Dissertations / Theses on the topic 'Vision – Physiology'
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1
Huang, Pi-Chun 1975. "The properties of collinear facilitation in human vision /." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103201.
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The detection threshold of a luminance-defined Gabor is improved by two high contrast, aligned flanking Gabors, an effect termed collinear facilitation. However, the neural basis of collinear facilitation is not well understood. This thesis focuses on a number of issues in collinear facilitation to better our understanding of its neural basis. (1) Cortical sites: the cortical site of collinear facilitation was investigated, and results showed that collinear facilitation is a purely monocular phenomenon. (2) Temporal properties: Collinear facilitation has fast dynamics for initiation and once collinear facilitation occurs it either decays slowly or is associated with a sustained detection. (3) Selectivity to other types of stimuli: chromatic stimuli (which isolated the S-cone opponent and the L/M cone opponent mechanisms) and 2nd order stimuli (a 2D white noise or ID noise multiplied with a Gabor envelope) were used and the results showed that collinear facilitation occurs in chromatic processing, and that some 2nd order stimuli also exhibit collinear facilitation. However, there was no interaction between luminance and chromatic systems nor between 1st and 2nd order mechanisms, suggesting independent processing streams for collinear facilitation. All of these results supported the conclusion that collinear facilitation is not a general property of cortical neurons in V1 since most V1 neurons are binocular, sensitive to both chromatic and achromatic stimuli and sensitive to both 1 st and 2nd order stimuli. Furthermore, the temporal properties of collinear facilitation suggest complex dynamic interactions, not simply explained by the passive propagation of long-range recurrent intra-cortical connections between flanks and target.
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Wichmann, Felix A. "Some aspects of modelling human spatial vision : contrast discrimination." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302262.
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Wilkins, Luke. "Vision testing and visual training in sport." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6313/.
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This thesis examines vision testing and visual training in sport. Through four related studies, the predictive ability of visual and perceptual tests was examined in a range of activities including driving and one-handed ball catching. The potential benefits of visual training methods were investigated (with particular emphasis on stroboscopic training), as well as the mechanisms that may underpin any changes. A key theme throughout the thesis was that of task representativeness; a concept by which it is believed the more a study design reflects the environment it is meant to predict, the more valid and reliable the results obtained are. Chapter one is a review of the literature highlighting the key areas which the thesis as a whole addresses. Chapter’s two to five include the studies undertaken in this thesis and follow the same format each time; an introduction to the relevant research, a methods section detailing the experimental procedure, a results section which statistically analysed the measures employed, and a discussion of the findings with reference to the existing literature. Finally, in chapter six the strengths and limitations of the thesis are considered, before suggestions are made for future studies, and concluding remarks made.
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Bäckman, Örjan. "Re-establishing reading skills of elderly low vision patients : studies on Swedish low vision clinic clients /." Stockholm, 2000. http://diss.kib.ki.se/2000/91-628-4577-2/.
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Gianna, Claire Cecile. "Otolith function in human subjects : perception of motion, reflex eye movements and vision during linear interaural acceleration." Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267886.
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Foulder-Hughes, Lynda Ann. "Motor function, vision, and growth, in main stream school children born at or below 32 weeks' gestation." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369049.
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Link, Norah K. "Curvature cues and discontinuity detection in early orientation selection." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66000.
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Knott, Benjamin. "Intraspecific variation in avian colour vision, and the effects of diet on avian visual physiology." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.685420.
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Avian vision is highly developed and complex. Avian retinas contain rod and double cone photoreceptors, and four classes of single cones. Single cones are sensitive to red, green, blue, and violet/ultraviolet wavelengths, producing, it seems, tetrachromatic colour vision. All cones contain an oil droplet, rich in carotenoid pigments. These droplets act as selective filters, substantially modifying light detected by the photoreceptor. Using dietary carotenoid manipulations, the effects of carotenoid availability on oil droplet absorbance properties were tested in two species: the zebra finch and the crimson rosella parrot. Microspectrophotometry was used to determine whether these manipulations affected oil droplet carotenoid concentration, a change that could alter the colour discrimination ability of birds, with consequences for individual behaviour and ecology. Oil droplet concentration was determined by measuring the cut-off wavelength at which no more light is transmitted. Significant increases concentration were found in carotenoid supplemented birds, but only in one droplet type not affecting colour vision. Analysis also revealed the effect sizes resulting from the manipulation were dependent on retinal location. These results reveal a response to dietary manipulation that potentially preserves spectral tuning of colour vision, and could also provide insights into the development of these droplets in the retina. In the zebra finch, additional measures of plumage spectra and immunocompetence were taken to assess the trade-off of carotenoid resources used in vision with those needed for other carotenoid dependent systems, but these studies were inconclusive. Intraspecific variation in visual physiology is a phenomenon known in fish and mammals, but currently unreported in birds. The oil droplets of green and blue budgerigars were measured to test for a relationship between plumage pigmentation and droplet absorbance. No relationship was found, but the spatial variation in oil droplet absorbance within the retina was notably similar to the spatial variation in crimson rosella. The visual pigments and opsins of the crimson rosella were characterised using micro spectrophotometry and molecular techniques, which revealed unusual features in RH 1 and RH2 opsins that were previously unknown in any vertebrate opsin.
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Suaning, Gregg J????rgen Graduate School of Biomedical Engineering Faculty of Engineering UNSW. "Engineering and acute physiological testing of a retinal neurostimulator." Awarded by:University of New South Wales. Graduate School of Biomedical Engineering, 2003. http://handle.unsw.edu.au/1959.4/19203.
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Electrical stimulation of retinal neurons is known to elicit visual sensations. When applied to the retina in a spatial pattern, electrical stimulation may be capable of providing rudimentary patterned vision that may be of benefit to sufferers of degenerative retinal disorders. No such device has yet been devised to provide for chronic study of the psychophysical perceptions elicited from a prosthesis for retinal stimulation. In this study, steps towards achieving this goal have been successfully carried out. Foregoing research was reviewed such that appropriate stimulation parameters were incorporated in the design of a 100 stimulation channel, complimentary metal oxide semiconductor (CMOS) integrated circuit, small enough in size so as to be capable of being implanted within the ocular anatomy or surrounding orbit. The device, and its associated external hardware and software were designed, modeled, fabricated, and interfaced with stimulating electrodes in acute testing in a highorder mammal (Ovis aries) so as to assess the capabilities of the device to elicit cortical potentials as a direct result of stimulation of the neural retina. Testing was performed under conditions similar to those anticipated in chronic in-situ configurations wherein radio-frequency telemetry was used to deliver power and configuration parameters to the device thus avoiding the passage of wires through tissue in order to communicate to the implant circuit. The results of the testing indicate that the circuit is indeed capable of eliciting physiological responses in the animal and evidence is present that these responses could be elicited in patterned form. Further work undertaken includes the development of surgical methods for implantation, and application of the prosthesis circuit in functional electronic stimulation.
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Mareschal, Isabelle. "Neuronal processing of second-order stimuli." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35913.
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The detection of visual stimuli involves neurons which are selectively responsive to components of a visual scene. In the early stages of visual processing, it is commonly accepted that neurons respond to the changes in luminance associated with objects and object boundaries. However, recent experiments have demonstrated that some neurons can also respond to features which are not defined by luminance variations. These features are termed "second-order" because they require more complex processing, and neurons which respond to second-order features are necessarily nonlinear.In this thesis, I undertook a three dimensional physiological characterization (i.e. tuning of orientation, spatial frequency and temporal frequency) of such nonlinear neurons in order to shed light on their processing capabilities. In particular we sought to address the following issues: (1) whether the temporal and spatial properties underlying second-order motion are similar to those underlying luminance based ("first-order") motion; (2) whether these properties remain constant using different types of second-order stimuli, suggesting that neurons' responses are invariant to the physical attributes comprising the stimulus; and (3) whether second-order processing is a cortical mechanism or can occur at an earlier stage of the visual system (e.g. in the lateral geniculate nucleus). Taken together these results have a dual function; they provide insight into the complex cellular processing of higher order features, and they provide a general framework for the generation of second-order models.
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Nieman, Chelsey L. "Visual Ecology of Lake Erie Fishes: An Investigation of the Impacts of ElevatedTurbidity on Vision." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555421470203573.
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Kotynski, Anne Elizabeth. "The Impact of Global Versus Local Visual Attention on Auditory Perception." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1565380220244836.
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Venkatesh, Aditya. "Activation of mTORC1 Improves Cone Cell Metabolism and Extends Vision in Retinitis Pigmentosa Mice: A Dissertation." eScholarship@UMMS, 2016. https://escholarship.umassmed.edu/gsbs_diss/822.
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Retinitis Pigmentosa (RP) is an inherited photoreceptor degenerative disease that leads to blindness and affects about 1 in 4000 people worldwide. The disease is predominantly caused by mutations in genes expressed exclusively in the night active rod photoreceptors; however, blindness results from the secondary loss of the day active cone photoreceptors, the mechanism of which remains elusive. Here, we show that the mammalian target of rapamycin complex 1 (mTORC1) is required to delay the progression of cone death during disease and that constitutive activation of mTORC1 is sufficient to maintain cone function and promote cone survival in RP. Activation of mTORC1 increased expression of genes that promote glucose uptake, retention and utilization, leading to increased NADPH levels; a key metabolite for cones. This protective effect was conserved in two mouse models of RP, indicating that the secondary loss of cones can be delayed by an approach that is independent of the primary mutation in rods. However, since mTORC1 is a negative regulator of autophagy, its constitutive activation led to an unwarranted secondary effect of shortage of amino acids due to incomplete digestion of autophagic cargo, which reduces the efficiency of cone survival over time. Moderate activation of mTORC1, which promotes expression of glycolytic genes, as well as maintains autophagy, provided more sustained cone survival. Together, our work addresses a long-standing question of non-autonomous cone death in RP and presents a novel, mutation-independent approach to extend vision in a disease that remains incurable.
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Venkatesh, Aditya. "Activation of mTORC1 Improves Cone Cell Metabolism and Extends Vision in Retinitis Pigmentosa Mice: A Dissertation." eScholarship@UMMS, 2004. http://escholarship.umassmed.edu/gsbs_diss/822.
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Retinitis Pigmentosa (RP) is an inherited photoreceptor degenerative disease that leads to blindness and affects about 1 in 4000 people worldwide. The disease is predominantly caused by mutations in genes expressed exclusively in the night active rod photoreceptors; however, blindness results from the secondary loss of the day active cone photoreceptors, the mechanism of which remains elusive. Here, we show that the mammalian target of rapamycin complex 1 (mTORC1) is required to delay the progression of cone death during disease and that constitutive activation of mTORC1 is sufficient to maintain cone function and promote cone survival in RP. Activation of mTORC1 increased expression of genes that promote glucose uptake, retention and utilization, leading to increased NADPH levels; a key metabolite for cones. This protective effect was conserved in two mouse models of RP, indicating that the secondary loss of cones can be delayed by an approach that is independent of the primary mutation in rods. However, since mTORC1 is a negative regulator of autophagy, its constitutive activation led to an unwarranted secondary effect of shortage of amino acids due to incomplete digestion of autophagic cargo, which reduces the efficiency of cone survival over time. Moderate activation of mTORC1, which promotes expression of glycolytic genes, as well as maintains autophagy, provided more sustained cone survival. Together, our work addresses a long-standing question of non-autonomous cone death in RP and presents a novel, mutation-independent approach to extend vision in a disease that remains incurable.
