What comparative studies of neocortex tell us about the human brain

There are several ways in which comparative studies of brain organization and function can be informative in attempts to understand the human brain. Often investigators study a favorable and sometimes specialized species in order to reveal features that may reflect general or widespread principles. The example used here is that the cortical representation of the unique and highly specialized receptor sheet of the nose of the star-nosed mole provides further evidence that the receptor sheet instructs the development of cortex. Comparative studies are also used to reconstruct the evolution of brain systems. As an example, comparative studies suggest that the visual area MT in the upper temporal lobe of primates evolved from a visual area along the border of V2. A third and very important use of comparative studies is to provide another level of evaluation of theories developed from a particular species. Since the brains of different mammals are modifications of an ancestral plan, conclusions about brain organization in any given species should be consistent with those for other species, within the framework of evolutionary change. When current proposals for how visual cortex is organized in rats and humans are considered from a comparative point of view, key concepts are clearly challenged.