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Academic literature on the topic 'Décodage neural'
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Dissertations / Theses on the topic "Décodage neural"
Siahpoush, Shadi. "Décodage neuronal dans le système auditif central à l'aide d'un modèle bilinéaire généralisé et de représentations spectro-temporelles bio-inspirées." Mémoire, Université de Sherbrooke, 2015. http://hdl.handle.net/11143/8027.
Full textAbstract : In this project, Bayesian neural decoding is performed on the neural activity recorded from the inferior colliculus of the guinea pig following the presentation of a vocalization. In particular, we study the impact of different encoding models on the accuracy of reconstruction of different spectro-temporal representations of the input stimulus. First voltages recorded from the inferior colliculus of the guinea pig are read and the spike trains are obtained. Then, we fit an encoding model to the stimulus and associated spike trains. Finally, we do neural decoding on the pairs of stimuli and neural activities using the maximum a posteriori optimization method to obtain the reconstructed spectro-temporal representation of the signal. Two encoding models, a generalized linear model (GLM) and a generalized bilinear model (GBM), are compared along with three different spectro-temporal representations of the input stimuli: a spectrogram and two bio-inspired representations, i.e. a gammatone filter bank (GFB) and a spikegram. The parameters of the GLM and GBM including spectro-temporal receptive field, post spike filter and input non linearity (only for the GBM) are fitted using the maximum likelihood optimization (ML) algorithm. Signal to noise ratios between the reconstructed and original representations are used to evaluate the decoding, or reconstruction accuracy. We experimentally show that the reconstruction accuracy is better with the spikegram representation than with the spectrogram and GFB representation. Furthermore, using a GBM instead of a GLM significantly increases the reconstruction accuracy. In fact, our results show that the spikegram reconstruction accuracy with a GBM fitting yields an SNR that is 3.3 dB better than when using the standard decoding approach of reconstructing a spectrogram with GLM fitting.
Ozcelik, Furkan. "Déchiffrer le langage visuel du cerveau : reconstruction d'images naturelles à l'aide de modèles génératifs profonds à partir de signaux IRMf." Electronic Thesis or Diss., Université de Toulouse (2023-....), 2024. http://www.theses.fr/2024TLSES073.
Full textThe great minds of humanity were always curious about the nature of mind, brain, and consciousness. Through physical and thought experiments, they tried to tackle challenging questions about visual perception. As neuroimaging techniques were developed, neural encoding and decoding techniques provided profound understanding about how we process visual information. Advancements in Artificial Intelligence and Deep Learning areas have also influenced neuroscientific research. With the emergence of deep generative models like Variational Autoencoders (VAE), Generative Adversarial Networks (GAN) and Latent Diffusion Models (LDM), researchers also used these models in neural decoding tasks such as visual reconstruction of perceived stimuli from neuroimaging data. The current thesis provides two frameworks in the above-mentioned area of reconstructing perceived stimuli from neuroimaging data, particularly fMRI data, using deep generative models. These frameworks focus on different aspects of the visual reconstruction task than their predecessors, and hence they may bring valuable outcomes for the studies that will follow. The first study of the thesis (described in Chapter 2) utilizes a particular generative model called IC-GAN to capture both semantic and realistic aspects of the visual reconstruction. The second study (mentioned in Chapter 3) brings new perspective on visual reconstruction by fusing decoded information from different modalities (e.g. text and image) using recent latent diffusion models. These studies become state-of-the-art in their benchmarks by exhibiting high-fidelity reconstructions of different attributes of the stimuli. In both of our studies, we propose region-of-interest (ROI) analyses to understand the functional properties of specific visual regions using our neural decoding models. Statistical relations between ROIs and decoded latent features show that while early visual areas carry more information about low-level features (which focus on layout and orientation of objects), higher visual areas are more informative about high-level semantic features. We also observed that generated ROI-optimal images, using these visual reconstruction frameworks, are able to capture functional selectivity properties of the ROIs that have been examined in many prior studies in neuroscientific research. Our thesis attempts to bring valuable insights for future studies in neural decoding, visual reconstruction, and neuroscientific exploration using deep learning models by providing the results of two visual reconstruction frameworks and ROI analyses. The findings and contributions of the thesis may help researchers working in cognitive neuroscience and have implications for brain-computer-interface applications
Corlay, Vincent. "Decoding algorithms for lattices." Electronic Thesis or Diss., Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAT050.
