important variation in cusp position and tooth shape. Disparity metrics were calculated and compared for the three time bins. In the early Eocene, notharctids have a more molarized P4 than omomyids. During the Bridgerian, expanding body size range of omomyids was accompanied by a significant increase in P4 disparity and convergent evolution of the semimolariform condition in the largest omomyines. P4 morphology relates to diet in early euprimates, although patterns vary between families. Copyright © 2013 Wiley Periodicals, Inc.

Genome Size Diversity and Its Impact on the Evolution of Land Plants

Directory of Open Access Journals (Sweden)

Jaume Pellicer

2018-02-01

Full Text Available Genome size is a biodiversity trait that shows staggering diversity across eukaryotes, varying over 64,000-fold. Of all major taxonomic groups, land plants stand out due to their staggering genome size diversity, ranging ca. 2400-fold. As our understanding of the implications and significance of this remarkable genome size diversity in land plants grows, it is becoming increasingly evident that this trait plays not only an important role in shaping the evolution of plant genomes, but also in influencing plant community assemblages at the ecosystem level. Recent advances and improvements in novel sequencing technologies, as well as analytical tools, make it possible to gain critical insights into the genomic and epigenetic mechanisms underpinning genome size changes. In this review we provide an overview of our current understanding of genome size diversity across the different land plant groups, its implications on the biology of the genome and what future directions need to be addressed to fill key knowledge gaps.

Effect of Growing Size of Interaction Neighbors on the Evolution of Cooperation in Spatial Snowdrift Game

International Nuclear Information System (INIS)

Zhang Juanjuan; Sun Shiwen; Wang Li; Xia Chengyi; Wang Juan; Wang Zhen

2012-01-01

In this paper, we study the influence of the size of interaction neighbors (k) on the evolution of cooperation in the spatial snowdrift game. At first, we consider the effects of noise K and cost-to-benefit ratio r, the simulation results indicate that the evolution of cooperation depends on the combined action of noise and cost-to-benefit ratio. For a lower r, the cooperators are multitudinous and the cooperation frequency ultimately increases to 1 as the increase of noise. However, for a higher r, the defectors account for the majority of the game and dominate the game if the noise is large enough. Then we mainly investigate how k influences the evolution of cooperation by varying the noise in detail. We find that the frequency of cooperators is closely related to the size of neighborhood and cost-to-benefit ratio r. In the case of lower r, the augmentation of k plays no positive role in promoting the cooperation as compared with that of k = 4, while for higher r the cooperation is improved for a growing size of neighborhood. At last, based on the above discussions, we explore the cluster-forming mechanism among the cooperators. The current results are beneficial to further understand the evolution of cooperation in many natural, social and biological systems. (general)

Superresolution Imaging of Aquaporin-4 Cluster Size in Antibody-Stained Paraffin Brain Sections.

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Smith, Alex J; Verkman, Alan S

2015-12-15

The water channel aquaporin-4 (AQP4) forms supramolecular clusters whose size is determined by the ratio of M1- and M23-AQP4 isoforms. In cultured astrocytes, differences in the subcellular localization and macromolecular interactions of small and large AQP4 clusters results in distinct physiological roles for M1- and M23-AQP4. Here, we developed quantitative superresolution optical imaging methodology to measure AQP4 cluster size in antibody-stained paraffin sections of mouse cerebral cortex and spinal cord, human postmortem brain, and glioma biopsy specimens. This methodology was used to demonstrate that large AQP4 clusters are formed in AQP4(-/-) astrocytes transfected with only M23-AQP4, but not in those expressing only M1-AQP4, both in vitro and in vivo. Native AQP4 in mouse cortex, where both isoforms are expressed, was enriched in astrocyte foot-processes adjacent to microcapillaries; clusters in perivascular regions of the cortex were larger than in parenchymal regions, demonstrating size-dependent subcellular segregation of AQP4 clusters. Two-color superresolution imaging demonstrated colocalization of Kir4.1 with AQP4 clusters in perivascular areas but not in parenchyma. Surprisingly, the subcellular distribution of AQP4 clusters was different between gray and white matter astrocytes in spinal cord, demonstrating regional specificity in cluster polarization. Changes in AQP4 subcellular distribution are associated with several neurological diseases and we demonstrate that AQP4 clustering was preserved in a postmortem human cortical brain tissue specimen, but that AQP4 was not substantially clustered in a human glioblastoma specimen despite high-level expression. Our results demonstrate the utility of superresolution optical imaging for measuring the size of AQP4 supramolecular clusters in paraffin sections of brain tissue and support AQP4 cluster size as a primary determinant of its subcellular distribution. Copyright © 2015 Biophysical Society

Mammalian collection on Noah's Ark: the effects of beauty, brain and body size.

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Daniel Frynta

Full Text Available The importance of today's zoological gardens as the so-called "Noah's Ark" grows as the natural habitat of many species quickly diminishes. Their potential to shelter a large amount of individuals from many species gives us the opportunity to reintroduce a species that disappeared in nature. However, the selection of animals to be kept in zoos worldwide is highly selective and depends on human decisions driven by both ecological criteria such as population size or vulnerability and audience-driven criteria such as aesthetic preferences. Thus we focused our study on the most commonly kept and bred animal class, the mammals, and we asked which factors affect various aspects of the mammalian collection of zoos. We analyzed the presence/absence, population size, and frequency per species of each of the 123 mammalian families kept in the worldwide zoo collection. Our aim was to explain these data using the human-perceived attractiveness of mammalian families, their body weight, relative brain size and species richness of the family. In agreement with various previous studies, we found that the body size and the attractiveness of mammals significantly affect all studied components of the mammalian collection of zoos. There is a higher probability of the large and attractive families to be kept. Once kept, these animals are presented in larger numbers in more zoos. On the contrary, the relative mean brain size only affects the primary selection whether to keep the family or not. It does not affect the zoo population size or the number of zoos that keep the family.

Triadic (ecological, neural, cognitive) niche construction: a scenario of human brain evolution extrapolating tool use and language from the control of reaching actions.

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Iriki, Atsushi; Taoka, Miki

2012-01-12

Hominin evolution has involved a continuous process of addition of new kinds of cognitive capacity, including those relating to manufacture and use of tools and to the establishment of linguistic faculties. The dramatic expansion of the brain that accompanied additions of new functional areas would have supported such continuous evolution. Extended brain functions would have driven rapid and drastic changes in the hominin ecological niche, which in turn demanded further brain resources to adapt to it. In this way, humans have constructed a novel niche in each of the ecological, cognitive and neural domains, whose interactions accelerated their individual evolution through a process of triadic niche construction. Human higher cognitive activity can therefore be viewed holistically as one component in a terrestrial ecosystem. The brain's functional characteristics seem to play a key role in this triadic interaction. We advance a speculative argument about the origins of its neurobiological mechanisms, as an extension (with wider scope) of the evolutionary principles of adaptive function in the animal nervous system. The brain mechanisms that subserve tool use may bridge the gap between gesture and language--the site of such integration seems to be the parietal and extending opercular cortices.

Information processing in miniature brains

OpenAIRE

Chittka, L.; Skorupski, P.

2011-01-01

Since a comprehensive understanding of brain function and evolution in vertebrates is often hobbled by the sheer size of the nervous system, as well as ethical concerns, major research efforts have been made to understand the neural circuitry underpinning behaviour and cognition in invertebrates, and its costs and benefits under natural conditions. This special feature of Proceedings of the Royal Society B contains an idiosyncratic range of current research perspectives on neural underpinning...

Brain evolution relating to family, play, and the separation call.

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MacLean, P D

1985-04-01

Mammals stem from the mammal-like reptiles (therapsids) that were widely prevalent in Pangaea 250 million years ago. In the evolutionary transition from reptiles to mammals, three key developments were (1) nursing, in conjunction with maternal care; (2) audiovocal communication for maintaining maternal-offspring contact; and (3) play. The separation call perhaps ranks as the earliest and most basic mammalian vocalization, while play may have functioned originally to promote harmony in the nest. How did such family related behavior develop? In its evolution, the forebrain of advanced mammals has expanded as a triune structure that anatomically and chemically reflects ancestral commonalities with reptiles, early mammals, and late mammals. Recent findings suggest that the development of the behavioral triad in question may have depended on the evolution of the thalamocingulate division of the limbic system, a derivative from early mammals. The thalamocingulate division (which has no distinctive counterpart in the reptilian brain) is, in turn, geared in with the prefrontal neocortex that, in human beings, may be inferred to play a key role in familial acculturation.

Smaller brain size likely in young adults (<40 years old) with depressive symptoms compared to healthy controls. A retrospective study

International Nuclear Information System (INIS)

Adachi, Michito; Sato, Takamichi; Kawaguchi, Etsuko; Shibata, Akiko

2011-01-01

The aim of this study was to determine whether the brain size of young patients with depressive symptoms is smaller than that of healthy controls using magnetic resonance imaging (MRI). We retrospectively evaluated brain size by calculating the ratio of the brain area to that of the skull (the brain-to-skull ratio) on routine MRI scans including the splenium of the corpus callosum obtained from 19 patients <40 years old with depressive symptoms in 2009. The controls were 12 healthy individuals <40 years old who underwent MRI for medical examinations. The mean brain-to-skull ratio of the control group was 0.850±0.022 (range 0.822-0.889), and that of the patient group was 0.819±0.041 (range 0.756-0.878). An unpaired t-test showed a significant difference in the brain-to-skull ratios between these groups (P=0.011). In particular, in 7 of the 19 patients with longer duration of illness and more severe symptoms, the brain-to-skull ratio was 89%-92% of the mean ratio of the control group. The brain size of young patients with depressive symptoms appears to be smaller than that of healthy controls. (author)

Seasonal evolution of the Arctic marginal ice zone and its power-law obeying floe size distribution

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Zhang, J.; Stern, H. L., III; Schweiger, A. J. B.; Steele, M.; Hwang, P. B.

2017-12-01

A thickness, floe size, and enthalpy distribution (TFED) sea ice model, implemented numerically into the Pan-arctic Ice-Ocean Modeling and Assimilation System (PIOMAS), is used to investigate the seasonal evolution of the Arctic marginal ice zone (MIZ) and its floe size distribution. The TFED sea ice model, by coupling the Zhang et al. [2015] sea ice floe size distribution (FSD) theory with the Thorndike et al. [1975] ice thickness distribution (ITD) theory, simulates 12-category FSD and ITD explicitly and jointly. A range of ice thickness and floe size observations were used for model calibration and validation. The model creates FSDs that generally obey a power law or upper truncated power law, as observed by satellites and aerial surveys. In this study, we will examine the role of ice fragmentation and lateral melting in altering FSDs in the Arctic MIZ. We will also investigate how changes in FSD impact the seasonal evolution of the MIZ by modifying the thermodynamic processes.

THE SIZE EVOLUTION OF PASSIVE GALAXIES: OBSERVATIONS FROM THE WIDE-FIELD CAMERA 3 EARLY RELEASE SCIENCE PROGRAM

International Nuclear Information System (INIS)

Ryan, R. E. Jr.; McCarthy, P. J.; Cohen, S. H.; Rutkowski, M. J.; Mechtley, M. R.; Windhorst, R. A.; Yan, H.; Hathi, N. P.; Koekemoer, A. M.; Bond, H. E.; Bushouse, H.; O'Connell, R. W.; Balick, B.; Calzetti, D.; Crockett, R. M.; Disney, M.; Dopita, M. A.; Frogel, J. A.; Hall, D. N. B.; Holtzman, J. A.

2012-01-01

We present the size evolution of passively evolving galaxies at z ∼ 2 identified in Wide-Field Camera 3 imaging from the Early Release Science program. Our sample was constructed using an analog to the passive BzK galaxy selection criterion, which isolates galaxies with little or no ongoing star formation at z ∼> 1.5. We identify 30 galaxies in ∼40 arcmin 2 to H obs ∼ * ∼ 10 11 M ☉ ) undergo the strongest evolution from z ∼ 2 to the present. Parameterizing the size evolution as (1 + z) –α , we find a tentative scaling of α ≈ (– 0.6 ± 0.7) + (0.9 ± 0.4)log (M * /10 9 M ☉ ), where the relatively large uncertainties reflect the poor sampling in stellar mass due to the low numbers of high-redshift systems. We discuss the implications of this result for the redshift evolution of the M * -R e relation for red galaxies.

Postoperative Stereotactic Radiosurgery Without Whole-Brain Radiation Therapy for Brain Metastases: Potential Role of Preoperative Tumor Size

International Nuclear Information System (INIS)

Hartford, Alan C.; Paravati, Anthony J.; Spire, William J.; Li, Zhongze; Jarvis, Lesley A.; Fadul, Camilo E.; Rhodes, C. Harker; Erkmen, Kadir; Friedman, Jonathan; Gladstone, David J.; Hug, Eugen B.; Roberts, David W.; Simmons, Nathan E.

2013-01-01

Purpose: Radiation therapy following resection of a brain metastasis increases the probability of disease control at the surgical site. We analyzed our experience with postoperative stereotactic radiosurgery (SRS) as an alternative to whole-brain radiotherapy (WBRT), with an emphasis on identifying factors that might predict intracranial disease control and overall survival (OS). Methods and Materials: We retrospectively reviewed all patients through December 2008, who, after surgical resection, underwent SRS to the tumor bed, deferring WBRT. Multiple factors were analyzed for time to intracranial recurrence (ICR), whether local recurrence (LR) at the surgical bed or “distant” recurrence (DR) in the brain, for time to WBRT, and for OS. Results: A total of 49 lesions in 47 patients were treated with postoperative SRS. With median follow-up of 9.3 months (range, 1.1-61.4 months), local control rates at the resection cavity were 85.5% at 1 year and 66.9% at 2 years. OS rates at 1 and 2 years were 52.5% and 31.7%, respectively. On univariate analysis (preoperative) tumors larger than 3.0 cm exhibited a significantly shorter time to LR. At a cutoff of 2.0 cm, larger tumors resulted in significantly shorter times not only for LR but also for DR, ICR, and salvage WBRT. While multivariate Cox regressions showed preoperative size to be significant for times to DR, ICR, and WBRT, in similar multivariate analysis for OS, only the graded prognostic assessment proved to be significant. However, the number of intracranial metastases at presentation was not significantly associated with OS nor with other outcome variables. Conclusions: Larger tumor size was associated with shorter time to recurrence and with shorter time to salvage WBRT; however, larger tumors were not associated with decrements in OS, suggesting successful salvage. SRS to the tumor bed without WBRT is an effective treatment for resected brain metastases, achieving local control particularly for tumors up to

Neuroenergetics: How energy constraints shape brain function

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CERN. Geneva

2016-01-01

The nervous system consumes a disproportionate fraction of the resting body’s energy production. In humans, the brain represents 2% of the body’s mass, yet it accounts for ~20% of the total oxygen consumption. Expansion in the size of the brain relative to the body and an increase in the number of connections between neurons during evolution underpin our cognitive powers and are responsible for our brains’ high metabolic rate. The molecules at the center of cellular energy metabolism also act as intercellular signals and constitute an important communication pathway, coordinating for instance the immune surveillance of the brain. Despite the significance of energy consumption in the nervous system, how energy constrains and shapes brain function is often under appreciated. I will illustrate the importance of brain energetics and metabolism with two examples from my recent work. First, I will show how the brain trades information for energy savings in the visual pathway. Indeed, a significant fraction ...

Contribution of brain size to IQ and educational underperformance in extremely preterm adolescents.

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Jeanie L Y Cheong

Full Text Available OBJECTIVES: Extremely preterm (EP survivors have smaller brains, lower IQ, and worse educational achievement than their term-born peers. The contribution of smaller brain size to the IQ and educational disadvantages of EP is unknown. This study aimed (i to compare brain volumes from multiple brain tissues and structures between EP-born (< 28 weeks and term-born (≥ 37 weeks control adolescents, (ii to explore the relationships of brain tissue volumes with IQ and basic educational skills and whether this differed by group, and (iii to explore how much total brain tissue volume explains the underperformance of EP adolescents compared with controls. METHODS: Longitudinal cohort study of 148 EP and 132 term controls born in Victoria, Australia in 1991-92. At age 18, magnetic resonance imaging-determined brain volumes of multiple tissues and structures were calculated. IQ and educational skills were measured using the Wechsler Abbreviated Scale of Intelligence (WASI and the Wide Range Achievement Test(WRAT-4, respectively. RESULTS: Brain volumes were smaller in EP adolescents compared with controls (mean difference [95% confidence interval] of -5.9% [-8.0, -3.7%] for total brain tissue volume. The largest relative differences were noted in the thalamus and hippocampus. The EP group had lower IQs(-11.9 [-15.4, -8.5], spelling(-8.0 [-11.5, -4.6], math computation(-10.3 [-13.7, -6.9] and word reading(-5.6 [-8.8, -2.4] scores than controls; all p-values<0.001. Volumes of total brain tissue and other brain tissues and structures correlated positively with IQ and educational skills, a relationship that was similar for both the EP and controls. Total brain tissue volume explained between 20-40% of the IQ and educational outcome differences between EP and controls. CONCLUSIONS: EP adolescents had smaller brain volumes, lower IQs and poorer educational performance than controls. Brain volumes of multiple tissues and structures are related to IQ and

Nonapeptides and the Evolution of Social Group Sizes in Birds

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James L. Goodson

2011-03-01

Full Text Available Species-typical patterns of grouping have profound impacts on many aspects of physiology and behavior. However, prior to our recent studies in estrildid finches, neural mechanisms that titrate species-typical group size preferences, independent of other aspects of social organization (e.g., mating system and parental care, have been wholly unexplored, likely because species-typical group size is typically confounded with other aspects of behavior and biology. An additional complication is that components of social organization are evolutionarily labile and prone to repeated divergence and convergence. Hence, we cannot assume that convergence in social structure has been produced by convergent modifications to the same neural characters, and thus any comparative approach to grouping must include not only species that differ in their species-typical group sizes, but also species that exhibit convergent evolution in this aspect of social organization. Using five estrildid finch species that differ selectively in grouping (all biparental and monogamous we have demonstrated that neural motivational systems evolve in predictable ways in relation to species-typical group sizes, including convergence in two highly gregarious species and convergence in two relatively asocial, territorial species. These systems include nonapeptide (vasotocin and mesotocin circuits that encode the valence of social stimuli (positive-negative, titrate group-size preferences, and modulate anxiety-like behaviors. Nonapeptide systems exhibit functional and anatomical properties that are biased towards gregarious species, and experimental reductions of nonapeptide signaling by receptor antagonism and antisense oligonucleotides significantly decrease preferred group sizes in the gregarious zebra finch. Combined, these findings suggest that selection on species-typical group size may reliably target the same neural motivation systems when a given social structure evolves

Primate brain architecture and selection in relation to sex.

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Lindenfors, Patrik; Nunn, Charles L; Barton, Robert A

2007-05-10

Social and competitive demands often differ between the sexes in mammals. These differing demands should be expected to produce variation in the relative sizes of various brain structures. Sexual selection on males can be predicted to influence brain components handling sensory-motor skills that are important for physical competition or neural pathways involving aggression. Conversely, because female fitness is more closely linked to ecological factors and social interactions that enable better acquisition of resources, social selection on females should select for brain components important for navigating social networks. Sexual and social selection acting on one sex could produce sexual dimorphism in brain structures, which would result in larger species averages for those same brain structures. Alternatively, sex-specific selection pressures could produce correlated effects in the other sex, resulting in larger brain structures for both males and females of a species. Data are presently unavailable for the sex-specific sizes of brain structures for anthropoid primates, but under either scenario, the effects of sexual and social selection should leave a detectable signal in average sizes of brain structures for different species. The degree of male intra-sexual selection was positively correlated with several structures involved in autonomic functions and sensory-motor skills, and in pathways relating to aggression and aggression control. The degree of male intra-sexual selection was not correlated with relative neocortex size, which instead was significantly positively correlated with female social group size, but negatively correlated with male group size. Sexual selection on males and social selection on females have exerted different effects on primate brain architecture. Species with a higher degree of male intra-sexual selection carry a neural signature of an evolutionary history centered on physical conflicts, but no traces of increased demands on

Primate brain architecture and selection in relation to sex

Directory of Open Access Journals (Sweden)

Nunn Charles L

2007-05-01

Full Text Available Abstract Background Social and competitive demands often differ between the sexes in mammals. These differing demands should be expected to produce variation in the relative sizes of various brain structures. Sexual selection on males can be predicted to influence brain components handling sensory-motor skills that are important for physical competition or neural pathways involving aggression. Conversely, because female fitness is more closely linked to ecological factors and social interactions that enable better acquisition of resources, social selection on females should select for brain components important for navigating social networks. Sexual and social selection acting on one sex could produce sexual dimorphism in brain structures, which would result in larger species averages for those same brain structures. Alternatively, sex-specific selection pressures could produce correlated effects in the other sex, resulting in larger brain structures for both males and females of a species. Data are presently unavailable for the sex-specific sizes of brain structures for anthropoid primates, but under either scenario, the effects of sexual and social selection should leave a detectable signal in average sizes of brain structures for different species. Results The degree of male intra-sexual selection was positively correlated with several structures involved in autonomic functions and sensory-motor skills, and in pathways relating to aggression and aggression control. The degree of male intra-sexual selection was not correlated with relative neocortex size, which instead was significantly positively correlated with female social group size, but negatively correlated with male group size. Conclusion Sexual selection on males and social selection on females have exerted different effects on primate brain architecture. Species with a higher degree of male intra-sexual selection carry a neural signature of an evolutionary history centered on

The use of magnetic resonance imaging to study the brain size of young children with autism

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Farah Ashrafzadeh

2016-07-01

Full Text Available Introduction: Autism spectrum disorder (ASD is a syndrome of social communication deficits and repetitive behaviors or restricted interests. While the impairments associated with ASD tend to deteriorate from childhood into adulthood, it is of critical importance that the syndrome is diagnosed at an early age. One means of facilitating this is through understanding how the brain of people with ASD develops from early childhood. Magnetic resonance imaging (MRI is the method of choice for in vivo and non-invasive investigations of the morphology of the human brain, especially when the subjects are children. In this study, we conducted a systematic review of existing structural MRI studies that have investigated brain size in ASD children of up to 5 years old. Methods: In this study, we systematically reviewed published papers that describe research studies in which the brain size of ASD children has been examined. PubMed and Scopus databases were searched for all relevant original articles that described the use of MRI techniques to study ASD patients who were between 1 and 5 years old. To be included in the review, all studies needed to be cohort and case series that involved at least 10 patients. No time limitations were placed on the searched articles within the inclusion criteria. The exclusion criteria were non-English articles, case reports, and articles that described research involving subjects that were not within the qualifying age range of 1-5 years old.Result: After an initial screening process through which the title, abstracts, and full text of the articles were reviewed to confirm they met the inclusion criteria, a total of 10 relevant articles were studied in depth. All studies found that children with ASD who were within the selected age range had a larger brain size than children without ASD.Discussion: The findings of recent studies indicate that the vast majority of ASD patients exhibit an enlarged brain; however, the extent of

Tempo and mode in human evolution.

Science.gov (United States)

McHenry, H M

1994-01-01

The quickening pace of paleontological discovery is matched by rapid developments in geochronology. These new data show that the pattern of morphological change in the hominid lineage was mosaic. Adaptations essential to bipedalism appeared early, but some locomotor features changed much later. Relative to the highly derived postcrania of the earliest hominids, the craniodental complex was quite primitive (i.e., like the reconstructed last common ancestor with the African great apes). The pattern of craniodental change among successively younger species of Hominidae implies extensive parallel evolution between at least two lineages in features related to mastication. Relative brain size increased slightly among successively younger species of Australopithecus, expanded significantly with the appearance of Homo, but within early Homo remained at about half the size of Homo sapiens for almost a million years. Many apparent trends in human evolution may actually be due to the accumulation of relatively rapid shifts in successive species. PMID:8041697

Clinical observations of the brain abscesses, especially on the computed tomographic brain scan findings

International Nuclear Information System (INIS)

Kitano, Masahiko; Kuroda, Ryotaro; Yamada, Yasufumi; Yorimae, Akira; Akai, Fumiharu; Watanabe, Masaru; Nakatani, Jiro; Ioku, Masahiko

1988-01-01

Fifteen cases with pyogenic brain abscess were experienced in our clinic during the last 7 years. The records of these patients were examined to evaluate the clinical stage and the result of several treatments. In 12 operative cases, diagnosis was made by fluid aspirated from the abscess. Bacteria were cultured from the fluid in 5 among these cases. In 3 other non-operative patients, diagnosis was based on computed tomographic (CT) brain scans and laboratory studies. Each volume of the brain abscess and surrounding brain edema was measured on serial CT scans to evaluate the clinical stage and the abscess evolution. In symptoms and signs, it has been thought that one of the factors contributing to mortality was the level of consciousness. In this study, the disturbance of consciousness did not correlate with the size of abscess, but with that of edema. The cases reported here were divided into 3 groups according to the volume of abscess and of edema on initial CT scans. The cases of group A had small surrounding edema ( 50 ml) and small abscess ( 25 ml). The group A had slight change in the clinical status and the size of edema, but the others had severe change. Three phase changes in edema size were seen in the group B regardless of therapeutic modalities ; showing almost constant increase in first 2 weeks, great decrease in second 2 weeks and moderate decrease following these 4 weeks. In the group C, however, these phases were seen only in early operation cases. (J.P.N.)

Lemur Biorhythms and Life History Evolution.

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Russell T Hogg

Full Text Available Skeletal histology supports the hypothesis that primate life histories are regulated by a neuroendocrine rhythm, the Havers-Halberg Oscillation (HHO. Interestingly, subfossil lemurs are outliers in HHO scaling relationships that have been discovered for haplorhine primates and other mammals. We present new data to determine whether these species represent the general lemur or strepsirrhine condition and to inform models about neuroendocrine-mediated life history evolution. We gathered the largest sample to date of HHO data from histological sections of primate teeth (including the subfossil lemurs to assess the relationship of these chronobiological measures with life history-related variables including body mass, brain size, age at first female reproduction, and activity level. For anthropoids, these variables show strong correlations with HHO conforming to predictions, though body mass and endocranial volume are strongly correlated with HHO periodicity in this group. However, lemurs (possibly excepting Daubentonia do not follow this pattern and show markedly less variability in HHO periodicity and lower correlation coefficients and slopes. Moreover, body mass is uncorrelated, and brain size and activity levels are more strongly correlated with HHO periodicity in these animals. We argue that lemurs evolved this pattern due to selection for risk-averse life histories driven by the unpredictability of the environment in Madagascar. These results reinforce the idea that HHO influences life history evolution differently in response to specific ecological selection regimes.

Lemur Biorhythms and Life History Evolution.

Science.gov (United States)

Hogg, Russell T; Godfrey, Laurie R; Schwartz, Gary T; Dirks, Wendy; Bromage, Timothy G

2015-01-01

Skeletal histology supports the hypothesis that primate life histories are regulated by a neuroendocrine rhythm, the Havers-Halberg Oscillation (HHO). Interestingly, subfossil lemurs are outliers in HHO scaling relationships that have been discovered for haplorhine primates and other mammals. We present new data to determine whether these species represent the general lemur or strepsirrhine condition and to inform models about neuroendocrine-mediated life history evolution. We gathered the largest sample to date of HHO data from histological sections of primate teeth (including the subfossil lemurs) to assess the relationship of these chronobiological measures with life history-related variables including body mass, brain size, age at first female reproduction, and activity level. For anthropoids, these variables show strong correlations with HHO conforming to predictions, though body mass and endocranial volume are strongly correlated with HHO periodicity in this group. However, lemurs (possibly excepting Daubentonia) do not follow this pattern and show markedly less variability in HHO periodicity and lower correlation coefficients and slopes. Moreover, body mass is uncorrelated, and brain size and activity levels are more strongly correlated with HHO periodicity in these animals. We argue that lemurs evolved this pattern due to selection for risk-averse life histories driven by the unpredictability of the environment in Madagascar. These results reinforce the idea that HHO influences life history evolution differently in response to specific ecological selection regimes.

Diagnosis and temporal evolution of signs of intracranial hypotension on MRI of the brain

Energy Technology Data Exchange (ETDEWEB)

Forghani, R. [McGill University Health Center, Department of Radiology, Montreal, Que (Canada); Massachusetts General Hospital, Division of Neuroradiology, Boston, MA (United States); Farb, R.I. [University of Toronto, Department of Medical Imaging, Division of Neuroradiology, Toronto Western Hospital, Toronto, Ontario (Canada)

2008-12-15

A comprehensive evaluation of cranial magnetic resonance imagings (MRIs) of 23 patients with intracranial hypotension (IH) was performed, and the evolution of the abnormalities on follow-up MRIs was correlated with the clinical outcome. The MRI report database at the University Health Network in Toronto was searched, and 23 cases of IH were identified between 2001 and 2007. A retrospective review of the MRIs of the brain and the electronic patient chart was performed. A control group of 40 subjects was also selected to complement the analysis of the pituitary gland. A positive venous distention sign (VDS) was observed in 23 out of 23 patients and was the first sign to disappear on early follow-up scans following successful treatment. Pachymeningeal enhancement was seen in 23 out of 23 patients, and pachymeningeal thickening was detectable on unenhanced fluid attenuation inversion recovery (FLAIR) sequences in 17 out of 23 patients (74%). An increase in pituitary size in IH was also demonstrated based on the measured pituitary height and was qualitatively detectable in 12 out of 21 (57%) patients as the protrusion of the pituitary gland above the sella turica (two postpartum patients were excluded from this analysis). Overall, there was good correlation between the imaging findings and clinical outcome following treatment. Accurate diagnosis and follow-up of IH should be possible is some patients on unenhanced MRI of the brain by combining the signs on FLAIR and sagittal T1W images, enabling timely diagnosis in unsuspected cases and avoiding unnecessary administration of gadolinium compounds. In addition, VDS might be useful for early assessment of response to treatment. (orig.)

MINOR MERGERS AND THE SIZE EVOLUTION OF ELLIPTICAL GALAXIES

International Nuclear Information System (INIS)

Naab, Thorsten; Johansson, Peter H.; Ostriker, Jeremiah P.

2009-01-01

Using a high-resolution hydrodynamical cosmological simulation of the formation of a massive spheroidal galaxy we show that elliptical galaxies can be very compact and massive at high redshift in agreement with recent observations. Accretion of stripped infalling stellar material increases the size of the system with time and the central concentration is reduced by dynamical friction of the surviving stellar cores. In a specific case of a spheroidal galaxy with a final stellar mass of 1.5 x 10 11 M sun we find that the effective radius r e increases from 0.7 ± 0.2 kpc at z = 3 to r e = 2.4 ± 0.4 kpc at z = 0 with a concomitant decrease in the effective density of an order of magnitude and a decrease of the central velocity dispersion by approximately 20% over this time interval. A simple argument based on the virial theorem shows that during the accretion of weakly bound material (minor mergers) the radius can increase as the square of the mass in contrast to the usual linear rate of increase for major mergers. By undergoing minor mergers compact high-redshift spheroids can evolve into present-day systems with sizes and concentrations similar to observed local ellipticals. This indicates that minor mergers may be the main driver for the late evolution of sizes and densities of early-type galaxies.

