Contribution of vestibular nerve irregular afferents to viewing distance-related changes in the vestibulo-ocular reflex

1998 ◽  
Vol 119 (1) ◽  
pp. 116-130 ◽  
Author(s):  
Chiju Chen-Huang ◽  
R. A. McCrea
Keyword(s):  
Vestibular Nerve ◽  
Viewing Distance ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Irregular Afferents

Effects of Unilateral Vestibular Deafferentation on the Linear Vestibulo-Ocular Reflex Evoked by Impulsive Eccentric Roll Rotation

2003 ◽  
Vol 89 (2) ◽  
pp. 969-978 ◽  
Author(s):  
S. T. Aw ◽  
M. J. Todd ◽  
L. A. McGarvie ◽  
A. A. Migliaccio ◽  
G. M. Halmagyi
Keyword(s):  
Rotation Axis ◽  
Normal Subjects ◽  
Stimulus Onset ◽  
Whole Body ◽  
Viewing Distance ◽  
Ocular Reflex ◽  
Significant Difference ◽  
Vestibulo Ocular Reflex ◽  
Unilateral Vestibular Deafferentation ◽  
Eye Velocity

The effects of unilateral vestibular deafferentation (UVD) on the linear vestibulo-ocular reflex (LVOR) were studied by measuring three-dimensional eye movements in seven UVD subjects evoked by impulsive eccentric roll rotation while viewing an earth-fixed target at 200, 300, or 600 mm and comparing their responses to 11 normal subjects. The stimulus, a whole-body roll of approximately 1°, with the eye positioned 815 mm eccentric to the rotation axis, produced an inter-aural linear acceleration of approximately 0.5 g and a roll acceleration of approximately 360°/s2. The responses generated by the LVOR comprise horizontal eye rotations. Horizontal eye velocity at 100 ms from stimulus onset in UVD subjects was significantly lower than in normal subjects for all viewing distances, with no significant difference between ipsilesional and contralesional responses. LVOR acceleration gain, defined as the slope of actual horizontal eye velocity divided by the slope of ideal horizontal eye velocity during a 30-ms period starting 70 ms from stimulus onset, was bilaterally significantly reduced in UVD subjects at all viewing distances. Acceleration gain from all viewing distances was 1.04 ± 0.28 in normal subjects, and in UVD subjects was 0.49 ± 0.23 for ipsilesional and 0.63 ± 0.27 for contralesional acceleration. LVOR enhancement in the first 100 ms by near viewing was still present in UVD subjects. LVOR latency in UVD subjects (approximately 39 ms) was not significantly different from normal subjects (approximately 36 ms). After UVD, LVOR is bilaterally and largely symmetrically reduced, but latency remains unchanged and modulation by viewing distance is still present.

Ocular Motor Responses to Abrupt Interaural Head Translation in Normal Humans

2003 ◽  
Vol 90 (2) ◽  
pp. 887-902 ◽  
Author(s):  
Stefano Ramat ◽  
David S. Zee
Keyword(s):  
Viewing Distance ◽  
Head Acceleration ◽  
Ideal Behavior ◽  
Head Velocity ◽  
Ocular Reflex ◽  
High Acceleration ◽  
Median Position ◽  
Vestibulo Ocular Reflex ◽  
Normal Humans ◽  
Eye Velocity

We characterized the interaural translational vestibulo-ocular reflex (tVOR) in 6 normal humans to brief (∼200 ms), high-acceleration (0.4–1.4 g) stimuli, while they fixed targets at 15 or 30 cm. The latency was 19 ± 5 ms at 15-cm and 20 ± 12 ms at 30-cm viewing. The gain was quantified using the ratio of actual to ideal behavior. The median position gain (at time of peak head velocity) was 0.38 and 0.37, and the median velocity gain, 0.52 and 0.62, at 15- and 30-cm viewing, respectively. These results suggest the tVOR scales proportionally at these viewing distances. Likewise, at both viewing distances, peak eye velocity scaled linearly with peak head velocity and gain was independent of peak head acceleration. A saccade commonly occurred in the compensatory direction, with a greater latency (165 vs. 145 ms) and lesser amplitude (1.8 vs. 3.2 deg) at 30- than 15-cm viewing. Even with saccades, the overall gain at the end of head movement was still considerably undercompensatory (medians 0.68 and 0.77 at 15- and 30-cm viewing). Monocular viewing was also assessed at 15-cm viewing. In 4 of 6 subjects, gains were the same as during binocular viewing and scaled closely with vergence angle. In sum the low tVOR gain and scaling of the response with viewing distance and head velocity extend previous results to higher acceleration stimuli. tVOR latency (∼20 ms) was lower than previously reported. Saccades are an integral part of the tVOR, and also scale with viewing distance.

