title: Excitation threshold of the motor cortex estimated with transcranial magnetic stimulation electroencephalography.
abstract: The excitation threshold of the human motor cortex was estimated on the basis of electroencephalographic responses evoked by transcranial magnetic stimulation. The hand area of the primary motor cortex was stimulated at 10 intensities, for seven healthy individuals. The four dominant peaks of the overall brain response could be reliably determined when stimulation was intense enough to induce a cortical electric field of approximately 33-44 mV/mm. This may be estimated as the threshold for evoking measurable brain activity by motor-cortex transcranial magnetic stimulation. The remarkably low threshold reflects the excellent sensitivity of the combination of transcranial magnetic stimulation and electroencephalography for the study of neuronal function of the cortex.
authors.affiliation: HUS Helsinki Medical Imaging Center, Department of Psychology, University of Helsinki, Helsinki University Central Hospital Laboratory, Finland. soile.komssi@hus.fi
authors.forename: Soile
authors.initials: S
authors.lastname: Komssi
authors.forename: Petri
authors.initials: P
authors.lastname: Savolainen
authors.forename: Juha
authors.initials: J
authors.lastname: Heiskala
authors.forename: Seppo
authors.initials: S
authors.lastname: Kähkönen
mesh_terms: D000328:Adult; D004056:Differential Threshold / Q000502:physiology*; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D050781:Transcranial Magnetic Stimulation