Relationship between apathy and tumor location, size, and brain edema in patients with intracranial meningioma

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Peng Y

2015-07-01

Full Text Available Yihua Peng,1,* Chunhong Shao,1,* Ye Gong,2 Xuehai Wu,2 Weijun Tang,3 Shenxun Shi1 1Psychiatry Department, 2Neurosurgery Department, 3Radiology Department, Huashan Hospital, Fudan University, People’s Republic of China *These authors contributed equally to this work Background: The purpose of this study is to assess the relationship between apathy and tumor location, size, and brain edema in patients with intracranial meningioma. Methods: We enrolled 65 consecutive patients with meningioma and 31 normal controls matched for age, gender, and education. The patients were divided into frontal or non-frontal (NF meningioma groups based on magnetic resonance imaging; the frontal group was then subdivided to dorsolateral frontal (DLF, medial frontal (MF, and ventral frontal (VF groups. Tumor size and brain edema were also recorded. Apathy was assessed by the Apathy Evaluation Scale (AES. Assessments were carried out 1 week before and 3 months after surgery, respectively. Logistic regression analysis was performed to identify the predictive effect of tumor size, location, and brain edema on apathy. Analysis of variance and chi-square analysis were applied to compare apathy scores and apathy rates among the frontal, NF, and normal control groups, and all subgroups within the frontal group. Results: Compared with the NF and control groups, the mean AES score was much higher in the frontal group (34.0±8.3 versus 28.63±6.0, P=0.008, and 26.8±4.2, P<0.001. Subgroup analysis showed that AES scores in the MF group (42.1±6.6 and VF group (34.7±8.0 were higher than in the DLF group (28.5±4.36, NF group, and control group (P<0.05. The apathy rate was 63.6% in the MF group and 25% in the VF group, and significantly higher than in the DLF (5.6%, NF (5.3%, and control (0% groups (P<0.001. A moderate correlation was found between AES score and mean diameter of the meningioma in all patient groups. Further analysis demonstrated that the correlation existed in

THE SIZE EVOLUTION OF PASSIVE GALAXIES: OBSERVATIONS FROM THE WIDE-FIELD CAMERA 3 EARLY RELEASE SCIENCE PROGRAM

Energy Technology Data Exchange (ETDEWEB)

Ryan, R. E. Jr. [Physics Department, University of California, Davis, CA 95616 (United States); McCarthy, P. J. [Observatories of the Carnegie Institute of Washington, Pasadena, CA 91101 (United States); Cohen, S. H.; Rutkowski, M. J.; Mechtley, M. R.; Windhorst, R. A. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Yan, H. [Center for Cosmology and Astroparticle Physics, Ohio State University, Columbus, OH 43210 (United States); Hathi, N. P. [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Koekemoer, A. M.; Bond, H. E.; Bushouse, H. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); O' Connell, R. W. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Balick, B. [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Calzetti, D. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Crockett, R. M. [Department of Physics, University of Oxford, Oxford OX1 3PU (United Kingdom); Disney, M. [School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom); Dopita, M. A. [Research School of Astronomy and Astrophysics, The Australian National University, Weston Creek, ACT 2611 (Australia); Frogel, J. A. [Galaxies Unlimited, Lutherville, MD 21093 (United States); Hall, D. N. B. [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Holtzman, J. A., E-mail: rryan@physics.ucdavis.edu [Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States); and others

2012-04-10

We present the size evolution of passively evolving galaxies at z {approx} 2 identified in Wide-Field Camera 3 imaging from the Early Release Science program. Our sample was constructed using an analog to the passive BzK galaxy selection criterion, which isolates galaxies with little or no ongoing star formation at z {approx}> 1.5. We identify 30 galaxies in {approx}40 arcmin{sup 2} to H < 25 mag. By fitting the 10-band Hubble Space Telescope photometry from 0.22 {mu}m {approx}< {lambda}{sub obs} {approx}< 1.6 {mu}m with stellar population synthesis models, we simultaneously determine photometric redshift, stellar mass, and a bevy of other population parameters. Based on the six galaxies with published spectroscopic redshifts, we estimate a typical redshift uncertainty of {approx}0.033(1 + z). We determine effective radii from Sersic profile fits to the H-band image using an empirical point-spread function. By supplementing our data with published samples, we propose a mass-dependent size evolution model for passively evolving galaxies, where the most massive galaxies (M{sub *} {approx} 10{sup 11} M{sub Sun }) undergo the strongest evolution from z {approx} 2 to the present. Parameterizing the size evolution as (1 + z){sup -{alpha}}, we find a tentative scaling of {alpha} Almost-Equal-To (- 0.6 {+-} 0.7) + (0.9 {+-} 0.4)log (M{sub *}/10{sup 9} M{sub Sun }), where the relatively large uncertainties reflect the poor sampling in stellar mass due to the low numbers of high-redshift systems. We discuss the implications of this result for the redshift evolution of the M{sub *}-R{sub e} relation for red galaxies.

A century of shocks : The evolution of the German city size distribution 1925-1999

NARCIS (Netherlands)

Bosker, Maarten; Brakman, Steven; Garretsen, Harry; Schramm, Marc

This paper uses empirical evidence on the evolution and structure of the West-German city size distribution to assess the relevance of three different theories of urban growth. The West-German case is of particular interest as Germany's urban system has been subject to some of history's largest

An in situ USAXS-SAXS-WAXS study of precipitate size distribution evolution in a model Ni-based alloy.

Science.gov (United States)

Andrews, Ross N; Serio, Joseph; Muralidharan, Govindarajan; Ilavsky, Jan

2017-06-01

Intermetallic γ' precipitates typically strengthen nickel-based superalloys. The shape, size and spatial distribution of strengthening precipitates critically influence alloy strength, while their temporal evolution characteristics determine the high-temperature alloy stability. Combined ultra-small-, small- and wide-angle X-ray scattering (USAXS-SAXS-WAXS) analysis can be used to evaluate the temporal evolution of an alloy's precipitate size distribution (PSD) and phase structure during in situ heat treatment. Analysis of PSDs from USAXS-SAXS data employs either least-squares fitting of a preordained PSD model or a maximum entropy (MaxEnt) approach, the latter avoiding a priori definition of a functional form of the PSD. However, strong low- q scattering from grain boundaries and/or structure factor effects inhibit MaxEnt analysis of typical alloys. This work describes the extension of Bayesian-MaxEnt analysis methods to data exhibiting structure factor effects and low- q power law slopes and demonstrates their use in an in situ study of precipitate size evolution during heat treatment of a model Ni-Al-Si alloy.

Model for evolution of grain size in the rim region of high burnup UO{sub 2} fuel

Energy Technology Data Exchange (ETDEWEB)

Xiao, Hongxing, E-mail: xiaohongxing2003@163.com; Long, Chongsheng; Chen, Hongsheng

2016-04-01

The restructuring process of the high burnup structure (HBS) formation in UO{sub 2} fuel results in sub-micron size grains that accelerate the fission gas swelling, which will raise some concern over the safety of extended the nuclear fuel operation life in the reactor. A mechanistic and engineering model for evolution of grain size in the rim region of high burnup UO{sub 2} fuel based on the experimental observations of the HBS in the literature is presented. The model takes into account dislocations evolution under irradiation and the grain subdivision occur successively at increasing local burnup. It is assumed that the original driving force for subdivision of grain in the HBS of UO{sub 2} fuel is the production and accumulation of dislocation loops during irradiation. The dislocation loops can also be annealed through thermal diffusion when the temperature is high enough. The capability of this model is validated by the comparison with the experimental data of temperature threshold of subdivision, dislocation density and sub-grain size as a function of local burnup. It is shown that the calculated results of the dislocation density and subdivided grain size as a function of local burnup are in good agreement with the experimental results. - Highlights: • A model for evolution of dislocation density and grain size in HBS is proposed. • The dislocation can also be annealed when the temperature is high enough. • Original driving force for subdivision is mostly accumulation of dislocation loops. • The temperature threshold of the subdivision is predicted at 1300–1400 K.

Expensive Brains: “Brainy” Rodents have Higher Metabolic Rate

Science.gov (United States)

Sobrero, Raúl; May-Collado, Laura J.; Agnarsson, Ingi; Hernández, Cristián E.

2011-01-01

Brains are the centers of the nervous system of animals, controlling the organ systems of the body and coordinating responses to changes in the ecological and social environment. The evolution of traits that correlate with cognitive ability, such as relative brain size is thus of broad interest. Brain mass relative to body mass (BM) varies among mammals, and diverse factors have been proposed to explain this variation. A recent study provided evidence that energetics play an important role in brain evolution (Isler and van Schaik, 2006). Using composite phylogenies and data drawn from multiple sources, these authors showed that basal metabolic rate (BMR) correlates with brain mass across mammals. However, no such relationship was found within rodents. Here we re-examined the relationship between BMR and brain mass within Rodentia using a novel species-level phylogeny. Our results are sensitive to parameter evaluation; in particular how species mass is estimated. We detect no pattern when applying an approach used by previous studies, where each species BM is represented by two different numbers, one being the individual that happened to be used for BMR estimates of that species. However, this approach may compromise the analysis. When using a single value of BM for each species, whether representing a single individual, or available species mean, our findings provide evidence that brain mass (independent of BM) and BMR are correlated. These findings are thus consistent with the hypothesis that large brains evolve when the payoff for increased brain mass is greater than the energetic cost they incur. PMID:21811456

Hunter syndrome in an 11-year old girl on enzyme replacement therapy with idursulfase: brain magnetic resonance imaging features and evolution.

Science.gov (United States)

Manara, Renzo; Rampazzo, Angelica; Cananzi, Mara; Salviati, Leonardo; Mardari, Rodica; Drigo, Paola; Tomanin, Rosella; Gasparotto, Nicoletta; Priante, Elena; Scarpa, Maurizio

2010-12-01

Mucopolysaccharidosis type II (MPS-II, Hunter disease) is a X-linked recessive disorder. Affected females are extremely rare, mostly due to skewed X chromosome inactivation. A few papers outline MPS-II brain magnetic resonance imaging (MRI) "gestalt" in males, but neuroradiological reports on females are still lacking. We present an 11-year-old girl affected by the severe form of MPS-II who was followed up over a time span of 8 years, focusing on clinical and brain MRI evolution. In the last 2.5 years, the patient has been treated with enzyme replacement therapy (ERT) with idursulfase (Elaprase™, Shire Human Genetic Therapies AB, Sweden). On brain and cervical MRI examination, abnormalities in our patient did not differ from those detected in male patients: J-shaped pituitary sella, enlargement of perivascular spaces, brain atrophy, mild T2-hyperintensity in the paratrigonal white matter, diffuse platyspondylia, and mild odontoid dysplasia with odontoid cup. Brain atrophy progressed despite ERT introduction, whereas perivascular space enlargement did not change significantly before and after ERT. Cognitive impairment worsened independently from the course of white matter abnormality. Despite a profound knowledge of genetic and biochemical aspects in MPS-II, neuroradiology is still poorly characterized, especially in female patients. Spinal and brain involvement and its natural course and evolution after ERT introduction still need to be clarified.

Spontaneous evolution of an unusual cortical malformation in SOX2 anophthalmia syndrome

Directory of Open Access Journals (Sweden)

Jay Desai

2013-01-01

Full Text Available Brain malformations such as agenesis and dysgenesis of corpus callosum, pituitary hypoplasia, hypothalamic hamartoma, mesial temporal periventricular heterotopia, and abnormally oriented and misshapen hippocampi have been described with SOX2 gene mutations. A neocortical malformation is presented here in association with SOX2 deletion that over time underwent spontaneous evolution and decrease in size.

A new Homo erectus (Zhoukoudian V) brain endocast from China.

Science.gov (United States)

Wu, Xiujie; Schepartz, Lynne A; Liu, Wu

2010-01-22

A new Homo erectus endocast, Zhoukoudian (ZKD) V, is assessed by comparing it with ZKD II, ZKD III, ZKD X, ZKD XI, ZKD XII, Hexian, Trinil II, Sambungmacan (Sm) 3, Sangiran 2, Sangiran 17, KNM-ER 3733, KNM-WT 15 000, Kabwe, Liujiang and 31 modern Chinese. The endocast of ZKD V has an estimated endocranial volume of 1140 ml. As the geological age of ZKD V is younger than the other ZKD H. erectus, evolutionary changes in brain morphology are evaluated. The brain size of the ZKD specimens increases slightly over time. Compared with the other ZKD endocasts, ZKD V shows important differences, including broader frontal and occipital lobes, some indication of fuller parietal lobes, and relatively large brain size that reflect significant trends documented in later hominin brain evolution. Bivariate and principal component analyses indicate that geographical variation does not characterize the ZKD, African and other Asian specimens. The ZKD endocasts share some common morphological and morphometric features with other H. erectus endocasts that distinguish them from Homo sapiens.

The ups and downs of genome size evolution in polyploid species of Nicotiana (Solanaceae)

Czech Academy of Sciences Publication Activity Database

Leitch, I.J.; Hanson, L.; Lim, K.Y.; Kovařík, Aleš; Chase, M.W.; Clarkson, J.J.; Leitch, A.R.

2008-01-01

Roč. 101, č. 6 (2008), s. 805-814 ISSN 0305-7364 R&D Projects: GA ČR(CZ) GA521/07/0116 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : genome size * allopolyploidy * evolution-Nicotiana Subject RIV: BO - Biophysics Impact factor: 2.755, year: 2008

The evolution of body size in extant groups of North American freshwater fishes: speciation, size distributions, and Cope's rule.

Science.gov (United States)

Knouft, Jason H; Page, Lawrence M

2003-03-01

Change in body size within an evolutionary lineage over time has been under investigation since the synthesis of Cope's rule, which suggested that there is a tendency for mammals to evolve larger body size. Data from the fossil record have subsequently been examined for several other taxonomic groups to determine whether they also displayed an evolutionary increase in body size. However, we are not aware of any species-level study that has investigated the evolution of body size within an extant continental group. Data acquired from the fossil record and data derived from the evolutionary relationships of extant species are not similar, with each set exhibiting both strengths and weaknesses related to inferring evolutionary patterns. Consequently, expectation that general trends exhibited in the fossil record will correspond to patterns in extant groups is not necessarily warranted. Using phylogenetic relationships of extant species, we show that five of nine families of North American freshwater fishes exhibit an evolutionary trend of decreasing body size. These trends result from the basal position of large species and the more derived position of small species within families. Such trends may be caused by the invasion of small streams and subsequent isolation and speciation. This pattern, potentially influenced by size-biased dispersal rates and the high percentage of small streams in North America, suggests a scenario that could result in the generation of the size-frequency distribution of North American freshwater fishes.

Diversification Rates and the Evolution of Species Range Size Frequency Distribution

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Silvia Castiglione

2017-11-01

Full Text Available The geographic range sizes frequency distribution (RFD within clades is typically right-skewed with untransformed data, and bell-shaped or slightly left-skewed under the log-transformation. This means that most species within clades occupy diminutive ranges, whereas just a few species are truly widespread. A number of ecological and evolutionary explanations have been proposed to account for this pattern. Among the latter, much attention has been given to the issue of how extinction and speciation probabilities influence RFD. Numerous accounts now convincingly demonstrate that extinction rate decreases with range size, both in living and extinct taxa. The relationship between range size and speciation rate, though, is much less obvious, with either small or large ranged species being proposed to originate more daughter taxa. Herein, we used a large fossil database including 21 animal clades and more than 80,000 fossil occurrences distributed over more than 400 million years of marine metazoans (exclusive of vertebrates evolution, to test the relationship between extinction rate, speciation rate, and range size. As expected, we found that extinction rate almost linearly decreases with range size. In contrast, speciation rate peaks at the large (but not the largest end of the range size spectrum. This is consistent with the peripheral isolation mode of allopatric speciation being the main mechanism of species origination. The huge variation in phylogeny, fossilization potential, time of fossilization, and the overarching effect of mass extinctions suggest caution must be posed at generalizing our results, as individual clades may deviate significantly from the general pattern.

Brain stem type neuro-Behcet's syndrome

International Nuclear Information System (INIS)

Kataoka, Satoshi; Hirose, Genjiro; Kosoegawa, Hiroshi; Oda, Rokuhei; Yoshioka, Akira

1987-01-01

Two cases of brain stem type Neuro-Behcet's syndrome were evaluated by brain CT and Magnetic Resonance Imaging (Super-conducting type, 0.5 tesla) to correlate with the neurological findings. In the acute phase, low density area with peripheral enhancement effect and mass effect were seen at the brain stem in brain CT. MRI revealed a extensive high intensity signal area mainly involving the corticospinal tract in the meso-diencephalon as well as pons by T 2 weighted images (spin echo, TR = 1, 600 msec, TE = 90 msec) and the value of T 1 , T 2 , at the brain stem lesion were prolonged moderately. After high dose steroid treatment, the low density area in brain CT and high signal area in MRI were gradually reduced in its size. Peripheral enhancement effect in brain CT disappeared within 10 months in case 1, one month in the other case. In the chronic stage, the reduction of low density area and atrophy of brain stem were noted in brain CT. The lesion in chronic stage had low intensity in T 1 , T 2 weighted images and the T 1 , T 2 values at the lesion were mildly prolonged in MRI. Sequentially CT with enhancement and MRI examinations with T 1 , T 2 weighted images were useful to detect the lesion and to evaluate the activity, evolution of brain stem type Neuro-Behcet's syndrome. (author)

Evolution of technetium-99m-HMPAO SPECT and brain mapping in a patient presenting with echolalia and palilalia.

Science.gov (United States)

Dierckx, R A; Saerens, J; De Deyn, P P; Verslegers, W; Marien, P; Vandevivere, J

1991-08-01

A 78-yr-old woman presented with transient echolalia and palilalia. She had suffered from Parkinson's disease for 2 yr. Routine laboratory examination showed hypotonic hyponatremia, but was otherwise unremarkable. Brain mapping revealed a bifrontal delta focus, more pronounced on the right. Single photon emission computed tomography (SPECT) of the brain with technetium-99m labeled d,l hexamethylpropylene-amine oxime (99mTc-HMPAO), performed during the acute episode showed relative frontoparietal hypoactivity. Brain mapping performed after disappearance of the echolalia and palilalia, which persisted only for 1 day, was normal. By contrast, SPECT findings persisted for more than 3 wk. Features of particular interest in the presented patient are the extensive defects seen on brain SPECT despite the absence of morphologic lesions, the congruent electrophysiologic changes and their temporal relationship with the clinical evolution.

Critical Evolution of Damage Toward System-Size Failure in Crystalline Rock

Science.gov (United States)

Renard, François; Weiss, Jérôme; Mathiesen, Joachim; Ben-Zion, Yehuda; Kandula, Neelima; Cordonnier, Benoît

2018-02-01

Rock failure under shear loading conditions controls earthquake and faulting phenomena. We study the dynamics of microscale damage precursory to shear faulting in a quartz-monzonite rock representative of crystalline rocks of the continental crust. Using a triaxial rig that is transparent to X-rays, we image the mechanical evolution of centimeter-size core samples by in situ synchrotron microtomography with a resolution of 6.5 μm. Time-lapse three-dimensional images of the samples inside the rig provide a unique data set of microstructural evolution toward faulting. Above a yield point there is a gradual weakening during which microfractures nucleate and grow until this damage span the whole sample. This leads to shear faults oriented about 30° to the main compressive stress in agreement with Anderson's theory and macroscopic failure. The microfractures can be extracted from the three-dimensional images, and their dynamics and morphology (i.e., number, volume, orientation, shape, and largest cluster) are quantified as a function of increasing stress toward failure. The experimental data show for the first time that the total volume of microfractures, the rate of damage growth, and the size of the largest microfracture all increase and diverge when approaching faulting. The average flatness of the microfractures (i.e., the ratio between the second and third eigenvalues of their covariance matrix) shows a significant decrease near failure. The precursors to faulting developing in the future faulting zone are controlled by the evolving microfracture population. Their divergent dynamics toward failure is reminiscent of a dynamical critical transition.

Changes in brain size during the menstrual cycle.

Directory of Open Access Journals (Sweden)

Georg Hagemann

Full Text Available BACKGROUND: There is increasing evidence for hormone-dependent modification of function and behavior during the menstrual cycle, but little is known about associated short-term structural alterations of the brain. Preliminary studies suggest that a hormone-dependent decline in brain volume occurs in postmenopausal, or women receiving antiestrogens, long term. Advances in serial MR-volumetry have allowed for the accurate detection of small volume changes of the brain. Recently, activity-induced short-term structural plasticity of the brain was demonstrated, challenging the view that the brain is as rigid as formerly believed. METHODOLOGY/PRINCIPAL FINDINGS: We used MR-volumetry to investigate short-term brain volume changes across the menstrual cycle in women or a parallel 4 week period in men, respectively. We found a significant grey matter volume peak and CSF loss at the time of ovulation in females. This volume peak did not correlate with estradiol or progesterone hormone levels. Men did not show any significant brain volume alterations. CONCLUSIONS/SIGNIFICANCE: These data give evidence of short-term hormone-dependent structural brain changes during the menstrual cycle, which need to be correlated with functional states and have to be considered in structure-associated functional brain research.

Analyzing the evolution of young people's brain cancer mortality in Spanish provinces.

Science.gov (United States)

Ugarte, M D; Adin, A; Goicoa, T; López-Abente, G

2015-06-01

To analyze the spatio-temporal evolution of brain cancer relative mortality risks in young population (under 20 years of age) in Spanish provinces during the period 1986-2010. A new and flexible conditional autoregressive spatio-temporal model with two levels of spatial aggregation was used. Brain cancer relative mortality risks in young population in Spanish provinces decreased during the last years, although a clear increase was observed during the 1990s. The global geographical pattern emphasized a high relative mortality risk in Navarre and a low relative mortality risk in Madrid. Although there is a specific Autonomous Region-time interaction effect on the relative mortality risks this effect is weak in the final estimates when compared to the global spatial and temporal effects. Differences in mortality between regions and over time may be caused by the increase in survival rates, the differences in treatment or the availability of diagnostic tools. The increase in relative risks observed in the 1990s was probably due to improved diagnostics with computerized axial tomography and magnetic resonance imaging techniques. Copyright © 2015 Elsevier Ltd. All rights reserved.

Time evolution of the drop size distribution for liquid-liquid dispersion in an agitated tank

Czech Academy of Sciences Publication Activity Database

Šulc, R.; Kysela, Bohuš; Ditl, P.

2018-01-01

Roč. 72, č. 3 (2018), s. 543-553 ISSN 0366-6352 R&D Projects: GA ČR GA16-20175S Institutional support: RVO:67985874 Keywords : liquid–liquid dispersion * drop breakup * drop size distribution * time evolution Subject RIV: BK - Fluid Dynamics Impact factor: 1.258, year: 2016

Why direct effects of predation complicate the social brain hypothesis: And how incorporation of explicit proximate behavioral mechanisms might help.

Science.gov (United States)

van der Bijl, Wouter; Kolm, Niclas

2016-06-01

A growing number of studies have found that large brains may help animals survive by avoiding predation. These studies provide an alternative explanation for existing correlative evidence for one of the dominant hypotheses regarding the evolution of brain size in animals, the social brain hypothesis (SBH). The SBH proposes that social complexity is a major evolutionary driver of large brains. However, if predation both directly selects for large brains and higher levels of sociality, correlations between sociality and brain size may be spurious. We argue that tests of the SBH should take direct effects of predation into account, either by explicitly including them in comparative analyses or by pin-pointing the brain-behavior-fitness pathway through which the SBH operates. Existing data and theory on social behavior can then be used to identify precise candidate mechanisms and formulate new testable predictions. © 2016 WILEY Periodicals, Inc.

The role of the nervous system in fish evolution

Directory of Open Access Journals (Sweden)

Michael H Hofmann

2015-12-01

Full Text Available The nervous system plays an important role in the evolution and adaptation of animals. All sensory and motor functions as well as cognitive abilities are organized in the brain and spinal cord. Volumetric measurements of different brain regions were made in more than 150 species of ray finned fishes as well as in several outgroups. In Actanthopterygii, the hypothalamus shows greatest enlargement most likely due to an enormous visual input via the nucleus glomerulosos. The telencephalon is highly differentiated in many acanthopterygii, mostly coral reef species, but its relative size is not much effected. There is, however, a clear shift from olfactory to visual functions in ray finned fishes. In species with a highly differentiated telencephalon, the area where place memory may be located is very prominent. In basal ray finned fishes, lungfish, amphibia and elasmobranchs, the olfactory bulb is relatively large and the ratio of the olfactory bulb and telencephalon large as well. This holds also for elopomorpha and spiny eels, but in most other groups vision dominates. Apart from differences between larger clades, variation in brain architecture are also seen in closely related species and even between sexes of the same species. Profound differences are present in the cerebellum between male and female swordtails and in the telencephalon of sticklebacks. Morphometric analysis of brain architecture turned out to be an important tool to study the evolution and adaptations of the brain in fishes.

Effect of grain size and arrangement on dynamic damage evolution of ductile metal

International Nuclear Information System (INIS)

Qi Mei-Lan; Zhong Sheng; Fan Duan; Zhao Li; He Hong-Liang

2013-01-01

Plate-impact experiments have been carried out to examine the effect of grain size and grain arrangement on the damage evolution of ultrapure aluminum. Two groups of samples, “cross-cut“ and “longitudinal-cut,“ are obtained from the rolled aluminum rod along different directions. The peak compressive stress is approximately 1.25 GPa−1.61 GPa, which can cause incipient spall damage that is correlated to the material microstructure. The metallographic analyses of all recovered samples show that nearly all damage nucleates at the grain boundaries, especially those with larger curvature. Moreover, under lower shock stress, the spall strength of the “longitudinal-cut“ sample is smaller than that of the “cross-cut“ sample, because the different grain sizes and arrangement of the two samples cause different nucleation, growth, and coalescence processes. In this study, the difference in the damage distribution between “longitudinal-cut“ and “cross-cut“ samples and the causes for this difference under lower shock-loading conditions are also analyzed by both qualitative and semi-quantitative methods. It is very important for these conclusions to establish a reasonable and perfect equation of damage evolution for ductile metals. (condensed matter: structural, mechanical, and thermal properties)

Hominid evolution: genetics versus memetics

Science.gov (United States)

Carter, Brandon

2012-01-01

The last few million years on planet Earth have witnessed two remarkable phases of hominid development, starting with a phase of biological evolution characterized by rather rapid increase of the size of the brain. This has been followed by a phase of even more rapid technological evolution and concomitant expansion of the size of the population that began when our own particular ‘sapiens’ species emerged, just a few hundred thousand years ago. The present investigation exploits the analogy between the neo-Darwinian genetic evolution mechanism governing the first phase, and the memetic evolution mechanism governing the second phase. From the outset of the latter until very recently - about the year 2000 - the growth of the global population N was roughly governed by an equation of the form dN/Ndt=N/T*, in which T* is a coefficient introduced (in 1960) by von Foerster, who evaluated it empirically as about 200 000 million years. It is shown here how the value of this hitherto mysterious timescale governing the memetic phase is explicable in terms of what happened in the preceding genetic phase. The outcome is that the order of magnitude of the Foerster timescale can be accounted for as the product of the relevant (human) generation timescale, about 20 years, with the number of bits of information in the genome, of the order of 10 000 million. Whereas the origin of our ‘homo’ genus may well have involved an evolutionary hard step, it transpires that the emergence of our particular ‘sapiens’ species was rather an automatic process.

Life course evolution of body size and breast cancer survival in the E3N cohort.

Science.gov (United States)

His, Mathilde; Le Guélennec, Marine; Mesrine, Sylvie; Boutron-Ruault, Marie-Christine; Clavel-Chapelon, Françoise; Fagherazzi, Guy; Dossus, Laure

2018-04-15

Although adult obesity has been associated with poor breast cancer survival, data on adiposity at different periods in life and its lifelong evolution are scarce. Our aims were to assess the associations between breast cancer survival and body size during childhood, puberty and early adulthood and body size trajectories from childhood to adulthood. Self-assessed body size at age 8, at puberty, at age 20-25 and at age 35-40 and trajectories of body size of 4,662 breast cancer survivors from the prospective E3N cohort were studied in relation to risk of death from any cause, death from breast cancer and second invasive cancer event using multivariate Cox regression models. Four trajectories of body size were identified (T1 "moderate increase," T2 "stable/low increase," T3 "increase at puberty" and T4 "constantly high"). Compared with stable body size, an increase in body size during adult life was associated with an increased risk of death from any cause (HR T1 vs. T2 = 1.27; 95% CI = 1.01-1.60) and an increased risk of second invasive cancer event (HR T1 vs. T2 = 1.25; 95% CI = 1.06-1.47). Silhouettes at various ages were not associated with survival. Our results suggest that the evolution of body size from childhood to adulthood has a long-term influence on breast cancer survival. Although these results need to be confirmed, this work sheds light on the need to combine lifelong approaches to current BMI to better identify breast cancer survivors who are at higher risk of recurrence or second primary cancer, or of death. © 2017 UICC.

Chernobyl birds have smaller brains.

Directory of Open Access Journals (Sweden)

Anders Pape Møller

2011-02-01

Full Text Available Animals living in areas contaminated by radioactive material from Chernobyl suffer from increased oxidative stress and low levels of antioxidants. Therefore, normal development of the nervous system is jeopardized as reflected by high frequencies of developmental errors, reduced brain size and impaired cognitive abilities in humans. Alternatively, associations between psychological effects and radiation have been attributed to post-traumatic stress in humans.Here we used an extensive sample of 550 birds belonging to 48 species to test the prediction that even in the absence of post-traumatic stress, there is a negative association between relative brain size and level of background radiation. We found a negative association between brain size as reflected by external head volume and level of background radiation, independent of structural body size and body mass. The observed reduction in brain size in relation to background radiation amounted to 5% across the range of almost a factor 5,000 in radiation level. Species differed significantly in reduction in brain size with increasing background radiation, and brain size was the only morphological character that showed a negative relationship with radiation. Brain size was significantly smaller in yearlings than in older individuals.Low dose radiation can have significant effects on normal brain development as reflected by brain size and therefore potentially cognitive ability. The fact that brain size was smaller in yearlings than in older individuals implies that there was significant directional selection on brain size with individuals with larger brains experiencing a viability advantage.

