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Kojima Y, Ling L, Phillips JO. Compensatory saccade in the vestibular impaired monkey. Front Neurol 2023; 14:1198274. [PMID: 37780695 PMCID: PMC10538121 DOI: 10.3389/fneur.2023.1198274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 08/11/2023] [Indexed: 10/03/2023] Open
Abstract
Introduction Loss of the vestibulo-ocular reflex (VOR) affects visual acuity during head movements. Patients with unilateral and bilateral vestibular deficits often use saccadic eye movements to compensate for an inadequate VOR. Two types of compensatory saccades have been distinguished, covert saccades and overt saccades. Covert saccades occur during head rotation, whereas overt saccades occur after the head has stopped moving. The generation of covert saccades is part of a central vestibular compensation process that improves visual acuity and suppresses oscillopsia. Understanding the covert saccade mechanism may facilitate vestibular rehabilitation strategies that can improve the patient's quality of life. To understand the brain mechanisms underlying covert saccades at the neural level, studies in an animal model are necessary. In this study, we employed non-human primates whose vestibular end organs are injured. Methods We examined eye movement during the head-impulse test, which is a clinical test to evaluate the vestibulo-ocular reflex. During this test, the monkeys are required to fixate on a target and the head is rapidly and unexpectedly rotated to stimulate the horizontal semi-circular canals. Results Similar to human subjects, monkeys made compensatory saccades. We compared these saccades with catch-up saccades following a moving target that simulates the visual conditions during the head impulse test. The shortest latency of the catch-up saccades was 250 ms, which indicates that it requires at least 250 ms to induce saccades by a visual signal. The latency of some compensatory saccades is shorter than 250 ms during the head impulse test, suggesting that such short latency compensatory saccades were not induced visually. The peak velocity of the short latency saccades was significantly lower than that of longer latency saccades. The peak velocity of these longer latency saccades was closer to that of visually guided saccades induced by a stepping target. Conclusion These results are consistent with studies in human patients. Thus, this study demonstrates, for the first time, compensatory covert saccades in vestibular impaired monkeys.
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Affiliation(s)
- Yoshiko Kojima
- Department of Otolaryngology-HNS, University of Washington, Seattle, WA, United States
- National Primate Research Center, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, WA, United States
| | - Leo Ling
- National Primate Research Center, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, WA, United States
| | - James O. Phillips
- Department of Otolaryngology-HNS, University of Washington, Seattle, WA, United States
- National Primate Research Center, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, WA, United States
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Kerkeni H, Zee DS, Korda A, Morrison M, Mantokoudis G, Ramat S. Corrective saccades in acute vestibular neuritis: studying the role of prediction with automated passively induced head impulses. J Neurophysiol 2023; 129:445-454. [PMID: 36651642 DOI: 10.1152/jn.00382.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
When the demands for visual stabilization during head rotations overwhelm the ability of the vestibuloocular reflex (VOR) to produce compensatory eye movements, the brain produces corrective saccades that bring gaze toward the fixation target, even without visual cues (covert saccades). What triggers covert saccades and what might be the role of prediction in their generation are unknown. We studied 14 subjects with acute vestibular neuritis. To minimize variability of the stimulus, head impulses were imposed with a motorized torque generator with the subject on a bite bar. Predictable and unpredictable (timing, amplitude, direction) stimuli were compared. Distributions of covert corrective saccade latencies were analyzed with a "LATER" (linear approach to threshold with ergodic rate) approach. On the affected side, VOR gain was higher (0.47 ± 0.28 vs. 0.39 ± 0.22, P ≪ 0.001) with predictable than unpredictable head impulses, and gaze error at the end of the head movement was less (5.4 ± 3.3° vs. 6.9 ± 3.3°, P ≪ 0.001). Analyzing trials with covert saccades, gaze error at saccade end was significantly less with predictable than unpredictable head impulses (4.2 ± 2.8° vs. 5.5 ± 3.2°, P ≪ 0.001). Furthermore, covert corrective saccades occurred earlier with predictable than unpredictable head impulses (140 ± 37 vs. 153 ± 37 ms, P ≪ 0.001). Using a LATER analysis with reciprobit plots, we were able to divide covert corrective saccades into two classes, early and late, with a break point in the range of 88-98 ms. We hypothesized two rise-to-threshold decision mechanisms for triggering early and late covert corrective saccades, with the first being most engaged when stimuli are predictable.NEW & NOTEWORTHY We successfully used a LATER (linear approach to threshold with ergodic rate) analysis of the latencies of corrective saccades in patients with acute vestibular neuritis. We found two types of covert saccades: early (<90 ms) and late (>90 ms) covert saccades. Predictability led to an increase in VOR gain and a decrease in saccade latency.
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Affiliation(s)
- Hassen Kerkeni
- Department of Neurology, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - David S Zee
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Athanasia Korda
- Department of Otorhinolaryngology, Head and Neck Surgery, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Miranda Morrison
- Department of Otorhinolaryngology, Head and Neck Surgery, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Georgios Mantokoudis
- Department of Otorhinolaryngology, Head and Neck Surgery, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Stefano Ramat
- Laboratory of Bioengineering, Department of Electrical, Computer and Biomedical Engineering, University of Pavia, Pavia, Italy
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Iwasaki S, Kamogashira T, Fujimoto C, Kabaya K, Kinoshita M, Yamasoba T. The Role of Neck Input in Producing Corrective Saccades in the Head Impulse Test. Front Neurol 2022; 13:881411. [PMID: 35655613 PMCID: PMC9152213 DOI: 10.3389/fneur.2022.881411] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 05/03/2022] [Indexed: 12/21/2022] Open
Abstract
Background The head impulse test is a valuable clinical test that can help identify peripheral vestibular dysfunction by observing corrective saccades that return the eyes to the target of interest. Corrective saccades have been classified as covert if the onset occurs before the end of the head impulse and as overt if they occur afterwards. However, the mechanism that trigger these saccades remain unclear. Objective The objective of this study was to examine the role of neck input in generating overt as well as covert saccades. Methods Sixteen patients (9 males and 7 females: age 35-80 years, average 62.7 years old) who showed corrective saccades during the head impulse test were included. Twelve patients had unilateral vestibular dysfunction, and 4 patients had bilateral vestibular dysfunction. Patients underwent both the head impulse test (HIT) and the body impulse test (BIT) in a randomized order. While the head is rotated horizontally in HIT, the body is rotated horizontally in BIT. During BIT, the neck is fixed by a cervical collar (neck lock extrication collar) to reduce somatosensory input from the neck. The head movements and eye movements were recorded and analyzed by the video HIT recording system. Results In all 16 patients, corrective saccades were observed in HIT as well as in BIT. While there were no significant differences in peak head velocities between HIT and BIT (p = 0.33, paired t-test), the VOR gain in BIT was significantly smaller than that in HIT (p = 0.011, paired t-test). The number of overt saccades per trial in BIT was significantly decreased compared to that in HIT (p < 0.001, paired t-test) whereas there were no significant differences in the number of covert saccades between the two tests. The proportion of overt saccades among all corrective saccades in BIT was significantly lower than the proportion in HIT (p < 0.001, paired t-test). Conclusions Somatosensory input from the neck contributes to the generation of overt saccades and reinforces the vestibulo-ocular reflex complementing the retinal slip during high frequency head movements.
