Relation Between Axon Morphology in C1 Spinal Cord and Spatial Properties of Medial Vestibulospinal Tract Neurons in the Cat

• Published in: Journal of neurophysiology 1998-01, Vol.79 (1), p.285-303
• Main Authors: Perlmutter, S. I, Iwamoto, Y, Barke, L. F, Baker, J. F, Peterson, B. W
• Format: Article
• Language: English
• Subjects: Afferent Pathways - physiology; Animals; Axonal Transport; Axons - physiology; Axons - ultrastructure; Biotin - analogs & derivatives; Cats; Electric Stimulation; Horseradish Peroxidase; Neurons - physiology; Oculomotor Nerve - physiology; Reaction Time; Space life sciences; Spinal Cord - physiology; Spinal Cord - ultrastructure; Vestibular Nuclei - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.1998.79.1.285

S. I. Perlmutter , Y. Iwamoto , L. F. Barke , J. F. Baker , and B. W. Peterson Department of Physiology, Northwestern University School of Medicine, Chicago, Illinois 60611 Perlmutter, S. I., Y. Iwamoto, L. F. Barke, J. F. Baker, and B. W. Peterson. Relation between axon morphology in C 1 spinal cord and spatial properties of medial vestibulospinal tract neurons in the cat. J. Neurophysiol. 79: 285-303, 1998. Twenty-one secondary medial vestibulospinal tract neurons were recorded intraaxonally in the ventromedial funiculi of the C 1 spinal cord in decerebrate, paralyzed cats. Antidromic stimulation in C 6 and the oculomotor nucleus identified the projection pattern of each neuron. Responses to sinusoidal, whole-body rotations in many planes in three-dimensional space were characterized before injection of horseradish peroxidase or Neurobiotin. The spatial response properties of 19 neurons were described by a maximum activation direction vector (MAD), which defines the axis and direction of rotation that maximally excites the neuron. The other two neurons had spatio-temporal convergent behavior and no MAD was calculated. Collateral morphologies were reconstructed from serial frontal sections to reveal terminal fields in the C 1 gray matter. Axons gave off multiple collaterals that terminated ipsilaterally to the stem axon. Collaterals of individual axons rarely overlapped longitudinally but projected to similar regions in the ventral horn when viewed in transverse sections. The number of primary collaterals in C 1 was different for vestibulo-collic, vestibulo-oculo-collic, and C 6 -projecting neurons: on average one every 1.34, 1.72, and 4.25 mm, respectively. The heaviest arborization and most terminal boutons were seen in the ventral horn, in laminae VIII and IX. Varicosities on terminal branches in lamina IX were observed adjacent to large cell bodies putative neck motoneurons in counterstained tissue. Some collaterals had branches that extended dorsally to lamina VII. Neurons with different spatial properties had terminal fields in different regions of the ventral horn. Axons with type I responses and MADs near those of a semicircular canal pair had widely distributed collateral branches and numerous terminations in the dorsomedial, ventromedial, and spinal accessory nuclei and in lamina VIII. Axons with type I responses that suggested convergent canal pair input, with type II responses, and with spatio-temporal convergent behavior had smaller terminal