Global and regional brain metabolic scaling and its functional consequences

Background: Information processing in the brain requires large amounts of metabolic energy, the spatial distribution of which is highly heterogeneous reflecting complex activity patterns in the mammalian brain. Results: Here, it is found based on empirical data that, despite this heterogeneity, the volume-specific cerebral glucose metabolic rate of many different brain structures scales with brain volume with almost the same exponent around -0.15. The exception is white matter, the metabolism of which seems to scale with a standard specific exponent -1/4. The scaling exponents for the total oxygen and glucose consumptions in the brain in relation to its volume are identical and equal to $0.86\pm 0.03$, which is significantly larger than the exponents 3/4 and 2/3 suggested for whole body basal metabolism on body mass. Conclusions: These findings show explicitly that in mammals (i) volume-specific scaling exponents of the cerebral energy expenditure in different brain parts are approximately constant (except brain stem structures), and (ii) the total cerebral metabolic exponent against brain volume is greater than the much-cited Kleiber's 3/4 exponent. The neurophysiological factors that might account for the regional uniformity of the exponents and for the excessive scaling of the total brain metabolism are discussed, along with the relationship between brain metabolic scaling and computation.Comment: Brain metabolism scales with its mass well above 3/4 exponen

Comparative Analysis of the Subventricular Zone in Rat, Ferret and Macaque: Evidence for an Outer Subventricular Zone in Rodents

The mammalian cerebral cortex arises from precursor cells that reside in a proliferative region surrounding the lateral ventricles of the developing brain. Recent work has shown that precursor cells in the subventricular zone (SVZ) provide a major contribution to prenatal cortical neurogenesis, and that the SVZ is significantly thicker in gyrencephalic mammals such as primates than it is in lissencephalic mammals including rodents. Identifying characteristics that are shared by or that distinguish cortical precursor cells across mammalian species will shed light on factors that regulate cortical neurogenesis and may point toward mechanisms that underlie the evolutionary expansion of the neocortex in gyrencephalic mammals. We immunostained sections of the developing cerebral cortex from lissencephalic rats, and from gyrencephalic ferrets and macaques to compare the distribution of precursor cell types in each species. We also performed time-lapse imaging of precursor cells in the developing rat neocortex. We show that the distribution of Pax6+ and Tbr2+ precursor cells is similar in lissencephalic rat and gyrencephalic ferret, and different in the gyrencephalic cortex of macaque. We show that mitotic Pax6+ translocating radial glial cells (tRG) are present in the cerebral cortex of each species during and after neurogenesis, demonstrating that the function of Pax6+ tRG cells is not restricted to neurogenesis. Furthermore, we show that Olig2 expression distinguishes two distinct subtypes of Pax6+ tRG cells. Finally we present a novel method for discriminating the inner and outer SVZ across mammalian species and show that the key cytoarchitectural features and cell types that define the outer SVZ in developing primates are present in the developing rat neocortex. Our data demonstrate that the developing rat cerebral cortex possesses an outer subventricular zone during late stages of cortical neurogenesis and that the developing rodent cortex shares important features with that of primates

High associative neuron numbers could drive cognitive performance in corvid species

Corvids possess cognitive skills, matching those of nonhuman primates. However, how these species with their small brains achieve such feats remains elusive. Recent studies suggest that cognitive capabilities could be based on the total numbers of telencephalic neurons. Here we extend this hypothesis further and posit that especially high neuron counts in associative pallial areas drive flexible, complex cognition. If true, avian species like corvids should specifically accumulate neurons in the avian associative areas meso- and nidopallium. To test the hypothesis, we analyzed the neuronal composition of telencephalic areas in corvids and noncorvids (chicken, pigeons, and ostriches—the species with the largest bird brain). The overall number of pallial neurons in corvids was much higher than in chicken and pigeons and comparable to those of ostriches. However, neuron numbers in the associative mesopallium and nidopallium were twice as high in corvids and, in correlation with these associative areas, the corvid subpallium also contained high neuron numbers. These findings support our hypothesis that large absolute numbers of associative pallial neurons contribute to cognitive flexibility and complexity and are key to explain why crows are smart. Since meso-/nidopallial and subpallial areas scale jointly, it is conceivable that associative pallio-striatal loops play a similar role in executive decision making as described in primates

