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Vincent, Gautier. "Programmation des saccades oculaires." Paris, EHESS, 1999. http://www.theses.fr/1999EHESA010.
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Les informations visuelles portees par les mots peripheriques et utilisables pour la programmation des saccades oculaires lors de la lecture sont de deux types : de bas niveau (longueur, excentricite) ou de haut niveau (contenu linguistique : lexical, semantique. . . ). Les modeles de programmation des saccades oculaires se differencient en fonction de l'importance donnee aux informations visuelles de haut niveau nous pouvons distinguer deux types de modeles de programmation : les modeles pour lesquels l'analyse linguistique des mots peripheriques est suffisamment rapide pour influencer directement la programmation des saccades de progression, et les modeles pour lesquels l'analyse linguistique des mots peripheriques n'est pas suffisamment rapide. Nos conclusions determinent une position intermediaire et rejoignent celles proposees par le modele << strategie-tactiques >> (o'regan, 1990) : les processus de bas niveau fournissent tres rapidement des informations exploitables pour la programmation des saccades. Ces informations sont ensuite modulees au fur et a mesure que les processus d'analyse de haut niveau deviennent operationnels. A partir de nos analyses, nous avons defini un modelede programmation des saccades oculaires, base sur le centre de gravite pondere d'une carte topique d'activite cognitive. La ponderation est donnee par la valeur des points de la carte, et la position d'arrivee des saccades, par la localisation du centre de gravite pondere au sein de la carte. L'activite de cette carte represente l'integration progressive de l'activite cognitive globale associee au champ visuel peripherique. Cette activite est nulle au debut de la fixation, puis integre progressivement les informations de bas niveau puis de haut niveau, issues des mots peripheriques. Ce modele permet une reproduction precise de nos donnees (< 5% d'erreur), et complete le modele propose par findlay (1999).
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Lau, Li Wing. "Saccades to doubly-flashed targets." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ34089.pdf.
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Diamond, Mark R. "The effect of saccades on visual sensitivity and time perception." University of Western Australia. School of Psychology, 2003. http://theses.library.uwa.edu.au/adt-WU2003.0038.
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Considerable evidence indicates that visual sensitivity is reduced during saccadic eye movement. A central question has been whether saccadic suppression results from a non-visual central signal, or whether the obligate image motion that accompanies saccades is itself sufficient to mask vision. In the first of a series of experiments described here, the visual and non-visual effects of saccades were distinguished by measuring contrast sensitivity to luminance modulated low spatial frequency gratings, at 17 cd·m¯² and 0.17 cd·m¯², in saccade conditions and in conditions in which saccade-like image motion was produced by the rotation of a mirror but when observers’ eyes were kept still. The time course of suppression was examined by making measurements from well before image motion began until well after it had ended. A tenfold decrease in contrast sensitivity was found for luminance-modulated gratings with saccades, but little suppression was found with simulated saccades. Adding high contrast noise to the visual display increased the magnitude and the duration of the suppression during simulated saccades but had little effect on suppression produced by real saccades. At lower luminance, suppression was found to be reduced, and its course shallower than at higher luminance. Simulated saccades produced shallower suppression over a longer time course at both higher and lower luminance. In a second experiment the time course of contrast sensitivity to chromatically modulated gratings, at 17 cd·m¯², was examined. No suppression was found; rather there was some evidence of an enhancement of sensitivity, both before and after saccades, relative to fixation conditions. Differences in the effects of real and simulated saccades in the magnitude and time course of sensitivity loss with luminance modulated gratings suggest that saccadic suppression has an extraretinal component that acts on the magnocellular system; the pattern of enhancement found in the later experiment suggests a selective favouring of the parvocellular system both immediately prior to and immediately after saccades. The possibility that the degree of enhancement in sensitivity varies across the visual field was examined using spatially localized stimuli (either high spatial frequency chromatically modulated gratings or letter combinations). Sensitivity was found to decrease at the initial fixation point during the 75 ms prior to saccadic onset and simultaneously to improve at the saccadic target. In the immediate post-saccadic period, sensitivity at the saccadic target was found to exceed that which had been manifest at the initial fixation point prior to saccades, suggesting that post-saccadic enhancement may improve the temporal contrast between one fixation and the next. The final experiments investigated the possibility that our sense of continuity across saccades (as opposed to stability) is influenced by saccade-induced errors in locating events in time. The results of these experiments suggest that saccades can result in errors in judging (a) the time at which external events occur relative to saccadic onset, (b) the temporal order of visual events, and (c) the magnitude of temporal intervals. It is concluded that apparent time is generally foreshortened prior to saccades. This might be due to selective suppression of magnocellular activity and might function to hide saccades and their effects from our awareness. A speculative synthesis is presented based on the idea that recurrent feedback between the neocortical and cortical structures on the one hand, and the thalamic nuclei on the other, has special importance for perception around the time of saccades
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Blum, Bernhard M. "Torsional control of eye-head saccades." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-178260.
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Under natural conditions the head and the eye are both free to rotate about three mutuall orthogonal axes each (horizontal, vertical and torsional). Theoretically, these six degrees of freedom would allow any two-dimensional direction of the line of sight to be obtained by infinitely many torsional head and eye orientations. Yet, for any one gaze direction our brain chooses specific angles of torsion for the head and the eye. For steady fixation of distant targets with the head fixed and upright this observation is known as Donders' law (1847). It has been shown to hold independently of the direction of the rapid gaze shift (saccade) preceding a fixation. Surprisingly, despite considerable research on head and eye coordination the full implications of Donders' law still have not been analyzed for head-unrestrained gaze shifts. It has merely been studied whether torsional constraints hold, when gaze is returned repeatedly to the targets from single initial positions. The aim of this study was to see whether Donders' law holds after head-unrestrained saccades, independently of the saccade direction. Secondary objectives were to analyze whether the neural controls of the eye and the head are dependent or independent during this task and to collect and present control data for comparison with patient recordings in clinical context. Therefore, seven healthy human subjects made large head-unrestrained gaze shifts to a single set of visual targets during two separate conditions: 1) Repeated saccades to individual target positions from the same direction respectively (Star paradigm). 2) Repeated saccades to every target position from several different directions (Diamond paradigm). Three-dimensional orientations of head and eye were measured simultaneously with the magnetic search coil technique and consecutively plotted in three-dimensional space so that those orientations obeying Donders' law formed a surface. For each of the three body units the static orientations formed subspaces that resembled surfaces in the shape of twisted double saddles. Surfaces of head orientations had the most pronounced twist, eye in head surfaces were the most planar and surfaces of gaze orientations showed intermediate twist. The standard deviation of torsional residuals of the approximated surfaces (torsional thickness) was bigger for gaze than for the eye and smallest for the head.
