Thèses sur le sujet « Visual oscillations »
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Beardsley, Burt Jay. « The visual shape and multipole moments of the sun ». Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184229.
Texte intégralWieczorek, Kacper. « Investigating the relationship between microsaccades and oscillations in the human visual cortex ». Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/86785/.
Texte intégralAdjamian, Peyman. « Magnetoencephalography : technical improvements in image co-registration and studies of visual cortical oscillations ». Thesis, Aston University, 2002. http://publications.aston.ac.uk/12253/.
Texte intégralGallina, Jessica <1990>. « Alpha oscillations index the functionality and the plastic changes of the visual system ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10265/1/Jessica_Gallina_PhD_Thesis.pdf.
Texte intégralMyers, Nicholas. « The role of cortical oscillations in the control and protection of visual working memory ». Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:c85253e0-6713-4fbc-801b-5f5bc8dea705.
Texte intégralLowe, Scott Corren. « Decoding information from neural populations in the visual cortex ». Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28861.
Texte intégralMoratti, Stephan. « Modulation of stimulus driven neuronal oscillations by the emotional and motivational significance of visual stimuli ». [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975676911.
Texte intégralLe, 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.
Texte intégralIn 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
ZAZIO, AGNESE. « Impact of ongoing alpha oscillations on visual perception and neurophysiological response : an integration with a psychophysical approach ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2019. http://hdl.handle.net/10281/241241.
Texte intégralNeural oscillations are considered to be the building blocks of cognitive functioning, and in the last decades neuroscientists have developed fundamental theories on their role in brain dynamics. Recently, a growing body of evidences has shown that ongoing oscillatory activity can account for a considerable amount of variability in behavioral performance and in neurophysiological response. In the domain of visual perception, a crucial role is played by neural oscillations within alpha frequency range. Alpha activity is believed to exert an inhibitory function on stimulus processing and to reflect cortical excitability, both when it fluctuates spontaneously as well as when it is modulated, by top-down or bottom-up mechanisms. It has been recently suggested that alpha rhythm may not be considered as a unitary phenomenon; however, still little is known about the neural mechanisms associated with alpha activity as measured by non-invasive recordings. Furthermore, up to now most of the studies on the effects of ongoing alpha activity on visual perception focused on a special class of stimuli, i.e., with a near-threshold intensity, and much less is known about what happens in the response beyond sensory threshold. In the present work, we aimed at addressing these issues by studying the effects of ongoing alpha oscillations on perceptual and neurophysiological outcome in the visual domain. The first goal was to replicate recent findings on the effects of spontaneous fluctuations of pre-stimulus alpha power and phase on a visual detection task, by using near-threshold stimuli. In addition to the original study, the use of magnetoencephalography allowed us to reconstruct brain sources of pre-stimulus and evoked activity. In a second study, we aimed at modulating ongoing alpha activity by using a sensory deprivation paradigm, and tested the effects of such modulation by means of a wide range of stimulation intensities. The use of transcranial magnetic stimulation (TMS) with concurrent electroencephalography allowed to directly assess the neurophysiological and perceptual response to TMS, by means of TMS-evoked potentials and phosphene perception. Finally, in a third study we developed a formal model of the effects of ongoing alpha activity on visual perception, with the aim of disentangling possible neural mechanisms which cannot be discerned non-invasively. The model is based on cross-frequency interactions between alpha functional inhibition and gamma activity of sensory neurons and highlights the advantages of presenting a wide range of stimulus intensities in the study of the effects of pre-stimulus oscillatory activity, using a psychophysical approach. Taken together, our results are consistent with current literature about the inhibitory function played by ongoing alpha activity on visual perception. Indeed, both perceptual and neurophysiological response to an external stimulus were affected by pre-stimulus alpha activity, when it fluctuated spontaneously as well as when it was modulated by a sensory deprivation paradigm. Moreover, the present findings support the hypothesis that alpha oscillations subtend distinct mechanisms, and highlighted that new insights may arise from applying a psychophysical approach to the study of ongoing activity on perception. By using different methodological approaches, the present work provides novel advances in the field of non-invasive investigation of ongoing oscillations on behavior, specifically on alpha inhibition of visual perception.
Barnes, William Halley [Verfasser], Ralf A. W. [Akademischer Betreuer] Galuske et Matthias H. J. [Akademischer Betreuer] Munk. « Reversible Visual Hemineglect : the Role of Neural Oscillations in Primary Visual Cortex / William Barnes. Betreuer : Ralf A. W. Galuske ; Matthias H. J. Munk ». Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2016. http://nbn-resolving.de/urn:nbn:de:tuda-tuprints-51931.
