Eye movement related activity and morphology of second order vestibular neurons terminating in the cat abducens nucleus

SummaryIntracellular records were obtained from axons of second order vestibular neurons in, and around, the left abducens nucleus in alert cats implanted with stimulating electrodes on both vestibular nerves and the left VIth nerve. Twelve secondary vestibular neurons were identified by their increase in firing rate with horizontal head rotation to the left and/or increasing eye position to the right. Following HRP injection, somatic location, axonal trajectory and termination sites were determined. Each of the above cells collateralized extensively in the abducens nucleus in a fashion consistent with their being either inhibitory (n = 7; left) or excitatory (n = 6; right) vestibular neurons in the disynaptic horizontal vestibulo-ocular reflex pathway. These vestibular neurons also arborized extensively in other posterior brainstem eye-movement related areas as well as sending an axon to the spinal cord.

[1]  R. Gacek.  Location of abducens afferent neurons in the cat , 1979, Experimental Neurology.

[2]  F. Miles,et al.  Single unit firing patterns in the vestibular nuclei related to voluntary eye movements and passive body rotation in conscious monkeys. , 1974, Brain research.

[3]  R. G. Baker,et al.  Postsynaptic potentials in abducens motoneurons induced by vestibular stimulation. , 1969, Brain research.

[4]  E. Keller,et al.  Oculomotor related interaction of vestibular and visual stimulation in vestibular nucleus cells in alert monkey , 1975, Experimental Neurology.

[5]  D. Robinson,et al.  Oculomotor signals in medial longitudinal fasciculus of the monkey. , 1978, Journal of neurophysiology.

[6]  Edward L. Keller,et al.  Characteristics of head rotation and eye movement-related neurons in alert monkey vestibular nucleus , 1975, Brain Research.

[7]  R. Gacek.  Anatomical demonstration of the vestibulo‐ocular projections in the cat , 1971, Acta oto-laryngologica. Supplementum.

[8]  O. Hikosaka,et al.  Presynaptic impulses in the abducens nucleus and their relation to postsynaptic potentials in motoneurons during vestibular nystagmus , 1977, Experimental Brain Research.

[9]  A. Berthoz,et al.  Organization of vestibular nystagmus in oblique oculomotor system. , 1974, Journal of neurophysiology.

[10]  A. Fuchs,et al.  Unit activity in vestibular nucleus of the alert monkey during horizontal angular acceleration and eye movement. , 1975, Journal of neurophysiology.

[11]  N. Ishizuka,et al.  Axonal branches and terminations in the cat abducens nucleus of secondary vestibular neurons in the horizontal canal system , 1980, Neuroscience Letters.

[12]  A. Fuchs,et al.  Responses of fibers in medial longitudinal fasciculus (MLF) of alert monkeys during horizontal and vertical conjugate eye movements evoked by vestibular or visual stimuli. , 1976, Journal of neurophysiology.

[13]  S. Highstein,et al.  The ascending tract of Deiters' conveys a head velocity signal to medial rectus motoneurons , 1979, Brain Research.

[14]  Y. Shinoda,et al.  Rhythmic activities of secondary vestibular efferent fibers recorded within the abducens nucleus during vestibular nystagmus. , 1971, Brain research.

[15]  C. Kaneko,et al.  Vestibular and medullary brain stem afferents to the abducens nucleus in the cat , 1977, Brain Research.

[16]  L. Maffei,et al.  Spatial frequency and orientation tuning curves of visual neurones in the cat: Effects of mean luminance , 1977, Experimental Brain Research.