Histologically, the cerebral cortex in LIS1-associated lissencephaly consists of four layers: a poorly defined marginal zone, which, however, has a very high cell density; a superficial neuronal layer with diffusely scattered neurons; a deeper neuronal layer with relatively sparse neurons; and a deepest neuronal layer with neurons arranged in columns. The gene discussed is PAFAH1B1; the disease is Lissencephaly.