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Gardiner, Jayne M. "Multisensory Integration in Shark Feeding Behavior." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4046.
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Multimodal sensory input directs simple and complex behaviors in animals. Most research to date has been limited to studies of individual senses rather than multiple senses working together, leading to important advances in our comprehension of the sensory systems in isolation, but not their complementary and alternative roles in difficult behavioral tasks, such as feeding. In the marine environment, a prey item might emit an odor, create a hydrodynamic disturbance, such as from gill movements or swimming, be visible to the predator, produce a sound, and/or produce a weak electrical field. Therefore, the goal of this study was to investigate the integration of olfaction, mechanoreception by the lateral line system, vision, and electroreception in a marine animal. Sharks were chosen as a model organism in which to investigate multisensory integration because of their sensitivity and acuity, the presence of the same suite of sensory modalities in all species, the availability of experimental animals from different species, habitats and ecologies, and the rich literature on sharks' prey capture behavior. Two approaches were used: controlled artificial stimuli, delivered to the animals, were used to determine the spatial and concentration characteristics of odor encounters that guide the initial orientation to an odor plume in the far field in a model elasmobranch, the smooth dogfish, Mustelus canis; and sensory deprivation was used to restrict the availability of natural cues emanating from live prey items in order to elucidate the complementary and alternating roles of the senses in detecting, tracking, orienting to, striking at, and ultimately capturing prey. In the latter experiments, three species of sharks from different ecological niches were investigated: benthic, suction-feeding nurse sharks (Ginglymostoma cirratum) that hunt nocturnally for fish; ram-biting bonnetheads (Sphyrna tiburo) that scoop crustaceans off the bottom of seagrass beds; and ram-feeding blacktip sharks (Carcharhinus limbatus) that rapidly chase down midwater teleost prey. In orienting to odor patches, bilateral time differences between the nares are more important than concentration differences, such that animals turn toward the side stimulated first, even with delayed pulses of higher concentration. This response would steer the shark into each oncoming odor patch, helping the animal maintain contact with an odor plume. Sensory deprivation experiments revealed similarities and differences among species in terms of which senses they choose to focus on for particular behaviors, likely as a result of differences in the environments that they hunt in, type of prey consumed, and foraging strategies used, as well as anatomical differences in the central nervous system and the sensory organs. In most cases, multiple senses can be used for the same behavioral task. Thus, sharks are capable of successfully capturing prey, even when the optimal sensory cues are unavailable, by switching to alternative sensory modalities, which indicates that feeding behavior is plastic. Nurse sharks rely primarily on olfaction for detection. Olfaction in combination with vision, the lateral line, or touch is required for tracking. Nurse sharks orient to prey using the lateral line, vision, or electroreception, but will not ingest food if olfaction is blocked. Capture is mediated by the electrosensory system or tactile cues. Bonnetheads normally detect prey using olfaction, rely on olfactory-based tracking until they are close to the prey, then vision to line up a strike, and finally electroreception to time the jaw movements for capture. They can detect, orient, and strike visually in the absence of olfactory cues. Blacktip sharks also detect prey using olfaction or vision. Olfaction is used in combination with vision or the lateral line system for tracking. Long-distance orientation and striking is visually mediated, but strike precision relies on lateral line cues and an increase in misses occurs when this system is blocked. In the absence of vision, short-range orientation and striking can occur using lateral line cues. Capture is mediated by electroreception or tactile cues. Collectively, these results were used to develop species-specific sensory hierarchies for shark feeding behavior in a captive environment, the first such hierarchies to cover a complete behavioral sequence in a vertebrate.
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Hasenei, Aaron. "Ecophysiology of lionfish metabolic and visual systems: Are there physiological limits to inshore invasion?" Thesis, NSUWorks, 2018. https://nsuworks.nova.edu/occ_stuetd/496.
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Lionfish (Pterois spp.), an invasive species native to the Indo-Pacific, have permanently established themselves throughout the greater Caribbean, Gulf of Mexico, and regions of the Western Atlantic ranging from as far north as North Carolina to central Brazil. As their fundamental range expands, lionfish threaten to migrate into estuarine environments as they have been found to tolerate low salinities and an eclectic range of temperatures. The physiological capacity of invasion was assessed by quantifying the visual ecology of lionfish utilizing corneal electroretinography (ERG) as well as their metabolic scope and hypoxia tolerances under various temperature-oxygen-regimes utilizing intermittent-flow respirometry. Seasonal changes in temperature-dissolved oxygen levels consistent with Atlantic/Gulf of Mexico inshore estuaries not only exceed the physiological tolerances of lionfish, but also constrain metabolic scope at sub-lethal levels by significantly limiting maximum metabolic rate across all temperatures. Median Scrit values were 33%, 39%, 46%, and 54% at 15, 20, 25, and 30℃ respectively. Luminous sensitivities, temporal resolutions (Flicker fusion frequency), and spectral sensitivities scaled similarly with other estuarine piscivores indicating lionfish possess a visual system that can function effectively within estuarine photic conditions. Overall, visual characteristics of estuaries will not pose as a significant barrier to lionfish, but minimum winter temperatures and hypoxia will pose controlling and limiting factors substantially preventing further inshore invasion. However, caution should still be advised as lionfish may capitalize on specific temporal and spatial scales that provide suitable habitat quality and abundance of prey items. Further insight is needed to forecast the effects of temperature-dissolved oxygen on lionfish metabolic-scope.
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Vital-Durand, François. "Le système visuel du singe : anatomie, physiologie, développement et manipulations précoces." Lyon 1, 1986. http://www.theses.fr/1986LYO19008.
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Lulich, Daniel P. "Zero-crossings : symbolic vision primitives emulating physiologic encoding schemes /." Full text open access at:, 1985. http://content.ohsu.edu/u?/etd,94.
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Faruga, Michal. "Modelování procesu vidění." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217222.
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This diploma thesis considers with human vision and human eye. It takes into account both anatomic view and physiology standpoints. There is, among others, description of optical processes occurring in the organ of the sight mentioned in the work. The human eye suffers from optical defects – aberrations – that are able to degrade the retinal image and ultimately visual performance. Substantial part of the text deals with these aberrations. There are also analysed possibilities of their elimination using an inverse aberration. Work also assumes opportunity to optical modeling to calculate distorted images from ocular aberration data. Practical part consist of software application created using Matlab environment ver. 6.5 as well as full documentation. The examples of outputs procured using this application are published. Both software application and detail documentation are included on CD.
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Van, Rheede Joram Jacob. "The emergence of visual responses in the developing retinotectal system in vivo." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:57cb9bff-a085-4ac4-b413-c29112eeb78e.
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Patterned neuronal activity driven by the sensory environment plays a key role in the development of precise synaptic connectivity in the brain. It is well established that the action potentials (‘spikes’) generated by individual neurons are crucial to this developmental process. A neuron’s spiking activity is jointly determined by its synaptic inputs and its intrinsic excitability. It is therefore important to ask how a neuron develops these attributes, and whether the emergence of spiking might itself be governed by activity-dependent processes. In this thesis, I address these questions in the retinotectal system of Xenopus laevis. First, I investigate the extent to which visuospatial information is available to the developing retinotectal system. I show that the eyes of developing Xenopus larvae are hyperopic at the onset of vision, but rapidly grow towards correct vision. Despite its imperfect optics, the Xenopus eye is able to generate spatially restricted activity on the retina, which is evident in the spatial structure of the receptive fields (RFs) of tectal neurons. Using a novel method to map the visually driven spiking output and synaptic inputs of the same tectal neuron in vivo, I show that neuronal spiking activity closely follows the spatiotemporal profile of glutamatergic inputs. Next, I characterise a population of neurons in the developing optic tectum that does not fire action potentials, despite receiving visually evoked glutamatergic and γ-aminobutyric acid (GABA)ergic synaptic inputs. A comparison of visually spiking and visually non-spiking neurons reveals that the principal reason these neurons are ‘silent’ is that they lack sufficient glutamatergic synaptic excitation. In the final section of the thesis, I investigate whether visually driven activity can play a role in the ‘unsilencing’ of these silent neurons. I show that non-spiking tectal neurons can be rapidly converted into spiking neurons through a visual conditioning protocol. This conversion is associated with a selective increase in glutamatergic input and implicates a novel, spike-independent form of synaptic potentiation. I provide evidence that this novel plasticity process is mediated by GABAergic inputs that are depolarising during early development, and can act in synergy with N-methyl-D-aspartate receptors (NMDARs) to strengthen immature glutamatergic synapses. Consistent with this, preventing the depolarising effects of GABA or blocking NMDARs abolished the activity-dependent unsilencing of tectal neurons. These results therefore support a model in which GABAergic and glutamatergic transmitter systems function synergistically to enable a neuron to recruit the synaptic excitation it needs to develop sensory-driven spiking activity. This represents a transition with important consequences for both the functional output and the activity-dependent development of a neuron.
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Stivalet, Philippe. "Codage de l'orientation en vision pré-attentionnelle : dynamique des interactions sensorielles." Grenoble 2, 1995. http://www.theses.fr/1995GRE29011.
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Le experimentations sur le codage de l'orientation spatiale en vision pre-attentionnelle ont ete realisees avec le paradigme de recherche de cible parmi des distracteurs. Nous avons cherche quels sont les principaux cadres de reference qui participent au codage de l'orientation spatiale en utilisant comme critere l'amplitude de l'asymetrie de recherche visuelle specifique a la vision pre-attentionnelle. Nous avons poursuivi deux objectifs : (i) demontrer que le codage de l'orientation spatiale est de nature plurimodalitaire des les premieres etapes du traitement visuel (traitement pre-attentionnel parallele), (ii) identifier l'origine des informations sensorielles non visuelles qui contribuent a la definition des differents cadres de reference. 367 sujets repartis en 31 groupes d'un effectif moyen de 10 a 12 personnes ont participe aux experiences. Pour operationnaliser nos recherches, nous avons manipule successivement l'orientation du corps du sujet dans l'espace (axe z), la direction et l'amplitude de la force gravitoinertielle (axe gi) et l'orientation des references visuo-contextuelles (axe v). Les resultats montrent que le codage pre-attentionnel de l'orientation spatiale est realise a partir d'un systeme d'axes "primaires" orthogonaux, constitue de la verticale et de l'horizontale. L'orientation oblique a 45 degre represente un axe d'orientation "secondaire", geometriquement defini a partir des deux axes d'orientation primaires precedents. L'ensemble des donnees experimentales valident l'hypothese selon laquelle le codage pre-attentionnel de l'orientation releve d'un mode d'interaction complexe entre les informations visuelles, vestibulaires et proprio-somesthesiques. D'un point de vue fondamental, ces resultats remettent en question l'assimilation du traitement pre-attentionnel parallele de l'orientation spatiale avec un traitement de bas niveau et obligent a reviser le modele de fonctionnement dichotomique du systeme visuel en deux sous-systemes pre-attentionnel et attentionnel traitant respectivement l'information visuelle sur un mode parallele versus serielExperiments on the coding of orientation in pre-attentive vision were based on an experimental paradigm of detection of a target distinguisable from distractors through differences in orientations (treisman, 1985). We looked for the main "reference frames" contributiong to the coding of spatial orientation using the amplitude of visual search asymetry in pre-attentive vision. We had two main aims : first, to demonstrate that the coding of spatial orientation is multimode in nature from the very initial stages of visual processing (parallel processes), and second to identify the source of the non visual sensorial data that contribute to defining the various reference frames. There were 367 subjects divided into 31 groups of ten to twelve persons. For the operational aspects of our studies, we successively manipulated the orientation of the subjects' body (z-axis), the direction and the amplitude of the gravito-inertial force (gi-axis) and the orientation of the visua-contextual references (v-axis). Results show that the pre-attentive orientation coding is based on two orthogonal primary axes -vertical and horizontal. The oblique-45 degre orientation is a secondary orientation axis which is geometrically computed from the two primary axes. Experimental data demonstrate the assumption that pre-attentive orientation involves a complex interaction mode between visual, vestibular and proprio-somesthetic data. From a theoretical viewpoint, these results require the dissociation of pre-attentive processing and low level processing. Indeed, the level of integration of visual and non-visual data is relatively high in the extra-striate cortex for visual search tasks. Actually, the dichotomy between the pre-attentive (parallel processing) and attentive processes (serial processing) must be revisited
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Guo, Peiyi. "A Glia-Mediated Feedback Mechanism for the Termination of Drosophila Visual Response: A Dissertation." eScholarship@UMMS, 2010. https://escholarship.umassmed.edu/gsbs_diss/499.
