Magnetic resonance imaging and diffusion tensor imaging reconstruction of connectomes in a macropod, the quokka (Setonix brachyurus).

The diversity of the diprotodontids provides an excellent opportunity to study how a basic marsupial cortical plan has been modified for the needs of the mammals living in different habitats. Very little is known about the connections of the cerebral cortex with the deep brain structures (basal ganglia and thalamus) in this evolutionarily significant group of mammals. In this study, we performed mapping of brain regions and connections in a diprotodontid marsupial from data obtained from an excised brain scanned in high-field (9.

Numerical Analysis of the Cerebral Cortex in Diprotodontids (Marsupialia; Australidelphia) and Comparison with Eutherian Brains.

Diprotodontids are a diverse group of Australian metatherians, which occupy a range of ecological niches from nectar and pollen-feeders to grazers and folivores. The group encompasses small-brained nectar-feeding species (Tarsipes) and large-brained grazing and browsing species (macropods). This group of Australian metatherians therefore represents an opportunity to examine how the cerebral cortex has expanded in an adaptive radiation quite independent of that occurring among eutherians.

Quantitative analysis of cerebellar morphology in monotreme, metatherian and eutherian mammals.

To superficial inspection, the mammalian cerebellum appears to be a stereotypical structure that varies little in morphology across mammals. In the present study, the volumes of components of the corpus cerebelli, foliation of the cerebellar cortex and the volumes of the pontine and deep cerebellar nuclei have been measured and compared in three species of monotreme, 90 species of marsupial and 57 species of eutherian mammal. In all three mammalian groups, the volume of the corpus cerebelli scales isometrically with brain volume, and pontine nuclear volume also scales isometrically with cerebellar volume.

Quantitative analysis of arterial supply to the developing brain in tetrapod vertebrates.

Understanding the metabolic cost of building developing tetrapod brains is critically important to explaining the more than 10-fold differences in encephalization of adult tetrapods that have emerged during evolution. The exact metabolic costs of developing the variety of tetrapod brains are impossible to determine, but one can compare cerebral artery caliber (internal radius raised to the fourth power-r ) across developing tetrapod vertebrate groups as a proxy of cerebral arterial flow, the delivery of nutrients during embryogenesis and early postnatal development, and hence the metabolic costs of brain development. In this study, r of aortic outflow and cerebral inflow arteries, as well as aortic wall thickness as a proxy of arterial pressure, were measured and compared between developing representatives of all four tetrapod classes (mammals, birds, reptiles, and amphibians).

Quantitative Analysis of the Timing of Development of the Cerebellum and Precerebellar Nuclei in Monotremes, Metatherians, Rodents, and Humans.

We have used a quantitative statistical approach to compare the pace of development in the cerebellum and precerebellar systems relative to body size in monotremes and metatherians with that in eutherians (rodents and humans). Embryos, fetuses, and early postnatal mammals were scored on whether key structural events had been reached in the development of the cerebellum itself (CC-corpus cerebelli; 10 milestones), or the pontine and inferior olivary precerebellar nuclear groups (PC; 4 milestones). We found that many early cerebellar and precerebellar milestones (e.