Texte intégralBarnes, William [Verfasser], Ralf A. W. [Akademischer Betreuer] Galuske et Matthias H. J. [Akademischer Betreuer] Munk. « Reversible Visual Hemineglect : the Role of Neural Oscillations in Primary Visual Cortex / William Barnes. Betreuer : Ralf A. W. Galuske ; Matthias H. J. Munk ». Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2016. http://d-nb.info/111204468X/34.
Texte intégralFiorini, Matilde [Verfasser]. « NMDARs hypofunction in parvalbumin-expressing interneurons alters oscillations and sensory tuning in mouse primary visual cortex / Matilde Fiorini ». Tübingen : Universitätsbibliothek Tübingen, 2020. http://d-nb.info/1219903434/34.
Texte intégralBrüers, Sasskia. « Towards a « Neuro-Encryption » system : from understanding the influence of brain oscillations in vision to controlling perception ». Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30195/document.
Texte intégralOur brain activity is inherently rhythmic: oscillations can be found at all levels of organization. This rhythmicity in brain activity gives a rhythm to what we see: instead of continuously monitoring the environment, our brains take "snapshots" of the external world from 5 to 15 times a second. This creates perceptual cycles: depending on the phase of the underlying oscillation, our perceptual abilities fluctuate. Accumulating evidence shows that brains oscillations at various frequencies are instrumental in shaping visual perception. At the heart of this thesis lies the White Noise Paradigm, which we designed as a tool to better understand the influence of oscillations on visual perception and which ultimately could be used to control visual perception. The White Noise Paradigm uses streams of flashes with random luminance (i.e. white noise) as stimuli, which have been shown to constrain brain oscillations in a predictable manner. The impulse response to WN sequences has a strong (subject specific) oscillatory component at ~10Hz akin to a perceptual echo. Since the impulse response is a model of how our brains respond to one single flash in the sequence, they can be used to reconstruct (rather than record) the brain activity to new stimulation sequences. We then present near-perceptual threshold targets embedded within the WN sequences and extract the time course of these predicted/reconstructed background oscillations around target presentation. Thus, the reconstructed EEG can be used to study the influence of the oscillatory components on visual perception, independently of other types of signals usually recorded in the EEG. First, we validate the White Noise Paradigm by showing that: 1) the WN sequences do modulate behaviour, 2) the perceptual echoes evoked by these WN sequences are stable in time, 3) they are a (relatively) good model of the subject's recorded brain activity and 4) their neuronal basis can be found in the early visual areas. Second, we investigate the relationship between these constrained brain oscillations and visual perception. Specifically, we show that the reconstructed EEG can help us recover the true latency at which (theta) phase influences perception. Moreover, it can help us uncover a causal influence of (alpha) power on target detection, independently from any fluctuation in endogenous factors. Finally, capitalizing on the link between oscillations and perception, we build two algorithms used to control the perception of subjects. First, we build a "universal" forward model which can predict for any observer whether a particular target will be seen or not. Second, we build a subject-dependent model which can predict whether a particular subject (for whom EEG was recorded previously) will perceive a given target or not. Critically, this can be used to present targets optimized to be perceived by one subject only, to the detriment of all other subjects, creating a sort of "Neuro-Encryption" system
Chanes, Puiggros Lorena. « Frontal and parietal contributions to visual perception in humans ». Phd thesis, Université Pierre et Marie Curie - Paris VI, 2014. http://tel.archives-ouvertes.fr/tel-00989767.
Texte intégralNotbohm, Annika [Verfasser], Christoph S. [Akademischer Betreuer] Herrmann et Jonas [Akademischer Betreuer] Obleser. « The role of Steady- State Visual Evoked Potentials in the study of brain oscillations / Annika Notbohm ; Christoph Siegfried Herrmann, Jonas Obleser ». Oldenburg : BIS der Universität Oldenburg, 2017. http://nbn-resolving.de/urn:nbn:de:gbv:715-oops-30990.
Texte intégralNotbohm, Annika [Verfasser], Christoph Siegfried [Akademischer Betreuer] Herrmann et Jonas [Akademischer Betreuer] Obleser. « The role of Steady- State Visual Evoked Potentials in the study of brain oscillations / Annika Notbohm ; Christoph Siegfried Herrmann, Jonas Obleser ». Oldenburg : BIS der Universität Oldenburg, 2017. http://d-nb.info/1127208616/34.
Texte intégralLuo, Canhuang. « Le rôle des oscillations du cerveau dans la perception visuelle, l'attention et la conscience ». Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30280.