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High temporal resolution of vision relies on the rapid kinetics of the photoresponse in the light-sensing photoreceptor neurons. It is well known that the rapid recovery of photoreceptor membrane potential at the end of light stimulation depends on timely deactivation of the visual transduction cascade within photoreceptors. Whether any extrinsic factor contributes to the termination speed of the photoresponse is unknown.
In this thesis, using Drosophilaas a model system, I show that a feedback circuit mediated by both neurons and glia in the visual neuropile lamina is required for rapid repolarization of the photoreceptor at the end of the light response.
In the first part of my thesis work, I provide evidence that lamina epithelial glia, the major glia in the visual neuropile, is involved in a retrograde regulation that is critical for rapid repolarization of the photoreceptor at the end of light stimulation. I identified the gene affected in a slrp (slow receptor potential) mutant that is defective in photoreceptor response termination, and found it needs to be expressed in both neurons and epithelial glia to rescue the mutant phenotype. The gene product SLRP, an ADAM (a disintegrin and metalloprotease) protein, is localized in a special structure of epithelial glia, gnarl, and is required for gnarl formation. This glial function of SLRP is independent of the metalloprotease activity.
In the second part of my thesis work, I demonstrate that glutamatergic transmission from lamina intrinsic interneurons, the amacrine cells, to the epithelial glia is required for the rapid repolarization of photoreceptors at the end of the light response. From an RNAi-based screen, I identified a vesicular glutamate transporter (vGluT) in amacrine cells as an indispensable factor for the rapid repolarization of the photoreceptor, suggesting a critical role of glutamatergic transmission from amacrine cells in this retrograde regulation. Further, I found that loss of a glutamate-gated chloride channel GluCl phenocopies vGluT downregulation. Cell specific knockdown indicates that GluCl functions in both neurons and glia. In the lamina, a FLAG-tagged GluCl colocalized with the SLRP protein in the gnarl-like structures, and this localization pattern of GluCl depends on SLRP, suggesting that lamina epithelial glia receive glutamatergic input from amacrine cells through GluCl at the site of gnarl. Since the amacrine cell itself is innervated by photoreceptors, these observations suggest that a photoreceptor — amacrine cell — epithelial glia — photoreceptor feedback loop facilitates rapid repolarization of photoreceptors at the end of the light response.
In summary, my thesis research has revealed a feedback regulation mechanism that helps to achieve rapid kinetics of photoreceptor response. This visual regulation contributes to the temporal resolution of the visual system, and may be important for vision during movement and for motion detection. In addition, this work may also advance our understanding of glial function, and change our concept about the effect of glutamatergic transmission.
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Hill, Nathan R. "Analysis of non-steady state physiological and pathological processes." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:c96c88a6-5dd4-43ce-989b-ac524d2654ea.
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The analysis of non steady state physiological and pathological processes concerns the abstraction, extraction, formalisation and analysis of information from physiological systems that is obscured, hidden or unable to be assessed using traditional methods. Time Series Analysis (TSA) techniques were developed and built into a software program, Easy TSA, with the aim of examining the oscillations of hormonal concentrations in respect to their temporal aspects – periodicity, phase, pulsatility. The Easy TSA program was validated using constructed data sets and used in a clinical study to examine the relationship between insulin and obesity in people without diabetes. In this study fifty-six non-diabetic subjects (28M, 28F) were examined using data from a number of protocols. Fourier Transform and Autocorrelation techniques determined that there was a critical effect of the level of BMI on the frequency, amplitude and regularity of insulin oscillations. Second, information systems formed the background to the development of an algorithm to examine glycaemic variability and a new methodology termed the Glycaemic Risk in Diabetes Equation (GRADE) was developed. The aim was to report an integrated glycaemic risk score from glucose profiles that would complement summary measures of glycaemia, such as the HbA1c. GRADE was applied retrospectively to blood glucose data sets to determine if it was clinically relevant. Subjects with type 1 and type 2 diabetes had higher GRADE scores than the non-diabetic population and the contribution of hypo- and hyperglycaemic episodes to risk was demonstrated. A prospective study was then designed with the aim to apply GRADE in a clinical context and to measure the statistical reproducibility of using GRADE. Fifty-three (Male 26, Female 27) subjects measured their blood glucose 4 times daily for twenty-one days. The results were that lower HbA1c’s correlated with an increased risk of hypoglycaemia and higher HbA1c’s correlated with an increased risk of hyperglycaemia. Some subjects had HbA1c of 7.0 but had median GRADE values ranging from 2.2 to 10.5. The GRADE score summarized diverse glycaemic profiles into a single assessment of risk. Well-controlled glucose profiles yielded GRADE scores <= 5 and higher GRADE scores represented increased clinical risk from hypo or hyperglycaemia. Third, an information system was developed to analyse data-rich multi-variable retinal images using the concept of assessment of change rather than specific lesion recognition. A fully Automated Retinal Image Differencing (ARID) computer system was developed to highlight change between retinal images over time. ARID was validated using a study and then a retrospective study sought to determine if the use of the ARID software was an aid to the retinal screener. One hundred and sixty images (80 image pairs) were obtained from Gloucestershire Diabetic Eye Screening Programme. Images pairs were graded manually and categorised according to how each type of lesion had progressed, regressed, or not changed between image A and image B. After a 30 day washout period image pairs were graded using ARID and the results compared. The comparison of manual grading to grading using ARID (Table 4.3) demonstrated an increased sensitivity and specificity. The mean sensitivity of ARID (87.9%) was increased significantly in comparison to manually grading sensitivity (84.1%) (p<0.05). The specificity of the automated analysis (87.5%) increased significantly from the specificity (56.3%) achieved by manually grading (p<0.05). The conclusion was that automatic display of an ARID differenced image where sequential photographs are available would allow rapid assessment and appropriate triage. Forth, non-linear dynamic systems analysis methods were utilised to build a system to assess the extent of chaos characteristics within the insulin-glucose feedback domain. Biological systems exist that are deterministic yet are neither predictable nor repeatable. Instead they exhibit chaos, where a small change in the initial conditions produces a wholly different outcome. The glucose regulatory system is a dynamic system that maintains glucose homeostasis through the feedback mechanism of glucose, insulin, and contributory hormones and was ideally suited to chaos analysis. To investigate this system a new algorithm was created to assess the Normalised Area of Attraction (NAA). The NAA was calculated by defining an oval using the 95% CI of glucose & Insulin (the limit cycle) on a phasic plot. Thirty non-diabetic subjects and four subjects with type 2 diabetes were analysed. The NAA indicated a smaller range for glucose and insulin excursions with the non-diabetics subjects (p<0.05). The conclusion was that the evaluation of glucose metabolism in terms of homeostatic integrity and not in term of cut-off values may enable a more realistic approach to the effective treatment and prevention of diabetes and its complications.
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Forshee, Terri Ann. "The influence of family visits on physiologic responses in coronary care patients /." Thesis, Connect to this title online; UW restricted, 1988. http://hdl.handle.net/1773/7283.
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Lekhel, Hamid. "Rôle de la vision dans les stratégies d'équilibre postural et locomoteur chez l'homme : analyse statistique par la méthode des inter-corrélations conjuguée." Aix-Marseille 2, 1994. http://www.theses.fr/1994AIX22012.
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Les strategies sensori-motrices mises en uvre chez l'homme adulte au service de l'equilibre statique ou dynamique sont examinees ici dans diverses taches posturales: maintien de l'equilibre sur support destabilisant, locomotion sur sol et poutre et reaction posturale a une force transitoirement appliquee. L'accent est mis en particulier sur les contributions visuelles a ces controles posturaux. Nous proposons de plus une etude des strategies de mouvements multi-segmentaires de maintien de l'equilibre. Il s'agit d'une analyse statistique basee sur l'exploitation des fonctions d'inter-correlation appliquees aux differents descripteurs du mouvement que nous avons selectionnes, accelerations lineaires, variations angulaires ou enregistrements electromyographiques. Cette methode permet de determiner les relations spatiales et temporelles entre les mouvements coordonnes, et d'en etudier la dependance en fonction de la tache et des conditions sensorielles. Les avantages, les limites et les perspectives de cette methode des inter-correlations conjuguees, applicable a toutes les conditions d'observation, naturelles ou experimentales, sont enfin discutees
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Vallet, Anne. "Analyse comportementale et électrophysiologique d'une vision hautement spécialisée : cas du mâle d'abeille (Apis mellifica L.)." Bordeaux 2, 1992. http://www.theses.fr/1992BOR28216.
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Genon-Catalot, Denis. "Conception d'un dispositif expérimental pour l'étude des conflits vision-posture." Grenoble 1, 1993. http://www.theses.fr/1993GRE10109.
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L'objet de cette these est la conception d'une instrumentation destinee a l'etude des mecanismes impliques dans le pilotage des systemes mobiles dans l'espace. L'instrumentation developpee comporte un stimulateur postural, un stimulateur visuel et un systeme pour la mesure de la posture. Le stimulateur postural est organise autour d'un fauteuil tri-axal, pilote par calculateur, qui permet des mouvements de tangage (+/45), de roulis (+/45) et de lacet. Le stimulateur visuel que nous avons developpe se compose d'un generateur d'images et d'un projecteur cathodique monochrome. Le generateur d'images permet de presenter des figures vectorielles enchassees dans une scene generee en video. Le procede d'affichage mixte pilote un systeme cathodique de projection a balayage vectoriel. Enfin pour observer les effets des stimulations visuelles sur la posture nous avons realise un systeme de mesure uni-axiale. L'ensemble de l'instrumentation est pilote a travers des logiciels simples et conviviaux depuis des compatibles ibm-pc. Des exemples des recherches menees avec ces appareils sont enonces en fin de memoire
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Javal, Émile. "Du strabisme dans ses applications à la physiologie de la vision thèse pour le doctorat en médecine présentée et soutenue le 2 mars 1868 /." Paris : BIUM, 2003. http://www.bium.univ-paris5.fr/histmed/medica/cote?TPAR1868x67.
