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1
Driller, Karina. "From Cue to Construct : Cues, Mechanisms, and Stability in Haptic Perception". Electronic Thesis or Diss., Sorbonne université, 2024. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2024SORUS418.pdf.
Testo completoAbstract (sommario):
La perception haptique sert d'interface principale avec le monde physique. Sans elle, notre capacité à comprendre et à répondre à un monde rempli d'objets et de sujets serait profondément altérée. Cette thèse traite de la manière dont nous reconstruisons perceptuellement ce qui est en contact avec notre peau à partir d'entrées mécaniques pertinentes sur le plan comportemental lors des interactions haptiques. Ces informations permettent au système sensoriel d'atteindre ses objectifs, dont l'exploration et la manipulation fine des objets. Après une introduction (Chapitre 1) couvrant les concepts liés à l'émergence des percepts haptiques stables, la thèse présente une série d'études expérimentales visant à découvrir les indices et mécanismes utilisés pour reconstruire différentes interactions haptiques. Comme les interactions haptiques commencent par la détection du contact, le Chapitre 2 identifie quelles informations le système sensoriel utilise pour détecter ce contact. Cette première partie révèle un métamère d'intensité pour le codage des événements d'impact et suggère que l'énergie transférée (le travail mécanique) est un indice important, mais pas le seul facteur dans la décomposition perceptuelle des interactions peau-objet. L'accent passe ensuite à des interactions plus complexes. Comme les indices de texture et de matériau sont cruciaux pour la préhension et le glissement, une attention particulière est accordée à la perception haptique de la rugosité et de la compliance, couvrant trois chapitres. Compte tenu de la complexité de cette perception, le Chapitre 3 explore comment capturer cette complexité sans compromettre le contrôle expérimental, via le développement d'une base de données de stimuli bien caractérisés. Dans le Chapitre 4, l'expérience explore ensuite la contribution des ondes de propagation vibratoires en éliminant les informations cutanées via une anesthésie du doigt. Nous identifions les ondes comme un indice pertinent pour la perception de la rugosité pour certains, mais pas tous. La douceur perçue est, elle, fortement réduite sans informations tactiles locales. Le Chapitre 5 explore l'influence combinée des caractéristiques de surface et de l'élasticité dans la perception de la rugosité et de la douceur, mettant en lumière une confusion perceptuelle dans la reconstruction de la rugosité. Le travail révèle des métamères de rugosité, des zones où différentes combinaisons d'indices mènent à des perceptions identiques. Le dernier chapitre (Chapitre 6) explore les conséquences du timing perçu lors des interactions haptiques lorsque les indices tactiles locaux sont supprimés. Une tâche de liaison temporelle est utilisée pour éclairer le rôle des indices cutanés dans l'estimation du temps d'interaction peau-bouton. Ensemble, ces travaux soulignent l'importance de bien déterminer les contributions des indices et mécanismes physiques, mécaniques, neuronaux et perceptuels pour comprendre la reconstruction du monde tactileHaptic perception serves as our primary interface to the physical world. Without it, our ability to understand and respond to a world full of objects and subjects would be profoundly impaired. This dissertation addresses the problem of how we perceptually reconstruct what is in contact with our skin from behaviorally-relevant mechanical inputs during haptic interactions. Behaviorally-relevant information is defined as the kind of information that allows the sensory system to achieve its goals, and a primary goal of the somatosensory system is to enable the exploration and dexterous manipulation of objects.Following an introduction (Chapter 1), which covers fundamental concepts related to the emergence of stable haptic percepts, the dissertation comprises a series of experimental studies aimed at uncovering the essential cues and mechanisms used to perceptually reconstruct different haptic interactions. Because most haptic interactions start with the detection of contact, the first challenge taken in Chapter 2 is to identify what information the sensory system uses to detect the onset of skin contact during basic impact events. This first part of the dissertation uncovers a basic intensity metamer in the encoding of impact events and suggests the total amount of energy transferred by a force (i.e., the mechanical work) as an important cue, but not the sole determinant in the perceptual decomposition of haptic skin-object interactions.The focus then moves towards more complex everyday-like skin-object interactions. Because texture and material cues are critical to grasp and sliding behavior, special emphasis is placed on haptic texture and material perception (i.e., roughness and compliance perception), spanning three full chapters of this dissertation. Given the high-dimensional nature of haptic material and texture perception, Chapter 3 first explores how we can capture the complexity of haptic interactions with naturalistic surfaces without compromising on the experimental control needed to link specific cues to perceptual phenomena. This problem is addressed via the development of a dual-property stimulus database containing well-characterized stimuli which resemble the statistics of naturally occurring rough and compliant surfaces.In a following experiment, Chapter 4 then explores the contribution of vibratory propagation waves in perceptually reconstructing these surfaces by eliminating cutaneous information using local anesthesia of the index finger. We identify propagation waves as a behaviorally-relevant and sufficient cue for roughness perception for some, but not all participants. The perceived softness of these surfaces, on the other hand, is strongly diminished when local tactile information is removed. Subsequently, Chapter 