Dissertations / Theses on the topic 'Visual perceptual learning'

Thesis (Ph.D.)--Boston University PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.<br>A prevailing hypothesis of visual perceptual learning (VPL) is that for a feature to be learned, focused attention must be directed to that feature. Along these lines, top-down, task-related factors are also required for such learning to take place. The first aim of this thesis was to challenge these ideas by the use of a procedure in which human participants, who were deprived of food and water, passively viewed visual stimuli while receiving occasional drops of water as rewards. Visual orientation stimuli, which were temporally paired with the liquid-rewards, were viewed monocularly and rendered imperceptible by continuously flashing contour rich patterns to the other eye. Results show that VPL can occur not only as a result of task-involvements but also as a result of stimulus-reward pairing in the absence of any task and without awareness of the stimulus presentation. Thus, a question arises as to whether reward-driven exposure-based VPL (REVPL) occurs in the same way as reward-driven task-based VPL (RTVPL). The second aim of this thesis was to investigate whether there are different properties in REVPL and RTVPL by combining VPL and a training procedure employing classical or operant conditioning. Results show different learning patterns between REVPL and RTVPL, suggesting that the mechanism of REVPL is not the same as that of RTVPL. Furthermore, neither REVPL nor RTVPL followed the rules of conditioning. These findings indicate that the underlying mechanism between VPL and conditioning is different. It was shown that VPL could occur without awareness of the stimulus presentation. However, there has been little research on the influence of weak or invisible stimuli. In the third aim, the incident probability of two alternative orientations were manipulated to examine how human observers' choices are influenced by past and present changes in probability. Results show that perceptual decision-making can be influenced to a greater degree by past incidence of weak signals than by stronger signals. In summary, VPL can arise through stimulus-reward pairing in the absence of a task and without awareness of the stimulus presentation. Furthermore, weak or invisible stimuli have great effects on visual learning and perceptual decision-making.

The role of excitatory processes in human visual learning has been well characterised through the use of technologies such as functional magnetic resonance imaging (fMRI). However, established imaging modalities do not distinguish excitatory processes from the inhibitory ones that are also involved. Here we investigate inhibitory processes using magnetic resonance spectroscopy (MRS) and the MEGA-PRESS pulse sequence. We measure concentrations of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) in different brain regions as functional markers of inhibitory potential. We then investigate the correlations between GABA concentrations and psychophysical learning metrics. We detail a full analysis pipeline that improves the accuracy of in vivo GABA quantification and introduce new scaling methods to resolve the grey matter contribution to metabolite measurements. We develop visual learning experiments that are mediated by training difficulty, which we link to inhibitory processes across different time scales. We also present novel evidence for GABAergic inhibitory mechanisms across multiple brain areas using fine and coarse discrimination tasks. Our results support a cooperative top-down and bottom-up model of visual learning in occipital and frontal cortical regions. Our findings reveal chemical interactions with cognition to contribute to our understanding of inhibitory processes in the human learning brain.

Identifying targets in cluttered scenes is critical for our interactions in complex environments. Our visual system is challenged to both detect elusive targets that we may want to avoid or chase and discriminate between targets that are highly similar. These tasks require our visual system to become an expert at detecting distinctive features that help us differentiate between indistinguishable targets. As the human brain is trained on this type of visual tasks, we observe changes in its function that correspond to improved performance. We use functional brain imaging, to measure learning-dependent modulations of brain activation and investigate the processes that mediate functional brain plasticity. I propose that dissociable brain mechanisms are engaged when detecting targets in clutter vs. discriminating between highly similar targets: for the former, background clutter needs to be suppressed for the target to be recognised, whereas for the latter, neurons are tuned to respond to fine differences. Although GABAergic inhibition is known to suppress redundant neuronal populations and tune neuronal representations, its role in visual learning remains largely unexplored. Here, I propose that GABAergic inhibition plays an important role in visual plasticity through training on these tasks. The purpose of my PhD is to investigate the inhibitory mechanisms that mediate visual perceptual learning; in particular, learning to detect patterns in visual clutter and discriminate between highly similar patterns. I show that BOLD signals as measured by functional Magnetic Resonance Imaging (fMRI) do not differentiate between the two proposed mechanisms. In contrast, Magnetic Resonance Spectroscopy (MRS) provides strong evidence for the distinct involvement of GABAergic inhibition in visual plasticity. Further, my findings show GABA changes during the time-course of learning providing evidence for a distinct role of GABA in learning-dependent plasticity across different brain regions involved in visual learning. Finally, I test the causal link between inhibitory contributions and visual plasticity using a brain stimulation intervention that perturbs the excitation-inhibition balance in the visual cortex and facilitates learning.

Aim: The aim of the present study was to examine the outcome of repetitive-part training and dual-task training in the acquisition of dribbling technique and decision making in prepubescent novice soccer players. Method: Twenty four preschool pupils, with an age of 6.2 ± 0.4 years (mean ± SD) and with no previous experience of partaking in any organized team or ball sport participated in the study. The participants were tested (pre test) for initial performance level of dribbling technique and decision making and were then divided into two balanced experimental groups. The repetitive-part group underwent four weeks of part-task training (isolated dribbling-technique training) which were followed by four weeks of dual-task training (simultaneous training of dribbling technique and decision making). The dual-task group underwent eight weeks of dual-task training. The outcome in acquisition of dribbling technique and decision making was examined after four (mid test) and eight (post test) weeks of training. Both training regimes were followed by four weeks of non-training and thereafter a test (retention test) of the retention effects was carried out. Effect sizes (d) of the acquisition within each group and of the difference in performance and acquisition between the two groups were evaluated based on Cohen's effect size criteria (|d| &gt; 0.2, small effect; |d| &gt; 0.5, moderate effect; |d| &gt; 0.8, large effect). Results: Between the pre and mid test, both groups showed large improvements in dribbling technique. The corresponding improvement was small in the repetitive-part group and moderate in the dual-task group between the mid and post test. There were large differences between the groups' decision-making performances at the mid, post, and retention test where the dual-task group was superior to the repetitive-part group. The dual task group showed large improvements of decision making between the pre and mid test. Between the mid and post test, the corresponding effect was large within the repetitive-part group and moderate in the dual-task group. The improvement of the dual-task group's decision making between the pre and mid test was greater than the corresponding improvement showed by the repetitive-part group, between the mid and post test. This difference produced a moderate effect size. Conclusions: These findings challenge conventional repetitive-part training regimes and, with references to previous research, emphasize the importance of dual-task training for skill acquisition in prepubescent novice soccer players.

