A positron emission tomographic study of subthalamic nucleus stimulation in Parkinson disease: enhanced movement-related activity of motor-association cortex and decreased motor cortex resting activity. - Ceballos-Baumann,A.O.; Boecker,H.; Bartenstein,P.; Falkenhayn,I von.; Riescher,H.; Conrad,B.; Moringlane,J.R.; Alesch,F. (Arch Neurol, 1999)