Texte intégralOscillations are ubiquitous in the brain. A large body of literature has supported that brain oscillations are not a by-product of brain activities; in fact, they shape our perception by modulating cortical excitability and facilitating neuronal communications. Consequently, our visual perception, attention and maybe even consciousness wax and wane across time. However, the role of oscillations in these perceptual or cognitive functions is not entirely understood. For visual perception and attention, although the relationship between them and brain oscillations has been established, it is unclear where and how these brain oscillations are generated. As for consciousness, how the oscillations are involved in producing conscious perception remains unknown. These are the questions the current thesis attempts to address. The thesis starts with brain oscillations in the most basic and best understood brain function - visual perception. It has been suggested that visual perception is an oscillatory process, sampling the world at the alpha frequency. Perceptual echoes are one demonstration of visual sampling. The echo is an impulse response function that oscillates at ~10 Hz in response to white-noise stimuli. While the temporal properties are gradually revealed, the origin of the echoes remains unclear. The first study set out to study the neural basis of perceptual echoes, and we found the echoes originate in the early visual cortex. Next, we move on to attention. It has been shown that attention samples the environment at theta frequency. A monkey study suggests that the theta oscillation of attention may arise from competitive receptive field interactions of V4. To investigate if the mechanism can be generalized to humans, we replicate the behavioral experiment in humans. Finally, in the last two studies, we examine brain oscillations in consciousness. Utilizing binocular rivalry, we first investigate if the perceptual echoes require consciousness. The results show that perceptual echoes can be elicited both when the stimulus is in consciousness and out of consciousness. Second, we investigate information flow during binocular rivalry and show an increased top-down beta and theta activities before perceptual switches. In conclusion, the brain is a dynamic system in which the oscillations flexibly facilitate various brain functions by playing different functional roles
Cevallos, Barragan Carlos. « THE RESONANCE OF BIOLOGICAL MOTION THROUGH VISUAL PERCEPTION IN THE HUMAN BRAIN ». Doctoral thesis, Universite Libre de Bruxelles, 2016. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/235472.
Texte intégralDoctorat en Sciences de la motricité
info:eu-repo/semantics/nonPublished
Freitag, F?bio Batista. « Encoding mechanisms based on fast oscillations in the retina of the cat and their dependencies on anesthesia ». Universidade Federal do Rio Grande do Norte, 2013. http://repositorio.ufrn.br:8080/jspui/handle/123456789/17028.
Texte intégralCoordena??o de Aperfei?oamento de Pessoal de N?vel Superior
Processing in the visual system starts in the retina. Its complex network of cells with different properties enables for parallel encoding and transmission of visual information to the lateral geniculate nucleus (LGN) and to the cortex. In the retina, it has been shown that responses are often accompanied by fast synchronous oscillations (30 - 90 Hz) in a stimulus-dependent manner. Studies in the frog, rabbit, cat and monkey, have shown strong oscillatory responses to large stimuli which probably encode global stimulus properties, such as size and continuity (Neuenschwander and Singer, 1996; Ishikane et al., 2005). Moreover, simultaneous recordings from different levels in the visual system have demonstrated that the oscillatory patterning of retinal ganglion cell responses are transmitted to the cortex via the LGN (Castelo-Branco et al., 1998). Overall these results suggest that feedforward synchronous oscillations contribute to visual encoding. In the present study on the LGN of the anesthetized cat, we further investigate the role of retinal oscillations in visual processing by applying complex stimuli, such as natural visual scenes, light spots of varying size and contrast, and flickering checkerboards. This is a necessary step for understanding encoding mechanisms in more naturalistic conditions, as currently most data on retinal oscillations have been limited to simple, flashed and stationary stimuli. Correlation analysis of spiking responses confirmed previous results showing that oscillatory responses in the retina (observed here from the LGN responses) largely depend on the size and stationarity of the stimulus. For natural scenes (gray-level and binary movies) oscillations appeared only for brief moments probably when receptive fields were dominated by large continuous, flat-contrast surfaces. Moreover, oscillatory responses to a circle stimulus could be broken with an annular mask indicating that synchronization arises from relatively local interactions among populations of activated cells in the retina. A surprising finding in this study was that retinal oscillations are highly dependent on halothane anesthesia levels. In the absence of halothane, oscillatory activity vanished independent of the characteristics of the stimuli. The same results were obtained for isoflurane, which has similar pharmacological properties. These new and unexpected findings question whether feedfoward oscillations in the early visual system are simply due to an imbalance between excitation and inhibition in the retinal networks generated by the halogenated anesthetics. Further studies in awake behaving animals are necessary to extend these conclusions