Head and eye torsion, as averaged over individual fixations, were correlated differently within every subject, but between subjects there was no correlation. In summary, neither surface shapes nor torsional thickness of gaze, head or eye differed between the two conditions (Star/Diamond). With this it is shown for the first time that Donders' law of torsional control holds true for gaze, head and eye orientations independently of the direction of the preceding saccade. The absence of correlation between head and eye torsion can be explained by independent controllers of head and eye movements. This yields a new, further argument supporting recent models of neuronal gaze control that are based on the assumption of independent head and eye controllers. Studies with patients carrying lesions in possible target structures of such neuronal controllers are needed to further investigate these models. Finally, clinically-diagnostic relevance of this study arises from the comparison to results of studies on gaze coordination after midbrain lesions where patients exhibit an altered form of Donders' law.Unter natürlichen Bedingungen sind Rotationen von Kopf und Auge um jeweils drei voneinander unabhängige Raumachsen (Quer-, Hoch- und Längsachse) möglich. Diese sechs Freiheitsgrade würden beim Blick in jede zweidimensionale Richtung beliebige Drehungen um die Längsachse (Torsion) sowohl des Kopfes als auch des Auges erlauben. Unser Gehirn wählt jedoch in jeder Blickrichtung je einen spezifischen Torsionswinkel für Kopf und Auge. Für die Fixation entfernter Blickziele bei aufrechtem, unbewegtem Kopf wurde diese Tatsache als Donders' Law (1847) bekannt. Das Gesetz gilt unabhängig von der Richtung der der Fixation vorhergehenden raschen Blickbewegung (Sakkade). Überraschenderweise wurde trotz zahlreicher Untersuchungen zur Kopf- und Augenkoordination die vollständige Gültigkeit von Donders' Law bei Blickbewegungen mit bewegtem Kopf noch nicht gezeigt. Es wurde lediglich untersucht, ob die resultierenden Torsionsbeschränkungen weiter gelten, wenn der Blick wiederholt von denselben Ausgangspositionen auf verschiedene Punkte gerichtet wird. Hauptziel dieser Arbeit war zu prüfen, ob Donders' Law nach Sakkaden mit bewegtem Kopf unabhängig von der Sakkadenrichtung gilt. Zudem wurde analysiert, ob Kopf und Auge dabei einer gemeinsamen oder separaten neuronalen Kontrolle unterliegen, und es wurden Kontrolldaten zum Vergleich mit Patientenmessungen im klinischen Kontext gesammelt. Dazu führten sieben gesunde menschliche Probanden Sakkaden mit bewegtem Kopf zwischen einer Anordnung visueller Blickziele unter zwei Versuchsbedingungen durch: 1) Wiederholte Sakkaden auf jedes Ziel aus der jeweils gleichen Richtung (Star Paradigma). 2) Wiederholte Sakkaden auf jedes Ziel aus mehreren verschiedenen Richtungen (Diamond Paradigma). Die dreidimensionalen Kopf- und Augenbewegungen wurden simultan mit der magnetischen Search-Coil-Technik gemessen und zur Analyse räumlich dargestellt, so dass Positionen, die Donders' Law entsprechen, eine Fläche bilden. Für jede der drei Körpereinheiten lagen die statischen Positionen in Unterräumen, die Flächen in Form verdrehter (getwisteter) Doppelsättel ähnelten. Die Flächen der Kopfpositionen wiesen den deutlichsten Twist auf, die der Auge-im-Kopf Positionen waren nahezu eben und die Flächen der Blickpositionen zeigten einen mittleren Twist. Die Standardabweichung der Torsionsresiduen der genäherten Flächen (Torsionsdicke) war größer für den Blick als für das Auge und am kleinsten für den Kopf. Kopf- und Augentorsion, gemittelt über die Einzelfixationen, waren für jeden einzelnen Probanden unterschiedlich korreliert; über alle Probanden ergab sich jedoch keine signifikante Korrelation. Zusammenfassend unterschieden sich weder Flächenform noch Torsionsdicke von Blick, Kopf oder Auge zwischen den beiden Bedingungen (Star/ Diamond). Damit ist zum ersten Mal gezeigt, dass Donders' Law für Blick-, Kopf- und Augenpositionen unabhängig von der Richtung der vorangegangenen Sakkade gilt. Die fehlende Korrelation der Kopf- und Augentorsion ist auf eine unabhängige Kontrolle von Kopf- und Augenbewegungen zurückzuführen. Dies ist ein neues, weiteres Argument zur Bestätigung aktueller Modelle der neuronalen Kontrolle von Blickbewegungen, die von der Annahme unabhängiger Kopf- und Augencontroller ausgehen. Studien mit Patienten, die Läsionen in möglichen Zielstrukturen für solche neuronalen Controller tragen, sind zur weiteren Untersuchung dieser Modelle nötig. Abschließend ergibt sich klinisch-diagnostische Relevanz der Arbeit aus dem Vergleich mit Studiendaten zur Blickkoordination nach Mittelhirnläsionen, bei denen Patienten eine veränderte Form von Donders' Law aufweisen.
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Gaymard, Bertrand. "Controle cerebral de l'amplitude des saccades." Paris 6, 1995. http://www.theses.fr/1995PA066604.
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Les etapes cerebrales de l'elaboration du signal qui specifie l'amplitude d'une saccade sont passees en revue, ainsi que les travaux que nous avons realise et s'y rapportant. La premiere etape comprend des mecanismes de perception et d'attention visuelles. La deuxieme etape est sensori-motrice et a lieu dans les aires oculomotrices corticales. C'est la qu'ont lieu les changements de coordonnees qui assurent un codage precis de la saccade. Nous avons demontre (etudes 1 et 2) que l'aire oculomotrice frontale (fef) code la position d'une cible dans un systeme de coordonnees retiniennes, alors que l'aire oculomotrice supplementaire et le cortex vestibulaire utilisent un systeme de coordonnees spatiales. Nous avons demontre (etudes 3 et 4) que le fef est implique dans le controle des saccades volontaires, predites ou memorisees. La troisieme etape est la transmission du signal moteur au colliculus et au cervelet. Nous avons demontre que le signal visuel (etude 5) est utilise pour ajuster la precision de la saccade. La quatrieme etape est la transmission du signal moteur aux structures premotrices. Nous avons demontre (etude 6) que la proprioception oculaire intervient dans le maintien de la conjugaison oculaire. La cinquieme etape declenche une eventuelle saccade de correction. Elle utilise pour cela la decharge corollaire, dont la precision met en jeu des mecanismes de calibrage. Nous avons demontre (etude 6) que le thalamus joue un role essentiel dans ces mecanismes. Nous avons etudie la contribution du fef et du cervelet au systeme de detection d'erreur
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Ohl, Sven. "Small eye movements during fixation : the case of postsaccadic fixation and preparatory influences." Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2014/6986/.
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Describing human eye movement behavior as an alternating sequence of saccades and fixations turns out to be an oversimplification because the eyes continue to move during fixation. Small-amplitude saccades (e.g., microsaccades) are typically observed 1-2 times per second during fixation.
Research on microsaccades came in two waves. Early studies on microsaccades were dominated by the question whether microsaccades affect visual perception, and by studies on the role of microsaccades in the process of fixation control. The lack of evidence for a unique role of microsaccades led to a very critical view on the importance of microsaccades.
Over the last years, microsaccades moved into focus again, revealing many interactions with perception, oculomotor control and cognition, as well as intriguing new insights into the neurophysiological implementation of microsaccades.
In contrast to early studies on microsaccades, recent findings on microsaccades were accompanied by the development of models of microsaccade generation. While the exact generating mechanisms vary between the models, they still share the assumption that microsaccades are generated in a topographically organized saccade motor map that includes a representation for small-amplitude saccades in the center of the map (with its neurophysiological implementation in the rostral pole of the superior colliculus).
In the present thesis I criticize that models of microsaccade generation are exclusively based on results obtained during prolonged presaccadic fixation. I argue that microsaccades should also be studied in a more natural situation, namely the fixation following large saccadic eye movements. Studying postsaccadic fixation offers a new window to falsify models that aim to account for the generation of small eye movements. I demonstrate that error signals (visual and extra-retinal), as well as non-error signals like target eccentricity influence the characteristics of small-amplitude eye movements.
These findings require a modification of a model introduced by Rolfs, Kliegl and Engbert (2008) in order to account for the generation of small-amplitude saccades during postsaccadic fixation. Moreover, I present a promising type of survival analysis that allowed me to examine time-dependent influences on postsaccadic eye movements. In addition, I examined the interplay of postsaccadic eye movements and postsaccadic location judgments, highlighting the need to include postsaccadic eye movements as covariate in the analyses of location judgments in the presented paradigm.
In a second goal, I tested model predictions concerning preparatory influences on microsaccade generation during presaccadic fixation. The observation, that the preparatory set significantly influenced microsaccade rate, supports the critical model assumption that increased fixation-related activity results in a larger number of microsaccades.
