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.

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.

Absence of a vergence-mediated vestibulo-ocular reflex gain increase does not preclude adaptation

2021 ◽  
pp. 1-9
Author(s):  
Béla Büki (Family name Büki) ◽  
László T. Tamás (Family name Tamás) ◽  
Christopher J. Todd ◽  
Michael C. Schubert ◽  
Americo A. Migliaccio
Keyword(s):  
Laser Target ◽  
Head Velocity ◽  
Gain Enhancement ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Vor Adaptation ◽  
Reflex Gain ◽  
Head Impulses ◽  
Eye Velocity ◽  
Vestibular Pathways

BACKGROUND: The gain (eye-velocity/head-velocity) of the angular vestibuloocular reflex (aVOR) during head impulses can be increased while viewing near-targets and when exposed to unilateral, incremental retinal image velocity error signals. It is not clear however, whether the tonic or phasic vestibular pathways mediate these gain increases. OBJECTIVE: Determine whether a shared pathway is responsible for gain enhancement between vergence and adaptation of aVOR gain in patients with unilateral vestibular hypofunction (UVH). MATERIAL AND METHODS: 20 patients with UVH were examined for change in aVOR gain during a vergence task and after 15-minutes of ipsilesional incremental VOR adaptation (uIVA) using StableEyes (a device that controls a laser target as a function of head velocity) during horizontal passive head impulses.A 5 % aVOR gain increase was defined as the threshold for significant change. RESULTS: 11/20 patients had >5% vergence-mediated gain increase during ipsi-lesional impulses. For uIVA, 10/20 patients had >5% ipsi-lesional gain increase. There was no correlation between the vergence-mediated gain increase and gain increase after uIVA training. CONCLUSION: Vergence-enhanced and uIVA training gain increases are mediated by separate mechanisms and/or vestibular pathways (tonic/phasic).The ability to increase the aVOR gain during vergence is not prognostic for successful adaptation training.

scholarly journals Normal Performance and Expression of Learning in the Vestibulo-Ocular Reflex (VOR) at High Frequencies

2005 ◽  
Vol 93 (4) ◽  
pp. 2028-2038 ◽  
Author(s):  
Ramnarayan Ramachandran ◽  
Stephen G. Lisberger
Keyword(s):  
Phase Shift ◽  
Harmonic Distortion ◽  
Head Movements ◽  
High Frequencies ◽  
Head Velocity ◽  
Ocular Reflex ◽  
Before And After ◽  
Vestibulo Ocular Reflex ◽  
Eye Velocity ◽  
Normal Performance

The rotatory vestibulo-ocular reflex (VOR) keeps the visual world stable during head movements by causing eye velocity that is equal in amplitude and opposite in direction to angular head velocity. We have studied the performance of the VOR in darkness for sinusoidal angular head oscillation at frequencies ranging from 0.5 to 50 Hz. At frequencies of ≥25 Hz, the harmonic distortion of the stimulus and response were estimated to be <14 and 22%, respectively. We measured the gain of the VOR (eye velocity divided by head velocity) and the phase shift between eye and head velocity before and after adaptation with altered vision. Before adaptation, VOR gains were close to unity for frequencies ≤20 Hz and increased as a function of frequency reaching values of 3 or 4 at 50 Hz. Eye velocity was almost perfectly out of phase with head velocity for frequencies ≤12.5 Hz, and lagged perfect compensation increasingly as a function of frequency. After adaptive modification of the VOR with magnifying or miniaturizing optics, gain showed maximal changes at frequencies <12.5 Hz, smaller changes at higher frequencies, and no change at frequencies larger than 25 Hz. Between 15 and 25 Hz, the phase of eye velocity led the unmodified VOR by as much as 50° when the gain of the VOR had been decreased, and lagged when the gain of the VOR had been increased. We were able to reproduce the main features of our data with a two-pathway model of the VOR, where the two pathways had different relationships between phase shift and frequency.

