title: Locating the motor cortex on the MRI with transcranial magnetic stimulation and PET.
abstract: Transcranial magnetic stimulation with a focal coil was used to map the cortical representation of a hand muscle in four healthy subjects. In each subject, the three-dimensional locations of the magnetic stimulation positions and about 400 positions on the surface of the head were digitized. The amplitude-weighted center of gravity of each subject's map was found, and a line perpendicular to the local head surface was projected inward. The digitized heads were registered with the subjects' MRIs using the scalp contours. The coordinate transformations yielded by this process were used to map the stimulation positions and the perpendicular line into the MRIs. Brain areas imaged with positron emission tomography (PET) and 15O-labeled water, activated by movement of the same muscle, were registered with the MRIs using the brain contours. In all cases, the magnetic stimulation lines encountered the surface of the brain at the anterior lip of the central sulcus and ran along the precentral gyrus a few millimeters anterior to the central sulcus, coming within 5-22 mm of all the PET activation maxima. This technique demonstrates the accuracy of transcranial magnetic stimulation for locating the primary motor area.
authors.affiliation: Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-1428, USA.
authors.forename: E M
authors.initials: EM
authors.lastname: Wassermann
authors.forename: B
authors.initials: B
authors.lastname: Wang
authors.forename: T A
authors.initials: TA
authors.lastname: Zeffiro
authors.forename: N
authors.initials: N
authors.lastname: Sadato
authors.forename: A
authors.initials: A
authors.lastname: Pascual-Leone
authors.forename: C
authors.initials: C
authors.lastname: Toro
authors.forename: M
authors.initials: M
authors.lastname: Hallett
mesh_terms: D000328:Adult; D000465:Algorithms; D001931:Brain Mapping / Q000295:instrumentation*; D003199:Computer Systems; D004574:Electromagnetic Fields; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008297:Male; D009044:Motor Cortex / Q000033:anatomy & histology / Q000502:physiology*; D012016:Reference Values; D014055:Tomography, Emission-Computed / Q000295:instrumentation*