Convergence of the horizontal semicircular canal and otolith afferents on cat single vestibular neurons

• Published in: Experimental brain research Vol. 140; no. 1; pp. 1 - 11
• Main Authors: ZHANG, X, ZAKIR, M, MENG, H, SATO, H, UCHINO, Y
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01.09.2001; Springer Nature B.V
• Subjects: Afferent Pathways - cytology; Afferent Pathways - physiology; Animals; Biological and medical sciences; Cats - anatomy & histology; Cats - physiology; Convergence; Electric Stimulation; Evoked Potentials - physiology; Excitatory Postsynaptic Potentials - physiology; Fundamental and applied biological sciences. Psychology; Motion Perception - physiology; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Nerves; Neural Conduction - physiology; Neurons; Neurons - cytology; Neurons - physiology; Oculomotor Nerve - cytology; Oculomotor Nerve - physiology; Orientation - physiology; Otolithic Membrane - cytology; Otolithic Membrane - physiology; Postural Balance - physiology; Reaction Time - physiology; Saccule; Semicircular canals; Semicircular Canals - cytology; Semicircular Canals - physiology; Sensory neurons; Spinal cord; Spinal Cord - cytology; Spinal Cord - physiology; Synapses - physiology; Synaptic Transmission - physiology; Vertebrates: nervous system and sense organs; Vestibular Nerve - cytology; Vestibular Nerve - physiology; Vestibular nuclei; Vestibular Nuclei - cytology; Vestibular Nuclei - physiology; Vestibular system; vestibulo-collic reflex; Vestibulocollic reflex; Vestibulospinal tract; Fissipedia; Carnivora; Central nervous system; Discharge pattern; Electrophysiology; Saccule; Inner ear; Convergence; Vertebrata; Mammalia; Semicircular canal; Vestibular nucleus; Otolith; Vestibular pathway; Cat; Vestibulocollic reflex; Vestibular system; Utricle; Utricular nerve; Brain (vertebrata)
• ISSN: 0014-4819; 1432-1106
• DOI: 10.1007/s002210100764

We studied the convergence of two afferent pairs of single vestibular neurons by selective stimulation of the horizontal semicircular canal (HC) and saccular (SAC) nerves, and the HC and utricular (UT) nerves in decerebrate cats. All recorded neurons were classified as vestibulospinal (VS), vestibulo-oculospinal (VOS) or vestibulo-ocular (VO), by antidromic stimulation from the oculomotor/trochlear nuclei and the spinal cord: neurons that could not be activated from any test sites were classified as vestibular (V) neurons. Of a total of 125 neurons activated by stimulation of the HC/SAC nerves, 21(17%) received convergent inputs. Twelve of 21 neurons received monosynaptic excitatory inputs from both nerves. About half (9/21, 43%) of the convergent neurons were classified as VS neurons, the majority of which descended through the ipsilateral lateral vestibulospinal tract (i-LVST). The HC/SAC convergent neurons were located in the rostral part of the descending, the medial and the caudal-ventral part of the lateral vestibular nucleus. In 80 neurons studied by stimulation of the HC/UT nerves, both inputs converged in 12 (15%) neurons, more than half of which were VS neurons. Eight of 12 convergent neurons received excitatory inputs followed by inhibition from both the HC and UT nerves. A few convergent neurons (3/12) projected to the oculomotor/trochlear nucleus. Half of the convergent and non-convergent VS neurons descended to the spinal cord through the i-LVST, and the only one VOS convergent neuron via the medial vestibulospinal tract. Most of the convergent neurons were located in the lateral, the rostral part of the descending and medial vestibular nucleus. The percentages of HC/SAC and HC/UT convergence were half those of the posterior semicircular canal (PC), PC/SAC (33%) and PC/UT (33%) convergence, respectively. The convergent neurons receiving the HC and otolith inputs may contribute at least partly to the vestibulocollic reflex.