Brightness temperature simulation of snow cover based on snow grain size evolution using in situ data

Science.gov (United States)

Wu, Lili; Li, Xiaofeng; Zhao, Kai; Zheng, Xingming; Jiang, Tao

2016-07-01

Snow depth parameter inversion from passive microwave remote sensing is of great significance to hydrological process and climate systems. The Helsinki University of Technology (HUT) model is a commonly used snow emission model. Snow grain size (SGS) is one of the important input parameters, but SGS is difficult to obtain in broad areas. The time series of SGS are first evolved by an SGS evolution model (Jordan 91) using in situ data. A good linear relationship between the effective SGS in HUT and the evolution SGS was found. Then brightness temperature simulations are performed based on the effective SGS and evolution SGS. The results showed that the biases of the simulated brightness temperatures based on the effective SGS and evolution SGS were -6.5 and -3.6 K, respectively, for 18.7 GHz and -4.2 and -4.0 K for 36.5 GHz. Furthermore, the model is performed in six pixels with different land use/cover type in other areas. The results showed that the simulated brightness temperatures based on the evolution SGS were consistent with those from the satellite. Consequently, evolution SGS appears to be a simple method to obtain an appropriate SGS for the HUT model.

Impact of spot size on plan quality of spot scanning proton radiosurgery for peripheral brain lesions

Energy Technology Data Exchange (ETDEWEB)

Wang, Dongxu, E-mail: dongxu-wang@uiowa.edu; Dirksen, Blake; Hyer, Daniel E.; Buatti, John M.; Sheybani, Arshin; Dinges, Eric; Felderman, Nicole; TenNapel, Mindi; Bayouth, John E.; Flynn, Ryan T. [Department of Radiation Oncology, University of Iowa, Iowa City, Iowa 52242 (United States)

2014-12-15

Purpose: To determine the plan quality of proton spot scanning (SS) radiosurgery as a function of spot size (in-air sigma) in comparison to x-ray radiosurgery for treating peripheral brain lesions. Methods: Single-field optimized (SFO) proton SS plans with sigma ranging from 1 to 8 mm, cone-based x-ray radiosurgery (Cone), and x-ray volumetric modulated arc therapy (VMAT) plans were generated for 11 patients. Plans were evaluated using secondary cancer risk and brain necrosis normal tissue complication probability (NTCP). Results: For all patients, secondary cancer is a negligible risk compared to brain necrosis NTCP. Secondary cancer risk was lower in proton SS plans than in photon plans regardless of spot size (p = 0.001). Brain necrosis NTCP increased monotonically from an average of 2.34/100 (range 0.42/100–4.49/100) to 6.05/100 (range 1.38/100–11.6/100) as sigma increased from 1 to 8 mm, compared to the average of 6.01/100 (range 0.82/100–11.5/100) for Cone and 5.22/100 (range 1.37/100–8.00/100) for VMAT. An in-air sigma less than 4.3 mm was required for proton SS plans to reduce NTCP over photon techniques for the cohort of patients studied with statistical significance (p = 0.0186). Proton SS plans with in-air sigma larger than 7.1 mm had significantly greater brain necrosis NTCP than photon techniques (p = 0.0322). Conclusions: For treating peripheral brain lesions—where proton therapy would be expected to have the greatest depth-dose advantage over photon therapy—the lateral penumbra strongly impacts the SS plan quality relative to photon techniques: proton beamlet sigma at patient surface must be small (<7.1 mm for three-beam single-field optimized SS plans) in order to achieve comparable or smaller brain necrosis NTCP relative to photon radiosurgery techniques. Achieving such small in-air sigma values at low energy (<70 MeV) is a major technological challenge in commercially available proton therapy systems.

Impact of spot size on plan quality of spot scanning proton radiosurgery for peripheral brain lesions

International Nuclear Information System (INIS)

Wang, Dongxu; Dirksen, Blake; Hyer, Daniel E.; Buatti, John M.; Sheybani, Arshin; Dinges, Eric; Felderman, Nicole; TenNapel, Mindi; Bayouth, John E.; Flynn, Ryan T.

2014-01-01

Purpose: To determine the plan quality of proton spot scanning (SS) radiosurgery as a function of spot size (in-air sigma) in comparison to x-ray radiosurgery for treating peripheral brain lesions. Methods: Single-field optimized (SFO) proton SS plans with sigma ranging from 1 to 8 mm, cone-based x-ray radiosurgery (Cone), and x-ray volumetric modulated arc therapy (VMAT) plans were generated for 11 patients. Plans were evaluated using secondary cancer risk and brain necrosis normal tissue complication probability (NTCP). Results: For all patients, secondary cancer is a negligible risk compared to brain necrosis NTCP. Secondary cancer risk was lower in proton SS plans than in photon plans regardless of spot size (p = 0.001). Brain necrosis NTCP increased monotonically from an average of 2.34/100 (range 0.42/100–4.49/100) to 6.05/100 (range 1.38/100–11.6/100) as sigma increased from 1 to 8 mm, compared to the average of 6.01/100 (range 0.82/100–11.5/100) for Cone and 5.22/100 (range 1.37/100–8.00/100) for VMAT. An in-air sigma less than 4.3 mm was required for proton SS plans to reduce NTCP over photon techniques for the cohort of patients studied with statistical significance (p = 0.0186). Proton SS plans with in-air sigma larger than 7.1 mm had significantly greater brain necrosis NTCP than photon techniques (p = 0.0322). Conclusions: For treating peripheral brain lesions—where proton therapy would be expected to have the greatest depth-dose advantage over photon therapy—the lateral penumbra strongly impacts the SS plan quality relative to photon techniques: proton beamlet sigma at patient surface must be small (<7.1 mm for three-beam single-field optimized SS plans) in order to achieve comparable or smaller brain necrosis NTCP relative to photon radiosurgery techniques. Achieving such small in-air sigma values at low energy (<70 MeV) is a major technological challenge in commercially available proton therapy systems

Costs of reproduction can explain the correlated evolution of semelparity and egg size: theory and a test with salmon.

Science.gov (United States)

Kindsvater, Holly K; Braun, Douglas C; Otto, Sarah P; Reynolds, John D

2016-06-01

Species' life history traits, including maturation age, number of reproductive bouts, offspring size and number, reflect adaptations to diverse biotic and abiotic selection pressures. A striking example of divergent life histories is the evolution of either iteroparity (breeding multiple times) or semelparity (breed once and die). We analysed published data on salmonid fishes and found that semelparous species produce larger eggs, that egg size and number increase with salmonid body size among populations and species and that migratory behaviour and parity interact. We developed three hypotheses that might explain the patterns in our data and evaluated them in a stage-structured modelling framework accounting for different growth and survival scenarios. Our models predict the observation of small eggs in iteroparous species when egg size is costly to maternal survival or egg number is constrained. By exploring trait co-variation in salmonids, we generate new hypotheses for the evolution of trade-offs among life history traits. © 2016 John Wiley & Sons Ltd/CNRS.

Genome Sequences of Marine Shrimp Exopalaemon carinicauda Holthuis Provide Insights into Genome Size Evolution of Caridea.

Science.gov (United States)

Yuan, Jianbo; Gao, Yi; Zhang, Xiaojun; Wei, Jiankai; Liu, Chengzhang; Li, Fuhua; Xiang, Jianhai

2017-07-05

Crustacea, particularly Decapoda, contains many economically important species, such as shrimps and crabs. Crustaceans exhibit enormous (nearly 500-fold) variability in genome size. However, limited genome resources are available for investigating these species. Exopalaemon carinicauda Holthuis, an economical caridean shrimp, is a potential ideal experimental animal for research on crustaceans. In this study, we performed low-coverage sequencing and de novo assembly of the E. carinicauda genome. The assembly covers more than 95% of coding regions. E. carinicauda possesses a large complex genome (5.73 Gb), with size twice higher than those of many decapod shrimps. As such, comparative genomic analyses were implied to investigate factors affecting genome size evolution of decapods. However, clues associated with genome duplication were not identified, and few horizontally transferred sequences were detected. Ultimately, the burst of transposable elements, especially retrotransposons, was determined as the major factor influencing genome expansion. A total of 2 Gb repeats were identified, and RTE-BovB, Jockey, Gypsy, and DIRS were the four major retrotransposons that significantly expanded. Both recent (Jockey and Gypsy) and ancestral (DIRS) originated retrotransposons responsible for the genome evolution. The E. carinicauda genome also exhibited potential for the genomic and experimental research of shrimps.

Aggregate size and structure determination of nanomaterials in physiological media: importance of dynamic evolution

Science.gov (United States)

Afrooz, A. R. M. Nabiul; Hussain, Saber M.; Saleh, Navid B.

2014-12-01

Most in vitro nanotoxicological assays are performed after 24 h exposure. However, in determining size and shape effect of nanoparticles in toxicity assays, initial characterization data are generally used to describe experimental outcome. The dynamic size and structure of aggregates are typically ignored in these studies. This brief communication reports dynamic evolution of aggregation characteristics of gold nanoparticles. The study finds that gradual increase in aggregate size of gold nanospheres (AuNS) occurs up to 6 h duration; beyond this time period, the aggregation process deviates from gradual to a more abrupt behavior as large networks are formed. Results of the study also show that aggregated clusters possess unique structural conformation depending on nominal diameter of the nanoparticles. The differences in fractal dimensions of the AuNS samples likely occurred due to geometric differences, causing larger packing propensities for smaller sized particles. Both such observations can have profound influence on dosimetry for in vitro nanotoxicity analyses.

Aggregate size and structure determination of nanomaterials in physiological media: importance of dynamic evolution

International Nuclear Information System (INIS)

Afrooz, A. R. M. Nabiul; Hussain, Saber M.; Saleh, Navid B.

2014-01-01

Most in vitro nanotoxicological assays are performed after 24 h exposure. However, in determining size and shape effect of nanoparticles in toxicity assays, initial characterization data are generally used to describe experimental outcome. The dynamic size and structure of aggregates are typically ignored in these studies. This brief communication reports dynamic evolution of aggregation characteristics of gold nanoparticles. The study finds that gradual increase in aggregate size of gold nanospheres (AuNS) occurs up to 6 h duration; beyond this time period, the aggregation process deviates from gradual to a more abrupt behavior as large networks are formed. Results of the study also show that aggregated clusters possess unique structural conformation depending on nominal diameter of the nanoparticles. The differences in fractal dimensions of the AuNS samples likely occurred due to geometric differences, causing larger packing propensities for smaller sized particles. Both such observations can have profound influence on dosimetry for in vitro nanotoxicity analyses.Graphical Abstract

Aggregate size and structure determination of nanomaterials in physiological media: importance of dynamic evolution

Energy Technology Data Exchange (ETDEWEB)

Afrooz, A. R. M. Nabiul [The University of Texas, Civil, Architectural and Environmental Engineering (United States); Hussain, Saber M. [Wright-Patterson AFB, Human Effectiveness Directorate, 711th Human Performance Wing, Air Force Research Laboratory (United States); Saleh, Navid B., E-mail: navid.saleh@utexas.edu [The University of Texas, Civil, Architectural and Environmental Engineering (United States)

2014-12-15

Most in vitro nanotoxicological assays are performed after 24 h exposure. However, in determining size and shape effect of nanoparticles in toxicity assays, initial characterization data are generally used to describe experimental outcome. The dynamic size and structure of aggregates are typically ignored in these studies. This brief communication reports dynamic evolution of aggregation characteristics of gold nanoparticles. The study finds that gradual increase in aggregate size of gold nanospheres (AuNS) occurs up to 6 h duration; beyond this time period, the aggregation process deviates from gradual to a more abrupt behavior as large networks are formed. Results of the study also show that aggregated clusters possess unique structural conformation depending on nominal diameter of the nanoparticles. The differences in fractal dimensions of the AuNS samples likely occurred due to geometric differences, causing larger packing propensities for smaller sized particles. Both such observations can have profound influence on dosimetry for in vitro nanotoxicity analyses.Graphical Abstract.

Population Size and the Rate of Language Evolution: A Test Across Indo-European, Austronesian, and Bantu Languages

Science.gov (United States)

Greenhill, Simon J.; Hua, Xia; Welsh, Caela F.; Schneemann, Hilde; Bromham, Lindell

2018-01-01

What role does speaker population size play in shaping rates of language evolution? There has been little consensus on the expected relationship between rates and patterns of language change and speaker population size, with some predicting faster rates of change in smaller populations, and others expecting greater change in larger populations. The growth of comparative databases has allowed population size effects to be investigated across a wide range of language groups, with mixed results. One recent study of a group of Polynesian languages revealed greater rates of word gain in larger populations and greater rates of word loss in smaller populations. However, that test was restricted to 20 closely related languages from small Oceanic islands. Here, we test if this pattern is a general feature of language evolution across a larger and more diverse sample of languages from both continental and island populations. We analyzed comparative language data for 153 pairs of closely-related sister languages from three of the world's largest language families: Austronesian, Indo-European, and Niger-Congo. We find some evidence that rates of word loss are significantly greater in smaller languages for the Indo-European comparisons, but we find no significant patterns in the other two language families. These results suggest either that the influence of population size on rates and patterns of language evolution is not universal, or that it is sufficiently weak that it may be overwhelmed by other influences in some cases. Further investigation, for a greater number of language comparisons and a wider range of language features, may determine which of these explanations holds true. PMID:29755387

Microwave assisted synthesis of CdS nanoparticles and their size evolution

International Nuclear Information System (INIS)

Lopez, I. A.; Vazquez, A.; Gomez, I.

2013-01-01

The study of the size evolution of CdS nanoparticles in aqueous dispersion is presented in this paper. The sodium citrate was employed as stabilizer of CdS nanoparticles synthesized by microwave assisted synthesis. Analysis of this study was carried out by UV-Vis spectrophotometry, by comparison of the band gap energy using theoretical and empirical models. Results obtained show that the synthesis conditions produce CdS nanoparticles with diameters below of 6 nm, which remains stabilized by at least 14 days. These characteristics were confirmed by transmission electron microscopy. The X-ray diffraction pattern confirms cubic phase of the CdS nanoparticles. (Author)

Microwave assisted synthesis of CdS nanoparticles and their size evolution

Energy Technology Data Exchange (ETDEWEB)

Lopez, I. A.; Vazquez, A.; Gomez, I., E-mail: idaliagomezmx@yahoo.com.mx [Universidad Autonoma de Nuevo Leon, Facultad de Ciencias Quimicas, Laboratorio de Materiales I, Av. Universidad, Cd. Universitaria, 66451 San Nicolas de los Garza, Nuevo Leon (Mexico)

2013-05-01

The study of the size evolution of CdS nanoparticles in aqueous dispersion is presented in this paper. The sodium citrate was employed as stabilizer of CdS nanoparticles synthesized by microwave assisted synthesis. Analysis of this study was carried out by UV-Vis spectrophotometry, by comparison of the band gap energy using theoretical and empirical models. Results obtained show that the synthesis conditions produce CdS nanoparticles with diameters below of 6 nm, which remains stabilized by at least 14 days. These characteristics were confirmed by transmission electron microscopy. The X-ray diffraction pattern confirms cubic phase of the CdS nanoparticles. (Author)

Inferring the photometric and size evolution of galaxies from image simulations. I. Method

Science.gov (United States)

Carassou, Sébastien; de Lapparent, Valérie; Bertin, Emmanuel; Le Borgne, Damien

2017-09-01

Context. Current constraints on models of galaxy evolution rely on morphometric catalogs extracted from multi-band photometric surveys. However, these catalogs are altered by selection effects that are difficult to model, that correlate in non trivial ways, and that can lead to contradictory predictions if not taken into account carefully. Aims: To address this issue, we have developed a new approach combining parametric Bayesian indirect likelihood (pBIL) techniques and empirical modeling with realistic image simulations that reproduce a large fraction of these selection effects. This allows us to perform a direct comparison between observed and simulated images and to infer robust constraints on model parameters. Methods: We use a semi-empirical forward model to generate a distribution of mock galaxies from a set of physical parameters. These galaxies are passed through an image simulator reproducing the instrumental characteristics of any survey and are then extracted in the same way as the observed data. The discrepancy between the simulated and observed data is quantified, and minimized with a custom sampling process based on adaptive Markov chain Monte Carlo methods. Results: Using synthetic data matching most of the properties of a Canada-France-Hawaii Telescope Legacy Survey Deep field, we demonstrate the robustness and internal consistency of our approach by inferring the parameters governing the size and luminosity functions and their evolutions for different realistic populations of galaxies. We also compare the results of our approach with those obtained from the classical spectral energy distribution fitting and photometric redshift approach. Conclusions: Our pipeline infers efficiently the luminosity and size distribution and evolution parameters with a very limited number of observables (three photometric bands). When compared to SED fitting based on the same set of observables, our method yields results that are more accurate and free from

Left brain, right brain: facts and fantasies.

Directory of Open Access Journals (Sweden)

Michael C Corballis

2014-01-01

Full Text Available Handedness and brain asymmetry are widely regarded as unique to humans, and associated with complementary functions such as a left-brain specialization for language and logic and a right-brain specialization for creativity and intuition. In fact, asymmetries are widespread among animals, and support the gradual evolution of asymmetrical functions such as language and tool use. Handedness and brain asymmetry are inborn and under partial genetic control, although the gene or genes responsible are not well established. Cognitive and emotional difficulties are sometimes associated with departures from the "norm" of right-handedness and left-brain language dominance, more often with the absence of these asymmetries than their reversal.

Left brain, right brain: facts and fantasies.

Science.gov (United States)

Corballis, Michael C

2014-01-01

Handedness and brain asymmetry are widely regarded as unique to humans, and associated with complementary functions such as a left-brain specialization for language and logic and a right-brain specialization for creativity and intuition. In fact, asymmetries are widespread among animals, and support the gradual evolution of asymmetrical functions such as language and tool use. Handedness and brain asymmetry are inborn and under partial genetic control, although the gene or genes responsible are not well established. Cognitive and emotional difficulties are sometimes associated with departures from the "norm" of right-handedness and left-brain language dominance, more often with the absence of these asymmetries than their reversal.

Brain vs behavior: an effect size comparison of neuroimaging and cognitive studies of genetic risk for schizophrenia.

LENUS (Irish Health Repository)

Rose, Emma Jane

2013-05-01

Genetic variants associated with increased risk for schizophrenia (SZ) are hypothesized to be more penetrant at the level of brain structure and function than at the level of behavior. However, to date the relative sensitivity of imaging vs cognitive measures of these variants has not been quantified. We considered effect sizes associated with cognitive and imaging studies of 9 robust SZ risk genes (DAOA, DISC1, DTNBP1, NRG1, RGS4, NRGN, CACNA1C, TCF4, and ZNF804A) published between January 2005-November 2011. Summary data was used to calculate estimates of effect size for each significant finding. The mean effect size for each study was categorized as small, medium, or large and the relative frequency of each category was compared between modalities and across genes. Random effects meta-analysis was used to consider the impact of experimental methodology on effect size. Imaging studies reported mostly medium or large effects, whereas cognitive investigations commonly reported small effects. Meta-analysis confirmed that imaging studies were associated with larger effects. Effect size estimates were negatively correlated with sample size but did not differ as a function of gene nor imaging modality. These observations support the notion that SZ risk variants show larger effects, and hence greater penetrance, when characterized using indices of brain structure and function than when indexed by cognitive measures. However, it remains to be established whether this holds true for individual risk variants, imaging modalities, or cognitive functions, and how such effects may be mediated by a relationship with sample size and other aspects of experimental variability.

Positive correlation between occlusion rate and nidus size of proton beam treated brain arteriovenous malformations (AVMs)

DEFF Research Database (Denmark)

Blomquist, Erik; Ronne Engström, Elisabeth; Borota, Ljubisa

2016-01-01

symptoms, clinical course, the size of AVM nidus and rate of occlusion was collected. Outcome parameters were the occlusion of the AVM, clinical outcome and side effects.Results. The rate of total occlusion was overall 68%. For target volume 0-2cm3 it was 77%, for 3-10 cm3 80%, for 11-15 cm3 50% and for 16...... of these had no effect and the other only partial occlusion from proton beams. Two thirds of those presenting with seizures reported an improved seizure situation after treatment.Conclusion. Our observations agree with earlier results and show that proton beam irradiation is a treatment alternative for brain......Background. Proton beam radiotherapy of arteriovenous malformations (AVM) in the brain has been performed in Uppsala since 1991. An earlier study based on the first 26 patients concluded that proton beam can be used for treating large and medium sized AVMs that were considered difficult to treat...

Phylogeny, rate variation, and genome size evolution of Pelargonium (Geraniaceae).

Science.gov (United States)

Weng, Mao-Lun; Ruhlman, Tracey A; Gibby, Mary; Jansen, Robert K

2012-09-01

The phylogeny of 58 Pelargonium species was estimated using five plastid markers (rbcL, matK, ndhF, rpoC1, trnL-F) and one mitochondrial gene (nad5). The results confirmed the monophyly of three major clades and four subclades within Pelargonium but also indicate the need to revise some sectional classifications. This phylogeny was used to examine karyotype evolution in the genus: plotting chromosome sizes, numbers and 2C-values indicates that genome size is significantly correlated with chromosome size but not number. Accelerated rates of nucleotide substitution have been previously detected in both plastid and mitochondrial genes in Pelargonium, but sparse taxon sampling did not enable identification of the phylogenetic distribution of these elevated rates. Using the multigene phylogeny as a constraint, we investigated lineage- and locus-specific heterogeneity of substitution rates in Pelargonium for an expanded number of taxa and demonstrated that both plastid and mitochondrial genes have had accelerated substitution rates but with markedly disparate patterns. In the plastid, the exons of rpoC1 have significantly accelerated substitution rates compared to its intron and the acceleration was mainly due to nonsynonymous substitutions. In contrast, the mitochondrial gene, nad5, experienced substantial acceleration of synonymous substitution rates in three internal branches of Pelargonium, but this acceleration ceased in all terminal branches. Several lineages also have dN/dS ratios significantly greater than one for rpoC1, indicating that positive selection is acting on this gene, whereas the accelerated synonymous substitutions in the mitochondrial gene are the result of elevated mutation rates. Published by Elsevier Inc.

Mosaic Evolution of Brainstem Motor Nuclei in Catarrhine Primates

Directory of Open Access Journals (Sweden)

Seth D. Dobson

2011-01-01

Full Text Available Facial motor nucleus volume coevolves with both social group size and primary visual cortex volume in catarrhine primates as part of a specialized neuroethological system for communication using facial expressions. Here, we examine whether facial nucleus volume also coevolves with functionally unrelated brainstem motor nuclei (trigeminal motor and hypoglossal due to developmental constraints. Using phylogenetically informed multiple regression analyses of previously published brain component data, we demonstrate that facial nucleus volume is not correlated with the volume of other motor nuclei after controlling for medulla volume. Our results show that brainstem motor nuclei can evolve independently of other developmentally linked structures in association with specific behavioral ecological conditions. This finding provides additional support for the mosaic view of brain evolution.

Big Cat Coalitions: A Comparative Analysis of Regional Brain Volumes in Felidae.

Science.gov (United States)

Sakai, Sharleen T; Arsznov, Bradley M; Hristova, Ani E; Yoon, Elise J; Lundrigan, Barbara L

2016-01-01

Broad-based species comparisons across mammalian orders suggest a number of factors that might influence the evolution of large brains. However, the relationship between these factors and total and regional brain size remains unclear. This study investigated the relationship between relative brain size and regional brain volumes and sociality in 13 felid species in hopes of revealing relationships that are not detected in more inclusive comparative studies. In addition, a more detailed analysis was conducted of four focal species: lions ( Panthera leo ), leopards ( Panthera pardus ), cougars ( Puma concolor ), and cheetahs ( Acinonyx jubatus ). These species differ markedly in sociality and behavioral flexibility, factors hypothesized to contribute to increased relative brain size and/or frontal cortex size. Lions are the only truly social species, living in prides. Although cheetahs are largely solitary, males often form small groups. Both leopards and cougars are solitary. Of the four species, leopards exhibit the most behavioral flexibility, readily adapting to changing circumstances. Regional brain volumes were analyzed using computed tomography. Skulls ( n = 75) were scanned to create three-dimensional virtual endocasts, and regional brain volumes were measured using either sulcal or bony landmarks obtained from the endocasts or skulls. Phylogenetic least squares regression analyses found that sociality does not correspond with larger relative brain size in these species. However, the sociality/solitary variable significantly predicted anterior cerebrum (AC) volume, a region that includes frontal cortex. This latter finding is despite the fact that the two social species in our sample, lions and cheetahs, possess the largest and smallest relative AC volumes, respectively. Additionally, an ANOVA comparing regional brain volumes in four focal species revealed that lions and leopards, while not significantly different from one another, have relatively larger AC

Big Cat Coalitions: A comparative analysis of regional brain volumes in Felidae

Directory of Open Access Journals (Sweden)

Sharleen T Sakai

2016-10-01

Full Text Available Broad-based species comparisons across mammalian orders suggest a number of factors that might influence the evolution of large brains. However, the relationship between these factors and total and regional brain size remains unclear. This study investigated the relationship between relative brain size and regional brain volumes and sociality in 13 felid species in hopes of revealing relationships that are not detected in more inclusive comparative studies. In addition, a more detailed analysis was conducted of 4 focal species: lions (Panthera leo, leopards (Panthera pardus, cougars (Puma concolor, and cheetahs (Acinonyx jubatus. These species differ markedly in sociality and behavioral flexibility, factors hypothesized to contribute to increased relative brain size and/or frontal cortex size. Lions are the only truly social species, living in prides. Although cheetahs are largely solitary, males often form small groups. Both leopards and cougars are solitary. Of the four species, leopards exhibit the most behavioral flexibility, readily adapting to changing circumstances. Regional brain volumes were analyzed using computed tomography (CT. Skulls (n=75 were scanned to create three-dimensional virtual endocasts, and regional brain volumes were measured using either sulcal or bony landmarks obtained from the endocasts or skulls. Phylogenetic least squares (PGLS regression analyses found that sociality does not correspond with larger relative brain size in these species. However, the sociality/solitary variable significantly predicted anterior cerebrum (AC volume, a region that includes frontal cortex. This latter finding is despite the fact that the two social species in our sample, lions and cheetahs, possess the largest and smallest relative AC volumes, respectively. Additionally, an ANOVA comparing regional brain volumes in 4 focal species revealed that lions and leopards, while not significantly different from one another, have relatively

Evolution, immunity and the emergence of brain superautoantigens [version 1; referees: 2 approved

Directory of Open Access Journals (Sweden)

Serge Nataf

2017-02-01

Full Text Available While some autoimmune disorders remain extremely rare, others largely predominate the epidemiology of human autoimmunity. Notably, these include psoriasis, diabetes, vitiligo, thyroiditis, rheumatoid arthritis and multiple sclerosis. Thus, despite the quasi-infinite number of "self" antigens that could theoretically trigger autoimmune responses, only a limited set of antigens, referred here as superautoantigens, induce pathogenic adaptive responses. Several lines of evidence reviewed in this paper indicate that, irrespective of the targeted organ (e.g. thyroid, pancreas, joints, brain or skin, a significant proportion of superautoantigens are highly expressed in the synaptic compartment of the central nervous system (CNS. Such an observation applies notably for GAD65, AchR, ribonucleoproteins, heat shock proteins, collagen IV, laminin, tyrosine hydroxylase and the acetylcholinesterase domain of thyroglobulin. It is also argued that cognitive alterations have been described in a number of autoimmune disorders, including psoriasis, rheumatoid arthritis, lupus, Crohn's disease and autoimmune thyroiditis. Finally, the present paper points out that a great majority of the "incidental" autoimmune conditions notably triggered by neoplasms, vaccinations or microbial infections are targeting the synaptic or myelin compartments. On this basis, the concept of an immunological homunculus, proposed by Irun Cohen more than 25 years ago, is extended here in a model where physiological autoimmunity against brain superautoantigens confers both: i a crucial evolutionary-determined advantage via cognition-promoting autoimmunity; and ii a major evolutionary-determined vulnerability, leading to the emergence of autoimmune disorders in Homo sapiens. Moreover, in this theoretical framework, the so called co-development/co-evolution model, both the development (at the scale of an individual and evolution (at the scale of species of the antibody and T-cell repertoires

Variations and asymmetries in regional brain surface in the genus Homo.

Science.gov (United States)

Balzeau, Antoine; Holloway, Ralph L; Grimaud-Hervé, Dominique

2012-06-01

Paleoneurology is an important field of research within human evolution studies. Variations in size and shape of an endocast help to differentiate among fossil hominin species whereas endocranial asymmetries are related to behavior and cognitive function. Here we analyse variations of the surface of the frontal, parieto-temporal and occipital lobes among different species of Homo, including 39 fossil hominins, ten fossil anatomically modern Homo sapiens and 100 endocasts of extant modern humans. We also test for the possible asymmetries of these features in a large sample of modern humans and observe individual particularities in the fossil specimens. This study contributes important new information about the brain evolution in the genus Homo. Our results show that the general pattern of surface asymmetry for the different regional brain surfaces in fossil species of Homo does not seem to be different from the pattern described in a large sample of anatomically modern H. sapiens, i.e., the right hemisphere has a larger surface than the left, as do the right frontal, the right parieto-temporal and the left occipital lobes compared with the contra-lateral side. It also appears that Asian Homo erectus specimens are discriminated from all other samples of Homo, including African and Georgian specimens that are also sometimes included in that taxon. The Asian fossils show a significantly smaller relative size of the parietal and temporal lobes. Neandertals and anatomically modern H. sapiens, who share the largest endocranial volume of all hominins, show differences when considering the relative contribution of the frontal, parieto-temporal and occipital lobes. These results illustrate an original variation in the pattern of brain organization in hominins independent of variations in total size. The globularization of the brain and the enlargement of the parietal lobes could be considered derived features observed uniquely in anatomically modern H. sapiens. Copyright

Early human speciation, brain expansion and dispersal influenced by African climate pulses.

Directory of Open Access Journals (Sweden)

Susanne Shultz

Full Text Available Early human evolution is characterised by pulsed speciation and dispersal events that cannot be explained fully by global or continental paleoclimate records. We propose that the collated record of ephemeral East African Rift System (EARS lakes could be a proxy for the regional paleoclimate conditions experienced by early hominins. Here we show that the presence of these lakes is associated with low levels of dust deposition in both West African and Mediterranean records, but is not associated with long-term global cooling and aridification of East Africa. Hominin expansion and diversification seem to be associated with climate pulses characterized by the precession-forced appearance and disappearance of deep EARS lakes. The most profound period for hominin evolution occurs at about 1.9 Ma; with the highest recorded diversity of hominin species, the appearance of Homo (sensu stricto and major dispersal events out of East Africa into Eurasia. During this period, ephemeral deep-freshwater lakes appeared along the whole length of the EARS, fundamentally changing the local environment. The relationship between the local environment and hominin brain expansion is less clear. The major step-wise expansion in brain size around 1.9 Ma when Homo appeared was coeval with the occurrence of ephemeral deep lakes. Subsequent incremental increases in brain size are associated with dry periods with few if any lakes. Plio-Pleistocene East African climate pulses as evinced by the paleo-lake records seem, therefore, fundamental to hominin speciation, encephalisation and migration.

