Intensity-dependent regional cerebral blood flow during 1-Hz repetitive transcranial magnetic stimulation (rTMS) in healthy volunteers studies with H2150 positron emission tomography: II. Effects of prefrontal cortex rTMS - Speer, AM; Willis, MW; Herscovitch, P; Daube-Witherspoon, M; Shelton, JR; Benson, BE; Post, RM; Wassermann, EM (Biol Psychiatry, 2003)