Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Progressive bulbar palsy ?
    ### Response:
    Progressive bulbar palsy involves the brain stem. The brain stem is the part of the brain needed for swallowing, speaking, chewing, and other functions. Signs and symptoms of progressive bulbar palsy include difficulty swallowing, weak jaw and facial muscles, progressive loss of speech, and weakening of the tongue.
    