Generation of the Cortical Area Map Emx2 Strikes Back

The recent identification of molecular cues involved in the generation of the cortical area map, such as the patterning molecule FGF8 and transcription factors such as Emx2, represents an important breakthrough. In this issue of Neuron, Hamasaki et al. use a genetic approach to explore how these signals interact and propose that Emx2 plays a direct, largely FGF8-independent role in the control of the relative size and position that each area occupies within the cortex.