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Harwood, Mark Richard. "The Fourier analysis of saccadic eye movements". Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407929.
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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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Wu, Chao-Yen. "Long-range predictors for saccadic eye movements". Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184465.
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To predict the final eye position in the middle of a saccadic eye movement will require long-range prediction. This dissertation investigated techniques for doing this. Many important results about saccadic eye movements and current prediction techinques were reviewed. New prediction techinques have been developed and tested for real saccadic data in computer. Three block processing predictors, two-point linear predictor (TPLP), five-point quadratic predictor (FPQP), and nine-point cubic predictor (NPCP), were derived based on the matrix approach. A different approach to deriving the TPLP, FPQP, and NPCP based on the difference equation was also developed. The difference equation approach is better than the matrix approach because it is not necessary to compute the matrix inversion. Two polynomial predictors: the polynomial-filter predictor 1 (PFP1), which is a linear combination of a TPLP and an FPQP, and the polynomial-filter predictor 2 (PFP2), which is a linear combination of a TPLP, and FPQP, and an NPCP, were also derived. Two recursive predictors: the recursive-least-square (RLS) predictor and the least-mean-square (LMS) predictor, were derived. Results show that the RLS and LMS predictors perform better than TPLP, FPQP, NPCP, PFP1, and PFP2 in the prediction of saccadic eye movements. A mathematical way of verifying the accuracy of the recursive-least-square predictor was developed. This technique also shows that the RLS predictor can be used to identify a signal. Results show that a sinusoidal signal can be described as a second-order difference equation with coefficients 2cosω and -1. In the same way, a cubic signal can be realized as a fourth-order difference equation with coefficients 4, -6, 4, and -1. A parabolic signal can be written as a third-order difference equation with coefficients 3, -3, and 1. And a triangular signal can be described as a second-order difference equation with coefficients 2 and -1. In this dissertation, all predictors were tested with various signals such as saccadic eye movements, ECG, sinusoidal, cubic, triangular, and parabolic signals. The FFT of these signals were studied and analyzed. Computer programs were written in systems language C and run on UNIX supported minicomputer VAX11/750. Results were discussed and compared to that of short-range prediction problems.
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Thurtell, Matthew James. "Effect of eye position on the three-dimensional kinematics of saccadic and vestibular-evoked eye movements". Thesis, The University of Sydney, 2005. http://hdl.handle.net/2123/1665.
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Saccadic and vestibular-evoked eye movements are similar in that their three-dimensional kinematic properties show eye position-dependence. When the line of sight is directed towards an eccentric target, the eye velocity axis tilts in a manner that depends on the instantaneous position of the eye in the head, with the magnitude of tilt also depending on whether the eye movement is saccadic or vestibular-evoked. The mechanism responsible for producing eye velocity axis tilting phenomena is not well understood. Some authorities have suggested that muscle pulleys in the orbit are critical for implementing eye velocity axis tilting, while others have suggested that the cerebellum plays an important role. In the current study, three-dimensional eye and head rotation data were acquired, using the magnetic search coil technique, to confirm the presence of eye position-dependent eye velocity axis tilting during saccadic eye movements. Both normal humans and humans with cerebellar atrophy were studied. While the humans with cerebellar atrophy were noted to have abnormalities in the two-dimensional metrics and consistency of their saccadic eye movements, the eye position-dependent eye velocity axis tilts were similar to those observed in the normal subjects. A mathematical model of the human saccadic and vestibular systems was utilized to investigate the means by which these eye position-dependent properties may arise for both types of eye movement. The predictions of the saccadic model were compared with the saccadic data obtained in the current study, while the predictions of the vestibular model were compared with vestibular-evoked eye movement data obtained in a previous study. The results from the model simulations suggest that the muscle pulleys are responsible for bringing about eye position-dependent eye velocity axis tilting for both saccadic and vestibular-evoked eye movements, and that these phenomena are not centrally programmed.
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Thurtell, Matthew James. "Effect of eye position on the three-dimensional kinematics of saccadic and vestibular-evoked eye movements". Faculty of Medicine, 2005. http://hdl.handle.net/2123/1665.
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Master of Science in MedicineSaccadic and vestibular-evoked eye movements are similar in that their three-dimensional kinematic properties show eye position-dependence. When the line of sight is directed towards an eccentric target, the eye velocity axis tilts in a manner that depends on the instantaneous position of the eye in the head, with the magnitude of tilt also depending on whether the eye movement is saccadic or vestibular-evoked. The mechanism responsible for producing eye velocity axis tilting phenomena is not well understood. Some authorities have suggested that muscle pulleys in the orbit are critical for implementing eye velocity axis tilting, while others have suggested that the cerebellum plays an important role. In the current study, three-dimensional eye and head rotation data were acquired, using the magnetic search coil technique, to confirm the presence of eye position-dependent eye velocity axis tilting during saccadic eye movements. Both normal humans and humans with cerebellar atrophy were studied. While the humans with cerebellar atrophy were noted to have abnormalities in the two-dimensional metrics and consistency of their saccadic eye movements, the eye position-dependent eye velocity axis tilts were similar to those observed in the normal subjects. A mathematical model of the human saccadic and vestibular systems was utilized to investigate the means by which these eye position-dependent properties may arise for both types of eye movement. The predictions of the saccadic model were compared with the saccadic data obtained in the current study, while the predictions of the vestibular model were compared with vestibular-evoked eye movement data obtained in a previous study. The results from the model simulations suggest that the muscle pulleys are responsible for bringing about eye position-dependent eye velocity axis tilting for both saccadic and vestibular-evoked eye movements, and that these phenomena are not centrally programmed.
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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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Bracewell, Robert Martyn. "On the posterior parietal cortex and saccadic eye movements". Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/12958.