Sensory substitution devices are a non-invasive visual prostheses that use sound or touch to aid functioning in the blind. Algorithms informed by natural crossmodal correspondences convert and transmit sensory information attributed to an impaired modality back to the user via an unimpaired modality and utilise multisensory networks to activate visual areas of cortex. While behavioural success has been demonstrated in non-visual tasks suing SSDs how they utilise a metamodal brain, organised for function is still a question in research. While imaging studies have shown activation of visual cortex in trained users it is likely that naïve users rely on auditory characteristics of the output signal for functionality and that it is perceptual learning that facilitates crossmodal plasticity. In this thesis I investigated visual-to-auditory sensory substitution in naïve sighted users to assess whether signal complexity and processing in the auditory system facilitates and limits simple recognition tasks. In four experiments evaluating; signal complexity, object resolution, harmonic interference and information load I demonstrate above chance performance in naïve users in all tasks, an increase in generalized learning, limitations in recognition due to principles of auditory scene analysis and capacity limits that hinder performance. Results are looked at from both theoretical and applied perspectives with solutions designed to further inform theory on a multisensory perceptual brain and provide effective training to aid visual rehabilitation.

Perceptual learning is the ability to improve performance of a perceptual task, with repeated practice. The concept of perceptual learning in the adult visual system has been established for many years, however, the neural mechanisms which mediate it have proved complex to unravel. Improved understanding could be used to guide novel rehabilitative strategies for those with damage to the brain which affects the primary visual cortex (V1) in the occipital lobe. Motion perception learning is thought to involve the brain area hMT+, which is located in the parieto-temporo- occipital cortex, distal from V1. It is possible that motion perception training may improve the vision or subjective quality of life for individuals with damage to V1. This project initially looked at the effect of motion perception training in healthy individuals, in order to establish and quantify the potential behavioural and neural impact of behavioural training. A five-day motion perception training paradigm applied in these experiments produced robust improvement of motion perception in healthy participants. This learning was found to be partially transferable to untrained regions of the visual field. If the training timecourse was reduced to a single day, the location specificity of learning effects was increased significantly. Functional MRI analysis indicated that the motion perception training paradigm applied here altered activity at extrastriate visual areas and frontotemporal decision areas. When motion perception training was combined with brain stimulation, it was shown that 20 minutes of anodal transcranial direct current stimulation (tDCS) over hMT+ had no impact on learning magnitude or timecourse. Finally, the motion perception training paradigm was applied as a case study in a patient with damage to V1. The results were promising but inconclusive with such a minimal dataset. Motion perception training produces robust improvements in perception in healthy individuals, which are likely mediated by visual extrastriate and decision-making areas of the brain. As such, motion perception training shows promise, with further development, as an avenue for rehabilitation of the visual system and visual perception following damage to the primary visual cortex.

This thesis is concerned with describing and experimentally investigating the nature of perceptual learning. Ecological psychology defines perceptual learning as a process of educating attention to structural properties of stimuli (i.e., invariants) that specify meaning (i.e., affordances) to the perceiver. Although such definition comprehensively describes the questions of what humans learn to perceive, it does not address the question of how learning occurs. It is proposed in this thesis that the principles of classical and operant conditioning can be used to strengthen and expand the ecological account of perceptual learning. The perceptual learning of affordances is described in terms of learning that a stimulus is associated with another stimulus (classical conditioning), and in terms of learning that interacting with a stimulus is associated with certain consequences (operant conditioning). Empirical work in this thesis investigated the effect of conditioning on pitch and speech perception. Experiments 1, 2, and 3 were designed to modify pitch perception in Shepard tones via tone-colour associative training. During training, Shepard tones were paired with coloured circles in a way that the colour of the circles could be predicted by either the F0 (pitch) or by an F0-irrelevant auditory invariant. Participants were required to identify the colour of the circles that was associated with the tones and they received corrective feedback. Hypotheses were based on the assumption that F0-relevant/F0- irrelevant conditioning would increase/decrease the accuracy of pitch perception in Shepard tones. Experiment 1 investigated the difference between F0-relevant and F0- irrelevant conditioning in a between-subjects design, and found that pitch perception in the two conditions did not differ. Experiments 2 and 3 investigated the effect of F0- relevant and F0-irrelevant conditioning (respectively) on pitch perception using a within subjects (pre-test vs. post-test) design. It was found that the accuracy of pitch perception increased after F0-relevant conditioning, and was unaffected by F0-irrelevant conditioning. The differential trends observed in Experiments 2 and 3 suggest that conditioning played some role in influencing pitch perception. However, the question whether the observed trends were due to the facilitatory effect of F0-relevant conditioning or the inhibitory effect of F0-irrelevant conditioning warrants future investigation. Experiments 4, 5, and 6 were designed to modify the perception of McGurk syllables (i.e., auditory /b/ paired with visual /g/) via consonant-pitch associative training. During training, participants were repeatedly presented with /b/, /d/, and /g/ consonants in falling, flat, and rising pitch contours, respectively. Pitch contour was paired with either the auditory signal (Experiments 4 and 5) or the visual signal (Experiment 6) of the consonant. Participants were required to identify the stop consonants and they received corrective feedback. The perception of McGurk stimuli was tested before and after training by asking participants to identify the stop consonant in each stimulus as /b/ or /d/ or /g/. It was hypothesized that conditioning would increase (1) /b/ responses more in the falling than in the flat/ rising contour conditions, (2) /d/ responses more in the flat than in the falling/ rising contour conditions, and (3) /g/ responses more in the rising than in the falling/flat contour conditions. Support for the hypotheses was obtained in Experiments 5 and 6, but only in one response category (i.e., /b/ and /g/ response categories, respectively). It is suggested that the subtlety of the observed conditioning effect could be enhanced by increasing the salience of pitch contour and by reducing the clarity of auditory/visual invariants that specify consonants.