Early human speciation, brain expansion and dispersal influenced by African climate pulses.

Science.gov (United States)

Shultz, Susanne; Maslin, Mark

2013-01-01

Early human evolution is characterised by pulsed speciation and dispersal events that cannot be explained fully by global or continental paleoclimate records. We propose that the collated record of ephemeral East African Rift System (EARS) lakes could be a proxy for the regional paleoclimate conditions experienced by early hominins. Here we show that the presence of these lakes is associated with low levels of dust deposition in both West African and Mediterranean records, but is not associated with long-term global cooling and aridification of East Africa. Hominin expansion and diversification seem to be associated with climate pulses characterized by the precession-forced appearance and disappearance of deep EARS lakes. The most profound period for hominin evolution occurs at about 1.9 Ma; with the highest recorded diversity of hominin species, the appearance of Homo (sensu stricto) and major dispersal events out of East Africa into Eurasia. During this period, ephemeral deep-freshwater lakes appeared along the whole length of the EARS, fundamentally changing the local environment. The relationship between the local environment and hominin brain expansion is less clear. The major step-wise expansion in brain size around 1.9 Ma when Homo appeared was coeval with the occurrence of ephemeral deep lakes. Subsequent incremental increases in brain size are associated with dry periods with few if any lakes. Plio-Pleistocene East African climate pulses as evinced by the paleo-lake records seem, therefore, fundamental to hominin speciation, encephalisation and migration.

Brain regions implicated in inhibitory control and appetite regulation are activated in response to food portion size and energy density in children

NARCIS (Netherlands)

English, L.K.; Fearnbach, S.N.; Lasschuijt, M.; Schlegel, A.; Anderson, K.; Harris, S.; Fisher, J.O.; Savage, J.S.; Rolls, B.J.; Keller, K.L.

2016-01-01

Objective:Large portions of energy-dense foods drive energy intake but the brain mechanisms underlying this effect are not clear. Our main objective was to investigate brain function in response to food images varied by portion size (PS) and energy density (ED) in children using functional

Mitochondrial genome evolution in Alismatales: Size reduction and extensive loss of ribosomal protein genes

DEFF Research Database (Denmark)

Petersen, Gitte; Cuenca, Argelia; Zervas, Athanasios

2017-01-01

The order Alismatales is a hotspot for evolution of plant mitochondrial genomes characterized by remarkable differences in genome size, substitution rates, RNA editing, retrotranscription, gene loss and intron loss. Here we have sequenced the complete mitogenomes of Zostera marina and Stratiotes...... aloides, which together with previously sequenced mitogenomes from Butomus and Spirodela, provide new evolutionary evidence of genome size reduction, gene loss and transfer to the nucleus. The Zostera mitogenome includes a large portion of DNA transferred from the plastome, yet it is the smallest known...... mitogenome from a non-parasitic plant. Using a broad sample of the Alismatales, the evolutionary history of ribosomal protein gene loss is analyzed. In Zostera almost all ribosomal protein genes are lost from the mitogenome, but only some can be found in the nucleus....

Evolution of science I: Evolution of Mind

OpenAIRE

Vahia, M N

2016-01-01

The central nervous system and particularly the brain was designed to control the life cycle of a living being. With increasing size and sophistication, in mammals, the brain became capable of exercising significant control over life. In Homo Sapiens the brain became significantly powerful and capable of comprehension beyond survival needs with visualisation, formal thought and long term memory. Here we trace the rise of the powers of the brains of the Homo Sapiens and its capability of three...

Unusual developmental pattern of brain lateralization in young boys with autism spectrum disorder: Power analysis with child-sized magnetoencephalography.

Science.gov (United States)

Hiraishi, Hirotoshi; Kikuchi, Mitsuru; Yoshimura, Yuko; Kitagawa, Sachiko; Hasegawa, Chiaki; Munesue, Toshio; Takesaki, Natsumi; Ono, Yasuki; Takahashi, Tsutomu; Suzuki, Michio; Higashida, Haruhiro; Asada, Minoru; Minabe, Yoshio

2015-03-01

Autism spectrum disorder (ASD) is often described as comprising an unusual brain growth pattern and aberrant brain lateralization. Although it is important to study the pathophysiology of the developing ASD cortex, examples of physiological brain lateralization in young children with ASD have yet to be well examined. Thirty-eight boys with ASD (aged 3-7 years) and 38 typically developing (TD) boys (aged 3-8 years) concentrated on video programs and their brain activities were measured non-invasively. We employed a customized child-sized magnetoencephalography system in which the sensors were located as close to the brain as possible for optimal recording in young children. To produce a credible laterality index of the brain oscillations, we defined two clusters of sensors corresponding to the right and left hemispheres. We focused on the laterality index ([left - right]/[left+right]) of the relative power band in seven frequency bands. The TD group displayed significantly rightward lateralized brain oscillations in the theta-1 frequency bands compared to the ASD group. This is the first study to demonstrate unusual brain lateralization of brain oscillations measured by magnetoencephalography in young children with ASD. © 2014 The Authors. Psychiatry and Clinical Neurosciences © 2014 Japanese Society of Psychiatry and Neurology.

Four types of interference competition and their impacts on the ecology and evolution of size-structured populations and communities

DEFF Research Database (Denmark)

Zhang, Lai; Andersen, Ken Haste; Dieckmann, Ulf

2015-01-01

We investigate how four types of interference competition - which alternatively affect foraging, metabolism, survival, and reproduction - impact the ecology and evolution of size-structured populations. Even though all four types of interference competition reduce population biomass, interference...

Larger ATV engine size correlates with an increased rate of traumatic brain injury.

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Butts, C Caleb; Rostas, Jack W; Lee, Y L; Gonzalez, Richard P; Brevard, Sidney B; Frotan, M Amin; Ahmed, Naveed; Simmons, Jon D

2015-04-01

Since the introduction of all-terrain vehicles (ATV) to the United States in 1971, injuries and mortalities related to their use have increased significantly. Furthermore, these vehicles have become larger and more powerful. As there are no helmet requirements or limitations on engine-size in the State of Alabama, we hypothesised that larger engine size would correlate with an increased incidence of traumatic brain injury (TBI) in patients following an ATV crash. Patient and ATV data were prospectively collected on all ATV crashes presenting to a level one trauma centre from September 2010 to May 2013. Collected data included: demographics, age of driver, ATV engine size, presence of helmet, injuries, and outcomes. The data were grouped according to the ATV engine size in cubic centimetres (cc). For the purposes of this study, TBI was defined as any type of intracranial haemorrhage on the initial computed tomography scan. There were 61 patients identified during the study period. Two patients (3%) were wearing a helmet at the time of injury. Patients on an ATV with an engine size of 350 cc or greater had higher Injury Severity Scores (13.9 vs. 7.5, p ≤ 0.05) and an increased incidence of TBI (26% vs. 0%, p ≤ 0.05) when compared to patients on ATV's with an engine size less than 350 cc. Patients on an ATV with an engine size of 350 cc or greater were more likely to have a TBI. The use of a helmet was rarely present in this cohort. Legislative efforts to implement rider protection laws for ATVs are warranted. Copyright © 2014 Elsevier Ltd. All rights reserved.

Initial brain aging: heterogeneity of mitochondrial size is associated with decline in complex I-linked respiration in cortex and hippocampus.

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Thomsen, Kirsten; Yokota, Takashi; Hasan-Olive, Md Mahdi; Sherazi, Niloofar; Fakouri, Nima Borhan; Desler, Claus; Regnell, Christine Elisabeth; Larsen, Steen; Rasmussen, Lene Juel; Dela, Flemming; Bergersen, Linda Hildegard; Lauritzen, Martin

2018-01-01

Brain aging is accompanied by declining mitochondrial respiration. We hypothesized that mitochondrial morphology and dynamics would reflect this decline. Using hippocampus and frontal cortex of a segmental progeroid mouse model lacking Cockayne syndrome protein B (CSB m/m ) and C57Bl/6 (WT) controls and comparing young (2-5 months) to middle-aged mice (13-14 months), we found that complex I-linked state 3 respiration (CI) was reduced at middle age in CSB m/m hippocampus, but not in CSB m/m cortex or WT brain. In hippocampus of both genotypes, mitochondrial size heterogeneity increased with age. Notably, an inverse correlation between heterogeneity and CI was found in both genotypes, indicating that heterogeneity reflects mitochondrial dysfunction. The ratio between fission and fusion gene expression reflected age-related alterations in mitochondrial morphology but not heterogeneity. Mitochondrial DNA content was lower, and hypoxia-induced factor 1α mRNA was greater at both ages in CSB m/m compared to WT brain. Our findings show that decreased CI and increased mitochondrial size heterogeneity are highly associated and point to declining mitochondrial quality control as an initial event in brain aging. Copyright © 2017 Elsevier Inc. All rights reserved.

Evolution of floral display in Eichhornia paniculata (Pontederiaceae): direct and correlated responses to selection on flower size and number.

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Worley, A C; Barrett, S C

2000-10-01

Trade-offs between flower size and number seem likely to influence the evolution of floral display and are an important assumption of several theoretical models. We assessed floral trade-offs by imposing two generations of selection on flower size and number in a greenhouse population of bee-pollinated Eichhornia paniculata. We established a control line and two replicate selection lines of 100 plants each for large flowers (S+), small flowers (S-), and many flowers per inflorescence (N+). We compared realized heritabilities and genetic correlations with estimates based on restricted-maximum-likelihood (REML) analysis of pedigrees. Responses to selection confirmed REML heritability estimates (flower size, h2 = 0.48; daily flower number, h2 = 0.10; total flower number, h2 = 0.23). Differences in nectar, pollen, and ovule production between S+ and S- lines supported an overall divergence in investment per flower. Both realized and REML estimates of the genetic correlation between daily and total flower number were r = 1.0. However, correlated responses to selection were inconsistent in their support of a trade-off. In both S- lines, correlated increases in flower number indicated a genetic correlation of r = -0.6 between flower size and number. In contrast, correlated responses in N+ and S+ lines were not significant, although flower size decreased in one N+ line. In addition, REML estimates of genetic correlations between flower size and number were positive, and did not differ from zero when variation in leaf area and age at first flowering were taken into account. These results likely reflect the combined effects of variation in genes controlling the resources available for flowering and genes with opposing effects on flower size and number. Our results suggest that the short-term evolution of floral display is not necessarily constrained by trade-offs between flower size and number, as is often assumed.

Brain Aneurysm

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A brain aneurysm is an abnormal bulge or "ballooning" in the wall of an artery in the brain. They are sometimes called berry aneurysms because they ... often the size of a small berry. Most brain aneurysms produce no symptoms until they become large, ...

Meta-analysis of associations between human brain volume and intelligence differences: How strong are they and what do they mean?

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Pietschnig, Jakob; Penke, Lars; Wicherts, Jelte M; Zeiler, Michael; Voracek, Martin

2015-10-01

Positive associations between human intelligence and brain size have been suspected for more than 150 years. Nowadays, modern non-invasive measures of in vivo brain volume (Magnetic Resonance Imaging) make it possible to reliably assess associations with IQ. By means of a systematic review of published studies and unpublished results obtained by personal communications with researchers, we identified 88 studies examining effect sizes of 148 healthy and clinical mixed-sex samples (>8000 individuals). Our results showed significant positive associations of brain volume and IQ (r=.24, R(2)=.06) that generalize over age (children vs. adults), IQ domain (full-scale, performance, and verbal IQ), and sex. Application of a number of methods for detection of publication bias indicates that strong and positive correlation coefficients have been reported frequently in the literature whilst small and non-significant associations appear to have been often omitted from reports. We show that the strength of the positive association of brain volume and IQ has been overestimated in the literature, but remains robust even when accounting for different types of dissemination bias, although reported effects have been declining over time. While it is tempting to interpret this association in the context of human cognitive evolution and species differences in brain size and cognitive ability, we show that it is not warranted to interpret brain size as an isomorphic proxy of human intelligence differences. Copyright © 2015 Elsevier Ltd. All rights reserved.

A general model for the scaling of offspring size and adult size.

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Falster, Daniel S; Moles, Angela T; Westoby, Mark

2008-09-01

Understanding evolutionary coordination among different life-history traits is a key challenge for ecology and evolution. Here we develop a general quantitative model predicting how offspring size should scale with adult size by combining a simple model for life-history evolution with a frequency-dependent survivorship model. The key innovation is that larger offspring are afforded three different advantages during ontogeny: higher survivorship per time, a shortened juvenile phase, and advantage during size-competitive growth. In this model, it turns out that size-asymmetric advantage during competition is the factor driving evolution toward larger offspring sizes. For simplified and limiting cases, the model is shown to produce the same predictions as the previously existing theory on which it is founded. The explicit treatment of different survival advantages has biologically important new effects, mainly through an interaction between total maternal investment in reproduction and the duration of competitive growth. This goes on to explain alternative allometries between log offspring size and log adult size, as observed in mammals (slope = 0.95) and plants (slope = 0.54). Further, it suggests how these differences relate quantitatively to specific biological processes during recruitment. In these ways, the model generalizes across previous theory and provides explanations for some differences between major taxa.

Morphological and pathological evolution of the brain microcirculation in aging and Alzheimer's disease.

Directory of Open Access Journals (Sweden)

Jesse M Hunter

Full Text Available Key pathological hallmarks of Alzheimer's disease (AD, including amyloid plaques, cerebral amyloid angiopathy (CAA and neurofibrillary tangles do not completely account for cognitive impairment, therefore other factors such as cardiovascular and cerebrovascular pathologies, may contribute to AD. In order to elucidate the microvascular changes that contribute to aging and disease, direct neuropathological staining and immunohistochemistry, were used to quantify the structural integrity of the microvasculature and its innervation in three oldest-old cohorts: 1 nonagenarians with AD and a high amyloid plaque load; 2 nonagenarians with no dementia and a high amyloid plaque load; 3 nonagenarians without dementia or amyloid plaques. In addition, a non-demented (ND group (average age 71 years with no amyloid plaques was included for comparison. While gray matter thickness and overall brain mass were reduced in AD compared to ND control groups, overall capillary density was not different. However, degenerated string capillaries were elevated in AD, potentially suggesting greater microvascular "dysfunction" compared to ND groups. Intriguingly, apolipoprotein ε4 carriers had significantly higher string vessel counts relative to non-ε4 carriers. Taken together, these data suggest a concomitant loss of functional capillaries and brain volume in AD subjects. We also demonstrated a trend of decreasing vesicular acetylcholine transporter staining, a marker of cortical cholinergic afferents that contribute to arteriolar vasoregulation, in AD compared to ND control groups, suggesting impaired control of vasodilation in AD subjects. In addition, tyrosine hydroxylase, a marker of noradrenergic vascular innervation, was reduced which may also contribute to a loss of control of vasoconstriction. The data highlight the importance of the brain microcirculation in the pathogenesis and evolution of AD.

No evidence of trade-offs in the evolution of sperm numbers and sperm size in mammals.

Science.gov (United States)

Tourmente, M; Delbarco Trillo, J; Roldan, E R S

2015-10-01

Post-copulatory sexual selection, in the form sperm competition, has influenced the evolution of several male reproductive traits. However, theory predicts that sperm competition would lead to trade-offs between numbers and size of spermatozoa because increased costs per cell would result in a reduction of sperm number if both traits share the same energetic budget. Theoretical models have proposed that, in large animals, increased sperm size would have minimal fitness advantage compared with increased sperm numbers. Thus, sperm numbers would evolve more rapidly than sperm size under sperm competition pressure. We tested in mammals whether sperm competition maximizes sperm numbers and size, and whether there is a trade-off between these traits. Our results showed that sperm competition maximizes sperm numbers in eutherian and metatherian mammals. There was no evidence of a trade-off between sperm numbers and sperm size in any of the two mammalian clades as we did not observe any significant relationship between sperm numbers and sperm size once the effect of sperm competition was taken into account. Maximization of both numbers and size in mammals may occur because each trait is crucial at different stages in sperm's life; for example size-determined sperm velocity is a key determinant of fertilization success. In addition, numbers and size may also be influenced by diverse energetic budgets required at different stages of sperm formation. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.

Evolution of the hip and pelvis.

Science.gov (United States)

Hogervorst, Tom; Bouma, Heinse W; de Vos, John

2009-08-01

Man's evolution features two unique developments: growing a huge brain and upright gait. Their combination makes the pelvis the most defining skeletal element to read human evolution. Recent revival in joint preserving hip surgery have brought to attention morphological variations of the human hip that appear similar to hips of extant mammals. In man, such variations can produce hip osteoarthrosis through motion. We reviewed the evolution of the hip and pelvis with special interest in morphology that can lead to motion induced osteoarthrosis in man. The combination of giving birth to big brained babies and walking upright has produced marked differences between the sexes in pelvis and hip morphology, each having their characteristic mode of hip impingement and osteoarthrosis.

The role of docosahexaenoic and the marine food web as determinants of evolution and hominid brain development: the challenge for human sustainability.

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Crawford, Michael A; Broadhurst, C Leigh

2012-01-01

Life originated on this planet about 3 billion years ago. For the first 2.5 billion years of life there was ample opportunity for DNA modification. Yet there is no evidence of significant change in life forms during that time. It was not until about 600 million years ago, when the oxygen tension rose to a point where air-breathing life forms became thermodynamically possible, that a major change can be abruptly seen in the fossil record. The sudden appearance of the 32 phyla in the Cambrian fossil record was also associated with the appearance of intracellular detail not seen in previous life forms. That detail was provided by cell membranes made with lipids (membrane fats) as structural essentials. Lipids thus played a major, as yet unrecognised, role as determinants in evolution. The compartmentalisation of intracellular, specialist functions as in the nucleus, mitochondria, reticulo-endothelial system and plasma membrane led to cellular specialisation and then speciation. Thus, not only oxygen but also the marine lipids were drivers in the Cambrian explosion. Docosahexaenoic acid (DHA) (all-cis-docosa-4,7,10,13,16,19-hexaenoic acid, C22:6ω3 or C22:6, n-3, DHA) is a major feature of marine lipids. It requires six oxygen atoms to insert its six double bonds, so it would not have been abundant before oxidative metabolism became plentiful. DHA provided the membrane backbone for the emergence of new photoreceptors that converted photons into electricity, laying the foundation for the evolution of other signalling systems, the nervous system and the brain. Hence, the ω3 DHA from the marine food web must have played a critical role in human evolution. There is also clear evidence from molecular biology that DHA is a determinant of neuronal migration, neurogenesis and the expression of several genes involved in brain growth and function. That same process was essential to the ultimate cerebral expansion in human evolution. There is now incontrovertible support of this

Midsagittal Brain Variation among Non-Human Primates: Insights into Evolutionary Expansion of the Human Precuneus.

Science.gov (United States)

Pereira-Pedro, Ana Sofia; Rilling, James K; Chen, Xu; Preuss, Todd M; Bruner, Emiliano

2017-01-01

The precuneus is a major element of the superior parietal lobule, positioned on the medial side of the hemisphere and reaching the dorsal surface of the brain. It is a crucial functional region for visuospatial integration, visual imagery, and body coordination. Previously, we argued that the precuneus expanded in recent human evolution, based on a combination of paleontological, comparative, and intraspecific evidence from fossil and modern human endocasts as well as from human and chimpanzee brains. The longitudinal proportions of this region are a major source of anatomical variation among adult humans and, being much larger in Homo sapiens, is the main characteristic differentiating human midsagittal brain morphology from that of our closest living primate relative, the chimpanzee. In the current shape analysis, we examine precuneus variation in non-human primates through landmark-based models, to evaluate the general pattern of variability in non-human primates, and to test whether precuneus proportions are influenced by allometric effects of brain size. Results show that precuneus proportions do not covary with brain size, and that the main difference between monkeys and apes involves a vertical expansion of the frontal and occipital regions in apes. Such differences might reflect differences in brain proportions or differences in cranial architecture. In this sample, precuneus variation is apparently not influenced by phylogenetic or allometric factors, but does vary consistently within species, at least in chimpanzees and macaques. This result further supports the hypothesis that precuneus expansion in modern humans is not merely a consequence of increasing brain size or of allometric scaling, but rather represents a species-specific morphological change in our lineage. © 2017 S. Karger AG, Basel.

INITIAL PLANETESIMAL SIZES AND THE SIZE DISTRIBUTION OF SMALL KUIPER BELT OBJECTS

International Nuclear Information System (INIS)

Schlichting, Hilke E.; Fuentes, Cesar I.; Trilling, David E.

2013-01-01

The Kuiper Belt is a remnant from the early solar system and its size distribution contains many important constraints that can be used to test models of planet formation and collisional evolution. We show, by comparing observations with theoretical models, that the observed Kuiper Belt size distribution is well matched by coagulation models, which start with an initial planetesimal population with radii of about 1 km, and subsequent collisional evolution. We find that the observed size distribution above R ∼ 30 km is primordial, i.e., it has not been modified by collisional evolution over the age of the solar system, and that the size distribution below R ∼ 30 km has been modified by collisions and that its slope is well matched by collisional evolution models that use published strength laws. We investigate in detail the resulting size distribution of bodies ranging from 0.01 km to 30 km and find that its slope changes several times as a function of radius before approaching the expected value for an equilibrium collisional cascade of material strength dominated bodies for R ∼< 0.1 km. Compared to a single power-law size distribution that would span the whole range from 0.01 km to 30 km, we find in general a strong deficit of bodies around R ∼ 10 km and a strong excess of bodies around 2 km in radius. This deficit and excess of bodies are caused by the planetesimal size distribution left over from the runaway growth phase, which left most of the initial mass in small planetesimals while only a small fraction of the total mass is converted into large protoplanets. This excess mass in small planetesimals leaves a permanent signature in the size distribution of small bodies that is not erased after 4.5 Gyr of collisional evolution. Observations of the small Kuiper Belt Object (KBO) size distribution can therefore test if large KBOs grew as a result of runaway growth and constrained the initial planetesimal sizes. We find that results from recent KBO

Concerted evolution of body mass and cell size: similar patterns among species of birds (Galliformes) and mammals (Rodentia)

Science.gov (United States)

Dragosz-Kluska, Dominika; Pis, Tomasz; Pawlik, Katarzyna; Kapustka, Filip; Kilarski, Wincenty M.; Kozłowski, Jan

2018-01-01

ABSTRACT Cell size plays a role in body size evolution and environmental adaptations. Addressing these roles, we studied body mass and cell size in Galliformes birds and Rodentia mammals, and collected published data on their genome sizes. In birds, we measured erythrocyte nuclei and basal metabolic rates (BMRs). In birds and mammals, larger species consistently evolved larger cells for five cell types (erythrocytes, enterocytes, chondrocytes, skin epithelial cells, and kidney proximal tubule cells) and evolved smaller hepatocytes. We found no evidence that cell size differences originated through genome size changes. We conclude that the organism-wide coordination of cell size changes might be an evolutionarily conservative characteristic, and the convergent evolutionary body size and cell size changes in Galliformes and Rodentia suggest the adaptive significance of cell size. Recent theory predicts that species evolving larger cells waste less energy on tissue maintenance but have reduced capacities to deliver oxygen to mitochondria and metabolize resources. Indeed, birds with larger size of the abovementioned cell types and smaller hepatocytes have evolved lower mass-specific BMRs. We propose that the inconsistent pattern in hepatocytes derives from the efficient delivery system to hepatocytes, combined with their intense involvement in supracellular function and anabolic activity. PMID:29540429

Concerted evolution of body mass and cell size: similar patterns among species of birds (Galliformes and mammals (Rodentia

Directory of Open Access Journals (Sweden)

Marcin Czarnoleski

2018-04-01

Full Text Available Cell size plays a role in body size evolution and environmental adaptations. Addressing these roles, we studied body mass and cell size in Galliformes birds and Rodentia mammals, and collected published data on their genome sizes. In birds, we measured erythrocyte nuclei and basal metabolic rates (BMRs. In birds and mammals, larger species consistently evolved larger cells for five cell types (erythrocytes, enterocytes, chondrocytes, skin epithelial cells, and kidney proximal tubule cells and evolved smaller hepatocytes. We found no evidence that cell size differences originated through genome size changes. We conclude that the organism-wide coordination of cell size changes might be an evolutionarily conservative characteristic, and the convergent evolutionary body size and cell size changes in Galliformes and Rodentia suggest the adaptive significance of cell size. Recent theory predicts that species evolving larger cells waste less energy on tissue maintenance but have reduced capacities to deliver oxygen to mitochondria and metabolize resources. Indeed, birds with larger size of the abovementioned cell types and smaller hepatocytes have evolved lower mass-specific BMRs. We propose that the inconsistent pattern in hepatocytes derives from the efficient delivery system to hepatocytes, combined with their intense involvement in supracellular function and anabolic activity.

A phenology of the evolution of endothermy in birds and mammals.

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Lovegrove, Barry G

2017-05-01

Recent palaeontological data and novel physiological hypotheses now allow a timescaled reconstruction of the evolution of endothermy in birds and mammals. A three-phase iterative model describing how endothermy evolved from Permian ectothermic ancestors is presented. In Phase One I propose that the elevation of endothermy - increased metabolism and body temperature (T b ) - complemented large-body-size homeothermy during the Permian and Triassic in response to the fitness benefits of enhanced embryo development (parental care) and the activity demands of conquering dry land. I propose that Phase Two commenced in the Late Triassic and Jurassic and was marked by extreme body-size miniaturization, the evolution of enhanced body insulation (fur and feathers), increased brain size, thermoregulatory control, and increased ecomorphological diversity. I suggest that Phase Three occurred during the Cretaceous and Cenozoic and involved endothermic pulses associated with the evolution of muscle-powered flapping flight in birds, terrestrial cursoriality in mammals, and climate adaptation in response to Late Cenozoic cooling in both birds and mammals. Although the triphasic model argues for an iterative evolution of endothermy in pulses throughout the Mesozoic and Cenozoic, it is also argued that endothermy was potentially abandoned at any time that a bird or mammal did not rely upon its thermal benefits for parental care or breeding success. The abandonment would have taken the form of either hibernation or daily torpor as observed in extant endotherms. Thus torpor and hibernation are argued to be as ancient as the origins of endothermy itself, a plesiomorphic characteristic observed today in many small birds and mammals. © 2016 Cambridge Philosophical Society.

Human evolution. Evolution of early Homo: an integrated biological perspective.

Science.gov (United States)

Antón, Susan C; Potts, Richard; Aiello, Leslie C

2014-07-04

Integration of evidence over the past decade has revised understandings about the major adaptations underlying the origin and early evolution of the genus Homo. Many features associated with Homo sapiens, including our large linear bodies, elongated hind limbs, large energy-expensive brains, reduced sexual dimorphism, increased carnivory, and unique life history traits, were once thought to have evolved near the origin of the genus in response to heightened aridity and open habitats in Africa. However, recent analyses of fossil, archaeological, and environmental data indicate that such traits did not arise as a single package. Instead, some arose substantially earlier and some later than previously thought. From ~2.5 to 1.5 million years ago, three lineages of early Homo evolved in a context of habitat instability and fragmentation on seasonal, intergenerational, and evolutionary time scales. These contexts gave a selective advantage to traits, such as dietary flexibility and larger body size, that facilitated survival in shifting environments. Copyright © 2014, American Association for the Advancement of Science.

The nearly neutral and selection theories of molecular evolution under the fisher geometrical framework: substitution rate, population size, and complexity.

Science.gov (United States)

Razeto-Barry, Pablo; Díaz, Javier; Vásquez, Rodrigo A

2012-06-01

The general theories of molecular evolution depend on relatively arbitrary assumptions about the relative distribution and rate of advantageous, deleterious, neutral, and nearly neutral mutations. The Fisher geometrical model (FGM) has been used to make distributions of mutations biologically interpretable. We explored an FGM-based molecular model to represent molecular evolutionary processes typically studied by nearly neutral and selection models, but in which distributions and relative rates of mutations with different selection coefficients are a consequence of biologically interpretable parameters, such as the average size of the phenotypic effect of mutations and the number of traits (complexity) of organisms. A variant of the FGM-based model that we called the static regime (SR) represents evolution as a nearly neutral process in which substitution rates are determined by a dynamic substitution process in which the population's phenotype remains around a suboptimum equilibrium fitness produced by a balance between slightly deleterious and slightly advantageous compensatory substitutions. As in previous nearly neutral models, the SR predicts a negative relationship between molecular evolutionary rate and population size; however, SR does not have the unrealistic properties of previous nearly neutral models such as the narrow window of selection strengths in which they work. In addition, the SR suggests that compensatory mutations cannot explain the high rate of fixations driven by positive selection currently found in DNA sequences, contrary to what has been previously suggested. We also developed a generalization of SR in which the optimum phenotype can change stochastically due to environmental or physiological shifts, which we called the variable regime (VR). VR models evolution as an interplay between adaptive processes and nearly neutral steady-state processes. When strong environmental fluctuations are incorporated, the process becomes a selection model

Interspecific geographic range size-body size relationship and the diversification dynamics of Neotropical furnariid birds.

Science.gov (United States)

Inostroza-Michael, Oscar; Hernández, Cristián E; Rodríguez-Serrano, Enrique; Avaria-Llautureo, Jorge; Rivadeneira, Marcelo M

2018-05-01

Among the earliest macroecological patterns documented, is the range and body size relationship, characterized by a minimum geographic range size imposed by the species' body size. This boundary for the geographic range size increases linearly with body size and has been proposed to have implications in lineages evolution and conservation. Nevertheless, the macroevolutionary processes involved in the origin of this boundary and its consequences on lineage diversification have been poorly explored. We evaluate the macroevolutionary consequences of the difference (hereafter the distance) between the observed and the minimum range sizes required by the species' body size, to untangle its role on the diversification of a Neotropical species-rich bird clade using trait-dependent diversification models. We show that speciation rate is a positive hump-shaped function of the distance to the lower boundary. The species with highest and lowest distances to minimum range size had lower speciation rates, while species close to medium distances values had the highest speciation rates. Further, our results suggest that the distance to the minimum range size is a macroevolutionary constraint that affects the diversification process responsible for the origin of this macroecological pattern in a more complex way than previously envisioned. © 2018 The Author(s). Evolution © 2018 The Society for the Study of Evolution.

Phenotypic integration of neurocranium and brain.