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Krantz, John H. "Changes in detectability of direction and motion associated with saccadic eye movements". Gainesville, FL, 1988. http://www.archive.org/details/changesindetecta00kran.
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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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Doig, Henry Ross. "An investigation of the pre-saccadic spike potential". Thesis, Aston University, 1990. http://publications.aston.ac.uk/14625/.
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A large negative spike potential, which is closely related to the onset of saccadic eyemovements, can be recorded from electrodes adjacent to the orbits. This potential, thepresaccadic spike potential, has often been regarded as an artefact related to eyemovement recordings and little work has been performed to establish its normal waveformand parameters. A positive spike potential, exactly coincident with the frontal negativespike, has also been recorded from electrodes positioned over the posterior scalp andthere has been some debate regarding any possible relationship between the twopotentials. The frontal spike potential has been associated with motor unit activity in theextraocular muscles prior to the saccade. This thesis investigates both the large anteriorand smaller posterior spike potentials and relates these recordings to the saccadic eyemovements associated with them. The anterior spike potential has been recorded from normal subjects to ascertain its normallatency and amplitude parameters for both horizontal and vertical saccades. A relationshipbetween saccade size and spike potential amplitude is described, the spike potentialamplitude reducing with smaller saccades. The potential amplitude also reduces withadvancing age. Studying the topographical distribution of the spike potential across thescalp shows the posterior spike activity may arise from potential spread of the larger frontalspike potential. Spike potential recordings from subjects with anomalous eye movements further implicate the extraocular muscles and their innervation in the generation of the spike potential. These recordings indicate that the spike potential may have some use as a clinical recording from patients with disease conditions affecting either their extraocular muscles or the innervational pathways to these muscles. Further recordings of the potential are necessary, however, to determine the exact nature of the changes which may occur with such conditions.
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Shin, SooYoon. "Role of the primate basal ganglia in saccadic eye movements". UNIVERSITY OF PITTSBURGH, 2012. http://pqdtopen.proquest.com/#viewpdf?dispub=3485870.
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Richardson, Brian. "Smooth-pursuit and saccadic eye movements: One clock or two?" Thesis, University of Ottawa (Canada), 2008. http://hdl.handle.net/10393/27649.
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It is commonly believed that saccadic and smooth-pursuit eye movements involve different neural and behavioural organization. However, the question of how these different movements are timed with respect to a pacing goal is less understood. In two experiments, we investigated the idea that repetitive saccadic and smooth pursuit eye movements might share the same clocking mechanisms or neural networks for timing. Eye movements exhibit predictive tracking (negative latencies) at fast frequencies and reactive (positive latencies) tracking at slow frequencies. In the first experiment, monotonic changes in pacing (speeding up and slowing down) were used to establish the point at which a transition occurs between reactive and predictive behaviours. The point of transition exhibited a strong hysteresis depending on the direction of the monotonic pacing. In subsequent trials, subjects were instructed to make smooth pursuit movements up to the point of transition after which they switched to making saccades. The saccade latencies were compared between saccade-only and switched trials. Although no uniform pattern was seen across individuals, some subjects were able to track nearly identically to baseline trials after the target switch. In the second experiment, subjects were instructed to continue making saccadic eye movements after being entrained to either a saccadic or smooth pursuit stimulus train using a synchronization-continuation design. The decomposed clock and motor variance measures and correlations at higher lags showed no differences between synchronizing conditions. Our results indicate that timing is represented globally without particular reference to the effector system for broad classes of repetitive oculomotor tasks.
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Hill, Anna Christine. "Neurophysiological studies of memory-guided saccadic eye movements in man". Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322814.
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Shaunak, Sandip. "Frontal lobe and basal ganglia control of saccadic eye movements". Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299858.
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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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Hardwick, David R., i na. "Factors Associated with Saccade Latency". Griffith University. School of Psychology, 2008. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20100705.111516.
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Part of the aim of this thesis was to explore a model for producing very fast saccade latencies in the 80 to 120ms range. Its primary motivation was to explore a possible interaction by uniquely combining three independent saccade factors: the gap effect, target-feature-discrimination, and saccadic inhibition of return (IOR). Its secondary motivation was to replicate (in a more conservative and tightly controlled design) the surprising findings of Trottier and Pratt (2005), who found that requiring a high resolution task at the saccade target location speeded saccades, apparently by disinhibition. Trottier and Pratts finding was so surprising it raised the question: Could the oculomotor braking effect of saccadic IOR to previously viewed locations be reduced or removed by requiring a high resolution task at the target location? Twenty naïve untrained undergraduate students participated in exchange for course credit. Multiple randomised temporal and spatial target parameters were introduced in order to increase probability of exogenous responses. The primary measured variable was saccade latency in milliseconds, with the expectation of higher probability of very fast saccades (i.e. 80-120ms). Previous research suggested that these very fast saccades could be elicited in special testing circumstances with naïve participants, such as during the gap task, or in highly trained observers in non-gap tasks (Fischer & Weber, 1993). Trottier and Pratt (2005) found that adding a task demand that required naïve untrained participants to obtain a feature of the target stimulus (and to then make a discriminatory decision) also produced a higher probability of very fast saccade latencies. They stated that these saccades were not the same as saccade latencies previously referred to as express saccades produced in the gap paradigm, and proposed that such very fast saccades were normal. Carpenter (2001) found that in trained participants the probability of finding very fast saccades during the gap task increased when the horizontal direction of the current saccade continued in the same direction as the previous saccade (as opposed to reversing direction) giving a distinct bimodality in the distribution of latencies in five out of seven participants, and likened his findings to the well known IOR effect. The IOR effect has previously been found in both manual key-press RT and saccadic latency paradigms. Hunt and Kingstone (2003) stated that there were both cortical top-down and oculomotor hard-wired aspects to IOR. An experiment was designed that included obtain-target-feature and oculomotor-prior-direction, crossed with two gap level offsets (0ms & 200ms-gap). Target-feature discrimination accuracy was high (97%). Under-additive main effects were found for each factor, with a three-way interaction effect for gap by obtain-feature by oculomotor-prior-direction. Another new three-way interaction was also found for anticipatory saccade type. Anticipatory saccades became significantly more likely under obtain-target-feature for the continuing oculomotor direction. This appears to be a similar effect to the increased anticipatory direction-error rate in the antisaccade task. These findings add to the saccadic latency knowledge base and in agreement with both Carpenter and Trottier and Pratt, laboratory testing paradigms can affect saccadic latency distributions. That is, salient (meaningful) targets that follow more natural oculomotor trajectories produce higher probability of very fast latencies in the 80-120ms range. In agreement with Hunt and Kingstone, there appears to be an oculomotor component to IOR. Specifically, saccadic target-prior-location interacts differently for obtain-target-feature under 200-ms gap than under 0ms-gap, and is most likely due predominantly to a predictive disinhibitory oculomotor momentum effect, rather than being due to the attentional inhibitory effect proposed for key-press IOR. A new interpretation for the paradigm previously referred to as IOR is offered that includes a link to the smooth pursuit system. Additional studies are planned to explore saccadic interactions in more detail.
