Abstract
Advances in neuroimaging and neuroanatomy have yielded major insights concerning fundamental principles of cortical organization and evolution, thus speaking to how well different species serve as models for human brain function in health and disease. Here, we focus on cortical folding, parcellation, and connectivity in mice, marmosets, macaques, and humans. Cortical folding patterns vary dramatically across species, and individual variability in cortical folding increases with cortical surface area. Such issues are best analyzed using surface-based approaches that respect the topology of the cortical sheet. Many aspects of cortical organization can be revealed using 1 type of information (modality) at a time, such as maps of cortical myelin content. However, accurate delineation of the entire mosaic of cortical areas requires a multimodal approach using information about function, architecture, connectivity, and topographic organization. Comparisons across the 4 aforementioned species reveal dramatic differences in the total number and arrangement of cortical areas, particularly between rodents and primates. Hemispheric variability and bilateral asymmetry are most pronounced in humans, which we evaluated using a high-quality multimodal parcellation of hundreds of individuals. Asymmetries include modest differences in areal size but not in areal identity. Analyses of cortical connectivity using anatomical tracers reveal highly distributed connectivity and a wide range of connection weights in monkeys and mice; indirect measures using functional MRI suggest a similar pattern in humans. Altogether, a multifaceted but integrated approach to exploring cortical organization in primate and nonprimate species provides complementary advantages and perspectives.
Highlights
Advances in neuroimaging and neuroanatomy have yielded major insights concerning fundamental principles of cortical organization and evolution, speaking to how well different species serve as models for human brain function in health and disease
The human brain is ∼3,800 times larger than that of the mouse, which diverged from our lineage ∼75 MYA; it is ∼290 times larger than that of the New World marmoset monkey, Cerebral cortex is the dominant structure of the mammalian brain and is implicated in a wide range of sensory, motor, cognitive, and emotional functions
Using structural MRI scans to examine cortical folding patterns in 3 gyrencephalic primates, we found that the variability of folding across individuals scales with brain size and complexity of convolutions
Summary
Parcellation, and connectivity in humans, nonhuman primates, and mice. | | | | macaque marmoset neuroanatomy cerebral cortex neuroimaging recent years these have been dwarfed by noninvasive methods, MRI. These complementary invasive and noninvasive methods have contributed to an explosion of experimental findings pertaining to cortical structure, function, and connectivity in a number of intensively studied species. We take an evolutionary perspective that focuses on a few intensively studied species—humans, nonhuman primates, and mice—and a few general topics pertaining to cerebral cortex These include 1) macroscopic morphology and individual variability, as revealed by MRI; 2) cortical parcellation, functional organization, and bilateral symmetry; and 3) corticocortical connectivity. Animal models offer promise for much-needed validation studies of the noninvasive approaches that are being used in the human brain
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