Дисертації з теми "Visual cortex (V1)"
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Thulin, Nilsson Linnea. "The Role of Primary Visual Cortex in Visual Awareness." Thesis, Högskolan i Skövde, Institutionen för biovetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-11623.
Повний текст джерелаStevens, Jean-Luc Richard. "Spatiotemporal properties of evoked neural response in the primary visual cortex." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31330.
Повний текст джерелаFournier, Julien. "Adaptation of the simple or complex nature of V1 receptive fields to visual statistics." Paris 6, 2009. http://www.theses.fr/2009PA066426.
Повний текст джерелаPalmer, Chris M. "Topographic and laminar models for the development and organisation of spatial frequency and orientation in V1." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/4114.
Повний текст джерелаYu, Hsin-Hao. "Integration of visual information and the organization of receptive fields in V1 of the California ground squirrel." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3283974.
Повний текст джерелаTitle from first page of PDF file (viewed January 8, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 112-124).
Kogan, Cary. "The expression of neurofilament protein and mRNA levels in the lateral geniculate nucleus and area V1 of the developing and adult vervet monkey (Ceorcopithicus aethiops) /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0028/MQ50807.pdf.
Повний текст джерелаFONTENELE, NETO Antonio Jorge. "Implementação de um protocolo experimental para estudo de propriedades de resposta visual de neurônios do córtex visual primário (V1) em ratos utilizando matrizes de eletrodos." Universidade Federal de Pernambuco, 2015. https://repositorio.ufpe.br/handle/123456789/17698.
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O córtex visual primário (V1) é a região do córtex cerebral responsável pela primeira etapa de processamento da informação visual capturada pela retina. Por ser uma das áreas corticais melhor compreendidas, V1 constitui um dos principais paradigmas de compreensão do processamento sensorial. Desde os anos 70 há uma extensa literatura que estuda propriedades de resposta de neurônios de V1, principalmente com eletrodos individuais e utilizando-se como modelo animal gatos e macacos. Tem-se conhecimento de onde partem seus principais inputs e quais estímulos fazem os neurônios dispararem (grades senoidais com determinadas frequências espaciais e temporais). Mais recentemente, com o uso de matrizes de eletrodos, se tornou possível a investigação de propriedades coletivas da atividade e codificação neurais, que não eram possíveis de serem desvendadas com eletrodos individuais. Além disso, no estado da arte tecnológico atual, o uso do rato como modelo animal permite o registro da atividade neural com os animais em comportamento livre (sem anestesia ou contenção). No entanto, pouco se sabe sobre especificidades das propriedades de resposta dos neurônios do córtex visual do rato. Este trabalho teve por objetivo desenvolver um aparato e um protocolo experimental no Laboratório de Neurociência de Sistemas e Computacional adequado para estudo das propriedades de resposta de neurônios de V1 de ratos usando matrizes de eletrodos. Finalmente, apresentamos resultados experimentais onde caracterizamos respostas de neurônios de V1 a diferentes estímulos visuais (Funções de Gabor ou Grades) seja em ruído denso ou rarefeito, variando as propriedades de frequências temporal e espacial de estimulação, densidades de estímulos, velocidade, etc. Concluímos que implementamos com sucesso a técnica experimental, que abre inúmeras perspectivas futuras de pesquisas nesta linha no Departamento de Física da Universidade Federal de Pernambuco.
The primary visual cortex (V1) is the cerebral cortex region responsible for the first processing step of the visual information captured by the retina. Being one of the most studied and well described cortical sensory areas, V1 is one of the main paradigms for the study of sensory processing. Since the 70s, there is a vast literature that studies properties of V1’s neurons, specially using single electrodes and using cats and monkeys as animal models. The anatomical conectivity of the visual pathway is known, from the retina to the lateral geniculate nucleus to V1, as well as the main visual stimulations that make V1 neurons fire (sinusoidal gratings with certain spatial and temporal frequencies). More recently, using multielectrode arrays, it became possible to study coletive properties of the activity and neural codification, that could not be unveiled with single electrodes. Furthermore with, the current state of the art in multielectrode recordings it is possible to record the neural activity in frelly behaving rats (without anesthesia or restraint). This represents an advantage in using the rat as animal model. However, little is known about specificities of the V1 neurons response properties in the rat. The aim of this work is to develop, in the Laboratório de Neurociência de Sistemas e Computacional, an apparatus and an experimental protocol suitable for the study of visual response properties of V1’s neurons in rats, using multielectrode array recordings. Finally, we present experimental results that characterize the response of V1’s neurons with different visual stimuli (Gabor or Grating Functions), either in dense os sparse noise modes, varying the spatial and temporal stimulation frequencies, stimulus density, speed, etc. We conclude that the experimental technique was implemented successfully. These results open important perspectives of future research on this field for the Departamento de Física at the Universidade Federal de Pernambuco.