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Affiliation(s)
- Shinichi Iwasaki
- Department of Otolaryngology & Head and Neck Surgery, Nagoya City University Graduate School of Medicine, Nagoya, Japan
| | - Teru Kamogashira
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Chisato Fujimoto
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Kayoko Kabaya
- Department of Otolaryngology & Head and Neck Surgery, Nagoya City University Graduate School of Medicine, Nagoya, Japan
| | - Makoto Kinoshita
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Tatsuya Yamasoba
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
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Koç A, Akkılıç EC. Evaluation of video head impulse test during vertiginous attack in vestibular migraine. ACTA OTORHINOLARYNGOLOGICA ITALICA 2022; 42:281-286. [PMID: 35880368 PMCID: PMC9330756 DOI: 10.14639/0392-100x-n1951] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 03/20/2022] [Indexed: 11/24/2022]
Abstract
Objective The aim of this study is to evaluate vestibular functions with video head impulse test (VHIT) and to understand the value of VHIT in differential diagnosis in patients with vestibular migraine (VM) during dizziness attack. Materials and methods Two groups were enrolled in this study. The first consisted of 84 vestibular migraine patients, and second group of 74 healthy subjects. VHIT was applied to patients with VM during vertigo attack and the results were compared with the VHIT values applied to subjects in the control group. Results The mean vestibulo-ocular reflex (VOR) in all semicircular canals in the VM group was lower than healthy individuals, but the results were not statistically significant. Refixation saccades were found in 52.3% of VM patients and in 10.2% of healthy individuals. Conclusions When patients with VM were evaluated with VHIT during vertiginous attack, VOR gain values were not different from healthy individuals, but the number of catch-up saccades were higher in VM patients, which indicates peripheral vestibular involvement. For differential diagnosis in patients with VM, vestibular tests should be performed during the vertigo attack. When evaluating VHIT results, the presence of refixation saccades should also be evaluated.
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Video Head Impulse Test in Darkness, Without Visual Fixation: A Study on Healthy Subjects. Ear Hear 2021; 43:1273-1281. [PMID: 34935649 DOI: 10.1097/aud.0000000000001180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE The head impulse test (HIT) is triggered by the vestibulo-ocular reflex (VOR), complemented by the optokinetic and pursuit systems. This study aimed to evaluate the possibility of individualizing the VOR contribution to the HIT. DESIGN Thirty-six healthy individuals (19 males, 17 females; age 21-64 years, mean 39 years) underwent horizontal video HIT (vHIT). This was first conducted in darkness, without visual fixation, and then visually tracked. RESULTS Seventy percent of the impulses delivered ocular responses opposite to the direction of the head, matching its velocity to a point where quick anticompensatory eye movements (SQEM) stopped the response (SQEM mean latency 58.21 ms, interquartile range 50-67 ms). Of these, 75% recaptured the head velocity after culmination. Thirty percent of the responses completed a bell-shaped curve. The completed bell-shaped curve gains and instantaneous gains (at 40, 60, and 80 ms) before SQEM were equivalent for both paradigms. Females completed more bell-shaped traces (42%) than males (15%); p = 0.01. The SQEM latency was longer (62.81 versus 55.71 ms, p < 0.01), and the time to recapture the bell-shaped curve was shorter (77.51 versus 92.52 ms, p < 0.01) in females than in males. The gains were comparable between sexes in both paradigms. CONCLUSIONS The VOR effect can be localized in the first 70 ms of the vHIT response. In addition, other influences may take place in estimating the vHIT responses. The study of these influences might provide useful information that can be applied to patient management.
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Sjögren J, Karlberg M, Hickson C, Magnusson M, Fransson PA, Tjernström F. Short-Latency Covert Saccades - The Explanation for Good Dynamic Visual Performance After Unilateral Vestibular Loss? Front Neurol 2021; 12:695064. [PMID: 34531814 PMCID: PMC8439257 DOI: 10.3389/fneur.2021.695064] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 07/26/2021] [Indexed: 11/13/2022] Open
Abstract
Background: Functional head impulse test (fHIT) tests the ability of the vestibulo-ocular reflex (VOR) to allow visual perception during head movements. Our previous study showed that active head movements to the side with a vestibular lesion generated a dynamic visual performance that were as good as during movements to the intact side. Objective: To examine the differences in eye position during the head impulse test when performed with active and passive head movements, in order to better understand the role of the different saccade properties in improving visual performance. Method: We recruited 8 subjects with complete unilateral vestibular loss (4 men and 4 women, mean age 47 years) and tested them with video Head Impulse Test (vHIT) and Functional Head Impulse Test (fHIT) during passive and active movements while looking at a target. We assessed the mean absolute position error of the eye during different time frames of the head movement, the peak latency and the peak velocity of the first saccade, as well as the visual performance during the head movement. Results: Active head impulses to the lesioned side generated dynamic visual performances that were as good as when testing the intact side. Active head impulses resulted in smaller position errors during the visual perception task (p = 0.006) compared to passive head-impulses and the position error during the visual perception time frame correlated with shorter latencies of the first saccade (p < 0.001). Conclusion: Actively generated head impulses toward the side with a complete vestibular loss resulted in a position error within or close to the margin necessary to obtain visual perception for a brief period of time in patients with chronic unilateral vestibular loss. This seems to be attributed to the appearance of short-latency covert saccades, which position the eyes in a more favorable position during head movements.
