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Brain scaling: Cerebral cortex


Neocortex is a new and rapidly expanding brain structure unique to mammals. The section diagrams, adapted from a drawing by E. de Vries, show that the cerebral cortex of a larger brain tends to have disproportionally more long-distance connection fibers or white matter (dark regions) than the gray matter (folded outer surface).

The volumes of cortical gray matter and the adjacent white matter are closely related by a power law across nearly the full range of mammalian brain sizes. The data here were compiled from several sources, including my own measurements. The theory presented in my paper (available online) shows quantitatively how this remarkable anatomical relationship might follow as a necessary consequence of the basic uniformity of the neocortex and the compact wiring of its interconnection.
Kechen Zhang, 2000