Bohi, Amine. "Descripteurs de Fourier inspirés de la structure du cortex visuel primaire humain : Application à la reconnaissance de navires dans le cadre de la surveillance maritime." Thesis, Toulon, 2017. http://www.theses.fr/2017TOUL0002/document.
Повний текст джерелаIn this thesis, we develop a supervised object recognition method using new global image descriptors inspired by the model of the human primary visual cortex V1. Mathematically speaking, the latter is modeled as the semi-discrete roto-translation group SE (2,N)=R² x ZN semi-direct product between R² and ZN. Therefore, our technique is based on generalized and rotational Fourier descriptors defined in SE (2,N) , and which are invariant to natural geometric transformations (translations, and rotations). Furthermore, we show that such Fourier descriptors are weakly complete, in the sense that they allow to distinguish over an open and dense set of compactly supported functions in L² (SE(2,N)) , hence between real-world images. These descriptors are later used in order to feed a Support Vector Machine (SVM) classifier for object recognition purposes. We have conducted a series of experiments aiming both at evaluating and comparing the performances of our method against existing both local - and global - descriptor based state of the art techniques, using the RL, the CVL, and the ORL face databases, and the COIL-100 image database (containing various types of objects). The obtained results have demonstrated that our approach was able to compete with many existing state of the art object recognition techniques, and to outperform many others. These results have also shown that our method is robust to noise. Finally, we have applied the proposed method on vessels recognition in the framework of maritime surveillance
Maama, Mohamed. "Dynamiques de réseaux complexes, modélisation et simulations : application au cortex visuel Emergent Properties in a V1 Network of Hodgkin-Huxley Neurons." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMLH07.
Повний текст джерелаThe aim of this work is to analyze theoretically and numerically the dynamics of a network of excitatory and inhibitory neurons of ordinary differential equations (ODE) of Hodgkin-Huxley type (HH) inspired by the primary visual cortex V1. The model emphasizes an approach combining a driven stochastic drive for each neuron and recurrent inputs resulting from the network activity. After a review of the dynamics of a single HH equation, for both deterministic and stochastic driven case, we proceed to the analysis of the network. Our numerical analysis highlights emergent properties such as partial synchronization and synchronization, waves of excitability, and oscillations in the gamma-band frequency
Cavalcante, André Borges. "Campos receptivos similares às wavelets de Haar são gerados a partir da codificação eficiente de imagens urbanas;V1." Universidade Federal do Maranhão, 2008. http://tedebc.ufma.br:8080/jspui/handle/tede/314.
Повний текст джерелаEfficient coding of natural images yields filters similar to the Gabor-like receptive fields of simple cells of primary visual cortex. However, natural and man-made images have different statistical proprieties. Here we show that a simple theoretical analysis of power spectra in a sparse model suggests that natural and man-made images would need specific filters for each group. Indeed, when applying sparse coding to man-made scenes, we found both Gabor and Haar wavelet-like filters. Furthermore, we found that man-made images when projected on those filters yielded smaller mean squared error than when projected on Gabor-like filters only. Thus, as natural and man-made images require different filters to be efficiently represented, these results suggest that besides Gabor, the primary visual cortex should also have cells with Haar-like receptive fields.
A codificação eficiente de imagens naturais gera filtros similares às wavelets de Gabor que relembram os campos receptivos de células simples do córtex visual primário. No entanto, imagens naturais e urbanas tem características estatísticas diferentes. Será mostrado que uma simples análise do espectro de potência em um modelo eficiente sugere que imagens naturais e urbanas requerem filtros específicos para cada grupo. De fato, aplicando codificação eficiente à imagens urbanas, encontramos filtros similares às wavelets de Gabor e de Haar. Além disso, observou-se que imagens urbanas quando projetadas nesses filtros geraram um menor erro médio quadrático do que quando projetadas somente em filtros de similares a Gabor. Desta forma, como imagens naturais e urbanas requerem filtros diferentes para serem representadas de forma eficiente, estes resultados sugerem que além de Gabor, o córtex visual primário também deve possuir células com campos receptivos similares às wavelets de Haar.
Reynaud, Alexandre. "Rôle fonctionnel des interactions latérales dans l'intégration du mouvement visuel : étude en imagerie optique au niveau du cortex visuel primaire du singe éveillé." Thesis, Aix-Marseille 2, 2010. http://www.theses.fr/2010AIX22129/document.