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Hardwick, David R. "Factors Associated with Saccade Latency". Thesis, Griffith University, 2008. http://hdl.handle.net/10072/365963.
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Part of the aim of this thesis was to explore a model for producing very fast saccade latencies in the 80 to 120ms range. Its primary motivation was to explore a possible interaction by uniquely combining three independent saccade factors: the gap effect, target-feature-discrimination, and saccadic inhibition of return (IOR). Its secondary motivation was to replicate (in a more conservative and tightly controlled design) the surprising findings of Trottier and Pratt (2005), who found that requiring a high resolution task at the saccade target location speeded saccades, apparently by disinhibition. Trottier and Pratt’s finding was so surprising it raised the question: Could the oculomotor braking effect of saccadic IOR to previously viewed locations be reduced or removed by requiring a high resolution task at the target location? Twenty naïve untrained undergraduate students participated in exchange for course credit. Multiple randomised temporal and spatial target parameters were introduced in order to increase probability of exogenous responses. The primary measured variable was saccade latency in milliseconds, with the expectation of higher probability of very fast saccades (i.e. 80-120ms). Previous research suggested that these very fast saccades could be elicited in special testing circumstances with naïve participants, such as during the gap task, or in highly trained observers in non-gap tasks (Fischer & Weber, 1993). Trottier and Pratt (2005) found that adding a task demand that required naïve untrained participants to obtain a feature of the target stimulus (and to then make a discriminatory decision) also produced a higher probability of very fast saccade latencies. They stated that these saccades were not the same as saccade latencies previously referred to as express saccades produced in the gap paradigm, and proposed that such very fast saccades were normal. Carpenter (2001) found that in trained participants the probability of finding very fast saccades during the gap task increased when the horizontal direction of the current saccade continued in the same direction as the previous saccade (as opposed to reversing direction) – giving a distinct bimodality in the distribution of latencies in five out of seven participants, and likened his findings to the well known IOR effect. The IOR effect has previously been found in both manual key-press RT and saccadic latency paradigms. Hunt and Kingstone (2003) stated that there were both cortical top-down and oculomotor hard-wired aspects to IOR. An experiment was designed that included obtain-target-feature and oculomotor-prior-direction, crossed with two gap level offsets (0ms & 200ms-gap). Target-feature discrimination accuracy was high (97%). Under-additive main effects were found for each factor, with a three-way interaction effect for gap by obtain-feature by oculomotor-prior-direction. Another new three-way interaction was also found for anticipatory saccade type. Anticipatory saccades became significantly more likely under obtain-target-feature for the continuing oculomotor direction. This appears to be a similar effect to the increased anticipatory direction-error rate in the antisaccade task. These findings add to the saccadic latency knowledge base and in agreement with both Carpenter and Trottier and Pratt, laboratory testing paradigms can affect saccadic latency distributions. That is, salient (meaningful) targets that follow more natural oculomotor trajectories produce higher probability of very fast latencies in the 80-120ms range. In agreement with Hunt and Kingstone, there appears to be an oculomotor component to IOR. Specifically, saccadic target-prior-location interacts differently for obtain-target-feature under 200-ms gap than under 0ms-gap, and is most likely due predominantly to a predictive disinhibitory oculomotor momentum effect, rather than being due to the attentional inhibitory effect proposed for key-press IOR. A new interpretation for the paradigm previously referred to as IOR is offered that includes a link to the smooth pursuit system. Additional studies are planned to explore saccadic interactions in more detail.Thesis (Masters)
Master of Philosophy (MPhil)
School of Psychology
Griffith Health
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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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Klingenhöfer, Steffen [Verfasser], i Frank [Akademischer Betreuer] Bremmer. "Perceptual stability during saccadic eye movements / Steffen Klingenhöfer. Betreuer: Frank Bremmer". Marburg : Philipps-Universität Marburg, 2012. http://d-nb.info/1028072627/34.
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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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Mitchell, Jude F. "Unity of action : coordination of movement plans between oculomotor areas /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3055792.
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Kavasakali, Maria. "Saccadic eye movement measurements in the normal eye : investigating the clinical value of a non-invasive eye movement monitoring apparatus". Thesis, University of Bradford, 2005. http://hdl.handle.net/10454/3577.
