title: Passive or simulated displacement of one arm (but not its mirror reflection) modulates the involuntary motor behavior of the other arm.
abstract: Recent studies of both healthy and patient populations have cast doubt on the mirror paradigm's beneficial effect on motor behavior. Indeed, the voluntary arm displacement that accompanies reflection in the mirror may be the determining factor in terms of the motor behavior of the contralateral arm. The objective of the present study was to assess the respective effects of mirror reflection and arm displacement (whether real or simulated) on involuntary motor behavior of the contralateral arm following sustained, isometric contraction (Kohnstamm phenomenon). Our results revealed that (i) passive displacement of one arm (displacement of the left arm via a motorized manipulandum moving at 4°/s) influenced the velocity of the Kohnstamm phenomenon (forearm flexion occurring shortly after the cessation of muscle contraction) in the contralateral arm and (ii) mirror vision had no effect. Indeed, the velocity of the Kohnstamm phenomenon tended to be adjusted to match the velocity of the passive displacement of the other arm. In a second experiment, arm displacement was simulated by vibrating the triceps at 25, 50 or 75 Hz. Results showed that the velocity of the Kohnstamm phenomenon in one arm increased with the vibration frequency applied to the other arm. Our results revealed the occurrence of bimanual coupling because involuntary displacement of one arm was regulated by muscle-related information generated by the actual or simulated displacement of the other arm. In line with the literature data on voluntary motor behavior, our study failed to evidence an additional impact of mirror vision on involuntary motor behavior.
authors.affiliation: Univ. Savoie, LPNC, F-7300 UMR 5105 Chambéry, CNRS, France.
authors.forename: C
authors.initials: C
authors.lastname: Brun
authors.affiliation: Univ. Savoie, LPNC, F-7300 UMR 5105 Chambéry, CNRS, France; Univ. Lille 3, Laboratory of Functional Neurosciences and Pathologies, EA 4559, Villeneuve d'Ascq, France.
authors.forename: M
authors.initials: M
authors.lastname: Metral
authors.affiliation: Univ. Savoie, LPNC, F-7300 UMR 5105 Chambéry, CNRS, France; Aix-Marseille Univ. CNRS, LNIA UMR 7260, Marseille, France.
authors.forename: M
authors.initials: M
authors.lastname: Chancel
authors.affiliation: Aix-Marseille Univ. CNRS, LNIA UMR 7260, Marseille, France.
authors.forename: A
authors.initials: A
authors.lastname: Kavounoudias
authors.affiliation: Univ. Lille 3, Laboratory of Functional Neurosciences and Pathologies, EA 4559, Villeneuve d'Ascq, France.
authors.forename: M
authors.initials: M
authors.lastname: Luyat
authors.affiliation: Univ. Savoie, LPNC, F-7300 UMR 5105 Chambéry, CNRS, France. Electronic address: Michel.guerraz@univ-savoie.fr.
authors.forename: M
authors.initials: M
authors.lastname: Guerraz
mesh_terms: D001132:Arm / Q000502:physiology*; D004576:Electromyography; D005260:Female; D006801:Humans; D007088:Illusions; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D010812:Physical Stimulation; D011434:Proprioception / Q000502:physiology*; D014732:Vibration; D014796:Visual Perception; D055815:Young Adult
keywords: Kohnstamm phenomenon; bimanual coupling; mirror paradigm; muscular afferents