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Beauquin, Christophe. "Caractéristiques fonctionnelles des afférences rétino-tectales ipsilatérales chez un amphibien (Rana esculenta) : sensibilité aux stimuli "configurationnels"." Poitiers, 1998. http://www.theses.fr/1998POIT2294.
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Chez la grenouille, les informations retiniennes projetant vers le toit optique ipsilateral utilisent une voie bisynaptique, deux fois croisee. Au sein de cette voie, le noyau isthmique est l'ultime station de relais. L'input ipsilateral retino-tecto-isthmo-tectal (irtt) est compose de deux groupes fonctionnels, les unites i1 et i2, ressemblant respectivement aux cellules ganglionnaires retiniennes r2 et r3. L'etude anatomique de la voie ipsilaterale irtt avec la biotine dextran amine confirme que la projection isthmo-tectale croisee est restreinte aux deux-tiers rostraux, binoculaires, du tectum et que le croisement se situe dans la partie posterieure du chiasma optique. Afin de comparer les systemes ipsilateral et contralateral, l'activite des unites i1 a ete enregistree extracellulairement en reponse a des stimuli mobiles configurationnels - i. E. Des barres noires de longueur croissante (l), orientees dans le sens du mouvement (configuration wl), ou perpendiculairement a la direction du mouvement (configuration awl). Un facteur de discrimination d(w,a), sorte de mesure du contraste entre des barres wl et awl de taille identique, a ete calcule. La sensibilite configurationnelle d(w,a)=f(l) des unites i1 ressemble a celle observee pour les cellules ganglionnaires r3. En outre, elle est invariante avec le niveau d'illumination ambiante et la structure du fond stationnaire. Neanmoins, son profil depend de la vitesse de deplacement du stimulus, et surtout de la largeur des barres wl-orientees. En conclusion, les unites i1 presenteraient les caracteristiques temporelles des cellules ganglionnaires r2, mais les caracteristiques spatiales des cellules ganglionnaires r3. Enfin, la courbe d(w,a)=f(l) represente la sensibilite differentielle d'un neurone visuel pour deux bords orientes verticalement de taille differente plutot qu'une sensibilite differentielle entre deux objets de taille identique mais de configuration differente.
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Jiménez, Manuel. "Temoignage d'ovni et psychologie de la perception." Montpellier 3, 1994. http://www.theses.fr/1994MON30012.
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La these defendue est la suivante : "un temoignage d'ovni est, dans la plupart des cas, l'aboutissement d'un processus de mesinterpretation perceptive d'un evenement connu". Le chapitre les limites epistemologiques et methodologiques de la demarche suivie. Le chapitre 2 montre que le temoignage d'ovni est general et repete, observable et analysable. Dans le chapitre 3 on passe en revue quelques essais particuliers, infructueux, pour expliquer ce phenomene, et on montre l'importance de la perception, en particulier de la perception de la distance. Le chapitre 4 rappelle les travaux et les explications classiques de la perception de la distance. Un de ses aspects, l'influence de la hauteru angulaire et de la distance supposee de l'horizon visuellement proche, est approfondi dans le chapitre 5. La question, plus generale, de l'erreur en psychologie de la perception est traitee dans le chapitre 6. On aboutit a un modele original qui, face au temoignage d'ovni, se manifeste dans quelques hypotheses principales, concernant la distance apparente, l'identite perceptive, et le schema cognitif d'ovni. Dans le chapitre 7 ces hypotheses sont confrontees aux temoignanges d'ovni, qui les confirment, parfois de facon partielle. Dans un dernier chapitre, une postface signale les questions qui restent ouvertes, principalement celle de l'origine de la representation d'ovni, et celle de la generalisation de l'explication proposeeThe defend thesis is : "a ufo witness is, in most cases, the issue of a know event's erroneous perception". The chapters 1, 2 and 3 describe the ufo witness's phenomenon; they show the perception's importance. The chapters 4,5 and 6 analyse the works and the explanations of the distance's perception and erroneous perception. They end in some principals hypothesis, concerning the appear distance, the perceptive recognition and the ufo's cognitive schema. In the chapter 7, these hypothesis are confronted with the witness. The last chapter examines complementary questions
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Li, Tianyi. "Vision, mutlisensory integration and aging in an integrated computational model of spatial memory." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS612.
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De plus en plus de données neuroscientifiques provenant de diverses espèces animales, y compris de l’homme, sont disponibles grâce au progrès technologique dans la capture des signaux cérébraux et des comportements qui y sont liés. Ces quantités croissantes de données, ainsi que la puissance et la capacité de mémoire sans précédent des ordinateurs d'aujourd'hui, nécessitent des modèles informatiques à grande échelle dans le but d'unifier, de stocker et d'analyser ces données. De plus, de tels modèles permettent de croiser des études computationnelles de divers domaines et à différents niveaux de la hiérarchie neuronale afin de mieux comprendre les mécanismes neuronaux qui sous-tendant divers phénomènes cognitifs et eur lien avec le comportement. L'objectif de cette thèse est de développer un modèle intégré du comportement humain dans le contexte de l'orientation spatiale et de sa détérioration avec l'âge. Le problème de la cognition spatiale est considéré ici comme un problème d’intégration multisensorielle entre des indices sensoriels externes provenant de l'environnement et d’informations sensorielles internes issue du mouvement propre, dans le but de construire une représentation mentale de l'environnement. Un grand nombre de recherches expérimentales suggèrent que cette représentation est construite dans un réseau complexe de zones cérébrales résidant dans le lobe temporal médian qui reçoit les entrées sensorielles externes par le biais du chemin visuel « dorsal » provenant des aires visuelles rétinotopiques et passant par le cortex pariétal. Il a été démontré que le vieillissement affecte fortement les réseaux du lobe temporal médian et les comportements associés basés sur la mémoire, et en particulier la création de représentations mentales de l’espace. Dans cette thèse nous développons un modèle neuronal intégré de la mémoire spatiale en s’appuyant sur des données expérimentales anatomiques et fonctionnelles concernant le traitement de l'information sensorielle dans le chemin visuel dorsal et dans des réseaux du lobe temporal médial. Nous utilisons ce modèle pour simuler plusieurs expériences reliant les fonctions visuelles humaines aux comportements d'orientation spatiale, et nous proposons comment les repères visuels sont combinés avec des entrées proprioceptives pendant la construction des cartes mentales de l'environnement. Nous testons ensuite l'hypothèse selon laquelle le vieillissement exerce ses effets détériorants sur la mémoire spatiale en agissant sur l'action neuromodulatrice dans le cerveau et est lié à un traitement des nouveautés réduit dans le lobe temporal médial. Dans l'ensemble, les travaux réalisés dans le cadre de cette thèse de doctorat constituent un premier pas vers la création d'une plate-forme informatique intégrée pour la simulation du comportement humain et contribuent à une meilleure compréhension de la façon dont les représentations spatiales sont construites à partir de signaux sensoriels et sont affectées par le vieillissementAn ever growing body of neuroscientific data is becoming available from various animal species, including humans, due to technological advances in capturing brain signals and behavior linked with them. These increasing amounts of data, together with an unprecedented power and memory capacity of present day computers calls for large scale computational models with the objective of unifying, storing and analysing these data. Moreover, such models allow crosslinking computational studies from various domains and in various levels of neural hierarchy to provide a deeper understanding of neuronal mechanisms underlying various cognitive phenomena and their link with behavior. The objective of this thesis is to develop an integrated model of human behavior in the context of spatial orientation and its deterioration with age. The problem of spatial cognition is considered as a problem of combining external sensory cues coming from the environment and internal sensory cues coming from self-motion information, with the objective to build a mental representation of surrounding space. A large body of experimental research suggests that this representation is constructed within an intricate network of brain areas residing in the medial temporal lobe, with external sensory input arriving via a ``dorsal'' visual path originating in early visual areas and passing via the parietal cortex. Aging has been shown to strongly affect medial temporal lobe networks and associated memory-based behaviors, and in particular the creation of mental representations of space. In this thesis we develop an integrated neural network model of spatial memory by based on anatomical and functional experimental evidence of sensory information processing in the dorsal visual path and medial temporal lobe networks. We use this model to simulate a number of experiments linking human visual functions with spatial orientation behaviors, and propose how visual cues are combined with self-motion input during the construction of mental maps of space. We then test the hypothesis that aging exerts its deteriorating effects on spatial memory via acting on neuromodulatory action in the brain and is linked with reduced novelty processing in the medial temporal lobe. Overall, the work performed during this doctoral thesis provides a first step towards building an integrated computer platform for human behavior simulation and contributes to a better understanding of how spatial representations are built from sensory signals and are affected by aging
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Tess, Claude. "Extraction de primitives mouvement en traitement d'images par modélisation de l'architecture des systèmes visuels biologiques." Nancy 1, 2000. http://www.theses.fr/2000NAN10014.
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Dans le cadre de la vision par ordinateur, ce mémoire, inspiré de l'observation du fonctionnement des systèmes visuels biologiques des primates, présente une approche d'extraction de primitives du mouvement issue de séquences d'images en niveaux de gris. La démarche traditionnelle en visionique, que nous avons rappelée sous une forme bibliographique (chapitre 2), consiste souvent à rechercher parmi la diversité des méthodes existantes, la succession d'outils qui offre les meilleurs résultats, puis de la généraliser par l'expérimentation. Mais les sytèmes développés sur ce principe manquent souvent d'universalité, alors que les systèmes visuels biologiques s'en acquittent fort bien. Nous nous en sommes inspirés, afin d'élaborer une approche plus naturelles à la résolution de problèmes de vision par ordinateur. Ainsi, le système visuel des primates par ses capacités d'adaptation, permet d'exécuter des tâches visuelles complexes (chapitre 3). Notre travail de modélisation architecturale et fonctionnelle des systèmes visuels biologiques (chapitre 4), utilisant les outils du traitement du signal, extrait des primitives spatio-temporelles telles que les segments ou encore les points anguleux, destinées à la reconstruction du mouvement global d'objets pesants, rigides et polyédriques. Nous n'abordons ici que l'aspect translation dans le plan. Notre réalisation, implémentée en Matlab et langage C++, comporte des modules séquentiels entre lesquels il est possible d'accéder aux informations intermédiaires du traitement. Cette recherche, très actuelle, nous semble riche en développements tant sur l'approche employée que sur les méthodes utiliséesWithin the context of Computer Vision, this thesis presents a motion primitives extraction approach stemming from grey level image sequences, inspired from the observation of primates biological visual system functionning. Usual processes in Machine Vision, set out in a bibliographical form (chapter 2), often consists in seeking, tools succession which offers the best results among existing methods diversity, and then generalising it by experimentation. But systems developed on thid principle often miss universality, whereas biological visual systems fulfill very well. We took our inspiration from biological processes, in order to work out a more natural approach to Computer Vision prblems resolution. Thus, visual primates system by its adaptation capacities, allows to carry out complex visual tasks (chapter 3). Our work on architectural and functionnal modelling of biological visual systems (chapter 4), using signal reconstruction of heavy, rigid and polyhedral objects. We considered only translation in plane. Our realisation, implemented in Matlad and C++ language, is composed of sequential modules that allow to reach intermediate processing information. This typical research seems to us full of developments as well on the approach employed as on the methods used
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Seghier, Mohamed Lamine. "IRM fonctionnelle de la vision : arguments en faveur du traitement des contours illusoires dans les aires corticales de bas niveau." Grenoble 1, 2000. http://www.theses.fr/2000GRE10046.
