Purpose: The aim of the study was to delineate differences in saccade characteristics between a population of athletes and non athletes. Aspects specifically investigated were latency, accuracy, peak velocity, and gain adaptation of saccades using both increasing and decreasing paradigms. Methods: A sample of 28 athletes (varsity badminton and squash players) and 18 non athletes (< 3 hour/week in sports) were studied. Eye movements were recorded at 120Hz using a video based eye tracker (ELMAR 2020). Each subject participated in 2 sessions on separate days. Baseline saccade responses to dot stimuli were measured in both sessions (stimulus size: 5-25 deg). The first session involved a gain decreasing paradigm, induced by displacing the stimulus backwards by 3 degrees from the initial target step (12 deg) for 500 trials. In the 2nd session a gain increase was induced by displacing the stimuli by 3 degrees in the forward direction. The latency and accuracy were calculated from the baseline. The asymptotic peak velocity was calculated from the main sequence (amplitude vs. peak velocity). The amplitude gains, calculated from the adaptation phase, were averaged for every 100 saccade responses. The averaged gains were normalized with respect to the baseline, fitted with a 3rd order polynomial, and differentiated to obtain the rate of change. Differences between the groups were compared using a regression analysis. Results: There were no significant differences in latency, accuracy, and asymptotic peak velocity between athletes and non athletes. No significant differences were seen between the two groups in the magnitude of saccadic adaptation, both for decreasing (- 15% in both groups) and increasing (athletes + 7% and non athletes + 5%) paradigms. However, athletes showed a significantly faster rate of adaptation for the gain increasing paradigm (F = 17. 96[3,6]; p = 0. 002). A significant difference was not observed in the rate of adaptation for the gain decreasing adaptation (F = 0. 856[3,6]; p = 0. 512). Conclusions: The study showed that the athletes do not respond better in terms of reaction time or accuracy of saccades. The significant difference in the rate of change of adaptation between the groups shows that online modification of saccades in the positive direction, although not greater in magnitude, occurs quicker in athletes than non athletes.