5 explores the combined influence of surface features and material elasticity in mediating roughness and softness perception and highlights a perceptual confound in the reconstruction of surface roughness. The work uncovers roughness metamers, that is, regions where different cue combinations lead to identical perceptual outcomes.The final empirical chapter of this dissertation (Chapter 6) uncovers the consequence of the perceived timing of dynamic haptic interactions when behaviorally-relevant local tactile cues are removed. A temporal-binding task is used to illuminate the role of cutaneous cues in estimating the time course of mechanical skin-button interaction.Together, the work presented in this dissertation highlights the importance of correctly determining the contributions of physical, mechanical, neural, and perceptual-level cues and mechanisms in understanding the reconstruction of our world of touch
2
Jones, Peter R. "Mechanisms of auditory perceptual learning". Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13376/.
Testo completoAbstract (sommario):
Practice improves performance on many basic auditory tasks. However, while the phenomenon of auditory perceptual learning is well established, little is known about the mechanisms underlying such improvements. What is learned during auditory perceptual learning? This thesis attempts to answer this question by applying models of performance to behavioural response data, and examining which parameters change with practice. On a simple pure tone discrimination task, learning is shown to primarily represent a reduction in internal noise, with encoding efficiency, attentiveness and bias appearing invariant. In a more complex auditory detection task, learning and development are also shown to involve improvements in listening strategy, with listeners becoming better able to selectively-attend to task-relevant information. Finally, task performance is potentially constrained not just by the strength of the sensory evidence, but also by the efficiency of the wider decision process that the sensory evidence informs. Thus, in the final chapters learning is also shown to involve reductions in both stationary and nonstationary bias. In short, learning is shown to be subserved by multiple mechanisms that: operate in parallel, vary in importance depending on the task demands, and incorporate both sensory and non-sensory processes. The methods of analysis described herein are shown to effectively partition components of perception in normal hearing children and adults, and may help to understand learning processes needed for the rehabilitation of listening difficulties.
3
Hancock, Sarah. "Perceptual mechanisms underlying binocular rivalry". Thesis, University of York, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437581.
Testo completo
4
Seaborn, Matthew. "Colour content based image retrieval using spatial and perceptual cues". Thesis, Brunel University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342391.
Testo completo
5
Al-Dossari, Munira. "Biases and mechanisms in perceptual memory". Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/12208.
Testo completoAbstract (sommario):
Intermittent presentation of an ambiguous visual stimulus leads to a memory effect in which the percept on one presentation is usually the same as on the previous presentation. This effect is a form of perceptual memory. The aim of this research was to compare and examine the different explanations of biases in this form of perceptual memory. The mechanism of the stabilisation of ambiguous perception during intermittent presentation of ambiguous stimuli was also investigated. The Participants were adult humans who voluntarily participated in the experiments. An ambiguous percept was created using binocular rivalry: most of the rivalry stimuli consisted of a grating to one eye and an orthogonal grating to the other eye. In order to measure biases in perceptual memory, ambiguous stimuli were presented intermittently with varying monocular contrasts. To investigate the mechanism of perceptual memory, brief monocular test stimuli were presented in the intervals between the rivalry stimuli, and the threshold response to the test stimuli was measured. Psychometric functions of monocular contrast predominance thresholds are used throughout this thesis. To start with, a new method of measuring the psychometric function is described. On each trial the stimulus contrast was sampled from a Gaussian probability density, and the reported percept on each trial was binned to calculate the psychometric function. This method has the advantage over conventional techniques, such as the method of constant stimuli, that this method reduces the potentially confounding factors such as adaptation. Furthermore, this method appears to be effective in concentrating the trials around the threshold region of the curve where usually there is less stimulus certainty allowing the achievement of a cleaner estimation of the slope. There were four following main results: First, a chronic bias towards the right-eye was established which was not stimulus specific rather eye specific. The probability of a right-eye percept was calculated as a function of right-eye contrast, with the sum of the two monocular contrasts equal to 1. This psychometric function was not centred over a contrast of 0.5. Instead the probability of seeing a right-eye percept was greater than 0.5 at this contrast, meaning that there was a chronic bias towards the right-eye stimulus. This bias persisted when the orientations were swapped between eyes, meaning that it was eye- rather than stimulus-specific. Second, there was a substantial variation in the strength of the bias among participants. This was demonstrated by analysing the same psychometric functions according to the perceptual history. The level of function was found more convincing when consecutive percepts were identical in comparison with that when the percepts were different. This percept-induced bias is the