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Dans ce travail, nous nous sommes intéressés au traitement des contours illusoires au sein du système visuel. Nous avons, en particulier, cherché à vérifier si les aires visuelles de bas niveau sont impliquées lors de la perception de contours illusoires. A cet effet, nous avons développé des paradigmes irmf originaux utilisant des contours illusoires de type kanizsa. Dans un premier paradigme, de type bloc, nous avons exploité le mouvement de contours illusoires. Des premières expériences nous ont montré une implication des aires v1/v2, non-différenciées. Dans une seconde série d'expériences, en utilisant également des techniques irmf de délinéation des aires v1 et v2, nous avons pu clairement identifier une activation significative de l'aire v1. Parallèlement, des activations ont été obtenues dans les aires mt+ et los/ko. Les activations dans l'aire v1 ont été nettement plus significatives en présence qu'en absence de mouvement, suggérant une possible contribution d'effets de contre-réaction (mt+$$v1). Nous avons voulu vérifier, en une seconde étape, si des contours illusoires présentés à excentricité variable induisent des réponses le long de la scissure calcarine selon la représentation retinotopique de v1. A cette fin, nous avons mis au point un second paradigme, de type fourier. Les propriétés de phase des réponses fonctionnelles obtenues le long de la scissure calcarine semblent bien en accord avec les propriétés retinotopiques de v1. Ces expériences nous ont donc fourni des arguments cohérents en faveur de l'implication de v1 dans la perception de contours illusoires.
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Rolla, Paula Mota Theo. "Behavioral and neurobiological studies of visual processing in honeybees." Toulouse 3, 2011. http://www.theses.fr/2011TOU30111.
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La vision chez l'abeille a été largement étudiée au niveau comportemental, en entraînant des insectes en libre vol à associer des cibles visuelles à une récompense de saccharose, et - dans une moindre mesure - au niveau physiologique, à l'aide d'enregistrements électrophysiologiques intracellulaires de neurones individuels des circuits visuels du cerveau de l'abeille. Notre connaissance des mécanismes du traitement visuel chez cet insecte demeure cependant limitée par le manque de : 1- protocoles de conditionnement pour l'étude de l'apprentissage et de la mémoire visuels chez des abeilles en contention dans le laboratoire ; 2- caractérisations anatomiques et physiologiques des neuropiles visuels du cerveau central ; et 3- techniques d'étude fonctionnelle du traitement visuel au niveau des circuits neuronaux du cerveau. Le présent travail a pour objectif de combler ces lacunes en menant une étude multiéchelle du traitement visuel chez les abeilles. Nous avons cherché à développer de nouveaux protocoles de conditionnement appétitif et aversif pour l'étude de l'apprentissage et de la mémoire visuels chez les abeilles en contention. Sur le plan appétitif, nous avons montré que les abeilles en contention ne sont pas capables d'apprendre une association directe entre couleur et saccharose. Pour des raisons à ce jour inconnues, l'ablation des antennes est nécessaire pour que les abeilles en contention acquièrent une telle association élémentaire entre couleur et saccharose. Malgré cette incapacité, des abeilles non-lésées parviennent à résoudre une discrimination bimodale non élémentaire dans laquelle les couleurs agissent comme modulateurs de l'apprentissage olfactif appétitif. Nous apportons donc la première démonstration contrôlée d'occasion setting bimodal (couleur-odeur) chez des abeilles en contention. Sur le plan aversif, nous avons établi un nouveau protocole de conditionnement dans lequel des abeilles en contention apprennent des associations entre stimuli visuels et chocs électriques. Nous montrons que les abeilles non-lésées apprennent à discriminer entre stimuli visuels punis et non punis en fonction de leurs propriétés chromatiques ou achromatiques, ou les deux à la fois. Non seulement l'ablation des antennes n'est pas nécessaire à l'apprentissage, mais elle compromet le conditionnement visuel par une réduction concomitante de la réponse au choc électrique. Ces deux protocoles, appétitif et aversif, ouvrent ainsi de nouvelles voies d'accès aux corrélats neuronaux de l'apprentissage et de la mémoire visuels et / ou bimodaux chez l'abeille. Nous avons réalisé par ailleurs une description neuroanatomique de circuits visuels non encore étudiés dans le cerveau central de l'abeille. Ainsi, nous avons caractérisé l'organisation et l'architecture neurale du tubercule optique antérieur (AOTu), et révélé une ségrégation de l'information visuelle dorso-ventrale dans cette structure. À travers la mise au point d'un nouveau protocole d'enregistrement optophysiologique de l'activité des circuits visuels, nous avons étudié la réponse des interneurones de l'AOTu lors de la stimulation visuelle de l'œil composé. Nous avons montré que des stimuli lumineux présentés dans différentes zones du champ visuel induisent des patrons d'activation distincts de ces interneurones, en lien avec la ségrégation dorso-ventrale mise en évidence par nos données neuroanatomiques. La stimulation des interneurones de l'AOTu à l'aide de lumières monochromatiques et de mélanges chromatiques a mis en évidence la dynamique temporelle des réponses neurales et les propriétés de traitement chromatique dans l'AOTu. Nos recherches offrent ainsi une analyse du traitement visuel chez l'abeille allant de l'étude comportementale de l'apprentissage visuel élémentaire et non élémentaire jusqu'à l'étude neurobiologique de l'encodage visuel dans le cerveau central de l'abeille. Ces approches ouvrent de nouvelles voies à l'exploration des modifications dépendantes de l'expérience de l'activité neuronale du cerveau central de l'abeilleVision in honeybees has been extensively studied at the behavioral level by training free-flying insects to choose visual targets rewarded with sucrose solution, and, to a lesser degree, at the physiological level using intracellular electrophysiological recordings of single neurons in different areas of the visual circuits of the bee brain. However, our knowledge of visual processing in honeybees is still limited by the lack of: 1- conditioning protocols for studying visual learning and memory in harnessed animals under controlled laboratory conditions; 2- anatomical and physiological characterizations of visual neuropils in the central brain; and 3- techniques for performing functional studies of visual processing at the neuronal circuit level. In the present work, we aimed at filling these gaps by providing a multilevel study of visual processing in harnessed bees. We aimed at developing novel appetitive and aversive conditioning protocols for studying visual learning and memory in harnessed bees. In an appetitive framework, we showed that intact harnessed bees are not capable of learning a direct association between color and sucrose. For reasons so far unknown, antennae ablation is necessary for harnessed bees to acquire such an elemental color-sucrose association. Despite this incapacity, intact bees are able to solve a non-elemental bimodal discrimination in which colors act as modulators of appetitive olfactory learning. We therefore provide the first controlled demonstration of bimodal (color-odor) occasion setting in harnessed honeybees. In an aversive framework, we established a new conditioning protocol in which harnessed bees learn aversive associations between visual cues and an electric shock. We showed that bees with intact antennae learn to discriminate punished from non-punished visual stimuli by relying on their chromatic or achromatic cues, or both. Antennae ablation was not only unnecessary for learning to occur but it even impaired visual conditioning due to a concomitant reduction of responsiveness to the electric shock. Both behavioral protocols, appetitive and aversive, open new doors for accessing the neural correlates of visual and/or bimodal learning and memory in honeybees. We also provided a comprehensive neuroanatomical description of unstudied visual circuits in the central bee brain. More specifically, we characterized the organization and neural architecture of the anterior optic tubercle (AOTu) and revealed a segregation of dorso-ventral visual information into this structure. Having established a novel protocol for performing optophysiological recordings of visual-circuit activity in the honeybee brain, we studied the responses of AOTu interneurons during visual stimulation of the compound eye. We showed that light stimuli presented in different parts of the visual field induced distinct patterns of activation in these interneurons, consistent with the dorso-ventral segregation revealed by our neuroanatomical data. Stimulation of AOTu interneurons with monochromatic lights and with chromatic mixtures induced distinct signal intensities, time-course dynamics and activity patterns, thus revealing intricate chromatic processing properties in this visual neuropil. Our studies provide therefore an innovative, multilevel analysis of visual processing in honeybees, spanning from behavioral studies on elemental and non-elemental visual learning to neurobiological studies on visual processing and coding in the honeybee central brain. Taken together our studies open new doors to investigate for the first time experience-dependent changes of neural activity in the bee brain related to visual and/or bimodal learning, a goal that has remained elusive until now
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Vacher, Jonathan. "Synthèse de textures dynamiques pour l'étude de la vision en psychophysique et électrophysiologie." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLED005/document.
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Le but de cette thèse est de proposer une modélisation mathématique des stimulations visuelles afin d'analyser finement des données expérimentales en psychophysique et en électrophysiologie. Plus précis\'ement, afin de pouvoir exploiter des techniques d'analyse de données issues des statistiques Bayésiennes et de l'apprentissage automatique, il est nécessaire de développer un ensemble de stimulations qui doivent être dynamiques, stochastiques et d'une complexité paramétrée. Il s'agit d'un problème important afin de comprendre la capacité du système visuel à intégrer et discriminer différents stimuli. En particulier, les mesures effectuées à de multiples échelles (neurone, population de neurones, cognition) nous permette d'étudier les sensibilités particulières des neurones, leur organisation fonctionnelle et leur impact sur la prise de décision. Dans ce but, nous proposons un ensemble de contributions théoriques, numériques et expérimentales, organisées autour de trois axes principaux : (1) un modèle de synthèse de textures dynamiques Gaussiennes spécialement paramétrée pour l'étude de la vision; (2) un modèle d'observateur Bayésien rendant compte du biais positif induit par fréquence spatiale sur la perception de la vitesse; (3) l'utilisation de méthodes d'apprentissage automatique pour l'analyse de données obtenues en imagerie optique par colorant potentiométrique et au cours d'enregistrements extra-cellulaires. Ce travail, au carrefour des neurosciences, de la psychophysique et des mathématiques, est le fruit de plusieurs collaborations interdisciplinairesThe goal of this thesis is to propose a mathematical model of visual stimulations in order to finely analyze experimental data in psychophysics and electrophysiology. More precisely, it is necessary to develop a set of dynamic, stochastic and parametric stimulations in order to exploit data analysis techniques from Bayesian statistics and machine learning. This problem is important to understand the visual system capacity to integrate and discriminate between stimuli. In particular, the measures performed at different scales (neurons, neural population, cognition) allow to study the particular sensitivities of neurons, their functional organization and their impact on decision making. To this purpose, we propose a set of theoretical, numerical and experimental contributions organized around three principal axes: (1) a Gaussian dynamic texture synthesis model specially crafted to probe vision; (2) a Bayesian observer model that accounts for the positive effect of spatial frequency over speed perception; (3) the use of machine learning techniques to analyze voltage sensitive dye optical imaging and extracellular data. This work, at the crossroads of neurosciences, psychophysics and mathematics is the fruit of several interdisciplinary collaborations
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Park, Hyeongdong. "Brain-body interactions in conscious experience : linking subjectivity, neural maps of visceral organs, and visual consciousness." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066055.