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Affiliation(s)
- Julia Sjögren
- Department of Clinical Sciences, Otorhinolaryngology Head and Neck Surgery, Skåne University Hospital, Lund University, Lund, Sweden
| | - Mikael Karlberg
- Department of Clinical Sciences, Otorhinolaryngology Head and Neck Surgery, Skåne University Hospital, Lund University, Lund, Sweden
| | - Craig Hickson
- Department of Otorhinolaryngology Head and Neck Surgery, William Harvey Hospital, East Kent Hospitals University Foundation Trust, Ashford, United Kingdom
| | - Måns Magnusson
- Department of Clinical Sciences, Otorhinolaryngology Head and Neck Surgery, Skåne University Hospital, Lund University, Lund, Sweden
| | - Per-Anders Fransson
- Department of Clinical Sciences, Otorhinolaryngology Head and Neck Surgery, Skåne University Hospital, Lund University, Lund, Sweden
| | - Fredrik Tjernström
- Department of Clinical Sciences, Otorhinolaryngology Head and Neck Surgery, Skåne University Hospital, Lund University, Lund, Sweden
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Yamakawa M, Kabaya K, Fukushima A, Ito S, Iwasaki S. Acute vestibulopathy with simultaneous bilateral involvement of the vestibulo-ocular reflex limited to the low-frequency range. Auris Nasus Larynx 2021; 49:898-902. [PMID: 33810924 DOI: 10.1016/j.anl.2021.03.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 02/12/2021] [Accepted: 03/16/2021] [Indexed: 11/20/2022]
Abstract
We report a novel type of idiopathic bilateral vestibulopathy with acute simultaneous involvement of the vestibulo-ocular reflex limited to the low-frequency range. A 64-year-old female presented with dizziness, oscillopsia, and difficulty walking. She did not experience rotatory vertigo and did not show any nystagmus. Vestibular function tests showed absent caloric responses in both ears, while vestibulo-ocular reflex (VOR) gains in the video head impulse test (vHIT) were preserved in all six semicircular canals. Cervical and ocular vestibular evoked myogenic potentials in response to air-conducted sound were absent on both sides. Since the caloric test and vHIT measures low-frequency and high-frequency VOR, respectively, we diagnosed the patient as having a bilateral VOR deficit limited to the low-frequency range. During a 1-year follow-up with vestibular rehabilitation, the subjective symptom of dizziness gradually recovered while recovery of vestibular function was minimal.
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Affiliation(s)
- Maiko Yamakawa
- Department of Otolaryngology-Head and Neck Surgery, Nagoya City University Graduate School of Medical Science, 1 Kawaumi Mizuho-Ku, Nagoya, Aichi, 467-8601, Japan
| | - Kayoko Kabaya
- Department of Otolaryngology-Head and Neck Surgery, Nagoya City University Graduate School of Medical Science, 1 Kawaumi Mizuho-Ku, Nagoya, Aichi, 467-8601, Japan.
| | - Akina Fukushima
- Department of Otolaryngology-Head and Neck Surgery, Nagoya City University Graduate School of Medical Science, 1 Kawaumi Mizuho-Ku, Nagoya, Aichi, 467-8601, Japan; Department of Otolaryngology-Head and Neck Surgery, Toyohashi Municipal Hospital, 50 Aza Hachiken Nishi, Aotake-Cho, Toyohashi, Aichi, 441-8570, Japan
| | - Shinobu Ito
- Department of Otolaryngology-Head and Neck Surgery, Toyohashi Municipal Hospital, 50 Aza Hachiken Nishi, Aotake-Cho, Toyohashi, Aichi, 441-8570, Japan
| | - Shinichi Iwasaki
- Department of Otolaryngology-Head and Neck Surgery, Nagoya City University Graduate School of Medical Science, 1 Kawaumi Mizuho-Ku, Nagoya, Aichi, 467-8601, Japan
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Pogson JM, Taylor RL, McGarvie LA, Bradshaw AP, D’Souza M, Flanagan S, Kong J, Halmagyi GM, Welgampola MS. Head impulse compensatory saccades: Visual dependence is most evident in bilateral vestibular loss. PLoS One 2020; 15:e0227406. [PMID: 31940394 PMCID: PMC6961882 DOI: 10.1371/journal.pone.0227406] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 12/18/2019] [Indexed: 11/19/2022] Open
Abstract
The normal vestibulo-ocular reflex (VOR) generates almost perfectly compensatory smooth eye movements during a 'head-impulse' rotation. An imperfect VOR gain provokes additional compensatory saccades to re-acquire an earth-fixed target. In the present study, we investigated vestibular and visual contributions on saccade production. Eye position and velocity during horizontal and vertical canal-plane head-impulses were recorded in the light and dark from 16 controls, 22 subjects after complete surgical unilateral vestibular deafferentation (UVD), eight subjects with idiopathic bilateral vestibular loss (BVL), and one subject after complete bilateral vestibular deafferentation (BVD). When impulses were delivered in the horizontal-canal plane, in complete darkness compared with light, first saccade frequency mean(SEM) reduced from 96.6(1.3)-62.3(8.9) % in BVL but only 98.3(0.6)-92.0(2.3) % in UVD; saccade amplitudes reduced from 7.0(0.5)-3.6(0.4) ° in BVL but were unchanged 6.2(0.3)-5.5(0.6) ° in UVD. In the dark, saccade latencies were prolonged in lesioned ears, from 168(8.4)-240(24.5) ms in BVL and 177(5.2)-196(5.7) ms in UVD; saccades became less clustered. In BVD, saccades were not completely abolished in the dark, but their amplitudes decreased from 7.3-3.0 ° and latencies became more variable. For unlesioned ears (controls and unlesioned ears of UVD), saccade frequency also reduced in the dark, but their small amplitudes slightly increased, while latency and clustering remained unchanged. First and second saccade frequencies were 75.3(4.5) % and 20.3(4.1) %; without visual fixation they dropped to 32.2(5.0) % and 3.8(1.2) %. The VOR gain was affected by vision only in unlesioned ears of UVD; gains for the horizontal-plane rose slightly, and the vertical-planes reduced slightly. All head-impulse compensatory saccades have a visual contribution, the magnitude of which depends on the symmetry of vestibular-function and saccade latency: BVL is more profoundly affected by vision than UVD, and second saccades more than first saccades. Saccades after UVD are probably triggered by contralateral vestibular function.
