A dynamic model for eye-position-dependence of spontaneous nystagmus in acute unilateral vestibular deficit (Alexander's Law)

2012 ◽  
Vol 37 (1) ◽  
pp. 141-149 ◽  
Author(s):  
Elham Khojasteh ◽  
Christopher J. Bockisch ◽  
Dominik Straumann ◽  
Stefan C. A. Hegemann
Keyword(s):  
Dynamic Model ◽  
Spontaneous Nystagmus ◽  
Eye Position ◽  
Alexander’S Law ◽  
Position Dependence ◽  
Vestibular Deficit

Eye Position Dependence of Innervation On-directions of Motoneurons in the Monkey

1996 ◽  
Vol 781 (1 Lipids and Sy) ◽  
pp. 629-632 ◽  
Author(s):  
K. HEPP ◽  
Y. SUZUKI ◽  
D. STRAUMANN ◽  
B. J. M. HESS ◽  
V. HENN
Keyword(s):  
Eye Position ◽  
Position Dependence

Eye position effects in saccadic adaptation in macaque monkeys

2012 ◽  
Vol 108 (10) ◽  
pp. 2819-2826 ◽  
Author(s):  
Svenja Wulff ◽  
Annalisa Bosco ◽  
Katharina Havermann ◽  
Giacomo Placenti ◽  
Patrizia Fattori ◽  
...  
Keyword(s):  
Macaca Fascicularis ◽  
Species Differences ◽  
The Other ◽  
Eye Position ◽  
Saccadic Amplitude ◽  
Position Effects ◽  
Starting Position ◽  
Saccadic Adaptation ◽  
Gaussian Profile ◽  
Position Dependence

The saccadic amplitude of humans and monkeys can be adapted using intrasaccadic target steps in the McLaughlin paradigm. It is generally believed that, as a result of a purely retinal reference frame, after adaptation of a saccade of a certain amplitude and direction, saccades of the same amplitude and direction are all adapted to the same extent, independently from the initial eye position. However, recent studies in humans have put the pure retinal coding in doubt by revealing that the initial eye position has an effect on the transfer of adaptation to saccades of different starting points. Since humans and monkeys show some species differences in adaptation, we tested the eye position dependence in monkeys. Two trained Macaca fascicularis performed reactive rightward saccades from five equally horizontally distributed starting positions. All saccades were made to targets with the same retinotopic motor vector. In each session, the saccades that started at one particular initial eye position, the adaptation position, were adapted to shorter amplitude, and the adaptation of the saccades starting at the other four positions was measured. The results show that saccades that started at the other positions were less adapted than saccades that started at the adaptation position. With increasing distance between the starting position of the test saccade and the adaptation position, the amplitude change of the test saccades decreased with a Gaussian profile. We conclude that gain-decreasing saccadic adaptation in macaques is specific to the initial eye position at which the adaptation has been induced.

Paroxysmal spontaneous nystagmus and vertigo evoked by lateral eye position

Neurology ◽  
1987 ◽  
Vol 37 (9) ◽  
pp. 1553-1553 ◽  
Author(s):  
U. Buttner ◽  
A. Straube ◽  
Th. Brandt
Keyword(s):  
Spontaneous Nystagmus ◽  
Eye Position ◽  
Lateral Eye

Alexander's Law Revisited

2008 ◽  
Vol 19 (08) ◽  
pp. 630-638 ◽  
Author(s):  
Gary P. Jacobson ◽  
Devin L. McCaslin ◽  
David M. Kaylie
Keyword(s):  
Eye Movement ◽  
Vestibular System ◽  
Case Reports ◽  
Spontaneous Nystagmus ◽  
Ocular Motility ◽  
Vestibular Evoked Myogenic Potential ◽  
Data Collection And Analysis ◽  
Alexander’S Law ◽  
Neuro Imaging ◽  
Case Data