Human Horizontal Vestibulo-Ocular Reflex Initiation: Effects of Acceleration, Target Distance, and Unilateral Deafferentation

1998 ◽  
Vol 80 (3) ◽  
pp. 1151-1166 ◽  
Author(s):  
Benjamin T. Crane ◽  
Joseph L. Demer
Keyword(s):  
Semicircular Canals ◽  
Linear Acceleration ◽  
Head Rotation ◽  
Target Distance ◽  
Whole Body ◽  
Viewing Distance ◽  
Gaze Stabilization ◽  
Ocular Reflex ◽  
Acceleration Period ◽  
Vestibulo Ocular Reflex

Crane, Benjamin T. and Joseph L. Demer. Human horizontal vestibulo-ocular reflex initiation: effects of acceleration, target distance, and unilateral deafferentation. J. Neurophysiol. 80: 1151–1166, 1998. The vestibulo-ocular reflex (VOR) generates compensatory eye movements in response to angular and linear acceleration sensed by semicircular canals and otoliths respectively. Gaze stabilization demands that responses to linear acceleration be adjusted for viewing distance. This study in humans determined the transient dynamics of VOR initiation during angular and linear acceleration, modification of the VOR by viewing distance, and the effect of unilateral deafferentation. Combinations of unpredictable transient angular and linear head rotation were created by whole body yaw rotation about eccentric axes: 10 cm anterior to eyes, centered between eyes, centered between otoliths, and 20 cm posterior to eyes. Subjects viewed a target 500, 30, or 15 cm away that was extinguished immediately before rotation. There were four stimulus intensities up to a maximum peak acceleration of 2,800°/s2. The normal initial VOR response began 7–10 ms after onset of head rotation. Response gain (eye velocity/head velocity) for near as compared with distant targets was increased as early as 1–11 ms after onset of eye movement; this initial effect was independent of linear acceleration. An otolith mediated effect modified VOR gain depending on both linear acceleration and target distance beginning 25–90 ms after onset of head rotation. For rotational axes anterior to the otoliths, VOR gain for the nearest target was initially higher but later became less than that for the far target. There was no gain correction for the physical separation between the eyes and otoliths. With lower acceleration, there was a nonlinear reduction in the early gain increase with close targets although later otolith-mediated effects were not affected. In subjects with unilateral vestibular deafferentation, the initial VOR was quantitatively normal for rotation toward the intact side. When rotating toward the deafferented side, VOR gain remained less than half of normal for at least the initial 55 ms when head acceleration was highest and was not modulated by target distance. After this initial high acceleration period, gain increased to a degree depending on target distance and axis eccentricity. This behavior suggests that the commissural VOR pathways are not modulated by target distance. These results suggest that the VOR is initially driven by short latency ipsilateral target distance dependent and bilateral target-distance independent canal pathways. After 25 ms, otolith inputs contribute to the target distance dependent pathway. The otolith input later grows to eventually dominate the target distance mediated effect. When otolith input is unavailable the target distance mediated canal component persists. Modulation of canal mediated responses by target distance is a nonlinear effect, most evident for high head accelerations.

Effects of Unilateral Loss of Vestibular Function on the Vestibulo-Ocular Reflex and Postural Control

1989 ◽  
Vol 98 (11) ◽  
pp. 884-889 ◽  
Author(s):  
F. Owen Black ◽  
Robert J. Peterka ◽  
Charlotte L. Shupert ◽  
Lewis M. Nashner
Keyword(s):  
Postural Control ◽  
Time Course ◽  
Normal Values ◽  
Vestibular Function ◽  
Vestibular Nerve ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Eye Velocity ◽  
Surgically Induced

Long-term recovery from surgically induced unilateral loss of vestibular function was studied in 14 patients. Seven patients underwent surgical extirpation or section of the vestibular nerve, and seven patients underwent labyrinthectomy without vestibular nerve section. The vestibulo-ocular reflex (VOR) and postural control were evaluated preoperatively and monitored for up to 4 years postoperatively with use of pseudorandom rotation (combined sinusoidal frequencies from 0.009 to 1.5 Hz) and moving platform posturography. Immediately following surgery all patients showed minimal reductions in the VOR gain constant, but marked reduction in the time constant, and marked increase in slow eye velocity bias. Bias returned to normal values within about 10 days, but time constants never returned to normal values. Results of standard Romberg tests in these patients were normal throughout the preoperative and postoperative periods. However, all patients showed marked postural control abnormalities in tests of the ability to maintain balance in unusual sensory environments in the immediate postoperative period. Seventy-five percent of the patients eventually recovered normal postural control. Postural control returned to near baseline performance with a time course similar to that of the VOR bias. However, postural control also continued to improve after the recovery of VOR bias was complete.

Sign in / Sign up

Export Citation Format

Share Document