For a long time, it has been assumed that mammals have different (better!) brains than other animals — partly because of the highly convoluted neocortex. Specifically, the mammalian neocortex features layers of cells (lamination) connected by radially arrayed columns of other cells, forming functional modules characterized by neuronal types and specific connections. Early studies of homologous regions in nonmammalian brains found no similar arrangement. Now new technology has revealed that a part of the chicken brain that handles auditory information is also composed of laminated layers of cells linked by narrow, radial columns of different types of cells with extensive interconnections that form microcircuits that are virtually identical to those found in the mammalian cortex. The finding suggests that the distinct structure of the mammalian neocortex has evolved from circuitry dating back at least 300 million years. The findings also indicate that mammalian and bird brains are more alike than we thought.
(2010). Laminar and columnar auditory cortex in avian brain.
Proceedings of the National Academy of Sciences. 107(28), 12676 - 12681.