A nonparametric Bayesian clustering approach to auditory perception

Models of perceptual grouping are usually using verbal, poorly accurate predictions. As of late, probabilistic models are being used more and more to create more stringent descriptions of the underlying mechanisms, and quantitative predictions. This thesis presents a nonparametric Bayesian clustering algorithm applied to Auditory Scene Analysis (ASA), along with several validations from the classical literature on the subject, and experiments using a new paradigm in different experimental settings. Grouping/segregation processes in ASA, and therefore in the model, follow similar Gestalt principles as in the more studied visual field: the more tones are similar, the more they tend to be clustered in a single auditory stream, and conversely. The first study focuses on a mathematical description of the clustering algorithm and on its validation on well-known studies from the field. A new paradigm has been used to create situations where 3 simultaneous streams could be reached by increasing the distance in frequencies between rapidly played tones, as predicted by the classical ASA model and our own. Results were in line with the hypotheses. The second study expands on the first one and uses qualitative predictions from the clustering algorithm to observe stream segregations using increasing differences in several dimensions at once in two experiments using the same paradigm: namely, frequency and spatial distance in the first one, frequency and timbre in the second one. Results presented an unexpected pattern, suggesting a stronger influence of attention as initially supposed. The third study explored the influence of attention on the stream formation process in the same paradigm, by adding specific attentional instructions to participants. Results suggest a possible limitation to 2 simultaneous attentional streams: the foreground stream, and the background one where all tones are clustered. Overall, while the model was only used to create qualitative predictions, those were useful enough to guide experiments with impactful results

Transcranial electric stimulation optimizes the balance of visual attention across space.

OBJECTIVE: Transcranial direct current stimulation (tDCS) provides a way to modulate spatial attention by enhancing the ratio of neural activity between the left and right hemispheres, with a potential benefit for the rehabilitation of visual neglect. METHODS: We tested the effect of bilateral tDCS in healthy individuals performing a visual detection task. This protocol consists in the positioning of the anode and cathode on mirror positions over the left and right parietal areas. The stimulation was repeated over three days to maximize the chance to observe a bias to the hemispace controlateral to the anode. RESULTS: Compared to a sham treatment, left anodal - right cathodal stimulation enhanced attention across the full range of space, since the first day with no build-up effect on the next days, and modified the balance of left-right omissions when stimuli appeared at the same time. CONCLUSION: Bilateral tDCS improved detection in both visual fields, with no privileged processing of one side, except when concurrent stimuli were presented. The results provide partial support to the hemispheric rivalry hypothesis. SIGNIFICANCE: The technique has the potential to boost attention in neglect patients but should be used as an adjuvant rather than as an alternative to functional rehabilitation

A non-parametric Bayesian prior for causal inference of auditory streaming.

traditionally been modeled using a mechanistic approach. The problem however is essentially one of source inference – a problem that has recently been tackled using statistical Bayesian models in visual and auditory-visual modalities. Usually the models are restricted to performing inference over just one or two possible sources, but human perceptual systems have to deal with much more complex scenarios. To characterize human perception we have developed a Bayesian inference model that allows an unlimited number of signal sources to be considered: it is general enough to allow any discrete sequential cues, from any modality. The model uses a non-parametric prior, hence increased complexity of the signal does not necessitate more parameters. The model not only determines the most likely number of sources, but also specifies the source that each signal is associated with. The model gives an excellent fit to data from an auditory stream segregation experiment in which the pitch and presentation rate of pure tones determined the perceived number of sources

LINEAR GLIDING DISCHARGE OVER DIELECTRIC SURFACES

No abstract availabl

Les différences hémisphériques de l’appréhension des quantités numériques et spatiales

Les interactions entre les capacités d’estimation numérique et spatiale ont été observées durant des décennies. La théorie ATOM propose qu’il existe des systèmes communs et spécifiques à chacune de ces capacités, ce que les observations neuro-anatomiques semblent corroborer. Cependant, les différences hémisphériques sous-tendant ces capacités d’estimation sont encore méconnues. Cette étude se propose d’étudier ces différences, en appliquant une stimulation électrique transcranienne en courant continu (tDCS) sur les deux hémisphères pendant une tâche de Stroop numérique. Les participants devaient décider quel chiffre était le plus grand parmi deux, en jugeant leur taille numérique lors d’une première tâche, puis leur taille physique lors d’une seconde. La taille des chiffres variait dans les deux modalités entre les essais quelle que soit la tâche de façon congruente ou incongruente. La stimulation tDCS était appliquée soit sur le Sulcus Intrapariétal (SIP) gauche, soit sur le SIP droit, soit il s’agissait d’une fausse stimulation (« sham »). Les résultats ont montré une légère tendance à l'amélioration de la prise en compte de la dimension spatiale lors de la tâche numérique en stimulation gauche. Cependant, les effets très modestes de la stimulation laissent entendre que la tDCS pourrait être insuffisante pour provoquer des effets dans ce type de tâche.Master [120] en sciences psychologiques, Université catholique de Louvain, 201

Etude de l'interaction d'un arc électrique de faible puissance avec une onde électromagnétique dans un écoulement d'air à pression atmosphérique

ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Etude expérimentale d'un déchargeur électrostatique pour hélicoptère

The problem of ejecting charges of one sign from an insulated body is considered. A system utilizing the condensation of the water vapor in air to form a charged aerosol has been studied in the laboratory. We have shown that, by using particular arrangements, it is possible to remove a current of 60 μA from a helicopter. The radioelectric perturbations associated with the operation of the discharger should be negligible.Le problème de l'éjection d'un courant de charges unipolaires d'un corps isolé est abordé. Un dispositif utilisant la condensation de l'humidité de l'air pour former un aérosol fortement chargé est étudié en laboratoire. On montre que, moyennant un certain nombre de dispositions, un déchargeur électrostatique capable d'évacuer d'un hélicoptère un courant de l'ordre de 60 μA est réalisable. Les perturbations radioélectriques liées au fonctionnement de l'appareil devraient être négligeables