Повний текст джерелаOur goal is to study motion integration at population level in V1 in the awake behaving onkey. We compare V1population recorded with optical imaging of voltage sensitive dyes with ocular following response.We have shown that contrast response function in V1 is controlled by a dynamic normalization pool. Then we identified two distinct mechanisms involved in contextual modulations: a fast transient one originating from MT and a show and sustained one, originating from V1. Finally, we have observed that cortical activity dynamics in presponse to apparent motion can induce a suppression wave at acortical surface
Hurdal, Monica Kimberly. "Mathematical and computer modelling of the human brain with reference to cortical magnification and dipole source localisation in the visual cortx." Thesis, Queensland University of Technology, 1998.
Знайти повний текст джерелаLevy, Manuel. "From boxes to codes : adaptation of V1 nonlinearities to the temporal encoding of spatial information during simuled eye movements." Paris 6, 2007. http://www.theses.fr/2007PA066238.
Повний текст джерелаThis thesis focuses on the processing and temporal encoding of natural stimuli by simple cells of the primary visual cortex (V1). Neuronal responses were recorded by intra- and extra-cellular electrodes in the anaesthetized and paralysed Cat, and analysed with tools derived from system identification and information theory. We show that the recruitment of contrast gain controls and centre surround interactions, in particular by stimuli having natural eye movement dynamics, increases the reproducibility of the high temporal frequencies components of the membrane potential, as well as the temporal precision and sparseness of the spike output. The addition of a complex-like, feedforward, delayed inhibition to the classical LN model accounted largely for our results. Finally we propose that V1 nonlinearities are adapted to the coarse-to-fine processing and temporal encoding of spatial information during the course of an ocular fixation
Montardy, Quentin. "Lier l'activité de population de neurones du cortex visuel primaire avec le comportement oculomoteur : des saccades de fixation à V1, et de V1 à la réponse de suivi oculaire." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM5069.
Повний текст джерелаWe analyzed population activity in V1 to understand (i) the consequence of eye movements on integration of visual information, and (ii) the influence of the processing performed at the level of V1 on the generation of eye movements.1. We recorded fixational saccades, relating, trial-by-trial, these eye movements with the representation of the position of a local stimulus in V1. After a fixational saccade, activity moves consistently in V1. However, the time-course of responses display a biphasic dynamic. This results in a global increase of the extent of cortical activity representing the local stimulus. We propose that the behavior of populations of neurons studied is explained by the contribution of two main phenomena: (i) an early suppressive response that could be attributed to the corollary discharge and (ii) the lateral connections generating lateral interactions between pre and post-saccadic lci of activity.2. We recorded the ocular following response, determining whether the response of V1 influences the oculomotor response. We studied the contrast response function of the population V1 activity and the OFR. The dynamics of CRF for a local stimulus are similar and shifted in time. We found no correlations between the single trial latencies between V1 and the OFR. At the chosen scale, surround suppression was found to be distance-dependent only in V1. The dynamics of the surround suppression shows two phases: an early suppression present over a wide cortical area, and a later peripheral spread. We propose that the early surround suppression originates from feedback from MT and MST, while the later is explained by the horizontal connections
Seriès, Peggy. "Étude théorique des modulations centre/pourtour des propriétés des champs récepteurs du cortex visuel primaire : circuits, dynamiques et corrélats perceptifs." Paris 6, 2002. http://www.theses.fr/2002PA066333.
Повний текст джерелаThe response of primary visual cortex (V1) neurons to a stimulus presented within the receptive field can be modulated by the stimulation of the surround of the receptive field. The origin and functional role of these " center/surround " modulations is yet poorly understood. Using computational methods in interaction with electrophysiological and psychophysical approaches, we try to answer 2 questions : What are the circuits responsible for the diversity of these phenomena ? We provide theoretical tools to evaluate current models, reconcile them in a common formalism and understand how the spatial characteristics of center/surround modulations can result from the known properties of V1 ; What are the consequences of the dynamics of these effects on cortical responses and visual perception ? Our results suggest that V1 responses and the perception of visual objects should depend not only on the spatial context, but also on the temporal context in which these objects are embedded. We discuss the functional implications of this mechanism for the analysis of static and moving objects
Khaytin, Ilya. "Analysis of cortical and thalamic contributors to functional organization of primate primary visual cortex (V1)." Diss., 2008. http://etd.library.vanderbilt.edu/ETD-db/available/etd-03272008-134041/.