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Affiliation(s)
- Jacob M. Pogson
- Royal Prince Alfred Hospital, Institute of Clinical Neuroscience, Camperdown, New South Wales, Australia
- Faculty of Health and Medicine, Sydney Medical School, The University of Sydney, Camperdown, New South Wales, Australia
| | - Rachael L. Taylor
- Royal Prince Alfred Hospital, Institute of Clinical Neuroscience, Camperdown, New South Wales, Australia
- Faculty of Health and Medicine, Sydney Medical School, The University of Sydney, Camperdown, New South Wales, Australia
| | - Leigh A. McGarvie
- Royal Prince Alfred Hospital, Institute of Clinical Neuroscience, Camperdown, New South Wales, Australia
- Department of Psychology, Faculty of Science, The University of Sydney, Camperdown, New South Wales, Australia
| | - Andrew P. Bradshaw
- Royal Prince Alfred Hospital, Institute of Clinical Neuroscience, Camperdown, New South Wales, Australia
| | - Mario D’Souza
- Department of Clinical Research, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
| | - Sean Flanagan
- Otolaryngology, Head and Neck and Skull Base Surgery, St Vincent’s Hospital, Darlinghurst, New South Wales, Australia
- Faculty of Medicine, University of NSW, Kensington, New South Wales, Australia
| | - Jonathan Kong
- Faculty of Health and Medicine, Sydney Medical School, The University of Sydney, Camperdown, New South Wales, Australia
- Department of Neurosurgery, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
- Department of Otolaryngology, Head & Neck Surgery, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
| | - G. Michael Halmagyi
- Royal Prince Alfred Hospital, Institute of Clinical Neuroscience, Camperdown, New South Wales, Australia
- Faculty of Health and Medicine, Sydney Medical School, The University of Sydney, Camperdown, New South Wales, Australia
| | - Miriam S. Welgampola
- Royal Prince Alfred Hospital, Institute of Clinical Neuroscience, Camperdown, New South Wales, Australia
- Faculty of Health and Medicine, Sydney Medical School, The University of Sydney, Camperdown, New South Wales, Australia
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Pogson JM, Taylor RL, Bradshaw AP, McGarvie L, D’Souza M, Halmagyi GM, Welgampola MS. The human vestibulo-ocular reflex and saccades: normal subjects and the effect of age. J Neurophysiol 2019; 122:336-349. [DOI: 10.1152/jn.00847.2018] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Here we characterize in 80 normal subjects (16–84 yr (means ± SD, 47 ± 19 yr) the vestibulo-ocular reflex (VOR) and saccades in response to three-dimensional head impulses with a monocular video head impulse test (vHIT) of the right eye. Impulses toward the right lateral, right anterior, and left posterior canals (means: 0.98, 0.91, 0.79) had slightly higher mean gains compared with their counterparts (0.95, 0.86, 0.76). In the older age group (>60 yr), gains of the left posterior canal dropped 0.09 and left anterior canals rose 0.09 resulting in symmetry. All canal gains reduced with increasing head velocity (0.02–0.13 per 100°/s). Comparison of lateral canal gains calculated using five published algorithms yielded lower values (~0.80) when a narrow detection window was used. Low-amplitude refixation saccades (amplitude: 1.11 ± 0.98°, peak velocity: 63.9 ± 34.0°/s at 262.0 ± 93.9 ms) were observed among all age groups (frequency: 40.2 ± 23.4%), increasing in amplitude, peak velocity, and frequency in older subjects. Impulses toward anterior canals showed the least frequent saccades and lateral and posterior canals were similar, but lateral canal impulses showed the smallest saccades and the posterior canal showed the largest saccades. Saccade peak-velocity approximate amplitude “main sequence” slope was steeper for the horizontal canals compared with the vertical planes (60 vs. <40°/s per 1°). In summary, we found small but significant asymmetries in monocular vHIT gain that changed with age. Healthy subjects commonly have minuscule refixation saccades that are moderately to strongly correlated with vHIT gain. NEW & NOTEWORTHY Gaze fixation is normally stabilized during rapid “head-impulse” movements by the bisynaptic vestibulo-ocular reflex (VOR), but earlier studies of normal subjects also report small amplitude saccades. We found that with increased age of the subject the vertical VOR became more variable, while in all semicircular canal directions the saccade frequency, amplitude, and peak velocity increased. We also found that the VOR gain algorithm significantly influences values.