In the present thesis I present important influences on the generation of small-amplitude saccades during fixation. These eye movements constitute a rich oculomotor behavior which still poses many research questions. Certainly, small-amplitude saccades represent an interesting source of information and will continue to influence future studies on perception and cognition.Die Beschreibung des Blickbewegungsverhaltens als eine sich abwechselnde Folge von Sakkaden und Fixationen stellt eine starke Vereinfachung dar, denn auch während einer Fixation bewegen sich die Augen. Typischerweise treten Bewegungen von kleiner Amplitude (z.B. Mikrosakkaden), 1-2 mal pro Sekunde während einer Fixation auf. Frühe Studien zu Mikrosakkaden wurden von Fragen bezüglich des Einflusses von Mikrosakkaden auf die visuelle Wahrnehmung, und Studien zu der Rolle von Mikrosakkaden bei der Fixationskontrolle dominiert. Fehlende Evidenz für eine Rolle, die ausschließlich Mikrosakkaden zufällt, führten zu einer sehr kritischen Betrachtung von Mikrosakkaden. In den letzten Jahren rückten Mikrosakkaden wieder mehr in den Fokus. Vielerlei Zusammenhänge mit Wahrnehmung, okulomotorischer Kontrolle und Kognition, sowie neue Erkenntnisse bezüglich der neurophysiologischen Implementierung von Mikrosakkaden konnten aufgedeckt werden. In den letzten Jahren wurden verschiedene Modelle der Mikrosakkadengenerierung vorgestellt. Auch wenn sich diese in ihren exakten Mechanismen unterscheiden, so teilen sie doch die Annahme, dass Mikrosakkaden in einer topographisch organisierten motorischen Karte für Sakkaden ausgelöst werden. Diese Karten beinhalten eine Repräsentation für klein-amplitudige Sakkaden im Zentrum der Karte (mit dem rostralen Pol der colliculi superiores als neurophysiologische Implementierung). In der vorliegenden Arbeit kritisiere ich, dass Modelle der Mikrosakkadengenerierung ausschließlich auf Resultaten langanhaltender präsakkadischer Fixation beruhen. Ich führe an, dass Mikrosakkaden in einer natürlicheren Situation untersucht werden sollten, nämlich während der Fixation nach einer großen Sakkade. Die Untersuchung postsakkadischer Fixation bietet eine neue Möglichkeit Modelle der Mikrosakkadengenerierung zu falsifizieren. In den Studien zeige ich, dass Signale über den Fehler in der Sakkadenlandeposition (visuelle und extra-retinale), sowie fehler-unabhängige Signale, wie die Zielreiz-Exzentrizität, einen entscheidenden Einfluss auf kleine Sakkaden haben. Diese Resultate erfordern Modifikationen an dem kürzlich eingeführten Modell von Rolfs, Kliegl und Engbert (2008), um die Generierung von kleinen Sakkaden auch während der postsakkadischen Fixation erklären zu können. Darüber hinaus präsentiere ich eine viel versprechende Ereigniszeitanalyse, die uns erlaubt zeitabhängige Einflüsse auf das postsakkadische Blickbewegungsverhalten zu untersuchen. Außerdem untersuche ich das Zusammenspiel von postsakkadischen Augenbewegungen und postsakkadischen Positionsurteilen. Dabei wird die Bedeutung von postsakkadischen Augenbewegungen als Kovariate in den statistischen Analysen betont. Ein zweites Ziel dieser Arbeit besteht darin Modellvorhersagen bezüglich vorbereitender Einflüsse auf die Mikrosakkadengenerierung zu untersuchen. Die Ergebnisse, hinsichtlich eines signifikanten Einflusses des preparatory set auf die Mikrosakkadenrate unterstützt die wesentliche Modellannahme, dass erhöhte fixationsbezogene Aktivität zu einer größeren Anzahl an Mikrosakkaden führt. In der vorliegenden Arbeit präsentiere ich wichtige Einflüsse auf die Generierung von kleinen Sakkaden während der Fixation. Diese Augenbewegungen stellen ein vielseitiges okulomorisches Verhalten dar, welche weiterhin zahlreiche Fragen mit sich bringen und sicherlich zukünftige Studien zu Wahrnehmung und Kognition beeinflussen werden.
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Laidlaw, Kaitlin Elizabeth Wiggins. "Greater distractor interference during vertical saccades : the time course of horizontal, vertical, and oblique saccadic curvature." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/27270.
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In three studies, we characterize the effect of a nearby distractor on vertical, horizontal and oblique saccadic curvature under normal saccade preparation times. In Experiments 1 and 2, participants made saccades to targets in the presence or absence of a nearby distractor. Consistent with previous findings, longer-latency vertical saccades showed greater curvature away from a distractor than did oblique or horizontal saccades. At short latencies, vertical saccades showed greater curvature towards the distractor. We propose that vertical saccades may be prone to greater distractor interference due to the superior colliculus, a midbrain region implicated in attentional and saccadic shifts, under-representing vertical target objects, which results in a relative over-representation of non-vertical distractor objects. In Experiment 3, we tested this hypothesis by having participants make saccades to vertical or horizontal targets in the presence or absence of bright or dim distractors. We reasoned that weaker representations for vertical targets would allow for greater interference from nearby distractors, which would be especially pronounced when distractors are highly salient. Consistent with this prediction, we found that only the trajectory of vertical saccades was modulated by distractor luminance.
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Savina, Olga. "Effects of training to an area-cue on human saccadic eye movements." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100209.
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Several recent studies have investigated advanced preparation of oculomotor programs after training to make saccades to a specific location in space. However, in natural visual scenes, we seldom know the precise stimulus location, rather, we often know the general area where target of interest may appear. Here, we investigated how human saccadic reaction time (SRT) and saccade final landing position may be affected by training to attend to an area where a target will appear. Additionally, we looked at how training to an area of one size may influence eye movements to targets presented in a larger area. Subjects were trained to attend to an area-cue of 6° in diameter, always presented in the same quadrant of the visual field, at the same spatial coordinates. During training, targets were presented at random locations inside the cued area. After training, targets were presented inside an area-cue (except for a few catch trials) of either the same size or of a larger size (i.e. 10° diameter). Results show that training-related saccades were directed toward individually distinctive preferred regions inside the trained area, and towards identical regions in relative coordinates inside the larger 10° area. Importantly, training-related saccades were mostly in the anticipatory range, a large proportion of which was followed by the corrective second saccades directed towards the target. Our findings suggest that anticipatory saccades should be considered in the assessment of training-related changes in oculomotor preparation of saccadic programming.
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Jones, Garrett L. "Noisy optimal control strategies for modelling saccades." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/39845.
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Eye movements have for a while provided us a closer view into how the brain commands the body. Particularly interesting are saccades: fast and accurate eye movements that allow us to scan our visual surroundings. One observation is that motor commands issued by the brain are corrupted by a signal-dependent noise. Moreover, the variance of the signal scales linearly with the control signal squared. It is assumed that such uncertainty in the dynamics introduces a probability distribution of the eye that the brain accounts for during motion planning.
We propose a framework for computing the optimal control law for arbitrary dynamical systems, subject to noise, and where the cost function depends on a statistical distribution of the eye’s position. A key contribution of this framework is estimating the endpoint distribution of the plant using Monte Carlo sampling, which is done efficiently using commodity graphics hardware in parallel. We then describe a modified form of gradient descent for computing the optimal control law for an objective function prone to stochastic effects. We compare our approach to other methods, such as downhill simplex and Covariance-Matrix-Adaptation, which are considered “gradient-free” approaches to optimization. We finally conclude with several examples that show the framework successfully controlling saccades for different plant models of the oculomotor system: this includes a 3D torque-based model of the eye, and a a nonlinear model of the muscle actuator that drives the eye.
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Griffiths, Helen Jane. "Saccades in the absence of binocular vision." Thesis, University of Sheffield, 2003. http://etheses.whiterose.ac.uk/3031/.
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The mechanism of suppression in strabismus is unclear and contribution of the suppressing eye to the generation of eye movements has received little attention. A series of nine experiments tested how the strabismic eye contributes to saccade generation in the presence of suppression and also considered the effect of the strabismic eye in the presence of abnormal retinal correspondence (ARC). These data were compared with data from subjects with normal binocular single vision (BSV). Chapters 2 and 3 describe the equipment, laboratory set-up and testing of the equipment used in the thesis for measuring eye movements, Skalar IRIS 6500 infrared limbal tracker, and presenting stimuli to each eye separately. The design of a novel method for dissociation of the eyes using four liquid crystal polymer shutters is presented. Chapter 4 compares the characteristics of saccades made by subjects with normal BSV (n=5) and strabismus (n=8). The effect of distractors on saccades is explored in Chapter 5 in subjects with normal BSV (n=5). The experiment documents the distractor effect produced in the described laboratory set-up, and compares it with that previously reported by Walker et al (1997). This is investigated further by comparing the effect of distractor presentations to the dominant eye, non-dominant eye or both eyes. There was no difference in the effect on saccade latency or gain with distractors presented to the dominant or non-dominant eye. The effect of binocular distractors on saccade gain was greater than monocular presentations. Chapter 6 repeats the experiment of Chapter 5 in subjects with constant strabismus and suppression (n=6) and constant strabismus with ARC (n=2) and found that distractors in the strabismic eye did affect saccades however the response differed from normal BSV. This was true even though it was shown that the distractor was not perceived by the strabismic eye. Chapter 7 investigates the influence of the central fixation target in the strabismic eye on saccade generation by inducing disconjugate saccade adaptation in subjects with normal BSV (n=8) and constant strabismus and suppression (n=6). The findings were that in the presence of suppression, disconjugate adaptation similar to that in normal BSV was possible. The conclusion of this thesis is to suggest that information from the suppressed eye is available to the saccadic system by either a sub-cortical pathway or processed cortically without conscious awareness.
