Dissertations / Theses: 'Eye Saccadic eye movements. Visual perception'

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Richard, Alby-Réal. "The interaction of visual perception and saccadic eye movements." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123018.

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Primates have evolved to make high velocity, ballistic eye movements called saccades approximately three to five times per second in order to orient the high resolution part of their retina, or fovea, towards objects of interest. While saccades are generally adaptive in most situations, they also present the brain with certain challenges in order maintain a stable perception of the world. With every movement of the visual axis involving the eyes alone or through a combined eye-head gaze shift, the retina is presented with a rapidly changing view of the world. Most observers are not aware of the actual flow of incoming retinal information during a saccade, and instead perceive the world as being stable from one gaze movement to the next. How the brain accomplishes this stability has been referred to as the problem of 'trans-saccadic' perceptual stability. While this problem been pondered for more than a century by philosophers, psychologists, and neuroscientists, there is still no consensus on the precise mechanism by which visual stability is achieved. One way to approach the problem of perceptual stability is to study the way in which visual perception changes around the time of saccades. It is well known that objects briefly presented around the time of saccadic eye movements are not perceived at their veridical location, a phenomenon called perisaccadic mislocalization. Most observers make errors of two types that are predictable and systematic: a translational shift in the direction of the saccade, and compression towards the target location. This later effect, the compression of visual space towards the saccade target, is the primary phenomenon through which this thesis sought to understand the mechanisms responsible for visual stability across saccades. To this end, a series of psychophysical experiments were conducted to explore which signals may be involved in computing where an object was in space around the time of a saccade. In the fist paper, we described a biological framework in which an oculomotor signal encoding the gaze command interacts with a visual signal encoding afferent information. The outcome of this interaction was related to the perceived position of the object presented around the time of the saccade, and this formulation was able to capture both our results in addition to data from outside our laboratory. After successfully modelling the compression effect within a plausible biological framework, the next paper focused on elucidating the nature of the oculomotor signal. We accomplished this by testing observers in a variety of conditions aimed to disambiguate whether the signal was encoding the eye movement alone or the eye-head gaze shift, and found that compression was indeed linked to the eye-head gaze shift. Moreover, the experiments performed allowed us to further describe the parameters involved in modulating the compression effect. With our understanding of the compression effect and the likely biological signals involved, we then used this model to gain an enhanced understanding of how perisaccadic visual perception may be altered in patients with schizophrenia. The final paper examines the postulate that patients with schizophrenia may have an altered corollary discharge signal in the visual pathway for saccadic eye movements. With this study we were able to show that these patients do in fact exhibit qualitative differences in mislocalization compared to controls, and that these are attributable to a noisy corollary discharge that encodes the eye's position in space. This thesis comprises a systematic overview of what signals are involved in maintaining perceptual stability across saccadic eye and head movements. We have been able to investigate these signals through a combination of psychophysical studies and computational modeling. Finally, we used these paradigms to understand how these signaling mechanisms are altered in patients with schizophrenia.
Au cours de l'évolution, les primates ont développé des mouvements oculaires rapides, ou les saccades. Bien que les saccades soient généralement une fonction adaptive, elles engendrent des défis important au près du système visuel qui cherche à maintenir une perception stable sur le monde. À chaque mouvement de l'axe visuel, que ce soit les yeux seuls ou la tête en combinaison avec les yeux, la rétine reçoit une nouvelle image du monde. La majorité des observateurs n'a pas conscience de ce flux important d'information rétinienne discontinue et perçoit plutôt un monde stable d'un regard à l'autre. Ce phénomène de consolidation de l'influx visuel saccadé en une perception stable et fluide du monde est intitulé le problème de la « perception stable trans-saccadique ». Le phénomène de la « perception stable trans-saccadique » peut être étudié par le biais d'une approche scientifique rigoureuse qui se penche sur la manière dont la perception visuelle évolue à travers les mouvements oculaires. Notamment, il a été démontré que les cibles présentées très brièvement lors d'un saccade sont perçu de façon erronée par rapport à leur emplacement spatial véridique, le phénomène des erreurs de localization peri-saccadique (ELPS). Ces erreurs prédictibles et systématiques sont de deux types : le premier est un simple déplacement dans la direction de la saccade ; le deuxième est sous forme de compression vers l'objet cible. Ce dernier type d'erreur, la compression du champ visuelle vers l'objet de la saccade, est le phénomène principal dont cette thèse s'est servi pour étudier les mécanismes qui engendrent la stabilité visuelle lors des saccades. Une série d'expérience psychophysique a donc été réalisée pour explorer les signaux qui entre en jeux lors du jugement spatial de la cible d'une saccade.Dans le premier chapitre, nous avons élucidé un schéma expérimental qui décrit l'interaction d'un signal oculomoteur qui encode le mouvement oculaire avec un signal visuel qui encode la position de la cible. Selon notre formulation, l'issue de cette interaction est directement reliée au positionnement perçu de la cible qui est présentée autour d'une saccade. Ce modèle a reproduit non seulement les résultats de notre laboratoire mais aussi ceux d'un collaborateur extérieur dont nous avons reçus que les données brutes. Suite à ce premier succès, lors du deuxième chapitre nous nous sommes orientés vers la nature même du signal oculomoteur. Nous avons accomplit cette tache en utilisant une variété de conditions expérimentales qui visaient à préciser si le signal visuel encodait le mouvement oculaire seule ou en conjonction avec le mouvement de la tête. Nos résultats ont clairement démontré que le phénomène de compression est en effet lié à la combinaison des mouvements des yeux et de la tête, que la compression était vers le but du regard et non l'objet de la saccade en tant que tel. Ces expériences nous ont aussi permis de décrire plus précisément les paramètres et les conditions qui affectent la compression. Armé de notre compréhension de l'effet de compression ci-haut et de ses signaux biologiques probables, lors du dernier chapitre nous avons employés notre model biologique pour comprendre davantage la manière dont la vision chez les patients atteints de la schizophrénie pourrait être altérée lors des saccades. Plus spécifiquement, nous avons étudié l'hypothèse que la décharge corollaire (DC) des voies optiques pourrait être altérée chez les patients schizophrènes. Nos études ont en effet souligné que lors des saccades, les patients schizophrènes démontrent des différences qualitatives en terme d'erreur de localisation de signal par rapport aux patients du groupe témoin. Le résultat de cette étude à démontrer que le DC dans les schizophrènes était différent que chez les contrôles, et que cette différence était suffisante pour expliquer les différences remarquées dans leur perception visuelle autour des saccades.

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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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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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Whitchurch, Elizabeth A. "Audiovisual integration in the saccadic system of the barn owl /." view abstract or download file of text, 2006. http://proquest.umi.com/pqdweb?did=1280135971&sid=3&Fmt=2&clientId=11238&RQT=309&VName=PQD.

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Thesis (Ph. D.)--University of Oregon, 2006.
Typescript. Includes vita and abstract. "These investigations were supported in part by the National Institute on Deafness and Communication Disorders ... and the National Institute of General Medical Sciences"--P. viii. Includes bibliographical references (leaves 142-152). Also available for download via the World Wide Web; free to University of Oregon users.

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Awater, Holger. "Perception of visual space at the time of saccadic eye movements Wahrnehmung des visuellen Raumes im Zeitraum sakkadischer Augenbewegungen /." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965503003.

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Ziesche, Arnold, and Fred H. Hamker. "Brain circuits underlying visual stability across eye movements—converging evidence for a neuro-computational model of area LIP." Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-147862.

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The understanding of the subjective experience of a visually stable world despite the occurrence of an observer's eye movements has been the focus of extensive research for over 20 years. These studies have revealed fundamental mechanisms such as anticipatory receptive field (RF) shifts and the saccadic suppression of stimulus displacements, yet there currently exists no single explanatory framework for these observations. We show that a previously presented neuro-computational model of peri-saccadic mislocalization accounts for the phenomenon of predictive remapping and for the observation of saccadic suppression of displacement (SSD). This converging evidence allows us to identify the potential ingredients of perceptual stability that generalize beyond different data sets in a formal physiology-based model. In particular we propose that predictive remapping stabilizes the visual world across saccades by introducing a feedback loop and, as an emergent result, small displacements of stimuli are not noticed by the visual system. The model provides a link from neural dynamics, to neural mechanism and finally to behavior, and thus offers a testable comprehensive framework of visual stability.

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Szinte, Martin. "The recovery of target locations in space across movements of eyes and head." Phd thesis, Université René Descartes - Paris V, 2012. http://tel.archives-ouvertes.fr/tel-00760375.

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The visual system has evolved to deal with the consequences of our own movements onour perception. In particular, evolution has given us the ability to perceive our visual world as stableand continuous despite large shift of the image on our retinas when we move our eyes, head orbody. Animal studies have recently shown that in some cortical and sub-cortical areas involved inattention and saccade control, neurons are able to anticipate the consequences of voluntary eyemovements on their visual input. These neurons predict how the world will look like after a saccadeby remapping the location of each attended object to the place it will occupy following a saccade.In a series of studies, we first showed that remapping could be evaluated in a non-invasive fashion in human with simple apparent motion targets. Using eye movement recordingsand psychophysical methods, we evaluated the distribution of remapping errors across the visualfield and found that saccade compensation was fairly accurate. The pattern of errors observedsupport a model of space constancy based on a remapping of attention pointers and excluded otherknown models. Then using targets that moved continuously while a saccade was made across themotion path, we were able to directly visualize the remapping processes. With this novel method wedemonstrated again the existence of systematic errors of correction for the saccade, best explainedby an inaccurate remapping of expected moving target locations. We then extended our model toother body movements, and studied the contribution of sub-cortical receptors (otoliths and semi-circular canals) in the maintenance of space constancy across head movements. Contrary tostudies reporting almost perfect compensations for head movements, we observed breakdowns ofspace constancy for head tilt as well as for head translation. Then, we tested remapping of targetlocations to correct for saccades at the very edge of the visual field, remapping that would place theexpected target location outside the visual field. Our results suggest that visual areas involved inremapping construct a global representation of space extending out beyond the traditional visualfield. Finally, we conducted experiments to determine the allocation of attention across saccades.We demonstrated that the attention captured by a brief transient was remapped to the correctspatial location after the eye movement and that this shift can be observed even before thesaccade.Taken together these results demonstrate the management of attention pointers to therecovery of target locations in space as well as the ability of behavioral measurements to address atopic pioneered by eletrophysiologists.