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Richtsmeier, Joan T; Aldridge, Kristina; DeLeon, Valerie B; Panchal, Jayesh; Kane, Alex A; Marsh, Jeffrey L; Yan, Peng; Cole, Theodore M

2006-07-15

Evolutionary history of Mammalia provides strong evidence that the morphology of skull and brain change jointly in evolution. Formation and development of brain and skull co-occur and are dependent upon a series of morphogenetic and patterning processes driven by genes and their regulatory programs. Our current concept of skull and brain as separate tissues results in distinct analyses of these tissues by most researchers. In this study, we use 3D computed tomography and magnetic resonance images of pediatric individuals diagnosed with premature closure of cranial sutures (craniosynostosis) to investigate phenotypic relationships between the brain and skull. It has been demonstrated previously that the skull and brain acquire characteristic dysmorphologies in isolated craniosynostosis, but relatively little is known of the developmental interactions that produce these anomalies. Our comparative analysis of phenotypic integration of brain and skull in premature closure of the sagittal and the right coronal sutures demonstrates that brain and skull are strongly integrated and that the significant differences in patterns of association do not occur local to the prematurely closed suture. We posit that the current focus on the suture as the basis for this condition may identify a proximate, but not the ultimate cause for these conditions. Given that premature suture closure reduces the number of cranial bones, and that a persistent loss of skull bones is demonstrated over the approximately 150 million years of synapsid evolution, craniosynostosis may serve as an informative model for evolution of the mammalian skull. Copyright 2006 Wiley-Liss, Inc.

When and Why Did Brains Break Symmetry?

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Lesley J. Rogers

2015-12-01

Full Text Available Asymmetry of brain function is known to be widespread amongst vertebrates, and it seems to have appeared very early in their evolution. In fact, recent evidence of functional asymmetry in invertebrates suggests that even small brains benefit from the allocation of different functions to the left and right sides. This paper discusses the differing functions of the left and right sides of the brain, including the roles of the left and right antennae of bees (several species in both short- and long-term recall of olfactory memories and in social behaviour. It considers the likely advantages of functional asymmetry in small and large brains and whether functional asymmetry in vertebrates and invertebrates is analogous or homologous. Neural or cognitive capacity can be enhanced both by the evolution of a larger brain and by lateralization of brain function: a possible reason why both processes occur side-by-side is offered.

Towards a Computational Comparative Neuroprimatology: Framing the language-ready brain

Science.gov (United States)

Arbib, Michael A.

2016-03-01

We make the case for developing a Computational Comparative Neuroprimatology to inform the analysis of the function and evolution of the human brain. First, we update the mirror system hypothesis on the evolution of the language-ready brain by (i) modeling action and action recognition and opportunistic scheduling of macaque brains to hypothesize the nature of the last common ancestor of macaque and human (LCA-m); and then we (ii) introduce dynamic brain modeling to show how apes could acquire gesture through ontogenetic ritualization, hypothesizing the nature of evolution from LCA-m to the last common ancestor of chimpanzee and human (LCA-c). We then (iii) hypothesize the role of imitation, pantomime, protosign and protospeech in biological and cultural evolution from LCA-c to Homo sapiens with a language-ready brain. Second, we suggest how cultural evolution in Homo sapiens led from protolanguages to full languages with grammar and compositional semantics. Third, we assess the similarities and differences between the dorsal and ventral streams in audition and vision as the basis for presenting and comparing two models of language processing in the human brain: A model of (i) the auditory dorsal and ventral streams in sentence comprehension; and (ii) the visual dorsal and ventral streams in defining ;what language is about; in both production and perception of utterances related to visual scenes provide the basis for (iii) a first step towards a synthesis and a look at challenges for further research.

Evolution of avian clutch size along latitudinal gradients: do seasonality, nest predation or breeding season length matter?

Science.gov (United States)

Griebeler, E M; Caprano, T; Böhning-Gaese, K

2010-05-01

Birds display a latitudinal gradient in clutch size with smaller clutches in the tropics and larger in the temperate region. Three factors have been proposed to affect this pattern: seasonality of resources (SR), nest predation and length of the breeding season (LBS). Here, we test the importance of these factors by modelling clutch size evolution within bird populations under different environmental settings. We use an individual-based ecogenetic simulation model that combines principles from population ecology and life history theory. Results suggest that increasing SR from the tropics to the poles by itself or in combination with a decreasing predation rate and LBS can generate the latitudinal gradient in clutch size. Annual fecundity increases and annual adult survival rate decreases from the tropics to the poles. We further show that the annual number of breeding attempts that (together with clutch size) determines total annual egg production is an important trait to understand latitudinal patterns in these life history characteristics. Field experiments that manipulate environmental factors have to record effects not only on clutch size, but also on annual number of breeding attempts. We use our model to predict the outcome of such experiments under different environmental settings.

Neuroscience, brains, and computers

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Giorno Maria Innocenti

2013-07-01

Full Text Available This paper addresses the role of the neurosciences in establishing what the brain is and how states of the brain relate to states of the mind. The brain is viewed as a computational deviceperforming operations on symbols. However, the brain is a special purpose computational devicedesigned by evolution and development for survival and reproduction, in close interaction with theenvironment. The hardware of the brain (its structure is very different from that of man-made computers.The computational style of the brain is also very different from traditional computers: the computationalalgorithms, instead of being sets of external instructions, are embedded in brain structure. Concerningthe relationships between brain and mind a number of questions lie ahead. One of them is why andhow, only the human brain grasped the notion of God, probably only at the evolutionary stage attainedby Homo sapiens.

Art and brain: insights from neuropsychology, biology and evolution.

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Zaidel, Dahlia W

2010-02-01

Art is a uniquely human activity associated fundamentally with symbolic and abstract cognition. Its practice in human societies throughout the world, coupled with seeming non-functionality, has led to three major brain theories of art. (1) The localized brain regions and pathways theory links art to multiple neural regions. (2) The display of art and its aesthetics theory is tied to the biological motivation of courtship signals and mate selection strategies in animals. (3) The evolutionary theory links the symbolic nature of art to critical pivotal brain changes in Homo sapiens supporting increased development of language and hierarchical social grouping. Collectively, these theories point to art as a multi-process cognition dependent on diverse brain regions and on redundancy in art-related functional representation.

Brain atrophy and lesion load predict long term disability in multiple sclerosis

DEFF Research Database (Denmark)

Popescu, Veronica; Agosta, Federica; Hulst, Hanneke E

2013-01-01

To determine whether brain atrophy and lesion volumes predict subsequent 10 year clinical evolution in multiple sclerosis (MS).......To determine whether brain atrophy and lesion volumes predict subsequent 10 year clinical evolution in multiple sclerosis (MS)....

The evolution of biomass-burning aerosol size distributions due to coagulation: dependence on fire and meteorological details and parameterization

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K. M. Sakamoto

2016-06-01

Full Text Available Biomass-burning aerosols have a significant effect on global and regional aerosol climate forcings. To model the magnitude of these effects accurately requires knowledge of the size distribution of the emitted and evolving aerosol particles. Current biomass-burning inventories do not include size distributions, and global and regional models generally assume a fixed size distribution from all biomass-burning emissions. However, biomass-burning size distributions evolve in the plume due to coagulation and net organic aerosol (OA evaporation or formation, and the plume processes occur on spacial scales smaller than global/regional-model grid boxes. The extent of this size-distribution evolution is dependent on a variety of factors relating to the emission source and atmospheric conditions. Therefore, accurately accounting for biomass-burning aerosol size in global models requires an effective aerosol size distribution that accounts for this sub-grid evolution and can be derived from available emission-inventory and meteorological parameters. In this paper, we perform a detailed investigation of the effects of coagulation on the aerosol size distribution in biomass-burning plumes. We compare the effect of coagulation to that of OA evaporation and formation. We develop coagulation-only parameterizations for effective biomass-burning size distributions using the SAM-TOMAS large-eddy simulation plume model. For the most-sophisticated parameterization, we use the Gaussian Emulation Machine for Sensitivity Analysis (GEM-SA to build a parameterization of the aged size distribution based on the SAM-TOMAS output and seven inputs: emission median dry diameter, emission distribution modal width, mass emissions flux, fire area, mean boundary-layer wind speed, plume mixing depth, and time/distance since emission. This parameterization was tested against an independent set of SAM-TOMAS simulations and yields R2 values of 0.83 and 0.89 for Dpm and modal width

The evolution of biomass-burning aerosol size distributions due to coagulation: dependence on fire and meteorological details and parameterization

Science.gov (United States)

Sakamoto, Kimiko M.; Laing, James R.; Stevens, Robin G.; Jaffe, Daniel A.; Pierce, Jeffrey R.

2016-06-01

Biomass-burning aerosols have a significant effect on global and regional aerosol climate forcings. To model the magnitude of these effects accurately requires knowledge of the size distribution of the emitted and evolving aerosol particles. Current biomass-burning inventories do not include size distributions, and global and regional models generally assume a fixed size distribution from all biomass-burning emissions. However, biomass-burning size distributions evolve in the plume due to coagulation and net organic aerosol (OA) evaporation or formation, and the plume processes occur on spacial scales smaller than global/regional-model grid boxes. The extent of this size-distribution evolution is dependent on a variety of factors relating to the emission source and atmospheric conditions. Therefore, accurately accounting for biomass-burning aerosol size in global models requires an effective aerosol size distribution that accounts for this sub-grid evolution and can be derived from available emission-inventory and meteorological parameters. In this paper, we perform a detailed investigation of the effects of coagulation on the aerosol size distribution in biomass-burning plumes. We compare the effect of coagulation to that of OA evaporation and formation. We develop coagulation-only parameterizations for effective biomass-burning size distributions using the SAM-TOMAS large-eddy simulation plume model. For the most-sophisticated parameterization, we use the Gaussian Emulation Machine for Sensitivity Analysis (GEM-SA) to build a parameterization of the aged size distribution based on the SAM-TOMAS output and seven inputs: emission median dry diameter, emission distribution modal width, mass emissions flux, fire area, mean boundary-layer wind speed, plume mixing depth, and time/distance since emission. This parameterization was tested against an independent set of SAM-TOMAS simulations and yields R2 values of 0.83 and 0.89 for Dpm and modal width, respectively. The

New tyrannosaur from the mid-Cretaceous of Uzbekistan clarifies evolution of giant body sizes and advanced senses in tyrant dinosaurs.

Science.gov (United States)

Brusatte, Stephen L; Averianov, Alexander; Sues, Hans-Dieter; Muir, Amy; Butler, Ian B

2016-03-29

Tyrannosaurids--the familiar group of carnivorous dinosaurs including Tyrannosaurus and Albertosaurus--were the apex predators in continental ecosystems in Asia and North America during the latest Cretaceous (ca. 80-66 million years ago). Their colossal sizes and keen senses are considered key to their evolutionary and ecological success, but little is known about how these features developed as tyrannosaurids evolved from smaller basal tyrannosauroids that first appeared in the fossil record in the Middle Jurassic (ca. 170 million years ago). This is largely because of a frustrating 20+ million-year gap in the mid-Cretaceous fossil record, when tyrannosauroids transitioned from small-bodied hunters to gigantic apex predators but from which no diagnostic specimens are known. We describe the first distinct tyrannosauroid species from this gap, based on a highly derived braincase and a variety of other skeletal elements from the Turonian (ca. 90-92 million years ago) of Uzbekistan. This taxon is phylogenetically intermediate between the oldest basal tyrannosauroids and the latest Cretaceous forms. It had yet to develop the giant size and extensive cranial pneumaticity of T. rex and kin but does possess the highly derived brain and inner ear characteristic of the latest Cretaceous species. Tyrannosauroids apparently developed huge size rapidly during the latest Cretaceous, and their success in the top predator role may have been enabled by their brain and keen senses that first evolved at smaller body size.

New tyrannosaur from the mid-Cretaceous of Uzbekistan clarifies evolution of giant body sizes and advanced senses in tyrant dinosaurs

Science.gov (United States)

Brusatte, Stephen L.; Averianov, Alexander; Sues, Hans-Dieter; Muir, Amy; Butler, Ian B.

2016-03-01

Tyrannosaurids-the familiar group of carnivorous dinosaurs including Tyrannosaurus and Albertosaurus-were the apex predators in continental ecosystems in Asia and North America during the latest Cretaceous (ca. 80-66 million years ago). Their colossal sizes and keen senses are considered key to their evolutionary and ecological success, but little is known about how these features developed as tyrannosaurids evolved from smaller basal tyrannosauroids that first appeared in the fossil record in the Middle Jurassic (ca. 170 million years ago). This is largely because of a frustrating 20+ million-year gap in the mid-Cretaceous fossil record, when tyrannosauroids transitioned from small-bodied hunters to gigantic apex predators but from which no diagnostic specimens are known. We describe the first distinct tyrannosauroid species from this gap, based on a highly derived braincase and a variety of other skeletal elements from the Turonian (ca. 90-92 million years ago) of Uzbekistan. This taxon is phylogenetically intermediate between the oldest basal tyrannosauroids and the latest Cretaceous forms. It had yet to develop the giant size and extensive cranial pneumaticity of T. rex and kin but does possess the highly derived brain and inner ear characteristic of the latest Cretaceous species. Tyrannosauroids apparently developed huge size rapidly during the latest Cretaceous, and their success in the top predator role may have been enabled by their brain and keen senses that first evolved at smaller body size.

The evolution of genome size in ants

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Spagna Joseph C

2008-02-01

Full Text Available Abstract Background Despite the economic and ecological importance of ants, genomic tools for this family (Formicidae remain woefully scarce. Knowledge of genome size, for example, is a useful and necessary prerequisite for the development of many genomic resources, yet it has been reported for only one ant species (Solenopsis invicta, and the two published estimates for this species differ by 146.7 Mb (0.15 pg. Results Here, we report the genome size for 40 species of ants distributed across 10 of the 20 currently recognized subfamilies, thus making Formicidae the 4th most surveyed insect family and elevating the Hymenoptera to the 5th most surveyed insect order. Our analysis spans much of the ant phylogeny, from the less derived Amblyoponinae and Ponerinae to the more derived Myrmicinae, Formicinae and Dolichoderinae. We include a number of interesting and important taxa, including the invasive Argentine ant (Linepithema humile, Neotropical army ants (genera Eciton and Labidus, trapjaw ants (Odontomachus, fungus-growing ants (Apterostigma, Atta and Sericomyrmex, harvester ants (Messor, Pheidole and Pogonomyrmex, carpenter ants (Camponotus, a fire ant (Solenopsis, and a bulldog ant (Myrmecia. Our results show that ants possess small genomes relative to most other insects, yet genome size varies three-fold across this insect family. Moreover, our data suggest that two whole-genome duplications may have occurred in the ancestors of the modern Ectatomma and Apterostigma. Although some previous studies of other taxa have revealed a relationship between genome size and body size, our phylogenetically-controlled analysis of this correlation did not reveal a significant relationship. Conclusion This is the first analysis of genome size in ants (Formicidae and the first across multiple species of social insects. We show that genome size is a variable trait that can evolve gradually over long time spans, as well as rapidly, through processes that may

Brain size and brain/intracranial volume ratio in major mental illness

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Teale Peter

2010-10-01

Full Text Available Abstract Background This paper summarizes the findings of a long term study addressing the question of how several brain volume measure are related to three major mental illnesses in a Colorado subject group. It reports results obtained from a large N, collected and analyzed by the same laboratory over a multiyear period, with visually guided MRI segmentation being the primary initial analytic tool. Methods Intracerebral volume (ICV, total brain volume (TBV, ventricular volume (VV, ventricular/brain ratio (VBR, and TBV/ICV ratios were calculated from a total of 224 subject MRIs collected over a period of 13 years. Subject groups included controls (C, N = 89, and patients with schizophrenia (SZ, N = 58, bipolar disorder (BD, N = 51, and schizoaffective disorder (SAD, N = 26. Results ICV, TBV, and VV measures compared favorably with values obtained by other research groups, but in this study did not differ significantly between groups. TBV/ICV ratios were significantly decreased, and VBR increased, in the SZ and BD groups compared to the C group. The SAD group did not differ from C on any measure. Conclusions In this study TBV/ICV and VBR ratios separated SZ and BD patients from controls. Of interest however, SAD patients did not differ from controls on these measures. The findings suggest that the gross measure of TBV may not reliably differ in the major mental illnesses to a degree useful in diagnosis, likely due to the intrinsic variability of the measures in question; the differences in VBR appear more robust across studies. Differences in some of these findings compared to earlier reports from several laboratories finding significant differences between groups in VV and TBV may relate to phenomenological drift, differences in analytic techniques, and possibly the "file drawer problem".

On the Importance of Accounting for Competing Risks in Pediatric Brain Cancer: II. Regression Modeling and Sample Size

International Nuclear Information System (INIS)

Tai, Bee-Choo; Grundy, Richard; Machin, David

2011-01-01

Purpose: To accurately model the cumulative need for radiotherapy in trials designed to delay or avoid irradiation among children with malignant brain tumor, it is crucial to account for competing events and evaluate how each contributes to the timing of irradiation. An appropriate choice of statistical model is also important for adequate determination of sample size. Methods and Materials: We describe the statistical modeling of competing events (A, radiotherapy after progression; B, no radiotherapy after progression; and C, elective radiotherapy) using proportional cause-specific and subdistribution hazard functions. The procedures of sample size estimation based on each method are outlined. These are illustrated by use of data comparing children with ependymoma and other malignant brain tumors. The results from these two approaches are compared. Results: The cause-specific hazard analysis showed a reduction in hazards among infants with ependymoma for all event types, including Event A (adjusted cause-specific hazard ratio, 0.76; 95% confidence interval, 0.45-1.28). Conversely, the subdistribution hazard analysis suggested an increase in hazard for Event A (adjusted subdistribution hazard ratio, 1.35; 95% confidence interval, 0.80-2.30), but the reduction in hazards for Events B and C remained. Analysis based on subdistribution hazard requires a larger sample size than the cause-specific hazard approach. Conclusions: Notable differences in effect estimates and anticipated sample size were observed between methods when the main event showed a beneficial effect whereas the competing events showed an adverse effect on the cumulative incidence. The subdistribution hazard is the most appropriate for modeling treatment when its effects on both the main and competing events are of interest.

Towards a Computational Comparative Neuroprimatology: Framing the language-ready brain.

Science.gov (United States)

Arbib, Michael A

2016-03-01

We make the case for developing a Computational Comparative Neuroprimatology to inform the analysis of the function and evolution of the human brain. First, we update the mirror system hypothesis on the evolution of the language-ready brain by (i) modeling action and action recognition and opportunistic scheduling of macaque brains to hypothesize the nature of the last common ancestor of macaque and human (LCA-m); and then we (ii) introduce dynamic brain modeling to show how apes could acquire gesture through ontogenetic ritualization, hypothesizing the nature of evolution from LCA-m to the last common ancestor of chimpanzee and human (LCA-c). We then (iii) hypothesize the role of imitation, pantomime, protosign and protospeech in biological and cultural evolution from LCA-c to Homo sapiens with a language-ready brain. Second, we suggest how cultural evolution in Homo sapiens led from protolanguages to full languages with grammar and compositional semantics. Third, we assess the similarities and differences between the dorsal and ventral streams in audition and vision as the basis for presenting and comparing two models of language processing in the human brain: A model of (i) the auditory dorsal and ventral streams in sentence comprehension; and (ii) the visual dorsal and ventral streams in defining "what language is about" in both production and perception of utterances related to visual scenes provide the basis for (iii) a first step towards a synthesis and a look at challenges for further research. Copyright © 2015 Elsevier B.V. All rights reserved.

Sauropod dinosaurs evolved moderately sized genomes unrelated to body size.

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Organ, Chris L; Brusatte, Stephen L; Stein, Koen

2009-12-22

Sauropodomorph dinosaurs include the largest land animals to have ever lived, some reaching up to 10 times the mass of an African elephant. Despite their status defining the upper range for body size in land animals, it remains unknown whether sauropodomorphs evolved larger-sized genomes than non-avian theropods, their sister taxon, or whether a relationship exists between genome size and body size in dinosaurs, two questions critical for understanding broad patterns of genome evolution in dinosaurs. Here we report inferences of genome size for 10 sauropodomorph taxa. The estimates are derived from a Bayesian phylogenetic generalized least squares approach that generates posterior distributions of regression models relating genome size to osteocyte lacunae volume in extant tetrapods. We estimate that the average genome size of sauropodomorphs was 2.02 pg (range of species means: 1.77-2.21 pg), a value in the upper range of extant birds (mean = 1.42 pg, range: 0.97-2.16 pg) and near the average for extant non-avian reptiles (mean = 2.24 pg, range: 1.05-5.44 pg). The results suggest that the variation in size and architecture of genomes in extinct dinosaurs was lower than the variation found in mammals. A substantial difference in genome size separates the two major clades within dinosaurs, Ornithischia (large genomes) and Saurischia (moderate to small genomes). We find no relationship between body size and estimated genome size in extinct dinosaurs, which suggests that neutral forces did not dominate the evolution of genome size in this group.

Patterns of differences in brain morphology in humans as compared to extant apes.

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Aldridge, Kristina

2011-01-01

Although human evolution is characterized by a vast increase in brain size, it is not clear whether or not certain regions of the brain are enlarged disproportionately in humans, or how this enlargement relates to differences in overall neural morphology. The aim of this study is to determine whether or not there are specific suites of features that distinguish the morphology of the human brain from that of apes. The study sample consists of whole brain, in vivo magnetic resonance images (MRIs) of anatomically modern humans (Homo sapiens sapiens) and five ape species (gibbons, orangutans, gorillas, chimpanzees, bonobos). Twenty-nine 3D landmarks, including surface and internal features of the brain were located on 3D MRI reconstructions of each individual using MEASURE software. Landmark coordinate data were scaled for differences in size and analyzed using Euclidean Distance Matrix Analysis (EDMA) to statistically compare the brains of each non-human ape species to the human sample. Results of analyses show both a pattern of brain morphology that is consistently different between all apes and humans, as well as patterns that differ among species. Further, both the consistent and species-specific patterns include cortical and subcortical features. The pattern that remains consistent across species indicates a morphological reorganization of 1) relationships between cortical and subcortical frontal structures, 2) expansion of the temporal lobe and location of the amygdala, and 3) expansion of the anterior parietal region. Additionally, results demonstrate that, although there is a pattern of morphology that uniquely defines the human brain, there are also patterns that uniquely differentiate human morphology from the morphology of each non-human ape species, indicating that reorganization of neural morphology occurred at the evolutionary divergence of each of these groups. Copyright © 2010 Elsevier Ltd. All rights reserved.

Social cognition on the Internet: testing constraints on social network size.

Science.gov (United States)

Dunbar, R I M

2012-08-05

The social brain hypothesis (an explanation for the evolution of brain size in primates) predicts that humans typically cannot maintain more than 150 relationships at any one time. The constraint is partly cognitive (ultimately determined by some aspect of brain volume) and partly one of time. Friendships (but not necessarily kin relationships) are maintained by investing time in them, and failure to do so results in an inexorable deterioration in the quality of a relationship. The Internet, and in particular the rise of social networking sites (SNSs), raises the possibility that digital media might allow us to circumvent some or all of these constraints. This allows us to test the importance of these constraints in limiting human sociality. Although the recency of SNSs means that there have been relatively few studies, those that are available suggest that, in general, the ability to broadcast to many individuals at once, and the possibilities this provides in terms of continuously updating our understanding of network members' behaviour and thoughts, do not allow larger networks to be maintained. This may be because only relatively weak quality relationships can be maintained without face-to-face interaction.

Brain evolution, the determinates of food choice, and the omnivore's dilemma.

Science.gov (United States)

Armelagos, George J

2014-01-01

A coevolutionary paradigm using a biocultural perspective can help to unravel the complex interactions that led to the contemporary pattern of eating. Evolutionary history helps to understand the adaptation of diet and its nutritional implications. Anatomical and behavioral changes linked to changing dietary patterns in the Paleolithic resulted in an adaptive framework that affects modern diet. The evolution of an expanding brain, a shrinking large intestine, and lengthening small intestine necessitated a demand for nutritionally dense foods. The key to these changes is an understanding of the response to the omnivore's dilemma. Omnivores in their search for new items to feed their varied diet (neophilia) have a challenge when they fear (neophobia) novel items that may be poisonous and can cause death. The inborn mechanism initiates palate fatigue (sensory-specific satiety) ensuring a variety of foods will be eaten. Variety will limit the impact of toxins ingested and provide a more balanced diet. The development of cuisine, a momentous event in history, mediated the conflict, and changed the course of human evolution. The cuisine, a biocultural construct, defines which items found in nature are edible, how these products are transformed into food, the flavors used to add a sensory dimension to foods, and rules of eating or etiquette. Etiquette defines how, when, and with whom we eat. Patterns of eating in the modern setting are the end product of the way that Homo sapiens evolved and resolved the omnivore's dilemma. Control of fire and cooking expanded the range of available foods by creating a class of foods that are "predigested." An essential element to the evolution of the human diet was the transition to agriculture as the primary mode of subsistence. The Neolithic revolution dramatically narrowed the dietary niche by decreasing the variety of available foods, with the shift to intensive agriculture creating a dramatic decline in human nutrition. The recent

Midsagittal brain variation and MRI shape analysis of the precuneus in adult individuals

Science.gov (United States)

Bruner, Emiliano; Rangel de Lázaro, Gizéh; de la Cuétara, José Manuel; Martín-Loeches, Manuel; Colom, Roberto; Jacobs, Heidi I L

2014-01-01

Recent analyses indicate that the precuneus is one of the main centres of integration in terms of functional and structural processes within the human brain. This neuroanatomical element is formed by different subregions, involved in visuo-spatial integration, memory and self-awareness. We analysed the midsagittal brain shape in a sample of adult humans (n = 90) to evidence the patterns of variability and geometrical organization of this area. Interestingly, the major brain covariance pattern within adult humans is strictly associated with the relative proportions of the precuneus. Its morphology displays a marked individual variation, both in terms of geometry (mostly in its longitudinal dimensions) and anatomy (patterns of convolution). No patent differences are evident between males and females, and the allometric effect of size is minimal. However, in terms of morphology, the precuneus does not represent an individual module, being influenced by different neighbouring structures. Taking into consideration the apparent involvement of the precuneus in higher-order human brain functions and evolution, its wide variation further stresses the important role of these deep parietal areas in modern neuroanatomical organization. PMID:24397462

Prenatal Exposure to Autism-Specific Maternal Autoantibodies Alters Proliferation of Cortical Neural Precursor Cells, Enlarges Brain, and Increases Neuronal Size in Adult Animals.

Science.gov (United States)

Martínez-Cerdeño, Verónica; Camacho, Jasmin; Fox, Elizabeth; Miller, Elaine; Ariza, Jeanelle; Kienzle, Devon; Plank, Kaela; Noctor, Stephen C; Van de Water, Judy

2016-01-01

Autism spectrum disorders (ASDs) affect up to 1 in 68 children. Autism-specific autoantibodies directed against fetal brain proteins have been found exclusively in a subpopulation of mothers whose children were diagnosed with ASD or maternal autoantibody-related autism. We tested the impact of autoantibodies on brain development in mice by transferring human antigen-specific IgG directly into the cerebral ventricles of embryonic mice during cortical neurogenesis. We show that autoantibodies recognize radial glial cells during development. We also show that prenatal exposure to autism-specific maternal autoantibodies increased stem cell proliferation in the subventricular zone (SVZ) of the embryonic neocortex, increased adult brain size and weight, and increased the size of adult cortical neurons. We propose that prenatal exposure to autism-specific maternal autoantibodies directly affects radial glial cell development and presents a viable pathologic mechanism for the maternal autoantibody-related prenatal ASD risk factor. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Insights into the evolution of mitochondrial genome size from complete sequences of Citrullus lanatus and Cucurbita pepo (Cucurbitaceae).

Science.gov (United States)

Alverson, Andrew J; Wei, XiaoXin; Rice, Danny W; Stern, David B; Barry, Kerrie; Palmer, Jeffrey D

2010-06-01

The mitochondrial genomes of seed plants are unusually large and vary in size by at least an order of magnitude. Much of this variation occurs within a single family, the Cucurbitaceae, whose genomes range from an estimated 390 to 2,900 kb in size. We sequenced the mitochondrial genomes of Citrullus lanatus (watermelon: 379,236 nt) and Cucurbita pepo (zucchini: 982,833 nt)--the two smallest characterized cucurbit mitochondrial genomes--and determined their RNA editing content. The relatively compact Citrullus mitochondrial genome actually contains more and longer genes and introns, longer segmental duplications, and more discernibly nuclear-derived DNA. The large size of the Cucurbita mitochondrial genome reflects the accumulation of unprecedented amounts of both chloroplast sequences (>113 kb) and short repeated sequences (>370 kb). A low mutation rate has been hypothesized to underlie increases in both genome size and RNA editing frequency in plant mitochondria. However, despite its much larger genome, Cucurbita has a significantly higher synonymous substitution rate (and presumably mutation rate) than Citrullus but comparable levels of RNA editing. The evolution of mutation rate, genome size, and RNA editing are apparently decoupled in Cucurbitaceae, reflecting either simple stochastic variation or governance by different factors.

Stepwise morphological evolution of the active Yellow River (Huanghe) delta lobe (1976-2013): Dominant roles of riverine discharge and sediment grain size

Science.gov (United States)

Wu, Xiao; Bi, Naishuang; Xu, Jingping; Nittrouer, Jeffrey A.; Yang, Zuosheng; Saito, Yoshiki; Wang, Houjie

2017-09-01

The presently active Yellow River (Huanghe) delta lobe has been formed since 1976 when the river was artificially diverted. The process and driving forces of morphological evolution of the present delta lobe still remain unclear. Here we examined the stepwise morphological evolution of the active Yellow River delta lobe including both the subaerial and the subaqueous components, and illustrated the critical roles of riverine discharge and sediment grain size in dominating the deltaic evolution. The critical sediment loads for maintaining the delta stability were also calculated from water discharge and sediment load measured at station Lijin, the last gauging station approximately 100 km upstream from the river mouth. The results indicated that the development of active delta lobe including both subaerial and subaqueous components has experienced four sequential stages. During the first stage (1976-1981) after the channel migration, the unchannelized river flow enhanced deposition within the channel and floodplain between Lijin station and the river mouth. Therefore, the critical sediment supply calculated by the river inputs obtained from station Lijin was the highest. However, the actual sediment load at this stage (0.84 Gt/yr) was more than twice of the critical sediment load ( 0.35 Gt/yr) for sustaining the active subaerial area, which favored a rapid seaward progradation of the Yellow River subaerial delta. During the second stage (1981-1996), the engineering-facilitated channelized river flow and the increase in median grain size of suspended sediment delivered to the sea resulted in the critical sediment load for keeping the delta stability deceasing to 0.29 Gt/yr. The active delta lobe still gradually prograded seaward at an accretion rate of 11.9 km2/yr at this stage as the annual sediment load at Lijin station was 0.55 Gt/yr. From 1996 to 2002, the critical sediment load further decreased to 0.15 Gt/yr with the sediment grain size increased to 22.5 �

Brain Morphology of the Zhoukoudian H.erectus Half a Million Years Ago

Institute of Scientific and Technical Information of China (English)

WU Xiujie

2010-01-01

@@ In the process of human evolution,how has the brain changed? When did it happen? Why did it happen?These questions are some of the hottest topics in paleoanthropology today.The study of brain evolution falls into the sub-discipline of paleoneurology and is based on direct examination of the fossil record of humans and their closest hominid relatives.Unfortunately,brains are not preserved in the fossil record.The most direct evidence of ancestral brains is available,however,from endocasts.An endocast is the impression taken from the inside of a cranium retaining the surface features of the brain.

