Dissertations / Theses on the topic 'Cortex Visuel Primaire (CVP)'
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Remy, Irving. "Les fonctions visuelles rétiniennes et corticales dans les troubles du spectre de la schizophrénie et les situations à risque de psychose." Electronic Thesis or Diss., Strasbourg, 2024. http://www.theses.fr/2024STRAJ030.
Full textPsychotic disorders are characterized by severe functional consequences, with emerging evidence of impairment in low-level visual functions. Most notably, the anatomical and functional link between the retina and the visual cortex led to hypotheses concerning the association between alterations in both visual stages. We investigated retinal and cortical visual electrophysiological measurements in schizophrenia spectrum disorders and situations at risk of psychosis, of which regular cannabis use and early phases of psychosis are an integral part. The results highlighted alterations in most retinal cells and deficits in the primary visual cortex, with a potential link between both measures in schizophrenia. The relevance of electrophysiological biomarkers also lies in the link described with psychotic symptoms, motivating them to be used more widely in clinical practice to improve diagnosis
BRINGUIER, VINCENT. "Oscillations et integration neuronale dans le cortex visuel primaire." Paris 6, 1995. http://www.theses.fr/1995PA066274.
Full textMonier, Cyril. "Diversité fonctionnelle de l'intégration synaptique dans le cortex visuel primaire." Paris 6, 2002. http://www.theses.fr/2002PA066494.
Full textCharbonneau, Valérie. "Caractérisation des connexions du cortex visuel primaire chez deux modèles de souris aveugles." Thèse, Université du Québec à Trois-Rivières, 2011. http://depot-e.uqtr.ca/1230/1/030175007.pdf.
Full textLaramée, Marie-Eve. "Facteurs déterminant la structure des afférences et efférences du cortex visuel primaire chez la souris." Thèse, Université du Québec à Trois-Rivières, 2012. http://depot-e.uqtr.ca/6176/1/030405512.pdf.
Full textReynaud, 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.
Full textOur 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
René, Alice. "Plasticité synaptique et fonctionnelle dans le cortex visuel primaire : une étude par conditionnement theta - burst in vivo." Paris 6, 2007. http://www.theses.fr/2007PA066656.
Full textSeriès, 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.
Full textThe 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
Debanne, Dominique. "Plasticite fonctionnelle de l'organisation spatiale des champs recepteurs du cortex visuel primaire du chat : etude extra- et intracellulaire." Paris 6, 1992. http://www.theses.fr/1992PA066111.
Full textKlein, Isabelle. "Etude anatomo-fonctionnelle du cortex visuel primaire au cours de l'imagerie visuelle : approche par imagerie par résonance magnétique fonctionnelle." Paris 11, 2003. http://www.theses.fr/2003PA112291.
Full textVisual imagery is a brain state that gives rise to visual experience on the basis of stored information, not current input from the eyes. Convergent results from psychophysical, neuroimaging and studies of brain damaged patients have shown that mental imagery shares many of the functional properties and cortical structures used in visual perception. However a fundamental question that remains unresolved is whether visual imagery shares the "low-level" neural mechanisms required to perceive the external world. We used event-related functional magnetic resonance imaging to detect and characterize the activity in the primary visual cortex (or area V1) during visual imagery. In a first experiment, we tested two general hypotheses: The first was that V1 is activated only when images with many details are formed and used, and the second was that V1 is activated whenever images are formed, even if they are not necessarily used to perform a task. The results revealed reproducible transient activation in this area whenever subjects generated or evaluated a mental image. This transient activation was strongly enhanced when subjects evaluated characteristics of objects, whether or not details actually needed to be extracted from the image to perform the task. In a second experiment, we tested the hypothesis that the orientation of a visualized pattern is directly reflected by the orientation of activity in retinopically organized early visual cortices. The primary visual cortex of primates, including humans, is retinotopically organized; the spatial pattern of light striking the retinas is physically preserved (with some metric distortions) on the surface of cortex itself. We asked subjects to view or visualize a flashing bar either vertically or horizontally. The results show that for most subjects, the topography of the activation produced by imagined stimuli closely matched corresponding cortical representations of the visual field. Although understanding the precise nature of neural mechanisms that causally link activity in area V1 to visual imagery requires further investigation, the present results provides strong evidence that visual mental imagery recruits the earliest stages of the visual system
Chavane, Frédéric. "Diversite d'expression fonctionnelle du champ d'integration synaptique : une re-evaluation intracellulaire des champs recepteurs des neurones du cortex visuel primaire." Paris 6, 1999. http://www.theses.fr/1999PA066109.