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Tagu, Jérôme. "Le rôle de la dominance oculaire dans la boucle perception-action : une propriété à l'origine d'asymétries perceptives et motrices How eye dominance strength modulates the influence of a distractor on saccade accuracy Isoler les effets de la dominance oculaire et du biais attentionnel sur la précision des saccades Influence de la dominance oculaire sur les sélections oculomotrice et attentionnelle Recentering bias for temporal saccades only: evidence from binocular recordings of eye movements Quantifying eye dominance strength – New insights into the neurophysiological bases of saccadic asymmetries." Thesis, Sorbonne Paris Cité, 2018. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=1818&f=14763.

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L'homme présente plusieurs préférences latérales, utilisant plutôt une main, un pied et un œil donnés. Si l'impact de la latéralité manuelle sur les performances perceptives et motrices a été très étudié, le rôle des autres latéralités est mal connu. Le premier axe de cette thèse avait pour objectif de mieux comprendre la place de la dominance oculaire dans les processus perceptivo-moteurs. L’œil dominant est celui choisi lors de la réalisation d'une tâche monoculaire. La neuroimagerie a montré qu'il était lié au cortex visuel primaire ipsilatéral, et du fait du croisement des voies optiques, à l'hémichamp visuel controlatéral. Dans cette thèse nous avons comparé les performances perceptives et oculomotrices dans les hémichamps controlatéral et ipsilatéral à l’œil dominant. Les participants devaient soit réaliser des saccades oculaires vers la gauche ou vers la droite, soit réaliser une tâche de discrimination visuelle sur une cible présentée à gauche ou à droite, soit réaliser une double-tâche de saccades et discrimination visuelle. Ces études ont montré que la relation entre l’œil dominant et le cortex visuel primaire ipsilatéral permettait un rehaussement perceptif des cibles visuelles de l'hémichamp controlatéral comparées à celles de l'hémichamp ipsilatéral. Ce rehaussement perceptif améliore à la fois les performances de discrimination visuelle et la précision des saccades oculaires dans l'hémichamp controlatéral à l’œil dominant comparé à l'hémichamp ipsilatéral. Nous avons ainsi montré que la dominance oculaire occupait une place importante dans les relations perception-action, engendrant des différences de traitement entre hémichamps visuels. Dans un deuxième axe, nous nous sommes intéressés à la quantification de la dominance oculaire. Contrairement aux questionnaires de latéralité manuelle permettant une mesure en pourcentages, les tests actuels de dominance oculaire ne fournissent qu'une mesure binaire (gauche ou droite). En vue d'attribuer à chaque individu un pourcentage de dominance oculaire, nous avons étudié les asymétries du système saccadique. Les saccades oculaires présentent en effet des pics de vitesse plus élevés vers la tempe (saccades vers la gauche de l’œil gauche et saccades vers la droite de l’œil droit) que vers le nez (saccades vers la droite de l’œil gauche et saccades vers la gauche de l’œil droit). Cette asymétrie semble liée à l'intensité de la dominance oculaire en ne s'exprimant que chez les participants ayant une dominance oculaire faible. En cas d'une forte dominance oculaire, les pics de vitesse sont plus élevés vers l'hémichamp ipsilatéral à l’œil dominant, que la saccade soit nasale ou temporale. Dans la présente thèse, nous avons également testé d'autres asymétries saccadiques avec l'idée que l'étude simultanée de plusieurs asymétries permettrait une quantification graduelle de dominance oculaire. Notamment, les pics de vitesse sont aussi plus élevés pour les saccades centripètes (vers le droit-devant) que centrifuges (vers l'extérieur). Nous avons utilisé une tâche de saccades depuis cinq positions de départ (afin d'analyser des saccades centripètes et centrifuges) et un enregistrement binoculaire (afin d'analyser des saccades temporales et nasales). Les résultats montrent (1) que les deux asymétries saccadiques sont liées, suggérant qu'elles partagent des bases neurophysiologiques communes, (2) que la dominance oculaire influence toutes les asymétries testées et (3) que l'analyse simultanée des deux asymétries permet d'assigner à chaque individu un pourcentage de dominance oculaire. L'absence de dominance oculaire correspondait à la manifestation de toutes les asymétries saccadiques, tandis qu'une dominance oculaire maximale correspondait à l'absence d'asymétries. Ainsi, cette thèse aura précisé les rôles de la dominance oculaire dans la boucle perception-action et permis d'élaborer une mesure graduelle de dominance oculaire, basée sur les performances visuo-motrices
Humans present several lateral preferences, using more a given hand, foot and eye than the other one. If handedness has already been shown to influence perceptual and motor performance, the role of other lateral preferences is currently unknown. The first part of this thesis is dedicated to the study of the influence of eye dominance on visuo-motor tasks. The dominant eye, the one used to perform monocular tasks, is linked to the ipsilateral primary visual cortex. As such, it I s also linked to the contralateral hemifield. In this thesis, we thus compared performance in the contralateral and ipsilatereral hemifields relative to the dominant eye. Participants had either to make leftward and rightward saccades, a visual discrimination task, or both simultaneously. These studies have shown that the relationship between the dominant eye and the ipsilateral primary visual cortex induced a greater perceptual enhancement of visual targets presented in the contralateral than ipsilateral hemifield relative to the dominant eye. This perceptual enhancement leaded to both higher discrimination performance and higher saccade accuracy in this hemifield compared to the ipsilateral one. Thereby, we showed that eye dominance was an important property to consider in the perception-action links, leading to asymmetries between hemifields. In a second part of this thesis, we focused on the quantification of eye dominance. Indeed, contrary to handedness questionnaires which provide a percentage-based measure, tests of eye dominance only dissociate between left and right eye dominance. To assign to each participant a percentage of eye dominance, we studied the asymmetries of the saccadic system. Saccadic peak velocity is indeed higher toward the temple (i.e., rightward saccades of the right eye and leftward saccades of the left eye) than toward the nose (i.e., leftward saccades of the right eye and rightward saccades of the right eye). This asymmetry seems linked to the strength of eye dominance, as it is only observed in case of weak eye dominance. People with strong eye dominance show higher saccadic peak velocity toward the hemifield ipsilateral to their dominant eye, irrespective of the temporal or nasal nature of the saccade. In this thesis, we simultaneously tested several saccadic asymmetries, with the idea that it could provide a graduated measure of eye dominance strength. Peak velocities are also higher for centripetal (toward the straight-ahead direction) than centrifugal (away from the straight-ahead direction) saccades. Participants had to make saccades from five different starting position (to elicit centripetal and centrifugal saccades) while the movements of their both eyes were recorded (to analyze temporal and nasal saccades). The results showed (1) that both saccadic asymmetries are linked together, suggesting that they share a common structure in their neurophysiological bases, (2) that eye dominance modulates all the saccadic asymmetries tested, and (3) that the study of several saccadic asymmetries allows quantifying eye dominance strength on a percentage-based continuous model. Observation of huge saccadic asymmetries corresponded to very weak eye dominance, whereas strong eye dominance was associated to no asymmetry. All in all, in this thesis we clarified the roles of eye dominance in the perception-action loop, and we computed a graduated measure of eye dominance strength based on oculomotor performance

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Eymond, Cécile. "L'attention sélective et les traits visuels dans la correspondance transsaccadique." Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCB234.

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Chaque saccade oculaire décale brusquement l'image projetée sur la rétine. Pourtant notre perception du monde reste stable et uniforme car le système visuel fait correspondre les informations avant et après chaque saccade. Pour établir cette correspondance, les mécanismes attentionnels seraient fondamentaux. Jusqu'à présent, ce lien transsaccadique a été mis en évidence par des études portant essentiellement sur le traitement des informations spatiales - à savoir, comment la position rétinienne d'un objet est corrigée à chaque saccade pour maintenir une perception stable du monde. Le traitement des traits visuels tels que la couleur ou la forme est encore mal compris et leur rôle dans l'impression de stabilité reste à établir. Est-ce que les traits et l'attention dédiée aux traits (feature-based attention), par définition indépendants de l'espace, participent aussi à la correspondance transsaccadique ? Pour analyser la relation entre le traitement des traits et celui des positions lors des saccades oculaires, cette thèse a suivi deux approches. La première s'est intéressée à la perception des attributs visuels, uniforme malgré l'hétérogénéité du système visuel. Les résultats ont montré que si la perception uniforme des attributs visuels s'appuie sur un apprentissage, les mécanismes sous-jacents ne seraient pas spécifiques aux mouvements oculaires. L'uniformité de la perception s'appuierait plutôt sur un mécanisme d'apprentissage associatif général. La seconde approche a cherché à mieux comprendre la nature de l'attention sélective transsaccadique. Les résultats ont montré que l'attention allouée à la cible d'une saccade ne contribue pas à aux mécanismes sélectifs guidés par les traits et engagés juste après l'exécution d'un mouvement oculaire. L'attention allouée à une cible saccadique et l'attention aux traits seraient alors indépendantes. Enfin, la dernière étude a montré que, lorsque l'attention sélective basée sur les traits est engagée pendant la préparation de la saccade en dehors de la cible saccadique, les traits sont maintenus pendant la saccade et affectent les processus sélectifs engagés juste après la saccade. L'attention transsaccadique ne serait alors pas de nature purement spatiale. L'ensemble de ces résultats suggère que les traits et l'attention aux traits joueraient un rôle dans la correspondance transsaccadique
With each saccade, the image on the retina shifts abruptly but our perception of the surrounding world remains stable and uniform, because the visual system matches pre- and post-saccadic visual information. Attentional mechanisms could play a fundamental role in this process and numerous studies have examined the role of spatial attention. The processing of feature-based attention across saccades remains unclear and its role in matching pre- to post-saccadic visual information is not known. Do visual features and feature-based attention, assumed to enhance the feature-specific representations throughout the visual field, take part in the transsaccadic correspondence? To examine the relationship between feature and spatial processing, this thesis chose two approaches. The first one considered the uniform perception that we have for features despite the heterogeneity of the retina. Results show that, if the transsaccadic correspondence of visual features relies on learning, the underlying mechanisms would not be specific to eye movements. Visual constancy is more likely to arise from a general associative learning. The second approach examined the nature of transsaccadique attention. Results show that attention drawn to the saccade target did not contribute to selective mechanisms engaged just after an eye movement, suggesting a dissociation between feature-based attention and saccade programming. Finally, the last study show that feature-based selectivity is maintained across saccades to ensure spatiotopic correspondence, pointing out the potential role of feature-based attention in matching pre- to post-saccadic information

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Notice, Keisha Joy. "Visual working memory and saccadic eye movements." Thesis, Anglia Ruskin University, 2013. http://arro.anglia.ac.uk/332975/.

