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https://www.readbyqxmd.com/read/28292832/functional-organization-of-vestibulo-ocular-responses-in-abducens-motoneurons
#1
Haike Dietrich, Stefan Glasauer, Hans Straka
Vestibulo-ocular reflexes (VOR) are the dominating contributors to gaze stabilization in all vertebrates. During horizontal head movements, abducens motoneurons form the final element of the reflex arc that integrates visuo-vestibular inputs into temporally precise motor commands for the lateral rectus eye muscle. Here, we studied a possible differentiation of abducens motoneurons into subtypes by evaluating their morphology, discharge properties and synaptic pharmacology in semi-intact in vitro preparations of larval Xenopus laevis Extracellular nerve recordings during sinusoidal head motion revealed a continuum of resting rates and activation thresholds during vestibular stimulation...
March 14, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28292694/asb-clinical-biomechanics-award-winner-2016-assessment-of-gaze-stability-within-24-48hours-post-concussion
#2
Nicholas G Murray, Nathan R D'Amico, Douglas Powell, Megan E Mormile, Katelyn E Grimes, Barry A Munkasy, Russell K Gore, Rebecca J Reed-Jones
BACKGROUND: Approximately 90% of athletes with concussion experience a certain degree of visual system dysfunction immediately post-concussion. Of these abnormalities, gaze stability deficits are denoted as among the most common. Little research quantitatively explores these variables post-concussion. As such, the purpose of this study was to investigate and compare gaze stability between a control group of healthy non-injured athletes and a group of athletes with concussions 24-48hours post-injury...
March 6, 2017: Clinical Biomechanics
https://www.readbyqxmd.com/read/28271408/moving-or-being-moved-that-makes-a-difference
#3
Hans Straka, Boris P Chagnaud
During head/body movements, gaze stability is ensured by transformation of motion-related sensory signals into respective motor commands. Passively induced motion in all vertebrates including amphibians evokes a robust vestibulo-ocular reflex, suggesting an equally important role of this motor reaction during actively induced motion. However, during self-induced movements including locomotion, motor efference copies offer a convenient additional substrate for counteracting retinal image displacements. During such locomotor activity in Xenopus laevis tadpoles, spinal central pattern generator-derived efference copies elicit spatio-temporally specific eye movements, which are functionally appropriate to offset swimming-related retinal image displacements...
March 7, 2017: Journal of Neurology
https://www.readbyqxmd.com/read/28242737/unchanging-visions-the-effects-and-limitations-of-ocular-stillness
#4
REVIEW
Susana Martinez-Conde, Stephen L Macknik
Scientists have pondered the perceptual effects of ocular motion, and those of its counterpart, ocular stillness, for over 200 years. The unremitting 'trembling of the eye' that occurs even during gaze fixation was first noted by Jurin in 1738. In 1794, Erasmus Darwin documented that gaze fixation produces perceptual fading, a phenomenon rediscovered in 1804 by Ignaz Paul Vital Troxler. Studies in the twentieth century established that Jurin's 'eye trembling' consisted of three main types of 'fixational' eye movements, now called microsaccades (or fixational saccades), drifts and tremor...
April 19, 2017: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
https://www.readbyqxmd.com/read/28194135/inaccurate-saccades-and-enhanced-vestibulo-ocular-reflex-suppression-during-combined-eye-head-movements-in-patients-with-chronic-neck-pain-possible-implications-for-cervical-vertigo
#5
Janine L Johnston, Pierre M Daye, Glen T D Thomson
BACKGROUND: The primate ocular motor system is designed to acquire peripheral targets of interest by coordinating visual, vestibular, and neck muscle activation signals. The vestibulo-ocular reflex (VOR) is greatly reduced at the onset of large eye-head (gaze) saccades and resumes before the end of the saccades to stabilize eye-in-orbit and ensure accurate target acquisition. Previous studies have relied on manipulating head movements in normal individuals to study VOR suppression and gaze kinematics...
2017: Frontiers in Neurology
https://www.readbyqxmd.com/read/28192092/peripheral-oculomotor-training-in-individuals-with-healthy-visual-systems-effects-of-training-and-training-transfer
#6
Dylan Rose, Peter Bex
Individuals with pathological or simulated central visual field loss can be trained to use a preferred retinal locus (PRL) as a substitute for their non-functioning fovea. The functional benefits of a stable PRL are well documented, but little is known about oculomotor adaptations during PRL acquisition or transfer of training to another location in response to real or simulated disease progression. In this study, eight normally-sighted observers were trained to use a pseudo-PRL (pPRL) at one of two locations by guiding an eccentrically placed, gaze-contingent ring over a fixation target...
February 25, 2017: Vision Research
https://www.readbyqxmd.com/read/28163007/vestibular-contributions-to-high-level-sensorimotor-functions
#7
W Pieter Medendorp, Luc J P Selen
The vestibular system, which detects motion and orientation of the head in space, is known to be important in controlling gaze to stabilize vision, to ensure postural stability and to provide our sense of self-motion. While the brain's computations underlying these functions are extensively studied, the role of the vestibular system in higher level sensorimotor functions is less clear. This review covers new research on the vestibular influence on perceptual judgments, motor decisions, and the ability to learn multiple motor actions...
