In human, neuronal migration disorders form a group of malformations of the brain, which primarily affect development of the cerebral cortex. They are commonly associated with delay in development, mental retardation, and epilepsy. Some form of cortical malformation is frequently observed in patients with epilepsy, the majority of them already presenting seizures in infancy. Mechanisms resulting in these cortical malformations are not well understood, mainly due to the limited number of animal model of these syndromes. We recently discovered a mouse mutant that is characterized by heterotopic cortex, which resembles cortical band heterotopia observed in human cases. These mice have a lowered threshold for epilepsy and behavioral analysis detected important cognitive deficits. The genetical analysis of these mutant mice as well as further functional and structural analysis will provide insight in the pathogenic mechanism that results in cortical heterotopia. Furthermore this model will represent a new tool to investigate new antiepileptic treatments. - see Croquelois, Welker.