This study aims to investigate the information that can be collected about counting strategies when tracking a person’s eye-movements when he/she is doing a mental calculation on a given expression. Eye-tracking is based on the study of what a person look at and the eye-movements between fixations. This study relies on the eye-mind hypothesis which claims that there is a connection between eye movements and the cognitive processes. The result is based on data from two participants and three tasks. The tasks consisted of mathematical expressions with addition and subtraction that the participants solved with mental arithmetic. The data from eye-movements is of such quality that it is possible to see indications on which counting strategies the participants are using and the results are in-line with previous research. The data also show which number the participant focus most on and how they begin to solve the task. On one task both participant gave an incorrect answer and the eye-movement showed where the participants made a mistake. Using this sort of eye-tracking investigation has both its limitations and its possibilities. / Syftet med arbetet är att undersöka vilken information som går att få fram om en persons räknestrategier med eye-tracking som metod. Eye-tracking innebär att en persons ögonrörelser studeras utifrån fixeringar vad någon fokuserar blicken på och sackader förflyttningarna mellan det personen fixerar på. Studien utgår från the eye-mind hypothesis som innebär att det finns ett samband mellan vad någon tittar på och vad den tänker på. Resultatet i det här arbetet baseras på datainsamling från två deltagare som löser tre uppgifter. Uppgifterna innehåller matematiska uttryck med addition och subtraktion som deltagaren ska lösa med huvudräkning. Under tiden deltagaren löste uppgiften registrerades personens ögonrörelser. Data från ögonrörelserna är av sådan kvalitet att det går att se indikationer på vilka räknestrategier deltagarna använder. Resultatet stämmer väl överens med data från tidigare studier. Dessutom visar data vilket tal deltagaren fokuserar sin blick på mest och hur deltagaren väljer att börja lösa uppgiften. På en uppgift gjorde båda deltagarna fel och ögonrörelserna kunde då visa var felräkningen uppstod. Metoden att mäta ögonrörelser diskuteras också utifrån dess möjligheter och begränsningar. Slutsatsen av studien är att eye-tracking kan ge värdefull information och kan bidra till förståelse för olika personers sätt att utföra beräkningar.

The real-world sensorimotor paradigm is based on the premise that sufficient ecological complexity is a prerequisite for inducing naturally relevant sensorimotor relations in the experimental context. The aim of this thesis is to embed visual attention research within the real-world sensorimotor paradigm using an innovative mobile gaze-tracking system (EyeSeeCam, Schneider et al., 2009). Common laboratory set-ups in the field of attention research fail to create natural two-way interaction between observer and situation because they deliver pre-selected stimuli and human observer is essentially neutral or passive. EyeSeeCam, by contrast, permits an experimental design whereby the observer freely and spontaneously engages in real-world situations. By aligning a video camera in real time to the movements of the eyes, the system directly measures the observer’s perspective in a video recording and thus allows us to study vision in the context of authentic human behaviour, namely as resulting from past actions and as originating future actions. The results of this thesis demonstrate that (1) humans, when freely exploring natural environments, prefer directing their attention to local structural features of the world, (2) eyes, head and body perform distinct functions throughout this process, and (3) coordinated eye and head movements do not fully stabilize but rather continuously adjust the retinal image also during periods of quasi-stable “fixation”. These findings validate and extend the common laboratory concept of feature salience within whole-body sensorimotor actions outside the laboratory. Head and body movements roughly orient gaze, potentially driven by early stages of processing. The eyes then fine-tune the direction of gaze, potentially during higher-level stages of visual-spatial behaviour (Studies 1 and 2). Additional head-centred recordings reveal distinctive spatial biases both in the visual stimulation and the spatial allocation of gaze generated in a particular real-world situation. These spatial structures may result both from the environment and form the idiosyncrasies of the natural behaviour afforded by the situation. By contrast, when the head-centred videos are re-played as stimuli in the laboratory, gaze directions reveal a bias towards the centre of the screen. This “central bias” is likely a consequence of the laboratory set-up with its limitation to eye-in-head movements and its restricted screen (Study 3). Temporal analysis of natural visual behaviour reveals frequent synergistic interactions of eye and head that direct rather than stabilize gaze in the quasi-stable eye movement periods following saccades, leading to rich temporal dynamics of real-world retinal input (Study 4) typically not addressed in laboratory studies. Direct comparison to earlier data with respect to the visual system of cats (CatCam), frequently taken as proxy for human vision, shows that stabilizing eye movements play an even less dominant role in the natural behaviour of cats. This highlights the importance of realistic temporal dynamics of vision for models and experiments (Study 5). The approach and findings presented in this thesis demonstrate the need for and feasibility of real- world research on visual attention. Real-world paradigms permit the identification of relevant features triggered in the natural interplay between internal-physiological and external-situational sensorimotor factors. Realistic spatial and temporal characteristics of eye, head and body interactions are essential qualitative properties of reliable sensorimotor models of attention but difficult to obtain under laboratory conditions. Taken together, the data and theory presented in this thesis suggest that visual attention does not represent a pre-processing stage of object recognition but rather is an integral component of embodied action in the real world.