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Affiliation(s)
- Jacob M. Pogson
- Sydney Medical School, The University of Sydney, Camperdown, New South Wales, Australia
- Institute of Clinical Neuroscience, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
| | - Rachael L. Taylor
- Institute of Clinical Neuroscience, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Andrew P. Bradshaw
- Institute of Clinical Neuroscience, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
| | - Leigh McGarvie
- Psychology Department, The University of Sydney, Camperdown, New South Wales, Australia
- Institute of Clinical Neuroscience, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
| | - Mario D’Souza
- Sydney Medical School, The University of Sydney, Camperdown, New South Wales, Australia
- Clinical Research Centre, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
| | - G. Michael Halmagyi
- Sydney Medical School, The University of Sydney, Camperdown, New South Wales, Australia
- Institute of Clinical Neuroscience, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
| | - Miriam S. Welgampola
- Sydney Medical School, The University of Sydney, Camperdown, New South Wales, Australia
- Institute of Clinical Neuroscience, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
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Jay DR, Cane D, Howe S. Age Is a Greater Influence on Small Saccades Than Target Size in Normal Subjects on the Horizontal Video Head Impulse Test. Front Neurol 2019; 10:328. [PMID: 31040813 PMCID: PMC6476940 DOI: 10.3389/fneur.2019.00328] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 03/18/2019] [Indexed: 12/01/2022] Open
Abstract
Objective: This study sought to investigate whether the size of the target used in the horizontal vHIT has an effect on the saccade profile of healthy subjects, and to expand upon previous work linking age to the existence of small vHIT saccades. Methods: Forty eight participants were recruited between 18 and 77 years of age, with no history of vestibular, oculomotor or neurological conditions and a visual acuity of at least 0.3 LogMAR. Participants underwent four consecutive horizontal vHIT trials using the standard target size and three smaller targets. VOR gain and metrics for saccadic incidence, peak eye velocity and latency were then extracted from results. Results: Target size was a statistically significant influence on saccade metrics. As target size increased, saccadic incidence decreased while peak eye velocity and latency increased. However, a potential order effect was also discovered, and once this was corrected for the remaining effect of target size was small and is likely clinically insignificant. The effect of age was much stronger than target size; increasing age was strongly positively correlated with saccadic incidence and showed a medium size correlation with peak velocity, though not with saccadic latency. Conclusion: While this study suggests that target size may have a statistically significant impact on the vHIT saccade profile of normal subjects, age has a greater influence on the incidence and size of small vHIT saccades.
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Affiliation(s)
- David R Jay
- Manchester Head and Neck Centre, Manchester University NHS Foundation Trust, Manchester, United Kingdom
| | - Debbie Cane
- Manchester Centre for Audiology and Deafness, The University of Manchester, Manchester, United Kingdom
| | - Simon Howe
- Manchester Centre for Audiology and Deafness, The University of Manchester, Manchester, United Kingdom.,Department of Audiology, The James Cook University Hospital, South Tees Hospitals NHS Foundation Trust, Middlesbrough, United Kingdom
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Van Nechel C, Bostan A, Duquesne U, Hautefort C, Toupet M. Visual Input Is the Main Trigger and Parametric Determinant for Catch-Up Saccades During Video Head Impulse Test in Bilateral Vestibular Loss. Front Neurol 2019; 9:1138. [PMID: 30662427 PMCID: PMC6328459 DOI: 10.3389/fneur.2018.01138] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 12/10/2018] [Indexed: 11/13/2022] Open
Abstract
Patients with vestibular deficit use slow eye movements or catch-up saccades (CUS) to compensate for impaired vestibulo-ocular reflex (VOR). The purpose of CUS is to bring the eyes back to the visual target. Covert CUS occur during high-velocity head rotation and overt CUS are generated after head rotation has stopped. Dynamic visual acuity is improved with an increased rate and gain of CUS. Nevertheless, the trigger and the parametric determinants of CUS are still under debate. To clarify the underlying mechanism, especially the visual contribution, we analyzed the number, amplitude and latencies of the CUS in relation with the extent of VOR deficiency. The head and eye movements were recorded in 17 patients with bilateral vestibular loss (BVL) and in 33 subjects with normal VOR gain using the Video Head Impulse Test (vHIT) in two conditions: with visible target and in darkness with an imaginary target. Our study shows that in darkness without visible target the number of CUS is significantly reduced and the relationship between the amplitude of CUS and gaze position error is lost. Results showed that there is a correlation between the number of CUS and the drop in VOR gain. CUS occurring during the head movement and when the head remained still were not always sufficiently accurate. Up to four consecutive CUS could be required to bring eyes back to the visible target. A positive correlation was found between the amplitude of overt saccades with visible target and the gaze position error, namely the remaining eye movement to reach the target. These results suggest that the visual inputs are the main trigger and parametric determinant of the CUS or at least the presence of a visual target is necessary in most cases for a CUS to occur.
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Affiliation(s)
- Christian Van Nechel
- Unité Troubles de l'Equilibre et Vertiges, Centre Hospitalier Universitaire Brugmann, Brussels, Belgium.,Unité de Neuro-Ophtalmologie, Hôpital Erasme, Brussels, Belgium.,Institut de Recherche Oto-Neurologique (IRON), Paris, France.,Clinique des Vertiges, Brussels, Belgium
| | - Alionka Bostan
- Unité Troubles de l'Equilibre et Vertiges, Centre Hospitalier Universitaire Brugmann, Brussels, Belgium.,Unité de Neuro-Ophtalmologie, Hôpital Erasme, Brussels, Belgium
| | - Ulla Duquesne
- Institut de Recherche Oto-Neurologique (IRON), Paris, France.,Clinique des Vertiges, Brussels, Belgium
| | - Charlotte Hautefort
- Institut de Recherche Oto-Neurologique (IRON), Paris, France.,Service ORL, APHP CHU Lariboisière, Paris, France
| | - Michel Toupet
- Institut de Recherche Oto-Neurologique (IRON), Paris, France.,Centre d'Explorations Fonctionnelles Otoneurologiques, Paris, France
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12
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Sjögren J, Fransson PA, Karlberg M, Magnusson M, Tjernström F. Functional Head Impulse Testing Might Be Useful for Assessing Vestibular Compensation After Unilateral Vestibular Loss. Front Neurol 2018; 9:979. [PMID: 30510538 PMCID: PMC6252383 DOI: 10.3389/fneur.2018.00979] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 10/30/2018] [Indexed: 11/13/2022] Open
Abstract
Background: Loss of the vestibulo-ocular reflex (VOR) affects visual acuity during head movements. Previous studies have shown that compensatory eye-saccades improve visual acuity and that the timing of the saccade is important. Most of the tests involved in testing VOR are made with passive head movement, that do not necessarily reflect the activities of daily living and thus not being proportionate to symptoms and distresses of the patients. Objective: To examine differences between active (self-generated) or passive (imposed by the examiner) head rotations while trying to maintain visual focus on a target. Method: Nine subjects with unilateral total vestibular loss were recruited (4 men and 5 women, mean age 47) and tested with video Head Impulse Test (vHIT) and Head Impulse Testing Device-Functional Test (HITD-FT) during passive and active movements while looking at a target. VOR gain, latencies of covert saccades, frequency of covert saccades and visual acuity were measured and analyzed. Results: Active head-impulses toward the lesioned side resulted in better visual acuity (p = 0.002) compared to conventional passive head-impulses and generated eye-saccades with significantly shorter latencies (p = 0.004). Active movements to the lesioned side generated dynamic visual acuities that were as good as when testing the intact side. Conclusion: Actively generated head impulses resulted in normal dynamic visual acuity, even when performed toward the side of total vestibular loss. This might be attributed to the appearance of short-latency covert saccades. The results show a strong relationship between self-generated movements, latencies of covert saccades and outcome in HITD-FT, i.e., a better dynamic visual function with less retinal slip which is the main function of the VOR. The method of active HITD-FT might be valuable in assessing vestibular compensation and monitoring ongoing vestibular rehabilitation.