well-known perceptual stabilisation effect, the main focus of this thesis. The strength of the bias was measured as the lateral shift between the two psychometric functions. Surprisingly, the bias differed substantially between Participants; for the standard participant cohort the range was 0 – 0.28 contrast units with a mean of 0.11. Third, a comparison between psychometric functions resulted in response to intermittent rivalry and continuous rivalry demonstrated that there was a greater influence of noisy neural processes during intermittent rivalry and the intermittent rivalry produced a stronger chronic bias towards the right eye when compared with that of the continuous rivalry. This conclusion was reached by measuring psychometric functions during intermittent rivalry and continuous rivalry and by making a comparative analysis of the results. The contrast of both monocular stimuli varied such that they always summed to 1, and the rivalry stimuli were viewed continuously. The slope of the psychometric functions was about half of that obtained during intermittent rivalry, indicating a greater influence of noisy neural processes. The chronic bias was towards the right eye, as before, but weaker than for intermittent rivalry. Fourth, it was demonstrated that the threshold for discriminating the test stimulus was lower for the match case than for mismatch, but the reduction was only statistically significant when the participant’s percept-induced bias was taken into account. To demonstrate this mechanism of perceptual stabilisation was investigated by using intermittently presented rivalry stimuli, and inserting a brief monocular test stimulus into the intervals between rivalry stimuli. The spatial form of the test stimulus matched that of the right-eye rivalry stimulus, and the form of the test stimulus therefore matched or mismatched the rivalry percept. In conclusion, this research has established a new and more effective method of measuring psychometric functions which provides a better picture of the responses as well as a robust measure of the threshold. It has been further demonstrated that in response to intermittently presented ambiguous stimuli a chronic bias towards the right eye and a temporary bias in the direction of the previous percept are established in perceptual memory. Similarly, a bias towards the right eye is also demonstrated when the stimulus is presented continuously. Furthermore, the research has helped to improve our understanding of the mechanisms of perceptual memory by demonstrating the establishment of a relatively weak, but statistically significant threshold due to the effects of percept.
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Housley, Meghan K. "The Positivity-Cues-Familiarity Effect and Initial Stimulus Valence". Miami University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=miami1185554049.
Testo completo
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Hamaoui, Kamil. "The perceptual grouping of musical sequences : pitch and timing as competing cues /". Diss., Connect to a 24 p. preview or request complete full text in PDF formate. Access restricted to UC IP addresses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3236630.
Testo completo
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Simon, Laurent. "Development of multichannel recording and reproduction techniques based on auditory perceptual cues". Thesis, University of Surrey, 2011. http://epubs.surrey.ac.uk/844355/.
Testo completoAbstract (sommario):
In order to capture and reproduce sound all around the listener in a perceptually realistic way, a recording technique (microphone layout) and a reproduction system (loudspeaker layout) capable of accurate 360° imaging are required. In order to develop the reproduction system, binaural and loudspeaker-based localisation cues were investigated in a literature review. The necessary loudspeaker-based localisation cues to manipulate the location of a sound image were analysed, and these showed that the common 5.1 surround sound loudspeaker arrangement could produce stable images to the front of the listener but not to the side. An 8-channel loudspeaker configuration arranged as a regular octagon was therefore chosen based on attempting to recreate plausible interaural cues for all locations. The performance of this was compared to a 5.1 loudspeaker system in terms of localisation accuracy. It was shown that the octagonal loudspeaker configuration produces more stable and more accurate images all around the listener. The octagonal loudspeaker arrangement required new microphone techniques for optimum recording and reproduction. An overview of the current literature showed how localisation curves can be used to design microphone arrays, and the other physical and perceptual parameters that need to be considered in microphone array design. This showed that it is useful to derive localisation curves for the new loudspeaker configuration, as these can be used to optimise the microphone array's sound imaging accuracy. An experiment was therefore conducted to measure the localisation curves, and it showed that localisation curves are different for the loudspeaker pairs to the front, side or the rear of the listener. It also showed that to the side of the listener, interchannel time differences have little influence on the perceived location of the sound event. The derivation of these localisation curves enabled the development of a microphone array design tool that predicts the localisation profile of a microphone array as a function of its geometrical set-up and the directivities of the microphones. The predictions of this tool were evaluated by comparing sound image positions for recordings of ten sound sources with ten different microphone arrays. This showed that the error of prediction is small when the crosstalk due to the microphone array is low. A linear regression model was created and shown to reasonably model the error of prediction as a function of the crosstalk level and crosstalk delay.
