Abstract
A central question in comparative neurobiology concerns how evolution has produced brains with expanded neocortices, composed of more areas with unique connectivity and functional properties. Some mammalian lineages, such as primates, exhibit exceptionally large cortices relative to the amount of sensory inputs from the dorsal thalamus, and this expansion is associated with a larger number of distinct cortical areas, composing a larger proportion of the cortical sheet. We propose a link between the organization of the neocortex and its expansion relative to the size of the dorsal thalamus, based on a combination of work in comparative neuroanatomy and experimental research.