Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Neuronal Migration Disorders ?
    ### Response:
    Neuronal migration disorders (NMDs) are a group of birth defects caused by the abnormal migration of neurons in the developing brain and nervous system. In the developing brain, neurons must migrate from the areas where they are born to the areas where they will settle into their proper neural circuits.
    