The main goal of the present thesis is to contribute to the study of overt visual attention under natural conditions. All publications included in the thesis employ eye-tracking methodology and local image feature analysis. The particular scientific question posed, if all parts of the thesis are considered together, can be formulated as: What experimental (i.e. experimenter controlled) and pseudo-experimental (e.g. demographic characteristics such as age) variables define, quantify and set limits for bottom-up determinants of fixation election? In this summary, I will bring together the answers to this question obtained during the course of the thesis and try to elucidate their significance in relation to the puzzles and riddles of eye movement research. After presenting an overview of the field, I will show how and to what extent fixation selection is altered as a function of age and as certain stimulus components are modified. Finally, I will argue that visual attention involves varying degrees of reliance on bottom-up cues according to the attending agent’s knowledge that is relevant in a given context.

The cognitive processing of a stimulus does not only depend on the physical properties of the stimulus itself but also on the larger context in which it occurs. In this thesis I will present a number of studies that investigate this context-dependency at different levels of cognition. In particular these levels include (1) sensory processing within a modality, (2) sensory integration across modalities and (3) the relation between sensory perception and motor behavior. Accordingly the chapters in this thesis are partitioned into three larger parts, each of which relates to one of these levels. The first study in Part 1 investigates the role of neural oscillations during perceptual grouping. By measuring EEG during contour integration we were not only able to identify the neural sources involved in this process but also to demonstrate local and long-range synchronization of oscillatory activity within frontoparietal networks. This study is then followed by a more general discussion about the properties of oscillatory activity and how they might relate to event-related potentials. The focus of Part 2 will then be on cross-modal interactions and their possible utilization for real-life applications. First we show that simultaneously presented auditory and tactile cues lead to interactions on both a behavioral and neural level. Subsequently we demonstrate how the observed perceptual effects can be used to optimize auditory and tactile localization performance. Finally we propose a setup for utilizing tactile information to enhance the perceptual interpretation of 360° visual scenes. The third and last part of this thesis is dedicated to problems and applications of measuring EEG in the presence of eye movements. Therefore we use eye tracking to investigate and characterize EEG artifacts resulting from ocular activity. Subsequently we develop an algorithm that allows objectively and reliably identifying these artifacts and removing them from the data without affecting the signal from neural sources. Employing this algorithm we then demonstrate that combined EEG and eye tracking can be used for monitoring and shaping both the gaze behavior and the related brain activity in ASD patients. Next to studying cognition with regard to perceptual and behavioral context, this thesis also focuses on the question how the context-relevant signal components can be identified and extracted from the EEG. In the studies presented here we applied a variety of different strategies to approach this problem. These range from resorting to prior knowledge and analyzing only activity from predetermined cortical sources on the one hand, to purely data driven approaches based on logistic regression or eye tracking information on the other hand.