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Zhang, Xiaoli. "Visuospatial information: integrating and updating across saccades." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587561006883305.
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Lévy-Bencheton, Delphine. "Perception visuelle et plasticité oculomotrice : aspects fondamentaux et application clinique." Phd thesis, Université Claude Bernard - Lyon I, 2013. http://tel.archives-ouvertes.fr/tel-00926062.
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Une façon d'explorer visuellement notre monde consiste à déplacer très rapidement nos yeux pour en analyser le contenu. Dans certaines circonstances, ces mouvements oculaires, appelés saccades, peuvent perdre de leur précision. Fort heureusement notre cerveau est capable de corriger cette imprécision en ajustant progressivement la taille de ces saccades grâce à des mécanismes de plasticité cérébrale : c'est l'adaptation saccadique. L'adaptation saccadique est souvent utilisée comme modèle d'étude des mécanismes de plasticité visuo-motrice. Nous faisons également l'hypothèse qu'elle puisse servir d'outil thérapeutique. Dans cette thèse, nous nous sommes essentiellement intéressés à l'adaptation des saccades volontaires en augmentation d'amplitude chez des sujets contrôles et chez des patients souffrant d'une amputation homonyme du champ visuel (hémianopsie latérale homonyme). Les expériences 1 à 3, réalisées chez le sujet contrôle, ont permis de découvrir les repères utilisés par le cerveau pour réaliser cette adaptation sensori-motrice et coder l'environnement visuel (expérience 1), et les mécanismes d'adaptation saccadique quand la cible visuelle n'est pas directement codée (remapping dans l'expérience 2 et cible virtuelle dans l'expérience 3). Enfin l'expérience 4 propose une application clinique du protocole d'adaptation des anti-saccades utilisé lors de l'expérience 3, dans un but thérapeutique de rééducation comportementale de patients hémianopsiques.
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Casana-Perez, Susana Maria. "Control of attention before reflexive and intentional saccades." Diss., lmu, 2004. http://nbn-resolving.de/urn:nbn:de:bvb:19-27083.
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Klier, Eliana Mira. "Three-dimensional visual-motor geometry of human saccades." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ27359.pdf.
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Casaña, Pérez Susana Maria. "Control of attention before reflexive and intentional saccades." kostenfrei, 2004. http://edoc.ub.uni-muenchen.de/archive/00002708/.
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Taylor, Kathleen. "Computational modelling of the contribution of posterior parietal cortex to saccadic eye movements." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302125.
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Edwards, Grace. "Predictive feedback to the primary visual cortex during saccades." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5861/.
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Perception of our sensory environment is actively constructed from sensory input and prior expectations. These expectations are created from knowledge of the world through semantic memories, spatial and temporal contexts, and learning. Multiple frameworks have been created to conceptualise this active perception, these frameworks will be further referred to as inference models. There are three elements of inference models which have prevailed in these frameworks. Firstly, the presence of internal generative models for the visual environment, secondly feedback connections which project prediction signals of the model to lower cortical processing areas to interact with sensory input, and thirdly prediction errors which are produced when the sensory input is not predicted by feedback signals. The prediction errors are thought to be fed-forward to update the generative models. These elements enable hypothesis driven testing of active perception. In vision, error signals have been found in the primary visual cortex (V1). V1 is organised retinotopically; the structure of sensory stimulus that enters through the retina is retained within V1. A semblance of that structure exists in feedback predictive signals and error signal production. The feedback predictions interact with the retinotopically specific sensory input which can result in error signal production within that region. Due to the nature of vision, we rapidly sample our visual environment using ballistic eye-movements called saccades. Therefore, input to V1 is updated about three times per second. One assumption of active perception frameworks is that predictive signals can update to new retinotopic locations of V1 with sensory input. This thesis investigates the ability of active perception to redirect predictive signals to new retinotopic locations with saccades. The aim of the thesis is to provide evidence of the relevance of generative models in a more naturalistic viewing paradigm (i.e. across saccades). An introduction into active visual perception is provided in Chapter 1. Structural connections and functional feedback to V1 are described at a global level and at the level of cortical layers. The role of feedback connections to V1 is then discussed in the light of current models, which hones in on inference models of perception. The elements of inferential models are introduced including internal generative models, predictive feedback, and error signal production. The assumption of predictive feedback relocation in V1 with saccades is highlighted alongside the effects of saccades within the early visual system, which leads to the motivation and introduction of the research chapters. A psychophysical study is presented in Chapter 2 which provides evidence for the transference of predictive signals across saccades. An internal model of spatiotemporal motion was created using an illusion of motion. The perception of illusory motion signifies the engagement of an internal model as a moving token is internally constructed from the sensory input. The model was tested by presenting in-time (predictable) and out-of-time (unpredictable) targets on the trace of perceived motion. Saccades were initiated across the illusion every three seconds to cause a relocation of predictive feedback. Predictable in-time targets were better detected than the unpredictable out-of-time targets. Importantly, the detection advantage for in-time targets was found 50 – 100 ms after saccade indicating transference of predictive signals across saccade. Evidence for the transfer of spatiotemporally predictive feedback across saccade was supported by the fMRI study presented in Chapter 3. Previous studies have demonstrated an increased activity when processing unpredicted visual stimulation in V1. This activity increase has been related to error signal production as the input was not predicted via feedback signals. In Chapter 3, the motion illusion paradigm used in Chapter 2 was redesigned to be compatible with brain activation analysis. The internal model of motion was created prior to saccade and tested at a post-saccadic retinotopic region of V1. An increased activation was found for spatiotemporally unpredictable stimuli directly after eye-movement, indicating the predictive feedback was projected to the new retinotopic region with saccade. An fMRI experiment was conducted in Chapter 4 to demonstrate that predictive feedback relocation was not limited to motion processing in the dorsal stream. This was achieved by using natural scene images which are known to incorporate ventral stream processing. Multivariate analysis was performed to determine if feedback signals pertaining to natural scenes could relocate to new retinotopic eye-movements with saccade. The predictive characteristic of feedback was also tested by changing the image content across eye-movements to determine if an error signal was produced due to the unexpected post-saccadic sensory input. Predictive feedback was found to interact with the images presented post-saccade, indicating that feedback relocated with saccade. The predictive feedback was thought to contain contextual information related to the image processed prior to saccade. These three chapters provide evidence for inference models contributing to visual perception during more naturalistic viewing conditions (i.e. across saccades). These findings are summarised in Chapter 5 in relation to inference model frameworks, transsacadic perception, and attention. The discussion focuses on the interaction of internal generative models and trans-saccadic perception in the aim of highlighting several consistencies between the two cognitive processes.
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Habchi, Ouazna. "Saccades oculaires, adaptation sensori-motrice et attention visuo-spatiale." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10328/document.
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L'interaction des individus avec l'environnement statique ou dynamique nécessite une exploration détaillée et précise des objets. Pour cela, notre système oculomoteur produit des mouvements oculaires rapides et précis appelés « saccades » afin de ramener l’image des objets d’intérêt sur la petite zone centrale de notre rétine (fovéa). Toutefois, notre système oculomoteur est fréquemment exposé à des perturbations physiologiques ou pathologiques. Ces changements sont contrôlés en permanence par des processus sensori moteurs basés sur la plasticité neuronale et appelés adaptation saccadique. L’objectif de mes travaux de thèse est de mieux comprendre les caractéristiques de cette adaptation et sa rétention à long terme mais aussi les réseaux impliqués dans l’adaptation saccadique. Comme les saccades oculaires ont un lien étroit avec l’attention visuo-spatiale, notre intérêt s’est également porté sur les interactions qui peuvent exister avec les réseaux impliqués dans le contrôle de l’attention visuo-spatiale. Un des principaux résultats est que l’orientation de l’attention exogène covert -sans bouger les yeuxdans des taches de détection et de discrimination est améliorée après l’adaptation des saccades réactives. Ces données fondamentales pourraient mener au développement de nouvelles méthodes de rééducation des déficits visuo-attentionnelsThe interaction of human beings with their static or dynamic environment requires detailed and precise exploration of objects. For this, our oculomotor system produces fast and accurate eye movements called "saccades" to bring the image of objects of interest on the small central area of the retina (fovea). However, our oculomotor system is frequently exposed to physiological or pathological disturbances. These changes are continuously monitored by sensorimotor processes based on neuronal plasticity and called "saccadic adaptation". The aim of my thesis is to better understand the characteristics of this adaptation and its long-term retention but also the neural networks involved in saccadic adaptation. As saccadic eye movements are closely related to visuo-spatial attention our work has also addressed the interactions that may exist with the networks involved in the control of visuo-spatial attention. A major result revealed that the orientation of the 'covert' exogenous attention -without moving the eyes- in detection and discrimination tasks is improved after adaptation of reactive saccades. These basic data could give rise to the development of new rehabilitation methods in visual-attention deficits
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Hopp, J. Johanna. "Localizing adaptation in the human saccadic system /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/10559.