Full textChappert-Piquemal, Catherine. "Analyse anatomo-fonctionnelle du développement postnatal et de la plasticité du cortex visuel primaire d'un primate du Nouveau Monde "Callithrix jacchus"." Montpellier 2, 1997. http://www.theses.fr/1997MON20133.
Full textEl, Boustani Sami. "Learning and coding correlations in stochastic network states." Paris 6, 2010. http://www.theses.fr/2010PA066279.
Full textWatroba, Laurent. "Plasticité de la carte corticale visuelle primaire calleuse du chat adulte : étude fonctionnelle et mécanismes sous-jacents." Paris 6, 2002. http://www.theses.fr/2002PA066374.
Full textBohi, 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.
Full textIn 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
Gazeres, Nicolas. "Modelisation de la structure on/off des champs recepteurs simples dans la couche iv du cortex visuel primaire chez le chat : interaction entre excitation genouillee et reverberation intracorticale." Paris 6, 1999. http://www.theses.fr/1999PA066206.
Full textMontardy, 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.
Full textWe 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
Le, Bec Benoît. "Lateral connectivity : propagation of network belief and hallucinatory-like states in the primary visual cortex." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS509.
Full textIn the primary visual cortex (V1), we examined the functional impact of centripetal apparent motion sequences originating from the far periphery and converging towards the receptive field of cortical cells along their preferred orientation axis. At high saccadic speed, the anisotropic congruency of elementary stimuli composing a coherent motion is crucial in the diffusion and lateral integration of contextual information. At the electrophysiological level, those results correspond to a latency advance and an amplitude gain of sub and suprathreshold responses, indicating the existence of a dynamic association field where form and motion are already bound in V1. Restricting the apparent motion to the silent periphery result in an invasion of the receptive field by predictive activity. This latter suggests the existence of a mechanism of lateral diffusion intrinsic to V1 that allows to solve the motion extrapolation problem. Second, we posit that geometric hallucinations reflect a long-distance spatial opponency of horizontal connectivity that structure the self organization of V1 ongoing activity, expressing itself through a model of interacting hypercolumns resulting in the formation of neural stripes on V1 surface. We designed visual stimuli in which perturbation by a 1/fα noise of a network highly adapted to geometric inducers result in perception of opponent planforms. Our results suggest that those dynamic percepts correspond to propagating waves of synaptic activity that are detectable at the level of V1 cells under the form of oscillations compatible with the local geometry and the dynamic of the induced percepts
Muller, Lyle. "Spatiotemporal dynamics in neocortex : quantification, analysis, models." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2014. http://tel.archives-ouvertes.fr/tel-01067199.
Full textBéhuret, Sébastien. "EXPLORATION PAR DES INTERFACES HYBRIDES DU CODE NEURONAL ET DES MÉCANISMES DE RÉGULATION DE L'INFORMATION SENSORIELLE DANS LE SYSTÈME VISUEL." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00714145.
Full textSavier, Élise. "Rôle des éphrines-As rétiniennes dans la mise en place des cartes visuelles." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAJ042/document.
Full textEfficient sensory processing requires correct alignment of neural maps throughout the brain. In the superficial layers of the superior colliculus in the midbrain, projections from retinal ganglion cells and V1 cortex must be aligned to form a visuotopic map, but the basic principle and underlying mechanism are elusive and still incomplete. In a new mouse model, over-expression of ephrin-A3 in a subset of retinal ganglion cells disrupts the cortico-collicular map alignment onto the retino-collicular map, creating a visuotopic mismatch. In vivo inactivation of retinal ephrin-A3 over-expression restores a wild-type corticocollicular map. Theoretical analyses using an original algorithm models the stochastic nature of maps formation and alignment, and recapitulates our observations. Our results identify a basic principle for the alignment of converging maps and the associated mechanism, validated by a theoretical model
Passarelli, Yannick. "Impact of natural scenes on the reliability and correlations of cortical dynamics across layers in cat primary visual cortex." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS291.
