title: Corticospinal Excitability in the Hand Muscles is Decreased During Eye Movement with Visual Occlusion.
abstract: Corticospinal excitability in the hand muscles decreases during smooth pursuit eye movement. The present study tested a hypothesis that the decrease in corticospinal excitability in the hand muscles at rest during eye movement is not caused by visual feedback but caused by motor commands to the eye muscles. Healthy men (M age = 28.4 yr., SD = 5.2) moved their eyes to the right with visual occlusion (dark goggles) while their arms and hands remained at rest. The motor-evoked potential in the hand muscles was suppressed by 19% in the third quarter of the eye-movement period, supporting a view that motor commands to the eye muscles are the cause of the decrease in corticospinal excitability in the hand muscles. The amount of the suppression was not significantly different among the muscles, indicating that modulation of corticospinal excitability in one muscle induced by eye movement is not dependent on whether eye movement direction and the direction of finger movement when the muscle contracts are identical. Thus, the finding failed to support a hypothetical view that motor commands to the eye muscles concomittantly produce motor commands to the hand muscles. Moreover, the amount of the suppression was not significantly different between the forearm positions, indicating that the suppression was not affected by proprioception of the forearm muscles when visual feedback is absent.
authors.affiliation: Graduate School of Comprehensive Rehabilitation, Osaka Prefecture University, Japan.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Chujo
authors.affiliation: Graduate School of Comprehensive Rehabilitation, Osaka Prefecture University, Japan.
authors.forename: Yasutomo
authors.initials: Y
authors.lastname: Jono
authors.affiliation: Graduate School of Comprehensive Rehabilitation, Osaka Prefecture University, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Tani
authors.affiliation: Graduate School of Comprehensive Rehabilitation, Osaka Prefecture University, Japan.
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Nomura
authors.affiliation: College of Health and Human Sciences, Osaka Prefecture University, Japan hiraoka@rehab.osakafu-u.ac.jp.
authors.forename: Koichi
authors.initials: K
authors.lastname: Hiraoka
mesh_terms: D000328:Adult; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005133:Eye Movements / Q000502:physiology*; D005542:Forearm / Q000502:physiology; D006225:Hand / Q000502:physiology*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D011434:Proprioception / Q000502:physiology; D011712:Pyramidal Tracts / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: corticospinal excitability; eye movement; eye-hand coordination; hand muscles