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Diamond, Mark R. "The effect of saccades on visual sensitivity and time perception /." Connect to this title, 2002. http://theses.library.uwa.edu.au/adt-WU2003.0038.
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Sylvestre, Pierre Alexandre. "A new view of the saccadic burst generator : the coordination of multiple effectors during disjunctive saccades and eye-head gaze shifts." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84848.
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The neuronal system that generates saccadic eye movements has been well studied over the last three decades. However, this system has been extensively characterized only in the simplified case where the head is kept immobile, and the two eyes rotate identically (conjugate saccades). In everyday life, we often need to rotate our eyes differently when looking between objects located at different depths (disjunctive saccades), and we often utilize eye and head movements to reorient to objects of interest (gaze shifts). In the present thesis, we describe a series of experiments that were aimed at determining the role of the brainstem saccadic burst generator, a key element of the saccadic subsystem, during these more complex movements.With respect to disjunctive saccades, a very influential theory (Hering's theory) was proposed a century ago in which the brainstem saccadic burst generator [including excitatory (EBN) and inhibitory (IBN) brainstem saccadic burst neurons, and omnipause (OPN) neurons], and burst-tonic neurons (BT) only encode conjugate saccades. Here, we clearly demonstrate that this theory does not apply during disjunctive saccades. We have found that the discharge dynamics of the premotor neurons described above reflect the asymmetry in eye movements that is characteristic of disjunctive saccades. Moreover, we show that these signals are sufficient to shape the activity of motoneurons in the abducens nucleus.
We also demonstrate that during eye-head gaze shifts, the same EBNs, IBNs and OPNs encode the movements of the head as well as those of the eyes. To do so, we designed a sophisticated paradigm in which head movements could be perturbed during gaze shifts, while we simultaneously recorded the activity of isolated neurons. This highly challenging experiment has allowed us to conclusively demonstrate that neuronal activity with the brainstem saccadic burst generator reflects the artificial perturbations applied to the head.
In summary, the studies described in this thesis have unmasked a new role for the brainstem saccadic burst generator in the generation of disjunctive saccades. They have also confirmed its role in the control of eye-head gaze shifts. We conclude that the brainstem saccadic burst generator does far more than generating conjugate saccades, and that it is in fact involved in controlling the movements of the two eyes in space.
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Rolfs, Martin, Jochen Laubrock, and Reinhold Kliegl. "Shortening and Prolongation of Saccade Latencies Following Microsaccades." Universität Potsdam, 2006. http://opus.kobv.de/ubp/volltexte/2011/5701/.
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When the eyes fixate at a point in a visual scene, small saccades rapidly shift the image on the retina. The effect of these microsaccades on the latency of subsequent large-scale saccades may be twofold. First, microsaccades are associated with an enhancement of visual perception. Their occurrence during saccade target perception should, thus, decrease saccade latencies. On the
other hand, microsaccades likely indicate activity in fixation-related oculomotor neurons. These represent competitors to saccade-related cells in the interplay of gaze holding and shifting. Consequently, an increase in saccade latencies after microsaccades would be expected. Here, we present evidence for both aspects of microsaccadic impact on saccade latency. In a delayed
response task, participants made saccades to visible or memorized targets. First, microsaccade occurrence up to 50 ms before target disappearance correlated with 18 ms (or 8%) faster saccades to memorized targets. Second, if microsaccades occurred shortly (i.e., < 150 ms) before a saccade was required, saccadic reaction times in visual and memory trials were increased by about 40 ms (or 16%). Hence, microsaccades can have opposite consequences for saccade latencies, pointing at a differential role of these fixational eye movements in preparation of motor programs.
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Lünenburger, Lars. "Influence of arm movements on saccades Einfluss von Armbewegungen auf Sakkaden /." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965163016.
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Bender, John Andrew Laurent Gilles Dickinson Michael. "Elements of feed-forward and feedback control in Drosophila body saccades /." Diss., Pasadena, Calif. : California Institute of Technology, 2007. http://resolver.caltech.edu/CaltechETD:etd-03042007-163003.
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Träisk, Frank. "Evaluation of the infrared reflection method for saccadic eye movement velocity analysis /." Stockholm, 2006. http://diss.kib.ki.se/2006/91-7140-609-3/.
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Gaertner, Chrystal. "Développement des saccades verticales et de la posture en interaction avec la vergence chez des enfants sains de 6 à 17 ans et chez des enfants avec strabisme." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066099.
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Les saccades verticales sont importantes pour l'exploration du monde visuel 3D. Ces mouvements complexes nécessitent le contrôle de la distribution d'innervation aux six muscles extraoculaires de chaque ¿il. Peu d'études existent chez quelques adultes. Elles montrent une asymétrie haut/bas : latence plus courte pour les saccades vers le haut, convergence pendant les saccades vers le bas et divergence pendant les saccades vers le haut. Une controverse persiste concernant l'origine centrale versus musculaire de la vergence. Cette thèse apporte des données de référence sur le développement des saccades verticales en interaction avec la vergence chez des enfants de 6 à 17 ans. Le résultat marquant est une convergence pendant toutes les saccades verticales qui diminue avec l'âge pour les saccades vers le haut, tendant vers la divergence de l'adulte. Ainsi, les asymétries haut/bas évoluent avec l'âge ; nos résultas plaident en faveur d'une synergie continue saccade-vergence qui soutiendrait un biais perceptif (champ visuel haut perçu comme plus lointain en profondeur que le champ visuel bas). Cette thèse étudie aussi le contrôle postural, focalisant sur l'interaction vision-oculomotricité-posture des enfants de 6 à 17 ans sains et des enfants avec strabisme. Les résultats montrent un effet stabilisateur de la vergence sur la posture, l'existence d'un espace privilégié pour la stabilité posturale (lointain pour strabismes divergents, mais proche pour strabismes convergents et enfants sains) et un bénéfice de la vision bi-oculaire rudimentaire présente chez des strabiques. Cette thèse ouvre des pistes multiples de recherche fondamentale en cliniqueVertical saccades eye movements are very important for exploration of the 3-D space. There are complex movements, requiring control of the distribution of innervation to the six extraocular muscles of each eye. Few studies exist in some adults subjects. These showed up/down anisotropies: shorter latency for upward saccades, convergence during downward and divergence during upward saccades. A controversy remains about the origin, central versus muscular, of the vergence. This thesis provides referential developmental data of vertical saccades in interaction with vergence in children from 6 to 17 years. The striking result is a convergence of the eyes during all vertical saccades that decrease with age for upward saccades, tending towards divergence like adults. Thus up/down asymmetries changed with age, in line with a continuous saccade-vergence synergy that supports a perceptual bias (upper visual field further away in depth than lower visual field). This thesis studied also postural control, focusing on the vision-oculomotricity-posture interaction in children from 6 to 17 years old, and in children with strabismus. Our results showed a stabilizing effect of vergence on posture, the existence of a favorite space for postural stability in strabismic children (near for convergent and healthy children and far for divergent strabismus) and a benefit of bi-ocular visual stimulation. This thesis opens multiple avenues for fundamental research in clinic
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Blum, Bernhard M. [Verfasser], and Ulrich [Akademischer Betreuer] Büttner. "Torsional control of eye-head saccades / Bernhard M. Blum. Betreuer: Ulrich Büttner." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2013. http://d-nb.info/1065611145/34.
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Tremblay, Alain Roland. "Interactions between natural and electrically-evoked saccades in the head-free cat." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=26160.
