Evolution of the Neocortex
The neocortex is the largest structure in the mammalian brain and yet it has no obvious homolog in the brain tissues of other vertebrates. In trying to understand the evolutionary origins of the neocortex the Ragsdale lab has found molecular support for one classic hypothesis: the input and output cell types of the neocortex are conserved in the dorsal telencephalon of birds and other reptiles.Dozens of nuclei can be distinguished in the brains of birds and mammals, and connections among neurons in these brains are in essence connections targeted to different nuclei. Viewed from this perspective, the problem of how neurons make the correct connections with one another in early development is, for studies of vertebrates, a problem of pattern formation. The Ragsdale Lab studies brain nucleogenesis in the chick and alligator embryos using cellular, molecular and genetic techniques. We are particularly interested in the signals that govern cell-type specification, the molecules that regulate how young neurons migrate to their future nuclear locations, and the mechanisms by which internuclear circuitry is established.