Pour percevoir le monde qui nous entoure, nous effectuons des mouvements rapides des yeux afin de placer les objets d'intérêt en fovéa, région de l'oeil où l'acuité visuelle est maximale. Ces mouvements oculaires, appelés saccades, sont précis malgré leur rapidité d'exécution. Le mécanisme assurant leur précision tout au long de la vie est l'adaptation saccadique. L'adaptation saccadique peut être facilement induite en laboratoire grâce au paradigme non invasif de double saut de la cible (McLaughlin, 1967) qui simule une « imprécision » de la visée d'une cible en déplaçant celle-ci pendant la saccade de manière répétée. Le système saccadique corrige progressivement l'erreur de visée induite artificiellement, la saccade amenant directement l'oeil vers la nouvelle position de la cible après seulement une cinquantaine d'essais. A ce jour, si les paramètres saccadiques (latence, amplitude, durée, vitesse moyenne et pic de vitesse) sont très bien documentés chez l'adulte, ils restent peu décrits chez le très jeune enfant. De plus, aucune étude n'a examiné la plasticité du système saccadique chez les enfants de moins de huit ans. Le but de ce travail de thèse est double. Il vise d'une part à caractériser les paramètres saccadiques chez le très jeune enfant. Pour ce faire, les mouvements oculaires d'un groupe de 115 bébés âgés de 7 à 42 mois ont été enregistrés pendant 140 essais (Etude 2). Nous avons mis au point un protocole expérimental original adapté à l'âge de ces jeunes participants que nous avons préalablement validé chez des adultes (Etude 1). D'autre part, nous avons étudié si la plasticité du système oculomoteur des bébés de cet âge possède les mêmes caractéristiques que celle des adultes en induisant, grâce au paradigme de double saut de la cible, une adaptation en diminution d'amplitude (Etude 3) et une adaptation en augmentation d'amplitude de la saccade (Etude 4). Les résultats reposant sur plus d'une centaine de saccades consécutives par participant montrent que les bébés sont capables de sélectionner un stimulus visuel comme cible et d'effectuer une saccade oculaire vers celle-ci. Le système oculomoteur est cependant immature à cet âge puisque les saccades des bébés ont des latences plus longues et sont plus hypométriques, i.e. moins précises que celles des adultes. Cependant, les performances saccadique des bébés s'améliorent avec l'âge pour la latence et, contre toute attente, au fur et à mesure des essais pour la précision de leur visée. Par ailleurs, les modifications adaptatives en réponse au saut intra-saccadique de la cible sont présentes chez un plus grand nombre d'adultes que d'enfants en diminution d'amplitude et inversement en augmentation d'amplitude. Cependant, l'efficacité de l'adaptation saccadique est similaire chez les deux groupes de participants. Nos études contribuent à la compréhension du développement du contrôle oculomoteur : le déclenchement de la saccade devient plus rapide (latence) avec l'âge mais la forte hypométrie de la saccade reste la même entre 7 et 42 mois. De façon inattendue, la précision saccadique s'améliore au cours de la session expérimentale suggérant une capacité d'apprentissage à court terme (Etude 2). Dans les Etudes 3 et 4, la plasticité du système oculomoteur est révélée pour la première fois chez des enfants d'âge préscolaire, signant des mécanismes adaptatifs fonctionnels chez le jeune enfant qui ne leur permettent cependant pas d'obtenir la précision saccadique des adultes. / To perceive the world around us, we perform rapid eye movements to bring objects of interest into the fovea, the eye region where visual acuity is optimal. These eye movements, called saccades, are accurate despite their high velocity. The mechanism that ensures accuracy throughout life is called saccadic adaptation. Saccadic adaptation can be easily induced in the laboratory by using the noninvasive double-step target paradigm (McLaughlin, 1967) that simulates targeting errors of the saccade by displacing repeatedly the target during the saccade. The saccadic system progressively reduces the error induced artificially so that after only fifty trials, the eyes rech the new position of the target. Today, if saccadic parameters (latency, amplitude, duration, average velocity and peak velocity) are well documented in adults, they remain poorly described in the very young children. Moreover, no study has examined the plasticity of the saccadic system in children aged under eight years-old. The goal of this thesis is twofold. On the one hand, it aims at characterizing saccadic parameters in very young children. To do this, the eye movements of a group of 115 babies aged 7-42 months-old were recorded during 140 trials (Study 2). We developed an original experimental protocol adapted to the age of these young participants, which first validated in adults (Study 1). One the other hand, we investigated whether the plasticity of the babies' oculomotor system has the same characteristics as adults' by inducing an adaptive shortening of saccade amplitude (backward adaptation; Study 3) and an adaptive lengthening of saccade amplitude (forward adaptation; Study 4). The results based on more than a hundred consecutive saccades per participant show that babies are able to select a stimulus as a visual target and generate a saccade toward it. However, the oculomotor system is immature at this age because babies' saccades have longer latencies and are more hypometric, i.e. less accurate than saccades in adults. Nevertheless, saccade latency improves with age in the child group. Unexpectedly, saccade accuracy improves over trials. Furthermore, adaptive changes in response to the intra-saccadic target step are present in a larger number of adults than children for backward adaptation and conversely for forward adaptation. However, the efficiency of saccadic adaptation is similar in the two groups of participants. Our studies allow to better understanding the development of oculomotor control: saccades are initiated faster with age but the high saccade hypometria remains the same between the age of 7 and 42 months. Unexpectedly, saccade accuracy improves over the course of the experimental session suggesting a short-term learning ability (Study 2). In Studies 3 and 4, the plasticity of the oculomotor system is revealed for the first time in preschool children. These results suggest that adaptive mechanisms are functional in young children. This ability however does not allow them to be as accurate as adults.

Suivre du regard un objet qui se déplace dans le champ visuel constitue un défi facilement relevé par le système nerveux central. Ce suivi consiste en une succession de mouvements rapides (saccades) et lents (poursuites) des yeux. La précision spatiotemporelle implique une annulation du délai entre l'activité rétinienne et la contraction des muscles extra-oculaires, et nécessite que la trajectoire de la cible soit connue et mémorisée. La question de l'élaboration de cette mémoire a été longtemps négligée, et les substrats neuronaux sous-jacents largement méconnus. L'objectif de mon travail était de mieux comprendre comment la trajectoire d'un objet est mémorisée et restituée lors du suivi oculaire d'une cible mobile. Il s'agissait en effet de caractériser comment s'opère la synergie entre les deux composantes oculaires (saccade et poursuite). Un premier versant comportemental, renseigne sur la mémorisation d'une trajectoire spatiotemporelle. Un second versant neurophysiologique, révèle le rôle du cervelet dans la restitution de cette trace mnésique. Au-delà de leur intérêt fondamental pour la neurologie, mes travaux apportent les prérequis pour accroître nos connaissances sur la mémorisation d'un évènement spatialement dynamique et pose les bases pour une compréhension neurophysiologique de la présence visuomotrice. / To track an object that moves in the visual field is a challenge easily executed by the central nervous system. This tracking consists of a succession of rapid (saccades) and slow (pursuit) eye movements. Spatiotemporal accuracy involves a cancellation of the delay between retinal activity and contraction of the extraocular muscles and requires that the trajectory of the target has been known and memorized. However, very few studies tried to explain how this memory was constructed, and the underlying neuronal substrates are largely unknown. The objective of my work was to better understand how the trajectory of an object is memorized and restored during the tracking of a moving target. The aim was to characterize the synergy between the two ocular components (saccade and pursuit). The first behavioral part of this work informs on the memorization of a spatiotemporal trajectory. The second neurophysiological part reveals the role of the cerebellum in the restitution of this memory. Beyond their fundamental interests in neurology, my work provides the prerequisites to increase our knowledge on the memorization of a spatially dynamic event.