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Saccadic eye movements, produced by the oculomotor system, are used to bring salient information in line with the high resolution fovea. It has been suggested that visual working memory, the cognitive system that temporarily stores and manipulates visual information (Baddeley & Hitch, 1974), is utilised by the oculomotor system in order to maintain saccade programmes across temporal delays (Belopolsky & Theeuwes, 2011). Saccadic eye movements have been found to deviate away from information stored in visual working memory (Theeuwes and colleagues, 2005, 2006). Saccadic deviation away from presented visual stimuli has been associated with top-down suppression (McSorley, Haggard, & Walker, 2006). This thesis examines the extent to which saccade trajectories are influenced by information held in visual working memory. Through a series of experiments behavioural memory data and saccade trajectory data were explored and evidence for visual working memory-oculomotor interaction was found. Other findings included specific interactions with the oculomotor system for the dorsal and ventral pathways as well as evidence for both bottom-up and top-down processing. Evidence of further oculomotor interaction with manual cognitive mechanisms was also illustrated, suggesting that visual working memory does not uniquely interact with the oculomotor system to preserve saccade programmes. The clinical and theoretical implications of this thesis are explored. It is proposed that the oculomotor system may interact with a variety of sensory systems to inform accurate and efficient visual processing.

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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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Coles, Peter Richard. "The development of saccadic eye movements during visual spatial tasks." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238172.

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Craven, Benjamin Joseph. "Saccadic undershoot and the perception of lateral spatial extent." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302947.

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Mannan, Sabira Khanam. "The visual analysis of complex scenes." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321654.

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Ludwig, Casimir Johannes Hendrikus. "Stimulus-driven and goal-driven control over visual selection." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269218.

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Davitt, Lina I. "Eye movements and the visual perception of shape." Thesis, Bangor University, 2012. https://research.bangor.ac.uk/portal/en/theses/eye-movements-and-the-visual-perception-of-shape(e8c97b73-656b-4041-a54a-74726eeb409c).html.

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This thesis reports the results of five novel studies that used eye movement patterns to elucidate the role of shape information content of object shape representation in human visual perception. In Experiments 1, and 2 eye movements were recorded while observers either actively memorised or passively viewed different sets of novel objects, and during a subsequent recognition memory task. ..• -'", ••. Fixation data were contrasted against different models of shape mralyses based on surface curvature bounding vs. internal contour and low level image visual saliency. The results showed a preference for fixation at regions of internal local features (either concave or/and convex) during both active memorisation and passive viewing of object shape. This pattern changed during the recognition phase where there was a fixation preference towards regions containing concave surface curvature minima. It is proposed that the preference of fixation at regions of concavity reflect the operation of a depth-sensitive view interpolation process that is constrained by key points encoding regions of concave curvature minima. Experiments 3 and 4 examined the extent to which fixation-based local shape analysis patterns are influenced by the perceptual expertise of the observer and the level of stimulus classification required by the task. These studies were based on the paradigm developed by Wong, Palmeri & Gauthier (2009) in which observers are extensively trained to categorize sets of novel objects (Ziggerins) at either a basic or subordinate level of classification. The effects of training were measured by comparing performance between a pre- and post-test sequential shape matching task that required either basic- or subordinate-level judgements. In addition, we also recorded fixation patterns during the pre- and post-tests.

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Richard, Christian M. "Goal-driven and stimulus-driven control of visual attention in a multiple-cue paradigm." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0018/NQ46409.pdf.

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Hudoba, Michelle Jane. "Three-dimensional eye and head movements evoked by passive rotation of cats." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0021/MQ56183.pdf.

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Smith, Nicholas David. "Eye movements, search and perception of visual field defects in glaucoma." Thesis, City University London, 2011. http://openaccess.city.ac.uk/1132/.

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Glaucoma is a progressive disease of the optic nerve that can result in irreversible loss of visual function and impairment in everyday visual tasks. The experimental studies described in this thesis primarily aim to investigate the performance of people with glaucoma on search and other visual tasks whilst simultaneously monitoring eye movements, making comparison with age-related visually healthy people. In an experiment focussing on visual search, a patient group (n=30) took significantly longer on average to find a target in images of everyday scenes than controls (n=30). Furthermore, comparison of eye movements made by the participants during this task revealed there was a statistically significant reduction (6%) in saccade rate in the patients compared to the controls, and that saccade rate correlated with performance. Similar differences in eye movements were observed when the same groups passively viewed a selection of images in a slideshow. A bivariate contour ellipse (BCE) analysis revealed that, on average, patients viewed smaller regions of the images compared to the controls. Eye movement differences between patients and controls were also examined in a different cohort of people with glaucoma (n=14) and visually healthy controls (n=22) whilst they watched a selection of Hazard Perception Test driving films. Saccade rate of the patients was found to increase by 9%, though results from the BCE analysis suggested the average size of viewing area was similar in both groups. Finally, a novel interview-based study of 50 people with glaucoma provides evidence that patients do not perceive their visual field defect as a black ‘tunnel’ effect, or as ‘black patches’, but more like blurred regions: this finding may, for example, impact on how glaucomatous visual field loss is depicted in patient information about the condition. In conclusion, the results from this thesis show how visual loss from glaucoma influences how patients perceive and react to their visual environment. The principal findings from the studies described in this thesis also show, for the first time, that eye movement analysis could provide a window into the functional deficits associated with glaucoma.

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McDermott, Kyle C. "Visual search and eye movements in novel and familiar contexts." abstract and full text PDF (free order & download UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1453596.

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21

陳海壽 and Hoi-shou Chan. "An experimental study on the inter-relationship of visual lobe, eye movement parameters and search performance." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1985. http://hub.hku.hk/bib/B31207169.

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Jie, Li 1976. "An eye movement dependent visual attention model and its application /." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115910.

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In this dissertation, we study the relationship between eye movements and visual attention. Different types of eye movements are investigated including microsaccades, eye fixation, and eye pursuit. First, we demonstrate that microsaccades occur during pursuit and they are linked to covert attention shifts. Employing a psychophysical task that involves covert attention shifts to a peripheral square, we detect if microsaccades occur during eye pursuit, and, if so, whether, and in what way, microsaccades are related to attention shifts. Microsaccades are found to occur during pursuit and they present in similar patterns as those occurring during eye fixation. We discover that microsaccades tend to be biased towards the same direction as pursuit and the bias increases with increases of pursuit velocities. Through the analysis of microsaccade orientation and latency, we argue that microsaccades occurring during pursuit, rather than being randomly distributed, have a link with covert attention shifts. This is consistent with what has been reported for microsaccades occurring during fixation. Further analysis of microsaccade amplitude supports this argument. The potential attention mechanisms for the characteristics of microsaccades are discussed. We suggest that the attention allocation during pursuit is responsible for the characteristics of microsaccades. Our analyses of microsaccades also enforce the argument that microsaccades may be the suppressed saccades.
In addition to microsaccades, the attention allocation during eye fixation and eye pursuit are considered as well. We demonstrate that, during eye fixation, the local image content around the area of a fixation point is a significant factor to influence the fixation duration. However, during pursuit, the pursuit direction, rather than image contents, is important to decide attention allocation. According to these results, a top-down attention model based on types of eye movements is built. Three types of eye movements are considered separately in the model. They are eye fixation, eye pursuit, and saccadic eye movements (including microsaccades). The model is applied to the design of an interactive 2D video game. We demonstrate that the game is successfully designed in different difficulty levels through the analysis of attention allocation by our attention model. Our results imply that the attention modeling can be used to alter the game play so as to provide varying difficulty levels and it is also promising to take advantage of eye tracking data for broader applications, such as for navigation, intelligent map searching, augmented reality, and others.

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Hsiao, Yi-Ting. "Visual perception of Chinese orthography : from characters to sentences." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/25762.