O processamento da informa??o visual se inicia na retina. A sua complexa rede de c?lulas com diferentes propriedades permite que a informa??o visual seja codificada em canais paralelos e transmitida para o n?cleo geniculado lateral (LGN) e o c?rtex. Na retina, tais respostas est?o frequentemente acompanhadas por oscila??es sincronizadas de alta frequ?ncia (30 90 Hz) em uma maneira dependente do est?mulo. Como demonstrado em estudos na r?, coelho, gato e macaco, respostas oscilat?rias ocorrem em geral a est?mulos relativamente grandes, podendo codificar propriedades globais do est?mulo como o tamanho e continuidade (Neuenschwander and Singer, 1996; Ishikane et al., 2005). Al?m disso, registros simult?neos em diferentes n?veis do sistema visual t?m mostrado que o padr?o de oscila??o nas c?lulas ganglionares retinianas ? transmitido para o c?rtex visual via LGN (Castelo-Branco et al., 1998). De uma forma geral, esses resultados sugerem que oscila??es sincronizadas em uma maneira feedforward s?o importantes na codifica??o da informa??o visual. No presente estudo feito no LGN de gatos anestesiados, investigamos o papel das oscila??es retinianas no processamento de informa??o visual atrav?s da apresenta??o de est?mulos complexos, como cenas naturais, pixels aleat?rios no tempo e espa?o, al?m de grades em movimento. Esse ? um importante passo para o entendimento de mecanismos de codifica??o em condi??es naturais, j? que grande parte dos estudos que investigaram o papel de oscila??es retinianas utilizaram-se de est?mulos simples e estacion?rios. An?lises de correla??o de respostas neuronais (spiking responses) confirmaram resultados pr?vios mostrando que respostas oscilat?rias na retina (observadas aqui a partir de registros no LGN) dependem do tamanho e estacionariedade do est?mulo. Para filmes de cenas naturais (em escala de cinza e preto e branco) oscila??es apareceram apenas por breves momentos provavelmente quando os campos receptores foram dominados por padr?es extensos e cont?nuos (para ambas as escalas). As atividades oscilat?rias parecem ser dependentes de uma massa cr?tica de c?lulas ativadas sugerindo que esse padr?o regular de atividade surge atrav?s de intera??es horizontais na retina. Nossos resultados mostram, al?m disto, que surpreendentemente oscila??es da retina no gato s?o dependentes da anestesia mediada por halotano. Na aus?ncia deste, atividades oscilat?rias estiveram ausentes independentemente das caracter?sticas dos est?mulos visuais. Resultados semelhantes foram obtidos para o isoflurano, anest?sico com propriedades farmacol?gicas similares. Esse novo e inesperado resultado nos faz questionar se oscila??es feedforward no sistema visual n?o seriam resultado de um desequil?brio entre correntes de excita??o e inibi??o nas redes retinianas gerado pelos anest?sicos halogenados. Experimentos futuros em animais acordados ser?o necess?rios para confirmar essas conclus?es
Brealy, Jennifer. « The relationship between variation in genes, GABA, structure and gamma oscillations in the visual and auditory system of healthy individuals and psychiatric disorder ». Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/75463/.
Texte intégralStengel, Chloé. « Frontal contributions to conscious visual perception through causal manipulation of brain rhythms ». Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS354.
Texte intégralCortical oscillatory activity has been shown to subtend a wide variety of cognitive processes. In particular, there is strong evidence for a causal role of high-beta (30 Hz) oscillations in the right Frontal Eye Field (FEF) for the orientation of attention and the facilitation of perception. However, for the same area in the left hemisphere, recent evidence has suggested that another pattern of brain activity: neuronal noise, i.e. unpredictable neuronal activity, could enhance processing of weak sensory stimuli and be needed to improve conscious detection. We use Transcranial Magnetic Stimulation (TMS) to either entrain high-beta cortical oscillations or modulate neuronal noise level in the left and right FEFs and we record electrophysiological signals of healthy subjects performing a visual detection at threshold task.We show, in the right hemisphere, that rhythmic patterns of TMS increase high-beta local and inter-regional synchronization in fronto-parietal regions and bring strong evidence for a causal role of high-beta oscillations for conscious visual perception. In the left hemisphere, we show that arrhythmic or irregular patterns of TMS increase neuronal noise throughout the attention network. Lastly, we show that these effects are caused by direct cortical stimulation and cannot be generated by the clicking sounds associated with the discharge of TMS pulses. We report only non-specific effects of the auditory stimulation on perceptual decision-making and activity in the auditory cortex. These findings contribute to a better understanding of coding strategies in the bilateral network for attention orienting and the specific and non-specific effects of TMS
Alexander, Kevin Eugene. « Visual Sampling with the EEG Alpha Oscillation ». Wright State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=wright1596757044725515.
Texte intégralBRINGUIER, VINCENT. « Oscillations et integration neuronale dans le cortex visuel primaire ». Paris 6, 1995. http://www.theses.fr/1995PA066274.
Texte intégralLiu, Xiaochen. « Modelling Functional Maps and Associated Visual Gamma Activities in the Primary Visual Cortex ». Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/28536.
Texte intégralButler, Colleen Ann. « Motion sickness with fore-and-aft and pitch oscillation : effect of the visual scene ». Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/51306/.
Texte intégralCHEN, HONGYI. « GPS-oscillation-robust Localization and Visionaided Odometry Estimation ». Thesis, KTH, Maskinkonstruktion (Inst.), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-247299.