Background: It is a common occurrence in the balance function laboratory to evaluate patients in the post-acute period following unilateral vestibular system impairment. It is important to be able to differentiate spontaneous nystagmus (SN) emanating from peripheral vestibular system impairments from asymmetric gaze-evoked nystagmus (GEN) that originates from central ocular motility impairment. Purpose: To describe the three elements of Alexander's Law (AL) that have been used to define SN from unilateral peripheral impairment. Additionally, a fourth element is described (i.e., augmentation of spontaneous nystagmus from unilateral peripheral vestibular system impairment) that differentiates nystagmus of peripheral vestibular system origin from nystagmus that originates from a central eye movement disorder. Research Design: Case reports Study Sample: Case data were obtained from two patients both showing a nystagmus that followed AL. Intervention: None Data Collection And Analysis: Videonystagmography (VNG), rotational, vestibular evoked myogenic potential (VEMP), and neuro-imaging studies were presented for each patient. Results: The nystagmus in Case 1 occurred as a result of a unilateral, peripheral, vestibular system impairment. The nystagmus was direction-fixed and intensified in the vision-denied condition. The nystagmus in Case 2, by appearance identical to that in Case 1, was an asymmetric gaze-evoked nystagmus originating from a space-occupying lesion in the cerebello-pontine angle. Unlike Case 1, the nystagmus did not augment in the vision-denied condition. Conclusions: Although nystagmus following AL usually occurs in acute peripheral vestibular system impairment, it can occur in cases of central eye movement impairment. The key element is whether the SN that follows AL is attenuated or augmented in the vision-denied condition. The SN from a unilateral peripheral vestibular system impairment should augment in the vision denied condition. An asymmetric GEN will either not augment, decrease in magnitude, or disappear entirely, in the vision-denied condition.

Vertical Eye Position–Dependence of the Human Vestibuloocular Reflex During Passive and Active Yaw Head Rotations

1999 ◽  
Vol 81 (5) ◽  
pp. 2415-2428 ◽  
Author(s):  
Matthew J. Thurtell ◽  
Ross A. Black ◽  
G. Michael Halmagyi ◽  
Ian S. Curthoys ◽  
Swee T. Aw
Keyword(s):  
Three Dimensional ◽  
Head Position ◽  
Eye Position ◽  
Vestibuloocular Reflex ◽  
Head Velocity ◽  
High Acceleration ◽  
Position Dependence ◽  
Head Impulses ◽  
Eye Velocity ◽  
Head Rotations

Vertical eye position–dependence of the human vestibuloocular reflex during passive and active yaw head rotations. The effect of vertical eye-in-head position on the compensatory eye rotation response to passive and active high acceleration yaw head rotations was examined in eight normal human subjects. The stimuli consisted of brief, low amplitude (15–25°), high acceleration (4,000–6,000°/s2) yaw head rotations with respect to the trunk (peak velocity was 150–350°/s). Eye and head rotations were recorded in three-dimensional space using the magnetic search coil technique. The input-output kinematics of the three-dimensional vestibuloocular reflex (VOR) were assessed by finding the difference between the inverted eye velocity vector and the head velocity vector (both referenced to a head-fixed coordinate system) as a time series. During passive head impulses, the head and eye velocity axes aligned well with each other for the first 47 ms after the onset of the stimulus, regardless of vertical eye-in-head position. After the initial 47-ms period, the degree of alignment of the eye and head velocity axes was modulated by vertical eye-in-head position. When fixation was on a target 20° up, the eye and head velocity axes remained well aligned with each other. However, when fixation was on targets at 0 and 20° down, the eye velocity axis tilted forward relative to the head velocity axis. During active head impulses, the axis tilt became apparent within 5 ms of the onset of the stimulus. When fixation was on a target at 0°, the velocity axes remained well aligned with each other. When fixation was on a target 20° up, the eye velocity axis tilted backward, when fixation was on a target 20° down, the eye velocity axis tilted forward. The findings show that the VOR compensates very well for head motion in the early part of the response to unpredictable high acceleration stimuli—the eye position– dependence of the VOR does not become apparent until 47 ms after the onset of the stimulus. In contrast, the response to active high acceleration stimuli shows eye position–dependence from within 5 ms of the onset of the stimulus. A model using a VOR-Listing’s law compromise strategy did not accurately predict the patterns observed in the data, raising questions about how the eye position–dependence of the VOR is generated. We suggest, in view of recent findings, that the phenomenon could arise due to the effects of fibromuscular pulleys on the functional pulling directions of the rectus muscles.

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