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Clinicians are becoming increasingly aware of the effect of various pathologies on the characteristics of saccadic eye movements. As such, an efficient and non-invasive means of measuring eye-movement in a clinical environment is of interest to many. The aim of this thesis is to investigate the clinical application of a non-invasive eye movement recording technique as a part of a clinical examination. Eye movements were measured using an IRIS 6500 infrared limbal eye tracker, which we customized for the direct recording of oblique eye movements as well as horizontal and vertical. Firstly, the eye-tracker itself was assessed. Visually normal observers made saccadic eye movements to a 10' stimulus in eight directions of gaze. Primary (ANOVA) and secondary analyses (mean error less than 5%) resulted in acceptance that averaging four measurements would give a representative measurement of saccadic latency, peak velocity, amplitude and duration. Test-retest results indicated that this technique gives statistically (± 1.96*STDEVDifference) repeatable responses. Several factors that could potentially influence clinically based measures of eye-movements were examined. These included, the effect of ageing, viewing distances, dioptric blur and cataract. The results showed that saccadic latency and duration are significantly (p < 0.05) longer in older (60-89 years) observers compared to younger (20-39 years). Peak velocity and amplitude were not significantly affected by the age of the observer. All saccadic parameters (SP) were significantly affected by direction (Chapter 5). The compact nature of this eye movement methodology is obtainable since there is no significant effect on viewing distance (300 cm vs. 49 cm) (Chapter 6). There is also no significant effect of dioptric blur (up to +LOODS) on any of the four SP. In contrast, a higher level of defocus (+3.O ODS) has a larger probability of interfering with the measurements of peak velocity and duration (Chapter 7). Saccadic eye-movements were also recorded whilst normally sighted subjects wore cataract simulation goggles. The results suggested that the presence of dense cataract introduces significant increases in saccadic latencies and durations. No effect was found on the peak velocities and amplitudes. The effect of amblyopia on SP was also investigated in order to examine if this methodology is able to detect normal from abnormal responses (i.e. increased saccadic latencies). This set of data (Chapter9 ) showed that using IRIS 6500, longer than normal latencies may be recorded from the amblyopic eye but no consistent effect was found for the other SP (peak velocity, amplitude, duration). Overall, the results of this thesis demonstrate that the IRIS 6500 eye-tracker has many desirable elements (it is non-invasive; comfortable for the observers and gives repeatable and precise results in an acceptable time) that would potentially make it a useful clinical tool as a part of a routine examination.
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Pearson, Benjamin Cann. "Using saccadic latency to assess traumatic brain injury". Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609562.
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Ohl, Sven. "Small eye movements during fixation : the case of postsaccadic fixation and preparatory influences". Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2014/6986/.
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Describing human eye movement behavior as an alternating sequence of saccades and fixations turns out to be an oversimplification because the eyes continue to move during fixation. Small-amplitude saccades (e.g., microsaccades) are typically observed 1-2 times per second during fixation.
Research on microsaccades came in two waves. Early studies on microsaccades were dominated by the question whether microsaccades affect visual perception, and by studies on the role of microsaccades in the process of fixation control. The lack of evidence for a unique role of microsaccades led to a very critical view on the importance of microsaccades.
Over the last years, microsaccades moved into focus again, revealing many interactions with perception, oculomotor control and cognition, as well as intriguing new insights into the neurophysiological implementation of microsaccades.
In contrast to early studies on microsaccades, recent findings on microsaccades were accompanied by the development of models of microsaccade generation. While the exact generating mechanisms vary between the models, they still share the assumption that microsaccades are generated in a topographically organized saccade motor map that includes a representation for small-amplitude saccades in the center of the map (with its neurophysiological implementation in the rostral pole of the superior colliculus).
In the present thesis I criticize that models of microsaccade generation are exclusively based on results obtained during prolonged presaccadic fixation. I argue that microsaccades should also be studied in a more natural situation, namely the fixation following large saccadic eye movements. Studying postsaccadic fixation offers a new window to falsify models that aim to account for the generation of small eye movements. I demonstrate that error signals (visual and extra-retinal), as well as non-error signals like target eccentricity influence the characteristics of small-amplitude eye movements.
These findings require a modification of a model introduced by Rolfs, Kliegl and Engbert (2008) in order to account for the generation of small-amplitude saccades during postsaccadic fixation. Moreover, I present a promising type of survival analysis that allowed me to examine time-dependent influences on postsaccadic eye movements. In addition, I examined the interplay of postsaccadic eye movements and postsaccadic location judgments, highlighting the need to include postsaccadic eye movements as covariate in the analyses of location judgments in the presented paradigm.
In a second goal, I tested model predictions concerning preparatory influences on microsaccade generation during presaccadic fixation. The observation, that the preparatory set significantly influenced microsaccade rate, supports the critical model assumption that increased fixation-related activity results in a larger number of microsaccades.