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There are different aims in this thesis. The primary aim is to investigate visual perception in Chinese orthography, from its fundamentally distinct unit, characters, to sentence reading. The first aim of the thesis is to investigate how a single Chinese character is processed in many ways. We have looked into an effect called orthographic satiation/decomposition (Cheng & Wu, 1994). It refers to the feeling of uncertainty about the composition of some characters when staring at a character for too long. Lee (2007) extended Cheng and Wu’s study (1996), and the results have showed that orthographic satiation occurred faster in females than males. We replicated Lee’s study (Experiment 1) (Chapter 3), and have found that: (1) there was no significant difference between male and female and (2) a radical that can stand alone as a single character makes characters in which it occurs resistant to satiation. Following orthographic satiation, in Chapter 4, we explored the preference for eye/hemisphere visual pathways in Chinese characters (Experiment 2 & 3) and words (Experiment 4). In English, researchers have reported a contralateral preference when four-letter words were presented very quickly using a haploscope (Obreg´on & Shillcock, 2012) . It raises the question of whether presenting Chinese characters and words will show similar results considering the complexity and the special characteristics of Chinese orthography. We presented Chinese characters and words to participants using a haploscope. Our results showed that: (1) the contralateral visual pathway was preferred in perceiving right-left structured Chinese characters and two-character words, (2) when a semantic radical is projected to the LH, participants are able to recognise the semantic component better, (3) neighbourhood size (NS) (Tsai, Lee, Lin, Tzeng & Hung, 2006) affects how participants recognise words, and(4) males do better than females recognising characters but not words. After investigating the recognition of Chinese characters and words, we analysed the eye-movements in Chinese and English reading corpora. The processes of reading are intuitively thought to be more complex than perceiving a single character or words. The last studies in the thesis focused on the reading behaviours in Chinese and English. The eye movement differences and similarities between reading Chinese and English were investigated. In Chapter 5, we showed that reading Chinese elicits more divergence of the eyes within a fixation, compared with reading English. We interpreted these data in terms of recent demonstrations that apparent size causes increases in visual sensitivity (Arnold & Schindel, 2010) and engages more cortical resource in V1 (Kersten & Murray, 2010). Our analyses were based on movement within exactly temporally synchronized binocular fixations in the reading of Chinese and English 5000-word multi-line texts, using monocular calibration, with EyeLink-2 technology. When faced with visually complex orthography, the oculomotor system ‘tricks’ the rest of the visual system into ‘zooming in’ on the text. We consolidated the relevant theorizing into the ‘Divergence Affects Reading’ (DOLLAR) Theory. In Chapter 6, we reported that (1) vertical movements within a fixation tend to be smaller than horizontal ones, and (2) vertical movements within a fixation tend to be upwards. We speculated that it is appropriate for the earlier part of the fixation to be associated with visual recognition and for the later part of the fixation to be associated with executive action. The tendency to move upwards also suggested that in real-world reading, the upper part of words/characters were informative. In the last chapter analysing the reading corpus (Chapter 7), we reported corrective saccades after return sweeps. We found that in English, there were more corrective saccades after return sweeps than in Chinese. We interpreted these data in terms of spatial coding (Kennedy & Murray, 1987). In terms of Chinese and English differences, the stimuli that were used in our corpus show that the length for each line was different in English. The length for each line in Chinese was less different. Though the first character of each line was at the same place for two languages, it was more difficult for English subjects to locate the correct place after return sweeps because the length of return sweeps was different. In short, this thesis investigated visual perception in Chinese orthography, in terms of characters, words, and real-world reading. Moreover, we compared the differences and similarities between languages (English and Chinese). Despite the fact that the orthographies of English and Chinese are very different, we still found similar effects (e.g., contralateral preference) between them. This thesis thus has contributed to a better understanding of the differences and similarities between English and Chinese in terms of the orthographies.

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Schweitzer, Richard. "Perceptual and Motor Consequences of Intra-saccadic Perception." Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/22148.

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Sakkadische Blickbewegungen sind die häufigsten und schnellsten aller menschlichen Bewegungen und führen zur wiederholtem und rapiden Verschiebung von Objektprojektionen über die Retina. Entgegen der verbreiteten Annahme der Suppression untersucht diese Arbeit Ausmaß und Funktion intrasakkadischer visueller Wahrnehmung. Studie I beschreibt eine individuell gefertigte LED-Installation zur ausschließlich intrasakkadischen Präsentation von Text und Bildern, während Studie II einen Algorithmus zur Detektion von Sakkaden vorstellt, welcher blickkontingente Stimulusmanipulationen mithilfe eines DLP Projektionssystems mit einer Bildwiederholungsrate von 1440 Hz ermöglicht. Studien III und IV untersuchten ob visuelle Bewegungsspuren (sog. motion streaks), welche durch die schnelle Bewegung von Objekten über die Retina erzeugt werden, Korrespondenz zwischen Objekten über Sakkaden hinweg herstellen könnten. Diese Bewegungsspuren erlaubten Versuchsteilnehmern nicht nur einen präsakkadischen Stimulus aus zwei identischen postsakkadischen Stimuli zu identifizieren, während diese Fähigkeit von der Deutlichkeit der Bewegungsspur abhing, sondern auch Korrektursakkaden zu einem ursprünglichen präsakkadischen Stimulus zu erleichtern, falls dieser während der Sakkade versetzt wurde. Studie V untersuchte die subjektive Wahrnehmung und Lokalisierung von intrasakkadischen Bewegungsspuren, indem Teilnehmer gezeichnete Berichte angaben. Die Modellierung letzterer ergab, dass retinale Positionssignale mit einer zeitlich gedämpften mentalen Repräsentation von Augenposition kombiniert wurden, um eine Lokalisation in weltzentrierten Koordinaten zu ermöglichen. Diese Ergebnisse legen nahe, dass intrasakkadische visuelle Signale einen Einfluss auf transsakkadische perzeptuelle und motorische Prozesse haben könnten. Letztlich werden die mögliche Funktionen intrasakkadischer Wahrnehmung, sowie Möglichkeiten für zukünftige wissenschaftliche Untersuchungen, diskutiert.
Rapid eye movements, so-called saccades, are the fastest and most frequent human movements and cause projections of objects in the world to constantly shift across the retina at high velocities, thereby producing large amounts of motion blur. In contrast to accounts of saccadic suppression, this work explores the extent and potential functional role of intra-saccadic perception. As saccades are fast and brief events, technical challenges were addressed. Study I describes a custom LED-based anorthoscopic presentation setup capable of displaying text and images strictly during saccades. In study II, a novel online saccade detection algorithm enabled rapid, gaze-contingent display changes using a DLP projection system running at 1440 fps. Studies III and IV investigated whether intra-saccadic motion streaks, i.e., blurred traces routinely induced by stimuli moving at saccadic speeds, could serve as cues to establishing object correspondence across saccades. Motion streaks not only enabled perceptual matching of pre- and post-saccadic object locations, while performance depended strongly on streak efficiency, but also facilitated gaze correction in response to intra-saccadic target displacements, that was previously found to be mainly driven by objects’ surface features. Finally, study V explored the subjective appearance and localization of intra-saccadic motion streaks, tasking observers to reproduce their trajectories. Computational modeling of resulting response patterns suggested that retinal positions over time were combined with a damped eye position signal to readily localize intra-saccadic input in world-centered coordinates. Taken together, these results invite the intriguing hypothesis that intra-saccadic visual signals are not discarded from processing and might affect trans-saccadic perceptual and motor processes. The potential role of intra-saccadic perception for active vision, as well as directions for future research, are discussed.

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25

Kovalenko, Lyudmyla. "The temporal interplay of vision and eye movements." Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17507.

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Das visuelle System erreicht enorme Verarbeitungsmengen, wenn wir unsere Augen auf ein Objekt richten. Mehrere Prozesse sind aktiv bevor unser Blick das neue Objekt erreicht. Diese Arbeit erforscht die räumlichen und zeitlichen Eigenschaften drei solcher Prozesse: 1. aufmerksamkeitsbedingte Steigerung der neuronalen Aktivität und sakkadische Suppression; 2. aufmerksamkeitsbasierte Auswahl des Zielreizes bei einer visuellen Suchaufgabe; 3. zeitliche Entwicklung der Detektiongenauigkeit bei der Objekt-Substitutionsmaskierung. Wir untersuchten diese Prozesse mit einer Kombination aus humaner Elektroenzephalografie (EEG), eye tracking und psychophysischen Verhaltensmessungen. Zuerst untersuchten wir, wie die neuronale Repräsentation eines Reizes von seiner zeitlichen Nähe zur Sakkade geprägt wird. Wir zeigten, dass direkt vor der Sakkade erscheinende Reize am meisten durch Aufmerksamkeit und Suppression geprägt sind. In Studie 2 wurde die Sichtbarkeit des Reizes mit der Objekt-Substitutionsmaskierung verringert, und wir analysierten das Verhältnis zwischen sakkadischen Reaktionszeiten und ihrer Genauigkeit. Dazu erfassten wir neuronale Marker der Aufmerksamkeitslenkung zum Zielreiz und eine subjektive Bewertung seiner Wahrnehmbarkeit. Wir stellten fest, dass schnelle Sakkaden der Maskierung entgingen und Genauigkeit sowie subjektive Wahrnehmbarkeit erhöhten. Dies zeigt, dass bereits in frühen Verarbeitungsstadien eine bewusste und korrekte Wahrnehmung des Reizes entstehen kann. Wir replizierten diesen Befund für manuelle Antworten, um eine Verfälschung der Ergebnisse durch sakkadenspezifische Prozesse auszuschließen. Neben ihrer theoretischen Bedeutung liefern diese Studien einen methodischen Beitrag zum Forschungsgebiet der EEG-Augenbewegung: Entfernung sakkadischer Artefakte aus dem EEG bzw. Erstellung eines künstlichen Vergleichsdatensatzes. Die Arbeit stellt mehrere Ansätze zur Untersuchung der Dynamik visueller Wahrnehmung sowie Lösungen für zukünftige Studien dar.
The visual system achieves a tremendous amount of processing as soon as we set eyes on a new object. Numerous processes are active already before eyes reach the object. This thesis explores the spatio-temporal properties of three such processes: attentional enhancement and saccadic suppression that accompany saccades to target; attentional selection of target in a visual search task; the timecourse of target detection accuracy under object-substitution masking. We monitored these events using a combination of human electrophysiology (EEG), eye tracking and behavioral psychophysics. We first studied how the neural representation of a visual stimulus is affected by its temporal proximity to saccade onset. We show that stimuli immediately preceding a saccade show strongest effects of attentional enhancement and saccadic suppression. Second, using object-substitution masking to reduce visibility, we analyzed the relationship between saccadic reaction times and response accuracy. We also collected subjective visibility ratings and observed neural markers of attentional selection, such as the negative, posterior-contralateral deflection at 200 ms (N2pc). We found that fast saccades escaped the effects of masking, resulted in higher response accuracy and higher awareness ratings. This indicates that early visual processing can trigger awareness and correct behavior. Finally, we replicated this finding with manual responses. Discovering a similar accuracy timecourse in a different modality ruled out saccade-specific mechanisms, such as saccadic suppression and retinal shift, as a potential confound. Next to their theoretical impact, all studies make a methodological contribution to EEG-eye movement research, such as removal of large-scale saccadic artifacts from EEG data and composition of matched surrogate data. In sum, this work uses multiple approaches to describe the dynamics of visual perisaccadic perception and offers solutions for future studies in this field.

