title: Stimulus-response profile during single-pulse transcranial magnetic stimulation to the primary motor cortex.
abstract: We examined the stimulus-response profile during single-pulse transcranial magnetic stimulation (TMS) by measuring motor-evoked potentials (MEPs) with electromyographic monitoring and hemodynamic responses with functional magnetic resonance imaging (fMRI) at 3 Tesla. In 16 healthy subjects, single TMS pulses were irregularly delivered to the left primary motor cortex at a mean frequency of 0.15 Hz with a wide range of stimulus intensities. The measurement of MEP proved a typical relationship between stimulus intensity and MEP amplitude in the concurrent TMS-fMRI environment. In the population-level analysis of the suprathreshold stimulation conditions, significant increases in hemodynamic responses were detected in the motor/somatosensory network, reflecting both direct and remote effects of TMS, and also the auditory/cognitive areas, perhaps related to detection of clicks. The stimulus-response profile showed both linear and nonlinear components in the direct and remote motor/somatosensory network. A detailed analysis suggested that the nonlinear components of the motor/somatosensory network activity might be induced by nonlinear recruitment of neurons in addition to sensory afferents resulting from movement. These findings expand our basic knowledge of the quantitative relationship between TMS-induced neural activations and hemodynamic signals measured by neuroimaging techniques.
authors.affiliation: Department of Cortical Function Disorders, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira 187-8502, Japan. hanakawa@ncnp.go.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Hanakawa
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Mima
authors.forename: Riki
authors.initials: R
authors.lastname: Matsumoto
authors.forename: Mitsunari
authors.initials: M
authors.lastname: Abe
authors.forename: Morito
authors.initials: M
authors.lastname: Inouchi
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Urayama
authors.forename: Kimitaka
authors.initials: K
authors.lastname: Anami
authors.forename: Manabu
authors.initials: M
authors.lastname: Honda
authors.forename: Hidenao
authors.initials: H
authors.lastname: Fukuyama
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D055815:Young Adult