Ce travail vise à mieux évaluer la qualité perceptuelle des images contenant des distorsions structurelles et géométriques notamment dans le contexte de médias immersifs. Nous proposons et explorons un cadre algorithmique hiérarchique de la perception visuelle. Inspiré par le système visuel humain, nous investiguons plusieurs niveaux de représentations des images : bas niveau (caractéristiques élémentaires comme les segments), niveau intermédiaire (motif complexe, encodage de contours), haut niveau (abstraction et reconnaissance des données visuelles). La première partie du manuscrit traite des représentations bas niveau pour la structure et texture. U n modèle basé filtre bilatéral est d’abord introduit pour qualifier les rôles respectifs de l’information texturale et structurelle dans diverses tâches d’évaluation (utilité, qualité. . . ). Une mesure de qualité d’image/vidéo est proposée pour quantifier les déformations de structure spatiales et temporelles perçues en utilisant une métrique dite élastique. La seconde partie du mémoire explore les représentations de niveaux intermédiaires. Un modèle basé « schetch token » et un autre basé sur codage d’un arbre de contexte sont présentés pour évaluer la qualité perçue. La troisième partie traite des représentations haut niveau. Deux approches d’apprentissage machine sont proposées pour apprendre ces représentations : une basée sur un technique de convolutional sparse coding, l’autre sur des réseaux profonds de type generative adversarial network. Au long du manuscrit, plusieurs expériences sont menées sur différentes bases de données pour plusieurs applications (FTV, visualisation multi-vues, images panoramiques 360. . . ) ainsi que des études utilisateurs<br>This work aims to better evaluate the perceptual quality of image/video that contains structural and geometric related distortions in the context of immersive multimedia. We propose and explore a hierarchical framework of visual perception for image/video. Inspired by representation mechanism of the visual system, low-level (elementary visual features, e.g. edges), mid-level (intermediate visual patterns, e.g. codebook of edges), and higher-level (abstraction of visual input, e.g. category of distorted edges) image/video representations are investigated for quality assessment. The first part of this thesis addresses the low-level structure and texture related representations. A bilateral filter-based model is first introduced to qualify the respective role of structure and texture information in various assessment tasks (utility, quality . . . ). An image quality/video quality measure is proposed to quantify structure deformation spatially and temporally using new elastic metric. The second part explores mid-level structure related representations. A sketch-token based model and a context tree based model are presented in this part for the image and video quality evaluation. The third part explores higher-level structure related representations. Two machine learning approaches are proposed to learn higher-level representation: a convolutional sparse coding based and a generative adversarial network. Along the thesis, experiments an user studies have been conducted on different databases for different applications where special structure related distortions are observed (FTV, multi-view rendering, omni directional imaging . . . )

Thesis (Ph.D.)--University of Western Sydney, 2007.<br>A thesis submitted to the University of Western Sydney, College of Arts, School of Psychology in fulfilment of the requirements for the degree of Doctor of Philosophy. Includes bibliography.

The purpose of the project was to determine if a school-wide intervention for students demonstrating symptons of Irlen Syndrome would result in improvements in reading skills and a reduction in physical symptoms that might impede visual processing necessary for successful reading.

Developing advanced semantic models is important in building computational systems that can not only understand language but also convey ideas and concepts to others. Semantic models can allow a creative image-producing-agent to autonomously produce artifacts that communicate an intended meaning. This notion of communicating meaning through art is often considered a necessary part of eliciting an aesthetic experience in the viewer and can thus enhance the (perceived) creativity of the agent. Computational creativity, a subfield of artificial intelligence, deals with designing computational systems and algorithms that either automatically create original and functional products, or that augment the ability of humans to do so. We present work on DARCI (Digital ARtist Communicating Intention), a system designed to autonomously produce original images that convey meaning. In order for DARCI to automatically express meaning through the art it creates, it must have its own semantic model that is perceptually grounded with visual capabilities.The work presented here focuses on designing, building, and incorporating advanced semantic and perceptual models into the DARCI system. These semantic models give DARCI a better understanding of the world and enable it to be more autonomous, to better evaluate its own artifacts, and to create artifacts with intention. Through designing, implementing, and studying DARCI, we have developed evaluation methods, models, frameworks, and theories related to the creative process that can be generalized to other domains outside of visual art. Our work on DARCI has even influenced the visual art community through several collaborative efforts, art galleries, and exhibits. We show that the DARCI system is successful at autonomously producing original art that is meaningful to human viewers. We also discuss insights that our efforts have contributed to the field of computational creativity.

La dégénérescence maculaire (DM) est une pathologie visuelle fréquente dans la population vieillissante, qui se caractérise par une perte de la vision centrale, une diminution de la sensibilité au contraste et de l'acuité visuelle. Cette déficience affecte fortement la qualité de vie et l'autonomie . Il n'existe actuellement aucun traitement curatif de la DMLA, les options thérapeutiques disponibles ne permettant que de ralentir l'évolution de la maladie, avec de rares traitements palliatifs. Après l'apparition du scotome central, les patients atteints de DM développent une ou plusieurs zones de fixations excentrées - les lieux rétiniens préférentiels (PRLs) - qui sont utilisées pour la fixation, la lecture, et d'autres tâches visuelles qui nécessitent des capacités oculaires plus fines. L'objectif principal du projet était d'étudier et d'améliorer les capacités visuelles résiduelles dans les PRL. En tout quatre études ont été menées L'étude 1 a été menée chez des patients atteints de DMLA afin de déterminer si, après l'apparition du scotome, le PRL acquiert des capacités accrues dans le traitement de l'information visuelle grâce à une plasticité adaptative spontanée ou dépendante de l'utilisation. L'étude 2 visait à évaluer les effets d'une seule stimulation électrique transcrânienne à bruit aléatoire (tRNS), une variante de stimulation électrique non-invasive, sur l'intégration spatiale dans le cortex visuel sain. L'étude 3 visait à évaluer chez des sujets sains l'effet d'une répétition quotidienne du tRNS associée à un entraînement perceptif entre les séances. L'objectif de l'étude 4 était de traduire ces résultats en une approche clinique en combinant la tRNS et l'entraînement perceptif chez des patients adultes atteints de DMLA. Nous n'avons trouvé aucun phénomène de plasticité corticale spontanée ou dépendante de l'utilisation dans la PRL avant l'entraînement contrairement à ce qui avait été montré dans d'autres études. Nous avons cependant constaté que le tRNS était capable de moduler l'intégration visuospatiale dans le traitement visuel précoce, en favorisant les changements plastiques dans le réseau stimulé. Les effets de la tRNS ne se sont pas limités à la modulation à court terme, mais ont également produit un renforcement de l'apprentissage dans une tâche d'encombrement spatial. L'expérience finale a montré chez les adultes atteints de DMLA qu'une combinaison de la tRNS et de l'apprentissage perceptif pouvait induire des améliorations plus importantes et un transfert accentué vers des tâches visuelles non entrainées que le seul apprentissage perceptif. Dans l'ensemble, nos résultats indiquent que la tRNS du cortex visuel peut être utilisée comme thérapie supplémentaire pour améliorer la vision chez les adultes atteints de cécité centrale bilatérale<br>Macular degeneration (MD) is a common visual disorder in the aging population characterized by a loss of central vision, reduced visual acuity contrast sensitivity, and increased crowding. This impairment strongly affects the quality of life and personal autonomy. There is currently no cure for AMD, available treatment options are only able to slow down the disease, and even palliative treatments are rare. After the emergence of the central scotoma, patients with MD develop one or more eccentric fixation areas - preferred retinal loci (PRLs) - that are used for fixation, reading, tracking, and other visual tasks that require finer ocular abilities. The final goal of the project was to investigate and to improve the residual visual abilities in the PRL. Four studies were conducted in total. Study 1 was conducted in MD patients to investigate whether after the emergence of the scotoma, the PRL acquire enhanced abilities in the processing of the visual information through spontaneous or use-dependent adaptive plasticity. Study 2 aimed to assess the effects of a single administration of transcranial random noise electrical stimulation (tRNS), a subtype of non-invasive transcranial electrical stimulation, on the spatial integration in the healthy visual cortex. Study 3 aimed to assess the between session effect of daily repeated tRNS coupled with perceptual training. The objective of study 4 was to translate the previous findings into a clinically applicable treatment approach by combining tRNS and perceptual training in adult patients with MD. Contrary to previous results, we found neither a phenomenon of spontaneous nor use-dependent cortical plasticity undergoing in the PRL before the training. We also found that the tRNS was able to modulate the visuospatial integration in the early visual processing, promoting plastic changes in the stimulated network. Its effects were not limited to the short-term modulation but also produced a boosting of the learning in a crowding task. The final experiment showed that a combination of tRNS and perceptual training could result in greater improvements and larger transfer to untrained visual tasks in adults with MD than training alone. Overall, our results indicate that tRNS of the visual cortex has potential application as an additional therapy to improve vision in adults with bilateral central blindness