Problemas ambientais, saúde coletiva e ciências sociais Environmental problems, collective health and social sciences

Problemas ambientais e sua interface com a saúde estão sempre presentes nos discursos e práticas sanitárias. Em meados do século 19, com os intensos impactos do processo de industrialização e urbanização sobre as condições sanitárias e de saúde, esses problemas são vistos como resultados de processos políticos e sociais. Mas com o paradigma microbiano essa relação foi reduzida aos problemas de saneamento e a controle de vetores. A dimensão social e política passa a ocupar lugar marginal e periférico. Para os movimentos ambientalistas e a medicina social latino-americana a noção de problemas ambientais e de problemas de saúde é ampliada. Apesar dos avanços, a análise de dados sobre grupos de pesquisa, a produção de teses e dissertações e a publicação de artigos científicos revelam que o campo da saúde coletiva ocupa um papel marginal na pesquisa sobre o tema problemas ambientais e a pesquisa e a produção das ciências sociais respondem por uma parcela muito pequena. O quadro atual impõe a necessidade de se avançar quantitativa e qualitativamente na pesquisa e produção científica da saúde coletiva sendo urgente no que se refere às ciências sociais e, particularmente, nas ciências sociais em saúde.<br>Environmental problems relative to health conditions have been always present in the speeches and practises about health. During 19 century, however, the wide and intense impacts of industrialization and urbanization over sanitary conditions contribute to a comprehension of these problems as result of social and political processes. With the advent of microbiological paradigm the strategies for these problems solutions were reduced to sanitation and vector control and the social and political dimensions become marginal and peripheric. The notion of environmental and health problems was enlarged and the social and political dimensions were retaking only during the 70s with the emergence of environmental movement and of social medicine in Latin-America. In spite of these advances, data analyses about researches groups, thesis and dissertations production and articles published in scientific journals reveal the collective health have a marginal role in the research about environmental problems and the research and scientific production of social science is too few. The present situation requires quantitative and qualitative advances in collective health research and scientific production, especially in the field of social science and health

O Movimento Cidades/Municípios Saudáveis: um compromisso com a qualidade de vida The Healthy Cities Movement: a commitement with quality of life

O Movimento Cidades/Municípios Saudáveis, desde a década de 1970, vem envolvendo cada vez maior número de cidades e atores em vários países e divulgando uma prática que representa uma nova forma de pensar e fazer saúde. O movimento tem como objetivo um produto social, a qualidade de vida da população e pressupõe a existência de problemas concretos de pessoas vivendo em um território. Representa uma nova forma de gestão municipal, baseada na ação intersetorial e exige, ao mesmo tempo, um protagonismo do Estado e a participação da sociedade civil como parceira na consecução dos objetivos. No Brasil há, até o momento, 19 municípios envolvidos com a proposta, mas somente 13 estão com projetos ativos. Os resultados dos esforços estão começando a ser visualizados, trazendo novas perspectivas em termos de desenvolvimento social e sustentado, bem como de melhoria das condições de saúde e qualidade de vida.<br>The Healthy Cities Movement has been involving an increasing number of cities and actors in several countries of the world since the 70's, and has been divulging a practice that represents a new form of thinking and working on health which aims at constructing a social product - quality of life of the population. This new proposal presupposes the existence of people living in a territory with concrete problem. It represents a new form of city administration based on intersectorial action and demands the protagonism of the state, as well as the participation of civil society in the accomplishment of new objectives aiming at changing the city profile. In Brazil there are so far 19 municipal districts involved with Healthy Cities' proposal but only 13 with active projects. The results of the efforts of these municipal districts are beginning to become visible and to bring new perspectives in terms of social and sustained development and the improvement of health conditions and quality of life