Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) isolated lissencephaly sequence ?
    ### Response:
    Isolated lissencephaly sequence (ILS) is a condition that affects brain development before birth. Normally, the cells that make up the exterior of the brain (cerebral cortex) are well-organized, multi-layered, and arranged into many folds and grooves (gyri).
    