Full textAbstract:
Rapporter 'j'ai vu le stimulus' est la marque de la vision consciente et implique deux caractéristiques fondamentales de l'expérience consciente, à savoir son aspect qualitatif et la subjectivité. L'aspect qualitatif correspond à la perception vive du stimulus, alors que la subjectivité correspond à la conscience implicite que j'ai fait l'expérience du stimulus. Afin de déterminer les bases neurales de la subjectivité, nous introduisons le concept de cadre neural subjectif ('neural subjective frame') qui correspond aux mécanismes biologiques définissant le sujet en tant qu'une entité biologique, un point d'ancrage à partir duquel des expressions relatives à l'expérience consciente à la première personne peuvent être formulées. De plus, je propose que la représentation neurale de l'information viscérale pourrait constituer ce cadre neural subjectif. Afin de tester expérimentalement cette hypothèse, à l'aide de la magnétoencéphalographie, nous avons enregistré les réponses neuronales aux battements cardiaques, pendant que les participants réalisaient une tâche de détection visuelle. Nous avons trouvé que les réponses neuronales aux battements cardiaques avant la présentation du stimulus, dans le cortex cingulaire ventral antérieur et le lobule postérieur intrapariétal droit, pouvaient prédire la détection d'un stimulus visuel de faible contraste. Les réponses neuronales aux battements cardiaques de plus forte amplitude s'accompagnaient d'un taux de détection et d'une sensibilité plus importants, sans changement du critère de décision. Ni les fluctuations des paramètres corporels ni l'excitabilité corticale générale ne semblent contribuer à ces résultats. Par ailleurs, le fait de voir consciemment le stimulus a ralenti le battement cardiaque après la réponse des participants et cet effet de décélération cardiaque pouvait être prédit par la réponse neuronale aux battements cardiaques du cortex cingulaire antérieur ventral, avant la présentation du stimulus. Ainsi, nos résultats sont en faveur de l’hypothèse selon laquelle la cartographie des afférents viscéraux façonne notre expérience subjective perceptive. Au-delà de la vision consciente, ces résultats suggèrent que les signaux internes du corps et leurs représentations neuronales peuvent être la source de fluctuations dans des aires corticales multi-fonctionnellesReporting “I saw the stimulus” is the hallmark of conscious vision and implies two fundamental characteristics of conscious experience, namely qualitativeness and subjectivity. Qualitativeness refers to the vivid feeling of the stimulus, whereas subjectivity refers to the implicit awareness that the experience occurred for me. To account for the neural basis of subjectivity, we introduce a concept termed the neural subjective frame which corresponds to the basic biological mechanisms defining the subject as a biological entity, as an anchoring point from which the first-person statements of conscious experience can be expressed. I further propose that neural representation of visceral information could constitute the neural subjective frame. To experimentally test this proposal, using magnetoencephalography, we recorded neural events locked to heartbeats while participants conducted visual detection task. We found that neural responses to heartbeats before stimulus onset in ventral anterior cingulate and right posterior intraparietal lobule could predict the detection of faint visual stimulus. Larger amplitude of neural responses to heartbeats were accompanied by enhanced hit-rate and sensitivity, but without changes in decision criterion. Neither fluctuations in measured bodily parameters nor in overall cortical excitability could account for this finding. In addition, consciously seeing the stimulus decelerated heartbeat after participants responded and the heartbeat slowing effect could be predicted from the prestimulus neural responses to heartbeats in ventral anterior cingulate cortex. Our findings therefore support the hypothesis that neural mapping of visceral afferents shape perceptual subjective experience. Beyond conscious vision, our findings suggest that signals from internal body and their neural representations could be sources of fluctuations in multi-functional cortical areas
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Arzi, Mohammad. "Traitement automatique des signaux vestibulo-oculaires et optocinétiques." Lyon, INSA, 1986. http://www.theses.fr/1986ISAL0025.
Full textAbstract:
Analyse entièrement automatique et fiable des réflexes vestibulo-oculaire{R. V. 0) et optocinétique (R. O. C. ). Pour cette analyse, un nouvel algorithme a été développe qui effectue une classification des phases lentes et rapides du nystagmus oculaire. La méthode utilisée pour le classement des phases lentes, fait appel à des notions de la théorie des sous ensembles flous. On peut résumer la méthode comme suit : 1)Une classification globale des phases lentes est réalisée. A chaque point du nystagmus une valeur est affectée qui détermine, dans un contexte global du nystagmus, son appartenance aux phases lentes. 2)Se basant sur ce classement, la forme globale de l'évolution des phases lentes est révélée en faisant un ajustement de courbe au sens des moindres carrés pondérés par la fonction d'appartenance obtenue en 1). 3)Le classement des phases lentes est raffiné en se basant sur la forme globale que l'an a obtenue en 2). Cette fois on obtient une classification locale des phases lentes. 4)La "Position Cumulée de la Phase Lente" (P. C. P. L. ) de l’œil est construite en supprimant les phases rapides et en mettant bout à bout les phases lentes et en faisant une interpolation pendant les phases rapides. 5)Un ajustement de courbe sur la P. C. P. L. Est effectué. Cet ajustement se fait au sens des moindres carrés pondérés par la dernière fonction d'appartenance. Les paramètres des R. V. O. Ou R. O. C. Sont calculés en se basant sur cette dernière courbe.
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Lablack, Adel. "Estimation du regard dans un environnement contrôlé." Phd thesis, Université des Sciences et Technologie de Lille - Lille I, 2010. http://tel.archives-ouvertes.fr/tel-00841161.
Full textAbstract:
L'objectif principal de mon travail de thèse est l'extraction de la direction du regard (attention visuelle) d'une personne à partir de la vidéo. Cette analyse est effectuée dans un environnement composé d'une scène cible et d'une zone d'observation. La scène cible est une région d'intérêt définie pour être analysée (e.g. un écran plasma large, une image projetée sur un mur, une affiche publicitaire, un linéaire dans un magasin, ou la vitrine d'un magasin). La zone surveillée quant à elle est l'emplacement d'où les personnes regardent la scène cible (e.g. la rue, un couloir ou bien les allées d'un supermarché). Les connaissances qui sont extraites sont alors utilisées pour comprendre le comportement visuel de personnes ainsi que pour la réorganisation de la scène cible. Pour atteindre cet objectif, nous proposons une approche basée sur l'estimation de l'orientation de la tête et la projection du champ visuel pour localiser la région d'intérêt. Nous avons utilisé une méthode d'estimation de l'orientation de la tête basée sur l'apparence globale et sur un modèle cylindrique, et une méthode de projection géométrique pour extraire les régions d'intérêts basée sur les données physiologiques de la vision humaine. L'analyse du comportement visuel des personnes a été effectuée à l'aide d'un ensemble de métriques. Les méthodes proposées ont été validées sur des données vidéos et images.
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Railing, Patricia Ann. "Kazimir Malévitch : le suprématisme comme sensation pure." Thesis, Paris 1, 2013. http://www.theses.fr/2013PA010565/document.
Full textAbstract:
Entre 1911 et 1920, Kazimir Malévitch découvre de nouvelles lois artistiques. Grâce à l' « Optique physiologique » d'Hermann von Helmholtz (1856-1866), il transforme les lois scientifiques des sensations optiques (couleur, lumière, mouvement) et celles des structures optiques de la vision en lois artistiques avec lesquelles il crée ses tableaux néo-primitivistes (1911-1912), proto-cubistes (1912-1913), futuristes (1912), cubistes (1913-1914) et suprématistes (1915-1920). Cette transformation des lois scientifiques de la vision en principes créatifs explique les innovations et l'évolution stylistique de Malévitch de 1911 à 1920. Ces découvertes sur les procédés créatifs de Malévitch sont totalement nouvelles, car ce travail est le premier à porter sur ce sujet. La présente thèse est composée de deux parties. La première présente en trois chapitres les lois de la perception sensorielle. Ell explique comment l'oeil voit la direction, la position, la taille et les dimensions dans le champ visuel. La seconde consiste également en trois chapitres, dans lesquels l'auteur analyse l'exploration par Malévitch de la sensation et de la perception sensorielle dans ses tableaux néo-primitivistes et proto-cubistes, de la perception sensorielle seule dans le cubisme et des sensations de couleur et de lumière pures dans le suprématisme. Tandis que la science révèle à l'artiste les vérités de la vision, les tableaux de Malévitch deviennent l'art de la vision optique. Ces recherches fournissent une contribution majeure pour la compréhension de l'oeuvre de Kazimir MalévitchBetween 1911 and 1920, Kazimir Malevitch was discovering new artistic laws with which to create. Relying on Hermann von Helmholtz's, « Treatise on Physiological Optics (1856-1866), scientific laws of optical sensations (colour, light and movement) and optical structures of seeing were transformed into artistic laws. With them Malevitch created his Neo-Primitivist paintings (1911-1912), Proto-Cubist paintings (1912-1913), Futurist paintings (1912), Cubist paintings (1913-1914), and Suprematist paintings (1915-1920). Adapting scientific laws of vision to creative laws of painting is what accounts for Malevitch's innovations and artistic development, 1911-1920.These are entirely new discoveries about malevitch's creative processes, a subject investigated here for the first time. Divided into two parts, the first part consists of three chapters on the science of optical sensations, the laws of light and colour, and the laws of sense perceptions : how the eye sees direction, position, size and dimensions in the visual field. The second part consists of three chapters analysing how Malevitch explored sensation and sense perception in the Neo-Primitive and Proto-Cubist paintings, sense perception in Cubism, and, in Suprematism, the pure sensations of colour and light. With science providing the truths of vision, Kazimir Malevitch's paintings became the art of the seeing eye, and this is a major new contribution to the understanding of the painting of Kazimir Malevitch
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Bonnefond, Catherine. "Melatonine et transmission de l'information photoperiodique chez le vison et le hamster dore." Paris 6, 1988. http://www.theses.fr/1988PA066626.
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Hardy, Olivier. "Le toit optique du pigeon : propriétés fonctionnelles et organisation neuronale." Paris 6, 1986. http://www.theses.fr/1986PA066028.
Full textAbstract:
Étude des propriétés des champs récepteurs des neurones du toit optique de pigeon, comparaison avec celles des neurones du colliculus des mammifères. Mise en évidence d'un rôle majeur du toit optique des oiseaux dans le traitement de l'information visuelle. Les réseaux neuronaux responsables de ce traitement ont été étudiés par enregistrement et marquage intracellulaire à l'HRP. Un modèle d'organisation de ces réseaux est proposé.
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Cian, Corinne. "Perception de la verticale visuelle : approche différentielle des mouvements oculaires." Université Pierre Mendès France (Grenoble ; 1990-2015), 1992. http://www.theses.fr/1992GRE29061.
