A 79-year-old man with poorly controlled Parkinson’s disease was scheduled for implantation of electrodes for deep brain stimulation under mild sedation. He was right-handed, English-speaking, and oriented to time and place. His memory was good, but he had a marked tremor. Current medications included levodopa, bromocriptine, selegiline, pramipexole and amantadine, all of which had been withheld for 24 hours to allow the surgeon to recognize when he