Several recent studies have investigated advanced preparation of oculomotor programs after training to make saccades to a specific location in space. However, in natural visual scenes, we seldom know the precise stimulus location, rather, we often know the general area where target of interest may appear. Here, we investigated how human saccadic reaction time (SRT) and saccade final landing position may be affected by training to attend to an area where a target will appear. Additionally, we looked at how training to an area of one size may influence eye movements to targets presented in a larger area. Subjects were trained to attend to an area-cue of 6° in diameter, always presented in the same quadrant of the visual field, at the same spatial coordinates. During training, targets were presented at random locations inside the cued area. After training, targets were presented inside an area-cue (except for a few catch trials) of either the same size or of a larger size (i.e. 10° diameter). Results show that training-related saccades were directed toward individually distinctive preferred regions inside the trained area, and towards identical regions in relative coordinates inside the larger 10° area. Importantly, training-related saccades were mostly in the anticipatory range, a large proportion of which was followed by the corrective second saccades directed towards the target. Our findings suggest that anticipatory saccades should be considered in the assessment of training-related changes in oculomotor preparation of saccadic programming.

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Lic.-avh. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 2 uppsatser.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 207-218).

Saccadic eye movements are guided by attention. Indeed, some saccade trajectory effects serve as an index the attentional strength of visual objects in the map of visual space used to plan a saccade. One approach to understanding saccade planning relies on simple tasks in sparse displays (containing a single target and distractor object) to develop neurophysiologically plausible models of saccade behavior. Under tightly controlled conditions, saccade trajectories can be well predicted by representing displays of objects with simple visual features and their relative salience. But the world in which the saccade system typically operates is not sparse, and observer eye movements are guided by more than just salience. As such, another approach has been to examine saccadic behavior in complex scenes and complicated goals. Such scene context can drastically affect saccades in ways that are not well predicted by a context-free and expectation-free representation of visual salience. This dissertation starts to bridge this gap between these literatures by focusing on object surfaces. Covert shifts of attention operate on representations informed not just by stimulus salience and location-based expectations, but also by the perceptual organization of object surfaces. Covert attention can be guided by surface context, such that targets and distractors are processed differently as a function of whether they are on the same or different surface. These effects are fragile, however, and have previously only been demonstrated in relatively engaging tasks and with strong perceptions of objecthood. The present work tested the strength of the relationship between attention and saccades by testing whether surface context guides orienting eye movements. Observers made saccades to objects that could be organized with different surface structure. In four experiments (Chapters 2 and 3) I found no evidence that the saccade map encoded surface context. But in two experiments (Chapters 4 and 5) I demonstrate saccade trajectories are sensitive to surface context, independently of low or high task engagement. This demonstrates that object surface-based representations are not necessarily fragile and can affect the oculomotor map even for simple saccadic orienting for which the surface is task-irrelevant. This lends evidence to the theory that the nature of the representation of vision is one of object surfaces, and suggests that the strength of object encoding is stronger than has been previously demonstrated.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 176-194).

A serious consequence of maternal consumption of alcohol during pregnancy is the fetal alcohol syndrome (FAS): characterized by growth deficiency (both pre- and post-natal), craniofacial dysmorphology and central nervous system (CNS) dysfunction. However, in the absence of the characteristic facial features, and without confirmed history of alcohol exposure, clinical diagnosis remains a significant challenge. Recently, the term fetal alcohol spectrum disorders (FASD) has been adopted to encompass all diagnoses relating to a history of prenatal alcohol exposure. The purpose of this study was to test the following three general hypotheses: Children with FASD 1) demonstrate specific deficits in oculomotor control that can be measured using saccadic eye movement tasks, 2) display specific deficiencies in multiple domains of executive function that can be determined using standardized neuropsychological tasks, and 3) reveal deficits in oculomotor control that correlate with deficiencies in executive function as measured using standardized neuropsychological tasks. A preliminary study revealed significant deficits in saccadic eye movement tasks and provided the foundation for a large, multi-centered study assessing oculomotor control and neuropsychological function in children with FASD. A mobile laboratory was created, which facilitated recruitment of 92 control subjects and 89 subjects with FASD. We found significant evidence for oculomotor deficits across multiple outcome measures following the saccadic eye movement experiments, especially for oculomotor tasks that probe aspects of executive function. Additionally, children with FASD exhibited performance deficits in neuropsychological tasks that assess planning, attention, spatial working memory and strategy; cognitive skills also included within the domain of executive function. Finally, significant correlations between these two objective measures were found for children with FASD, which were not evident in the control sample. These findings are consistent with significant frontal lobe dysfunction. This is an exciting area of research that may hold promise in developing effective screening tools that can assist in the diagnosis of individuals with a history of prenatal alcohol exposure. / Thesis (Ph.D, Neuroscience Studies) -- Queen's University, 2008-08-28 15:41:20.595

Submitted to the faculty of the University Graduate School in parital fulfillment of the requirements for the degree Master of Sciences in the School of Informatics, Indiana University, August 2005

Une façon d'explorer visuellement notre monde consiste à déplacer très rapidement nos yeux pour en analyser le contenu. Dans certaines circonstances, ces mouvements oculaires, appelés saccades, peuvent perdre de leur précision. Fort heureusement notre cerveau est capable de corriger cette imprécision en ajustant progressivement la taille de ces saccades grâce à des mécanismes de plasticité cérébrale : c'est l'adaptation saccadique. L'adaptation saccadique est souvent utilisée comme modèle d'étude des mécanismes de plasticité visuo-motrice. Nous faisons également l'hypothèse qu'elle puisse servir d'outil thérapeutique. Dans cette thèse, nous nous sommes essentiellement intéressés à l'adaptation des saccades volontaires en augmentation d'amplitude chez des sujets contrôles et chez des patients souffrant d'une amputation homonyme du champ visuel (hémianopsie latérale homonyme). Les expériences 1 à 3, réalisées chez le sujet contrôle, ont permis de découvrir les repères utilisés par le cerveau pour réaliser cette adaptation sensori-motrice et coder l' environnement visuel (expérience 1 ), et les mécanismes d'adaptation saccadique quand la cible visuelle n'est pas directement codée (remapping dans l'expérience 2 et cible virtuelle dans l'expérience 3). Enfin l'expérience 4 propose une application clinique du protocole d'adaptation des anti-saccades utilisé lors de l'expérience 3, dans un but thérapeutique de rééducation comportementale de patients hémianopsiques / One way to visually explore our environment consists to rapidly displace our eyes to analyze its content. Under certain circumstances, these ocular movements called saccades can become inaccurate. Fortunately our brain is able to correct this inaccuracy by progressively adjusting the size of saccades thanks to plasticity mechanisms called saccadic adaptation. Saccadic adaptation is often used as a model to study visuo-motor plasticity. We also suggest that it could be used as a rehabilitation tool. ln this thesis, we were interested in outward adaptation of voluntary saccades in healthy subjects and patients suffering from a half visual field loss for both eyes (lateral homonymous hemianopia). Experiments 1 to 3, performed on healthy subjects, gave us opportunity to acquired complementary knowledge on the reference frame used by the brain to code its environment (experience 1) and on adaptation mechanisms when a visual target is not directly coded (remapping in experiment 2 virtual target in experiment 3). Finally, experiment 4 suggests to clinically implement the anti-saccades adaptation protocol used in experiment 3, as a new rehabilitation tool tested in hemianopie patients