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Affiliation(s)
- Julia Sjögren
- Department of Clinical Sciences Lund, Faculty of Medicine, Skåne University Hospital, Lund University, Lund, Sweden
| | - Per-Anders Fransson
- Department of Clinical Sciences Lund, Faculty of Medicine, Skåne University Hospital, Lund University, Lund, Sweden
| | - Mikael Karlberg
- Department of Clinical Sciences Lund, Faculty of Medicine, Skåne University Hospital, Lund University, Lund, Sweden
| | - Måns Magnusson
- Department of Clinical Sciences Lund, Faculty of Medicine, Skåne University Hospital, Lund University, Lund, Sweden
| | - Fredrik Tjernström
- Department of Clinical Sciences Lund, Faculty of Medicine, Skåne University Hospital, Lund University, Lund, Sweden
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13
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Colagiorgio P, Versino M, Colnaghi S, Quaglieri S, Manfrin M, Zamaro E, Mantokoudis G, Zee DS, Ramat S. New insights into vestibular-saccade interaction based on covert corrective saccades in patients with unilateral vestibular deficits. J Neurophysiol 2017; 117:2324-2338. [PMID: 28404827 DOI: 10.1152/jn.00864.2016] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 04/10/2017] [Accepted: 04/10/2017] [Indexed: 11/22/2022] Open
Abstract
In response to passive high-acceleration head impulses, patients with low vestibulo-ocular reflex (VOR) gains often produce covert (executed while the head is still moving) corrective saccades in the direction of deficient slow phases. Here we examined 23 patients using passive, and 9 also active, head impulses with acute (< 10 days from onset) unilateral vestibular neuritis and low VOR gains. We found that when corrective saccades are larger than 10°, the slow-phase component of the VOR is inhibited, even though inhibition increases further the time to reacquire the fixation target. We also found that 1) saccades are faster and more accurate if the residual VOR gain is higher, 2) saccades also compensate for the head displacement that occurs during the saccade, and 3) the amplitude-peak velocity relationship of the larger corrective saccades deviates from that of head-fixed saccades of the same size. We propose a mathematical model to account for these findings hypothesizing that covert saccades are driven by a desired gaze position signal based on a prediction of head displacement using vestibular and extravestibular signals, covert saccades are controlled by a gaze feedback loop, and the VOR command is modulated according to predicted saccade amplitude. A central and novel feature of the model is that the brain develops two separate estimates of head rotation, one for generating saccades while the head is moving and the other for generating slow phases. Furthermore, while the model was developed for gaze-stabilizing behavior during passively induced head impulses, it also simulates both active gaze-stabilizing and active gaze-shifting eye movements.NEW & NOTEWORTHY During active or passive head impulses while fixating stationary targets, low vestibulo-ocular gain subjects produce corrective saccades when the head is still moving. The mechanisms driving these covert saccades are poorly understood. We propose a mathematical model showing that the brain develops two separate estimates of head rotation: a lower level one, presumably in the vestibular nuclei, used to generate the slow-phase component of the response, and a higher level one, within a gaze feedback loop, used to drive corrective saccades.
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Affiliation(s)
- Paolo Colagiorgio
- Department of Electrical, Computer and Biomedical Engineering, University of Pavia, Pavia, Italy
| | - Maurizio Versino
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy.,Laboratory of Neuro-otology and Neuro-ophthalmology, C. Mondino National Neurological Institute, Pavia, Italy
| | - Silvia Colnaghi
- Department of Public Health, Experimental and Forensic Medicine, University of Pavia, Pavia, Italy.,Inter-Department Multiple Sclerosis Research Centre, C. Mondino National Neurological Institute, Pavia, Italy
| | - Silvia Quaglieri
- UOC Otorinolaringoiatria, Fondazione IRCCS San Matteo and University of Pavia, Pavia, Italy
| | - Marco Manfrin
- UOC Otorinolaringoiatria, Fondazione IRCCS San Matteo and University of Pavia, Pavia, Italy
| | - Ewa Zamaro
- Department of Otorhinolaryngology, Head and Neck Surgery, lnselspital, Bern University Hospital, University of Bern, Bern, Switzerland; and
| | - Georgios Mantokoudis
- Department of Otorhinolaryngology, Head and Neck Surgery, lnselspital, Bern University Hospital, University of Bern, Bern, Switzerland; and
| | - David S Zee
- Department of Neurology, Otolaryngology-Head and Neck Surgery, Neuroscience, Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Stefano Ramat
- Department of Electrical, Computer and Biomedical Engineering, University of Pavia, Pavia, Italy;
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14
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Yang CJ, Lee JY, Kang BC, Lee HS, Yoo MH, Park HJ. Quantitative analysis of gains and catch-up saccades of video-head-impulse testing by age in normal subjects. Clin Otolaryngol 2016; 41:532-8. [PMID: 26453356 DOI: 10.1111/coa.12558] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/04/2015] [Indexed: 12/01/2022]
Abstract
OBJECTIVES To evaluate video-head-impulse test (vHIT) results in normal subjects, to determine the normative values of vHIT for the vestibulo-ocular reflex (VOR) and to characterise the catch-up saccades (CSs). DESIGN Prospective cohort study. SETTING Tertiary care academic referral centre. PARTICIPANTS Fifty healthy subjects with no history of vestibular impairment, ten each in their 20's, 30's, 40's, 50's and 60's, underwent vHITs in the lateral semicircular canal plane. MAIN OUTCOME MEASURES vHIT gains and the incidence and amplitudes of covert and overt CSs. RESULTS The mean vHIT gain was 1.02 ± 0.07, and the mean gain asymmetry was 2.39 ± 1.96%, with no significant differences among age groups. CSs were observed during 22.6% of the trials and in 49% of the ears. The incidence of CSs was not associated with age. The mean velocity of CSs was 55.5 ± 16.9°/s, and its mean interaural difference was 11.8 ± 10.7°/s. CONCLUSIONS vHIT gains were consistently equal to 1.0 in all age groups (20's to 60's), suggesting that abnormal criteria for vHIT gain (e.g. 0.8) and gain asymmetry (e.g. 8%) can be used, regardless of age. CSs were observed in about half of normal ears, suggesting that VOR is a hypometric system. The amplitudes and interaural difference of CSs were also similar in all age groups, suggesting that abnormal criteria for CS amplitude (e.g. 100°/s) and interaural difference (e.g. 40°/s) can be used, regardless of age.