Modification of compensatory saccades after aVOR gain recovery

2007 ◽  
Vol 16 (6) ◽  
pp. 285-291
Author(s):  
Michael C. Schubert ◽  
Americo A. Migliaccio ◽  
Charles C. Della Santina
Keyword(s):  
Head Rotation ◽  
Rehabilitation Program ◽  
Inverse Dynamic ◽  
Gaze Stabilization ◽  
Ocular Reflex ◽  
Dynamic Relationship ◽  
Vestibulo Ocular Reflex ◽  
Functional Relevance ◽  
Vestibular Neuronitis ◽  
Eye Velocity

The recruitment of extra-vestibular mechanisms to assist a deficient angular vestibulo-ocular reflex (aVOR) during ipsilesional head rotations is well established and includes saccades of reduced latency that occur in the direction of the lesioned aVOR, termed compensatory saccades (CS). Less well known is the functional relevance of these unique saccades. Here we report a 42 y.o. male diagnosed with right unilateral vestibular hypofunction due to vestibular neuronitis who underwent a vestibular rehabilitation program including gaze stabilization exercises. After three weeks, he had a significant improvement in his ability to see clearly during head rotation. Our data show a reduction in the recruitment and magnitude of CS as well as improved peripheral aVOR gain (eye velocity/head velocity) and retinal eye velocity. Our data suggest an inverse, dynamic relationship between the recruitment of CS and the gain of the aVOR.

Recruitment Order of Cat Abducens Motoneurons and Internuclear Neurons

2003 ◽  
Vol 90 (4) ◽  
pp. 2240-2252 ◽  
Author(s):  
Ángel M. Pastor ◽  
David González-Forero
Keyword(s):  
Rectus Muscle ◽  
Neuronal Firing ◽  
Eye Position ◽  
High Dose ◽  
Recruitment Threshold ◽  
Ocular Reflex ◽  
Lateral Rectus Muscle ◽  
Vestibulo Ocular Reflex ◽  
Recruitment Order ◽  
Eye Velocity

Abducens neurons undergo a dose-dependent synaptic blockade (either disinhibition or complete blockade) when tetanus neurotoxin (TeNT) is injected into the lateral rectus muscle at either a low (0.5) or a high dose (5 ng/kg). We studied the firing pattern and recruitment order in abducens neurons both in control and after TeNT injection. The eye position threshold for recruitment of control abducens neurons was exponentially related to the eye position and velocity sensitivities. We also found a constancy of recruitment threshold for different eye movement modalities (spontaneous, optokinetic, and vestibular). Exponential relationships were found, as well, for eye velocity sensitivity during saccades and for position and velocity sensitivities during the vestibulo-ocular reflex. Likewise, inverse relationships were found between recruitment threshold or position sensitivity with the antidromic latency in control abducens neurons. These relationships, however, did not apply following TeNT treatment. Neuronal firing after TeNT appeared either disinhibited (low dose) or depressed (high dose), but the relationships between neuronal sensitivities and recruitment still applied. However, the pattern of recruitment shifted toward the treated side as more inputs were blocked by the low- and high-dose treatments, respectively. Nonetheless, although the recruitment-to-sensitivity relationships persisted under the TeNT synaptic blockade, we conclude that synaptic inputs are determinant for establishing the recruitment threshold and recruitment spacing of abducens motoneurons and internuclear neurons.

The three-dimensional vestibulo-ocular reflex evoked by high-acceleration rotations in the squirrel monkey

2004 ◽  
Vol 159 (4) ◽  
pp. 433-446 ◽  
Author(s):  
Americo A. Migliaccio ◽  
Michael C. Schubert ◽  
Patpong Jiradejvong ◽  
David M. Lasker ◽  
Richard A. Clendaniel ◽  
...  
Keyword(s):  
Squirrel Monkey ◽  
Three Dimensional ◽  
Ocular Reflex ◽  
High Acceleration ◽  
Vestibulo Ocular Reflex

scholarly journals Vestibulo-Ocular Reflex to Transient Surge Translation: Complex Geometric Response Ablated by Normal Aging