In the present thesis I present important influences on the generation of small-amplitude saccades during fixation. These eye movements constitute a rich oculomotor behavior which still poses many research questions. Certainly, small-amplitude saccades represent an interesting source of information and will continue to influence future studies on perception and cognition.Die Beschreibung des Blickbewegungsverhaltens als eine sich abwechselnde Folge von Sakkaden und Fixationen stellt eine starke Vereinfachung dar, denn auch während einer Fixation bewegen sich die Augen. Typischerweise treten Bewegungen von kleiner Amplitude (z.B. Mikrosakkaden), 1-2 mal pro Sekunde während einer Fixation auf. Frühe Studien zu Mikrosakkaden wurden von Fragen bezüglich des Einflusses von Mikrosakkaden auf die visuelle Wahrnehmung, und Studien zu der Rolle von Mikrosakkaden bei der Fixationskontrolle dominiert. Fehlende Evidenz für eine Rolle, die ausschließlich Mikrosakkaden zufällt, führten zu einer sehr kritischen Betrachtung von Mikrosakkaden. In den letzten Jahren rückten Mikrosakkaden wieder mehr in den Fokus. Vielerlei Zusammenhänge mit Wahrnehmung, okulomotorischer Kontrolle und Kognition, sowie neue Erkenntnisse bezüglich der neurophysiologischen Implementierung von Mikrosakkaden konnten aufgedeckt werden. In den letzten Jahren wurden verschiedene Modelle der Mikrosakkadengenerierung vorgestellt. Auch wenn sich diese in ihren exakten Mechanismen unterscheiden, so teilen sie doch die Annahme, dass Mikrosakkaden in einer topographisch organisierten motorischen Karte für Sakkaden ausgelöst werden. Diese Karten beinhalten eine Repräsentation für klein-amplitudige Sakkaden im Zentrum der Karte (mit dem rostralen Pol der colliculi superiores als neurophysiologische Implementierung). In der vorliegenden Arbeit kritisiere ich, dass Modelle der Mikrosakkadengenerierung ausschließlich auf Resultaten langanhaltender präsakkadischer Fixation beruhen. Ich führe an, dass Mikrosakkaden in einer natürlicheren Situation untersucht werden sollten, nämlich während der Fixation nach einer großen Sakkade. Die Untersuchung postsakkadischer Fixation bietet eine neue Möglichkeit Modelle der Mikrosakkadengenerierung zu falsifizieren. In den Studien zeige ich, dass Signale über den Fehler in der Sakkadenlandeposition (visuelle und extra-retinale), sowie fehler-unabhängige Signale, wie die Zielreiz-Exzentrizität, einen entscheidenden Einfluss auf kleine Sakkaden haben. Diese Resultate erfordern Modifikationen an dem kürzlich eingeführten Modell von Rolfs, Kliegl und Engbert (2008), um die Generierung von kleinen Sakkaden auch während der postsakkadischen Fixation erklären zu können. Darüber hinaus präsentiere ich eine viel versprechende Ereigniszeitanalyse, die uns erlaubt zeitabhängige Einflüsse auf das postsakkadische Blickbewegungsverhalten zu untersuchen. Außerdem untersuche ich das Zusammenspiel von postsakkadischen Augenbewegungen und postsakkadischen Positionsurteilen. Dabei wird die Bedeutung von postsakkadischen Augenbewegungen als Kovariate in den statistischen Analysen betont. Ein zweites Ziel dieser Arbeit besteht darin Modellvorhersagen bezüglich vorbereitender Einflüsse auf die Mikrosakkadengenerierung zu untersuchen. Die Ergebnisse, hinsichtlich eines signifikanten Einflusses des preparatory set auf die Mikrosakkadenrate unterstützt die wesentliche Modellannahme, dass erhöhte fixationsbezogene Aktivität zu einer größeren Anzahl an Mikrosakkaden führt. In der vorliegenden Arbeit präsentiere ich wichtige Einflüsse auf die Generierung von kleinen Sakkaden während der Fixation. Diese Augenbewegungen stellen ein vielseitiges okulomorisches Verhalten dar, welche weiterhin zahlreiche Fragen mit sich bringen und sicherlich zukünftige Studien zu Wahrnehmung und Kognition beeinflussen werden.
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Savina, Olga. "Effects of training to an area-cue on human saccadic eye movements". Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100209.
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Several recent studies have investigated advanced preparation of oculomotor programs after training to make saccades to a specific location in space. However, in natural visual scenes, we seldom know the precise stimulus location, rather, we often know the general area where target of interest may appear. Here, we investigated how human saccadic reaction time (SRT) and saccade final landing position may be affected by training to attend to an area where a target will appear. Additionally, we looked at how training to an area of one size may influence eye movements to targets presented in a larger area. Subjects were trained to attend to an area-cue of 6° in diameter, always presented in the same quadrant of the visual field, at the same spatial coordinates. During training, targets were presented at random locations inside the cued area. After training, targets were presented inside an area-cue (except for a few catch trials) of either the same size or of a larger size (i.e. 10° diameter). Results show that training-related saccades were directed toward individually distinctive preferred regions inside the trained area, and towards identical regions in relative coordinates inside the larger 10° area. Importantly, training-related saccades were mostly in the anticipatory range, a large proportion of which was followed by the corrective second saccades directed towards the target. Our findings suggest that anticipatory saccades should be considered in the assessment of training-related changes in oculomotor preparation of saccadic programming.
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Gilman, Elizabeth R. "Towards an eye-movement model of music sight-reading". Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342467.
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Mezey, Laura Elisabeth. "The adaptive control of saccades in normal and abnormal children and adults". Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343722.
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Taylor, Kathleen. "Computational modelling of the contribution of posterior parietal cortex to saccadic eye movements". Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302125.
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Bell, Paul. "The use of saccadic eye movements in the clinical psychopharmacology of psychotropic drugs". Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261766.
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Turner, Travis Henry. "Validation of a new method for neurobehavioral testing of oculomotor function". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3259051.
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Thesis (Ph. D.)--University of California, San Diego and San Diego State University, 2007.Title from first page of PDF file (viewed June 11, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 171-178).
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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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Unsworth, David I. "Working memory capacity and the control of saccades : individual differences in executive control". Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/30980.
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Ryan, Suzanne. "The role of the posterior parietal cortex in the planning of saccadic eye movements". Thesis, University of Nottingham, 2007. http://eprints.nottingham.ac.uk/10290/.
