title: Intensity-dependent regional cerebral blood flow during 1-Hz repetitive transcranial magnetic stimulation (rTMS) in healthy volunteers studied with H215O positron emission tomography: I. Effects of primary motor cortex rTMS.
abstract: BACKGROUND
  Repetitive transcranial magnetic stimulation (rTMS) affects the excitability of the motor cortex and is thought to influence activity in other brain areas as well. We combined the administration of varying intensities of 1-Hz rTMS of the motor cortex with simultaneous positron emission tomography (PET) to delineate local and distant effects on brain activity.
  
  
  METHODS
  Ten healthy subjects received 1-Hz rTMS to the optimal position over motor cortex (M1) for producing a twitch in the right hand at 80, 90, 100, 110, and 120% of the twitch threshold, while regional cerebral blood flow (rCBF) was measured using H(2)(15)O and PET. Repetitive transcranial magnetic stimulation (rTMS) was delivered in 75-pulse trains at each intensity every 10 min through a figure-eight coil. The regional relationship of stimulation intensity to normalized rCBF was assessed statistically.
  
  
  RESULTS
  Intensity-dependent rCBF increases were produced under the M1 stimulation site in ipsilateral primary auditory cortex, contralateral cerebellum, and bilateral putamen, insula, and red nucleus. Intensity-dependent reductions in rCBF occurred in contralateral frontal and parietal cortices and bilateral anterior cingulate gyrus and occipital cortex.
  
  
  CONCLUSIONS
  This study demonstrates that 1-Hz rTMS delivered to the primary motor cortex (M1) produces intensity-dependent increases in brain activity locally and has associated effects in distant sites with known connections to M1.
authors.affiliation: Biological Psychiatry Branch, National Institute of Mental Health, National Institutes of Health, Building 10 Room 5N234, Bethesda, MD 20892-1430, USA.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Speer
authors.forename: Mark W
authors.initials: MW
authors.lastname: Willis
authors.forename: Peter
authors.initials: P
authors.lastname: Herscovitch
authors.forename: Margaret
authors.initials: M
authors.lastname: Daube-Witherspoon
authors.forename: Jennifer Repella
authors.initials: JR
authors.lastname: Shelton
authors.forename: Brenda E
authors.initials: BE
authors.lastname: Benson
authors.forename: Robert M
authors.initials: RM
authors.lastname: Post
authors.forename: Eric M
authors.initials: EM
authors.lastname: Wassermann
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging; D002560:Cerebrovascular Circulation / Q000502:physiology; D004056:Differential Threshold; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000098:blood supply* / Q000000981:diagnostic imaging; D012886:Skull; D014055:Tomography, Emission-Computed; D050781:Transcranial Magnetic Stimulation / Q000295:instrumentation*