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Kwok, Rebecca Martha. "Visual mechanisms subserving perceptual judgement and action". Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408703.
Testo completo
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Wang, Xueying. "Mechanisms of Simple Perceptual Decision Making Processes". The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1249662470.
Testo completo
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Wong, King-yu Natalie. "The effect of contextual cues on the perceptual normalization of Cantonese level tones". Click to view the E-thesis via HKUTO, 2001. http://sunzi.lib.hku.hk/hkuto/record/B36208097.
Testo completoAbstract (sommario):
Thesis (B.Sc)--University of Hong Kong, 2001."A dissertation submitted in partial fulfilment of the requirements for the Bachelor of Science (Speech and Hearing Sciences), The University of Hong Kong, May 4, 2001." Also available in print.
12
Blanc-Goldhammer, Daryn. "The Neural and Perceptual Mechanisms Underlying Spatial Integration". Thesis, University of Oregon, 2019. http://hdl.handle.net/1794/24536.
Testo completoAbstract (sommario):
The visual system integrates information over space to see surfaces, contours and edges. This integration can be described by a divisive normalization framework in which surrounding contextual information normalizes response to a central target. We ran a set of studies examining perceptual illusions with the intention of better understanding the neural mechanisms responsible for how the visual system integrates information over space. We measured surround integration using the Simultaneous Tilt Illusion. In the first study, we determined the extent to which the probability that different surround regions were co-assigned to the same object as the center impacts how much they are integrated. We found that the magnitude of the illusion was a sum of regional surround effects weighted by their dependency to the center. These results are consistent with a system that uses prior experience with natural scene statistics to integrate regions of space. In the second study, we measured the relationship between individual differences in spatial integration and autistic traits. We found no evidence for reduced normalization in people who score high on autistic traits. In the third study, we determined the extent to which arousal modulates spatial integration. Although we did not observe an effect of natural fluctuations in arousal, as indexed by pupil diameter, we observed a reduction in the magnitude of the illusion following an alerting tone. While more work is still needed to verify this effect, it suggests that we context information less under moderately alert states. We interpret these results in the context of the neural and perceptual mechanisms underlying spatial integration. Specifically, these results seem to indicate that the normalization process is gated by our expectancies about the structure of a scene and by our internal brain state. These results are consistent with a system that uses prior experience with scene statistics to represent patterns more efficiently.
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Bray, Jodi Patrice. "Understanding sonority an acoustic analysis of perceptual cues in English and Russian consonant clusters". [Gainesville, Fla.] : University of Florida, 2001. http://purl.fcla.edu/fcla/etd/UFE0000306.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Florida, 2001.Title from title page of source document. Document formatted into pages; contains xxviii, 236 p.; also contains graphics. Includes vita. Includes bibliographical references.
14
Ikeno, Ayako. "Perceptual cues in English accent variation: The role of prosody and listener accent background". Diss., Connect to online resource, 2005. http://wwwlib.umi.com/cr/colorado/fullcit?p3190392.
Testo completo
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Marples, Daryl. "The influence of intrinsic perceptual cues on navigation and route selection in virtual environments". Thesis, University of Huddersfield, 2017. http://eprints.hud.ac.uk/id/eprint/34448/.