Full textThis thesis discusses two problems related to lattices, an old problem and a new one.Both of them are lattice decoding problems: Namely, given a point in the space, find the closest lattice point.The first problem is related to channel coding in moderate dimensions. While efficient lattice schemes exist in low dimensions n < 30 and high dimensions n > 1000, this is not the case of intermediate dimensions. We investigate the decoding of interesting lattices in these intermediate dimensions. We introduce new families of lattices obtained by recursively applying parity checks. These families include famous lattices, such as Barnes-Wall lattices, the Leech and Nebe lattices, as well as new parity lattices.We show that all these lattices can be efficiently decoded with an original recursive list decoder.The second problem involves neural networks. Since 2016 countless papers tried to use deep learning to solve the decoding/detection problem encountered in digital communications. We propose to investigate the complexity of the problem that neural networks should solve. We introduce a new approach to the lattice decoding problem to fit the operations performed by a neural network. This enables to better understand what a neural network can and cannot do in the scope of this problem, and get hints regarding the best architecture of the neural network. Some computer simulations validating our analysis are provided
Logiaco, Laureline. "Temporal modulation of the dynamics of neuronal networks with cognitive function : experimental evidence and theoretical analysis." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066225/document.
Full textWe investigated the putative function of the fine temporal dynamics of neuronal networks for implementing cognitive processes. First, we characterized the coding properties of spike trains recorded from the dorsal Anterior Cingulate Cortex (dACC) of monkeys. dACC is thought to trigger behavioral adaptation. We found evidence for (i) high spike count variability and (ii) temporal reliability (favored by temporal correlations) which respectively hindered and favored information transmission when monkeys were cued to switch the behavioral strategy. Also, we investigated the nature of the neuronal variability that was predictive of behavioral variability. High vs. low firing rates were not robustly associated with different behavioral responses, while deviations from a neuron-specific prototypical spike train predicted slower responses of the monkeys. These deviations could be due to increased or decreased spike count, as well as to jitters in spike times. Our results support the hypothesis of a complex spatiotemporal coding of behavioral adaptation by dACC, and suggest that dACC signals are unlikely to be decoded by a neural integrator. Second, we further investigated the impact of dACC temporal signals on the downstream decoder by developing mean-field equations to analyze network dynamics. We used an adapting single neuron model that mimics the response of cortical neurons to realistic dynamic synaptic-like currents. We approximated the time-dependent population rate for recurrent networks in an asynchronous irregular state. This constitutes an important step towards a theoretical study of the effect of temporal drives on networks which could mediate cognitive functions
Logiaco, Laureline. "Temporal modulation of the dynamics of neuronal networks with cognitive function : experimental evidence and theoretical analysis." Electronic Thesis or Diss., Paris 6, 2015. http://www.theses.fr/2015PA066225.
Full textWe investigated the putative function of the fine temporal dynamics of neuronal networks for implementing cognitive processes. First, we characterized the coding properties of spike trains recorded from the dorsal Anterior Cingulate Cortex (dACC) of monkeys. dACC is thought to trigger behavioral adaptation. We found evidence for (i) high spike count variability and (ii) temporal reliability (favored by temporal correlations) which respectively hindered and favored information transmission when monkeys were cued to switch the behavioral strategy. Also, we investigated the nature of the neuronal variability that was predictive of behavioral variability. High vs. low firing rates were not robustly associated with different behavioral responses, while deviations from a neuron-specific prototypical spike train predicted slower responses of the monkeys. These deviations could be due to increased or decreased spike count, as well as to jitters in spike times. Our results support the hypothesis of a complex spatiotemporal coding of behavioral adaptation by dACC, and suggest that dACC signals are unlikely to be decoded by a neural integrator. Second, we further investigated the impact of dACC temporal signals on the downstream decoder by developing mean-field equations to analyze network dynamics. We used an adapting single neuron model that mimics the response of cortical neurons to realistic dynamic synaptic-like currents. We approximated the time-dependent population rate for recurrent networks in an asynchronous irregular state. This constitutes an important step towards a theoretical study of the effect of temporal drives on networks which could mediate cognitive functions
François, Dominique. "Détection et identification des occlusives et fricatives au sein du système indépendant du locuteur APHODEX." Nancy 1, 1995. http://www.theses.fr/1995NAN10044.
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