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This thesis aimed to investigate the role of posterior parietal cortex (PPC) in relation to saccade planning and more specifically the spatial remapping processes essential to this behaviour. These experiments begin through the use of transcranial magnetic stimulation (TMS) on a version of the classic double-step saccade paradigm (Chapter 2). TMS was not found to disrupt spatial remapping on this task and a potential explanation for this in terms of task specifications was proposed. In Chapter 4 this theme was explored further through a series of variations on the double-step saccade task, in which the order of target presentation was manipulated; these led to the conclusion that both target encoding and spatial remapping are influenced by such task-related factors. In Chapter 3, a second set of TMS experiments is discussed, which investigated the updating of saccade plans in response to a change in target location, rather than eye position. Finally in Chapters 5 and 6 neuroimaging studies that aimed to evaluate the cortical areas involved in these processes are discussed. The first of these (Chapter 5) was an extension of the behavioural studies previously conducted in Chapter 4. The second employed a novel saccade paradigm to investigate the effect of intervening saccades made between the time of target encoding and execution (Chapter 6). The findings from these experiments supported the idea that the PPC is important for representing saccade goals and updating these following a change in the spatial relationship between the centre of gaze and the target location for a future saccade. In Chapter 7 the findings from the aforementioned studies were discussed in relation to current debate within this area of research, concerning in particular the functional significance of saccade-related neuronal activity in PPC, as were suggestions for future studies that might help provide further insight into these issues.
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Sommer, Marc A. (Marc Alois). "The role of frontal cortex in the generation of saccadic eye movements and fixation". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/32678.
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Campbell, Pauline Elizabeth. "The utility of the auditory brainstem response in children with atypical saccadic eye movements". Thesis, University of Plymouth, 2014. http://hdl.handle.net/10026.1/2931.
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Lesions in the brainstem result in widespread damage to a number of sensorimotor systems including oculomotor and auditory neural circuits. Although these systems are spatially separate and highly specialised, they are also co-located. This thesis, investigates whether lesions in the oculomotor system will also cause co-morbid dysfunction in the auditory pathways. Specifically, we investigated the usefulness of the Auditory Brainstem Response (ABR) in two oculomotor conditions: slow saccades in Gaucher disease (GD) and opsoclonus in Dancing Eye Syndrome (DES). We present four empirical studies. In our first study we systematically investigated the ABR in GD. We found that multimodal testing can better delineate underlying neurological deficits in neuronopathic GD (nGD) and distinguish between phenotypes. In the second study we examined the ABR's utility as a longitudinal, objective marker of disease burden and in a randomised clinical control trial. ABRs continued to deteriorate regardless of treatment. In our third study we assessed audiological function in DES. We found that at least 43% of DES patients have hyperacusis. We also found subtle abnormalities in the auditory brainstem, as shown by the ABR. Our final study explored the onset-offset response in the ABR and assessed its utility as a clinical marker. Overall, this thesis provides new evidence that auditory pathways are also affected in diseases which are traditionally assumed to be ‘oculomotor’ in nature. We believe that there is sufficient evidence to warrant the inclusion of audiological testing, such as the ABR, as part of the standard assessment of newly diagnosed GD patients and that they undergo these tests prior to commencing treatment. These tests may also have a wider application as longitudinal outcome measures for use in clinical trials or as markers of neurological burden in GD and we believe may be useful in other metabolic diseases; we found that current therapies for GD have low efficacy. Understanding the underlying neurological deficits in these debilitating illnesses can only help to improve treatments and the long-term outlook for these patients.
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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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Farber, Robert H. "Ocular motor system functioning in obsessive-compulsive disorder and Tourette syndrome /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9917950.
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Manca, Giulia [Verfasser], i Heiner [Akademischer Betreuer] Deubel. "Dynamical and metrical adaptation of saccadic eye movements in humans / Giulia Manca ; Betreuer: Heiner Deubel". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2021. http://d-nb.info/1241963789/34.
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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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Berry, Donna M. "The contributions of inhibitory control, attention and working memory to the control of saccadic eye movements". Thesis, Lancaster University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618555.
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It has been suggested that control over saccadic eye movements represents cognitive proficiency. but the precise cognitive mechanisms underpinning saccades are unclear. This thesis aims to elucidate the mechanisms controlling the accuracy, validity and latencies of prosaccades and antisaccades. Experiment I assessed the role of working memory in determining antisaccade latencies and errors, by measuring the impact of imposing a task-relevant, concurrent load. It was found that reducing available working memory for saccades comparably impeded prosaccade and antisaccade performance. This suggests that, contrary to earlier indications, working memory capacity is not a specific determinant of antisaccade latencies or errors. Experiment 2 systematically varied concurrent working memory load in prosaccade and antisaccade tasks, whilst eliminating potentially confounding attentional factors. The results confirmed the minor role played by working memory in the control of antisaccades: when attentional factors were eliminated, the effects previously misattributed to working memory were abolished. Experiment 3 assessed the relative contributions of working memory and inhibitory control, and revealed that antisaccades are more reliant upon an inhibitory mechanism, particularly in older adults. In Experiment 4, the previously documented decline in this inhibitory mechanism with age was unpacked. Inhibitory control was temporally segregated into covert inhibition of attention and overt inhibition of saccades. The results suggested that it is only when covert and overt inhibition are required simultaneously, as in the standard antisaccade task, that older adults exhibit notably poorer performance, since older adults demonstrated a selective decline in overt inhibitory control. Finally, Experiment 5 tested competitive programming models of antisaccades, which predict that performance is largely determined by the relative programming speed of prosaccades, but found no support for such models. Taken together, these results suggest that visual attention, covert and overt inhibition, and working memory capacity all contribute to the cognitive control of saccadic eye movements.