2006 ◽  
Vol 95 (4) ◽  
pp. 2042-2054 ◽  
Author(s):  
Jun-ru Tian ◽  
Eriko Mokuno ◽  
Joseph L. Demer
Keyword(s):  
Response Rate ◽  
Normal Aging ◽  
Whole Body ◽  
Head Acceleration ◽  
Target Eccentricity ◽  
Ocular Reflex ◽  
Younger Age ◽  
Vestibulo Ocular Reflex ◽  
Older Subjects ◽  
Target Visibility

The linear vestibulo-ocular reflex (LVOR) to surge (fore-aft) translation has complex kinematics varying with target eccentricity and distance. To determine normal responses and aging changes, 9 younger [age, 28 ± 2 (SE) yr] and 11 older subjects (age, 69 ± 2 yr) underwent 0.5 g whole body surge transients while wearing binocular scleral search coils. Linear chair position and head acceleration were measured with a potentiometer and accelerometer. Subjects viewed centered and 10° horizontally and vertically eccentric targets 50, 25, or 15 cm distant before unpredictable onset of randomly directed surge in darkness (LVOR) and light (V-LVOR). Response directions were kinematically appropriate to eccentricity in all subjects, but there were significantly more measurable LVOR and V-LVOR responses (63–79%) in younger than older subjects (38–44%, P < 0.01). Minimal LVOR latency averaged 48 ± 4 ms for younger and significantly longer at 70 ± 6 ms for older subjects. In the interval 200–300 ms after surge onset, horizontal LVOR gain (relative to ideal velocity) of younger subjects averaged over all target distances was 0.55 ± 0.04 and was significantly reduced in older subjects to 0.33 ± 0.04. Horizontal V-LVOR gain was 0.58 ± 0.04 in younger and significantly lower at 0.35 ± 0.06 in older subjects. Vertical gains did not differ significantly between groups. Target visibility had no effect in either group during the initial 200 ms. The LVOR and V-LVOR were augmented by saccades in younger more than older subjects. Aging thus decreases LVOR velocity gain, response rate, and saccade augmentation, but prolongs latency.

Primate Translational Vestibuloocular Reflexes. II. Version and Vergence Responses to Fore-Aft Motion

2000 ◽  
Vol 83 (3) ◽  
pp. 1648-1661 ◽  
Author(s):  
M. Quinn McHenry ◽  
Dora E. Angelaki
Keyword(s):  
Eye Movements ◽  
Rhesus Monkeys ◽  
Viewing Distance ◽  
Functional Dependencies ◽  
Ideal Behavior ◽  
Pass Filter ◽  
Disjunctive Eye Movements ◽  
Eye Velocity ◽  
High Pass ◽  
Straight Ahead

To maintain binocular fixation on near targets during fore-aft translational disturbances, largely disjunctive eye movements are elicited the amplitude and direction of which should be tuned to the horizontal and vertical eccentricities of the target. The eye movements generated during this task have been investigated here as trained rhesus monkeys fixated isovergence targets at different horizontal and vertical eccentricities during 10 Hz fore-aft oscillations. The elicited eye movements complied with the geometric requirements for binocular fixation, although not ideally. First, the corresponding vergence angle for which the movement of each eye would be compensatory was consistently less than that dictated by the actual fixation parameters. Second, the eye position with zero sensitivity to translation was not straight ahead, as geometrically required, but rather exhibited a systematic dependence on viewing distance and vergence angle. Third, responses were asymmetric, with gains being larger for abducting and downward compared with adducting and upward gaze directions, respectively. As frequency was varied between 4 and 12 Hz, responses exhibited high-pass filter properties with significant differences between abduction and adduction responses. As a result of these differences, vergence sensitivity increased as a function of frequency with a steeper slope than that of version. Despite largely undercompensatory version responses, vergence sensitivity was closer to ideal. Moreover, the observed dependence of vergence sensitivity on vergence angle, which was varied between 2.5 and 10 MA, was largely linear rather than quadratic (as geometrically predicted). We conclude that the spatial tuning of eye velocity sensitivity as a function of gaze and viewing distance follows the general geometric dependencies required for the maintenance of foveal visual acuity. However, systematic deviations from ideal behavior exist that might reflect asymmetric processing of abduction/adduction responses perhaps because of different functional dependencies of version and vergence eye movement components during translation.

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