Experimentally induced cortical malformations in rats.

Different cortical malformations were produced in rats by a single dose of X-rays (200 cGy) given on different days during gestation. These include large cortical ectopic masses after irradiation on day 14; segmentation of the cerebral cortex following irradiation on days 15, 17, 19; and a four-layered "lissencephalic" cortex following irradiation on day 16. Other types of cortical malformation were produced in rats aged 0-2 days by one of the following procedures: focal cortical freezing, focal electrocoagulation, cortical aspiration, and focal brushing of the meninges with a blunt needle covered with cotton. These latter abnormalities include laminar necrosis of layer V, focal cortical dysplasia reminiscent of microgyria, status verrucosus deformis and porencephaly. Experimentally induced cortical malformations in rats can help to increase our understanding of normal and abnormal neurogenesis and organisation of the human cerebral cortex.