In many different spatial discrimination tasks, such as in determining the sign of the offset in a vernier stimulus, the human visual system exhibits hyperacuity-level performance by evaluating spatial relations with the precision of a fraction of a photoreceptor"s diameter. We propose that this impressive performance depends in part on a fast learning process that uses relatively few examples and occurs at an early processing stage in the visual pathway. We show that this hypothesis is plausible by demonstrating that it is possible to synthesize, from a small number of examples of a given task, a simple (HyperBF) network that attains the required performance level. We then verify with psychophysical experiments some of the key predictions of our conjecture. In particular, we show that fast timulus-specific learning indeed takes place in the human visual system and that this learning does not transfer between two slightly different hyperacuity tasks.

Thesis (M.Sc.)--York University, 2006. Graduate Programme in Kinesiology & Health Science.<br>Typescript. Includes bibliographical references (leaves 70-77). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR19733

abstract: To be a versatile violinist, one needs interdependence of aural, visual and kinesthetic skills. This thesis introduces aural, visual and kinesthetic learning modalities, and explores the way each is used in the Suzuki, Paul Rolland, Orff, Kodály, and Dalcroze methods, as well as in Edwin Gordon’s Musical Learning Theory. Other methods and pedagogical approaches were consulted and influential in developing the curriculum, such as the teaching of Mimi Zweig, but were not included in this paper either because of an overlap with other methods or insufficient comparable material. This paper additionally presents a new curriculum for teaching beginning violin that incorporates aural, visual, and kinesthetic learning in a systematic and comprehensive manner. It also details a sequenced progression to learn new repertoire and develop proficiency with rhythm, solfège, reading and writing musical notation, and left- and right-hand technique.<br>Dissertation/Thesis<br>Doctoral Dissertation Music 2017

Object experts quickly and accurately discriminate objects within their domain of expertise. Although expert recognition has been extensively studied both at the behavioral- and neural-levels in both real-world and laboratory trained experts, we know little about the visual features and perceptual strategies that the expert learns to use in order to make fast and accurate recognition judgments. Thus, the aim of this work was to identify the visual features (e.g., color, form, motion) and perceptual strategies (e.g., fixation pattern) that real-world experts employ to recognize objects from their domain of expertise. Experiments 1 to 3 used psychophysical methods to test the role of color, form (spatial frequencies), and motion, respectively, in expert object recognition. Experiment 1 showed that although both experts and novices relied on color to recognize birds at the family level, analysis of the response time distribution revealed that color facilitated expert performance in the fastest and slowest trials whereas color only helped the novices in the slower trials. Experiment 2 showed that both experts and novices were more accurate when bird images contained the internal information represented by a middle range of SFs, described by a quadratic function. However, the experts, but not the novices, showed a similar quadratic relationship between response times and SF range. Experiment 3 showed that, contrary to our prediction, both groups were equally sensitivity to global bird motion. Experiment 4, which tested the perceptual stategies of expert recognition in a gaze-contingent eye-tracking paradigm, showed that only in the fastest trials did experts use a wider range of vision. Experiment 5, which examined the neural representations of categories within the expert domain, suggested that the mechanisms that represents within-categories of faces also represented within-categories from the domain of expertise, but not the novice domain. Collectively, these studies suggest that expertise influence visual discrimination mechanisms such that they become more sensitive to the visual dimensions upon which the expert domains are discriminated.<br>Graduate<br>2018-12-12

abstract: Magnocellular-Dorsal pathway’s function had been related to reading ability, and visual perceptual learning can effectively increase the function of this neural pathway. Previous researches training people with a traditional dot motion paradigm and an integrated visual perceptual training “video game” called Ultimeyes pro, all showed improvement with regard to people’s reading performance. This research used 2 paradigms in 2 groups in order to compare the 2 paradigms’ effect on improving people’s reading ability. We also measured participants’ critical flicker fusion threshold (CFFT), which is related to word decoding ability. The result did not show significant improvement of reading performance in each group, but overall the reading speed improved significantly. The result for CFFT in each group only showed significant improvement among people who trained with Ultimeyes pro. This result supports that the beneficial effect of visual perceptual learning training on people’s reading ability, and it suggests that Ultimeyes pro is more efficient than the traditional dot motion paradigm, and might have more application value.<br>Dissertation/Thesis<br>Masters Thesis Psychology 2015

Compelling evidence stemming from past research suggests that a wide variety of visual search tasks can undergo perceptual learning. Such learning is typically characterized by a marked improvement in the speed and accuracy of target detection or identification by observers, as a result of repeated practice with the visual search task at hand. For difficult visual discriminations, the improvement in visual search performance associated with perceptual learning has been shown to be specific to the training context. Such contexts include, but are not limited to, the trained target stimuli and their trained retinal positions within the visual field. The current compilation of psychophysical experiments aimed to investigate an aspect of perceptual learning specificity in difficult visual discriminations previously unreported in the relevant literature. These experiments assessed whether perceptual learning for difficult visual discriminations is specific to the trained context of stimulus display durations in which such discriminations are embedded. With training, a significant improvement in performance for trials with a 50-millisecond stimulus display duration (difficult discriminations) resulted when such trials were embedded within sessions containing a variety of longer stimulus display durations (easier discriminations). However, this improvement was lost when difficult trials were no longer embedded within the context of easier trials. These findings may supplement our current knowledge regarding the perceptual plasticity of the visual system.