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Cong, Yu Fang. "Comparison of visual performance with operational fatigue level based on eye tracking model." Thesis, University of Macau, 2018. http://umaclib3.umac.mo/record=b3950613.

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Vivekananda-Schmidt, Pirashanthie. "Differential effects of simulated visual impairment on locomotion and eye-movements in the built environment." Thesis, University of Ulster, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369950.

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Matsumoto, Yukiko. "Visual processing and social cognition in schizophrenia: Relationships among eye movements, biological motion perception, and empathy." Kyoto University, 2016. http://hdl.handle.net/2433/204558.

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Roldan, Stephanie Marie. "Eye Movements and Hemodynamic Response during Emotional Scene Processing: Exploring the Role of Visual Perception in Intrusive Mental Imagery." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/86165.

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Unwanted and distressing visual imagery is a persistent and emotionally taxing symptom characteristic of several mental illnesses, including depression, schizophrenia, and posttraumatic stress disorder. Intrusive imagery symptoms have been linked to maladaptive memory formation, abnormal visual cortical activity during viewing, gaze pattern deficits, and trait characteristics of mental imagery. Emotional valence of visual stimuli has been shown to alter perceptual processes that influence the direction of attention to visual information, which may result in enhanced attention to suboptimal and generalizable visual properties. This study tested the hypothesis that aberrant gaze patterns to central and peripheral image regions influence the formation of decontextualized visual details which may facilitate involuntary and emotionally negative mental imagery experiences following a stressful or traumatic event. Gaze patterns and hemodynamic response from occipital cortical locations were recorded while healthy participants (N = 39) viewed and imagined scenes with negative or neutral emotional valence. Self-report behavioral assessments of baseline vividness of visual imagery and various cognitive factors were combined with these physiological measures to investigate the potential relationship between visual perception and mental recreation of negative scenes. Results revealed significant effects of task and valence conditions on specific fixation measures and hemodynamic response patterns in ventral visual areas, which interacted with cognitive factors such as imagery vividness and familiarity. Findings further suggest that behaviors observed during mental imagery reveal processes related to representational formation over and above perceptual performance and may be applied to the study of disorders such as PTSD.
Ph. D.

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30

Simoncini, Claudio. "Intégration spatio-temporelle de l'information visuelle pour les mouvements oculaires et la perception : =Spatio-temporal integration of visual information for eye movements and perception." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM5065/document.

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Dans ce travail de thèse, nous avons tout d’abord étudié comment l’information de mouvement est intégrée pour estimer la vitesse d’une texture aléatoire afin de la suivre réflexivement avec les yeux ou d’estimer perception son déplacement. Dans une seconde série d’études, nous avons étudié comment la distribution spatiale du contraste dans une texture affecte à la fois les mouvements oculaires de fixation et la reconnaissance perceptive. A ces fins, nous avons utilisé un nouvel ensemble de stimuli visuels, des textures pseudo-naturelles dans lesquelles on peut finement contrôler la statistique (moyenne, variance) des fréquences spatiales et/ou temporelles. La première partie explore l’intégration et le décodage de information fréquentielle spatio-temporelle visuelle pour les réponses de poursuite réflexes et la discrimination perceptive. Nous montrons que l’action tire complètement partie de la richesse du stimuli en intégrant sur toute la distribution pour estimer la vitesse : accélération initiale, précision et robustesse sont améliorées. Au contraire, la performance perceptive décroit pour des stimuli à bandes passantes larges. Cette dissociation se maintient sur une large place d’intégration temporelle. La seconde partie élargie cette approche à la distribution spatiale de l’information et à ces différentes échelles. Nous montrons que le comportement oculaire de fixation dépend de la composition fréquentielle d’une texture, en termes de moyenne et de fréquence. Saccade et micro-saccades se distribuent au cours de la fixation de façon coordonnée en fonction de cette statistique. In fine, cette dernière joue sur la carte de salience calculée à partir de l’image
We focused on the impact of the statistical distributions of visual information on these various behavioral responses. We asked first how motion information is integrated to estimate speed in order to perform either a speed discrimination task or to control reflexive tracking eye movements. Next, we investigated how spatial distribution in textures affects both pattern recognition and fixational eye movements. To do so, we used a set of artificial stimuli that are naturalistic textures where we can maintain a tight control on their information contents as for instance their spatio-temporal frequency bandwidth. The first studies compared speed information decoding for ocular following eye movements and perceptual speed discrimination. We found a strong dissociation where ocular following take full advantage by the enlargement of the spatio-temporal frequency bandwidth while perceptual speed discrimination is largely impaired for large bandwidth stimuli. Such dissociation remains over a large temporal integration window. We propose an adaptive gain control mechanism to explain this opposite dependencies. The second series of experimental studies investigate the properties of fixation eye movements (microsaccade and saccade) as a function of the mean and variance of the spatial frequency content of visual static textures. We show that several characteristics of fixational saccades (location, direction and amplitude) varied systematically with the distribution of spatial frequencies. The spatial distribution of the fixation zones could be best predicted from the saliency maps of the stimuli

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Startsev, Mikhail [Verfasser], Michael [Akademischer Betreuer] Dorr, Erhardt [Gutachter] Barth, Michael [Gutachter] Dorr, and Klaus [Gutachter] Diepold. "Computationally Modelling Human Visual Perception: Eye Movements and Saliency / Mikhail Startsev ; Gutachter: Erhardt Barth, Michael Dorr, Klaus Diepold ; Betreuer: Michael Dorr." München : Universitätsbibliothek der TU München, 2020. http://d-nb.info/1223616851/34.

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32

Adelore, Temilade Adediwura. "Determining fixation stability of amd patients using predictive eye estimation regression." Thesis, Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26495.

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Patients with macular degeneration (MD) often fixate with a preferred retinal locus (PRL). Eye movements made while fixating with the PRL (in MD patients) has been observed to be maladaptive compared to those made while fixating with the fovea (normal sighted individuals). For example, in MD patients, PRL eye movements negatively affect fixation stability and re-fixation precision; consequently creating difficulty in reading and limits to their execution of other everyday activities. Abnormal eye movements from the PRL affect research on the physiological adaptations to MD. Specifically, previous research on cortical reorganization using functional magnetic resonance imaging (fMRI), indicates a critical need to accurately determine a MD patient's point of gaze in order to better infer existence of cortical reorganization. Unfortunately, standard MR compatible hardware eye-tracking systems do not work well with these patients. Their reduction in fixation stability often overwhelms the tracking algorithms used by these systems. This research investigates the use of an existing magnetic resonance imaging (MRI) based technique called Predictive Eye Estimation Regression (PEER) to determine the point of gaze of MD patients and thus control for fixation instability. PEER makes use of the fluctuations in the MR signal caused by eye movements to identify position of gaze. Engineering adaptations such as temporal resolution and brain coverage were applied to tailor PEER to MD patients. Also participants were evaluated on different fixation protocols and the results compared to that of the micro-perimeter MP-1 to test the efficacy of PEER. The fixation stability results obtained from PEER were similar to that obtained from the eye tracking results of the micro-perimeter MP-1. However, PEER's point of gaze estimations was different from the MP-1's in the fixation tests. The difference in this result cannot be concluded to be specific to PEER. In order to resolve this issue, advancements to PEER by the inclusion of an eye tracker in the scanner to run concurrently with PEER could provide more evidence of PEER's reliability. In addition, increasing the diversity of AMD patients in terms of the different scotoma types will help provide a better estimate of PEER flexibility and robustness.

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Holm, Linus. "Predictive eyes precede retrieval : visual recognition as hypothesis testing." Doctoral thesis, Umeå : Department of Psychology, Umeå University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1179.

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Helo, Andrea, Pia Rämä, Sebastian Pannasch, and David Meary. "Eye movement patterns and visual attention during scene viewing in 3- to 12-month-olds." Cambridge University Press, 2016. https://tud.qucosa.de/id/qucosa%3A70683.

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Recently, two attentional modes have been associated with specifi c eye movement patterns during scene processing. Ambient mode, characterized by short fi xations and long saccades during early scene inspection, is associated with localization of objects. Focal mode, characterized by longer fi xations, is associated with more detailed object feature processing during later inspection phase. The aim of the present study was to investigate the development of these attentional modes. More specifi cally, we examined whether indications of ambient and focal attention modes are similar in infants and adults. Therefore, we measured eye movements in 3- to 12-months-old infants while exploring visual scenes. Our results show that both adults and 12-month-olds had shorter fi xation durations within the fi rst 1.5 s of scene viewing compared with later time phases (>2.5 s); indicating that there was a transition from ambient to focal processing during image inspection. In younger infants, fi xation durations between two viewing phases did not differ. Our results suggest that at the end of the fi rst year of life, infants have developed an adult-like scene viewing behavior. The evidence for the existence of distinct attentional processing mechanisms during early infancy furthermore underlines the importance of the concept of the two modes.

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Meyberg, Susann. "Microsaccades as a window to visuospatial attention." Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2017. http://dx.doi.org/10.18452/17756.