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Fixed-vector saccades obtained upon electrical stimulation--while the eyes are steady--of any central oculomotor system structure can be derived from 2 different signals: (1) a retinal error signal, directing the eyes toward a specific location relative to the retina; (2) a motor error signal determining the movement vector itself. Theoretically, the two mechanisms can be segregated by delivering the stimulation during a naturally-triggered saccade (colliding saccade paradigm, Schlag-Rey et al., 1989), thereby creating a difference between the eyes' position at stimulation onset and their position at saccade outset. If derived from a retinal error signal, the electrically-evoked vector trajectory should be modified to compensate for the intervening change in eye position. If the saccade is derived from a motor error signal, the vector trajectory should be the same as when stimulating the same site while the eyes are immobile. This study describes the results of the application of the collision test in conjunction with the stimulation of 16 sites throughout the Superior Colliculus of 3 head-free cats. The main result of these tests--whether applied in conjunction with stimulation of superficial (where cells have visual activity) or deeper layers (where cells have motor activity) sites--is an absence of compensation indicating that the gaze saccades were derived from a motor error signal. Compensating saccades were only found in 6% of the cases with superficial layer stimulation sites while they were found in about 12% of the cases with deeper layer sites.
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Etchells, Peter James. "The need for speed : target velocity integration in saccades to moving tatgets." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.535172.
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Mezey, Laura Elisabeth. "The adaptive control of saccades in normal and abnormal children and adults." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343722.
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Grosbras, Marie-Hélène. "Controle cortical des saccades volontaires : etudes par neuro-imagerie fonctionnelle chez l'homme." Paris 6, 2001. http://www.theses.fr/2001PA066112.
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Nous nous sommes interesses aux bases neurales des saccades oculaires volontaires chez l'homme sain. Notre perspective considere l'execution de saccades comme partie d'un comportement necessitant un controle de haut niveau pour la selection spatiale, la decision et l'integration perception-action. Nous avons dans un premier temps identifie et localise chez l'homme, a l'aide de l'imagerie fonctionnelle par resonance magnetique, le reseau cortical active lors de l'execution de saccades volontaires simples. Nous avons ensuite etudie avec la stimulation magnetique transcranienne, le role d'une composante majeure de ce reseau, le champ oculomoteur frontal, dans les deplacements de l'attention spatiale avec ou sans mouvements oculaires. Nous avons demontre que cette region est fondamentale non seulement pour la programmation oculomotrice, mais aussi pour la perception visuelle. Enfin nous avons etudie, pour la premiere fois a l'aide de l'imagerie cerebrale, les bases neurales de la capacite du systeme oculomoteur non seulement a organiser la strategie d'exploration en sequences saccade-fixation, mais aussi a apprendre des sequences utilisees pour l'exploration automatique. Nous avons ainsi montre que l'activation du circuit oculomoteur est plus importante pour l'execution de sequences nouvellement apprise que pour les sequences familieres et que chaque type de sequence active des regions specifiques. L'ensemble de ce travail contribue a mieux comprendre les reseaux corticaux en jeu dans l'execution de mouvements oculaires, et au-dela questionne l'organisation integree des systemes executif, perceptif et mnemonique pour la planification des comportements volontaires.
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Alahyane, Nadia. "Adaptation des saccades oculaires réactives et volontaires : propriétés fonctionnelles et substrats neuroanatomiques." Lyon 1, 2006. http://www.theses.fr/2006LYO10018.
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Notre travail concerne l'étude de l'adaptation des saccades oculaires réactives (SR) et des saccades volontaires d'exploration (SV) chez l'Homme sain et pathologique. En utilisant le protocole de cibles double-saut pour mimer l'adaptation saccadique, nous avons montré que selon le contexte (position verticale des yeux, mode de présentation de la cible), le système saccadique peut subir des changements d'amplitude adaptatifs spécifiques, persistant plusieurs jours. Nos données suggèrent de plus que l'adaptation des SV et des SR repose sur un site commun au niveau du tronc cérébral. Ce site serait modulé par un signal de correction délivré par le cervelet de façon adéquate suivant le contexte. Enfin, l'adaptation des SR, efficiente dès l'enfance, est préservée chez les enfants dyslexiques, rejetant l'hypothèse d'une anomalie du cervelet médio-postérieur dans la dyslexie. L'adaptation saccadique représente ainsi un bon modèle d'étude de la plasticité cérébrale et de diagnostic clinique
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Boudet, Claire. "Etude de la poursuite oculaire dans la schizophrénie." Caen, 2002. http://www.theses.fr/2002CAEN3077.
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Afin de vérifier si les altérations de la poursuite oculaire pourraient être des marqueurs de la vulnérabilité génétique de la schizophrénie, nous avons inclus des patients, des apparentés sains du premier degré et des témoins appariés. Ils ont été testés avec les paradigmes de saccades, d'antisaccades et de poursuite lente. Nous avons observé des altérations chez les patients, mais aucune chez les apparentés, ce qui ne nous permet pas de conclure que les troubles de la poursuite oculaire seraient des marqueurs de vulnérabilité génétique de cette pathologie. Lors de la poursuite lente d'un stimulus multifréquentiel, il intervient trois systèmes : poursuite lente, saccadique et prédictif (influence les deux autres). La comparaison de patients schizophrènes et de sujets sains ne nous a permis de mettre en évidence de différence entre ces deux groupes. Par conséquent, aucun des systèmes de poursuite oculaire ne semble altéré chez les patients par rapport aux sujets témoins.
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Soetedjo, Robijanto. "The role of the superior colliculus in the feedback control of saccadic eye movement in the rhesus monkey /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/8033.
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Jardine, Nicole. "Surface structure and saccadic control." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6147.
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Saccadic eye movements are guided by attention. Indeed, some saccade trajectory effects serve as an index the attentional strength of visual objects in the map of visual space used to plan a saccade. One approach to understanding saccade planning relies on simple tasks in sparse displays (containing a single target and distractor object) to develop neurophysiologically plausible models of saccade behavior. Under tightly controlled conditions, saccade trajectories can be well predicted by representing displays of objects with simple visual features and their relative salience.
But the world in which the saccade system typically operates is not sparse, and observer eye movements are guided by more than just salience. As such, another approach has been to examine saccadic behavior in complex scenes and complicated goals. Such scene context can drastically affect saccades in ways that are not well predicted by a context-free and expectation-free representation of visual salience.
This dissertation starts to bridge this gap between these literatures by focusing on object surfaces. Covert shifts of attention operate on representations informed not just by stimulus salience and location-based expectations, but also by the perceptual organization of object surfaces. Covert attention can be guided by surface context, such that targets and distractors are processed differently as a function of whether they are on the same or different surface. These effects are fragile, however, and have previously only been demonstrated in relatively engaging tasks and with strong perceptions of objecthood.
The present work tested the strength of the relationship between attention and saccades by testing whether surface context guides orienting eye movements. Observers made saccades to objects that could be organized with different surface structure. In four experiments (Chapters 2 and 3) I found no evidence that the saccade map encoded surface context. But in two experiments (Chapters 4 and 5) I demonstrate saccade trajectories are sensitive to surface context, independently of low or high task engagement. This demonstrates that object surface-based representations are not necessarily fragile and can affect the oculomotor map even for simple saccadic orienting for which the surface is task-irrelevant. This lends evidence to the theory that the nature of the representation of vision is one of object surfaces, and suggests that the strength of object encoding is stronger than has been previously demonstrated.
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Unsworth, David I. "Working memory capacity and the control of saccades : individual differences in executive control." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/30980.
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Nezzar, Hachemi. "Etude in vivo du connectome des saccades oculomotrices chez l'Homme par imagerie structurelle." Thesis, Clermont-Ferrand 1, 2016. http://www.theses.fr/2016CLF1MM15/document.
