Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Parkinson's Disease ?
    ### Response:
    A Shortage of Dopamine Parkinson's disease occurs when nerve cells, or neurons, in an area of the brain that controls movement become impaired and/or die. Normally, these neurons produce an important brain chemical known as dopamine, but when the neurons die or become impaired, they produce less dopamine.
    