Testo completoAbstract (sommario):
The principle aims of this thesis were to investigate the influence of intrinsic navigational cues in virtual environments and video games. Modern video games offer complex environments that may reflect real world spaces or represent landscapes from fantasy and fiction. The coherent design of these spaces can promote natural navigational flow without the requirement for extraneous guidance such as maps and arrows. The methods that designers use to create natural flow are complex and stratified utilising principles rooted in urban architectural design and navigational cues that are intrinsic to real-world wayfinding scenarios. The studies presented in this thesis analysed not only these commonly used architectural cues but also the potential for the reinforcing of these cues by the addition of lighting, visual and auditory cues. The primary focus of this thesis was a systematic and quantitatively rooted analysis of the impact lighting has on navigation and the levels at which variance in lighting makes a quantifiable difference to navigational choices within a virtual environment. The findings of this thesis offer clear guidance as to the influence that lighting has within virtual environments and specifies that thresholds at which the inclusion of guidance lighting begins to affect navigational choices and the levels that players become conscious of these cues. The thesis also analyses the temporal thresholds for the detection of changes in contrast, hue and texture within an environment. The relationship of other intrinsic cues such as the potential reinforcement or cue competition effects of both audio and other visual cues, for instance motion are quantitatively analysed. These data were reflected in the form of a series of heuristic design principles that augment those that underpin architectural and environmental design considerations by for instance suggesting levels of saliency for lighting cues or reinforcing existing cues via supporting audio guidance.
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El, Zein Marwa. "Neural mechanisms of contextual influences during social perceptual decisions". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066436/document.
Testo completoAbstract (sommario):
Les décisions que nous prenons au quotidien nécessitent le traitement de plusieurs sources d'information, et dépendent par conséquent de nombreux éléments contextuels tels que les indices sociaux provenant d'un émetteur ainsi que le centre de l'attention, l'humeur et l'expérience passée de l'observateur. Le travail réalisé durant cette thèse a eu pour but de caractériser les mécanismes cognitifs et neuraux sous-tendant l'impact de ces éléments contextuels sur la prise de décision dans un environnement social. La première étude d'électroencéphalographie (EEG) a manipulé l'attention de l'observateur lors du traitement des indices sociaux. Grâce à des analyses comportementales et EEG basées sur la modélisation, la seconde étude a caractérisé les mécanismes qui sous-tendent l'intégration des indices sociaux extraits d'un visage et l'influence de l'anxiété sur cette intégration. Enfin, en conjuguant modélisation et enregistrements pupillaires, la troisième étude a caractérisé l'influence de l'expérience apriori sur la perception de l'émotion. Alors que les indices sociaux émis simultanément interagissent en renforçant le traitement ascendant 'bottom-up' des signaux pertinents de menace, l'expérience apriori agit comme un facteur contextuel descendant 'top-down' qui biaise les décisions vers les options attendues, tandis que l'attention et les caractéristiques de l'observateur modulent la contribution relative de régions pertinentes dans le traitement de stimuli sociaux. Les résultats mettent en lumière les différents mécanismes cognitifs qui sous-tendent l'influence de facteurs contextuels distincts lors de la prise de décision perceptive dans un environnement socialEveryday social decisions require the combination of multiple sources of information and therefore build upon abundant contextual elements such as the social cues of emitters (e.g., gaze direction, emotion, gesture), the attentional focus of observers, their mood and their past experience. The work conducted during this Ph.D. (including three main studies in healthy human subjects) aimed at characterizing the cognitive and neural mechanisms of contextual influences in social settings. The first Electroencephalography (EEG) study manipulated the attentional focus of participants while they processed social signals. Using model-based behavioral and single-trial EEG analyses, the second study aimed at characterizing the mechanisms underlying the integration of multiple social cues from faces and the role of anxiety in this integration,. Finally, the third study used model-based behavioral and pupillometric analyses to investigate the mechanisms by which prior experience with individual identities influences the perception of their emotion. While co-emitted social cues interact by boosting bottom-up processing of relevant threat signals within 200 ms after stimulus onset, prior experience enacts as a top-down contextual factor biasing decisions toward expected options, and attention and individual traits (anxiety) modulate the relative contribution to social processing of relevant neural regions. Altogether, these findings shed light on the distinct cognitive mechanisms underlying the influence of different contextual factors during perceptual decisions in social settings
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López, Pigozzi Diego. "Brain mechanisms underlying the tracking and localization of dynamic cues". Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/112125.
