title: Unconscious modulation of motor cortex excitability revealed with transcranial magnetic stimulation.
abstract: The neuronal effects of sensory events that do not enter conscious awareness have been reported in numerous pathological conditions and in normal subjects. In the present study, unconscious modulation of corticospinal excitability was probed in healthy volunteers with transcranial magnetic stimulation (TMS). TMS-induced motor evoked potentials (MEPs) were collected from the first dorsal interosseus muscle while subjects performed a masked semantic priming task that has been shown to elicit covert motor cortex activations. Our data show that the amplitude of the MEPs is modulated by an unseen prime, in line with temporal patterns revealed with event related potentials. These data confirm previous reports showing specific motor neural responses associated with an unseen visual stimulus and establish TMS as a valuable tool in the study of the neural correlates of consciousness.
authors.affiliation: Laboratory for Magnetic Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA. hugo.theoret@umontreal.ca
authors.forename: Hugo
authors.initials: H
authors.lastname: Théoret
authors.forename: Erin
authors.initials: E
authors.lastname: Halligan
authors.forename: Masahito
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Lotfi
authors.initials: L
authors.lastname: Merabet
authors.forename: Alvaro
authors.initials: A
authors.lastname: Pascual-Leone
mesh_terms: D000328:Adult; D003243:Consciousness / Q000502:physiology*; D003463:Cues; D004569:Electroencephalography; D004574:Electromagnetic Fields; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D010775:Photic Stimulation; D013360:Subliminal Stimulation