Le système postural est un complexe sensori-moteur qui assure deux grandes fonctions, la stabilisation et l’orientation du corps dans l’espace. Le contrôle postural est permis par l’intégration de trois entrées sensorielles - vestibulaire, somatosensorielle et visuelle-, par le système nerveux central qui réalise les transformations appropriées et coordonnées de ces informations pour générer les réponses musculaires adaptées. Durant de nombreuses années, la posture a été considérée comme un système régulé de façon automatique, mais de récentes études ont mis en évidence l’existence d’une régulation par des processus attentionnels. Le paradigme de double-tâche a été utilisé dans de nombreuses études chez l’adulte puis plus récemment chez l’enfant afin de comprendre les interférences entre une tâche cognitive et une tâche posturale. Les interactions dépendent de différents facteurs tels que la difficulté de la tâche cognitive, la difficulté de la tâche posturale, le contexte environnemental, les capacités attentionnelles et l’âge. Le choix de la tâche oculomotrice comme tâche associée à la tâche posturale permet d’observer les réponses comportementales des adultes et des enfants dans des tâches impliquant différents niveaux attentionnels et différentes régions cérébrales. Les tâches oculomotrices sont réalisées à partir de paradigmes expérimentaux permettant de stimuler différents types de saccades. L’objectif de cette thèse est de comprendre les interactions entre le système postural et le système oculomoteur chez l’enfant en utilisant le paradigme de double-tâche. Nous avons d’abord exploré ces interactions chez le jeune adulte puis nous avons comparé les performances posturales et oculomotrices des adultes à celles des enfants âgés de 7 à 12 ans. Nous avons enregistré les mouvements oculaires et les paramètres posturaux lors de la réalisation de trois tâches oculomotrices - fixation, saccades réactives et anti-saccades- réalisées simultanément au maintien de la posture dans deux tâches posturales, - Romberg et Romberg sensibilisé-. Les enfants de 7-8 ans réalisent sur le plan oculomoteur les saccades réactives comme les adultes, leurs paramètres posturaux sont cependant plus élevés. L’augmentation de la difficulté de la tâche oculomotrice comme dans la tâche d’anti-saccades entraine une forte dégradation des paramètres oculomoteurs et posturaux des enfants de 7-12 ans. De façon générale, les résultats montrent que la difficulté de la tâche oculomotrice entraine des modifications des paramètres posturaux et que la difficulté de la tâche posturale ne semble pas modifier les paramètres oculomoteurs. Ces interférences peuvent être associées à un nombre important de structures cérébrales communes activées pour ces deux tâches. / The postural system is a sensory motor complex controlled which permit two high functions, the stabilization and the orientation of body. The postural control is permit by the integration of three sensorial inputs, vestibular, somatosensory and visuals by the central nervous system; it carries adaptative transformations and coordinates this information to generate the appropriate muscles responses. For a long time, the posture has been considered like as an automatic system, but recents studies showed the regulation by attentionals processes. Further studies used the dual-task paradigm in adults and more recently in children, to understand interferences between a cognitive task and a postural task. The interactions depend on various factors such as the difficulty of the cognitive task, the difficulty of the postural task, the environmental context, the attentional capacity and the age. Choose oculomotor task as task associated at postural task allows simple, varying the protocol used to observe the behavior of adults and children in tasks involving different attentionals levels and different brain regions. Several experimental oculomotors paradigms allow to stimulate different types of saccades. The objective of this thesis is to understand, by using the dual-task paradigm, the interactions between the oculomotor system and the postural system in children. Initially, we observed these interferences in young adults then we compared the adults postural and oculomotor performance to those of children aged 7 to 12 years. Three oculomotor tasks, fixation, reactive saccades and antisaccades, were recorded simultaneously to two postural tasks, standard Romberg and tandem Romberg. Children aged 7-8 years achieve on oculomotor performance the reactive saccade task like adults, by cons their postural parameters are higher than adults. When we increase the difficulty of the oculomotor task, in case in antisaccade task, leads very quickly at the decrease of the oculomotor and postural performances for children aged 7 to 12 years. Generally, results show that the oculomotor difficulty leads to modifications of postural parameters and the postural difficulty do not seem modify the oculomotor parameters. These interferences can be associated with a large number of common brain structures activated for both tasks.

