Comparative neuroanatomy searches for the rules behind such organized diversity, as seen above. All of these brains have a cerebral cortex, a cerebellum in the back, olfactory bulbs up front, and a brainstem that is connected to the spinal cord. The marmoset brain stands out a little, at least in my opinion. It is the most smooth, with almost no visible gyri (folds) or sulci (grooves) on the surface. This makes the marmoset brain popular for studies of the visual system - the vast majority of the visual cortex lies exposed. Comparative neuroanatomy is used by paleoneurologists to understand the evolution of primate and human brains, to assess the nature of our cognitive abilities. Herculano-Houzel notes that it's less about gross anatomy, and more to do with architecture and neuronal connections. She found that the horizontal spacing distance between neurons have increased in humans in the frontopolar cortex as well as what we call Broca's area, whic...