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Affiliation(s)
- C J Yang
- Department of Otolaryngology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - J Y Lee
- Department of Otolaryngology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - B C Kang
- Department of Otolaryngology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - H S Lee
- Department of Otolaryngology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - M H Yoo
- Department of Otorhinolaryngology-Head & Neck Surgery, Korea University Ansan Hospital, Ansan, Korea
| | - H J Park
- Department of Otolaryngology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
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15
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Pilot study of a new rehabilitation tool: improved unilateral short-term adaptation of the human angular vestibulo-ocular reflex. Otol Neurotol 2015; 35:e310-6. [PMID: 25122595 DOI: 10.1097/mao.0000000000000539] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
HYPOTHESIS Unilateral vestibulo-ocular reflex (VOR) short-term adaptation training causes some increase toward the nonadapting side (~30% of increase on adapting side). We conducted a pilot study to determine if the increase could be reduced by providing a visual stimulus during rotations to the nonadapting side. BACKGROUND Unilateral vestibular short-term adaptation is a technique that could increase the ipsilesional VOR response of vestibular patients with unilateral hypofunction. However, this technique results in the VOR response increasing for rotations toward the nonadapting (normal) side, which is undesirable because the VOR will be overcompensatory (causing nonstable vision) during head rotations toward the normal side. METHODS We built a portable helmet device that sensed horizontal angular head velocity to generate a visual target that required a preset VOR gain (eye velocity/head velocity) for optimal image stabilization that could be set differently for leftward and rightward head rotations. We tested 10 subjects (six controls and four patients with vestibular hypofunction). We measured the active and passive VOR gain during high-peak-acceleration, unilateral, transient head rotations (head impulses) before and after unilateral VOR adaptation training. RESULTS In control subjects, for rotations toward the adapting side (target gain = 1.5), the VOR gain increased because of training by 26.1% ± 23.4% during active head impulses and by 14.6% ± 13.0% during passive head impulses. In contrast, for rotations toward the nonadapting side, there were no statistically significant increases. CONCLUSION A visual stimulus driving the VOR gain to unity toward the nonadapting side aids unilateral adaptation more so than no visual stimulus.
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16
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Jamali M, Mitchell DE, Dale A, Carriot J, Sadeghi SG, Cullen KE. Neuronal detection thresholds during vestibular compensation: contributions of response variability and sensory substitution. J Physiol 2013; 592:1565-80. [PMID: 24366259 DOI: 10.1113/jphysiol.2013.267534] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The vestibular system is responsible for processing self-motion, allowing normal subjects to discriminate the direction of rotational movements as slow as 1-2 deg s(-1). After unilateral vestibular injury patients' direction-discrimination thresholds worsen to ∼20 deg s(-1), and despite some improvement thresholds remain substantially elevated following compensation. To date, however, the underlying neural mechanisms of this recovery have not been addressed. Here, we recorded from first-order central neurons in the macaque monkey that provide vestibular information to higher brain areas for self-motion perception. Immediately following unilateral labyrinthectomy, neuronal detection thresholds increased by more than two-fold (from 14 to 30 deg s(-1)). While thresholds showed slight improvement by week 3 (25 deg s(-1)), they never recovered to control values - a trend mirroring the time course of perceptual thresholds in patients. We further discovered that changes in neuronal response variability paralleled changes in sensitivity for vestibular stimulation during compensation, thereby causing detection thresholds to remain elevated over time. However, we found that in a subset of neurons, the emergence of neck proprioceptive responses combined with residual vestibular modulation during head-on-body motion led to better neuronal detection thresholds. Taken together, our results emphasize that increases in response variability to vestibular inputs ultimately constrain neural thresholds and provide evidence that sensory substitution with extravestibular (i.e. proprioceptive) inputs at the first central stage of vestibular processing is a neural substrate for improvements in self-motion perception following vestibular loss. Thus, our results provide a neural correlate for the patient benefits provided by rehabilitative strategies that take advantage of the convergence of these multisensory cues.
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Affiliation(s)
- Mohsen Jamali
- McGill University, Aerospace Medical Research Unit, MacIntyre Medical Sciences Bldg, 3655 Prom Sir William Osler, Montreal, Quebec, Canada, H3G 1Y6.
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17
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Kheradmand A, Zee DS. The bedside examination of the vestibulo-ocular reflex (VOR): an update. Rev Neurol (Paris) 2012; 168:710-9. [PMID: 22981296 PMCID: PMC4066458 DOI: 10.1016/j.neurol.2012.07.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 07/17/2012] [Indexed: 10/27/2022]
Abstract
Diagnosing dizzy patients remains a daunting challenge to the clinician in spite of modern imaging and increasingly sophisticated electrophysiological testing. Here we review the major bedside tests of the vestibulo-ocular reflex and how, when combined with a proper examination of the other eye movement systems, one can arrive at an accurate vestibular diagnosis.
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Affiliation(s)
- A Kheradmand
- Departments of Neurology, The Johns Hopkins Hospital, Oculomotor Lab, Path 2-210, 600 N. Wolfe street, Baltimore, MD 21287, USA.