February 2, 2017: Neuropsychologia
https://www.readbyqxmd.com/read/28114567/retinotopic-to-spatiotopic-mapping-in-blind-patients-implanted-with-the-argus-ii-retinal-prosthesis
#8
Avi Caspi, Arup Roy, Jessy D Dorn, Robert J Greenberg
Purpose: To quantify the precision of mapping from retinotopic (retina-centered) to spatiotopic (world-centered) coordinates in blind humans implanted with a retinal prosthesis device. Additionally, to demonstrate that an eye tracker can be calibrated on sightless patients based on the percept from a visual implant. Methods: We directly activated epiretinal electrodes to create retinotopic stimuli and recorded the location of the percept at world-based coordinates...
January 1, 2017: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/28065472/adaptive-changes-in-running-kinematics-as-a-function-of-head-stability-demands-and-their-effect-on-shock-transmission
#9
Jongil Lim, Michael A Busa, Richard E A van Emmerik, Joseph Hamill
This study aimed to identify adaptive changes in running kinematics and impact shock transmission as a function of head stability requirements. Fifteen strides from twelve recreational runners were collected during preferred speed treadmill running. Head stability demands were manipulated through real-time visual feedback that required head-gaze orientation to maintain within boxes of different sizes, ranging from 21° to 3° of visual angle with 3° decrements. The main outcome measures were tibial and head peak accelerations in the time and frequency domains (impact and active phases), shock transmission from tibia to head, stride parameters, and sagittal plane joint kinematics...
December 29, 2016: Journal of Biomechanics
https://www.readbyqxmd.com/read/28065412/quantitative-predictions-orchestrate-visual-signaling-in-drosophila
#10
Anmo J Kim, Lisa M Fenk, Cheng Lyu, Gaby Maimon
Vision influences behavior, but ongoing behavior also modulates vision in animals ranging from insects to primates. The function and biophysical mechanisms of most such modulations remain unresolved. Here, we combine behavioral genetics, electrophysiology, and high-speed videography to advance a function for behavioral modulations of visual processing in Drosophila. We argue that a set of motion-sensitive visual neurons regulate gaze-stabilizing head movements. We describe how, during flight turns, Drosophila perform a set of head movements that require silencing their gaze-stability reflexes along the primary rotation axis of the turn...
January 12, 2017: Cell
https://www.readbyqxmd.com/read/28056109/postural-ataxia-in-cerebellar-downbeat-nystagmus-its-relation-to-visual-proprioceptive-and-vestibular-signals-and-cerebellar-atrophy
#11
Christoph Helmchen, Jan-Birger Kirchhoff, Martin Göttlich, Andreas Sprenger
BACKGROUND: The cerebellum integrates proprioceptive, vestibular and visual signals for postural control. Cerebellar patients with downbeat nystagmus (DBN) complain of unsteadiness of stance and gait as well as blurred vision and oscillopsia. OBJECTIVES: The aim of this study was to elucidate the differential role of visual input, gaze eccentricity, vestibular and proprioceptive input on the postural stability in a large cohort of cerebellar patients with DBN, in comparison to healthy age-matched control subjects...
2017: PloS One
https://www.readbyqxmd.com/read/28054910/examining-effects-of-physical-exertion-on-the-dynamic-visual-acuity-test-in-collegiate-athletes
#12
Jessie N Patterson, Anna M Murphy, Julie A Honaker
BACKGROUND: Acute symptoms of dizziness and/or imbalance commonly experienced in athletes postconcussion are speculated to arise from dysfunction at multiple levels (i.e., inner ear or central vestibular system) to appropriately integrate afferent sensory information. Disruption along any pathway of the balance system can result in symptoms of dizziness, decreased postural control function (vestibulospinal reflex), and reduced vestibulo-ocular reflex function. This may also lead to decreased gaze stability with movements of the head and may account for symptoms of blurred vision or diplopia reported in almost half of athletes sustaining a concussion...
January 2017: Journal of the American Academy of Audiology
https://www.readbyqxmd.com/read/27981586/gaze-evoked-nystagmus-induced-by-alcohol-intoxication
#13
Fausto Romano, Alexander A Tarnutzer, Dominik Straumann, Stefano Ramat, Giovanni Bertolini
KEY POINTS: The cerebellum is the core structure controlling gaze stability. Chronic cerebellar diseases and acute alcohol intoxication affect cerebellar function, inducing, among others, gaze instability as gaze-evoked nystagmus. Gaze-evoked nystagmus is characterized by increased centripetal eye-drift. It is used as an important diagnostic sign for patients with cerebellar degeneration and to assess the 'driving while intoxicated' condition. We quantified the effect of alcohol on gaze-holding using an approach allowing, for the first time, the comparison of deficits induced by alcohol intoxication and cerebellar degeneration...