Повний текст джерелаLai, Jimmy. "Pulvinar modulates contrast response function of neurons in the primary visual cortex." Thèse, 2017. http://hdl.handle.net/1866/19712.
Повний текст джерелаLe pulvinar, localisé dans le thalamus postérieur, établit des connections réciproques avec la vaste majorité des aires visuelles corticales et il est ainsi dans une position stratégique afin d’influencer les processus de décodage de celles-ci. Les projections du pulvinar au cortex visuel primaire (V1) sont considérées comme étant des projections modulatrices, qui modifieraient les réponses neuronales sans toutefois changer les propriétés de base des champs récepteurs. Dans la présente étude, nous avons étudié les réponses des neurones de V1 suite à l’inactivation réversible du complexe noyau latéral postérieur (LP)-pulvinar chez le chat. Des courbes de réponse au contraste ont été générées par la présentation de réseaux ayant plusieurs niveaux de contraste pendant l’inactivation du LP-pulvinar. Aucun changement n’a été observé concernant l’orientation préférée ou la sélectivité à la direction des neurones de V1 lors de l’inactivation du pulvinar. Néanmoins, pour la majorité des cellules testées, l’amplitude de la réponse aux stimuli optimaux a été réduite. La fonction de Naka-Rushton a été appliquée aux courbes de réponse au contraste et l’analyse des effets de l’inactivation du pulvinar a montré une panoplie d’effets modulateurs : 35% des cellules ont présenté une réduction de leur réponse maximale, 11% ont eu une augmentation de leur C50, 6% ont montré une modulation de la pente et 22% des neurones ont présenté des changements dans plus d’un paramètre. Nos résultats suggèrent que le pulvinar module l’activité des neurones de V1 d’une façon dépendante du contraste et qu’il contrôle le gain des réponses des neurones des aires primaires du cortex visuel.
TSUI, CLAUDIA KA YAN. "Visual Discrimination Performance in Rats: Role of Acetylcholine and Synaptic Correlates in the Primary Visual Cortex and Hippocampus." Thesis, 2011. http://hdl.handle.net/1974/6726.
Повний текст джерелаThesis (Master, Psychology) -- Queen's University, 2011-09-16 13:50:24.045
(8086100), Samuel T. Kissinger. "Visual experience-dependent oscillations in the mouse visual system." Thesis, 2019.
Знайти повний текст джерелаThe visual system is capable of interpreting immense sensory complexity, allowing us to quickly identify behaviorally relevant stimuli in the environment. It performs this task with a hierarchical organization that works to detect, relay, and integrate visual stimulus features into an interpretable form. To understand the complexities of this system, visual neuroscientists have benefited from the many advantages of using mice as visual models. Despite their poor visual acuity, these animals possess surprisingly complex visual systems, and have been instrumental in understanding how visual features are processed in the primary visual cortex (V1). However, a growing body of literature has shown that primary sensory areas like V1 are capable of more than basic feature detection, but can express neural activity patterns related to learning, memory, categorization, and prediction.
Visual experience fundamentally changes the encoding and perception of visual stimuli at many scales, and allows us to become familiar with environmental cues. However, the neural processes that govern visual familiarity are poorly understood. By exposing awake mice to repetitively presented visual stimuli over several days, we observed the emergence of low frequency oscillations in the primary visual cortex (V1). The oscillations emerged in population level responses known as visually evoked potentials (VEPs), as well as single-unit responses, and were not observed before the perceptual experience had occurred. They were also not evoked by novel visual stimuli, suggesting that they represent a new form of visual familiarity in the form of low frequency oscillations. The oscillations also required the muscarinic acetylcholine receptors (mAChRs) for their induction and expression, highlighting the importance of the cholinergic system in this learning and memory-based phenomenon. Ongoing visually evoked oscillations were also shown to increase the VEP amplitude of incoming visual stimuli if the stimuli were presented at the high excitability phase of the oscillations, demonstrating how neural activity with unique temporal dynamics can be used to influence visual processing.
