The purpose of this study is to identify genes responsible for epilepsy and disorders of human cognition (EDHC). The Walsh Laboratory at the Children's Hospital Boston and Beth Israel Deaconess Medical Center is looking for genes involved in brain development. Conditions that we study include brain malformations, such as polymicrogyria, lissencephaly, Walker-Warburg syndrome, heterotopias, and cerebellar hypoplasia, and inherited disorders of cognition, such as familial mental retardation and familial autism; people with these conditions also often have epilepsy. The structural brain abnormalities are usually diagnosed by brain MRI or sometimes CT scans. Adults and children with these conditions, and their family members, are invited to participate in our study. By comparing the DNA of individuals or families that carry EDHC to the DNA of people in the general population, it may be possible to learn more about the genetic bases of certain forms of EDHC.