title: Histological and electrophysiological analysis of the corticospinal pathway to forelimb motoneurons in common marmosets.
abstract: Using histological and electrophysiological methods, we identified the neuroanatomical properties of the common marmoset corticospinal tract (CST), which underlies hand/arm motor control. Biotinylated dextran amine (BDA) was injected into the primary motor cortex to anterogradely label CST axons in the cervical segments, revealing that most CST axons descend in the contralateral dorsolateral funiculus (DLF; 85.0%), and some in the ipsilateral DLF (10.7%). Terminal buttons were mainly found in the contralateral lamina VII of the gray matter, but projection to lamina IX, where forelimb motoneurons are located, was rare. Bilateral projections were more abundant than found in the rat CST, resembling the CST organization of other primates. Intracellular recordings were made from 57 forelimb motoneurons on the contralateral side to stimulation, which revealed no monosynaptic excitatory postsynaptic potentials (EPSPs), but di- or polysynaptic EPSPs and inhibitory synaptic potentials were commonly found. Local field potentials showed monosynaptic excitation mainly in laminae VII, where abundant BDA-labeled CST terminals were observed. These results suggest that direct corticomotoneuronal projection is absent in common marmosets but di- or oligosynaptic effects would be mediated by spinal interneurons.
authors.affiliation: Department of Physiology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kondo
authors.affiliation: School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Kanagawa, Japan.
authors.forename: Yamato
authors.initials: Y
authors.lastname: Yoshihara
authors.affiliation: Department of Physiology, Keio University School of Medicine, Tokyo, Japan; Japan Society for the Promotion of Science, Tokyo, Japan.
authors.forename: Kimika
authors.initials: K
authors.lastname: Yoshino-Saito
authors.affiliation: School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Kanagawa, Japan.
authors.forename: Tomofumi
authors.initials: T
authors.lastname: Sekiguchi
authors.affiliation: School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Kanagawa, Japan.
authors.forename: Akito
authors.initials: A
authors.lastname: Kosugi
authors.affiliation: School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Kanagawa, Japan.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Miyazaki
authors.affiliation: Department of Developmental Physiology, National Institute for Physiological Sciences, Aichi, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Nishimura
authors.affiliation: Division of Regenerative Medicine, Jikei University School of Medicine, Tokyo, Japan.
authors.forename: Hirotaka J
authors.initials: HJ
authors.lastname: Okano
authors.affiliation: Department of Orthopaedic Surgery, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Masaya
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Department of Physiology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Okano
authors.affiliation: Department of Developmental Physiology, National Institute for Physiological Sciences, Aichi, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Isa
authors.affiliation: Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Kanagawa, Japan; Department of Rehabilitation Medicine, Keio University School of Medicine, Tokyo, Japan. Electronic address: ushiba@brain.bio.keio.ac.jp.
authors.forename: Junichi
authors.initials: J
authors.lastname: Ushiba
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology / Q000648:ultrastructure; D002144:Callithrix; D055724:Electrophysiological Phenomena; D019706:Excitatory Postsynaptic Potentials; D005552:Forelimb / Q000294:innervation*; D066128:Gray Matter / Q000502:physiology / Q000648:ultrastructure; D008564:Membrane Potentials; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation*; D009434:Neural Pathways; D011712:Pyramidal Tracts / Q000033:anatomy & histology* / Q000502:physiology*; D066127:White Matter / Q000502:physiology / Q000648:ultrastructure
keywords: Common marmoset; Corticospinal tract; Manual dexterity; Motoneuron; Non-human primate; Segmental interneuron