Full textAbstract:
L'influence de l'inclinaison de l'environnement visuel sur la perception de l'orientation posturale et des objets est generalement etudiee en laboratoire par la situation experimentale du rod france test (fft). Les erreurs d'ajustement d'une baguette a la verticale dans le sens du cadre incline s'expliquent par le phenomene de contraste d'orientation mais ainsi, l'effet cadre est attribuable a l'activite du stysteme visuel ambiant qui repond principalement a des stimulations de la retine peripherique. Cependant la taille angulaire limite de certains dispositifs (i. E. 28 ) s'oppose a cette definition. Ce travail exploratoire sur la localisation des fixations oculaires au cours du rft, montre clairement que les orientations statiques du cadre sont en partie fovealisees, en particulier par les sujets sensibles a la perturbation, le rft illustrant la possibilite d'une cooperation entre les deux mecanismes, foveal et peripherique. De plus, ce style d'exploration visuelle est stable puisqu'il resiste aux variations situationnlles du rft (cadre droit, corps incline, presentation tachistoscopique, lumiere stroboscopique, ajustement haptique). Enfin, ces recherches nous ont amenes a etudier d'autres proprietes determinantes de l'effet cadre (caracteristiques temporelles) et a preciser la relation entre cet effet perturbateur et les informations visuelles statiques et dynamiques d'equilibration posturaleThe influence of visual surroundings on apprent orientation of objets and posture is studied by the rod and france (rft). Adjustment errors of a rod to the verticalm which err in the direction of the frame tilt can be explained in terms of orientation constrast and vection. This last factor considers the frame effect as an exemple of ambient system processing which mainly responds to the stimulation of peripheral retina. However this effect is observed with displays subtending smaller visual angle (i. E. 28o ) than those usually employed to produce vection. These studies, concerned specifically with the location of foveal fixations during the rft, show that the static orientations of the frame are fovealized, in particular by subjects sensitive to the perturbation. Thus, the rft illustrates a possible co-operation between the two mechanisms, focal and peripheral. Moreover, visual scanning is stable whatever the experiment (upright frame, body tilted, tachistoscopic presentation, stroboscopic lighting, haptic adjustment). Finally, these researches study temporal characteristics of the frame effect and the relationship between this effect and static and dynamic visual cues involved in posture
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Gustave-Dit-Duflo, Sylvie. "Adaptation et restauration des fonctions vestibulaires : Analyses comportementale et cellulaire après lésion ou stimulation vestibulaire chez l'animal." Montpellier 2, 1998. http://www.theses.fr/1998MON20128.
Full textAbstract:
La thematique generale de ces travaux de these est la plasticite des fonctions vestibulaires examinee par une double approche comportementale et immunohistochimique chez le chat et le rat. Le volet comportemental consiste en une etude electrophysiologique de la reorganisation des mecanismes de stabilisation du regard apres lesion unilaterale ou bilaterale du nerf vestibulaire. Les resultats obtenus chez les animaux leses testes aux stades precoce ou compense montrent l'emergence de processus de substitution sensorielle d'origine visuelle et labyrinthique ou comportementale caracterisee par l'apparition d'une nouvelle strategie motrice de coactivation des muscles antagonistes du cou. Le volet immunochistochimique decrit les modifications de l'expression fos soit apres neurectomie vestibulaire unilaterale, soit apres variation du vecteur gravitaire modifiant l'activite le systeme otolithique. Apres lesion vestibulaire, une expression fos asymetrique est detectee au sein des noyaux vestibulaires et dans des structures associees, caracterisee par une induction precoce qui refleterait des modifications cellulaires directement liees a la deafferentation des noyaux vestibulaires, et une induction retardee serait correlee a la mise en place de mecanismes de plasticite cellulaire. L'exposition prolongee de rats dans un milieu hypergravitaire n'est pas source d'expression fos, alors qu'une transition de courte duree d'un milieu hypergravitaire vers un milieu hypogravitaire, ou l'inverse, entraine une forte expression fos. Ces resultats temoignent d'une activation de voies vestibulo-corticale et vestibulo-vegetative. Par ailleurs, ce sont les memes structures du tronc cerebral qui sont fos-positives apres lesion vestibulaire ou stimulation otolithique, suggerant que ce sont les memes reseaux neuronaux qui sous-tendraient la plasticite post-lesionnelle et la plasticite adaptative du systeme vestibulaire.
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Pinville, Tony. "Robotique évolutionniste : influence des pressions de sélection sur l'émergence d'une forme de mémoire interne." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-00794343.
Full textAbstract:
La robotique évolutionniste vise à concevoir des machines capables d'apprendre continuellement des savoir-faire nouveaux dans un monde continu, non contrôlé et changeant. Cette méthode a permis de construire avec succès des robots réels exhibant des comportements réactifs complexes. L'une des prochaines étapes est désormais de réussir à concevoir des architectures de contrôle pourvus de capacités plus cognitives. La mémoire est un élément central de la cognition, mettre en œuvre des méthodes permettant aux robots d'acquérir cette capacité peut être vu comme un premier jalon nécessaire à la réalisation de comportements cognitifs de plus haut niveau. Partant de ce constat, l'objectif de cette thèse est d'étudier la synthèse d'architectures de contrôle pour robot, capable de réaliser des tâches nécessitant le développement d'une forme de mémoire interne. Nous émettons l'hypothèse que faire émerger une capacité de mémoire au sein d'une architecture de contrôle est un problème trompeur, la robotique évolutionniste ayant tendance à générer des agents prenant seulement en considération leurs perceptions courantes. Nous proposons une approche basée sur l'utilisation de différentes pressions de sélection afin d'éviter une convergence prématurée vers des individus au comportement réactif. Nous montrons que pour favoriser l'émergence d'une mémoire interne, il est nécessaire : d'utiliser une fitness discrète qui n'introduit pas un gradient pouvant tendre vers un optimum local; de mettre en place des mécanismes de diversités comportementales afin d'explorer efficacement l'espace de recherche; de développer différents objectifs auxiliaires pour garantir une mémoire robuste.
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Carvajal, Carlos. "Dynamic interplay between standard and non-standard retinal pathways in the early thalamocortical visual system : A modeling study." Electronic Thesis or Diss., Université de Lorraine, 2014. http://www.theses.fr/2014LORR0209.
Full textAbstract:
Comprendre le comportement du système visuel rétino-thalamo-cortico-colliculaire (i.e. précoce) dans une situation d'images naturelles est d'une importance capitale pour comprendre ce qui se passe ensuite dans le cerveau. Pour comprendre ces comportements, les neurobiologistes ont étudié les voies standard, Parvocellulaires et Magnocellulaires, depuis des décennies. Cependant, il y a aussi la voie non-standard, ou Koniocellulaire, qui joue un rôle modulateur important dans les traitements local, global, et entremêlé, pour atteindre de tels comportements. Particulièrement, l'analyse standard du mouvement réalisée par la voie Magno est alternée avec des réactions rapides, comme la fuite ou l'approche à des mouvements spécifiques, qui sont pré-câblés dans la voie Konio. De plus, l'étude d'une tâche de fixation dans une situation réelle, par exemple quand un prédateur s'approche lentement de sa proie, implique non seulement un mécanisme de mouvement, mais nécessite également l'utilisation de la voie Parvo, qui analyse, au moins, le contraste de l'image. Ici, nous étudions dans un modèle neuronal de calcul bio-inspiré comment ces voies peuvent être modélisées avec un ensemble minimal de paramètres, afin de fournir des résultats numériques robustes lors d'une tâche réelle. Ce modèle repose sur une étude approfondie pour intégrer des éléments biologiques dans l'architecture des circuits, les constantes de temps et les caractéristiques de fonctionnement des neurones. Nos résultats montrent que notre modèle, bien que fonctionnant via des calculs locaux, montre globalement un bon comportement de réseau en termes d'espace et de temps, et permet d'analyser et de proposer des interprétations de l'interaction entre le thalamus et le cortex. À une échelle plus macroscopique, les comportements du modèle sont reproductibles et peuvent être qualitativement comparés à des mesures de fixation oculaire chez l'homme. Cela est également vrai lorsque l'on utilise des images naturelles, où quelques paramètres sont légèrement modifiés, en gardant des résultats qualitativement humains. Les résultats de robustesse montrent que les valeurs précises des paramètres ne sont pas critiques, mais leur ordre de grandeur l'est. Une instabilité numérique ne se produit qu'après une variation de 100% d'un paramètre. Nous pouvons donc conclure que cette approche systémique est capable de représenter les changements de l'attention en utilisant des images naturelles, tout en étant algorithmiquement robuste. Cette étude nous donne ainsi une interprétation possible sur le rôle de la voie Konio, tandis qu'en même temps elle nous permet de participer au débat sur les low et high-roads des flux attentionnel et émotionnel. Néanmoins, d'autres informations, comme la couleur, sont également présentes dans le système visuel précoce, et pourraient être prises en considération, ainsi que des mécanismes corticaux plus complexes, dans les perspectives de ce travailUnderstanding the behavior of the retino-thalamo-cortico-collicular (i.e. early) visual system in a natural images situation is of utmost importance to understand what further happens in the brain. To understand these behaviors, neuroscientists have looked at the standard Parvocellular and Magnocellular pathways for decades. However, there is also the non-standard Koniocellular pathway, which plays an important modulating role in the local, global, and intermingled processing carried out to achieve such behaviors. Particularly, the standard motion analysis carried out by the Magno pathway is alternated with rapid reactions, like fleeing or approaching to specific motions, which are hard-wired in the Konio pathway. In addition, studying a fixation task in a real situation, e.g., when a predator slowly approaches its prey, not only involves a motion mechanism, but also requires the use of the Parvo pathway, analyzing, at least, the image contrast. Here, we study in a bio-inspired computational neural model how these pathways can be modeled with a minimal set of parameters, in order to provide robust numerical results when doing a real task. This model is based upon an important study to integrate biological elements about the architecture of the circuits, the time constants and the operating characteristics of the different neurons. Our results show that our model, despite operating via local computations, globally shows a good network behavior in terms of space and time, and allows to analyze and propose interpretations to the interplay between thalamus and cortex. At a more macroscopic scale, the behaviors emerging from the model are reproducible and can be qualitatively compared to human-made fixation measurements. This is also true when using natural images, where just a few parameters are slightly modified, keeping the qualitatively human-like results. Robustness results show that the precise values of the parameters are not critical, but their order of magnitude matters. Numerical instability occurs only after a 100% variation of a parameter. We thus can conclude that such a reduced systemic approach is able to represent attentional shifts using natural images, while also being algorithmically robust. This study gives us as well a possible interpretation about the role of the Konio pathway, while at the same time allowing us to participate in the debate between low and high-roads in the attentional and emotional streams. Nevertheless, other information, such as color, is also present in the early visual system, and should be addressed together with more complex cortical mechanisms in a sequel of this work
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Carvajal, Carlos. "Dynamic interplay between standard and non-standard retinal pathways in the early thalamocortical visual system : A modeling study." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0209/document.