Size evolution of ultrafine particles: Differential signatures of normal and episodic events.

Science.gov (United States)

Joshi, Manish; Khan, Arshad; Anand, S; Sapra, B K

2016-01-01

The effect of fireworks on the aerosol number characteristics of atmosphere was studied for an urban mega city. Measurements were made at 50 m height to assess the local changes around the festival days. Apart from the increase in total number concentration and characteristic accumulation mode, short-term increase of ultrafine particle concentration was noted. Total number concentration varies an order of magnitude during the measurement period in which peak occurs at a frequency of approximately one per day. On integral scale, it seems not possible to distinguish an episodic (e.g. firework bursting induced aerosol emission) and a normal (ambient atmospheric changes) event. However these events could be differentiated on the basis of size evolution analysis around number concentration peaks. The results are discussed relative to past studies and inferences are drawn towards aerosol signatures of firework bursting. The short-term burst in ultrafine particle concentration can pose an inhalation hazard. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evolution of size distribution, optical properties, and structure of Si nanoparticles obtained by laser-assisted fragmentation

Science.gov (United States)

Plautz, G. L.; Graff, I. L.; Schreiner, W. H.; Bezerra, A. G.

2017-05-01

We investigate the physical properties of Si-based nanoparticles produced by an environment-friendly three-step method relying on: (1) laser ablation of a solid target immersed in water, (2) centrifugation and separation, and (3) laser-assisted fragmentation. The evolution of size distribution is followed after each step by means of dynamic light scattering (DLS) measurements and crosschecked by transmission electron microscopy (TEM). The as-ablated colloidal suspension of Si nanoparticles presents a large size distribution, ranging from a few to hundreds of nanometers. Centrifugation drives the very large particles to the bottom eliminating them from the remaining suspension. Subsequent irradiation of height-separated suspensions with a second high-fluence (40 mJ/pulse) Nd:YAG laser operating at the fourth harmonic (λ =266 nm) leads to size reduction and ultra-small nanoparticles are obtainable depending on the starting size. Si nanoparticles as small as 1.5 nm with low dispersion (± 0.7 nm) are observed for the uppermost part after irradiation. These nanoparticles present a strong blue photoluminescence that remains stable for at least 8 weeks. Optical absorption (UV-Vis) measurements demonstrate an optical gap widening as a consequence of size decrease. Raman spectra present features related to pure silicon and silicon oxides for the irradiated sample. Interestingly, a defect band associated with silicon oxide is also identified, indicating the possible formation of defect states, which, in turn, supports the idea that the blue photoluminescence has its origin in defects.

FGFR3 regulates brain size by controlling progenitor cell proliferation and apoptosis during embryonic development.

Science.gov (United States)

Inglis-Broadgate, Suzanne L; Thomson, Rachel E; Pellicano, Francesca; Tartaglia, Michael A; Pontikis, Charlie C; Cooper, Jonathan D; Iwata, Tomoko

2005-03-01

Mice with the K644E kinase domain mutation in fibroblast growth factor receptor 3 (Fgfr3) (EIIa;Fgfr3(+/K644E)) exhibited a marked enlargement of the brain. The brain size was increased as early as E11.5, not secondary to the possible effect of Fgfr3 activity in the skeleton. Furthermore, the mutant brains showed a dramatic increase in cortical thickness, a phenotype opposite to that in FGF2 knockout mice. Despite this increased thickness, cortical layer formation was largely unaffected and no cortical folding was observed during embryonic days 11.5-18.5 (E11.5-E18.5). Measurement of cortical thickness revealed an increase of 38.1% in the EIIa;Fgfr3(+/K644E) mice at E14.5 and the advanced appearance of the cortical plate was frequently observed at this stage. Unbiased stereological analysis revealed that the volume of the ventricular zone (VZ) was increased by more than two fold in the EIIa;Fgfr3(+/K644E) mutants at E14.5. A relatively mild increase in progenitor cell proliferation and a profound decrease in developmental apoptosis during E11.5-E14.5 most likely accounts for the dramatic increase in total telecephalic cell number. Taken together, our data suggest a novel function of Fgfr3 in controlling the development of the cortex, by regulating proliferation and apoptosis of cortical progenitors.

Optimal Location and Sizing of UPQC in Distribution Networks Using Differential Evolution Algorithm

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Seyed Abbas Taher

2012-01-01

Full Text Available Differential evolution (DE algorithm is used to determine optimal location of unified power quality conditioner (UPQC considering its size in the radial distribution systems. The problem is formulated to find the optimum location of UPQC based on an objective function (OF defined for improving of voltage and current profiles, reducing power loss and minimizing the investment costs considering the OF's weighting factors. Hence, a steady-state model of UPQC is derived to set in forward/backward sweep load flow. Studies are performed on two IEEE 33-bus and 69-bus standard distribution networks. Accuracy was evaluated by reapplying the procedures using both genetic (GA and immune algorithms (IA. Comparative results indicate that DE is capable of offering a nearer global optimal in minimizing the OF and reaching all the desired conditions than GA and IA.

Evolution of oxytocin pathways in the brain of vertebrates

Directory of Open Access Journals (Sweden)

H. Sophie Knobloch

2014-02-01

Full Text Available The central oxytocin system transformed tremendously during the evolution, thereby adapting to the expanding properties of species. In more basal vertebrates (paraphyletic taxon Anamnia, which includes agnathans, fish and amphibians, magnocellular neurosecretory neurons producing oxytocin, vasopressin and their homologs reside in the wall of the third ventricle of the hypothalamus composing a single hypothalamic structure, the preoptic nucleus. This nucleus further diverged in advanced vertebrates (monophyletic taxon Amniota, which includes reptiles, birds and mammals into the paraventricular and supraoptic nuclei with accessory nuclei between them. The individual magnocellular neurons underwent a process of transformation from primitive uni- or bipolar neurons into highly differentiated neurons. Due to these microanatomical and cytological changes, the ancient release modes of oxytocin into the cerebrospinal fluid were largely replaced by vascular release. However, the most fascinating feature of the progressive transformations of the oxytocin system has been the expansion of oxytocin axonal projections to forebrain regions. In the present review we provide a background on these evolutionary advancements. Furthermore, we draw attention to the non-synaptic axonal release in small and defined brain regions with the aim to clearly distinguish this way of oxytocin action from the classical synaptic transmission on one side and from dendritic release followed by a global diffusion on the other side. Finally, we will summarize the effects of oxytocin and its homologs on pro-social reproductive behaviors in representatives of the phylogenetic tree and will propose anatomically plausible pathways of oxytocin release contributing to these behaviors in basal vertebrates and amniots.

Evolution of brains and behavior for optimal foraging: A tale of two predators

Science.gov (United States)

Catania, Kenneth C.

2012-01-01

Star-nosed moles and tentacled snakes have exceptional mechanosensory systems that illustrate a number of general features of nervous system organization and evolution. Star-nosed moles use the star for active touch—rapidly scanning the environment with the nasal rays. The star has the densest concentration of mechanoreceptors described for any mammal, with a central tactile fovea magnified in anatomically visible neocortical modules. The somatosensory system parallels visual system organization, illustrating general features of high-resolution sensory representations. Star-nosed moles are the fastest mammalian foragers, able to identify and eat small prey in 120 ms. Optimal foraging theory suggests that the star evolved for profitably exploiting small invertebrates in a competitive wetland environment. The tentacled snake’s facial appendages are superficially similar to the mole’s nasal rays, but they have a very different function. These snakes are fully aquatic and use tentacles for passive detection of nearby fish. Trigeminal afferents respond to water movements and project tentacle information to the tectum in alignment with vision, illustrating a general theme for the integration of different sensory modalities. Tentacled snakes act as rare enemies, taking advantage of fish C-start escape responses by startling fish toward their strike—often aiming for the future location of escaping fish. By turning fish escapes to their advantage, snakes increase strike success and reduce handling time with head-first captures. The latter may, in turn, prevent snakes from becoming prey when feeding. Findings in these two unusual predators emphasize the importance of a multidisciplinary approach for understanding the evolution of brains and behavior. PMID:22723352

Science & Society seminar: Evolution is not only a story of genes

CERN Multimedia

2002-01-01

Memes are behaviours and ideas copied from person to person by imitation. These include songs, habits, skills, inventions and ways of doing things. Darwinian evolutionary theory, which holds that genes control the traits of organisms, has traditionally explained human nature. Susan Blackmore offers a new look at evolution, and considers evolving memes as well as genes. This will be the subject of the next Science and Society seminar, 'The evolution of Meme machines', that will take place on Thursday 24 October. According to the meme idea, everything changed in human evolution when imitation first appeared because imitation let loose a new replicator, the meme. Since that time, two replicators have been driving human evolution, not one. This is why humans have such big brains, and why they alone produce and understand grammatical language, sing, dance, wear clothes and have complex cumulative cultures. Unlike other brains, human brains had to solve the problem of choosing which memes to imitate. In other wor...

The mating brain: early maturing sneaker males maintain investment into the brain also under fast body growth in Atlantic salmon (Salmo salar).

Science.gov (United States)

Kotrschal, Alexander; Trombley, Susanne; Rogell, Björn; Brannström, Ioana; Foconi, Eric; Schmitz, Monika; Kolm, Niclas

It has been suggested that mating behaviours require high levels of cognitive ability. However, since investment into mating and the brain both are costly features, their relationship is likely characterized by energetic trade-offs. Empirical data on the subject remains equivocal. We investigated if early sexual maturation was associated with brain development in Atlantic salmon ( Salmo salar ), in which males can either stay in the river and sexually mature at a small size (sneaker males) or migrate to the sea and delay sexual maturation until they have grown much larger (anadromous males). Specifically, we tested how sexual maturation may induce plastic changes in brain development by rearing juveniles on either natural or ad libitum feeding levels. After their first season we compared brain size and brain region volumes across both types of male mating tactics and females. Body growth increased greatly across both male mating tactics and females during ad libitum feeding as compared to natural feeding levels. However, despite similar relative increases in body size, early maturing sneaker males maintained larger relative brain size during ad libitum feeding levels as compared to anadromous males and females. We also detected several differences in the relative size of separate brain regions across feeding treatments, sexes and mating strategies. For instance, the relative size of the cognitive centre of the brain, the telencephalon, was largest in sneaker males. Our data support that a large relative brain size is maintained in individuals that start reproduction early also during fast body growth. We propose that the cognitive demands during complex mating behaviours maintain a high level of investment into brain development in reproducing individuals.

A fish is not a fish: patterns in fatty acid composition of aquatic food may have had implications for hominin evolution.

Science.gov (United States)

Joordens, Josephine C A; Kuipers, Remko S; Wanink, Jan H; Muskiet, Frits A J

2014-12-01

From c. 2 Ma (millions of years ago) onwards, hominin brain size and cognition increased in an unprecedented fashion. The exploitation of high-quality food resources, notably from aquatic ecosystems, may have been a facilitator or driver of this phenomenon. The aim of this study is to contribute to the ongoing debate on the possible role of aquatic resources in hominin evolution by providing a more detailed nutritional context. So far, the debate has focused on the relative importance of terrestrial versus aquatic resources while no distinction has been made between different types of aquatic resources. Here we show that Indian Ocean reef fish and eastern African lake fish yield on average similarly high amounts of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (AA). Hence a shift from exploiting tropical marine to freshwater ecosystems (or vice versa) would entail no material difference in dietary long-chain polyunsaturated fatty acid (LC-PUFA) availability. However, a shift to marine ecosystems would likely mean a major increase in access to brain-selective micronutrients such as iodine. Fatty fish from marine temperate/cold waters yield twice as much DHA and four times as much EPA as tropical fish, demonstrating that a latitudinal shift in exploitation of African coastal ecosystems could constitute a significant difference in LC-PUFA availability with possible implications for brain development and functioning. We conclude that exploitation of aquatic food resources could have facilitated the initial moderate hominin brain increase as observed in fossils dated to c. 2 Ma, but not the exceptional brain increase in later stages of hominin evolution. We propose that the significant expansion in hominin brain size and cognition later on may have been aided by strong directional selecting forces such as runaway sexual selection of intelligence, and nutritionally supported by exploitation of high-quality food resources in stable and

Stellar evolution

CERN Document Server

Meadows, A J

2013-01-01

Stellar Evolution, Second Edition covers the significant advances in the understanding of birth, life, and death of stars.This book is divided into nine chapters and begins with a description of the characteristics of stars according to their brightness, distance, size, mass, age, and chemical composition. The next chapters deal with the families, structure, and birth of stars. These topics are followed by discussions of the chemical composition and the evolution of main-sequence stars. A chapter focuses on the unique features of the sun as a star, including its evolution, magnetic fields, act

Archeological insights into hominin cognitive evolution.

Science.gov (United States)

Wynn, Thomas; Coolidge, Frederick L

2016-07-01

How did the human mind evolve? How and when did we come to think in the ways we do? The last thirty years have seen an explosion in research related to the brain and cognition. This research has encompassed a range of biological and social sciences, from epigenetics and cognitive neuroscience to social and developmental psychology. Following naturally on this efflorescence has been a heightened interest in the evolution of the brain and cognition. Evolutionary scholars, including paleoanthropologists, have deployed the standard array of evolutionary methods. Ethological and experimental evidence has added significantly to our understanding of nonhuman brains and cognition, especially those of nonhuman primates. Studies of fossil brains through endocasts and sophisticated imaging techniques have revealed evolutionary changes in gross neural anatomy. Psychologists have also gotten into the game through application of reverse engineering to experimentally based descriptions of cognitive functions. For hominin evolution, there is another rich source of evidence of cognition, the archeological record. Using the methods of Paleolithic archeology and the theories and models of cognitive science, evolutionary cognitive archeology documents developments in the hominin mind that would otherwise be inaccessible. © 2016 Wiley Periodicals, Inc.

Computational neuroanatomy using brain deformations: From brain parcellation to multivariate pattern analysis and machine learning.

Science.gov (United States)

Davatzikos, Christos

2016-10-01

The past 20 years have seen a mushrooming growth of the field of computational neuroanatomy. Much of this work has been enabled by the development and refinement of powerful, high-dimensional image warping methods, which have enabled detailed brain parcellation, voxel-based morphometric analyses, and multivariate pattern analyses using machine learning approaches. The evolution of these 3 types of analyses over the years has overcome many challenges. We present the evolution of our work in these 3 directions, which largely follows the evolution of this field. We discuss the progression from single-atlas, single-registration brain parcellation work to current ensemble-based parcellation; from relatively basic mass-univariate t-tests to optimized regional pattern analyses combining deformations and residuals; and from basic application of support vector machines to generative-discriminative formulations of multivariate pattern analyses, and to methods dealing with heterogeneity of neuroanatomical patterns. We conclude with discussion of some of the future directions and challenges. Copyright © 2016. Published by Elsevier B.V.

Transcranial brain stimulation: closing the loop between brain and stimulation

DEFF Research Database (Denmark)

Karabanov, Anke; Thielscher, Axel; Siebner, Hartwig Roman

2016-01-01

-related and state-related variability. Fluctuations in brain-states can be traced online with functional brain imaging and inform the timing or other settings of transcranial brain stimulation. State-informed open-loop stimulation is aligned to the expression of a predefined brain state, according to prespecified......PURPOSE OF REVIEW: To discuss recent strategies for boosting the efficacy of noninvasive transcranial brain stimulation to improve human brain function. RECENT FINDINGS: Recent research exposed substantial intra- and inter-individual variability in response to plasticity-inducing transcranial brain...... stimulation. Trait-related and state-related determinants contribute to this variability, challenging the standard approach to apply stimulation in a rigid, one-size-fits-all fashion. Several strategies have been identified to reduce variability and maximize the plasticity-inducing effects of noninvasive...

When problem size matters: differential effects of brain stimulation on arithmetic problem solving and neural oscillations.

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Bruno Rütsche

Full Text Available The problem size effect is a well-established finding in arithmetic problem solving and is characterized by worse performance in problems with larger compared to smaller operand size. Solving small and large arithmetic problems has also been shown to involve different cognitive processes and distinct electroencephalography (EEG oscillations over the left posterior parietal cortex (LPPC. In this study, we aimed to provide further evidence for these dissociations by using transcranial direct current stimulation (tDCS. Participants underwent anodal (30min, 1.5 mA, LPPC and sham tDCS. After the stimulation, we recorded their neural activity using EEG while the participants solved small and large arithmetic problems. We found that the tDCS effects on performance and oscillatory activity critically depended on the problem size. While anodal tDCS improved response latencies in large arithmetic problems, it decreased solution rates in small arithmetic problems. Likewise, the lower-alpha desynchronization in large problems increased, whereas the theta synchronization in small problems decreased. These findings reveal that the LPPC is differentially involved in solving small and large arithmetic problems and demonstrate that the effects of brain stimulation strikingly differ depending on the involved neuro-cognitive processes.

Novel insights into early neuroanatomical evolution in penguins from the oldest described penguin brain endocast.

Science.gov (United States)

Proffitt, J V; Clarke, J A; Scofield, R P

2016-08-01

Digital methodologies for rendering the gross morphology of the brain from X-ray computed tomography data have expanded our current understanding of the origin and evolution of avian neuroanatomy and provided new perspectives on the cognition and behavior of birds in deep time. However, fossil skulls germane to extracting digital endocasts from early stem members of extant avian lineages remain exceptionally rare. Data from early-diverging species of major avian subclades provide key information on ancestral morphologies in Aves and shifts in gross neuroanatomical structure that have occurred within those groups. Here we describe data on the gross morphology of the brain from a mid-to-late Paleocene penguin fossil from New Zealand. This most basal and geochronologically earliest-described endocast from the penguin clade indicates that described neuroanatomical features of early stem penguins, such as lower telencephalic lateral expansion, a relatively wider cerebellum, and lack of cerebellar folding, were present far earlier in penguin history than previously inferred. Limited dorsal expansion of the wulst in the new fossil is a feature seen in outgroup waterbird taxa such as Gaviidae (Loons) and diving Procellariiformes (Shearwaters, Diving Petrels, and allies), indicating that loss of flight may not drastically affect neuroanatomy in diving taxa. Wulst enlargement in the penguin lineage is first seen in the late Eocene, at least 25 million years after loss of flight and cooption of the flight stroke for aquatic diving. Similar to the origin of avian flight, major shifts in gross brain morphology follow, but do not appear to evolve quickly after, acquisition of a novel locomotor mode. Enlargement of the wulst shows a complex pattern across waterbirds, and may be linked to sensory modifications related to prey choice and foraging strategy. © 2016 Anatomical Society.

Has Human Evolution Stopped?

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Alan R. Templeton

2010-07-01

Full Text Available It has been argued that human evolution has stopped because humans now adapt to their environment via cultural evolution and not biological evolution. However, all organisms adapt to their environment, and humans are no exception. Culture defines much of the human environment, so cultural evolution has actually led to adaptive evolution in humans. Examples are given to illustrate the rapid pace of adaptive evolution in response to cultural innovations. These adaptive responses have important implications for infectious diseases, Mendelian genetic diseases, and systemic diseases in current human populations. Moreover, evolution proceeds by mechanisms other than natural selection. The recent growth in human population size has greatly increased the reservoir of mutational variants in the human gene pool, thereby enhancing the potential for human evolution. The increase in human population size coupled with our increased capacity to move across the globe has induced a rapid and ongoing evolutionary shift in how genetic variation is distributed within and among local human populations. In particular, genetic differences between human populations are rapidly diminishing and individual heterozygosity is increasing, with beneficial health effects. Finally, even when cultural evolution eliminates selection on a trait, the trait can still evolve due to natural selection on other traits. Our traits are not isolated, independent units, but rather are integrated into a functional whole, so selection on one trait can cause evolution to occur on another trait, sometimes with mildly maladaptive consequences.

Why Grandmothers May Need Large Brains. (Commentary on Skoyles on Brain Expertise)

OpenAIRE

Humphrey, Nicholas

1999-01-01

Skoyles's case against human brain size being related to IQ is strong; but his case in favor of its being related to expertise is weak. I propose that the explanation for the evolutionary expansion of the human brain in fact lies far away, in the need to have a brain that could continue to function into old age.

Evolution of genome size and chromosome number in the carnivorous plant genus Genlisea (Lentibulariaceae), with a new estimate of the minimum genome size in angiosperms

Science.gov (United States)

Fleischmann, Andreas; Michael, Todd P.; Rivadavia, Fernando; Sousa, Aretuza; Wang, Wenqin; Temsch, Eva M.; Greilhuber, Johann; Müller, Kai F.; Heubl, Günther

2014-01-01

Background and Aims Some species of Genlisea possess ultrasmall nuclear genomes, the smallest known among angiosperms, and some have been found to have chromosomes of diminutive size, which may explain why chromosome numbers and karyotypes are not known for the majority of species of the genus. However, other members of the genus do not possess ultrasmall genomes, nor do most taxa studied in related genera of the family or order. This study therefore examined the evolution of genome sizes and chromosome numbers in Genlisea in a phylogenetic context. The correlations of genome size with chromosome number and size, with the phylogeny of the group and with growth forms and habitats were also examined. Methods Nuclear genome sizes were measured from cultivated plant material for a comprehensive sampling of taxa, including nearly half of all species of Genlisea and representing all major lineages. Flow cytometric measurements were conducted in parallel in two laboratories in order to compare the consistency of different methods and controls. Chromosome counts were performed for the majority of taxa, comparing different staining techniques for the ultrasmall chromosomes. Key Results Genome sizes of 15 taxa of Genlisea are presented and interpreted in a phylogenetic context. A high degree of congruence was found between genome size distribution and the major phylogenetic lineages. Ultrasmall genomes with 1C values of sections of the genus. The smallest known plant genomes were not found in G. margaretae, as previously reported, but in G. tuberosa (1C ≈ 61 Mbp) and some strains of G. aurea (1C ≈ 64 Mbp). Conclusions Genlisea is an ideal candidate model organism for the understanding of genome reduction as the genus includes species with both relatively large (∼1700 Mbp) and ultrasmall (∼61 Mbp) genomes. This comparative, phylogeny-based analysis of genome sizes and karyotypes in Genlisea provides essential data for selection of suitable species for comparative

Automatic Evolution of Multimodal Behavior with Multi-Brain HyperNEAT

DEFF Research Database (Denmark)

Schrum, Jacob; Lehman, Joel; Risi, Sebastian

2016-01-01

indirect encoding. A previous multimodal approach called situational policy geometry assumes that multiple brains benefit from being embedded within an explicit geometric space. However, this paper introduces HyperNEAT extensions for evolving many brains without assuming geometric relationships between...

Evolution of man in the light of molecular genetics: a review. Part I. Our evolutionary history and genomics.

Science.gov (United States)

Portin, Petter

2007-07-01

The discovery in the mid 1970s of efficient methods of DNA sequencing and their subsequent development into more and more rapid procedures followed by sequencing the genomes of many species, including man in 2001, revolutionised the whole of biology. Remarkably, new light could be cast on the evolutionary relations of different species, and the tempo and mode of evolution within a given species, notably man, could quantitatively be illuminated including ongoing evolution possibly involving also the size of the brains. This review is a short summary of the results of the molecular genetic investigations of human evolution including the time and place of the formation of our species, our evolutionary relation to the closest living species relatives as well as extinct forms of the genus Homo. The nature and amount of genetic polymorphism in man is also considered with special emphasis on the causes of this variation, and the role of natural selection in human evolution. A consensus about the mosaic nature of our genome and the rather dynamic structure of our ancestral population is gradually emerging. The modern gene pool has most likely been contributed to several different ancestral demes either before or after the emergence of the anatomically modern human phenotype in the extent that even the nature of the evolutionary lineage leading to the anatomically modern man as a distinct biological species is disputable. Regulation of the function of genes, as well as the evolution of brains will be dealt with in the second part of this review.

Brain shape in human microcephalics and Homo floresiensis.

Science.gov (United States)

Falk, Dean; Hildebolt, Charles; Smith, Kirk; Morwood, M J; Sutikna, Thomas; Jatmiko; Saptomo, E Wayhu; Imhof, Herwig; Seidler, Horst; Prior, Fred

2007-02-13

Because the cranial capacity of LB1 (Homo floresiensis) is only 417 cm(3), some workers propose that it represents a microcephalic Homo sapiens rather than a new species. This hypothesis is difficult to assess, however, without a clear understanding of how brain shape of microcephalics compares with that of normal humans. We compare three-dimensional computed tomographic reconstructions of the internal braincases (virtual endocasts that reproduce details of external brain morphology, including cranial capacities and shape) from a sample of 9 microcephalic humans and 10 normal humans. Discriminant and canonical analyses are used to identify two variables that classify normal and microcephalic humans with 100% success. The classification functions classify the virtual endocast from LB1 with normal humans rather than microcephalics. On the other hand, our classification functions classify a pathological H. sapiens specimen that, like LB1, represents an approximately 3-foot-tall adult female and an adult Basuto microcephalic woman that is alleged to have an endocast similar to LB1's with the microcephalic humans. Although microcephaly is genetically and clinically variable, virtual endocasts from our highly heterogeneous sample share similarities in protruding and proportionately large cerebella and relatively narrow, flattened orbital surfaces compared with normal humans. These findings have relevance for hypotheses regarding the genetic substrates of hominin brain evolution and may have medical diagnostic value. Despite LB1's having brain shape features that sort it with normal humans rather than microcephalics, other shape features and its small brain size are consistent with its assignment to a separate species.

Modeling of the evolution of bubble size distribution of gas-liquid flow inside a large vertical pipe. Influence of bubble coalescence and breakup models

International Nuclear Information System (INIS)

Liao, Yixiang; Lucas, Dirk

2011-01-01

The range of gas-liquid flow applications in today's technology is immensely wide. Important examples can be found in chemical reactors, boiling and condensation equipments as well as nuclear reactors. In gas-liquid flows, the bubble size distribution plays an important role in the phase structure and interfacial exchange behaviors. It is therefore necessary to take into account the dynamic change of the bubble size distribution to get good predictions in CFD. An efficient 1D Multi-Bubble-Size-Class Test Solver was introduced in Lucas et al. (2001) for the simulation of the development of the flow structure along a vertical pipe. The model considers a large number of bubble classes. It solves the radial profiles of liquid and gas velocities, bubble-size class resolved gas fraction profiles as well as turbulence parameters on basis of the bubble size distribution present at the given axial position. The evolution of the flow along the height is assumed to be solely caused by the progress of bubble coalescence and break-up resulting in a bubble size distribution changing in the axial direction. In this model, the bubble coalescence and breakup models are very important for reasonable predictions of the bubble size distribution. Many bubble coalescence and breakup models have been proposed in the literature. However, some obvious discrepancies exist in the models; for example, the daughter bubble size distributions are greatly different from different bubble breakup models, as reviewed in our previous publication (Liao and Lucas, 2009a; 2010). Therefore, it is necessary to compare and evaluate typical bubble coalescence and breakup models that have been commonly used in the literature. Thus, this work is aimed to make a comparison of several typical bubble coalescence and breakup models and to discuss in detail the ability of the Test Solver to predict the evolution of bubble size distribution. (orig.)

Surface Aging Effect on Tire/Pavement Noise Medium-Term Evolution in a Medium-Size City

Directory of Open Access Journals (Sweden)

Víctor F. Vázquez

2018-05-01

Full Text Available This paper presents the geo-referenced acoustical results obtained throughout the close proximity noise (CPX technique carried out on different urban sections included within the 2017 strategic noise mapping (Directive 2002/49/CE in Ciudad Real, a Spanish medium-sized city. The employed methodology quantifies the tire/pavement noise generated in the contact between the tire and the surface of the studied sections. Measurements were carried out in different research campaigns between 2008 and 2015 (medium-term evolution. They give valuable information about the pavement-aging effect on its surface characteristics. Throughout these years, the acoustic situation of these sections has worsened mainly due to surface damage and higher mean profile depth (MPD values, although the performance does not follow the same pattern in every section. The relationships between measured tire/pavement noise and theoretical environmental noise, just due to the geometric spreading of sound energy, is also studied in order to elaborate a simple rolling noise mapping and to assess the environmental noise evolution. Traffic noise plays the main role in the noise registered within the assessed sections, therefore, CPX assessment could be used by local authorities to take decisions regarding urban planning and traffic management, with the aim of reducing noise exposure from traffic.

Theoretical evaluation of accuracy in position and size of brain activity obtained by near-infrared topography

International Nuclear Information System (INIS)

Kawaguchi, Hiroshi; Hayashi, Toshiyuki; Kato, Toshinori; Okada, Eiji

2004-01-01

Near-infrared (NIR) topography can obtain a topographical distribution of the activated region in the brain cortex. Near-infrared light is strongly scattered in the head, and the volume of tissue sampled by a source-detector pair on the head surface is broadly distributed in the brain. This scattering effect results in poor resolution and contrast in the topographic image of the brain activity. In this study, a one-dimensional distribution of absorption change in a head model is calculated by mapping and reconstruction methods to evaluate the effect of the image reconstruction algorithm and the interval of measurement points for topographic imaging on the accuracy of the topographic image. The light propagation in the head model is predicted by Monte Carlo simulation to obtain the spatial sensitivity profile for a source-detector pair. The measurement points are one-dimensionally arranged on the surface of the model, and the distance between adjacent measurement points is varied from 4 mm to 28 mm. Small intervals of the measurement points improve the topographic image calculated by both the mapping and reconstruction methods. In the conventional mapping method, the limit of the spatial resolution depends upon the interval of the measurement points and spatial sensitivity profile for source-detector pairs. The reconstruction method has advantages over the mapping method which improve the results of one-dimensional analysis when the interval of measurement points is less than 12 mm. The effect of overlapping of spatial sensitivity profiles indicates that the reconstruction method may be effective to improve the spatial resolution of a two-dimensional reconstruction of topographic image obtained with larger interval of measurement points. Near-infrared topography with the reconstruction method potentially obtains an accurate distribution of absorption change in the brain even if the size of absorption change is less than 10 mm

Fresh Frozen Plasma Modulates Brain Gene Expression in a Swine Model of Traumatic Brain Injury and Shock

DEFF Research Database (Denmark)

Sillesen, Martin; Bambakidis, Ted; Dekker, Simone E

2017-01-01

BACKGROUND: Resuscitation with fresh frozen plasma (FFP) decreases brain lesion size and swelling in a swine model of traumatic brain injury and hemorrhagic shock. We hypothesized that brain gene expression profiles after traumatic brain injury and hemorrhagic shock would be modulated by FFP resu...