Given the necessity of perceptual experience for the strong expression of these oscillations and their dependence on the cholinergic system, it was clear we had discovered a phenomenon grounded in visual learning or memory. To further validate this, we characterized this response in a mouse model of Fragile X syndrome (FX), the most common inherited form of autism and a condition with known visual perceptual learning deficits. Using a multifaceted experimental approach, a number of neurophysiological differences were found in the oscillations displayed in FX mice. Extracellular recordings revealed shorter durations and lower power oscillatory activity in FX mice. Furthermore, we found that the frequency of peak oscillatory activity was significantly decreased in FX mice, demonstrating a unique temporal neural impairment not previously reported in FX. In collaboration with Dr. Christopher J. Quinn at Purdue, we performed functional connectivity analysis on the extracellularly recorded spikes from WT and FX mice. This analysis revealed significant impairments in functional connections from multiple layers in FX mice after the perceptual experience; some of which were validated by another graduate student (Qiuyu Wu) using Channelrhodopsin-2 assisted circuit mapping (CRACM). Together, these results shed new light on how visual stimulus familiarity is differentially encoded in FX via persistent oscillations, and allowed us to identify impairments in cross layer connectivity that may underlie these differences.
Finally, we asked whether these oscillations are observable in other brain areas or are intrinsic to V1. Furthermore, we sought to determine if the oscillating unit populations in V1 possess uniform firing dynamics, or contribute differentially to the population level response. By performing paired recordings, we did not find prominent oscillatory activity in two visual thalamic nuclei (dLGN and LP) or a nonvisual area (RSC) connected to V1, suggesting the oscillations may not propagate with similar dynamics via cortico-thalamic connections or retrosplenial connections, but may either be uniquely distributed across the visual hierarchy or predominantly restricted to V1. Using K-means clustering on a large population of oscillating units in V1, we found unique temporal profiles of visually evoked responses, demonstrating distinct contributions of different unit sub-populations to the oscillation response dynamics.
Schottdorf, Manuel. "The reconstitution of visual cortical feature selectivity in vitro." Thesis, 2017. http://hdl.handle.net/11858/00-1735-0000-002E-E348-B.
Повний текст джерелаLiedtke, Joscha. "Genetic determination and layout rules of visual cortical architecture." Doctoral thesis, 2017. http://hdl.handle.net/11858/00-1735-0000-0023-3EE8-5.
Повний текст джерелаJeans, Rhiannon. "Form perception and neural feedback: insights from V1 and V2." Thesis, 2014. http://hdl.handle.net/1885/12731.
Повний текст джерелаCattan, Sarah. "Plasticité de la réponse aux orientations dans le cortex visuel primaire du chat par la méthode d'imagerie optique intrinsèque." Thèse, 2016. http://hdl.handle.net/1866/18508.
Повний текст джерелаIn the cat primary visual cortex (areas 17 and 18), neurons responding to orientations in the environment (such as the outline of objects) are organized in columns perpendicular to the cortical surface. It was previously shown that a drastic change in orientations in the environment changes the response of neurons. For example, a neuron responding to a horizontal orientation will respond, after learning a new environment, to an oblique orientation. In this thesis, we seek to follow the changes of properties of large populations of neurons due to this type of learning. To this end, we used the intrinsic signals optical imaging technique, which measures the activity of a cortical surface using the BOLD (blood-oxygen-level dependent) signal. This thesis follows three axes: the effect of learning at the local level, the effect of learning at the visual area scale, and the modeling of learning. In the first part, we compared the changes in orientation of neurons according to the local gradient of orientation. This gradient is strong when two neighboring neurons have very different orientations, and weak when their orientations are similar. The obtained relation between the gradient and the magnitude of change in orientation shows that when neurons are increasingly surrounded by neurons with different orientations, they change their response to orientation to a greater extent. This suggests that local connections have a decisive influence on the extent of learning. In the second part, we followed the change in the orientation of neurons in the areas 17 and 18, before and after learning. The results are not significantly different between area 17 and area 18. However, it is noteworthy that orientation changes in area 18 are more variable in amplitude than in area 17. This may be because area 18 receives more diverse inputs than area 17, including a direct input from dLGN (dorsal Lateral Geniculate Nucleus) Y cells. In the third part, we modeled the experimentally observed learning with neural networks using a Hebbian learning rule (networks are self-organizing maps). We have shown that feedback from higher areas to the primary visual cortex was desirable for the neurons orientation selectivity conservation. Overall, this thesis shows the importance of local connections in neuronal plasticity. In particular, they guarantee a homeostatic learning, i.e. maintaining the representativeness of orientations in the cortex. In a complementary manner, it also shows the importance of the superior areas in the conservation of learned orientations.
Keil, Wolfgang. "Optimization principles and constraints shaping visual cortical architecture." Doctoral thesis, 2012. http://hdl.handle.net/11858/00-1735-0000-000D-F0B0-0.
Повний текст джерелаBouchard, Marilyn. "Étude de la plasticité à court terme pour la fréquence spatiale dans le cortex visuel primaire du chat adulte." Thèse, 2006. http://hdl.handle.net/1866/17072.
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