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Alhazmi, Mohammed. "Effect of ocular rigidity upon the dynamic characteristics of saccadic, smooth pursuit and disparity vergence eye movements". Thesis, Glasgow Caledonian University, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676478.
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Eye movements are important to fixate or track an object of interest in the visual field. Eye movements are coordinated by six extraocular muscles (EOM) [1, 2]. These EOMs are responsible for ensuring that the visual axes of both eyes are parallel to each other [1, 2]. The effect of variation in refractive error upon eye movements has not received the same attention in the literature as the sensory aspect. Axial length varies considerably with refractive error [3-8]. Subjects with myopia have been found to have considerably larger eyes, with a longer axial length and lower ocular rigidity [3-5, 7, 8], compared to subjects who are emmetropic or hyperopic [3, 4, 6, 9]. It has also been shown that subjects with hyperopia have significantly smaller eyes with shorter axial lengths [6] and higher ocular rigidity [9]. Despite these marked differences in the physical characteristics of the eye between subjects, little work has been done to examine whether axial length or ocular rigidity influences eye movement response characteristics. The effect of variations in the structural characteristics of the eye upon the eye movement characteristics were explored in this PhD work by measuring eye movements under a number of experimental saccadic, smooth pursuit and vergence paradigms in 93 young visually normal subjects. This thesis showed that the characteristics of saccadic eye movements varied systematically with ocular rigidity. Subjects with lower ocular rigidity (always myopic) produced saccades with significantly slower peak velocity and a longer time to peak velocity. Conversely, subjects with high ocular rigidity (hyperopic) produced saccades with significantly faster peak velocity and a shorter time to peak velocity compared to both emmetropes (medium ocular rigidity) and myopes. Smooth pursuit responses to sinusoidal stimulus movement also varied significantly with ocular rigidity. Subjects with lower ocular rigidity (myopic) showed significantly lower response gain and larger phase lag. Hyperopes showed significantly more accurate responses with higher response gain and lower phase lag compared to emmetropes and myopes. Disparity vergence responses to a sinusoidal moving 3D stimulus varied systematically with ocular rigidity. The high ocular rigidity hyperopic eyes showed significantly higher response gain and lower phase lag than the other two refractive groups. The low ocular rigidity myopic eyes exhibited significantly lower response gain and longer phase lag than the medium ocular rigidity emmetropic eyes. The viewing time has a significant influence upon response quality as both response gain and phase lag deteriorates significantly over a very short period of time. In conclusion, it has been shown in this thesis and for the first time that the dynamic characteristics of saccadic, smooth pursuit and disparity vergence eye movements vary systematically with the structural characteristics of the globe. The results of this work provide substantial evidence of the influence of ocular rigidity upon the characteristics of eye movements.
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Gregory, Nicola Jean. "The influence of socio-biological cues on saccadic orienting". Thesis, University of Exeter, 2011. http://hdl.handle.net/10036/3231.
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Previous research has suggested that viewing of another’s averted eye gaze causes automatic orienting of attention and eye movements in observers due to the importance of eye gaze for effective social interaction. Other types of visual cues with no social or biological relevance, such as arrows, are claimed not to produce such a direct effect on orienting behaviour. The finding that processing of eye gaze is reduced in individuals with Autistic Spectrum Disorders as well as following damage to the orbitofrontal cortex of the brain, suggests that gaze processing is indeed critical for effective social behaviour and therefore eye gaze may constitute a “special” directional cue. This thesis tested these ideas by examining the influence of socio-biological (eye gaze and finger pointing) and non-social cues (arrows and words) on eye movement responses in both healthy control participants and those with damage to the frontal lobes of the brain. It further investigated the relationship between orienting to gaze and arrow cues and autistic traits in a healthy population. Important differences between the effects of socio-biological and non-social cues were found on saccadic eye movements. Although in the pro-saccade tasks, arrow cues caused a similar facilitation of responses in the cued direction as eye gaze and pointing cues, in the anti-saccade tasks (in which participants have to respond away from the location of a peripheral onset), arrows had a greatly reduced effect on oculomotor programming relative to the biologically relevant cues. Importantly, although the socio-biological cues continued to influence saccadic responses, the facilitation was in the opposite direction to the cues. This finding suggests that the cues were being processed within the same "anti-response" task set (i.e. "go opposite") as the target stimulus. Word cues had almost no effects on saccadic orienting in either pro- or anti-saccade tasks. Schematicised eye gaze cues had a smaller magnitude effect than photographic gaze cues suggesting that ecological validity ("biological-ness") is an important factor in influencing oculomotor responses to social cues. No relationship was found between autistic traits and orienting to gaze or arrow cues in a large sample of males. However, findings from the neurological patients point to a possible double-dissociation between the neural mechanisms subserving processing of socio-biological and non-social cues, with the former reliant on the orbitofrontal cortex, and the latter on lateral frontal cortex. Taken together, these results suggest that biologically relevant cues have privileged access to the oculomotor system. The findings are interpreted in terms of a neurocognitive model of saccadic orienting to socio-biological and non-social cues, and an extension to an existing model of saccade generation is proposed. Finally, limitations of the research, its wider impact and directions for future work are discussed.
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Coughlin, Michael J., i n/a. "Calibration of Two Dimensional Saccadic Electro-Oculograms Using Artificial Neural Networks". Griffith University. School of Applied Psychology, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030409.110949.