Texte intégralGPS/IMU integrerade system används ofta för navigering av fordon. Algoritmen för detta kopplade system är normalt baserat på ett Kalmanfilter. Ett problem med systemet är att oscillerade GPS mätningar i stadsmiljöer enkelt kan leda till en lokaliseringsdivergens. Dessutom kan riktningsuppskattningen vara känslig för magnetiska störningar om den är beroende av en IMU med integrerad magnetometer. Rapporten försöker lösa lokaliseringsproblemet som skapas av GPS-oscillationer och avbrott med hjälp av ett adaptivt förlängt Kalmanfilter (AEKF). När det gäller riktningsuppskattningen används stereovisuell odometri (VO) för att försvaga effekten av magnetiska störningar genom sensorfusion. En Visionsstödd AEKF-baserad algoritm testas i fall med både goda GPS omständigheter och med oscillationer i GPS mätningar med magnetiska störningar. Under de fallen som är aktuella är algoritmen verifierad för att överträffa det konventionella utökade Kalmanfilteret (CEKF) och ”Unscented Kalman filter” (UKF) när det kommer till positionsuppskattning med 53,74% respektive 40,09% samt minska fel i riktningsuppskattningen.
Tallon-Baudry, Catherine. « Rôle des oscillations 40 Hz dans l'intégration de l'information visuelle : étude électro- et magnéto-encéphalographique ». Lyon 1, 1997. http://www.theses.fr/1997LYO1T061.
Texte intégralThillay, Alix. « Etude du traitement cérébral d'un contexte visuel prédictif dans l'autisme ». Thesis, Tours, 2015. http://www.theses.fr/2015TOUR3314/document.
Texte intégralIndividuals with autism react in an unusual and disproportionate way if unpredictable changes occur in their environment. The aim of the present work is to investigate brain mechanisms involved in visual predictive context processing in adolescents and adults with autism using analysis of event-related potentials and brain oscillations. The developmental study shows that mechanisms of prediction are mature by the age of 12 in typically developing adolescents. Individuals with autism are able to extract relevant information from the stimulus train in a simple, certain and explicit context, to use it in order to anticipate the occurrence of an event and to have an appropriate response, suggesting preserved extraction and use of predictive information during a certain context. However, individuals with autism over-anticipate stimuli during an uncertain context, consistent with the sense of being overwhelmed by incoming information, and also cannot flexibly modulate cortical activity according to changing levels of uncertainty, in agreement with atypical adaptation in an ever-changing world. This work suggests that a dysfunction of predictive processing in an uncertain context might provide a theoretical framework to better understand the symptoms encountered in autism
Herculano-Houzel, Suzana. « Modulation of neuronal synchronous oscillations : dynamic variation with level of cortical activation and long-term use-dependent modification ». Paris 6, 1999. http://www.theses.fr/1999PA066610.
Texte intégralMagazzini, Lorenzo. « Quality control of visual gamma oscillation frequency in studies of pharmacology, cognitive neuroscience and large-scale multi-site collaborations ». Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/98613/.
Texte intégralChow, Eric Ho Chi. « Postural disturbance and vection when viewing visual stimulus oscillating in roll and fore-and-aft directions : effects of frequency and peak velocity / ». View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?IELM%202008%20CHOW.
Texte intégralKoenig, Roger. « Comment le sens est-il extrait de l'information visuelle ? Le système visuel exploré des catégories à la conscience ». Phd thesis, Université Paul Sabatier - Toulouse III, 2012. http://tel.archives-ouvertes.fr/tel-00736494.
Texte intégralKoenig, Alexis Roger. « Comment le sens est-il extrait de l'information visuelle ? : le système visuel exploré des catégories à la conscience ». Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1749/.
Texte intégralHow does sense emerges in the visual system? In this thesis we will be focused on the visual system of human and non-human primates and their large capacity of extract and represent visual information. We studied several levels of visual representations from those related to the extraction of coarse visual features to the emergence of conscious visual representations. This manuscript presents six works in which we explored: (1) the visual features necessary to perform ultra-rapid visual categorization in monkeys and humans using psychophysics, (2) the spatio-temporal dynamics of visual attention in humans using psychophysics, (3) the neural correlates of high-level visual representations using EEG tanks to the development of an innovative technique called SWIFT, (4) the neural correlates of visual consciousness under binocular rivalry using EEG, (5) the synchrony of brain signals as a function of conscious recognition using intracranial electrodes implanted in epileptic patients and (6) the neural correlates associated with conscious perception in monkeys using intracranial electrodes. The results of these works allowed outlining a tentative model of visual perception aimed to dissociate attention and consciousness
Chaumon, Maximilien. « Apprentissage implicite du contexte visuel et guidage de la perception : Expériences MEG et EEG intracrânien ». Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00310152.