Full textAbstract:
Comprendre le comportement du système visuel rétino-thalamo-cortico-colliculaire (i.e. précoce) dans une situation d'images naturelles est d'une importance capitale pour comprendre ce qui se passe ensuite dans le cerveau. Pour comprendre ces comportements, les neurobiologistes ont étudié les voies standard, Parvocellulaires et Magnocellulaires, depuis des décennies. Cependant, il y a aussi la voie non-standard, ou Koniocellulaire, qui joue un rôle modulateur important dans les traitements local, global, et entremêlé, pour atteindre de tels comportements. Particulièrement, l'analyse standard du mouvement réalisée par la voie Magno est alternée avec des réactions rapides, comme la fuite ou l'approche à des mouvements spécifiques, qui sont pré-câblés dans la voie Konio. De plus, l'étude d'une tâche de fixation dans une situation réelle, par exemple quand un prédateur s'approche lentement de sa proie, implique non seulement un mécanisme de mouvement, mais nécessite également l'utilisation de la voie Parvo, qui analyse, au moins, le contraste de l'image. Ici, nous étudions dans un modèle neuronal de calcul bio-inspiré comment ces voies peuvent être modélisées avec un ensemble minimal de paramètres, afin de fournir des résultats numériques robustes lors d'une tâche réelle. Ce modèle repose sur une étude approfondie pour intégrer des éléments biologiques dans l'architecture des circuits, les constantes de temps et les caractéristiques de fonctionnement des neurones. Nos résultats montrent que notre modèle, bien que fonctionnant via des calculs locaux, montre globalement un bon comportement de réseau en termes d'espace et de temps, et permet d'analyser et de proposer des interprétations de l'interaction entre le thalamus et le cortex. À une échelle plus macroscopique, les comportements du modèle sont reproductibles et peuvent être qualitativement comparés à des mesures de fixation oculaire chez l'homme. Cela est également vrai lorsque l'on utilise des images naturelles, où quelques paramètres sont légèrement modifiés, en gardant des résultats qualitativement humains. Les résultats de robustesse montrent que les valeurs précises des paramètres ne sont pas critiques, mais leur ordre de grandeur l'est. Une instabilité numérique ne se produit qu'après une variation de 100% d'un paramètre. Nous pouvons donc conclure que cette approche systémique est capable de représenter les changements de l'attention en utilisant des images naturelles, tout en étant algorithmiquement robuste. Cette étude nous donne ainsi une interprétation possible sur le rôle de la voie Konio, tandis qu'en même temps elle nous permet de participer au débat sur les low et high-roads des flux attentionnel et émotionnel. Néanmoins, d'autres informations, comme la couleur, sont également présentes dans le système visuel précoce, et pourraient être prises en considération, ainsi que des mécanismes corticaux plus complexes, dans les perspectives de ce travailUnderstanding the behavior of the retino-thalamo-cortico-collicular (i.e. early) visual system in a natural images situation is of utmost importance to understand what further happens in the brain. To understand these behaviors, neuroscientists have looked at the standard Parvocellular and Magnocellular pathways for decades. However, there is also the non-standard Koniocellular pathway, which plays an important modulating role in the local, global, and intermingled processing carried out to achieve such behaviors. Particularly, the standard motion analysis carried out by the Magno pathway is alternated with rapid reactions, like fleeing or approaching to specific motions, which are hard-wired in the Konio pathway. In addition, studying a fixation task in a real situation, e.g., when a predator slowly approaches its prey, not only involves a motion mechanism, but also requires the use of the Parvo pathway, analyzing, at least, the image contrast. Here, we study in a bio-inspired computational neural model how these pathways can be modeled with a minimal set of parameters, in order to provide robust numerical results when doing a real task. This model is based upon an important study to integrate biological elements about the architecture of the circuits, the time constants and the operating characteristics of the different neurons. Our results show that our model, despite operating via local computations, globally shows a good network behavior in terms of space and time, and allows to analyze and propose interpretations to the interplay between thalamus and cortex. At a more macroscopic scale, the behaviors emerging from the model are reproducible and can be qualitatively compared to human-made fixation measurements. This is also true when using natural images, where just a few parameters are slightly modified, keeping the qualitatively human-like results. Robustness results show that the precise values of the parameters are not critical, but their order of magnitude matters. Numerical instability occurs only after a 100% variation of a parameter. We thus can conclude that such a reduced systemic approach is able to represent attentional shifts using natural images, while also being algorithmically robust. This study gives us as well a possible interpretation about the role of the Konio pathway, while at the same time allowing us to participate in the debate between low and high-roads in the attentional and emotional streams. Nevertheless, other information, such as color, is also present in the early visual system, and should be addressed together with more complex cortical mechanisms in a sequel of this work
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CHANG, CHIN-FU, and 張錦富. "Effects of Different Screen Sizes on Vision and Physiology." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/6rs7an.
Full textAbstract:
碩士中華大學
工業管理學系
106
ABSTRACT According to the statistics of the network information center, there have the number of internet users over the age of 12 reached 17.6 million, and the number of internet users nationwide has reached 18.79 million, and the overall internet access rate has reached 80.0% , and the proportion of households in the country has reached 82.3% , people read visually on the screen very frequently. With the advancement of technology, the screen size is getting bigger and bigger, and it has a greater impact on people's eyes. This study explores the effects of screen size on visual acuity and visual fatigue. According to research by scholars at home and abroad, line of sight can also be used as an indicator of visual fatigue, especially the screen's ability to project information, videos, games, data complexity, detail, and quantity in the close range has become an important factor affecting performance and visual fatigue during use. This study will understand the impact of different screen sizes on the human body's vision and visual fatigue, and in the future provide designers with reference to the screen size application and the user's purchase. In this study, the analysis of single-factor covariates means that the close-range work or observation has a great impact on the eye's projection and a large amount of light causing eyesight flash and radiation, and the user should keep a certain distance from the screen during the operation and advise the user to rest their eyes for a period of time after working for a period of time, It can solve the physiological effects such as vision loss and visual fatigue caused by unreasonable angle of view or distance. Keywords: screen, visual fatigue, single factor variance, single factor covariate
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Kang, Incheol. "Scotopic vision : behavioral sensitivity and underlying optical and neural factors /." 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3242890.
Full textAbstract:
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006.Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6222. Adviser: Joseph G. Malpeli. Includes bibliographical references (leaves 151-162) Available on microfilm from Pro Quest Information and Learning.
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"An investigation into radiographic sharpness & contrast." Chinese University of Hong Kong, 1995. http://library.cuhk.edu.hk/record=b5888520.
Full textAbstract:
Francis Edward Mitchell.Thesis (M.Phil.)--Chinese University of Hong Kong, 1995.
Includes bibliographical references (leaves 80-81 (2nd gp.)).
Acknowledgments --- p.iii
Summary --- p.iv
Introduction --- p.1
Sharpness and contrast --- p.2
Causes of unsharpness --- p.3
Chapter i) --- Photographic unsharpness --- p.3
Chapter ii) --- Movement unsharpness --- p.6
Chapter iii) --- Geometric unsharpness --- p.8
Chapter iv) --- Exposure unsharpness --- p.12
Contrast factors --- p.15
Chapter i) --- Subject/object contrast --- p.15
Chapter ii) --- Radiation --- p.16
Chapter iii) --- Film and screen --- p.18
Chapter iv) --- Subjective --- p.20
"How do we see ""Sharpness & Contrast"" ？" --- p.21
Factors in perception --- p.26
Chapter i) --- The individuals eyesight (and age) --- p.26
Chapter ii) --- Light intensity --- p.26
Chapter iii) --- Colour --- p.27
Chapter iv) --- Pupil diameter --- p.27
Chapter v) --- Size and shape of the object --- p.28
Chapter vi) --- Eccentricity --- p.28
Chapter vii) --- Edge enhancement --- p.29
Chapter viii) --- Background luminance --- p.30
Chapter ix) --- Maximising information retrieval from an image --- p.30
Experiment I - Production of an image with controlled sharpness and contrast --- p.31
Chapter i) --- Choice of film & cassette --- p.31
Chapter ii) --- Prevention of movement unsharpness --- p.34
Chapter iii) --- Prevention of parallax --- p.34
Chapter iv) --- Control of penumbra --- p.35
Chapter v) --- Verification of image unsharpness --- p.40
Control of contrast --- p.46
Radiography of test objects --- p.48
Experiment II - Perception of sharpness at different contrast levels --- p.53
Chapter i) --- Experiment --- p.53
Chapter ii) --- "Viewing the data in terms of ""sharpness""" --- p.56
Chapter iii) --- Viewing the data in terms of contrast levels --- p.61
Analysis of data from an expanded group size (N=55) --- p.66
Experiment III - Effect of room lighting conditions on the perception of sharpness --- p.69
Overall conclusions --- p.78
Bibliography --- p.79
References --- p.80
Appendix A (VBV calculation) --- p.82
Appendix B (Line-pair test-tool) --- p.83
Appendix C (Scattered radiation) --- p.85
Photo-electric --- p.85
Compton --- p.85
Pair-production --- p.85
Net result --- p.86
Appendix D (Metal discs) --- p.87
"Appendix E (OFD, magnification and penumbra)" --- p.88
Appendix F (Processor developer temperature) --- p.90
Appendix G (Viewing contrast-sharpness data) --- p.91
Appendix H (Viewing conditions) --- p.92
Appendix I (Comparison of data - light and dark viewing conditions) --- p.94
Appendix J (Curix film & screens) --- p.97
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彭捷裕. "Study of Vision Fatigue, Dizziness and Physiology by Virtual Reality Image and Flat Sizes impacted." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/znb3m4.
Full textAbstract:
碩士中華大學
工業管理學系
106
VR (Virtual reality) has recently developed into a trend that must be followed. Virtual reality is a potential modern computer technology. With its extensive scope of application, the technology companies worldwide have been investing in the research and development of itThe development and application of virtual reality in advanced countries have already been quite common, especially the recent rapid development of application in entertainment industry. At the same time, VR can also be used in fields of military training or medical treatment. Many excellent features of virtual reality are also ideal for education. However, while using different VR devices effects of eye fatigue dizziness between VR game images and flat game images differ. Hence, researching on how to know the difference in the effects of eye fatigue dizziness between VR game images and flat game images is the main purpose of this study. The biggest difference between VR and non-VR is that in VR, the head-mounted device must be used to visually generate a VR stereo space. This is what other average screen cannot achieve. This study was to investigate the effects of visual fatigue or motion sickness in VR stereoscopic images and plane images, and to explore whether there are certain effects on the size of plane images used in different applications. This study used three kinds of equipment: VR glasses, 24” screen and 27” screen in spacious classrooms with adequate amount of lighting to do pre-test, post- test, measurement of vision, blood pressure and pulse, and filling in the subjective scale of visualfatigue and SSQ. After verifying the data of ANOVA and ANCOVA to detect the relationship between VR and flat screen, the test results show that flat screen has no significant correlation with visualfatigue dizziness, while VR images have a significant effect on visual fatigue dizziness and motionsickness. We found that due to the application of in vitual images, VR do more pressure on the eyes and the eyesight and dizziness are more obvious. As flat screen is forward dynamics and Static Square, it has no significant effects comparing to VR.Considering prolonged testing will hurt the subjects’ eyes, the test time is limited. If longer test time is allowed, the results should be possible to indicatemore obvious differences.