Dynamical Evolution of Ring-Satellite Systems

Science.gov (United States)

Ohtsuki, Keiji

2005-01-01

The goal of this research was to understand dynamical processes related to the evolution of size distribution of particles in planetary rings and application of theoretical results to explain features in the present rings of giant planets. We studied velocity evolution and accretion rates of ring particles in the Roche zone. We developed a new numerical code for the evolution of ring particle size distribution, which takes into account the above results for particle velocity evolution and accretion rates. We also studied radial diffusion rate of ring particles due to inelastic collisions and gravitational encounters. Many of these results can be also applied to dynamical evolution of a planetesimal disk. Finally, we studied rotation rates of moonlets and particles in planetary rings, which would influence the accretional evolution of these bodies. We describe our key accomplishments during the past three years in more detail in the following.

Development of the Young Brain

Medline Plus

Full Text Available ... brain involved in controlling our impulses, long range planning, judgment, decision making. Announcer: Imaging has shown by the time children reach the first grade the physical size of the brain is nearly complete. But what goes on within the brain is nothing short ...

Surface properties, more than size, limiting convective distribution of virus-sized particles and viruses in the central nervous system.

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Chen, Michael Y; Hoffer, Alan; Morrison, Paul F; Hamilton, John F; Hughes, Jeffrey; Schlageter, Kurt S; Lee, Jeongwu; Kelly, Brandon R; Oldfield, Edward H

2005-08-01

Achieving distribution of gene-carrying vectors is a major barrier to the clinical application of gene therapy. Because of the blood-brain barrier, the distribution of genetic vectors to the central nervous system (CNS) is even more challenging than delivery to other tissues. Direct intraparenchymal microinfusion, a minimally invasive technique, uses bulk flow (convection) to distribute suspensions of macromolecules widely through the extracellular space (convection-enhanced delivery [CED]). Although acute injection into solid tissue is often used for delivery of oligonucleotides, viruses, and liposomes, and there is preliminary evidence that certain of these large particles can spread through the interstitial space of the brain by the use of convection, the use of CED for distribution of viruses in the brain has not been systematically examined. That is the goal of this study. Investigators used a rodent model to examine the influence of size, osmolarity of buffering solutions, and surface coating on the volumetric distribution of virus-sized nanoparticles and viruses (adeno-associated viruses and adenoviruses) in the gray matter of the brain. The results demonstrate that channels in the extracellular space of gray matter in the brain are large enough to accommodate virus-sized particles and that the surface characteristics are critical determinants for distribution of viruses in the brain by convection. These results indicate that convective distribution can be used to distribute therapeutic viral vectors in the CNS.

The evolution of body size under environmental gradients in ectotherms: why should Bergmann's rule apply to lizards?

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Tregenza Tom

2008-02-01

Full Text Available Abstract Background The impact of environmental gradients on the evolution of life history traits is a central issue in macroecology and evolutionary biology. A number of hypotheses have been formulated to explain factors shaping patterns of variation in animal mass. One such example is Bergmann's rule, which predicts that body size will be positively correlated with latitude and elevation, and hence, with decreasing environmental temperatures. A generally accepted explanation for this phenotypic response is that as body mass increases, body surface area gets proportionally smaller, which contributes to reduced rates of heat-loss. Phylogenetic and non-phylogenetic evidence reveals that endotherms follow Bergmann's rule. In contrast, while previous non-phylogenetic studies supported this prediction in up to 75% of ectotherms, recent phylogenetic comparative analyses suggest that its validity for these organisms is controversial and less understood. Moreover, little attention has been paid to why some ectotherms conform to this rule, while others do not. Here, we investigate Bergmann's rule in the six main clades forming the Liolaemus genus, one of the largest and most environmentally diverse genera of terrestrial vertebrates. A recent study conducted on some species belonging to four of these six clades concluded that Liolaemus species follow Bergmann's rule, representing the only known phylogenetic support for this model in lizards. However, a later reassessment of this evidence, performed on one of the four analysed clades, produced contrasting conclusions. Results Our results fail to support Bergmann's rule in Liolaemus lizards. Non-phylogenetic and phylogenetic analyses showed that none of the studied clades experience increasing body size with increasing latitude and elevation. Conclusion Most physiological and behavioural processes in ectotherms depend directly upon their body temperature. In cold environments, adaptations to gain heat

Mathematical modeling of human glioma growth based on brain topological structures: study of two clinical cases.

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Cecilia Suarez

Full Text Available Gliomas are the most common primary brain tumors and yet almost incurable due mainly to their great invasion capability. This represents a challenge to present clinical oncology. Here, we introduce a mathematical model aiming to improve tumor spreading capability definition. The model consists in a time dependent reaction-diffusion equation in a three-dimensional spatial domain that distinguishes between different brain topological structures. The model uses a series of digitized images from brain slices covering the whole human brain. The Talairach atlas included in the model describes brain structures at different levels. Also, the inclusion of the Brodmann areas allows prediction of the brain functions affected during tumor evolution and the estimation of correlated symptoms. The model is solved numerically using patient-specific parametrization and finite differences. Simulations consider an initial state with cellular proliferation alone (benign tumor, and an advanced state when infiltration starts (malign tumor. Survival time is estimated on the basis of tumor size and location. The model is used to predict tumor evolution in two clinical cases. In the first case, predictions show that real infiltrative areas are underestimated by current diagnostic imaging. In the second case, tumor spreading predictions were shown to be more accurate than those derived from previous models in the literature. Our results suggest that the inclusion of differential migration in glioma growth models constitutes another step towards a better prediction of tumor infiltration at the moment of surgical or radiosurgical target definition. Also, the addition of physiological/psychological considerations to classical anatomical models will provide a better and integral understanding of the patient disease at the moment of deciding therapeutic options, taking into account not only survival but also life quality.

Sensory Evolution and Ecology of Early Turtles Revealed by Digital Endocranial Reconstructions

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Stephan Lautenschlager

2018-02-01

Full Text Available In the past few years, new fossil finds and novel methodological approaches have prompted intensive discussions about the phylogenetic affinities of turtles and rekindled the debate on their ecological origin, with very distinct scenarios, such as fossoriality and aquatic habitat occupation, proposed for the earliest stem-turtles. While research has focused largely on the origin of the anapsid skull and unique postcranial anatomy, little is known about the endocranial anatomy of turtles. Here, we provide 3D digital reconstructions and comparative descriptions of the brain, nasal cavity, neurovascular structures and endosseous labyrinth of Proganochelys quenstedti, one of the earliest stem-turtles, as well as other turtle taxa. Our results demonstrate that P. quenstedti retained a simple tube-like brain morphology with poorly differentiated regions and mediocre hearing and vision, but a well-developed olfactory sense. Endocast shape analysis indicates that an increase in size and regionalization of the brain took place in the course of turtle evolution, achieving an endocast diversity comparable to other amniote groups. Based on the new evidence presented herein, we further conclude that P. quenstedti was a highly terrestrial, but most likely not fossorial, taxon.

Both noncoding and protein-coding RNAs contribute to gene expression evolution in the primate brain.

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Babbitt, Courtney C; Fedrigo, Olivier; Pfefferle, Adam D; Boyle, Alan P; Horvath, Julie E; Furey, Terrence S; Wray, Gregory A

2010-01-18

Despite striking differences in cognition and behavior between humans and our closest primate relatives, several studies have found little evidence for adaptive change in protein-coding regions of genes expressed primarily in the brain. Instead, changes in gene expression may underlie many cognitive and behavioral differences. Here, we used digital gene expression: tag profiling (here called Tag-Seq, also called DGE:tag profiling) to assess changes in global transcript abundance in the frontal cortex of the brains of 3 humans, 3 chimpanzees, and 3 rhesus macaques. A substantial fraction of transcripts we identified as differentially transcribed among species were not assayed in previous studies based on microarrays. Differentially expressed tags within coding regions are enriched for gene functions involved in synaptic transmission, transport, oxidative phosphorylation, and lipid metabolism. Importantly, because Tag-Seq technology provides strand-specific information about all polyadenlyated transcripts, we were able to assay expression in noncoding intragenic regions, including both sense and antisense noncoding transcripts (relative to nearby genes). We find that many noncoding transcripts are conserved in both location and expression level between species, suggesting a possible functional role. Lastly, we examined the overlap between differential gene expression and signatures of positive selection within putative promoter regions, a sign that these differences represent adaptations during human evolution. Comparative approaches may provide important insights into genes responsible for differences in cognitive functions between humans and nonhuman primates, as well as highlighting new candidate genes for studies investigating neurological disorders.

The evolution of cerebrotypes in birds.

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Iwaniuk, Andrew N; Hurd, Peter L

2005-01-01

Multivariate analyses of brain composition in mammals, amphibians and fish have revealed the evolution of 'cerebrotypes' that reflect specific niches and/or clades. Here, we present the first demonstration of similar cerebrotypes in birds. Using principal component analysis and hierarchical clustering methods to analyze a data set of 67 species, we demonstrate that five main cerebrotypes can be recognized. One type is dominated by galliforms and pigeons, among other species, that all share relatively large brainstems, but can be further differentiated by the proportional size of the cerebellum and telencephalic regions. The second cerebrotype contains a range of species that all share relatively large cerebellar and small nidopallial volumes. A third type is composed of two species, the tawny frogmouth (Podargus strigoides) and an owl, both of which share extremely large Wulst volumes. Parrots and passerines, the principal members of the fourth group, possess much larger nidopallial, mesopallial and striatopallidal proportions than the other groups. The fifth cerebrotype contains species such as raptors and waterfowl that are not found at the extremes for any of the brain regions and could therefore be classified as 'generalist' brains. Overall, the clustering of species does not directly reflect the phylogenetic relationships among species, but there is a tendency for species within an order to clump together. There may also be a weak relationship between cerebrotype and developmental differences, but two of the main clusters contained species with both altricial and precocial developmental patterns. As a whole, the groupings do agree with behavioral and ecological similarities among species. Most notably, species that share similarities in locomotor behavior, mode of prey capture or cognitive ability are clustered together. The relationship between cerebrotype and behavior/ecology in birds suggests that future comparative studies of brain-behavior relationships

Ultrafast carrier dynamics unravel role of surface ligands and metal domain size on the photocatalytic hydrogen evolution efficiency of Au-tipped CdS nanorods: an ultrafast transient absorption spectroscopy study

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Ben-Shahar, Yuval; Kriegel, Ilka; Scotognella, Francesco; Waiskopf, Nir; Dal Conte, Stefano; Moretti, Luca; Cerullo, Giulio; Rabani, Eran; Banin, Uri

2017-02-01

Semiconductor-metal hybrid nanostructures are interesting materials for photocatalysis. Their tunable properties offer a highly controllable platform to design light-induced charge separation, a key to their function in photocatalytic water splitting. Hydrogen evolution quantum yields are influenced by factors as size, shape, material and morphology of the system, additionally the surface coating or the metal domain size play a dominant role. In this paper we present a study on a well-defined model system of Au-tipped CdS nanorods. We use transient absorption spectroscopy to get insights into the charge carrier dynamics after photoexcitation of the bandgap of CdS nanorods. The study of charge transfer processes combined with the hydrogen evolution efficiency unravels the effects of surface coating and the gold tip size on the photocatalytic efficiency. Differences in efficiency with various surface ligands are primarily ascribed to the effects of surface passivation. Surface trapping of charge carriers is competing with effective charge separation, a prerequisite for photocatalysis, leading to the observed lower hydrogen production quantum yields. Interestingly, non-monotonic hydrogen evolution efficiency with size of the gold tip is observed, resulting in an optimal metal domain size for the most efficient photocatalysis. These results are explained by the sizedependent interplay of the metal domain charging and the relative band-alignments. Taken together our findings are of major importance for the potential application of hybrid nanoparticles as photocatalysts.

Development of the Young Brain

Medline Plus

Full Text Available ... the frontal part of the brain involved in controlling our impulses, long range planning, judgment, decision making. Announcer: Imaging has shown by the time children reach the first grade the physical size of the brain is nearly complete. But what goes on within the brain is nothing short ...

Adaptive processes drive ecomorphological convergent evolution in antwrens (Thamnophilidae).

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Bravo, Gustavo A; Remsen, J V; Brumfield, Robb T

2014-10-01

Phylogenetic niche conservatism (PNC) and convergence are contrasting evolutionary patterns that describe phenotypic similarity across independent lineages. Assessing whether and how adaptive processes give origin to these patterns represent a fundamental step toward understanding phenotypic evolution. Phylogenetic model-based approaches offer the opportunity not only to distinguish between PNC and convergence, but also to determine the extent that adaptive processes explain phenotypic similarity. The Myrmotherula complex in the Neotropical family Thamnophilidae is a polyphyletic group of sexually dimorphic small insectivorous forest birds that are relatively homogeneous in size and shape. Here, we integrate a comprehensive species-level molecular phylogeny of the Myrmotherula complex with morphometric and ecological data within a comparative framework to test whether phenotypic similarity is described by a pattern of PNC or convergence, and to identify evolutionary mechanisms underlying body size and shape evolution. We show that antwrens in the Myrmotherula complex represent distantly related clades that exhibit adaptive convergent evolution in body size and divergent evolution in body shape. Phenotypic similarity in the group is primarily driven by their tendency to converge toward smaller body sizes. Differences in body size and shape across lineages are associated to ecological and behavioral factors. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

Grain size and microhardness evolution during annealing of a magnesium alloy processed by high-pressure torsion

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Livia Raquel C. Malheiros

2015-01-01

Full Text Available High-pressure torsion (HPT was used to impose severe plastic deformation on a magnesium alloy AZ31. The material was processed for 0.5, 1, 2, 3, 5 and 7 turns at room temperature under a pressure of 6.0 GPa. Samples were annealed for 1800 s at temperatures of 373 K, 423 K, 473 K, 573 K and 673 K. Microhardness tests and metallography were used to determine the evolution of strength and grain size as a function of the annealing temperature. The results show that recrystallization takes place at temperatures higher than 423 K. The annealing behavior is independent of the number of turns in HPT.

Correlation between Peripheral Levels of Brain-Derived Neurotrophic Factor and Hippocampal Volume in Children and Adolescents with Bipolar Disorder

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Tatiana Lauxen Peruzzolo

2015-01-01

Full Text Available Pediatric bipolar disorder (PBD is a serious mental disorder that affects the development and emotional growth of affected patients. The brain derived neurotrophic factor (BDNF is recognized as one of the possible markers of the framework and its evolution. Abnormalities in BDNF signaling in the hippocampus could explain the cognitive decline seen in patients with TB. Our aim with this study was to evaluate possible changes in hippocampal volume in children and adolescents with BD and associate them to serum BDNF. Subjects included 30 patients aged seven to seventeen years from the ProCAB (Program for Children and Adolescents with Bipolar Disorder. We observed mean right and left hippocampal volumes of 41910.55 and 41747.96 mm3, respectively. No statistically significant correlations between peripheral BDNF levels and hippocampal volumes were found. We believe that the lack of correlation observed in this study is due to the short time of evolution of BD in children and adolescents. Besides studies with larger sample sizes to confirm the present findings and longitudinal assessments, addressing brain development versus a control group and including drug-naive patients in different mood states may help clarify the role of BDNF in the brain changes consequent upon BD.

Qualitative and quantitative assessment of step size adaptation rules

DEFF Research Database (Denmark)

Krause, Oswin; Glasmachers, Tobias; Igel, Christian

2017-01-01

We present a comparison of step size adaptation methods for evolution strategies, covering recent developments in the field. Following recent work by Hansen et al. we formulate a concise list of performance criteria: a) fast convergence of the mean, b) near-optimal fixed point of the normalized s...... that cumulative step size adaptation (CSA) and twopoint adaptation (TPA) provide reliable estimates of the optimal step size. We further find that removing the evolution path of CSA still leads to a reliable algorithm without the computational requirements of CSA.......We present a comparison of step size adaptation methods for evolution strategies, covering recent developments in the field. Following recent work by Hansen et al. we formulate a concise list of performance criteria: a) fast convergence of the mean, b) near-optimal fixed point of the normalized...

Artificial Intelligence and brain.

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Shapshak, Paul

2018-01-01

From the start, Kurt Godel observed that computer and brain paradigms were considered on a par by researchers and that researchers had misunderstood his theorems. He hailed with displeasure that the brain transcends computers. In this brief article, we point out that Artificial Intelligence (AI) comprises multitudes of human-made methodologies, systems, and languages, and implemented with computer technology. These advances enhance development in the electron and quantum realms. In the biological realm, animal neurons function, also utilizing electron flow, and are products of evolution. Mirror neurons are an important paradigm in neuroscience research. Moreover, the paradigm shift proposed here - 'hall of mirror neurons' - is a potentially further productive research tactic. These concepts further expand AI and brain research.

The evolution of ferrite grain size in structural steels

International Nuclear Information System (INIS)

Hodgson, P.D.

1999-01-01

The refinement of the ferrite grain size is the main aim of modern thermomechanical processes for hot rolled steels. The ferrite grain size is determined by the composition, the state of the austenite at the point of transformation and the cooling rate through transformation. By adding microalloying additions of Ti for grain refinement and Nb to retard recrystallisation, it is possible to reduce the ferrite grain size to less than 5μm at moderate to high cooling rates. However, it is not possible under even the most extreme traditional controlled rolling and accelerated cooling conditions to produce an equiaxed ferrite grain size of less than 3μm. More recent work, though, involving rolling with high undercooling and friction conditions that lead to high shear, suggests that it is possible to produce microstructures in a single rolling pass with an average grain size less than 1μm. This appears to involve a dynamic (ie strain induced) transformation process. The current understanding of static and dynamic transformation and the resultant grain size is reviewed and areas requiring further research are highlighted

Comparing brain networks of different size and connectivity density using graph theory.

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Bernadette C M van Wijk

Full Text Available Graph theory is a valuable framework to study the organization of functional and anatomical connections in the brain. Its use for comparing network topologies, however, is not without difficulties. Graph measures may be influenced by the number of nodes (N and the average degree (k of the network. The explicit form of that influence depends on the type of network topology, which is usually unknown for experimental data. Direct comparisons of graph measures between empirical networks with different N and/or k can therefore yield spurious results. We list benefits and pitfalls of various approaches that intend to overcome these difficulties. We discuss the initial graph definition of unweighted graphs via fixed thresholds, average degrees or edge densities, and the use of weighted graphs. For instance, choosing a threshold to fix N and k does eliminate size and density effects but may lead to modifications of the network by enforcing (ignoring non-significant (significant connections. Opposed to fixing N and k, graph measures are often normalized via random surrogates but, in fact, this may even increase the sensitivity to differences in N and k for the commonly used clustering coefficient and small-world index. To avoid such a bias we tried to estimate the N,k-dependence for empirical networks, which can serve to correct for size effects, if successful. We also add a number of methods used in social sciences that build on statistics of local network structures including exponential random graph models and motif counting. We show that none of the here-investigated methods allows for a reliable and fully unbiased comparison, but some perform better than others.

Lutein and Brain Function

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John W. Erdman

2015-10-01

Full Text Available Lutein is one of the most prevalent carotenoids in nature and in the human diet. Together with zeaxanthin, it is highly concentrated as macular pigment in the foveal retina of primates, attenuating blue light exposure, providing protection from photo-oxidation and enhancing visual performance. Recently, interest in lutein has expanded beyond the retina to its possible contributions to brain development and function. Only primates accumulate lutein within the brain, but little is known about its distribution or physiological role. Our team has begun to utilize the rhesus macaque (Macaca mulatta model to study the uptake and bio-localization of lutein in the brain. Our overall goal has been to assess the association of lutein localization with brain function. In this review, we will first cover the evolution of the non-human primate model for lutein and brain studies, discuss prior association studies of lutein with retina and brain function, and review approaches that can be used to localize brain lutein. We also describe our approach to the biosynthesis of 13C-lutein, which will allow investigation of lutein flux, localization, metabolism and pharmacokinetics. Lastly, we describe potential future research opportunities.

Initial brain aging

DEFF Research Database (Denmark)

Thomsen, Kirsten; Yokota, Takashi; Hasan-Olive, Md Mahdi

2018-01-01

Brain aging is accompanied by declining mitochondrial respiration. We hypothesized that mitochondrial morphology and dynamics would reflect this decline. Using hippocampus and frontal cortex of a segmental progeroid mouse model lacking Cockayne syndrome protein B (CSB(m/m)) and C57Bl/6 (WT......) controls and comparing young (2-5 months) to middle-aged mice (13-14 months), we found that complex I-linked state 3 respiration (CI) was reduced at middle age in CSB(m/m) hippocampus, but not in CSB(m/m) cortex or WT brain. In hippocampus of both genotypes, mitochondrial size heterogeneity increased....... Mitochondrial DNA content was lower, and hypoxia-induced factor 1α mRNA was greater at both ages in CSB(m/m) compared to WT brain. Our findings show that decreased CI and increased mitochondrial size heterogeneity are highly associated and point to declining mitochondrial quality control as an initial event...

Toward Developmental Connectomics of the Human Brain

OpenAIRE

Cao, Miao; Huang, Hao; Peng, Yun; Dong, Qi; He, Yong

2016-01-01

Imaging connectomics based on graph theory has become an effective and unique methodological framework for studying structural and functional connectivity patterns of the developing brain. Normal brain development is characterized by continuous and significant network evolution throughout infancy, childhood, and adolescence, following specific maturational patterns. Disruption of these normal changes is associated with neuropsychiatric developmental disorders, such as autism spectrum disorder...

Towards Developmental Connectomics of the Human Brain

OpenAIRE

Miao eCao; Hao eHuang; Hao eHuang; Yun ePeng; Qi eDong; Yong eHe

2016-01-01

Imaging connectomics based on graph theory has become an effective and unique methodological framework for studying structural and functional connectivity patterns of the developing brain. Normal brain development is characterized by continuous and significant network evolution throughout infancy, childhood and adolescence, following specific maturational patterns. Disruption of these normal changes is associated with neuropsychiatric developmental disorders, such as autism spectrum disorders...

Development of the Young Brain

Medline Plus

Full Text Available ... 160; Watch on YouTube. Transcript Announcer: Parents and caregivers have always been fascinated with the development of ... size of the brain is nearly complete. But what goes on within the brain is nothing short ...

Mathematical modeling and comparison of protein size distribution in different plant, animal, fungal and microbial species reveals a negative correlation between protein size and protein number, thus providing insight into the evolution of proteomes

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Tiessen Axel

2012-02-01

Full Text Available Abstract Background The sizes of proteins are relevant to their biochemical structure and for their biological function. The statistical distribution of protein lengths across a diverse set of taxa can provide hints about the evolution of proteomes. Results Using the full genomic sequences of over 1,302 prokaryotic and 140 eukaryotic species two datasets containing 1.2 and 6.1 million proteins were generated and analyzed statistically. The lengthwise distribution of proteins can be roughly described with a gamma type or log-normal model, depending on the species. However the shape parameter of the gamma model has not a fixed value of 2, as previously suggested, but varies between 1.5 and 3 in different species. A gamma model with unrestricted shape parameter described best the distributions in ~48% of the species, whereas the log-normal distribution described better the observed protein sizes in 42% of the species. The gamma restricted function and the sum of exponentials distribution had a better fitting in only ~5% of the species. Eukaryotic proteins have an average size of 472 aa, whereas bacterial (320 aa and archaeal (283 aa proteins are significantly smaller (33-40% on average. Average protein sizes in different phylogenetic groups were: Alveolata (628 aa, Amoebozoa (533 aa, Fornicata (543 aa, Placozoa (453 aa, Eumetazoa (486 aa, Fungi (487 aa, Stramenopila (486 aa, Viridiplantae (392 aa. Amino acid composition is biased according to protein size. Protein length correlated negatively with %C, %M, %K, %F, %R, %W, %Y and positively with %D, %E, %Q, %S and %T. Prokaryotic proteins had a different protein size bias for %E, %G, %K and %M as compared to eukaryotes. Conclusions Mathematical modeling of protein length empirical distributions can be used to asses the quality of small ORFs annotation in genomic releases (detection of too many false positive small ORFs. There is a negative correlation between average protein size and total number of

Body size evolution in insular speckled rattlesnakes (Viperidae: Crotalus mitchellii.

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Jesse M Meik

2010-03-01

Full Text Available Speckled rattlesnakes (Crotalus mitchellii inhabit multiple islands off the coast of Baja California, Mexico. Two of the 14 known insular populations have been recognized as subspecies based primarily on body size divergence from putative mainland ancestral populations; however, a survey of body size variation from other islands occupied by these snakes has not been previously reported. We examined body size variation between island and mainland speckled rattlesnakes, and the relationship between body size and various island physical variables among 12 island populations. We also examined relative head size among giant, dwarfed, and mainland speckled rattlesnakes to determine whether allometric differences conformed to predictions of gape size (and indirectly body size evolving in response to shifts in prey size.Insular speckled rattlesnakes show considerable variation in body size when compared to mainland source subspecies. In addition to previously known instances of gigantism on Angel de la Guarda and dwarfism on El Muerto, various degrees of body size decrease have occurred frequently in this taxon, with dwarfed rattlesnakes occurring mostly on small, recently isolated, land-bridge islands. Regression models using the Akaike information criterion (AIC showed that mean SVL of insular populations was most strongly correlated with island area, suggesting the influence of selection for different body size optima for islands of different size. Allometric differences in head size of giant and dwarf rattlesnakes revealed patterns consistent with shifts to larger and smaller prey, respectively.Our data provide the first example of a clear relationship between body size and island area in a squamate reptile species; among vertebrates this pattern has been previously documented in few insular mammals. This finding suggests that selection for body size is influenced by changes in community dynamics that are related to graded differences in area over

Gene family size conservation is a good indicator of evolutionary rates.

Science.gov (United States)

Chen, Feng-Chi; Chen, Chiuan-Jung; Li, Wen-Hsiung; Chuang, Trees-Juen

2010-08-01

The evolution of duplicate genes has been a topic of broad interest. Here, we propose that the conservation of gene family size is a good indicator of the rate of sequence evolution and some other biological properties. By comparing the human-chimpanzee-macaque orthologous gene families with and without family size conservation, we demonstrate that genes with family size conservation evolve more slowly than those without family size conservation. Our results further demonstrate that both family expansion and contraction events may accelerate gene evolution, resulting in elevated evolutionary rates in the genes without family size conservation. In addition, we show that the duplicate genes with family size conservation evolve significantly more slowly than those without family size conservation. Interestingly, the median evolutionary rate of singletons falls in between those of the above two types of duplicate gene families. Our results thus suggest that the controversy on whether duplicate genes evolve more slowly than singletons can be resolved when family size conservation is taken into consideration. Furthermore, we also observe that duplicate genes with family size conservation have the highest level of gene expression/expression breadth, the highest proportion of essential genes, and the lowest gene compactness, followed by singletons and then by duplicate genes without family size conservation. Such a trend accords well with our observations of evolutionary rates. Our results thus point to the importance of family size conservation in the evolution of duplicate genes.

Function and regulation of AUTS2, a gene implicated in autism and human evolution.

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Nir Oksenberg

Full Text Available Nucleotide changes in the AUTS2 locus, some of which affect only noncoding regions, are associated with autism and other neurological disorders, including attention deficit hyperactivity disorder, epilepsy, dyslexia, motor delay, language delay, visual impairment, microcephaly, and alcohol consumption. In addition, AUTS2 contains the most significantly accelerated genomic region differentiating humans from Neanderthals, which is primarily composed of noncoding variants. However, the function and regulation of this gene remain largely unknown. To characterize auts2 function, we knocked it down in zebrafish, leading to a smaller head size, neuronal reduction, and decreased mobility. To characterize AUTS2 regulatory elements, we tested sequences for enhancer activity in zebrafish and mice. We identified 23 functional zebrafish enhancers, 10 of which were active in the brain. Our mouse enhancer assays characterized three mouse brain enhancers that overlap an ASD-associated deletion and four mouse enhancers that reside in regions implicated in human evolution, two of which are active in the brain. Combined, our results show that AUTS2 is important for neurodevelopment and expose candidate enhancer sequences in which nucleotide variation could lead to neurological disease and human-specific traits.

The Evolution of Learning Mechanisms.

Science.gov (United States)

Garcia, John; Garcia y Robertson, Rodrigo

This paper introduces seven principles of learning, enduring over the last five centuries of psychological thought, to discuss the evolution of the "Biophyche" (the brain in action) in the development of humans and other large organisms. It describes the conditioning theories of Darwin, Pavlov, and Thorndike and critically reviews the…

Brain edema associated with unruptured brain arteriovenous malformations

International Nuclear Information System (INIS)

Kim, Bum-soo; Sarma, Dipanka; Lee, Seon-Kyu; ter Brugge, Karel G.

2009-01-01

Brain edema in unruptured brain arteriovenous malformations (AVMs) is rare; this study examines (1) its frequency and clinical presentation, (2) imaging findings with emphasis on venous drainage abnormalities, and (3) implications of these findings on natural history and management. Presentation and imaging features of all unruptured brain AVMs were prospectively collected in our brain AVM database. Neurological findings, size, location, venous drainage pattern, presence of venous thrombosis, ectasia, or stenosis, and brain edema were specifically recorded. Treatment details of all patients with brain edema and their clinical and imaging follow-up were reviewed. Finally, a comparison was made between patients with and without edema. Brain edema was found in 13/329 unruptured brain AVMs (3.9%). Neurological deficit (46.2%), venous thrombosis (38.5%), venous ectasia (84.6%), stenosis (38.5%), and contrast stagnation in the draining veins (84.6%) were more frequent in patients with brain edema than without edema. Eight patients with brain edema received specific treatment (embolization = 5, surgery = 2, radiosurgery = 1). Clinical features correlated well with change in degree of edema in six. Three of five embolized patients were stable or showed improvement after the procedure. On follow-up, however, intracranial hemorrhage developed in three. Brain edema in unruptured brain AVMs is rare, 3.9% in this series. Venous outflow abnormalities are frequently associated and appear to contribute to the development of edema. Progressive nonhemorrhagic symptoms are also associated, with a possible increased risk of hemorrhage. Palliative embolization arrests the nonhemorrhagic symptoms in selected patients, although it may not have an effect on hemorrhagic risk. (orig.)

The size and burden of mental disorders and other disorders of the brain in Europe 2010.

