Effects of Flocculectomy on Vestibular and Optokinetic Nystagmus and Unit Activity in the Vestibular Nuclei

2015 ◽  
pp. 226-229 ◽  
Author(s):  
Walter Waespe ◽  
Bernard Cohen ◽  
Theodore Raphan
Keyword(s):  
Unit Activity ◽  
Optokinetic Nystagmus ◽  
Vestibular Nuclei

Spatial orientation of the angular vestibulo-ocular reflex

1999 ◽  
Vol 9 (3) ◽  
pp. 163-172
Author(s):  
Bernard Cohen ◽  
Susan Wearne ◽  
Mingjia Dai ◽  
Theodore Raphan
Keyword(s):  
Spatial Orientation ◽  
Optokinetic Nystagmus ◽  
Vestibular Nuclei ◽  
Velocity Storage ◽  
Gravitational Acceleration ◽  
Ocular Reflex ◽  
Eye Rotation ◽  
Slow Velocity ◽  
Vestibulo Ocular Reflex ◽  
Vector Sum

During vestibular nystagmus, optokinetic nystagmus (OKN), and optokinetic afternystagmus (OKAN), the axis of eye rotation tends to align with the vector sum of linear accelerations acting on the head. This includes gravitational acceleration and the linear accelerations generated by translation and centrifugation. We define the summed vector of gravitational and linear accelerations as gravito-inertial acceleration (GIA) and designate the phenomenon of alignment as spatial orientation of the angular vestibuloocular reflex (aVOR). On the basis of studies in the monkey, we postulated that the spatial orientation of the aVOR is dependent on the slow (velocity storage) component of the aVOR, not on the short latency, compensatory aVOR component, which is in head-fixed coordinates. Experiments in which velocity storage was abolished by midline medullary section support this postulate. The velocity storage component of the aVOR is likely to be generated in the vestibular nuclei, and its spatial orientation was shown to be controlled through the nodulus and uvula of the vestibulo-cerebellum. Separate regions of the nodulus/uvula appear to affect the horizontal and vertical/torsional components of the response differently. Velocity storage is weaker in humans than in monkeys, but responds in a similar fashion in both species. We postulate that spatial orientation of the aVOR plays an important role in aligning gaze with the GIA and in maintaining balance during angular locomotion.

Neurons of the medial terminal accessory optic nucleus of the rat are poorly collateralized

1989 ◽  
Vol 2 (3) ◽  
pp. 269-273 ◽  
Author(s):  
R. J. Clarke ◽  
R. A. Giolli ◽  
R. H. Blanks ◽  
Y. Torigoe ◽  
J. H. Fallon
Keyword(s):  
Optokinetic Nystagmus ◽  
Inferior Olive ◽  
Previous Analysis ◽  
Optic Tract ◽  
Vestibular Nuclei ◽  
The Other ◽  
Projection Neurons ◽  
Double Labeling ◽  
Cell Counts ◽  
Brainstem Nuclei

AbstractThe vast majority of neurons of the rat medial terminal nucleus (MTN) project to the nucleus of the optic tract (NOT), but the MTN also projects to a lesser degree upon a number of other brainstem nuclei controlling optokinetic nystagmus. Because of the diversity of targets of the MTN, it is possible that individual neurons have branched axons that project to two or more brainstem nuclei. The possibility that axons of MTN-NOT neurons collateralize to innervate other MTN targets is examined in the rat with the fluorescent, double-labeling, retrograde tracer technique. Fluoro-Gold was injected into the NOT while Fast Blue was simultaneously injected into each of five other known targets of the MTN: the supraoculomotor-periaqueductal gray; the dorsal cap of the inferior olive; the visual tegmental relay zone; the dorsolateral nucleus of the basal pons; and the superior/lateral vestibular nuclei. Brainstem sections were processed for fluorescence microscopy and the MTN was examined for single- and double-labeled neurons. Results show that virtually all neurons of the MTN (>97.5%), together with neurons in the visual tegmental relay zone immediately surrounding the MTNd, are single-labeled in all paired injections involving the NOT and the other target nuclei. It was found that about 69% of MTN neurons project exclusively to the NOT, 5–10% project to each one of the other nuclei, and 3% of MTN neurons project to more than one target. Based upon cell counts from the fluorescent material, and previous analysis of Nissl-stained serial sections, the findings show that virtually all MTN neurons are projection neurons. It was concluded that the MTN is comprised of independent projection systems, possibly involved in different aspects of generating optokinetic nystagmus.

Optokinetic nystagmus and the vestibular nuclei

1974 ◽  
Vol 42 (1) ◽  
pp. 158-168 ◽  
Author(s):  
G.B. Azzena ◽  
M.T. Azzena ◽  
R. Marini
Keyword(s):  
Optokinetic Nystagmus ◽  
Vestibular Nuclei

Neuron activity in monkey vestibular nuclei during vertical vestibular stimulation and eye movements

1984 ◽  
Vol 52 (4) ◽  
pp. 724-742 ◽  
Author(s):  
M. C. Chubb ◽  
A. F. Fuchs ◽  
C. A. Scudder
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
Unit Activity ◽  
Vestibular Nuclei ◽  
Vestibular Stimulation ◽  
Head Movements ◽  
Medial Longitudinal Fasciculus ◽  
Eye Position ◽  
Head Velocity ◽  
Eye Velocity

To elucidate how information is processed in the vestibuloocular reflex (VOR) pathways subserving vertical eye movements, extracellular single-unit recordings were obtained from the vestibular nuclei of alert monkeys trained to track a visual target with their eyes while undergoing sinusoidal pitch oscillations (0.2-1.0 Hz). Units with activity related to vertical vestibular stimulation and/or eye movements were classified as either vestibular units (n = 53), vestibular plus eye-position units (n = 30), pursuit units (n = 10), or miscellaneous units (n = 5), which had various combinations of head- and eye-movement sensitivities. Vestibular units discharged in relation to head rotation, but not to smooth eye movements. On average, these units fired approximately in phase with head velocity; however, a broad range of phase shifts was observed. The activities of 8% of the vestibular units were related to saccades. Vestibular plus eye-position units fired in relation to head velocity and eye position and, in addition, usually to eye velocity. Their discharge rates increased for eye and head movements in opposite directions. During combined head and eye movements, the modulation in unit activity was not significantly different from the sum of the modulations during each alone. For saccades, the unit firing rate either decreased to zero or was unaffected. Pursuit units discharged in relation to eye position, eye velocity, or both, but not to head movements alone. For saccades, unit activity usually either paused or was unaffected. The eye-movement-related activities of the vestibular plus eye-position and pursuit units were not significantly different. A quantitative comparison of their firing patterns suggests that vestibular, vestibular plus eye-position, and pursuit neurons in the vestibular nucleus could provide mossy fiber inputs to the flocculus. In addition, the vertical vestibular plus eye-position neurons have discharge patterns similar to those of fibers recorded rostrally in the medial longitudinal fasciculus. Therefore, our data support the view that vertical vestibular plus eye-position neurons are interneurons of the VOR.

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