<p>Visual search, the process of detecting relevant items within an environment, is a vital skill required for navigating one's visual environment as well as for careers, such as radiology and airport security, that rely upon accurate searching. Research over the course of several decades has established that visual search requires the integration of low- and high-level cognitive processes, including sensory analysis, attentional allocation, target discrimination, and decision-making. Search abilities are malleable and vary in accordance with long-term experiences, direct practice, and contextual factors in the immediate environment; however, the mechanisms responsible for changes in search performance remain largely unclear. A series of studies examine variation in visual search abilities and performance and aim to identify the underlying mechanisms.</p><p>To assess differences associated with long-term experiences, visual search performance is compared between laypersons (typically undergraduates) and specific populations, including radiologists and avid action video game players. Behavioral markers of search processes are used to elucidate causes of enhanced search performance. To assess differences associated with direct practice, laypersons perform a visual search task over five consecutive days, and electrophysiological activity is recorded from the scalp on the first and last days of the protocol. Electrophysiological markers associated with specific stages of processing are analyzed to determine neurocognitive changes contributing to improved performance. To assess differences associated with contextual factors, laypersons are randomly assigned to experimental conditions in which they complete a visual search task within a particular framework or in the presence or absence of motivation, feedback, and/or time pressure.</p><p>Results demonstrate that search abilities can improve through experience and direct training, but the mechanisms underlying effects in each case are different. Long-term experiences are associated with strategic attentional allocation, but direct training can improve low-level sensory analysis in addition to higher-level processes. Results also demonstrate nuanced effects of experience and context. On searches that contain multiple targets, task framework impacts accuracy for detecting additional targets after one target has been identified. The combination of motivation and feedback enhances accuracy for both single- and multiple-target searches. Implications for cognitive theory and applications to occupational protocols are discussed.</p><br>Dissertation