Science.gov (United States)

Wittchen, H U; Jacobi, F; Rehm, J; Gustavsson, A; Svensson, M; Jönsson, B; Olesen, J; Allgulander, C; Alonso, J; Faravelli, C; Fratiglioni, L; Jennum, P; Lieb, R; Maercker, A; van Os, J; Preisig, M; Salvador-Carulla, L; Simon, R; Steinhausen, H-C

2011-09-01

, early retirement and treatment rates due to mental disorders, rates in the community have not increased with a few exceptions (i.e. dementia). There were also no consistent indications of improvements with regard to low treatment rates, delayed treatment provision and grossly inadequate treatment. Disability: Disorders of the brain and mental disorders in particular, contribute 26.6% of the total all cause burden, thus a greater proportion as compared to other regions of the world. The rank order of the most disabling diseases differs markedly by gender and age group; overall, the four most disabling single conditions were: depression, dementias, alcohol use disorders and stroke. In every year over a third of the total EU population suffers from mental disorders. The true size of "disorders of the brain" including neurological disorders is even considerably larger. Disorders of the brain are the largest contributor to the all cause morbidity burden as measured by DALY in the EU. No indications for increasing overall rates of mental disorders were found nor of improved care and treatment since 2005; less than one third of all cases receive any treatment, suggesting a considerable level of unmet needs. We conclude that the true size and burden of disorders of the brain in the EU was significantly underestimated in the past. Concerted priority action is needed at all levels, including substantially increased funding for basic, clinical and public health research in order to identify better strategies for improved prevention and treatment for disorders of the brain as the core health challenge of the 21st century. Copyright © 2011. Published by Elsevier B.V.

Genes, evolution and intelligence.

Science.gov (United States)

Bouchard, Thomas J

2014-11-01

I argue that the g factor meets the fundamental criteria of a scientific construct more fully than any other conception of intelligence. I briefly discuss the evidence regarding the relationship of brain size to intelligence. A review of a large body of evidence demonstrates that there is a g factor in a wide range of species and that, in the species studied, it relates to brain size and is heritable. These findings suggest that many species have evolved a general-purpose mechanism (a general biological intelligence) for dealing with the environments in which they evolved. In spite of numerous studies with considerable statistical power, we know of very few genes that influence g and the effects are very small. Nevertheless, g appears to be highly polygenic. Given the complexity of the human brain, it is not surprising that that one of its primary faculties-intelligence-is best explained by the near infinitesimal model of quantitative genetics.

Middle cerebral artery occlusion in Macaca fascicularis: acute and chronic stroke evolution.

Science.gov (United States)

D'Arceuil, Helen E; Duggan, Michael; He, Julian; Pryor, Johnny; de Crespigny, Alex

2006-04-01

An intravascular stroke model designed for magnetic resonance imaging was developed in Macaca fascicularis (M. fascicularis) to characterize serial stroke lesion evolution. This model produces a range of stroke lesion sizes which closely mimics human stroke evolution. This paper describes the care of animals undergoing this stroke procedure, the range of outcomes we experienced and the cause of mortality in this model. Anesthesia was induced with atropine and ketamine and maintained with isoflurane or propofol. Non-invasive blood pressure, oxygen saturation, heart rate, respiration rate, temperature and end tidal CO2 were monitored continuously. The stroke was created by occluding a distal branch of the middle cerebral artery. During catheter placement animals were heparinized and vasospasm was minimized using verapamil. Anesthetic induction and maintenance were smooth. Animals with small strokes showed very rapid recovery, were able to ambulate and self-feed within 2 hours of recovery. Animals with strokes of >or=4% of the hemispheric volume required lengthy observation during recovery and parenteral nutrition. Large strokes resulted in significant brain edema, herniation and brainstem compression. Intracerebral hemorrhage and or subarachnoid hemorrhage coupled with a stroke of any size was acutely fatal. In the absence of an effective acute stroke therapy, the spectrum of outcomes seen in our primate model is very similar to that observed in human stroke patients.

Brain size and white matter content of cerebrospinal tracts determine the upper cervical cord area: evidence from structural brain MRI

Energy Technology Data Exchange (ETDEWEB)

Engl, Christina; Arsic, Milan; Boucard, Christine C.; Biberacher, Viola; Nunnemann, Sabine; Muehlau, Mark [Technische Universitaet Muenchen, Department of Neurology, Klinikum rechts der Isar, Munich (Germany); Technische Universitaet Muenchen, TUM-Neuroimaging Center, Klinikum rechts der Isar, Munich (Germany); Schmidt, Paul [Technische Universitaet Muenchen, Department of Neurology, Klinikum rechts der Isar, Munich (Germany); Ludwig-Maximilians-University Muenchen, Department of Statistics, Munich (Germany); Roettinger, Michael [Technische Universitaet Muenchen, Department of Radiology, Klinikum rechts der Isar, Munich (Germany); Muenchner Institut fuer Neuroradiologie, Munich (Germany); Etgen, Thorleif [Technische Universitaet Muenchen, Department of Neurology, Klinikum rechts der Isar, Munich (Germany); Klinikum Traunstein, Department of Neurology, Traunstein (Germany); Koutsouleris, Nikolaos; Meisenzahl, Eva M. [Ludwig-Maximilians-Universitaet Muenchen, Department of Psychiatry and Psychotherapy, Munich (Germany); Reiser, Maximilian [Ludwig-Maximilians-Universitaet, Department of Radiology, Munich (Germany)

2013-08-15

Measurement of the upper cervical cord area (UCCA) from brain MRI may be an effective way to quantify spinal cord involvement in neurological disorders such as multiple sclerosis. However, knowledge on the determinants of UCCA in healthy controls (HCs) is limited. In two cohorts of 133 and 285 HCs, we studied the influence of different demographic, body-related, and brain-related parameters on UCCA by simple and partial correlation analyses as well as by voxel-based morphometry (VBM) across both cerebral gray matter (GM) and white matter (WM). First, we confirmed the known but moderate effect of age on UCCA in the older cohort. Second, we studied the correlation of UCCA with sex, body height, and total intracranial volume (TIV). TIV was the only variable that correlated significantly with UCCA after correction for the other variables. Third, we studied the correlation of UCCA with brain-related parameters. Brain volume correlated stronger with UCCA than TIV. Both volumes of the brain tissue compartments GM and WM correlated with UCCA significantly. WM volume explained variance of UCCA after correction for GM volume, whilst the opposite was not observed. Correspondingly, VBM did not yield any brain region, whose GM content correlated significantly with UCCA, whilst cerebral WM content of cerebrospinal tracts strongly correlated with UCCA. This latter effect increased along a craniocaudal gradient. UCCA is mainly determined by brain volume as well as by WM content of cerebrospinal tracts. (orig.)

On the Relationship between Pollen Size and Genome Size

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Charles A. Knight

2010-01-01

Full Text Available Here we test whether genome size is a predictor of pollen size. If it were, inferences of ancient genome size would be possible using the abundant paleo-palynolgical record. We performed regression analyses across 464 species of pollen width and genome size. We found a significant positive trend. However, regression analysis using phylogentically independent contrasts did not support the correlated evolution of these traits. Instead, a large split between angiosperms and gymnosperms for both pollen width and genome size was revealed. Sister taxa were not more likely to show a positive contrast when compared to deeper nodes. However, significantly more congeneric species had a positive trend than expected by chance. These results may reflect the strong selection pressure for pollen to be small. Also, because pollen grains are not metabolically active when measured, their biology is different than other cells which have been shown to be strongly related to genome size, such as guard cells. Our findings contrast with previously published research. It was our hope that pollen size could be used as a proxy for inferring the genome size of ancient species. However, our results suggest pollen is not a good candidate for such endeavors.

Evidence for the Higher Importance of Signal Size Over Body Size in Aposematic Signaling in Insects

OpenAIRE

Remmel, Triinu; Tammarub, Toomas

2011-01-01

To understand the evolution of warning coloration, it is important to distinguish between different aspects of conspicuous color patterns. As an example, both pattern element size and body size of prey have been shown to enhance the effectiveness of warning signals. However, it is unclear whether the effect of body size is merely a side effect of proportionally increasing pattern elements, or if there is an effect of body size per se. These possibilities were evaluated by offering different s...

Preliminary notes on brain weight variation across labrid fish species with different levels of cooperative behaviour

Institute of Scientific and Technical Information of China (English)

Marta C.SOARES; Gon(c)alo I.ANDR(E); José R.PAULA

2015-01-01

Brain size and weight vary tremendously in the animal kingdom.It has been suggested that brain structural development must evolve balanced between the advantages of dealing with greater social challenges and the energetic costs of maintaining and developing larger brains.Here we ask if interspecific differences in cooperative behaviour (i.e.cleaning behaviour) are related to brain weight variations in four close-related species of Labrid fish:two are obligatory cleanerfish throughout their entire life (Labroides dimidiatus and L.bicolor),one facultative cleaner fish Labropsis australis and one last species that never engage in cleaning Labrichthys unilineatus.We first search for the link between the rate of species' cooperation and its relative brain weight,and finally,if the degree of social complexity and cooperation are reflected in the weight of its major brain substructures.Overall,no differences were found in relative brain weight (in relation to body weight) across species.Fine-scale differences were solely demonstrated for the facultative cleaner L.australis,at the brainstem level.Furthermore,data visual examination indicates that the average cerebellum and brainstem weights appear to be larger for L.dimidiatus.Because variation was solely found at specific brain areas (such as cerebellum and brainstem) and not for the whole brain weight values,it suggests that species social-ecological and cognitive demands may be directly contributing to a selective investment in relevant brain areas.This study provides first preliminary evidence that links potential differences in cognitive ability in cooperative behaviour to how these may mediate the evolution of brain structural development in non-mammal vertebrate groups [Current Zoology 61 (2):274-280,2015].

Dyslexia singular brain

International Nuclear Information System (INIS)

Habis, M.; Robichon, F.; Demonet, J.F.

1996-01-01

Of late ten years, neurologists are studying the brain of the dyslectics. The cerebral imagery (NMR imaging, positron computed tomography) has allowed to confirm the anatomical particularities discovered by some of them: asymmetry default of cerebral hemispheres, size abnormally large of the white substance mass which connect the two hemispheres. The functional imagery, when visualizing this singular brain at work, allows to understand why it labors to reading. (O.M.)

Galaxy Size Evolution at High Redshift and Surface Brightness Selection Effects: Constraints from the Hubble Ultra Deep Field

Science.gov (United States)

Bouwens, R. J.; Illingworth, G. D.; Blakeslee, J. P.; Broadhurst, T. J.; Franx, M.

2004-08-01

We use the exceptional depth of the Ultra Deep Field (UDF) and UDF-parallel Advanced Camera for Surveys fields to study the sizes of high-redshift (z~2-6) galaxies and address long-standing questions about possible biases in the cosmic star formation rate due to surface brightness dimming. Contrasting B-, V-, and i-dropout samples culled from the deeper data with those obtained from the shallower Great Observatories Origins Deep Survey fields, we demonstrate that the shallower data are essentially complete at bright magnitudes to z~0.4", >~3 kpc) low surface brightness galaxies are rare. A simple comparison of the half-light radii of the Hubble Deep Field-North + Hubble Deep Field-South U-dropouts with B-, V-, and i-dropouts from the UDF shows that the sizes follow a (1+z)-1.05+/-0.21 scaling toward high redshift. A more rigorous measurement compares different scalings of our U-dropout sample with the mean profiles for a set of intermediate-magnitude (26.0dropouts from the UDF. The best fit is found with a (1+z)-0.94+0.19-0.25 size scaling (for fixed luminosity). This result is then verified by repeating this experiment with different size measures, low-redshift samples, and magnitude ranges. Very similar scalings are found for all comparisons. A robust measurement of size evolution is thereby demonstrated for galaxies from z~6 to 2.5 using data from the UDF. Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Why did humans develop a large brain?

OpenAIRE

Muscat Baron, Yves

2012-01-01

"Of all animals, man has the largest brain in proportion to his size"- Aristotle. Dr Yves Muscat Baron shares his theory on how humans evolved large brains. The theory outlines how gravity could have helped humans develop a large brain- the author has named the theory 'The Gravitational Vascular Theory'. http://www.um.edu.mt/think/why-did-humans-develop-a-large-brain/

Cluster size matters: Size-driven performance of subnanometer clusters in catalysis, electrocatalysis and Li-air batteries

Science.gov (United States)

Vajda, Stefan

2015-03-01

This paper discusses the strongly size-dependent performance of subnanometer cluster based catalysts in 1) heterogeneous catalysis, 2) electrocatalysis and 3) Li-air batteries. The experimental studies are based on I. fabrication of ultrasmall clusters with atomic precision control of particle size and their deposition on oxide and carbon based supports; II. test of performance, III. in situand ex situ X-ray characterization of cluster size, shape and oxidation state; and IV.electron microscopies. Heterogeneous catalysis. The pronounced effect of cluster size and support on the performance of the catalyst (catalyst activity and the yield of Cn products) will be illustrated on the example of nickel and cobalt clusters in Fischer-Tropsch reaction. Electrocatalysis. The study of the oxygen evolution reaction (OER) on size-selected palladium clusters supported on ultrananocrystalline diamond show pronounced size effects. While Pd4 clusters show no reaction, Pd6 and Pd17 clusters are among the most active catalysts known (in in terms of turnover rate per Pd atom). The system (soft-landed Pd4, Pd6, or Pd17 clusters on an UNCD Si coated electrode) shows stable electrochemical potentials over several cycles, and the characterization of the electrodes show no evidence for evolution or dissolution of either the support Theoretical calculations suggest that this striking difference may be a demonstration that bridging Pd-Pd sites, which are only present in three-dimensional clusters, are active for the oxygen evolution reaction in Pd6O6. Li-air batteries. The studies show that sub-nm silver clusters have dramatic size-dependent effect on the lowering of the overpotential, charge capacity, morphology of the discharge products, as well as on the morphology of the nm size building blocks of the discharge products. The results suggest that by precise control of the active surface sites on the cathode, the performance of Li-air cells can be significantly improved

Skulls and Human Evolution: The Use of Casts of Anthropoid Skulls in Teaching Concepts of Human Evolution.

Science.gov (United States)

Gipps, John

1991-01-01

Proposes the use of a series of 11 casts of fossil skulls as a method of teaching about the theory of human evolution. Students explore the questions of which skulls are "human" and which came first in Homo Sapien development, large brain or upright stance. (MDH)

Variation, Evolution, and Correlation Analysis of C+G Content and Genome or Chromosome Size in Different Kingdoms and Phyla

Science.gov (United States)

Li, Xiu-Qing; Du, Donglei

2014-01-01

C+G content (GC content or G+C content) is known to be correlated with genome/chromosome size in bacteria but the relationship for other kingdoms remains unclear. This study analyzed genome size, chromosome size, and base composition in most of the available sequenced genomes in various kingdoms. Genome size tends to increase during evolution in plants and animals, and the same is likely true for bacteria. The genomic C+G contents were found to vary greatly in microorganisms but were quite similar within each animal or plant subkingdom. In animals and plants, the C+G contents are ranked as follows: monocot plants>mammals>non-mammalian animals>dicot plants. The variation in C+G content between chromosomes within species is greater in animals than in plants. The correlation between average chromosome C+G content and chromosome length was found to be positive in Proteobacteria, Actinobacteria (but not in other analyzed bacterial phyla), Ascomycota fungi, and likely also in some plants; negative in some animals, insignificant in two protist phyla, and likely very weak in Archaea. Clearly, correlations between C+G content and chromosome size can be positive, negative, or not significant depending on the kingdoms/groups or species. Different phyla or species exhibit different patterns of correlation between chromosome-size and C+G content. Most chromosomes within a species have a similar pattern of variation in C+G content but outliers are common. The data presented in this study suggest that the C+G content is under genetic control by both trans- and cis- factors and that the correlation between C+G content and chromosome length can be positive, negative, or not significant in different phyla. PMID:24551092

Ultrasound effects on brain-targeting mannosylated liposomes: in vitro and blood–brain barrier transport investigations

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Zidan AS

2015-07-01

Full Text Available Ahmed S Zidan,1,2 Hibah Aldawsari1 1Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia; 2Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Zagazig University, Zagazig, Egypt Abstract: Delivering drugs to intracerebral regions can be accomplished by improving the capacity of transport through blood–brain barrier. Using sertraline as model drug for brain targeting, the current study aimed at modifying its liposomal vesicles with mannopyranoside. Box-Behnken design was employed to statistically optimize the ultrasound parameters, namely ultrasound amplitude, time, and temperature, for maximum mannosylation capacity, sertraline entrapment, and surface charge while minimizing vesicular size. Moreover, in vitro blood–brain barrier transport model was established to assess the transendothelial capacity of the optimized mannosylated vesicles. Results showed a dependence of vesicular size, mannosylation capacity, and sertraline entrapment on cavitation and bubble implosion events that were related to ultrasound power amplitude, temperature. However, short ultrasound duration was required to achieve >90% mannosylation with nanosized vesicles (<200 nm of narrow size distribution. Optimized ultrasound parameters of 65°C, 27%, and 59 seconds for ultrasound temperature, amplitude, and time were elucidated to produce 81.1%, 46.6 nm, and 77.6% sertraline entrapment, vesicular size, and mannosylation capacity, respectively. Moreover, the transendothelial ability was significantly increased by 2.5-fold by mannosylation through binding with glucose transporters. Hence, mannosylated liposomes processed by ultrasound could be a promising approach for manufacturing and scale-up of brain-targeting liposomes. Keywords: CNS delivery, sizing, lipid based formulations, quality by design, sertraline hydrochloride

Ultrasound effects on brain-targeting mannosylated liposomes: in vitro and blood-brain barrier transport investigations.

Science.gov (United States)

Zidan, Ahmed S; Aldawsari, Hibah

2015-01-01

Delivering drugs to intracerebral regions can be accomplished by improving the capacity of transport through blood-brain barrier. Using sertraline as model drug for brain targeting, the current study aimed at modifying its liposomal vesicles with mannopyranoside. Box-Behnken design was employed to statistically optimize the ultrasound parameters, namely ultrasound amplitude, time, and temperature, for maximum mannosylation capacity, sertraline entrapment, and surface charge while minimizing vesicular size. Moreover, in vitro blood-brain barrier transport model was established to assess the transendothelial capacity of the optimized mannosylated vesicles. Results showed a dependence of vesicular size, mannosylation capacity, and sertraline entrapment on cavitation and bubble implosion events that were related to ultrasound power amplitude, temperature. However, short ultrasound duration was required to achieve >90% mannosylation with nanosized vesicles (ultrasound parameters of 65°C, 27%, and 59 seconds for ultrasound temperature, amplitude, and time were elucidated to produce 81.1%, 46.6 nm, and 77.6% sertraline entrapment, vesicular size, and mannosylation capacity, respectively. Moreover, the transendothelial ability was significantly increased by 2.5-fold by mannosylation through binding with glucose transporters. Hence, mannosylated liposomes processed by ultrasound could be a promising approach for manufacturing and scale-up of brain-targeting liposomes.

An investigation of processes controlling the evolution of the boundary layer aerosol size distribution properties at the Swedish background station Aspvreten

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P. Tunved

2004-01-01

Full Text Available Aerosol size distributions have been measured at the Swedish background station Aspvreten (58.8° N, 17.4° E. Different states of the aerosol were determined using a novel application of cluster analysis. The analysis resulted in eight different clusters capturing different stages of the aerosol lifecycle. The atmospheric aerosol size distributions were interpreted as belonging to fresh, intermediate and aged types of size distribution. With aid of back trajectory analysis we present statistics concerning the relation of source area and different meteorological parameters using a non-Lagrangian approach. Source area is argued to be important although not sufficient to describe the observed aerosol properties. Especially processing by clouds and precipitation is shown to be crucial for the evolution of the aerosol size distribution. As much as 60% of the observed size distributions present features that are likely to be related to cloud processes or wet deposition. The lifetime properties of different sized aerosols are discussed by means of measured variability of the aerosol size distribution. Processing by clouds and precipitation is shown to be especially crucial in the size range 100 nm and larger. This indicates an approximate limit for activation in clouds to 100 nm in this type of environment. The aerosol lifecycle is discussed. Size distributions indicating signs of recent new particle formation (~30% of the observed size distributions represent the first stage in the lifecycle. Aging of the aerosol size distribution may follow two branches: either growth by condensation and coagulation or processing by non-precipitating clouds. In both cases mass is accumulated. Wet removal is the main process capable of removing aerosol mass. Wet deposition is argued to be an important mechanism in reaching a state where nucleation may occur (i.e. sufficiently low aerosol surface area in environments similar to the one studied.

The Importance of Dietary Carbohydrate in Human Evolution

OpenAIRE

Hardy, K.; Brand-Miller, J.; Brown, K. D.; Thomas, M. G.; Copeland, L.

2015-01-01

We propose that plant foods containing high quantities of starch were essential for the evolution of the human phenotype during the Pleistocene. Although previous studies have highlighted a stone tool-mediated shift from primarily plant-based to primarily meat-based diets as critical in the development of the brain and other human traits, we argue that digestible carbohydrates were also necessary to accommodate the increased metabolic demands of a growing brain. Furthermore, we acknowledge th...

The evolution of cuckoo parasitism: a comparative analysis.

Science.gov (United States)

Krüger, O; Davies, N B

2002-02-22

Cuckoos (family Cuculidae) show the highest diversity of breeding strategies within one bird family (parental care, facultative and obligate brood parasites). We used independent contrasts from two phylogenies to examine how this variation was related to 13 ecological and life-history variables. The ancestral state was probably tropical, resident, forest cuckoos with parental care. The evolution of brood parasitism was correlated with a shift to more open habitats, a change in diet, increases in species breeding-range size and migration, and a decrease in egg size. Once parasitism had evolved, more elaborate parasitic strategies (more harmful to host fitness) were correlated with decreased egg size, a change in diet, increased breeding-range size and migration, a shortened breeding season and a decrease in local abundance. Establishing the most probable evolutionary pathways, using the method of Pagel, shows that changes in ecological variables (such as migration, range size and diet type) preceded the evolution of brood parasitism, which is likely to be a later adaptation to reduce the cost of reproduction. By contrast, brood parasitism evolved before changes in egg size occurred, indicating that egg size is an adaptive trait in host--parasite coevolution. Our results suggest that the evolution of cuckoo brood parasitism reflects selection from both ecological pressures and host defences.

Orbital evolution of colliding star and pulsar winds in 2D and 3D: effects of dimensionality, EoS, resolution, and grid size

Science.gov (United States)

Bosch-Ramon, V.; Barkov, M. V.; Perucho, M.

2015-05-01

Context. The structure formed by the shocked winds of a massive star and a non-accreting pulsar in a binary system suffers periodic and random variations of orbital and non-linear dynamical origins. The characterization of the evolution of the wind interaction region is necessary for understanding the rich phenomenology of these sources. Aims: For the first time, we simulate in 3 dimensions the interaction of isotropic stellar and relativistic pulsar winds along one full orbit, on scales well beyond the binary size. We also investigate the impact of grid resolution and size, and of different state equations: a γ̂-constant ideal gas, and an ideal gas with γ̂ dependent on temperature. Methods: We used the code PLUTO to carry out relativistic hydrodynamical simulations in 2 and 3 dimensions of the interaction between a slow dense wind and a mildly relativistic wind with Lorentz factor 2, along one full orbit in a region up to ~100 times the binary size. The different 2-dimensional simulations were carried out with equal and larger grid resolution and size, and one was done with a more realistic equation of state than in 3 dimensions. Results: The simulations in 3 dimensions confirm previous results in 2 dimensions, showing: a strong shock induced by Coriolis forces that terminates the pulsar wind also in the opposite direction to the star; strong bending of the shocked-wind structure against the pulsar motion; and the generation of turbulence. The shocked flows are also subject to a faster development of instabilities in 3 dimensions, which enhances shocks, two-wind mixing, and large-scale disruption of the shocked structure. In 2 dimensions, higher resolution simulations confirm lower resolution results, simulations with larger grid sizes strengthen the case for the loss of the general coherence of the shocked structure, and simulations with two different equations of state yield very similar results. In addition to the Kelvin-Helmholtz instability, discussed in

Pharmacologic resuscitation for hemorrhagic shock combined with traumatic brain injury

DEFF Research Database (Denmark)

Jin, Guang; Duggan, Michael; Imam, Ayesha

2012-01-01

[Hex]) after traumatic brain injury (TBI) decreases brain swelling, without affecting size of the lesion. This study was performed to determine whether addition of VPA to Hex would decrease the lesion size in a clinically relevant large animal model of TBI + HS....

Using perturbations to identify the brain circuits underlying active vision.

Science.gov (United States)

Wurtz, Robert H

2015-09-19

The visual and oculomotor systems in the brain have been studied extensively in the primate. Together, they can be regarded as a single brain system that underlies active vision--the normal vision that begins with visual processing in the retina and extends through the brain to the generation of eye movement by the brainstem. The system is probably one of the most thoroughly studied brain systems in the primate, and it offers an ideal opportunity to evaluate the advantages and disadvantages of the series of perturbation techniques that have been used to study it. The perturbations have been critical in moving from correlations between neuronal activity and behaviour closer to a causal relation between neuronal activity and behaviour. The same perturbation techniques have also been used to tease out neuronal circuits that are related to active vision that in turn are driving behaviour. The evolution of perturbation techniques includes ablation of both cortical and subcortical targets, punctate chemical lesions, reversible inactivations, electrical stimulation, and finally the expanding optogenetic techniques. The evolution of perturbation techniques has supported progressively stronger conclusions about what neuronal circuits in the brain underlie active vision and how the circuits themselves might be organized.

In search of genetic constraints limiting the evolution of egg size: direct and correlated responses to artificial selection on a prenatal maternal effector.

Science.gov (United States)

Pick, J L; Hutter, P; Tschirren, B

2016-06-01

Maternal effects are an important force in nature, but the evolutionary dynamics of the traits that cause them are not well understood. Egg size is known to be a key mediator of prenatal maternal effects with an established genetic basis. In contrast to theoretical expectations for fitness-related traits, there is a large amount of additive genetic variation in egg size observed in natural populations. One possible mechanism for the maintenance of this variation is through genetic constraints caused by a shared genetic basis among traits. Here we created replicated, divergent selection lines for maternal egg investment in Japanese quail (Coturnix japonica) to quantify the role of genetic constraints in the evolution of egg size. We found that egg size responds rapidly to selection, accompanied by a strong response in all egg components. Initially, we observed a correlated response in body size, but this response declined over time, showing that egg size and body size can evolve independently. Furthermore, no correlated response in fecundity (measured as the proportion of days on which a female laid an egg) was observed. However, the response to selection was asymmetrical, with egg size plateauing after one generation of selection in the high but not the low investment lines. We attribute this pattern to the presence of genetic asymmetries, caused by directional dominance or unequal allele frequencies. Such asymmetries may contribute to the evolutionary stasis in egg size observed in natural populations, despite a positive association between egg size and fitness.

Has evolution 'prepared' us to deal with death ...

African Journals Online (AJOL)

Has evolution 'prepared' us to deal with death? ... brain with its enlarged Broca's area suggests the possibility of a sophisticated communication system and an enhanced way of dealing with emotion. ... Some attention is given to this thesis.

THE ROLE OF QUENCHING TIME IN THE EVOLUTION OF THE MASS–SIZE RELATION OF PASSIVE GALAXIES FROM THE WISP SURVEY

Energy Technology Data Exchange (ETDEWEB)

Zanella, A.; Scarlata, C.; Rutkowski, M. J. [Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis MN 55455 (United States); Corsini, E. M.; Bontà, E. Dalla [Dipartimento di Fisica e Astronomia “G. Galilei,” Università di Padova, vicolo dell’Osservatorio 3, I-35122 Padova (Italy); Bedregal, A. G. [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Atek, H. [Spitzer Science Center, Caltech, Pasadena, CA 91125 (United States); Bunker, A. J. [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford, OX13RH (United Kingdom); Colbert, J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Dai, Y. S. [Infrared Processing and Analysis Center, 770 South Wilson Avenue, Pasadena, CA 91125 (United States); Henry, A.; Rafelski, M. [Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States); Malkan, M. [Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA 90095 (United States); Martin, C. [Department of Physics, University of California, Santa Barbara, CA, 93106 (United States); Siana, B. [Department of Physics and Astronomy, University of California Riverside, Riverside, CA 92521 (United States); Teplitz, H., E-mail: anita.zanella@cea.fr, E-mail: cmartin@physics.ucsb.edu [Infrared Processing and Analysis Center, Caltech, Pasadena, CA 91125 (United States)

2016-06-20

We analyze how passive galaxies at z ∼ 1.5 populate the mass–size plane as a function of their stellar age, to understand if the observed size growth with time can be explained with the appearance of larger quenched galaxies at lower redshift. We use a sample of 32 passive galaxies extracted from the Wide Field Camera 3 Infrared Spectroscopic Parallel (WISP) survey with spectroscopic redshift 1.3 ≲ z ≲ 2.05, specific star formation rates lower than 0.01 Gyr{sup −1}, and stellar masses above 4.5 × 10{sup 10} M {sub ⊙}. All galaxies have spectrally determined stellar ages from fitting of their rest-frame optical spectra and photometry with stellar population models. When dividing our sample into young (age ≤2.1 Gyr) and old (age >2.1 Gyr) galaxies we do not find a significant trend in the distributions of the difference between the observed radius and that predicted by the mass–size relation. This result indicates that the relation between the galaxy age and its distance from the mass–size relation, if it exists, is rather shallow, with a slope α ≳ −0.6. At face value, this finding suggests that multiple dry and/or wet minor mergers, rather than the appearance of newly quenched galaxies, are mainly responsible for the observed time evolution of the mass–size relation in passive galaxies.

Performance Analysis of Unsupervised Clustering Methods for Brain Tumor Segmentation

Directory of Open Access Journals (Sweden)

Tushar H Jaware

2013-10-01

Full Text Available Medical image processing is the most challenging and emerging field of neuroscience. The ultimate goal of medical image analysis in brain MRI is to extract important clinical features that would improve methods of diagnosis & treatment of disease. This paper focuses on methods to detect & extract brain tumour from brain MR images. MATLAB is used to design, software tool for locating brain tumor, based on unsupervised clustering methods. K-Means clustering algorithm is implemented & tested on data base of 30 images. Performance evolution of unsupervised clusteringmethods is presented.

Brain Plasticity and Intellectual Ability Are Influenced by Shared Genes

NARCIS (Netherlands)

Brans, R.G.H.; Kahn, R.S.; Schnack, H.G.; van Baal, G.C.M.; Posthuma, D.; van Haren, N.E.M.; Lepage, C.; Lerch, J.P.; Collins, D.L.; Evans, A.C.; Boomsma, D.I.; Hulshoff Pol, H.E.

2010-01-01

Although the adult brain is considered to be fully developed and stable until senescence when its size steadily decreases, such stability seems at odds with continued human (intellectual) development throughout life. Moreover, although variation in human brain size is highly heritable, we do not

Evolution of A-Type Macrosegregation in Large Size Steel Ingot After Multistep Forging and Heat Treatment

Science.gov (United States)