March 15, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/27877114/ontogenetic-development-of-vestibulo-ocular-reflexes-in-amphibians
#14
REVIEW
Francisco Branoner, Boris P Chagnaud, Hans Straka
Vestibulo-ocular reflexes (VOR) ensure gaze stability during locomotion and passively induced head/body movements. In precocial vertebrates such as amphibians, vestibular reflexes are required very early at the onset of locomotor activity. While the formation of inner ears and the assembly of sensory-motor pathways is largely completed soon after hatching, angular and translational/tilt VOR display differential functional onsets and mature with different time courses. Otolith-derived eye movements appear immediately after hatching, whereas the appearance and progressive amelioration of semicircular canal-evoked eye movements is delayed and dependent on the acquisition of sufficiently large semicircular canal diameters...
2016: Frontiers in Neural Circuits
https://www.readbyqxmd.com/read/27874249/role-of-neural-integrators-in-oculomotor-systems-a%C3%A2-systematic-narrative-literature-review
#15
REVIEW
Katherine Sanchez, Fiona J Rowe
PURPOSE: To evaluate the role of neural integrators (NI) in the oculomotor system. METHODS: A literature search was carried out using several electronic databases during the months of June 2014 to March 2015. The following keywords were used to generate focused results: 'neural integrators', 'gaze-holding', 'oculomotor integration', 'impaired gaze-holding', 'gaze evoked nystagmus' and 'gaze dysfunction'. Further materials were found through searching relevant articles within reference lists...
November 22, 2016: Acta Ophthalmologica
https://www.readbyqxmd.com/read/27864084/development-and-regeneration-of-vestibular-hair-cells-in-mammals
#16
REVIEW
Joseph C Burns, Jennifer S Stone
Vestibular sensation is essential for gaze stabilization, balance, and perception of gravity. The vestibular receptors in mammals, Type I and Type II hair cells, are located in five small organs in the inner ear. Damage to hair cells and their innervating neurons can cause crippling symptoms such as vertigo, visual field oscillation, and imbalance. In adult rodents, some Type II hair cells are regenerated and become re-innervated after damage, presenting opportunities for restoring vestibular function after hair cell damage...
November 15, 2016: Seminars in Cell & Developmental Biology
https://www.readbyqxmd.com/read/27837042/gaze-shift-patterns-during-a-jump-with-full-turn-in-male-gymnasts
#17
Yusuke Sato, Shuko Torii, Masaharu Sasaki, Thomas Heinen
When airborne, gymnasts skillfully control their movements to achieve a successful landing. Utilizing visual information from task-specific eye-body coordination patterns (i.e., visual spotting) is thought to be important for gymnasts in the performance of aerial skills. The purpose of this study was to assess the interplay of eye movements and body movements in an aerial skill with a rotation about the longitudinal axis, namely a straight jump with full turn. Participants were 10 skilled male gymnasts (age [M ± SD], 23...
November 11, 2016: Perceptual and Motor Skills
https://www.readbyqxmd.com/read/27802139/visual-resolution-and-contrast-sensitivity-in-two-benthic-sharks
#18
Laura A Ryan, Nathan S Hart, Shaun P Collin, Jan M Hemmi
Sharks have long been described as having 'poor' vision. They are cone monochromats and anatomical estimates suggest they have low spatial resolution. However, there are no direct behavioural measurements of spatial resolution or contrast sensitivity. This study estimates contrast sensitivity and spatial resolution of two species of benthic sharks, the Port Jackson shark, Heterodontus portusjacksoni, and the brown-banded bamboo shark, Chiloscyllium punctatum, by recording eye movements in response to optokinetic stimuli...
December 15, 2016: Journal of Experimental Biology
https://www.readbyqxmd.com/read/27781300/functional-synergy-between-postural-and-visual-behaviors-when-performing-a-difficult-precise-visual-task-in-upright-stance
#19
Cédrick T Bonnet, Sébastien Szaffarczyk, Stéphane Baudry
Previous works usually report greater postural stability in precise visual tasks (e.g., gaze-shift tasks) than in stationary-gaze tasks. However, existing cognitive models do not fully support these results as they assume that performing an attention-demanding task while standing would alter postural stability because of the competition of attention between the tasks. Contrary to these cognitive models, attentional resources may increase to create a synergy between visual and postural brain processes to perform precise oculomotor behaviors...
October 26, 2016: Cognitive Science
https://www.readbyqxmd.com/read/27780044/evolution-of-biological-image-stabilization
#20
REVIEW
Ben J Hardcastle, Holger G Krapp
The use of vision to coordinate behavior requires an efficient control design that stabilizes the world on the retina or directs the gaze towards salient features in the surroundings. With a level gaze, visual processing tasks are simplified and behaviorally relevant features from the visual environment can be extracted. No matter how simple or sophisticated the eye design, mechanisms have evolved across phyla to stabilize gaze. In this review, we describe functional similarities in eyes and gaze stabilization reflexes, emphasizing their fundamental role in transforming sensory information into motor commands that support postural and locomotor control...
October 24, 2016: Current Biology: CB
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