Texte intégralNous proposons que l'activité gamma permet la création et l'affûtage d'une représentation neuronale par des mécanismes de plasticité dépendante de la synchronie des potentiels d'action (spike timing dependent plasticity, STDP). Cette représentation une fois créée serait activée très rapidement pour biaiser le traitement cérébral, permettant la prise en compte de l'expérience vécue dès les étapes précoces du traitement sensoriel.
Ossandon, Valdes Tomas. « A prefrontal-temporal network underlying state changes between Stimulus-Driven and Stimulus-Independent Cognition ». Phd thesis, Université Claude Bernard - Lyon I, 2010. http://tel.archives-ouvertes.fr/tel-00726306.
Texte intégral(8086100), Samuel T. Kissinger. « Visual experience-dependent oscillations in the mouse visual system ». Thesis, 2019.
Trouver le texte intégralThe 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.
Barnes, William. « Reversible Visual Hemineglect : the Role of Neural Oscillations in Primary Visual Cortex ». Phd thesis, 2016. https://tuprints.ulb.tu-darmstadt.de/5193/1/Thesis%20Barnes%20PDF%20Dec2015.pdf.
Texte intégralBENEDETTO, ALESSANDRO. « The temporal dynamics of vision for action and perception ». Doctoral thesis, 2017. http://hdl.handle.net/2158/1079075.
Texte intégralBharmauria, Vishal. « Investigating the encoding of visual stimuli by forming neural circuits in the cat primary visual cortex ». Thèse, 2016. http://hdl.handle.net/1866/14129.
Texte intégralBackground ‘Connectomics’— the mapping of neural connections, is a rapidly advancing field in neurosciences and it promises significant insights into the brain functioning. The formation of neuronal circuits in response to the sensory environment is an emergent property of the brain; however, the knowledge about the precise nature of these sub-networks is still limited. Even at the level of the visual cortex, which is the most studied area in the brain, how sensory inputs are processed between its neurons, is a question yet to be completely explored. Heuristically, this invites an investigation into the emergence of micro-circuits in response to a visual input — that is, how the intriguing interplay between a stimulus and a cell assembly is engineered and modulated? Methods Neuronal assemblies were recorded in response to randomly presented drifting sine-wave gratings in the layer II/III (area 17) of the primary visual cortex (V1) in anaesthetized cats using tungsten multi-electrodes. Cross-correlograms (CCGs) between simultaneously recorded neural activities were computed to reveal the functional links between neurons that were indicative of putative synaptic connections between them. Further, the peristimulus time histograms (PSTH) of neurons were compared to divulge the epochal synergistic collaboration in the revealed functional networks. Thereafter, perievent spectrograms were computed to observe the gamma oscillations in emergent microcircuits. Noise correlation (Rsc) was calculated for the connected and unconnected neurons within these microcircuits. Results The functionally linked neurons collaborate synergistically with augmented activity in a 50-ms window of opportunity compared with the functionally unconnected neurons suggesting that the connectivity between neurons leads to the added excitability between them. Further, the perievent spectrogram analysis revealed that the connected neurons had an augmented power of gamma activity compared with the unconnected neurons in the emergent 50-ms window of opportunity. The low-band (20-40 Hz) gamma activity was linked to the regular-spiking (RS) neurons, whereas the high-band (60-80 Hz) activity was related to the fast-spiking (FS) neurons. The functionally connected neurons systematically displayed higher Rsc compared with the unconnected neurons in emergent microcircuits. Finally, the CCG analysis revealed that there is an activation of a salient functional network in an assembly in relation to the presented orientation. Closely tuned neurons exhibited more connections than the distantly tuned neurons. Untuned assemblies did not display functional linkage. In short, a ‘signature’ functional network was formed between neurons comprising an assembly that was strictly related to the presented orientation. Conclusion Indeed, this study points to the fact that a cell-assembly is the fundamental functional unit of information processing in the brain, rather than the individual neurons. This dilutes the importance of a neuron working in isolation, that is, the classical firing rate paradigm that has been traditionally used to study the encoding of a stimulus. This study also helps to reconcile the debate on gamma oscillations in that they systematically originate between the connected neurons in assemblies. Though the size of the recorded assemblies in the current investigation was relatively small, nevertheless, this study shows the intriguing functional specificity of interacting neurons in an assembly in response to a visual input. One may form this study as a premise to computationally infer the functional connectomes on a larger scale.
Mikulskaya, Elena. « Visual processing, visual attention and their neural correlates in early-onset cannabis users ». Thesis, 2016. http://hdl.handle.net/1959.13/1312742.
