Genetic Resolutions of Brain Convolutions

Cortical convolutions—prominent folds on the surface of the human brain—have a long history of speculation ( 1 ). The claims range from their function as a bodily cooling system to the attribution of Einstein's genius to the unusual shape of a single gyrus (the ridge of a cortical fold). Only recently, with advances in molecular genetics and brain imaging techniques, has it become possible to study the development, evolution, and abnormalities of cerebral convolutions in a scientifically rigorous manner ( 2 ). On page 764 of this issue, Bae et al. ( 3 ) show that a specific gene controls the number of gyri that form in a region of the cerebral cortex that includes Broca's area (the major language area). This begins to pinpoint mechanisms that underlie the development of specialized regions of the human brain and may be relevant to understanding human brain evolution.