Full textThe principle of efficient coding suggests that processing in the early visual system should be optimized and adapted to the environmental statistics. An intracellular study of the primary visual cortex (V1) in the anesthetized and paralyzed cat showed that the reliability of the neural response is optimized for natural statistics. Using the same natural and artificial stimuli, we recorded the neuronal population activity (single unit, multi-unit and local field potentials) in cat’s V1 with high-density linear silicon probes. We first investigated the reliability and of the mesoscopic signal with the intracellular signal and explored its laminar dependency. Our results showed that natural images evoke, at all scales, the most reliable response, suggesting that V1 is better suited to efficiently encode natural statistics. In addition, granular and infragranular layers displayed higher reliability levels than the supragranular one. This argues for a functional filtering of the pertinent information between these layers. We also explored which statistics of the natural images produce this reliable response. Finally, we specifically addressed the role of the correlations between neurons (within and between layers) by measuring the amount of shared variability and signal of the neuronal population in response to our stimulus set. We observed that natural images always evoked higher correlations. We did not observe a strong decorrelation at the single cell level but instead at the scale of groups of neurons, with those that are close together being more correlated and farther apart less correlated, arguing for a functional clustering of the neurons into coherent “neural mass”
Yavuz, Esin. "Source separation analysis of visual cortical dynamics revealed by voltage sensitive dye imaging." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00836931.
Full textBastien, Danielle. "Asymétries fonctionnelles du cortex visuel observées par spectroscopie proche de l’infrarouge fonctionnelle." Thèse, 2014. http://hdl.handle.net/1866/11588.
Full textThe present study aimed to further investigate retinotopic mapping and functional asymmetries within the human visual cortex using functional near-infrared spectroscopy (fNIRS), as well as the reliability of this technique. As expected, results showed a stronger visual cortical activation in the controlateral hemisphere and in the inverse upper/lower quadrant to the stimulation. We also measured significant stronger activations in the upper visual cortex (when lower hemifield stimuli were presented) compared to activations in the lower visual cortex (when upper hemifield stimuli were showed), especially when the visual stimulation was presented in the right visual field. This is the first study to confirm the vertical and horizontal asymmetries of the visual cortex with fNIRS technique. The present work also settles the reliability of this technique for functional mapping of the human brain.
Marshansky, Serguei. "Analyse des réponses neuronales du cortex visuel primaire du chat à la fréquence spatiale suite à des adaptations répétées." Thèse, 2010. http://hdl.handle.net/1866/4763.
Full textPrimary visual cortex neurons in adult cat are selective to different image properties as orientation, contrast and spatial frequency. This selectivity is characterized by action potentials as electrical activity from the visual neurons. This response occurs during the presentation of a luminous bar in the receptive fields of the neurons. Spatial frequency is the amount of luminous bars in a grating presented from a precise distance from the eyes and is measured in cycles per degree. Furthermore, it was establish until recently that cortical organisation in the adult remains inflexible following the critical period after birth. However, our results have revealed that spatial frequency selectivity is able to change after an imposition of a non-preferred spatial frequency, also called adapter. Following cortical activity recordings, there is a shift of the spatial frequency tuning curves in the direction of the adapter. A second adaptation at the same non-preferred spatial frequency produced a different neural response from the first adaptation. This “short-term plasticity” was already observed in the primary visual cortex for orientation selective neurons but not yet for spatial frequency. The results presented in this study suggest that such plasticity is possible and that visual neurons regulate their electrical responses through modulation of the weights of their synaptic afferences.
Bouchard, 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.
Full textCattan, 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.
Full textIn 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.
Nemri, Abdellatif. "Codage de l’information visuelle par la plasticité et la synchronisation des réponses neuronales dans le cortex visuel primaire du chat." Thèse, 2010. http://hdl.handle.net/1866/4756.