Eyetracking applications are becoming more and more common. Applications such as monitoring a driver's focus on the road and behavior of customers in a store are just a few examples. For a long time, eye tracking has been expensive and too complex to make all kinds of applications. Thanks to the recent explosion in camera sensor technology it is possible to develop eye trackers cheaper and better. However, developing and testing these sensors requires advanced algorithms. These algorithms are then tested by a variety of people to confirm that they work. This thesis will try to see if it is possible to make robotic eyes that move like a human's eyes. This project includes a detailed process for developing a human- robotic head. Implemented movements on the robot are Saccader and smooth- pursuit with potential for Vergence movements and Vestibulo-ocular movements and microsaccades. The robot head could be used instead of a person for Eyetrackers. The report contains how the author developed the electronics to power the robotic human head. The electronics scheme is discussed and developed. The model of how the robot head and its eyes moves are explained and then implemented. The thesis also contains an explanation of the software used. With this project, it will make it easier to invent and develop good Eye trackers. / Applicationer med Eyetracking börjar bli mer och mer vanliga. Applikationer som att övervaka en chaförs fokus på vägen samt beteende hos kunder i en butik är bara ett få exempel. Under lång tid har ögonspårning varit dyrt och för komplex för att göra alla möjliga applikationer. Tack vare den senaste tidens explosion i teknik i kamerasensor går det att utveckla ögonspårare billigare och bättre. Men att utveckla och testa dessa sensorer kräver avancerade algoritmer. Dessa algoritmer testas sedan av en mängd personer för att bekräfta att de fungerar. Denna avhandling kommer att försöka se om det är möjligt att göra robotögon som rör sig som en människas ögon. Detta projekt innehåller en detaljerad process för att utveckla ett mänskligt robot huvud. Implementerade rörelser på roboten är Saccader och smoothpursuit med potentioal för Vergence-rörelser och Vestibulo-okulära rörelser och microsaccades. Robothuvudet skulle kunna användas istället för en person för Eyetrackers. Rapporten innehåller hur författaren utvecklat elektroniken för att driva det robotiska mänskliga huvudet. Elektronik-schemat diskuteras och utvecklas. Modellen av hur robothuvudet och dess ögon förklaras och sedan implementeras. I avhandlingen finns även en förklaring av den programvara som används. Med detta projekt kommer det bli lättare att ta fram och utveckla bra Eyetrackers

Alzheimer’s disease (AD) is a neurodegenerative disorder with no existing cure. Since cognitive control influences saccade behaviour, saccades provide a valuable tool when studying cognitive changes in healthy and pathological aging. This thesis aims to evaluate differences in predictive capacity and working memory between cognitively normal older adults (NC) and mild AD patients using customized saccade paradigms and a battery of neuropsychological tests. In the predictive paradigm, we hypothesize that AD participants would display a decreased level of prediction, predictive capacity and learning capacity. In the memory-guided paradigm, we hypothesize that AD participants would have a decreased ability to maintain fixation and capacity to retain information and reproduce it correctly. Overall, we found that in the predictive paradigm, NC displayed a greater degree of prediction than AD participants. However, both groups had an optimal level of prediction at intermediate inter-stimulus intervals (ISI) (750 and 1000 ms). As ISI increased, both groups, although more so in AD, elicited a greater proportion of SRTs below -200 ms and -400 ms. This may suggest that as ISI increased, participants switched from a predictive to an anticipatory/guessing strategy. At an ISI of 500 ms, NC’s learning capacity was greater than AD participants. Cognitive scores of neuropsychological tests did not correlate with learning capacity in NC. However, learning capacity in AD participants was positively correlated with working memory capacity and attentional control. The memory-guided paradigm revealed AD participants completed less viable trials, less correct trials, and had more combined directional and timing errors than NC. Cognitive correlations showed that NC’s working memory capacity positively correlated with the frequency of correct trials, whilst negatively correlating with saccade errors. Since AD participants completed 10% of viable trials correctly, the task may have been too difficult for AD participants to comprehend, rendering correlations invalid. These findings suggest that although the predictive paradigm does not solely assess for prediction, it may provide a measure to cognitively differentiate NC from AD patients, and detect AD severity. Since the memory-guided paradigm may be too difficult for AD participants, it may provide a better indicator of cognitive changes associated with healthy aging. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2013-05-21 18:54:19.492