Le système visuel a évolué de manière à prendre en compte les conséquences de nos mouvements sur notre perception. L’évolution nous a particulièrement doté de la capacité à percevoir notre environnement visuel comme stable et continu malgré les importants déplacements de ses projections sur nos rétines à chaque fois que nous déplaçons nos yeux, notre tête ou notre corps. Des études chez l’animal ont récemment montré que dans certaines aires corticales et sous-corticales, impliquées dans le contrôle attentionnel et dans l’élaboration des mouvements oculaires, des neurones sont capables d’anticiper les conséquences des futurs mouvements volontaires des yeux sur leurs entrées visuelles. Ces neurones prédisent ce à quoi ressemblera notre environnement visuel en re-cartographiant la position des objets d’importance à l’endroit qu’ils occuperont après l’exécution d’une saccade. Dans une série d’études, nous avons tout d’abord démontré que cette re- cartographie pouvait être évaluée de manière non invasive chez l’Homme avec de simples cibles en mouvement apparent. En utilisant l’enregistrement des mouvements des yeux combinés à des méthodes psychophysiques, nous avons déterminé la distribution des erreurs de re-cartographie à travers le champ visuel et ainsi découvert que la compensation des saccades oculomotrices se faisait de manière relativement précise. D’autre part, les patterns d’erreurs observés soutiennent un modèle de la constance spatiale basé sur la re-cartographie de pointeurs attentionnels et excluent d’autres modèles issus de la littérature. Par la suite, en utilisant des objets en mouvement continu et l’exécution de saccades au travers de leurs trajectoires, nous avons mis à jour une visualisation directe des processus de re-cartographie. Avec ce nouveau procédé nous avons à nouveau démontré l’existence d’erreurs systématiques de correction pour les saccades, qui s’expliquent par une re-cartographie imprécise de la position attendue des objets en mouvement. Nous avons par la suite étendu notre modèle à d’autres types de mouvements du corps et notamment étudié les contributions de récepteurs sous-corticaux (otoliths et canaux semi-circulaires) dans le maintien de la constance spatiale à travers des mouvements de la tête. Contrairement à des études décrivant une compensation presque parfaite des mouvements de la tête, nous avons observé une rupture de la constance spatiale pour des mouvements de roulis et de translation de la tête. Enfin, nous avons testé cette re-cartographie de la position des objets compensant un déplacement oculaire avec des cibles présentées à la limite du champ visuel, une re-cartographie censée placer la position attendue de l’objet à l’extérieur du champ visuel. Nos résultats suggèrent que les aires visuelles cérébrales impliquées dans ce processus de re-cartographie construisent une représentation globale de l’espace allant au-delà du traditionnel champ visuel. Pour finir, nous avons conduit deux expériences pour déterminer le déploiement de l’attention à travers l’exécution de saccades. Nous avons alors démontré que l’attention capturée par la présentation brève d’un stimuli est re-cartographiée à sa position spatiale correcte après l’exécution d’une saccade, et que cet effet peut être observé avant même l’initiation d’une saccade. L’ensemble de ces résultats démontre le rôle des pointeurs attentionnels dans la gestion du rétablissement des positions d’un objet dans l’espace ainsi que l’apport des mesures comportementales à un champ de recherche initialement restreint à l’électrophysiologie / 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.

Eye-tracking is the process of determining the point where the viewer is looking at. Therefore, an eye tracker is a device that measures eye positions and eye movements. Over the recent few years, eye trackers are being used in research in the area of medical technology, visual system, rehabilitation, and human-computer interaction. This study explores the application of eye-tracking in watching and rendering images on a computer screen. In this research, Eye-tracker 5 developed by Tobii is used which is a popular instrument among other eye trackers. Tobii Eye Tracker 5 includes a software development kit (SDK) enabling the creation of new research projects based on eye-tracking and head movement. This work measured eye-tracking streaming data on the digital images, and post-process the gaze data to observe the gaze pattern of the human eye. This thesis investigated the impact of blinking using subtle gaze direction (SGD) approach, which states that flickering on the computer screen in peripheral vision instead of foveal vision attracts human attention and as the viewer’s foveal vision attracted to that blinking point, flickering was stopped and, subsequently, performed flickering to the next point of interest while the viewer is watching the previous point of interest. The work successfully modeled flickering on the desired locations of an image. Furthermore, rendering to different images is also demonstrated in this work using entirely through eye movement. It is envisaged that eye-gazing-based control technology would have tremendous applications in almost all areas of future technology, particularly in assistive technology.

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This dissertation is a collection of a total of seven publications that deal with eye movement disorders in patients with basal ganglia disorders. We obtained normative data for videooculography in healthy individuals. We have described the eye movement evolution during a human life such as the increase of latency, movements become hypometric and antisaccadic error rate increases. We have shown that sex and education do not affect the eye movements. Our study highlighted the asymmetry in the eye movement performance. As the first, we studied the vergence in patients with Parkinson's disease (PN) using videooculography (VOG). We devised and defined a paradigm for this examination and saw that in patients with PN there is a prolonged latency and hypometry of divergence. In patients with ephedrone induced parkinsonism (EP), we were the first who examined eye movements and found that it was possible to identify between this toxic Parkinson's syndrome and PN on the basis of a videooculography. In EP patients, we described velocity decsrease and hypometry in horizontal saccades, prolonged latency in horizontal saccades, and higher error rate in the antisacadic task. Behavioral disorder in REM sleep (RBD) as a prodromal stage of PN leads to impaired eye movement. In the evaluation with PN patients, we...

Reflective eye movementa as a function of cognitive nodes were studied in English speaking and Spanish bilingual populations (N=20). A total of 40 questions were asked with the initial, lateral eye movement recorded. Questions consisted of 20 verbal-mathematical type intended to elicit right-eye movement and 20 spatial questions intended to elicit left-eye movement. A significant difference in responses was found dependent on the type of questions asked (F=114.3421,p<.001). No significant differences were obtained between the two groups.