Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) polymicrogyria ?
    ### Response:
    Polymicrogyria is a condition characterized by abnormal development of the brain before birth. The surface of the brain normally has many ridges or folds, called gyri. In people with polymicrogyria, the brain develops too many folds, and the folds are unusually small.
    