All of the mammalian species but none of the non-mammalian species have the layered neocortex in the dorsal telencephalon. We are exploring the evolutionary scenario for the layered neocortex through comparing developmental processes of brains of different vertebrate species.
In the mammalian neocortex, deep layer (DL) and upper layer (UL) neurons are horizontally aligned. In the chick and turtle brains, deep and upper layer neurons are separated in the medial and lateral domains, respectively.
see NIG research news for details
Suzuki, I.K., Kawasaki, T., Gojobori, T. and Hirata, T. (2012) The temporal sequence of the mammalian neocortical neurogenetic program drives mediolateral pattern in the chick pallium. Dev. Cell 22 863-870. doi:10.1016/j.devcel.2012.01.004
Suzuki. I.K. and Hirata, T. (2014) A common developmental plan for neocortical gene-expressing neurons in the pallium of the domestic chicken Gallus gallus domesticus and the Chinese softshell turtle Pelodiscus sinensis. Front. Neuroanat. April 8 1-17. doi: 10.3389/fnana.2014.00020
Suzuki, I.K. and Hirata, T. (2013) Neocortical neurogenesis is not really “neo”: a new evolutionary model derived from a comparative study of chick pallial development. review, Dev. Growth Differ. 55, 173-187. doi: 10.1111/dgd.12020.