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Le système visuel humain est complexe par son organisation anatomique et par son fonctionnement incomplètement élucidé. Il est fonctionnellement divisé en deux systèmes. Le premier système est destiné à la vision consciente communément appelée voie visuelle principale ou en anglais « image forming visual pathways ». Le second, appelé système secondaire ou accessoire, n’apporte pas d’information visuelle consciente, il est dit « non image forming visual pathway ». Ce dernier apporte à notre cerveau une information sur l’environnement telle que la sensation jour/nuit. Ses fonctions sont sous-tendues par l’afflux d’informations rétiniennes non visuelles sur des structures de l’hypothalamus comme le noyau supra-chiasmatique. Les deux systèmes visuels ont un substratum anatomique complexe faisant intervenir de nombreuses structures anatomiques au sein des différents étages du cerveau cortical et sous-cortical comme les noyaux gris centraux dits « Basal Ganglias » (BG). Le système visuel secondaire intervient aussi comme une structure de contrôle des mouvements oculomoteurs tels que la poursuite ou les saccades nécessaires pour explorer notre environnement. Ainsi les saccades oculomotrices sont sous le contrôle modulateur des BG. De ce fait l’étude des saccades apparait comme un très bon modèle pour explorer le fonctionnement du système extrapyramidal au cours des maladies neuro-dégénératives. Les connaissances actuelles sur ce système de contrôle des saccades proviennent essentiellement des études sur le primate non humain et sur des observations cliniques chez l’homme au cours de pathologies dégénératives ou toxiques des BG. L’observation des structures anatomiques, en particulier du réseau de la substance blanche cérébrale qui supporte les connections axonales, n’est pas accessible à l’imagerie clinique de routine. Pour décrire et étudier ces réseaux de connections, la notion de connectomique a été introduite il y a un dizaine d’années. Dans ce travail, nous nous sommes donné l’objectif de décrire le connectome des saccades oculomotrices sur un plan structurel. Nous avons exploré les structures sous-corticales intervenant dans le contrôle des saccades comme les BG, le colliculus supérieur et le pulvinar. Pour ce faire, nous avons utilisé l’imagerie IRM structurelle en diffuseur de tension (DTI) chez deux groupes de patients présentant une maladie neuro-dégénérative : un groupe souffrant de maladie de Parkinson chez qui une atteinte des BG et une dysfonction des saccades sont reconnues, et un groupe de trembleurs essentiels reconnu pour ne pas présenter de dysfonction des saccades et chez qui les BG sont épargnés. Le résultat de ce travail a permis pour la première fois une description in vivo du connectome des saccades chez l’Homme. Il a de plus montré des différences dans la structure du connectome dans les deux groupes de patients. Une meilleure connaissance de ce connectome pourrait permettre de mieux comprendre certains troubles oculomoteurs et aussi de suivre l’évolution de certaines maladies neurodegenerativesVisual system is complex by its anatomy and its function. Neuro-anatomists have been interested in understanding the link between the visual pathways and the brain for centuries. Classical brain fixation and dissection methods were used to describe the visual pathways identifiable macroscopically. Non–image visual pathway, particularly the part involves in saccadic eye movements network in human is still not mastered. Our current knowledge in SCM is based on animal studies, anatomic dissection and brain histopathology examination of specimens from patients with clinical basal ganglia (BG) disorders. Saccadic eye movements (SCM) are under the control of the basal ganglia (BG) and SCM circuitry within the BG represents a good model for studying pathology in the extra-pyramidal system. The diagnosis of Parkinson’s disease (PD), which affects SEM and its distinction from non-dopaminergic, essential tremor (ET) where SEM are not impaired can be challenging and still relies on clinical observations. Diffusion tensor imaging and fiber tractography (DTI-FT), a new MRI technology, can be used to evaluate the presence and integrity of white matter tracts using directional diffusion patterns of water. The purpose of this study is to use DTI-FT to analyse SEM networks within BG and compare the SEM neural pathways or connectome of patients clinically diagnosed with PD and ET. To date, there are no studies, using DTI-FT for the extensive exploration of non-image visual pathways and SCM circuits, notably the deep brain connections. For this goal, we introduced the concept of SCM connectomes, derived from the general concept of connectome. Our study used structural MRI to identify nuclei and fascicles of the SCM connectome in PD and ET patients; imageries were acquired in routine clinical conditions fitted for DBS surgery. We found a reduction of the fiber number in two fascicles of the connectome in PDcompared to ET group
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RIVAUD, SOPHIE. "Effets des lesions corticales et sous-corticales sur les saccades oculaires chez l'homme." Paris 6, 1995. http://www.theses.fr/1995PA066451.
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Pour etudier le controle cortical oculomoteur chez l'homme, nous avons enregistre les saccades visuelles (sv) de patients ayant une lesion corticale, ne touchant que le champ oculomoteur parietal (cop), ou le champ oculomoteur frontal (cof), ou le cortex prefrontal (cpf), ou le champ oculomoteur supplementaire (cos), ou la region hippocampique (rh), ou le cortex vestibulaire (cv), ou le colliculus superieur (cs). Nous avons etudie, les mecanismes de declenchement, d'inhibition, d'utilisation de differents types de coordonnees pour calculer l'amplitude, et de memorisation apres stimulation visuelle ou vestibulaire des sv. Le cop faciliterait le declenchement des sv reflexes (svr), et serait plus implique dans l'integration visuo-motrice des coordonnees d'une cible visuelle que dans l'integration d'informations vestibulaires, le mecanisme inverse est observe dans le cv. Le cof participerait au declenchement des sv volontaires dont l'amplitude est determinee a partir de coordonnees retinotopiques. Le cos interviendrait quand les saccades sont effectuees a partir de coordonnees extraretiniennes. Le cpf controlerait l'inhibition des svr, et la memorisation a court terme d'informations visuelles et vestibulaires. La rh interviendrait pour la memorisation a long terme. Le cs participerait a l'inhibition des svr et au controle de l'amplitude des svr. Les anomalies des svr des syndromes parkinsoniens atypiques sont specifiques et permettent un diagnostic precoce. Les svr sont normales dans la maladie de parkinson. Dans la degenerescence cortico-basale un tres important ralentissement du declenchement des svr traduit un dysfonctionnement parietal. Dans la paralysie supranucleaire progressive, une diminution tres marque de l'amplitude des sv horizontales et un important deficit d'inhibition des svr, s'ajoute a une paralysie de la verticalite
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Choi, Eugénie. "Mouvements oculaires rapides : parametres de forme et modelisation de saccades de fixation calibrees." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13210.
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Choi, Eugénie. "Mouvements oculaires rapides paramètres de forme et modélisation de saccades de fixation calibrées /." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376127480.
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Pocius, Edgaras. "Įcentrinių ir išcentrinių žmogaus akies sakadų tyrimas." Bachelor's thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20140716_103003-70836.
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Bakalauro baigiamajame darbe tiriamas įcentrinių ir išcentrinių žmogaus akies sakadų tikslumas. Eksperimento metu, kompiuterio ekrane, horizontalia kryptimi per penkias fiksuotas padėtis, šuoline trajektorija judėjo žalias (0,25 laipsnio diametro) taškas. Tiriamųjų paprašyta žvilgsniu sekti šį tašką. Apdorojus gautus tyrimo duomenis pastebėta, kad tos pačios amplitudės įcentrinės sakados yra tikslesnės, nei išcentrinės.In this Bachelor thesis accuracy of the centripetal and centrifugal human eye saccades was studied. During the experiment, on the computer screen, in horizontal direction within five fixed positions, the hopping green spot (diameter of 0,25 degrees) was moving. Subjects were instructed to follow this green spot with gaze. Processing the research data reported that the centripetal saccades is more accurate than the centrifugal of the same amplitude.
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Thurtell, Matthew James. "Effect of eye position on the three-dimensional kinematics of saccadic and vestibular-evoked eye movements." Thesis, The University of Sydney, 2005. http://hdl.handle.net/2123/1665.
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Saccadic and vestibular-evoked eye movements are similar in that their three-dimensional kinematic properties show eye position-dependence. When the line of sight is directed towards an eccentric target, the eye velocity axis tilts in a manner that depends on the instantaneous position of the eye in the head, with the magnitude of tilt also depending on whether the eye movement is saccadic or vestibular-evoked. The mechanism responsible for producing eye velocity axis tilting phenomena is not well understood. Some authorities have suggested that muscle pulleys in the orbit are critical for implementing eye velocity axis tilting, while others have suggested that the cerebellum plays an important role. In the current study, three-dimensional eye and head rotation data were acquired, using the magnetic search coil technique, to confirm the presence of eye position-dependent eye velocity axis tilting during saccadic eye movements. Both normal humans and humans with cerebellar atrophy were studied. While the humans with cerebellar atrophy were noted to have abnormalities in the two-dimensional metrics and consistency of their saccadic eye movements, the eye position-dependent eye velocity axis tilts were similar to those observed in the normal subjects. A mathematical model of the human saccadic and vestibular systems was utilized to investigate the means by which these eye position-dependent properties may arise for both types of eye movement. The predictions of the saccadic model were compared with the saccadic data obtained in the current study, while the predictions of the vestibular model were compared with vestibular-evoked eye movement data obtained in a previous study. The results from the model simulations suggest that the muscle pulleys are responsible for bringing about eye position-dependent eye velocity axis tilting for both saccadic and vestibular-evoked eye movements, and that these phenomena are not centrally programmed.