Les cortices sensoriels sont des régions cérébrales essentielles pour la perception. En particulier, le cortex visuel traite l’information visuelle en provenance de la rétine qui transite par le thalamus. Les neurones sont les unités fonctionnelles qui transforment l'information sensorielle en signaux électriques, la transfèrent vers le cortex et l'intègrent. Les neurones du cortex visuel sont spécialisés et analysent différents aspects des stimuli visuels. La force des connections entre les neurones peut être modulée par la persistance de l'activité pré-synaptique et induit une augmentation ou une diminution du signal post-synaptique à long terme. Ces modifications de la connectivité synaptique peuvent induire la réorganisation de la carte corticale, c’est à dire la représentation de ce stimulus et la puissance de son traitement cortical. Cette réorganisation est connue sous le nom de plasticité corticale. Elle est particulièrement active durant la période de développement, mais elle s’observe aussi chez l’adulte, par exemple durant l’apprentissage. Le neurotransmetteur acétylcholine (ACh) est impliqué dans de nombreuses fonctions cognitives telles que l’apprentissage ou l’attention et il est important pour la plasticité corticale. En particulier, les récepteurs nicotiniques et muscariniques du sous-type M1 et M2 sont les récepteurs cholinergiques impliqués dans l’induction de la plasticité corticale. L’objectif principal de la présente thèse est de déterminer les mécanismes de plasticité corticale induits par la stimulation du système cholinergique au niveau du télencéphale basal et de définir les effets sur l’amélioration de la perception sensorielle. Afin d’induire la plasticité corticale, j’ai jumelé des stimulations visuelles à des injections intracorticales d’agoniste cholinergique (carbachol) ou à une stimulation du télencéphale basal (neurones cholinergiques qui innervent le cortex visuel primaire). J'ai analysé les potentiels évoqués visuels (PEVs) dans le cortex visuel primaire des rats pendant 4 à 8 heures après le couplage. Afin de préciser l’action de l’ACh sur l’activité des PEVs dans V1, j’ai injecté individuellement l’antagoniste des récepteurs muscariniques, nicotiniques, α7 ou NMDA avant l’infusion de carbachol. La stimulation du système cholinergique jumelée avec une stimulation visuelle augmente l’amplitude des PEVs durant plus de 8h. Le blocage des récepteurs muscarinique, nicotinique et NMDA abolit complètement cette amélioration, tandis que l’inhibition des récepteurs α7 a induit une augmentation instantanée des PEVs. Ces résultats suggèrent que l'ACh facilite à long terme la réponse aux stimuli visuels et que cette facilitation implique les récepteurs nicotiniques, muscariniques et une interaction avec les récepteur NMDA dans le cortex visuel. Ces mécanismes sont semblables à la potentiation à long-terme, évènement physiologique lié à l’apprentissage. L’étape suivante était d’évaluer si l’effet de l’amplification cholinergique de l’entrée de l’information visuelle résultait non seulement en une modification de l’activité corticale mais aussi de la perception visuelle. J’ai donc mesuré l’amélioration de l’acuité visuelle de rats adultes éveillés exposés durant 10 minutes par jour pendant deux semaines à un stimulus visuel de type «réseau sinusoïdal» couplé à une stimulation électrique du télencéphale basal. L’acuité visuelle a été mesurée avant et après le couplage des stimulations visuelle et cholinergique à l’aide d’une tâche de discrimination visuelle. L’acuité visuelle du rat pour le stimulus d’entrainement a été augmentée après la période d’entrainement. L’augmentation de l’acuité visuelle n’a pas été observée lorsque la stimulation visuelle seule ou celle du télencéphale basal seul, ni lorsque les fibres cholinergiques ont été lésées avant la stimulation visuelle. Une augmentation à long terme de la réactivité corticale du cortex visuel primaire des neurones pyramidaux et des interneurones GABAergiques a été montrée par l’immunoréactivité au c-Fos. Ainsi, lorsque couplé à un entrainement visuel, le système cholinergique améliore les performances visuelles pour l’orientation et ce probablement par l’optimisation du processus d’attention et de plasticité corticale dans l’aire V1. Afin d’étudier les mécanismes pharmacologiques impliqués dans l’amélioration de la perception visuelle, j’ai comparé les PEVs avant et après le couplage de la stimulation visuelle/cholinergique en présence d’agonistes/antagonistes sélectifs. Les injections intracorticales des différents agents pharmacologiques pendant le couplage ont montré que les récepteurs nicotiniques et M1 muscariniques amplifient la réponse corticale tandis que les récepteurs M2 muscariniques inhibent les neurones GABAergiques induisant un effet excitateur. L’infusion d’antagoniste du GABA corrobore l’hypothèse que le système inhibiteur est essentiel pour induire la plasticité corticale. Ces résultats démontrent que l’entrainement visuel jumelé avec la stimulation cholinergique améliore la plasticité corticale et qu’elle est contrôlée par les récepteurs nicotinique et muscariniques M1 et M2. Mes résultats suggèrent que le système cholinergique est un système neuromodulateur qui peut améliorer la perception sensorielle lors d’un apprentissage perceptuel. Les mécanismes d’amélioration perceptuelle induits par l’acétylcholine sont liés aux processus d’attention, de potentialisation à long-terme et de modulation de la balance d’influx excitateur/inhibiteur. En particulier, le couplage de l’activité cholinergique avec une stimulation visuelle augmente le ratio de signal / bruit et ainsi la détection de cibles. L’augmentation de la concentration cholinergique corticale potentialise l’afférence thalamocorticale, ce qui facilite le traitement d’un nouveau stimulus et diminue la signalisation cortico-corticale minimisant ainsi la modulation latérale. Ceci est contrôlé par différents sous-types de récepteurs cholinergiques situés sur les neurones GABAergiques ou glutamatergiques des différentes couches corticales. La présente thèse montre qu’une stimulation électrique dans le télencéphale basal a un effet similaire à l’infusion d’agoniste cholinergique et qu’un couplage de stimulations visuelle et cholinergique induit la plasticité corticale. Ce jumelage répété de stimulations visuelle/cholinergique augmente la capacité de discrimination visuelle et améliore la perception. Cette amélioration est corrélée à une amplification de l’activité neuronale démontrée par immunocytochimie du c-Fos. L’immunocytochimie montre aussi une différence entre l’activité des neurones glutamatergiques et GABAergiques dans les différentes couches corticales. L’injection pharmacologique pendant la stimulation visuelle/cholinergique suggère que les récepteurs nicotiniques, muscariniques M1 peuvent amplifier la réponse excitatrice tandis que les récepteurs M2 contrôlent l’activation GABAergique. Ainsi, le système cholinergique activé au cours du processus visuel induit des mécanismes de plasticité corticale et peut ainsi améliorer la capacité perceptive. De meilleures connaissances sur ces actions ouvrent la possibilité d’accélérer la restauration des fonctions visuelles lors d’un déficit ou d’amplifier la fonction cognitive.<br>Sensory cortex is an essential area where sensory perception occurs. Especially visual cortex processes visual information transmitted from the retina through the thalamus. By different neuronal activation the information is segregated and sent to diverse visual area for interpretation. Neurons are the basic unit that transform sensory information into electrophysiological signal, transfer to the cortex and integrate it. Connection between neurons can be modulated depending on the persistent presynaptic activity inducing either a long-term increase or decrease of the post-synaptic activity. Modification in synaptic strength can affect large area and induce reorganization of cortical map (i.e. cortical plasticity) which changes the representation of the visual stimulus and its weight in visual processing. Cortical plasticity can occur during juvenile while forming developmental connection or in adult while acquiring novel information (i.e. learning). The neurotransmitter ACh is involved in many cognitive functions, such as learning or attention and it was demonstrated that lesioning or blocking cholinergic system diminishes cortical plasticity. It was shown that nicotinic, M1 subtype and M2 subtype muscarinic receptors are the major cholinergic receptors abundant in the cortex and implicated during cortical plasticity induction. In a first part, I analyzed visual evoked potentials (VEPs) in V1 of rats during a 4-8h period after coupling visual stimulation to an intracortical injection of ACh agonist carbachol or stimulation of basal forebrain. To clarify the action of ACh on VEP activity in V1, we individually injected muscarinic, nicotinic, α7, and NMDA receptor antagonists just before carbachol infusion. Stimulation of the cholinergic system paired with visual stimulation significantly increased VEP amplitude for long-term. Pre-inhibition of muscarinic, nicotinic and NMDA receptor completely abolished this long-term enhancement, while α7 inhibition induced an instant increase of VEP amplitude. This suggests a role of ACh in facilitating visual stimuli responsiveness which involves nicotinic and muscarinic receptors with an interaction of NMDA transmission in the visual cortex. These mechanisms were similar to long-term potentiation, a neurobiological mechanism of learning. In a second step, I evaluate whether cholinergic modulation of visual neurons results in cortical activity and visual perception changes. Awake adult rats were exposed repetitively for two weeks to an orientation-specific grating with coupling visual stimulation to an electrical stimulation of the basal forebrain. The visual acuity, as measured using a visual water maze before and after coupling visual/cholinergic stimulation was increased. The increase in visual acuity was not observed when visual or basal forebrain stimulation was performed separately nor when cholinergic fibers were selectively lesioned prior to the visual stimulation. There was a long-lasting increase in cortical reactivity of the primary visual cortex shown by c-Fos immunoreactivity of both pyramidal and GABAergic interneuron. These findings demonstrate that when coupled with visual training, the cholinergic system improves visual performance for the trained orientation probably through enhancement of attentional processes and cortical plasticity in V1 related to the ratio of excitatory/inhibitory inputs. Finally, I also investigated the different pharmacological mechanisms involved in the visual enhancement. Pre- and post-pairing visual/cholinergic stimulation VEP were compared with selective administered agonist/antagonist during the pairing. Awaken adult rats were exposed during 10 minutes per day for 1 week to an orientation specific grating with an electrical stimulation of the basal forebrain. Intracortical injection of different pharmacological agents during pairing demonstrated that nicotinic and M1 muscarinic receptors are used to amplify cortical response while M2 muscarinic receptor suppresses GABAergic neurons to disinhibit excitatory neurons. Infusion of GABAergic antagonist supported that inhibitory system is crucial to induce cortical plasticity. These findings demonstrate that visual training coupled with the cholinergic stimulation enhances the cortical plasticity mediated by nicotinic, M1 and M2 muscarinic receptors, which the latter induces a disinhibition by suppressing GABAergic neuron. The cholinergic system is a potent neuromodulatory system. Boosting this system during perceptual learning robustly enhances the sensory perception. Especially, pairing a cholinergic activation with a visual stimulation increases the signal-to-noise ratio, cue detection ability in the primary visual cortex. This cholinergic enhancement increases the strength of thalamocortical afferent to facilitate the treatment of a novel stimulus while decreasing the cortico-cortical signaling to minimize recurrent or top-down modulation. This is mediated by different cholinergic receptor subtypes located in both glutamatergic and GABAergic neurons of the different cortical layers. The mechanisms of cholinergic enhancement are closely linked to attentional processes, long-term potentiation and modulation of the excitatory/inhibitory balance. The present thesis shows that electrical stimulation of the basal forebrain has similar effect with cholinergic agonist release and pairing visual/cholinergic stimulation induces cortical plasticity. Repetitive pairing of visual/cholinergic increases visual discrimination capacity and enhances perceptual ability. This enhancement is followed by an augmentation of neuronal activity demonstrated by c-Fos immunohistochemistry. Immunoreactivity also shows difference in glutamatergic and GABAergic neurons activities between layers. Pharmacological injection during visual/cholinergic pairing suggests that nicotinic and M1 muscarinic receptor can amplify excitatory response while M2 receptor controls GABAergic activation. Altogether cholinergic system activated during visual process induces cortical plasticity and can enhance perceptual ability. Further understanding of this training has the potential to accelerate visual recovery or boost cognitive function.