Texte intégralCannabis use worldwide has been increasing steadily over the past decade. The current trend towards legalization of cannabis for medical purposes and/or recreational use increases the potential to expose more and younger people to cannabis. Early age of onset has been linked to visual and attentional deficits in adulthood suggested to arise from blunted dopaminergic functioning. Dopamine is a neurotransmitter, critically important for efficient visual and attentional functioning in addition to general cognitive and motor behaviour. The overall aim of this thesis was to investigate in depth low level visual processing (Phase 1) and visual attention and underlying neural processing (Phase 2) in early-onset cannabis users. Static and dynamic contrast thresholds were examined in Experiments 1 and 2 and motion discrimination thresholds were examined in Experiment 3 under normal and low luminance conditions. An index of brain dopamine production was also collected and compared in Experiment 4. Static but not dynamic contrast detection thresholds were significantly higher in the cannabis group (21 participants: 18 of whom commenced cannabis use before the age of 17) compared to the control group (20 participants) under mesopic levels of luminance. Both static and dynamic contrast thresholds were positively correlated with frequency of use in the cannabis group. Discrimination of direction of translational and radial motion was examined in Experiment 3 under normal and mesopic luminance and at two levels of stimuli contrast: 12 and 24%. Independently of luminance level and motion type, coherence thresholds were significantly higher in the cannabis group at 24% stimuli contrast compared to the control group and in particular the thresholds were higher for radial compared to translational motion, although the differences failed to reach statistical significance. Again, the thresholds in the cannabis group were higher with more frequent cannabis use. We also found significantly lower spontaneous Eye Blink Rate (EBR) in the cannabis group compared to the control group in Experiment 4. We argued that lower dopamine may underlie the higher thresholds shown by the cannabis group across all visual tasks in Phase 1. In Phase 2 of this thesis behavioural data and EEG recordings were collected from 53 participants in four experiments. ERPs and gamma band activity were extracted from EEG recordings and compared between the control group (29 participants) and the cannabis group (24 participants: all commenced cannabis use before age 17). In Experiment 5 we investigated the neural correlates (ERPs and gamma band activity) of radial motion processing to further investigate the results of Experiment 3. As expected reduced ERP amplitudes to motion stimuli were shown by the cannabis group compared to the control group. Motion stimuli were also employed in the oddball task in Experiment 6 in which we aimed to investigate the neural correlates of selective attention. The cannabis group showed significant reductions in P3b amplitude in response to target stimuli, overall reduced amplitude and delayed latency of P3b, and increased connectivity in the gamma range to target and standard stimuli. Increased connectivity for both types of stimuli was argued to compensate for reduced attentional resource allocation, as indexed by reduced P3b amplitudes in the cannabis group. Cannabis related and neutral words were used in a word recognition task in Experiment 7, with target words presented briefly, then presented paired with a distractor for recognition. Cannabis and neutral pictures used as primes followed by cannabis and neutral words in a lexical decision task were employed in Experiment 8. We found some evidence for cannabis biased attention in the cannabis group, as indexed by differences in ERP components and the connectivity patterns in gamma band activity. Overall, in both experiments, the cannabis group showed increased processing effort toward both cannabis and neutral stimuli. The current thesis has demonstrated that visual processing, attention and underlying brain activity are altered by cannabis use with early age of onset. Consistent with previous research, selective attention and its neural correlates differed in respect to stimuli identity, cannabis or neutral, in early-onset cannabis users. It has also been shown that cannabis related stimuli, presented at subliminal levels, influenced attention and subsequent processing of cannabis and neutral stimuli in the cannabis group. Future investigations could examine in depth the effects of early-onset cannabis use on visual processing and attention, and whether and how it is modulated by concomitant reductions in dopamine.
Moratti, Stephan [Verfasser]. « Modulation of stimulus driven neuronal oscillations by the emotional and motivational significance of visual stimuli / vorgelegt von Stephan Moratti ». 2005. http://d-nb.info/975676911/34.
Texte intégral« Neural Mechanisms of Sensory Integration : Frequency Domain Analysis of Spike and Field Potential Activity During Arm Position Maintenance with and Without Visual Feedback ». Doctoral diss., 2017. http://hdl.handle.net/2286/R.I.46363.
Texte intégralDissertation/Thesis
Doctoral Dissertation Biomedical Engineering 2017
Ferrandez, Roxanne. « Profil temporel de l’efficacité du traitement visuel en reconnaissance d’objets et de visages ». Thèse, 2019. http://hdl.handle.net/1866/23828.