Testo completoAbstract (sommario):
Since the discovery of the place cells in 1971 by John O’Keefe and colleagues an extensive work over the hippocampus has been developed as the mammal model of spatial navigation. Place cells are rodents’ hippocampal neurons whose firing is associated to certain locations of the environment. A majority of studies have focused on how the place fields (the area where the firing of a neuron is restricted) are generated in relation to the static cues of the environment (O'Keefe and Conway, 1978; Muller et al., 1987; Gothard et al., 1996). The present work assessed a similar question but regarding the dynamic cues surrounding the subject, and with the hypothesis that the hippocampus is also representing the position of other moving objects. In order to demonstrate if that was the case, we developed a behavioural protocol in which rats learnt to discriminate the movements of a robot in order to obtain reward, an Operant Position Discrimination Task (OPDT). Once the protocol was validated, the subjects were chronically implanted with tetrodes in the CA1 region of the hippocampus. In this way the activity of single hippocampal cells could be isolated off-line and the LFP of the area stored during the recordings. Using this method, the relationship between the firing of the cells and the field activity with the spatial parameters of the robot could be evaluated.
The results showed a modulation by the dynamic cue of the theta oscillation. While the locomotor activity of the subjects is directly related to the power of theta in natural conditions (Vanderwolf, 1969), during the movement of the robot such relationship was disrupted and the band power between 4-12 Hz showed a trough at this time.
The analysis of the single cells’ activity showed neurons locked to several spatial features of the dynamic cue. First, the position of the rat and the robot where analysed by information content parameters. Skaggs Index and Positional information (Markus et al., 1994; Olypher et al., 2003) showed neurons locked to the position of the subject as expected in CA1 and also other neurons locked to the positions of the robot. Second, moving from the spatial analysis to the temporal one, we found responses to the movement of the robot like OFF/ON variations of the basal activity of the neurons. Such changes in the firing patterns where quantified by the Mutual Information index (Nelken and Chechik, 2007) demonstrating that a large fraction of the neurons have a significant differential pattern of activity during the movement of the robot towards one side or the other. The use of the same index, MI, for the evaluation of the static or dynamic condition of the robot, also resulted in a set of neurons spiking with significant disparity during such epochs.
In conclusion, the present work has demonstrated the existence of neural correlates locked to a dynamic cue in the hippocampus. Both the field activity at the theta range, LFP between 4 and 12 Hz, and the activity of the hippocampal neurons were found to reflect and/or encode the spatial features of a dynamic cue. The present work has in this way enlarged the limited evidence present in the prior literature about the role of the hippocampus in the tracking and localization of dynamic cues with the use of a behavioural protocol where both the spatial and temporal dynamics could be assessed.La correcta localización y seguimiento de las pistas dinámicas que se encuentran en el ambiente es una tarea crucial para el individuo. Comportamientos fundamentales como la caza, el apareamiento o el escape necesitan una correcta identificación de la posición de presas, congéneres y depredadores para su correcta realización. El sistema cerebral encargado de localizar al propio sujeto en el ambiente se sabe que se encuentra en la formación hipocampal después de que diversos estudios hayan demostrado la necesidad del mismo para una correcta orientación (Morris et al., 1982) y, aún más importante, tras el descubrimiento en roedores de neuronas que disparan únicamente en espacios restringidos del entorno, las células de lugar (O'Keefe and Dostrovsky, 1971). Si bien se conoce que estos procesos están fundados en una correcta representación de la posición de las pistas estáticas del ambiente (O'Keefe and Conway, 1978; Muller et al., 1987; Gothard et al., 1996), que sirven de referencia para la propia localización, poco se sabe acerca de cómo se integra la información relativa a los objetos y/o sujetos móviles que se encuentran en el mismo ambiente. Este trabajo tiene como objetivo principal intentar responder a esta pregunta, es decir, ¿en qué modo el hipocampo procesa la información relativa a las pistas dinámicas? Para el desarrollo del estudio, primero, se diseñó una tarea comportamental que asegurara el hecho de que la pista dinámica resultase relevante para los sujetos de forma que los mismos prestaran atención a sus movimientos. Con este fin elegimos utilizar un robot cuyos desplazamientos pueden ser finamente controlados y asociar una recompensa a determinados patrones de navegación del robot. Después de probar con diferentes tareas de discriminación se llegó a una configuración (Operant