Summaries in Afrikaans and English<br>Text in Afrikaans<br>Die waarde van visueel-perseptuele skoling of terapie vir visueel-perseptueel gestremde leerlinge as 'n subgroep van leergestremdheid, is reeds vir dekades 'n omstrede aangeleentheid. Hierdie omstredenheid is ondersoek aan die hand van sewe internasionaal erkende psigometriese toetse. Die interne konsekwentheidskoeffisiente van hierdie toetse het vir die huidige studie van 0,62 tot 0,95 gestrek. 'n Faktorontleding van die toetsinterkorrelasies het 'n gemeenskaplike faktor blootgele. Ses toetse was primer visueel-perseptueel, en Goodenough <1926> se skaal is vir die bepaling van intelligensie gebruik. Bykomend hiertoe, is leerlinge se prestasies in hul eerste taal, wiskunde en skrif gebruik om die effek van terapie te bepaal. Proefpersone is as visueel-perseptueel gestremd gediagnoseer deur 'n opvoedkundige sielkundige en 'n visuele skolingsentrum in Pretoria, waar eksper imentele leerlinge terapie ontvang het. Hierdie diagnoses is deur die Test for Visual Analysis Skills wat beduidend tussen normale en visueelperseptueel gestremdes onderskei, bevestig. Die toets se geldigheid vir Suid-Afrikaanse omstandighede is in 'n voorstudie bepaal. Honderd en ses, ses- tot negejarige proefpersone (82 seuns en 24 dogters>, van normale intelligensie, gesigskerpte en gehoor, is betrek. Drie en vyftig het die eksperimentele groep gevorm wat onderverdeel is in 32 wat terapie voltooi het, en 21 wat nie het nie. Hierdie leerlinge is individueel afgepaar met kontroleleerlinge van dieselfde geslag, ouderdom, huistaal, sosio-ekonomiese status en skoolstanderd. Eksperimentele leerlinge het visuele terapie in n breer groepsverband vir een uur per week ontvang. Terapieperiodes het van 4 tot 15 maande gewissel. Die eksperimentele ontwerp was 'n voortoets-natoets-tweegroepontwerp. t-Toetse vir afhanklike (afgepaarde) groepe is uitgevoer op die verskille tussen voor- en natoetstellings, asook tussen die eksperimentele en kontrolegroepe. Geeneen van die primer visueel-oerseptuele meettegnieke het beduidende resultate opgelewer nie. Dit is aanduidend van die ondoeltreffendheid van visueel-perseptuele terapie om die tekorte waarop dit gemik is, reg te stel. Die waarde van visueel-perseptueie terapie is inteendeel beperk tot 'n oorhoofse verbetering in konseptualisering en intellektuele ryping by die groep wat terapie voltooi het. Skrif was die enigste vak wat by dieselfde groep beduidend verbeter het. Hierdie resultaat is egter twyfelagtig vanwee beoordelingstekorte.<br>The value of visual perceptual training or therapy, to visually perceptually impaired pupils as a subgroup of the learning disabled, has been a controversy far decades. This controversy was investigated by means of seven internationally recognised psychometric tests. The internal consistency coefficients of these tests for the present study ranged from 0,62 to 0,95. A factor analysis of test intercorrelations revealed a common factor. Six tests were primarily visual perceptual, whilst the Goodenough (1926) scale determined intelligence. Additionally, pupils' performance in their first language, mathematics and writing, was used to assess the therapeutic effect. Subjects were diagnosed as visually perceptually impaired by an educational psychologist and a visual training centre in Pretoria where experimental pupils received therapy. These diagnoses were confirmed by the Test for Visual Analysis Skills, which significantly differentiates between the normal and visually perceptually impaired. This test's validity for South African circumstances was determined in a prestudy. One hundred and six, six to nine year old subjects <82 boys and 24 girls>, of normal intelligence, visual acuity and hearing, were involved. Fifty three formed the experimental group which was subdivided in 32 who completed therapy, and 21 who did not. These pupils were individualiy matched with controls of similar sex, age, home language, socio economic status and school standard. Experimental pupils received visual therapy within a broader group context for one hour per week. Therapy periods fluctuated between 4 and 15 months. The experimental design was a pretest-posttest two group design. t-Tests for dependant <matched) groups were conducted on the differences between pre and oosttest scores, as well as between the experimental and control groups. None of the primarily visual perceptual tests revealed significant results. This signifies the inefficiency of visual perceptual therapy to rectify the deficits at which it is directed. The value of visual perceptual therapy is, on the contrary, restricted to an overall improvement in conceptualization and intellectual maturation within the group which completed therapy. Writing was the only subject which improved significantly within the same group. However, this result is dubious, due to evaluation deficits.<br>Psychology<br>D.Litt. et Phil. (Psychology)