Texte intégralVariations in visual processing effectiveness through time were investigated using random temporal stimulus sampling. Twenty-four adults named photographs of either familiar objects (experiment 1) or famous faces (experiment 2). Stimuli were made by a linear combination of the target image and high density white visual noise. Signal-to-noise ratio varied throughout the 200 ms stimulus duration. A new temporal sampling function was generated on each trial by the integration of random amplitude and phase sinusoidal waves of frequency between 5 and 55 Hz (in 5 Hz steps). Temporal classification vectors (CV) were calculated by subtracting the weighted sum of the signal-to-noise ratio associated to errors from that associated to correct responses. Time-frequency classification images (CI) were obtained by applying the same procedure on the outcome of time-frequency analyses applied to the sampling functions of each trial. In both experiments, the temporal CVs were highly variable across participants, but the time-frequency CIs were remarkably similar across participants (inter-subject coherence of .93 and .57 for experiments 1 and 2 respectively). T-tests revealed multiple differences between the time-frequency CIs obtained with familiar objects and faces, but also with non-familiar objects and words analyzed in previous studies. Therefore, theses CIs are sensitive to stimulus type, but also to stimulus familiarity. The present results indicate rapid variations of visual encoding effectiveness in the initial 200 ms of stimulus exposure and suggests that the time-frequency CIs tap a highly fundamental aspect of visual processing, hypothetically linked to brain oscillations.
(10531388), Alexandr Pak. « CONTEXTUAL MODULATION OF NEURAL RESPONSES IN THE MOUSE VISUAL SYSTEM ». Thesis, 2021.
Trouver le texte intégralCastellano, Marta. « Computational Principles of Neural Processing : modulating neural systems through temporally structured stimuli ». Doctoral thesis, 2014. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2014121112959.
Texte intégralPodubnaia-Birca, Ala. « Caractérisation électro-clinique des convulsions fébriles et risque d’épilepsie ». Thèse, 2008. http://hdl.handle.net/1866/2775.
Texte intégralThe incidence of epilepsy in children with febrile seizures (FS) varies from 2 to 3%, but available clinical tools do not allow the identification of those children who will later develop epilepsy. Evidences have shown quantitative EEG abnormalities, more particularly revealed by intermittent photic stimulation (IPS), in patients with epilepsy. No studies have yet examined quantitative EEG parameters in children with FS. It is not known either whether they can be relevant to the evaluation of FSs prognosis. The objectives of this research program were to identify, first, clinical risk factors for developing epilepsy after FS and, second, to determine quantitative EEG markers that differentiate FS patients from normal controls and may aid to evaluate their prognosis. In order to meet our first objective, we reviewed the charts of 482 children with FS, aged 3 months to 6 years. Using survival statistics, we described risk factors for developing partial (prenatal antecedents, developmental delay, prolonged and focal FS) and generalized (family history of epilepsy, recurrent FS and FS after the age of 4 years) epilepsy after FS. In addition, we identified several distinct clinical phenotypes related to the prognosis of FS: (i) simple FS with a family history of FS, not related to a subsequent epilepsy, (ii) recurrent FS with a family history of epilepsy and an increased risk of generalised epilepsy and (iii) focal FS with a family history of epilepsy and an increased risk of partial epilepsy. In order to meet our second objective, we analyzed the steady-state visual potentials (SSVEP) evoked by IPS (5, 7.5, 10 and 12.5 Hz) as a function of age. The high density EEG (128 channels) was recorded in 61 normal children between 6 months and 16 years of age and 8 adults. We showed different topographical development of low (5-15 Hz) and high (30-50 Hz) frequency SSVEP components phase alignment. Thus, low frequency phase alignment increased with age only over the frontal and occipital regions, whereas high frequency phase alignment increased over all cerebral regions. Then, using the same methodology, we investigated whether children with FS show abnormalities of gamma frequency SSVEP components. We show an increase of both magnitude and phase alignment of the gamma frequency SSVEP components in 12 FS patients compared to 5 siblings of FS patients and 15 control children between 6 and 36 months of age. This study has identified distinct electro-clinical phenotypes that differentiate FS patients from the group of siblings and controls. Future studies should investigate whether detected abnormalities are associated with the clinical presentation of FS and their prognosis. This could help identify children with FSs who will later develop epilepsy and would eventually allow the institution of an early neuroprotective treatment.
Wu, Ying-Ting, et 吳熒庭. « If I Were for Real : Visual Works Derived from the Oscillation between Construction and Deconstruction of Self Identity ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/63154079607641203051.
Texte intégral實踐大學
時尚與媒體設計研究所
101
If I take off the mask, will the face still be clearly recognizable? I don’t want anyone to see me through, because I’m concealing a truth that is inconvenient to me. The essential part of the thesis was inspired by the struggle between external behaviors and internal emotions as a result of a self-awareness experience during my adolescence. I feel a sense of security as I intend to be invisible and be alienated from interpersonal relations; however, being in great solitude, I gradually cannot distinguish true from fake and begin to negate myself. My secret is concealed and nourished by lies, it sprouts evergreen vines and they tie me up so severely that I could suffocate. “To be happy is to be able to become aware of oneself without fright,” writes Walter Benjamin. I am unable to get rid of my past life experience, but I am willing to transform them into the inexhaustible energy of creating my pieces and hope they could unleash the masks on me. Furthermore, with visual works derived from the concept of stream of consciousness, my past, present and future will ultimately be interweaved to portrait the real me.