title: Facilitation from flexor digitorum superficialis to extensor carpi radialis in humans.
abstract: Effects of low-threshold afferents from the flexor digitorum superficialis (FDS) to the extensor carpi radialis (ECR) motoneurons were examined using a post-stimulus time-histogram (PSTH) and electromyogram-averaging (EMG-A) methods in eight healthy human subjects. In the PSTH study in five of the eight subjects, electrical conditioning stimuli (ES) to the median nerve branch innervating FDS with the intensity below the motor threshold induced excitatory effects (facilitation) in 39 out of 92 ECR motor units. In 11 ECR motor units, the central synaptic delay of the facilitation was -0.1 ± 0.3 ms longer than that of the homonymous facilitation of ECR. Mechanical conditioning stimuli (MS) to FDS with the intensity below the threshold of the tendon(T)-wave-induced facilitation in 51 out of 51 ECR motor units. With the EMG-A method, early and significant peaks were produced by ES and MS in all the eight subjects. The difference between latencies of the peaks by ES and MS was almost equivalent to that of the Hoffmann- and T-waves of FDS by ES and MS. The peak was diminished by tonic vibration stimuli to FDS. These findings suggest that a facilitation from FDS to ECR exists in humans and group Ia afferents mediate the facilitation through a monosynaptic path.
authors.affiliation: Department of Anatomy and Structural Science, Yamagata University School of Medicine, 2-2-2, Iida-nishi, Yamagata, 990-9585, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Nito
authors.affiliation: Department of Anatomy and Structural Science, Yamagata University School of Medicine, 2-2-2, Iida-nishi, Yamagata, 990-9585, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Hashizume
authors.affiliation: Department of Judo Therapy, Teikyo University Faculty of Medical Technology, Utsunomiya, Japan.
authors.forename: Takuji
authors.initials: T
authors.lastname: Miyasaka
authors.affiliation: Department of Physical Therapy, Yamagata Prefectural University of Health Sciences, Yamagata, Japan.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Department of Occupational Therapy, Yamagata Prefectural University of Health Sciences, Yamagata, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Sato
authors.affiliation: Department of Occupational Therapy, Yamagata Prefectural University of Health Sciences, Yamagata, Japan.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Fujii
authors.affiliation: Graduate School of Health Sciences, Matsumoto University, Matsumoto, Japan.
authors.forename: Masaomi
authors.initials: M
authors.lastname: Shindo
authors.affiliation: Department of Anatomy and Structural Science, Yamagata University School of Medicine, 2-2-2, Iida-nishi, Yamagata, 990-9585, Japan. anaitoh@med.id.yamagata-u.ac.jp.
authors.forename: Akira
authors.initials: A
authors.lastname: Naito
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D005385:Fingers / Q000294:innervation / Q000502:physiology*; D005542:Forearm / Q000294:innervation / Q000502:physiology*; D006801:Humans; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010812:Physical Stimulation; D012023:Reflex, Monosynaptic / Q000502:physiology*; D055815:Young Adult
keywords: Electromyogram-averaging method; Extensor carpi radialis; Flexor digitorum superficialis; Group Ia monosynaptic path; Humans; Post-stimulus time-histogram method