This thesis is concerned with describing and experimentally investigating the nature of perceptual learning. Ecological psychology defines perceptual learning as a process of educating attention to structural properties of stimuli (i.e., invariants) that specify meaning (i.e., affordances) to the perceiver. Although such definition comprehensively describes the questions of what humans learn to perceive, it does not address the question of how learning occurs. It is proposed in this thesis that the principles of classical and operant conditioning can be used to strengthen and expand the ecological account of perceptual learning. The perceptual learning of affordances is described in terms of learning that a stimulus is associated with another stimulus (classical conditioning), and in terms of learning that interacting with a stimulus is associated with certain consequences (operant conditioning). Empirical work in this thesis investigated the effect of conditioning on pitch and speech perception. Experiments 1, 2, and 3 were designed to modify pitch perception in Shepard tones via tone-colour associative training. During training, Shepard tones were paired with coloured circles in a way that the colour of the circles could be predicted by either the F0 (pitch) or by an F0-irrelevant auditory invariant. Participants were required to identify the colour of the circles that was associated with the tones and they received corrective feedback. Hypotheses were based on the assumption that F0-relevant/F0- irrelevant conditioning would increase/decrease the accuracy of pitch perception in Shepard tones. Experiment 1 investigated the difference between F0-relevant and F0- irrelevant conditioning in a between-subjects design, and found that pitch perception in the two conditions did not differ. Experiments 2 and 3 investigated the effect of F0- relevant and F0-irrelevant conditioning (respectively) on pitch perception using a within subjects (pre-test vs. post-test) design. It was found that the accuracy of pitch perception increased after F0-relevant conditioning, and was unaffected by F0-irrelevant conditioning. The differential trends observed in Experiments 2 and 3 suggest that conditioning played some role in influencing pitch perception. However, the question whether the observed trends were due to the facilitatory effect of F0-relevant conditioning or the inhibitory effect of F0-irrelevant conditioning warrants future investigation. Experiments 4, 5, and 6 were designed to modify the perception of McGurk syllables (i.e., auditory /b/ paired with visual /g/) via consonant-pitch associative training. During training, participants were repeatedly presented with /b/, /d/, and /g/ consonants in falling, flat, and rising pitch contours, respectively. Pitch contour was paired with either the auditory signal (Experiments 4 and 5) or the visual signal (Experiment 6) of the consonant. Participants were required to identify the stop consonants and they received corrective feedback. The perception of McGurk stimuli was tested before and after training by asking participants to identify the stop consonant in each stimulus as /b/ or /d/ or /g/. It was hypothesized that conditioning would increase (1) /b/ responses more in the falling than in the flat/ rising contour conditions, (2) /d/ responses more in the flat than in the falling/ rising contour conditions, and (3) /g/ responses more in the rising than in the falling/flat contour conditions. Support for the hypotheses was obtained in Experiments 5 and 6, but only in one response category (i.e., /b/ and /g/ response categories, respectively). It is suggested that the subtlety of the observed conditioning effect could be enhanced by increasing the salience of pitch contour and by reducing the clarity of auditory/visual invariants that specify consonants.<br>Doctor of Philosophy (PhD)

Ten experiments examined the interactions between vision and audition in stimulusdriven spatial attention orienting and inhibition of return (IOR). IOR is the demonstration that subjects are slower to respond to stimuli that are presented at a previously stimulated location. In each experiment, subjects made go/no-go responses to peripheral targets but not to central targets. On every trial, a target was preceded by a sensory event, called a "cue," either in the same modality (intramodal conditions) or in a different modality (crossmodal conditions). The cue did not predict the location of the target stimulus in any experiment. In some experiments, the cue and target modalities were fixed and different. Under these conditions, response times to a visual target were shorter when it appeared at the same location as an auditory cue than when it appeared on the opposite side of fixation, particularly at short (100 ms) cue-target stimulus onset asynchronies (Experiments 1A and IB). Similarly, response times to an auditory target were shorter when it appeared at the same location as a visual cue than when it appeared at a location on the opposite side of fixation (Experiments 2A and 2B). These crossmodal effects indicate that stimulus-driven spatial attention orienting might arise from a single supramodal brain mechanism. IOR was not observed in either crossmodal experiment indicating that it might arise from modality specific mechanisms. However, for many subjects, IOR did occur between auditory cues and visual targets (Experiments 3A and 3B) and between visual cues and auditory targets (Experiment 4A and 4B) when the target could appear in the same modality as the cue on half of the trials. Finally, the crossmodal effects of stimulus-driven spatial attention orienting on auditory and visual event-related brain potentials (ERPs) were examined in the final two experiments. Auditory cues modulated the ERPs to visual targets and visual cues modulated the ERPs to auditory targets, demonstrating that the mechanisms for spatial attention orienting cannot be completely modality specific. However, these crossmodal ERP effects were very different from each other indicating that the mechanisms for spatial attention orienting cannot be completely shared.

Le système cholinergique joue un rôle important dans de nombreuses fonctions cognitives telles que l'attention et l'apprentissage perceptuel. La stimulation pharmacologique du système cholinergique par le donépézil, un inhibiteur de l’acétylcholinestérase, est un moyen efficace pour améliorer les fonctions cognitives et le traitement cortical via les récepteurs muscariniques et nicotiniques. En effet, le donépézil permet l'accumulation d'acétylcholine dans la fente synaptique. Toutefois, l’effet de la stimulation pharmacologique du système cholinergique sur le traitement visuel complexe et l’apprentissage perceptuel n’est pas encore bien défini. L'objectif de cette thèse est d'étudier, d'une part, l'effet de la combinaison d’un entrainement visuel répétitif avec une stimulation cholinergique sur les capacités visuelles chez le rat et l’humain et, d'autre part, l’effet de la stimulation pharmacologique du système cholinergique sur la restauration des capacités visuelles dans un modèle de déficit visuel chez les rats. Nos résultats ont montré qu’un entrainement visuel/cholinergique entraînait : 1) une potentialisation à long terme de la réponse visuelle corticale chez le rat, 2) une récupération plus rapide des capacités visuelles chez la rat suite un écrasement du nerf optique 3) une amélioration de la performance dans une tâche perceptivo-cognitive de haut niveau plus rapide et conservée dans le temps chez les jeunes sujets sains. Le patron d’électroencéphalographie chez le sujet humain pratiquant une tâche d’attention visuelle n’est cependant pas modifié par l’administration d’une dose unique de donépézil. Ensembles, ces résultats soulignent le bénéfice considérable de la combinaison d’une stimulation du système cholinergique lors de l’entrainement visuel répétitif afin d'obtenir des améliorations de la perception visuelle. Cela présente une avenue très intéressante pour la réhabilitation chez les humains.<br>The cholinergic system plays an important role in many cognitive functions such as attention and perceptual learning. Pharmacological stimulation of the cholinergic system via donepezil, an acetylcholinesterase inhibitor, is an efficient tool for enhancing cognitive functions and cortical processing via muscarinic and nicotinic receptors. In fact, donepezil allows the build-up of acetylcholine in the synaptic cleft. However, whether pharmacological manipulation of the cholinergic system has an effect on complex visual processing and perceptual learning remains unclear. The goal of this thesis is to investigate on the one hand the effect of combining repetitive visual training with cholinergic enhancement on visual capacities in rats and humans and on the other hand the effect of the pharmacological stimulation of the cholinergic system on visual restoration in a model of visual deficit in rats. Our results showed that cholinergic potentiation induces 1) a long-term potentiation of visual cortical response following repetitive visual stimulation, 2) a faster recovery of brightness discrimination in rats with an optic nerve crush, 3) a faster progression of and a sustained performance in a highly demanding perceptual-cognitive task for healthy young humans. However, the EEG pattern for subjects performing a visual attention task is not modified by a single administration of donepezil. Together these results underline the substantial benefice of combining cholinergic enhancement with visual training in order to obtain visual perception improvements, which presents an interesting avenue for visual rehabilitation paradigm in humans.