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Die Erforschung visueller Aufmerksamkeit beruht auf verdeckter Aufmerksamkeit; das heißt, wenn der Fokus der Aufmerksamkeit trotz strikter Fixation ausgerichtet wird ohne größere Sakkaden auszuführen. EEG-Studien haben das neuronale Netzwerk identifiziert, dass verdeckte Aufmerksamkeit steuert. Diese Studien ignorieren jedoch unwillkürliche kleine Sakkaden während der Fixation - Mikrosakkaden (MS) genannt. Blickbewegungsstudien hingegen belegen einen Zusammenhang zwischen Aufmerksamkeit und diesen MS, beziehen ihre Resultate jedoch nicht auf etablierte EEG-Befunde. Um diese Forschungslücke zu schließen, zielt diese Dissertation darauf, den Zusammenhang zwischen Ereignis-korrelierten Potentialen (EKP) endogener Aufmerksamkeit und MS zu untersuchen. Folglich wurden drei Studien mit gleichzeitiger Erfassung von EEG und Blickbewegungen durchgeführt. In den Studien haben die Probanden ein „Posner Spatial-Cueing-Paradigma“ absolviert mit einem endogenen Hinweisreiz. Wir zeigen deutliche Zusammenhänge zwischen MS und neuronalen Korrelaten visueller Aufmerksamkeit. Erstens, MS und ein posteriores EKP reflektierten die Selektion visueller Reize basierend auf deren Merkmale. Dieses Ergebnis stärkt die Idee eines Netzwerkes, dass relevante Reize unter Distraktoren selektiert und zielgerichtetes Verhalten initiiert. Zweitens, MS erzeugten ein visuelles Potential, das verstärkte Potentialkomponenten für Reize zeigte, die im Aufmerksamkeitsfokus lagen. Dieses MS-evozierte Potential stellte einen zeitlich gut aufgelösten Aufmerksamkeitsindex dar. Drittens, MS erzeugten zudem ein in früheren Studien übersehenes, korneoretinales Artefakt. Dieses Artefakt kontaminierte die Messung eines frontalen EKPs, dass zuvor mit der Kontrolle von Aufmerksamkeit assoziiert war. Zusammenfassend zeigt diese Dissertation, dass die gleichzeitige Erfassung von EEG und Blickbewegungen bedeutsame Einblicke in den Zusammenhang von MS und visueller Aufmerksamkeit erlaubt.
Research on visual attention focusses on covert attention; that is, when attention is directed during fixation periods in the absence of larger saccades. While previous EEG research has provided insights into the neural network that controls covert attention, this field fails to account for the inevitable occurrence of miniature fixational saccades - called microsaccades (MS). In contrast, previous eye-tracking research has established links between MSs and covert attention, but has not directly related their findings to seminal EEG results. This thesis bridges this research gap by investigating the link between event-related potentials (ERPs) of endogenous attention and MSs. To this end, three studies were conducted with concomitant ERP and high-resolution eye-tracking recordings while participants performed a Posner spatial cueing task with an endogenous cue. Crucially, we show that MSs relate to neural correlates of visual attention. First, MS and an early posterior ERP reflected the top-down selection of a visual stimulus based on its features. This finding is consistent with the notion of a neural network that selects relevant stimuli from distracting ones and initiates goal-directed behavior toward selected stimuli. Second, gaze shifts from MSs evoked a visual potential in the EEG that was enhanced for stimuli in the focus of attention; a finding well-known for the visual potential measured after presenting a stimulus. Importantly, these MS-related potentials provided a fine-grained temporal index of the subject’s attentional state. Finally, MSs further evoked a corneoretinal artifact overlooked in previous EEG studies. This artifact contaminated the measurement of a frontal ERP previously associated with preparatory attentional control. In sum, this thesis provides first evidence for the benefits of using concomitant ERP and eye-tracking recordings to examine the link between MSs and visual attention.

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Fayel, Alexandra. "Mécanismes de sélection visuelle pour l'action et pour la perception : apports de l'étude des saccades oculaires chez des patients présentant une hémianopsie latérale homonyme." Thesis, Paris 5, 2014. http://www.theses.fr/2014PA05H101.

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La saccade oculaire, i.e. mouvement très rapide des yeux, permet d’amener l’objet d’intérêt sur la fovéa, afin que le système visuel puisse analyser ses propriétés. Malgré l’importance du cortex occipital dans le traitement de l’information visuelle, son rôle dans la génération de saccades est encore peu connu. Pour ce faire, l’hémianopsie latérale homonyme consécutive à une atteinte unilatérale du cortex occipital (i.e. amputation de l’hémichamp visuel controlésionnel) peut être considérée comme modèle d’étude. En effet, malgré la perte de la vision consciente, certains patients sont capables de répondre à un stimulus présenté dans l’hémichamp controlésionnel. Ces capacités préservées, appelées vision aveugle, peuvent être de nature attentionnelle et/ou motrice. Le but de cette thèse est ainsi d’étudier l’implication du cortex occipital dans la génération de saccades. En manipulant les propriétés spatiales et temporelles du point de fixation, de la cible ou d’un distracteur, les paramètres des saccades de ces patients ont été examinés en étudiant différents types de saccades (volontaires et réactives) ainsi que des effets connus pour moduler les paramètres saccadiques (effets d’un distracteur et adaptation saccadique). Parallèlement, les capacités de vision aveugle ont été examinées à partir de différentes tâches perceptives (détection et discrimination), nécessitant une réponse verbale, manuelle (appui-bouton) et/ou oculomotrice (saccade et fixation). Malgré la perte de la conscience visuelle du stimulus présenté dans l’hémichamp controlésionnel, des capacités de vision aveugle sont attestées par la réalisation d’une action oculomotrice sur ce stimulus. La dichotomie observée dans ces capacités en fonction de la nécessité de réaliser une action sur la stimulation visuelle suppose une implication du cortex occipital dans les mécanismes de sélection pour l’action et pour la perception. Par ailleurs, une dissociation est observée dans l’atteinte des paramètres saccadiques. Si l’initiation de la saccade – reflétée par la latence - est altérée dans les deux hémichamps ipsi- et controlésionnel, le calcul de la métrique de la saccade – reflétée par l’amplitude - est spécifiquement altéré dans l’hémichamp controlésionnel. Ainsi, nos résultats sont en faveur d’une implication du cortex occipital dans la génération des saccades oculaires ainsi qu’en faveur d’un modèle fonctionnel de génération de saccades à deux voies de traitement parallèles dédiées respectivement à l’initiation et à la métrique de la saccade
Saccadic eye movements are rapid and necessary to targeting the interesting object in our visual environment. Despite the crucial role of the occipital cortex in the visual process, its implication in the saccadic generation is poorly studied. To examine this, we can use one pathological model, the homonymous hemianopia (i.e. loss of contralateral visual hemifield to unilateral occipital lesion). Despite the loss of conscious vision, some patients can be able to react at one stimulus presented in the contralesional hemifield. These residual abilities, named blindsight, can be observed in attentional and/or motor tasks. The aim of this thesis is examine the parameters of saccades in hemianopic patients, through the study of saccade types (voluntary and reflexive saccades) and classical effects on the modulation of saccadic parameters (gap effect and distractor effects, by manipulating the spatial and temporal characteristics of the fixation point, the target or a distractor). Furthermore, the residual abilities are investigated by perceptual tasks (detection or discrimination) with different types of response: verbal, manual (key press) and motor (saccade or fixation). Overall, despite the loss of conscious perception of the target presented in the contralesional hemifield, residual abilities are found as showed by the saccadic execution toward the target, with a dichotomy depending on the need to perform an action on the visual stimulation. This suggests that the role of the occipital cortex is not the same in the selection mechanism for the action and the perception. Concerning to saccadic programming, dissociation is found in the saccadic parameters. The saccadic initiation, studied by with the saccade latency, is altered in both ipsi- and contralesional hemifields but the saccade metric, studied by the saccade amplitude, is altered in the contralesional hemifield. This suggests that the occipital cortex is implicated in the saccade generation and that saccade programing involves two pathways for the initiation and the metric of saccades

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Silva, Jéssica Bruna Santana. "Efeitos da ingestão aguda moderada de álcool nos movimentos oculares: um estudo duplo-cego, placebocontrolado." Universidade Federal da Paraíba, 2016. http://tede.biblioteca.ufpb.br:8080/handle/tede/8643.

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Alcohol is one of the most widely consumed psychoactive substances worldwide and the negative impacts related alcohol use has become a problem of global public health. Research suggests that alcohol use can cause impairments to various cognitive and perceptual processes. Specifically, there is evidence that acute ingestion of alcohol can change the eye movements. The aim of this study was to evaluate the effects of moderate acute alcohol intake in eye movements, having as parameter the concentration of 0.08% BAC. In a double-blind, placebo controlled design, 20 volunteers participated in both conditions: Experimental (0.08%) and control (placebo) in order counterbalanced. We used the Eye Tracker Tobii TX300 equipment for tracking eye movement, and as a stimulus, Visual Maze Test. Data were analyzed using SPSS version 20, being conducted normality test, descriptive and inferential analysis. Analysis with paired t test showed significant differences in the pattern of eye movements between the two conditions. The results indicated significant differences in the parameters of eye movements: fixation number (p = 0.001, r = 0.713) and fixation duration average (p = 0.004, r = 0.597) and total (p = 0.026, r = 0.485), saccade number (p = 0.001, r = 0.728) and saccade total duration (p = 0.028, r = 0.478) and total time of Visual maze test performance (p = 0.014, r = 0.525). However, no significant difference in the pupil diameter between conditions. In addition, Analysis of Variance of two factors mixed showed no interaction effect between the independent variables alcohol and sex. These results suggest that alcohol can cause impairments in eye movement pattern in young adults, which may cause impairments in processing of visual information.
O álcool etílico é uma das substâncias psicoativas mais consumidas mundialmente e os impactos negativos relacionados o uso do álcool têm se tornado um problema de saúde pública mundial. Investigações sugerem que o uso do álcool pode causar prejuízos a diversos processos cognitivos e perceptuais. Especificamente, há evidências de que a ingestão aguda do álcool pode alterar os movimentos oculares. O objetivo do presente estudo foi verificar os efeitos do consumo agudo de álcool nos movimentos oculares, tendo como parâmetro a concentração de 0,08% BAC. Utilizando um delineamento duplo-cego, placebo controlado, 20 voluntários participaram das duas condições: Experimental (0,08 %) e Controle (placebo), em ordem contrabalanceada. Utilizou-se o equipamento Eye tracker Tobii TX300, para rastreamento do movimento ocular, e como estímulo, o Teste do Labirinto Visual. Os dados foram analisados por meio do software SPSS versão 20, sendo realizados teste de normalidade, análises descritivas e inferenciais. Análises com o Teste t de medidas repetidas mostraram diferenças significativas no padrão de movimentos oculares entre as duas condições. Os resultados indicaram diferenças significativas nos parâmetros de movimentos oculares: número de fixações (p = 0,001, r = 0,713), duração média (p = 0,004, r = 0,597) e total (p = 0,026, r = 0,485) da fixação, número de sacadas (p = 0,001, r = 0,728) e duração total das sacadas (p = 0,028, r = 0,478) e tempo de execução do Teste do Labirinto Visual (p = 0,014, r = 0,525). No entanto, não houve diferença significativa em relação ao diâmetro pupilar entre as condições. Além disso, a Análise de Variância de dois fatores mostrou que não houve efeito de interação entre as variáveis independentes álcool e sexo. Estes resultados sugerem que o álcool pode acarretar prejuízos no padrão de movimento ocular de adultos jovens, podendo levar a alterações no processamento de informações visuais.