Full textSensory systems encode information about our environment into electrical impulses that propagate in networks of neurons. Understanding the neural code – the principles by which information is represented in neuronal activity – is one of the most fundamental issues in neuroscience. This thesis investigates in a series of 3 studies (S) two coding mechanisms, synchrony and adaptation, in neurons of the cat primary visual cortex (V1). In V1, neurons display selectivity for image features such as contour orientation, motion direction and velocity. Each neuron has at least one combination of features that elicits its maximum firing rate. Visual information is thus distributed among numerous neurons within and across cortical columns, modules and areas. Synchronized electrical activity between cells was proposed as a potential mechanism underlying the binding of related features to form coherent perception. However, the precise nature of the relations between image features that may elicit neuronal synchrony remains unclear (S1). In another coding strategy, sensory neurons display transient changes of their response properties following prolonged exposure to an appropriate stimulus (adaptation). In adult cat V1, orientation-selective neurons shift their preferred orientation after being exposed to a non-preferred orientation. How the adaptive behavior of a neuron is related to that of its neighbors remains unclear (S2). Finally, we investigated the relationship between synchrony and orientation tuning in neuron pairs, especially how synchrony is modulated during adaptation-induced plasticity (S3). Main results — (S1) We show that two stimuli in either convergent or divergent motion elicit significantly more synchrony in V1 neuron pairs than two stimuli with the same motion direction. Synchronization seems to encode the relation of cocircularity, of which convergent (centripetal) and divergent (centrifugal) motion are two special instances, and could thus play a role in contour integration. Our results suggest that V1 neuron pairs transmit specific information on distinct image configurations through stimulus-dependent synchrony of their action potentials. (S2) We show that after being adapted to a non-preferred orientation, cells shift their preferred orientation in the same direction as their neighbors in most cases (75%). Several response properties of V1 neurons depend on their location within the cortical orientation map. The differences we found between cell clusters that shift in the same direction and cell clusters with both attractive and repulsive shifts suggest a different cortical location, iso-orientation domains for the former and pinwheel centers for the latter. (S3) We found that after adaptation, neuron pairs that share closer tuning properties display a significant increase of synchronization. Recovery from adaptation is accompanied by a return to the initial synchrony level. Synchrony therefore seems to reflect the similarity in neurons’ response properties, and varies accordingly when these properties change. Conclusions — This thesis further advances our understanding of how visual neurons adapt to a changing environment, especially regarding cortical network dynamics. We also propose novel data about the potential role of synchrony. Especially, synchrony appears capable of binding various features, whether similar or dissimilar, suggesting superimposed neural assemblies.
Tran, Van Minh Antonin. "La vision aveugle suite à une ablation partielle du cortex visuel primaire : une étude en imagerie par résonance magnétique fonctionnelle." Thèse, 2018. http://hdl.handle.net/1866/22321.
Full textOliveira, Ferreira de Souza Bruno. "Impact of the pulvinar on the ventral pathway of the cat visual cortex." Thèse, 2019. http://hdl.handle.net/1866/21816.
Full textPrévost, François. "Développement physiologique des voies visuelles chez le rat normal et chez celui ayant subi des convulsions hyperthermiques." Thèse, 2011. http://hdl.handle.net/1866/4861.
Full textNeurons in superficial layers of the rat superior colliculus and primary visual cortex are sensitive to highly contrasted low spatial frequencies drifting at fast speeds. Between post-natal days 27-30 and adulthood, the optimal temporal frequencies of neurons in the primary visual cortex increase, whereas their contrast thresholds decrease. However, the optimal spatial frequencies, spatial resolution values and spatial bandwidths of these neurons are, soon after eyelid opening, similar to those observed in the adult rat. These neuronal response profiles suggest that the retino-collicular and retino-geniculo-cortical projections are mainly innervated by magnocellular and koniocellular retinal ganglion cells. Neurons in the primary visual cortex of rats having experienced hyperthermic seizures are, soon after eyelid opening, sensitive to low optimal spatial frequencies and show broad directional and temporal bandwidths, as well as elevated contrast thresholds when compared to neurons of normal rats. At adulthood, low optimal temporal frequencies and broad spatial bandwidths are also observed in rats having experienced hyperthermic seizures. The alteration of response profiles of neurons in the primary visual cortex of rats having experienced hyperthermic seizures suggests an unbalance between excitatory and inhibitory mechanisms in this cortical structure. These results also suggest that a single episode of febrile seizures could be sufficient to impede the development of the spatio-temporal receptive field properties of neurons in the primary visual cortex.