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18
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Unidirectional rotations produce asymmetric changes in horizontal VOR gain before and after unilateral labyrinthectomy in macaques. Exp Brain Res 2011; 210:651-60. [PMID: 21431432 DOI: 10.1007/s00221-011-2622-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Accepted: 02/24/2011] [Indexed: 10/18/2022]
Abstract
Unilateral vestibular lesions cause marked asymmetry in the horizontal vestibulo-ocular reflex (VOR) during rapid head rotations, with VOR gain being lower for head rotations toward the lesion than for rotations in the opposite direction. Reducing this gain asymmetry by enhancing ipsilesional responses would be an important step toward improving gaze stability following vestibular lesions. To that end, there were two goals in this study. First, we wanted to determine whether we could selectively increase VOR gain in only one rotational direction in normal monkeys by exposing them to a training session comprised of a 3-h series of rotations in only one direction (1,000°/s² acceleration to a plateau of 150°/s for 1 s) while they wore 1.7 × magnifying spectacles. Second, in monkeys with unilateral vestibular lesions, we designed a paradigm intended to reduce the gain asymmetry by rotating the monkeys toward the side of the lesion in the same way as above but without spectacles. There were three main findings (1) unidirectional rotations with magnifying spectacles result in gain asymmetry in normal monkeys, (2) gain asymmetry is reduced when animals are rotated towards the side of the labyrinthectomy via the ipsilesional rotation paradigm, and (3) repeated training causes lasting reduction in VOR gain asymmetry.
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19
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Tian JR, Crane BT, Ishiyama A, Demer JL. Three dimensional kinematics of rapid compensatory eye movements in humans with unilateral vestibular deafferentation. Exp Brain Res 2007; 182:143-55. [PMID: 17549461 PMCID: PMC2104540 DOI: 10.1007/s00221-007-0977-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2006] [Accepted: 04/27/2007] [Indexed: 10/23/2022]
Abstract
Saccades executed with the head stationary have kinematics conforming to Listing's law (LL), confining the ocular rotational axis to Listing's plane (LP). In unilateral vestibular deafferentation (UVD), the vestibulo-ocular reflex (VOR), which does not obey LL, has at high head acceleration a slow phase that has severely reduced velocity during ipsilesional rotation, and mildly reduced velocity during contralesional rotation. Studying four subjects with chronic UVD using 3D magnetic search coils, we investigated kinematics of stereotypic rapid eye movements that supplement the impaired VOR. We defined LP with the head immobile, and expressed eye and head movements as quaternions in LP coordinates. Subjects underwent transient whole body yaw at peak acceleration 2,800 degrees /s(2) while fixating targets centered, or 20 degrees up or down prior to rotation. The VOR shifted ocular torsion out of LP. Vestibular catch-up saccades (VCUS) occurred with mean latency 90 +/- 44 ms (SD) from ipsilesional rotation onset, maintained initial non-LL torsion so that their quaternion trajectories paralleled LP, and had velocity axes changing by half of eye position. During contralesional rotation, rapid eye movements occurred at mean latency 135 +/- 36 ms that were associated with abrupt decelerations (ADs) of the horizontal slow phase correcting 3D deviations in its velocity axis, with quaternion trajectories not paralleling LP. Rapid eye movements compensating for UVD have two distinct kinematics. VCUS have velocity axis dependence on eye position consistent with LL, so are probably programmed in 2D by neural circuits subserving visual saccades. ADs have kinematics that neither conform to LL nor match the VOR axis, but appear instead programmed in 3D to correct VOR axis errors.
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Affiliation(s)
- Jun-Ru Tian
- Department of Ophthalmology, University of California, Los Angeles, CA 90095-7002, USA.
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20
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Migliaccio AA, Della Santina CC, Carey JP, Minor LB, Zee DS. The effect of binocular eye position and head rotation plane on the human torsional vestibuloocular reflex. Vision Res 2006; 46:2475-86. [PMID: 16545855 DOI: 10.1016/j.visres.2006.02.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2005] [Revised: 02/03/2006] [Accepted: 02/06/2006] [Indexed: 11/16/2022]
Abstract
We examined how the gain of the torsional vestibulo-ocular reflex (VOR) (defined as the instantaneous eye velocity divided by inverted head velocity) in normal humans is affected by eye position, target distance, and the plane of head rotation. In six normal subjects we measured three-dimensional (3D) eye and head rotation axes using scleral search coils, and 6D head position using a magnetic angular and linear position measurement device, during low-amplitude (approximately 20 degrees ), high-velocity (approximately 200 degrees/s), high-acceleration (approximately 4000 degrees /s2) rapid head rotations or 'impulses.' Head impulses were imposed manually and delivered in five planes: yaw (horizontal canal plane), pitch, roll, left anterior-right posterior canal plane (LARP), and right anterior-left posterior canal plane (RALP). Subjects were instructed to fix on one of six targets at eye level. Targets were either straight-ahead, 20 degrees left or 20 degrees right from midline, at distance 15 or 124 cm from the subject. Two subjects also looked at more eccentric targets, 30 degrees left or 30 degrees right from midline. We found that the vertical and horizontal VOR gains increased with the proximity of the target to the subject. Previous studies suggest that the torsional VOR gain should decrease with target proximity. We found, however, that the torsional VOR gain did not change for all planes of head rotation and for both target distances. We also found a dynamic misalignment of the vertical positions of the eyes during the torsional VOR, which was greatest during near viewing with symmetric convergence. This dynamic vertical skew during the torsional VOR arises, in part, because when the eyes are converged, the optical axes are not parallel to the naso-occipital axes around which the eyes are rotating. In five of six subjects, the average skew ranged 0.9 degrees -2.9 degrees and was reduced to <0.4 degrees by a 'torsional' quick-phase (around the naso-occipital axis) occurring <110 ms after the onset of the impulse. We propose that the torsional quick-phase mechanism during the torsional VOR could serve at least three functions: (1) resetting the retinal meridians closer to their usual orientation in the head, (2) correcting for the 'skew' deviation created by misalignment between the axes around which the eyes are rotating and the line of sight, and (3) taking the eyes back toward Listing's plane.
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Affiliation(s)
- Americo A Migliaccio
- Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University, MA 21205, USA.
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