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Lemonnier, Sophie. "L'allocation de l'attention visuelle lors d'une situation naturelle et dynamique : l'approche de carrefour en conduite." Thesis, Paris 8, 2015. http://www.theses.fr/2015PA080066/document.

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Avec ce travail, nous avons voulu mettre l'accent sur la validité externe des expérimentations et nous focaliser sur des situations dynamiques naturelles. Or dans ce type de situation, les traitements top-down, découlant des connaissances préalables et de l'objectif, guident préférentiellement l'allocation de l'attention, tandis que les traitements bottom-up (caractéristiques des entrées perceptives) ont une influence mineure. Ce travail est donc centré sur l'attention top-down. La situation choisie est une approche de carrefour en conduite automobile, les sous-tâches étudiées sont le contrôle du véhicule (la trajectoire) et la décision de s'arrêter ou non au carrefour. Deux objectifs opérationnels sont investigués à travers l'analyse des mouvements oculaires : 1/ distinguer les sous-tâches de contrôle du véhicule et de prise de décision, 2/ distinguer les processus de la sous-tâche de prise de décision. Pour chaque objectif, une approche qualitative puis quantitative sont explorées. Des techniques de classification supervisées ont notamment été utilisées pour distinguer les différents processus. Deux études ont été conduites afin de répondre à ces objectifs, une en simulateur de conduite et une en situation réelle de conduite, mettant toutes deux en scène des approches de carrefours
In this work, we focus on the external validity of experiments and on natural dynamic situations. In this type of situation, the top-down treatments resulting from prior knowledge and goal preferably guide the allocation of attention, while the bottom-up treatments (characteristics of perceptual input) play a minor role. This work is then focused on top-down attention. The chosen situation is an approach of driving crossroads, the studied subtasks are the control of vehicle (trajectory) and the decision to stop or not at the crossroads. Two operational objectives are investigated by analyzing eye movements: 1/ discriminating the vehicle's control and decision making subtasks, 2/ discriminating the process of the decision making subtask. For each objective, we explore a qualitative and quantitative approach. In particular, supervised techniques of classification have been used to distinguish the different processes. Two studies were conducted in order to meet these objectives, one with a driving simulator and one in a real situation of driving, both involving approaches to crossroads

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Green, Melissa Jayne. "Facial affect processing in delusion-prone and deluded individuals: A continuum approach to the study of delusion formation." University of Sydney. Psychology, 2002. http://hdl.handle.net/2123/792.

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This thesis examines attentional and cognitive biases for particular facial expressions in delusion-prone and deluded individuals. The exploration of cognitive biases in delusion-prone individuals provides one means of elucidating psychological processes that might be involved in the genesis of delusions. Chapter 1 provides a brief review of the continuum approach to schizophrenia, and outlines recent theoretical conceptualisations of delusions. The study of schizophrenia phenomena at the symptom level has become a popular method of inquiry, given the heterogeneous phenotypic expression of schizophrenia, and the uncertainty surrounding the existence of a core neuropathology. Delusions are one of the most commonly experienced symptoms of schizophrenia, and have traditionally been regarded as fixed, false beliefs that are pathognomonic of an organic disease process. However, recent phenomenological evidence of delusional ideation in the general population has led to the conceptualisation of delusions as multi-dimensional entities, lying at the extreme end of a continuum from normal through to maladaptive beliefs. Recent investigations of the information processing abnormalities in deluded individuals are reviewed in Chapter 2. This strand of research has revealed evidence of various biases in social cognition, particularly in relation to threat-related material, in deluded individuals. These biases are evident in probabilistic reasoning, attribution style, and attention, but there has been relatively little investigation of cognitive aberrations in delusion-prone individuals. In the present thesis, social-cognitive biases were examined in relation to a standard series of faces that included threat-related (anger, fear) and non-threatening (happy, sad) expressions, in both delusion-prone and clinically deluded individuals. Chapters 3 and 4 present the results of behavioural (RT, affect recognition accuracy) and visual scanpath investigations in healthy participants assessed for level of delusion- proneness. The results indicate that delusion-prone individuals are slower at processing angry faces, and show a general (rather than emotion-specific) impairment in facial affect recognition, compared to non-prone healthy controls. Visual scanpath studies show that healthy individuals tend to direct more foveal fixations to the feature areas (eyes, nose, mouth) of threat-related facial expressions (anger, fear). By contrast, delusion-prone individuals exhibit reduced foveal attention to threat-related faces, combined with �extended� scanpaths, that may be interpreted as an attentional pattern of �vigilance-avoidance� for social threat. Chapters 5 and 6 extend the work presented in Chapters 3 and 4, by investigating the presence of similar behavioural and attentional biases in deluded schizophrenia, compared to healthy control and non-deluded schizophrenia groups. Deluded schizophrenia subjects exhibited a similar delay in processing angry faces, compared to non-prone control participants, while both deluded and non-deluded schizophrenia groups displayed a generalised affect recognition deficit. Visual scanpath investigations revealed a similar style of avoiding a broader range of negative (anger, fear, sad) faces in deluded schizophrenia, as well as a common pattern of fewer fixations with shorter duration, and reduced attention to facial features of all faces in both deluded and non-deluded schizophrenia. The examination of inferential biases for emotions displayed in facial expressions is presented in Chapter 7 in a study of causal attributional style. The results of this study provide some support for a �self-serving� bias in deluded schizophrenia, as well as evidence for an inability to appreciate situational cues when making causal judgements in both delusion-prone and deluded schizophrenia. A theoretical integration of the current findings is presented in Chapter 8, with regard to the implications for cognitive theories of delusions, and neurobiological models of schizophrenia phenomena, more generally. Visual attention biases for threat-related facial expressions in delusion-prone and deluded schizophrenia are consistent with proposals of neural dysconnectivity between frontal-limbic networks, while attributional biases and impaired facial expression perception may reflect dysfunction in a broader �social brain� network encompassing these and medial temporal lobe regions. Strong evidence for attentional biases and affect recognition deficits in delusion-prone individuals implicates their role in the development of delusional beliefs, but the weaker evidence for attributional biases in delusion-prone individuals suggests that inferential biases about others� emotions may be relevant only to the maintenance of delusional beliefs (or that attributional biases for others� emotional states may reflect other, trait-linked difficulties related to mentalising ability). In summary, the work presented in this thesis demonstrates the utility of adopting a single-symptom approach to schizophrenia within the continuum framework, and attests to the importance of further investigations of aberrant social cognition in relation to the development of delusions.

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Dornhöfer, Sascha M. "Veränderungsblindheit." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1114955960020-08344.

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Veränderungsblindheit tritt auf, wenn das Bewegungssignal einer Veränderung verdeckt wird oder der Betrachter von der Veränderung abgelenkt wird. In beiden Fällen kann die visuelle Aufmerksamkeit, mangels Hinweisreiz, nicht zum Ort der Veränderung gelenkt werden. Nach einer Erörterung von Augenbewegungen und ihrem Zusammenhang mit Veränderungsblindheit werden drei explorative Untersuchungen zur Veränderungsblindheit im Kontext des Straßenverkehrs vorgestellt. Untersuchung 1 befasst sich mit einem direkten Vergleich dreier unterschiedlicher Verdeckungsarten (Lidschläge, Blicksprünge, Blanks) bei statischem Stimulusmaterial (Fotos). Insgesamt führen die Ergebnisse zu dem Schluss, dass Veränderungsblindheit, unabhängig von der Verdeckungsart, ein Grund für zu spät oder nicht erkannte Gefahren im Straßenverkehr sein könnte, wenngleich sie für die gefährlichsten Situationen (relevante Additionen) am geringsten ausfällt und künstliche Blanks sich, zumindest in einer statischen Bedingung, gut zur Simulation von Lidschlägen und Sakkaden eignen. Darüber hinaus zeigen sich deutliche Hinweise zur impliziten Veränderungsentdeckung. Untersuchung 2 überprüft Teile von Untersuchung 1 in dynamischer Umgebung (Fahrsimulator) und findet überraschenderweise einen umgekehrten Effekt von Veränderungsblindheit. Die Echtheit des Effektes wird angezweifelt und auf die Nutzung von Abzählstrategien zurückgeführt. Unabhängig davon zeigen sich erneut Hinweise zur impliziten Entdeckung. Untersuchung 3 stellt schließlich einen direkten Vergleich zwischen statischer (Fotos) und dynamischer Umgebung (Filme) vor und zeigt, dass das Ausmaß an Veränderungsblindheit, unabhängig von Verdeckungsdauer und Veränderungsart, in dynamischer Umgebung größer ist als in statischer (85% vs. 64%) und daher eine Gefahr im Straßenverkehr darstellt. Wieder zeigen sich Hinweise auf eine implizite Entdeckung. Die Arbeit schließt mit einem grundlagen- und anwendungsorientierten Ausblick.

