title: Sensorimotor event-related desynchronization represents the excitability of human spinal motoneurons.
abstract: Amplitudes of mu and beta (7-26Hz) oscillations measured by electroencephalography over the sensorimotor areas are suppressed during motor imagery as well as during voluntary movements. This phenomenon is referred to as event-related desynchronization (ERD) and is known to reflect motor cortical excitability. The increased motor cortical excitability associated with ERD during hand motor imagery would induce a descending cortical volley to spinal motoneurons, resulting in facilitation of spinal motoneuronal excitability. Therefore, in the present study, we tested the association of ERD during motor imagery with the excitability of spinal motoneurons in 15 healthy participants. Spinal excitability was tested using the F-wave recorded from the right abductor pollicis brevis muscle. The F-wave results from antidromic activation of spinal motoneurons and is induced by peripheral nerve stimulation. Participants performed 5s of motor imagery of right thumb abduction following 7s of rest. The right median nerve was stimulated at wrist level when the ERD magnitude of the contralateral hand sensorimotor area exceeded predetermined thresholds during motor imagery. The results showed ERD magnitude during hand motor imagery was associated with an increase in F-wave persistence, but not with the response average of F-wave amplitude or F-wave latency. These findings suggest that the ERD magnitude may be a biomarker representing increases in the excitability of both cortical and spinal levels.
authors.affiliation: School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Kanagawa, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Takemi
authors.affiliation: Department of Rehabilitation Medicine, Tokai University School of Medicine, Kanagawa, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Masakado
authors.affiliation: Department of Rehabilitation Medicine, Keio University School of Medicine, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Liu
authors.affiliation: Department of Rehabilitation Medicine, Keio University School of Medicine, Tokyo, Japan; Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Kanagawa, Japan. Electronic address: ushiba@brain.bio.keio.ac.jp.
authors.forename: J
authors.initials: J
authors.lastname: Ushiba
mesh_terms: D000704:Analysis of Variance; D001931:Brain Mapping; D003344:Cortical Synchronization / Q000502:physiology*; D004558:Electric Stimulation; D004569:Electroencephalography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D056228:Feedback, Sensory; D005260:Female; D006801:Humans; D007092:Imagination / Q000502:physiology; D008297:Male; D008475:Median Nerve / Q000502:physiology; D009046:Motor Neurons / Q000502:physiology*; D066191:Sensorimotor Cortex / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology*; D055815:Young Adult
keywords: F-wave; cortical oscillations; electroencephalography; motor imagery; spinal excitability