A universal scaling law between gray matter and white matter of cerebral cortex

Neocortex, a new and rapidly evolving brain structure in mammals, has a similar layered architecture in species over a wide range of brain sizes. Larger brains require longer fibers to communicate between distant cortical areas; the volume of the white matter that contains long axons increases disproportionally faster than the volume of the gray matter that contains cell bodies, dendrites, and axons for local information processing, according to a power law. The theoretical analysis presented here shows how this remarkable anatomical regularity might arise naturally as a consequence of the local uniformity of the cortex and the requirement for compact arrangement of long axonal fibers. The predicted power law with an exponent of 4/3 minus a small correction for the thickness of the cortex accurately accounts for empirical data spanning several orders of magnitude in brain sizes for various mammalian species, including human and nonhuman primates.

A Declaração universal dos direitos do homem e a constituição portuguesa

Análise comparativa dos direitos humanos na constituição dos seguintes paises : Espanha, Portugal, São Tomé e Príncipe e Angola

A Universidade de bolonha e a cultura universal os herdeiros espirituais de bolonha no ocidente : andres bell / Silvio A. B. Meira. --

Trabalho apresentado na Universidade Nacional do Chile, Santiago, em comemoração aos 900 anos da Universidade de Bolonha.

Princípios jurídicos e esperança de uma futura autoridade pública universal

Inclui notas explicativas, bibliográficas e bibliografia

Interpreting the universal phylogenetic tree

The universal phylogenetic tree not only spans all extant life, but its root and earliest branchings represent stages in the evolutionary process before modern cell types had come into being. The evolution of the cell is an interplay between vertically derived and horizontally acquired variation. Primitive cellular entities were necessarily simpler and more modular in design than are modern cells. Consequently, horizontal gene transfer early on was pervasive, dominating the evolutionary dynamic. The root of the universal phylogenetic tree represents the first stage in cellular evolution when the evolving cell became sufficiently integrated and stable to the erosive effects of horizontal gene transfer that true organismal lineages could exist.