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Dornhöfer, Sascha M. "Veränderungsblindheit: Drei explorative Untersuchungen in statischer und dynamischer verkehrsbezogener Umgebung." Doctoral thesis, Technische Universität Dresden, 2004. https://tud.qucosa.de/id/qucosa%3A24484.

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Veränderungsblindheit tritt auf, wenn das Bewegungssignal einer Veränderung verdeckt wird oder der Betrachter von der Veränderung abgelenkt wird. In beiden Fällen kann die visuelle Aufmerksamkeit, mangels Hinweisreiz, nicht zum Ort der Veränderung gelenkt werden. Nach einer Erörterung von Augenbewegungen und ihrem Zusammenhang mit Veränderungsblindheit werden drei explorative Untersuchungen zur Veränderungsblindheit im Kontext des Straßenverkehrs vorgestellt. Untersuchung 1 befasst sich mit einem direkten Vergleich dreier unterschiedlicher Verdeckungsarten (Lidschläge, Blicksprünge, Blanks) bei statischem Stimulusmaterial (Fotos). Insgesamt führen die Ergebnisse zu dem Schluss, dass Veränderungsblindheit, unabhängig von der Verdeckungsart, ein Grund für zu spät oder nicht erkannte Gefahren im Straßenverkehr sein könnte, wenngleich sie für die gefährlichsten Situationen (relevante Additionen) am geringsten ausfällt und künstliche Blanks sich, zumindest in einer statischen Bedingung, gut zur Simulation von Lidschlägen und Sakkaden eignen. Darüber hinaus zeigen sich deutliche Hinweise zur impliziten Veränderungsentdeckung. Untersuchung 2 überprüft Teile von Untersuchung 1 in dynamischer Umgebung (Fahrsimulator) und findet überraschenderweise einen umgekehrten Effekt von Veränderungsblindheit. Die Echtheit des Effektes wird angezweifelt und auf die Nutzung von Abzählstrategien zurückgeführt. Unabhängig davon zeigen sich erneut Hinweise zur impliziten Entdeckung. Untersuchung 3 stellt schließlich einen direkten Vergleich zwischen statischer (Fotos) und dynamischer Umgebung (Filme) vor und zeigt, dass das Ausmaß an Veränderungsblindheit, unabhängig von Verdeckungsdauer und Veränderungsart, in dynamischer Umgebung größer ist als in statischer (85% vs. 64%) und daher eine Gefahr im Straßenverkehr darstellt. Wieder zeigen sich Hinweise auf eine implizite Entdeckung. Die Arbeit schließt mit einem grundlagen- und anwendungsorientierten Ausblick.

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Sadr, Shabnam. "Effect of scene transitions on transsaccadic change detection in natural scenes /." 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR45969.

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Thesis (M.A.)--York University, 2008. Graduate Programme in Psychology.
Typescript. Includes bibliographical references (leaves72-76). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR45969

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Prime, Steven L. "Transsaccadic memory and integration of visual features /." 2004. http://wwwlib.umi.com/cr/yorku/fullcit?pMQ99375.

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Thesis (M.A.)--York University, 2004. Graduate Programme in Psychology.
Typescript. Includes bibliographical references (leaves 90-111). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ99375

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Gallego, Pamela. "Search asymmetry and eye movements in infants and adults /." 2006. http://proquest.umi.com/pqdweb?index=0&did=1240706441&SrchMode=1&sid=8&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1195584865&clientId=5220.

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Thesis (M.A.)--York University, 2006. Graduate Programme in Education.
Typescript. Includes bibliographical references (leaves 77-84). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://proquest.umi.com/pqdweb?index=0&did=1240706441&SrchMode=1&sid=8&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1195584865&clientId=5220

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Dahlstrom-hakki, Ibrahim H. "Investigating change blindness in three-dimensional dynamic stimuli." 2004. https://scholarworks.umass.edu/theses/2415.

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Awater, Holger [Verfasser]. "Perception of visual space at the time of saccadic eye movements = Wahrnehmung des visuellen Raumes im Zeitraum sakkadischer Augenbewegungen / vorgelegt von Holger Awater." 2002. http://d-nb.info/965503003/34.

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Crabb, D. P., N. D. Smith, F. G. Rauscher, C. M. Chisholm, J. L. Barbur, D. F. Edgar, and D. F. Garway-Heath. "Exploring eye movements in patients with glaucoma when viewing a driving scene." 2010. http://hdl.handle.net/10454/5943.

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BACKGROUND: Glaucoma is a progressive eye disease and a leading cause of visual disability. Automated assessment of the visual field determines the different stages in the disease process: it would be desirable to link these measurements taken in the clinic with patient's actual function, or establish if patients compensate for their restricted field of view when performing everyday tasks. Hence, this study investigated eye movements in glaucomatous patients when viewing driving scenes in a hazard perception test (HPT). METHODOLOGY/PRINCIPAL FINDINGS: The HPT is a component of the UK driving licence test consisting of a series of short film clips of various traffic scenes viewed from the driver's perspective each containing hazardous situations that require the camera car to change direction or slow down. Data from nine glaucomatous patients with binocular visual field defects and ten age-matched control subjects were considered (all experienced drivers). Each subject viewed 26 different films with eye movements simultaneously monitored by an eye tracker. Computer software was purpose written to pre-process the data, co-register it to the film clips and to quantify eye movements and point-of-regard (using a dynamic bivariate contour ellipse analysis). On average, and across all HPT films, patients exhibited different eye movement characteristics to controls making, for example, significantly more saccades (P<0.001; 95% confidence interval for mean increase: 9.2 to 22.4%). Whilst the average region of 'point-of-regard' of the patients did not differ significantly from the controls, there were revealing cases where patients failed to see a hazard in relation to their binocular visual field defect. CONCLUSIONS/SIGNIFICANCE: Characteristics of eye movement patterns in patients with bilateral glaucoma can differ significantly from age-matched controls when viewing a traffic scene. Further studies of eye movements made by glaucomatous patients could provide useful information about the definition of the visual field component required for fitness to drive.

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Alexander, Clyde. "The beneficial effects of letter sequencing therapy in a comparative study between educationally advantaged and educationally disadvantaged children." Thesis, 2012. http://hdl.handle.net/10210/5765.

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D.Phil.
Efficient ocular saccadics with a clear visual memory are essential functions in reading fluently. A child needs to sequence the eyes in a controlled jump called a saccade in order to form a picture in the mind of what is being read. The child is therefore primarily aware of a story rather than individual words. This sequential visual input of the written text contributes to efficient reading skills. The letter sequencing therapy used in this research is designed to improve the ocular saccadics and also to simultaneously develop an efficient visual memory. This improves the reading skills and creates good comprehension. The above exercise program illustrated that visual therapy, in general, done not only as a physical exercise but by improving the visual memory, will integrate very quickly into a child's perceptual development. Visual therapy can therefore improve the learning skills in an effective and efficient manner. The development of learning skills can be expanded to benefit children that have poor reading skills as a result of cultural deprivation. Until recently, due to apartheid and cultural differences at the pre school level disadvantaged children were deprived of the same standard of education as advantaged children. This research compared the average visual skills in reading of educationally advantaged children to educationally disadvantaged children. This illustrated the gap created by apartheid, differences in culture and preschool stimulation in the two levels of education. 167 children with no particular learning or visual problems were randomly selected from a group of pupils at an average middle class educationally advantaged white school and an average middle class disadvantaged black school. 100 of the children came from two standard 2 and two standard 3 classes of the educationally advantaged school while 67 of the children came from one standard 2 and one standard 3 class of the educationally disadvantaged school. All the children were evaluated before the therapy program began with respect to ocular fixations, ocular regressions, reading rate, directional attack, span of recognition and relative efficiency. All the children were given letter sequencing therapy under supervision of the class teacher. Strict controls were applied.

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Tavassoli, Abtine 1978. "Discovery and representation of human strategies for visual search." Thesis, 2007. http://hdl.handle.net/2152/3702.

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Visual search can simply be defined as the task of looking for an object of interest in a visual environment. Due to its foveated nature, the human visual system succeeds at such task by making many discrete fixations linked by rapid eye movements called saccades. However, very little is known about how saccadic targets (fixation loci) are selected by the brain in such naturalistic tasks. Discoveries to be made are not only invaluable to the field of vision science but are very important in designing automated vision systems, which to this day lag in performance vis-à-vis human observers. What I have sought to accomplish in this dissertation has been to reveal previously unknown saccadic targeting and target selection strategies used by human observers in naturalistic visual search tasks. My driving goal has been to understand how the brain selects fixation loci and target candidates upon fixation, with the objective of using these findings for automated fixation selection algorithms employed for visual search. I have proposed a novel and efficient technique akin to psychophysical reverse correlation to study human observer strategies in locating low-contrast targets under a variety of experimental conditions. My technique has successfully been used to study saccadic programming and target selection in various experimental conditions, including visual searches for targets with known characteristics, targets whose orientation attributes are not known a priori, and targets containing multiple orientations. I have found visual guidance in saccadic targeting and target selection under all experimental conditions, revealed by observers' selectivity for spatial frequencies and/or orientations of stimuli close to that of the target. I have shown that under uncertainty, observers rely on known target characteristics to direct their saccades and to select target candidates upon foveal scrutiny. Moreover, I have demonstrated that multiple orientation characteristics of targets are represented in observer search strategies, modulated by their sensitivity / selectivity for each orientation. Some of my findings have been applied towards applications for automated visual search algorithms.

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Pastva, Amy Marie. "The effects of rhythmic and arrhythmic eye movements on memory recall /." 2008. http://hdl.handle.net/10288/469.

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Dissertations / Theses on the topic 'Eye Saccadic eye movements. Visual perception'

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