Introduction: In gymnastics, athletes perform twisting and flipping skills at high angular velocities. These athletes rely heavily on sensory information from the visual, proprioceptive, and vestibular systems. The vestibulo-ocular reflex (VOR) is responsible for stabilizing the visual field on the retina during head movement. To accomplish this, the eyes are reflexively moved in a direction opposite the head. In a twisting gymnast, this actually reduces the ability of gymnasts to see the landing during airborne skills. Hence it becomes necessary for the gymnasts to cancel or suppress their VOR in order to view the landing. Objective: The purpose of this research is to investigate the relationship between gymnastics skill level and their ability to suppress the VOR. Methods: Ten female gymnasts (mean age 15±2.2) were obtained via a sample of convenience from a local club. The sample included both competitive and recreational gymnasts. Subjects were asked to wear a measurement system that could track head and eye movements as they performed a series of visual tasks. Three experiments were performed: (1) a saccadic experiment – two horizontally fixed LEDs (±10°) were alternately lit in a non-predictable pattern to provide visual cues, (2) a VOR experiment – the subject was asked to perform yawl head movements to an audible metronome beat 11 while visually fixating on an LED target 1m away, and (3) a vestibulo-ocular reflex suppression/cancellation (VORc) experiment – a laser pointer was fixed to the subject‟s helmet close to the cyclopean eye (slaving the target to the head movement) and the subject was again asked to perform head movements to a metronome while visually fixating on the target. In both VOR experiments, the metronome frequency varied from 72 to 196 beats per minute. Eye and head position data were synchronously sampled at 250 and 100Hz respectively. Data were post-processed using MATLAB. Periodic calibrations were performed throughout the experiment to test the continued reliability of the data. Results: Saccadic peak velocities and latencies were calculated for the sample population. Their performance did not differ from the normal population. VOR and VORc gains were also calculated and compared. The higher level (competitive) gymnasts were better at suppressing their VOR. In addition, left/right VOR gain asymmetries correlated highly with twist direction in seven of the competitive gymnasts. Discussion/Conclusions: There is a correlation between VOR performance and gymnastic level. These results do not suggest that VOR differences develop as a result of practice. These differences may simply allow some individuals to become better performers. A longitudinal study on a larger population would be required to test the causal relationship between these variables.

共著者あり。共著者名:Yoshida Toshikazu, Fukushima Kikuro. / Hokkaido University (北海道大学) / 博士 / 医学

It is essential for the brain to keep track of self-movement in order to establish a stable percept of the environment. The major source of information about self-movement is vision. However, non visual (extraretinal) information can also contribute to the sense of motion. This thesis investigated the role of extraretinal signals to account for self-generated motion in the case of eye movements. The interaction of two types of eye movements, i.e. smooth pursuit and saccades, was used to investigate the system's capacity to keep track of self-motion. This work focused in particular on the ability of the saccadic system to account for smooth pursuit eye movements in darkness. A detailed analysis of the saccade metrics allowed the identification of a novel neural mechanism for smooth eye movement integration. As a result, the saccadic system could compensate for smooth eye displacements and thus was able to ensure space constancy across different eye movements. In addition to the experimental approach of this thesis, a mathematical model was developed that described all current findings.

It is essential for the brain to keep track of self-movement in order to establish a stable percept of the environment. The major source of information about self-movement is vision. However, non visual (extraretinal) information can also contribute to the sense of motion. This thesis investigated the role of extraretinal signals to account for self-generated motion in the case of eye movements. The interaction of two types of eye movements, i.e. smooth pursuit and saccades, was used to investigate the system's capacity to keep track of self-motion. This work focused in particular on the ability of the saccadic system to account for smooth pursuit eye movements in darkness. A detailed analysis of the saccade metrics allowed the identification of a novel neural mechanism for smooth eye movement integration. As a result, the saccadic system could compensate for smooth eye displacements and thus was able to ensure space constancy across different eye movements. In addition to the experimental approach of this thesis, a mathematical model was developed that described all current findings.

Mental workload is commonly defined as the proportion of a person's total mental capacity in use at a given moment. A measure of mental workload would have utility in a number of rehabilitation medicine applications, but no method has been adequately examined for these purposes. A candidate measure is the intersaccadic interval (ISI), which is the duration between two successive saccades. Previous studies indicate that ISI length may be linked to mental workload, but this link is poorly understood for tasks that are not primarily visual. Therefore, the current study was an investigation of ISI and workload intensity in three non-visual tasks: mental arithmetic, verbal fluency, and audio perception. Workload was manipulated through changes in task difficulty as well as study participant motivation level. An analysis of eye movements and other experimental workload measures indicated a significant association between audio perceptual workload and ISI length.