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Thurtell, Matthew James. "Effect of eye position on the three-dimensional kinematics of saccadic and vestibular-evoked eye movements." Faculty of Medicine, 2005. http://hdl.handle.net/2123/1665.
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Master of Science in MedicineSaccadic and vestibular-evoked eye movements are similar in that their three-dimensional kinematic properties show eye position-dependence. When the line of sight is directed towards an eccentric target, the eye velocity axis tilts in a manner that depends on the instantaneous position of the eye in the head, with the magnitude of tilt also depending on whether the eye movement is saccadic or vestibular-evoked. The mechanism responsible for producing eye velocity axis tilting phenomena is not well understood. Some authorities have suggested that muscle pulleys in the orbit are critical for implementing eye velocity axis tilting, while others have suggested that the cerebellum plays an important role. In the current study, three-dimensional eye and head rotation data were acquired, using the magnetic search coil technique, to confirm the presence of eye position-dependent eye velocity axis tilting during saccadic eye movements. Both normal humans and humans with cerebellar atrophy were studied. While the humans with cerebellar atrophy were noted to have abnormalities in the two-dimensional metrics and consistency of their saccadic eye movements, the eye position-dependent eye velocity axis tilts were similar to those observed in the normal subjects. A mathematical model of the human saccadic and vestibular systems was utilized to investigate the means by which these eye position-dependent properties may arise for both types of eye movement. The predictions of the saccadic model were compared with the saccadic data obtained in the current study, while the predictions of the vestibular model were compared with vestibular-evoked eye movement data obtained in a previous study. The results from the model simulations suggest that the muscle pulleys are responsible for bringing about eye position-dependent eye velocity axis tilting for both saccadic and vestibular-evoked eye movements, and that these phenomena are not centrally programmed.
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Craig, Gregory L. "Inhibiting reflexive saccades to peripheral targets, effects of fixation offset on the gap effect." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ26850.pdf.
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Craig, Gregory (Gregory Lorne) Carleton University Dissertation Psychology. "Inhibiting reflexive saccades to peripheral targets; effects of fixation offset on the gap effect." Ottawa, 1997.
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Godijn, Richard. "Endogenous saccades are preceded by shifts of visual attention, evidence from a novel priming task." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0003/MQ46167.pdf.
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Harrison, James J. "Volition and automaticity in the interactions of optokinetic nystagmus, infantile nystagmus, saccades and smooth pursuit." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/59168/.
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Volitional target-selecting eye movements, such as saccades or smooth pursuit, are frequently considered distinct and separate from automatic gaze-stabilising eye movements like optokinetic nystagmus or the vestibulo-ocular reflex. This difference is regularly mapped onto brain anatomy, with distinctions made between subcortical, automatic processes; and cortical, volitional ones. However gaze-stabilising and target-selecting eye movements must work together when a moving observer views natural scenes. Yet such co-ordination would not be possible if automatic and volitional actions are sharply divided. This thesis focuses upon interactions between gaze-stabilising and target-selecting eye movements, and how these interactions can aid our understanding of the relationship between automatic and volitional processes. For a saccade executed during optokinetic nystagmus to accurately land on target, it must compensate for the ongoing optokinetic movement. It was found that targeting saccades can partially compensate for concomitant optokinetic nystagmus. The degree of compensation during optokinetic nystagmus was indistinguishable from compensation due to voluntary smooth pursuit displacements. A subsequent experiment found that locations are similarly misperceived during optokinetic nystagmus and smooth pursuit. Furthermore, saccade end-points are subject to the same perceptual mislocalisations. The next experiment established that fast-phases of optokinetic nystagmus can act like competitive saccades and cause curvature in targeting saccades. Moreover, optokinetic nystagmus fast-phases are delayed by irrelevant visual distractors in the same way as saccades (the saccadic inhibition effect). Lastly, it was established that the fast-phases of Infantile Nystagmus Syndrome also show the saccadic inhibition effect. In conclusion, target-selecting and gaze-stabilising eye movements show substantial co-ordination. Furthermore these results demonstrate considerable commonalties between ‘automatic’ and ‘volitional’ eye movements. Such commonalities provide further evidence there is no sharp distinction between automatic and volitional processes. Instead it is likely there are substantial interconnections between automatic and volitional mechanisms, and volition has a graded influence upon behaviour.
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Riska, Kristal M., Jordan Bellucci, Doug Garrison, and Courtney D. Hall. "Relationship Between Corrective Saccades and Measures of Physical Function in Unilateral and Bilateral Vestibular Loss." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/etsu-works/7782.
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Objectives:Following the loss of vestibular function, some patients functionally improve and are minimally bothered by their loss of peripheral function while others remain more symptomatic and are unable to return to their activities of daily living. To date, the mechanisms for functional improvement remain poorly understood. The purpose of the present study was to examine the association between corrective saccades and measures of handicap, dynamic visual acuity, gait, and falls.
Design:A retrospective chart review was performed to identify patients who were diagnosed with unilateral or bilateral vestibular hypofunction and who also completed a baseline vestibular rehabilitation evaluation. A total of 82 patients with unilateral vestibular hypofunction and 17 patients with bilateral vestibular hypofunction were identified. The video head impulse test results for each patient were grouped based on the type of presenting saccades. Specifically, the saccade grouping included the following: (1) covert, (2) overt, or (3) a combination of both types of saccades.
Results:The results show that covert saccades are associated with better performance on measures of dynamic visual acuity, gait, and balance in patients with unilateral vestibular hypofunction. Patients exhibiting overt saccades or combination of both covert and overt saccades were more often found to have an abnormal gait speed and be characterized as being at risk for falls using the Dynamic Gait Index. We observed no differences in physical function for those patients with bilateral vestibular hypofunction as a function of saccade grouping.
Conclusions:When comparing saccade groups (covert, overt, or combination of both), patients with unilateral vestibular hypofunction and covert saccades demonstrated better performance on standard baseline physical therapy measures of dynamic visual acuity and gait and balance. We did not observe any significant associations between saccade group and physical function in patients with bilateral vestibular hypofunction; however, additional studies are needed with adequate sample sizes. Our findings may suggest that corrective saccade latency in patients with unilateral vestibular hypofunction is related to measures of physical function. The extent to which saccade latency has the potential to be a useful target for vestibular rehabilitation is still to be determined and may be promising target to improve functional outcomes.
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Zhang, Xiaoli. "More than Relational Information in Space: The Role of Nontargets in Target Localization across Saccades." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1467892193.
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GRAIGNIC, GWENAELLE. "Saccades oculaires : de la modelisation aux tests cliniques integres dans un atelier d'aide au diagnostic." Université Louis Pasteur (Strasbourg) (1971-2008), 1995. http://www.theses.fr/1995STR13008.
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Afin d'etudier la dynamique des saccades de maniere quantitative en pratique clinique, j'ai realise un logiciel comprenant vingt tests, appuye sur la modelisation, a interface ergonomique. Ce logiciel s'inscrit dans le cadre d'un atelier d'aide au diagnostic instrumente du systeme humain de l'equilibre. La saccade y est etudiee en evaluant non seulement des parametres locaux, qui dependent de valeurs isolees, mais aussi des parametres globaux dependant de l'ensemble des points de la saccade et dont les fluctuations sont effectivement moindres. La methodologie experimentale utilisee vise a produire plusieurs saccades horizontales de la meme amplitude, plus ou moins excentrees, afin de pouvoir separer objectivement le signal du bruit par moyennage plutot que par filtrage. Les saccades oculaires provoquees par la presentation de cibles visuelles sont enregistrees par electro-oculographie bivoie chez vingt cinq sujets normaux afin d'une part, de valider le logiciel et d'autre part, d'etablir des references pour une future utilisation en pathologie. Deux modeles du generateur de saccades ont ete construits qui comportent un modele interne de l'oculomotricite fonde sur le principe d'une regulation d'etat appliquee a la representation de la plasticite neuro-mecanique du systeme oculomoteur. Les saccades simulees a l'aide de ces deux modeles, l'un avec un modele interne fonctionnant en boite noire et l'autre explicitant les variables d'etats du modele interne, ont ete comparees aux saccades experimentales. Cette comparaison est plutot en faveur du deuxieme modele