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The electro-oculogram (EOG) is the most widely used technique for recording eye movements in clinical settings. It is inexpensive, practical, and non-invasive. Use of EOG is usually restricted to horizontal recordings as vertical EOG contains eyelid artefact (Oster & Stern, 1980) and blinks. The ability to analyse two dimensional (2D) eye movements may provide additional diagnostic information on pathologies, and further insights into the nature of brain functioning. Simultaneous recording of both horizontal and vertical EOG also introduces other difficulties into calibration of the eye movements, such as different gains in the two signals, and misalignment of electrodes producing crosstalk. These transformations of the signals create problems in relating the two dimensional EOG to actual rotations of the eyes. The application of an artificial neural network (ANN) that could map 2D recordings into 2D eye positions would overcome this problem and improve the utility of EOG. To determine whether ANNs are capable of correctly calibrating the saccadic eye movement data from 2D EOG (i.e. performing the necessary inverse transformation), the ANNs were first tested on data generated from mathematical models of saccadic eye movements. Multi-layer perceptrons (MLPs) with non-linear activation functions and trained with back propagation proved to be capable of calibrating simulated EOG data to a mean accuracy of 0.33° of visual angle (SE = 0.01). Linear perceptrons (LPs) were only nearly half as accurate. For five subjects performing a saccadic eye movement task in the upper right quadrant of the visual field, the mean accuracy provided by the MLPs was 1.07° of visual angle (SE = 0.01) for EOG data, and 0.95° of visual angle (SE = 0.03) for infrared limbus reflection (IRIS®) data. MLPs enabled calibration of 2D saccadic EOG to an accuracy not significantly different to that obtained with the infrared limbus tracking data.
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Coughlin, Michael J. "Calibration of Two Dimensional Saccadic Electro-Oculograms Using Artificial Neural Networks". Thesis, Griffith University, 2003. http://hdl.handle.net/10072/365854.
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The electro-oculogram (EOG) is the most widely used technique for recording eye movements in clinical settings. It is inexpensive, practical, and non-invasive. Use of EOG is usually restricted to horizontal recordings as vertical EOG contains eyelid artefact (Oster & Stern, 1980) and blinks. The ability to analyse two dimensional (2D) eye movements may provide additional diagnostic information on pathologies, and further insights into the nature of brain functioning. Simultaneous recording of both horizontal and vertical EOG also introduces other difficulties into calibration of the eye movements, such as different gains in the two signals, and misalignment of electrodes producing crosstalk. These transformations of the signals create problems in relating the two dimensional EOG to actual rotations of the eyes. The application of an artificial neural network (ANN) that could map 2D recordings into 2D eye positions would overcome this problem and improve the utility of EOG. To determine whether ANNs are capable of correctly calibrating the saccadic eye movement data from 2D EOG (i.e. performing the necessary inverse transformation), the ANNs were first tested on data generated from mathematical models of saccadic eye movements. Multi-layer perceptrons (MLPs) with non-linear activation functions and trained with back propagation proved to be capable of calibrating simulated EOG data to a mean accuracy of 0.33° of visual angle (SE = 0.01). Linear perceptrons (LPs) were only nearly half as accurate. For five subjects performing a saccadic eye movement task in the upper right quadrant of the visual field, the mean accuracy provided by the MLPs was 1.07° of visual angle (SE = 0.01) for EOG data, and 0.95° of visual angle (SE = 0.03) for infrared limbus reflection (IRIS®) data. MLPs enabled calibration of 2D saccadic EOG to an accuracy not significantly different to that obtained with the infrared limbus tracking data.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Applied Psychology
Griffith Health
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Buonocore, Antimo. "Remote distractor effects in saccadic, manual and covert attention tasks". Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/5850.
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The Remote Distractor Effect (RDE) is a robust phenomenon where a saccade to a lateralised target is delayed by the appearance of a distractor in the contralateral hemifield (Walker, Kentridge, & Findlay, 1995). The main aim of this thesis was to test whether the RDE generalises to response modalities other then the eyes. In Chapter 2, the RDE was tested on saccadic and simple manual keypress responses, and on a choice discrimination task requiring a covert shift of attention. The RDE was observed for saccades, but not simple manual responses, suggesting that spatially oriented responses may be necessary for the phenomenon. However, it was unclear whether distractor interference occurred in the covert task. Chapter 4 compared the effects of distractors between spatially equivalent tasks requiring saccadic and manual aiming responses respectively. Again, the RDE was observed for the eyes but not for the hands. This dissociation was also replicated in a more naturalistic task in which participants were free to move their eyes during manual aiming. In order to examine the time-course of distractor effects for the eyes and the hands, a third experiment investigated distractor effects across a wider range of target-distractor delays, finding no RDE for manual aiming responses at distractor delays of 0, 100, or 150 ms. The failure of the RDE to generalise to manual aiming suggests that target selection mechanisms are not shared between hand and eye movements. Chapter 5 further investigated the role of distractors during covert discrimination. The first experiment showed that distractor appearance did not interfere with discrimination performance. A second experiment, in which participants were also asked to saccade toward the target, confirmed the lack of RDE for covert discrimination while saccades were slower in distractor trials. The dissociation between covert and overt orienting suggests important differences between shifts of covert attention and preparation of eye movements. Finally, Chapter 6 investigated the mechanism driving the RDE. In particular it was assessed whether saccadic inhibition (Reingold & Stampe, 2002) is responsible for the increase in saccadic latency induced by remote distractors. Examination of the distributions of saccadic latencies at different distractor delays showed that each distractor produced a discrete dip in saccadic frequency, time-locked to distractor onset, conforming closely to the character of saccadic inhibition. It is concluded that saccadic inhibition underlies the remote distractor effect.
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Istvan, Peter John. "The intrinsic organization and characteristics of neurons in monkey superior colliculus and their role in saccadic eye movements". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq22467.pdf.
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Munro, N. A. R. "The control of saccadic and smooth pursuit eye movements in patients with lesions of the central nervous system". Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319050.
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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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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.