title: Human cervical spinal cord circuitry activated by tonic input can generate rhythmic arm movements.
abstract: The coordination between arms and legs during human locomotion shares many features with that in quadrupeds, yet there is limited evidence for the central pattern generator for the upper limbs in humans. Here we investigated whether different types of tonic stimulation, previously used for eliciting stepping-like leg movements, may evoke nonvoluntary rhythmic arm movements. Twenty healthy subjects participated in this study. The subject was lying on the side, the trunk was fixed, and all four limbs were suspended in a gravity neutral position, allowing unrestricted low-friction limb movements in the horizontal plane. The results showed that peripheral sensory stimulation (continuous muscle vibration) and central tonic activation (postcontraction state of neuronal networks following a long-lasting isometric voluntary effort, Kohnstamm phenomenon) could evoke nonvoluntary rhythmic arm movements in most subjects. In ∼40% of subjects, tonic stimulation elicited nonvoluntary rhythmic arm movements together with rhythmic movements of suspended legs. The fact that not all participants exhibited nonvoluntary limb oscillations may reflect interindividual differences in responsiveness of spinal pattern generation circuitry to its activation. The occurrence and the characteristics of induced movements highlight the rhythmogenesis capacity of cervical neuronal circuitries, complementing the growing body of work on the quadrupedal nature of human gait.
authors.affiliation: Laboratory of Neurobiology of Motor Control, Institute for Information Transmission Problems, Moscow, Russia; solopova@iitp.ru.
authors.forename: I A
authors.initials: IA
authors.lastname: Solopova
authors.affiliation: Laboratory of Neurobiology of Motor Control, Institute for Information Transmission Problems, Moscow, Russia;
authors.forename: V A
authors.initials: VA
authors.lastname: Selionov
authors.affiliation: Laboratory of Neurobiology of Motor Control, Institute for Information Transmission Problems, Moscow, Russia;
authors.forename: D S
authors.initials: DS
authors.lastname: Zhvansky
authors.affiliation: Biomedical Engineering Department, Oregon Health and Science University, Portland, Oregon; and.
authors.forename: V S
authors.initials: VS
authors.lastname: Gurfinkel
authors.affiliation: Laboratory of Neuromotor Physiology, Fondazione Santa Lucia, Rome, Italy.
authors.forename: Y
authors.initials: Y
authors.lastname: Ivanenko
mesh_terms: D000328:Adult; D000368:Aged; D001132:Arm / Q000294:innervation / Q000502:physiology*; D066193:Cervical Cord / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D005684:Gait; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D009068:Movement; D010507:Periodicity; D010525:Peripheral Nerves / Q000502:physiology; D011984:Sensory Receptor Cells / Q000502:physiology
keywords: Kohnstamm phenomenon; arm-leg coordination; central pattern generator; human cervical spinal cord; sensory stimulation