Position Discrimination Task, OPDT) que permitía a los animales seguir los movimientos del robot desde un espacio separado en el cual recibían la recompensa en caso de discernir correctamente los desplazamientos de la pista. Una vez validada la tarea comportamental, a los sujetos que alcanzaron altas tasas de rendimiento se les implantaron tetrodos en la zona CA1 del hipocampo, lugar en el que se encuentran las células de lugar más estables. Una vez hecho el implante se procedió a registrar la actividad cerebral durante la ejecución de la tarea. Por una parte se aislaron los potenciales de acción pertenecientes a neuronas únicas y el potencial de campo de la zona, LFP. Respecto a la actividad de campo, LFP, se observó una disminución significativa de la potencia en la banda theta, 4-12 Hz, relacionada generalmente con la actividad locomotora del sujeto (Vanderwolf, 1969) durante el movimiento del robot. Durante el resto del registro la relación entre velocidad y potencia de theta se mantuvo y sólo en el periodo de discriminación del movimiento del robot esta relación se vio alterada con un mínimo de potencia observado en diferentes sujetos y registros. La actividad de las neuronas se analizó en función de los parámetros espaciales y dinámicos de la rata y el robot. Mirando la especificidad espacial del disparo de las neuronas a través de los parámetros Skaggs Index y Positional information (Markus et al., 1994; Olypher et al., 2003) se encontraron células significativamente ligadas en su actividad a la posición del sujeto o del robot. La actividad de las neuronas también se analizó de forma temporal, tomando como referencia el inicio de los estímulos, es decir el movimiento del robot hacia un lado u otro. Utilizando como índice la Mutual Information (Nelken and Chechik, 2007) se encontró que una larga proporción de las neuronas tienen respuestas diferenciales durante el movimiento del robot hacia uno de los lados. A su vez, el mismo análisis, pero en esta ocasión comparando los periodos en los que la pista se encuentra inmóvil con los que está en movimiento, determinó que otra fracción de las neuronas tiene patrones de disparo diferenciales según sea la condición dinámica de la pista. El conjunto de los resultados obtenidos indica claramente que el hipocampo se encuentra involucrado activamente en la localización y el seguimiento de las pistas dinámicas, siendo esto reflejado tanto en la actividad de sus neuronas como en la actividad de campo global. Los parámetros espaciales de la pista que resultaron modulados durante la tarea fueron su posición, la dirección de su movimiento y el hecho en sí de permanecer inmóvil o en desplazamiento.
18
Hodgson, Eric P. "The interaction of transient and enduring spatial representations using visual cues to maintain perceptual engagement /". Oxford, Ohio : Miami University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1217959226.
Testo completo
19
Maguire, Rachael. "Acquisition and maintenance of keyboard skills". Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/926/.
Testo completo
20
Pun, Kwok Cheung. "New directions in image modelling based on human perceptual mechanisms". Thesis, Heriot-Watt University, 1995. http://hdl.handle.net/10399/1329.
Testo completo
21
Batson, Melissa Anne. "Task-irrelevant perceptual learning of crossmodal links: specificity and mechanisms". Thesis, Boston University, 2010. https://hdl.handle.net/2144/42191.
Testo completoAbstract (sommario):
It is clear that in order to perceive the external environment in its entirety, inputs from multiple sensory systems (i.e. modalities) must be combined with regard to each object in the environment. Humans are highly vision-dependent creatures, with a large portion of the human cortex dedicated to visual perception and many multimodal areas proposed to integrate vision with other modalities. Recent studies of multimodal integration have shown crossmodal facilitation (increased performance at short stimulus onset asynchronies, SOA s) and/or inhibition of return ( IOR ; decreased performance at long SOAs) for detection of a target stimulus in one modality following a location-specific cue in a different modality. It has also been shown that unimodal systems maintain some level of plasticity through adulthood, as revealed through studies of sensory deprivation (i.e. unimodal areas respond to multimodal stimuli), and especially through perceptual learning ( PL )--a well-defined type of cortical plasticity. Few studies have attempted to investigate the specificity and plasticity of crossmodal effects or the contexts in which multimodal processing is necessary for accurate visual perception. This dissertation addresses these unanswered questions of audiovisual ( AV ) crossmodal cuing effects by combining findings from unimodal perceptual learning with those of multimodal cuing effects as follows: (1) the short- and long-term effects of audiovisual crossmodal cuing, as well as the plasticity of these effects were systematically examined using spatially specific audiovisual training to manipulate crossmodal associations using perceptual learning; (2) neural correlates of these plastic crossmodal effects were deduced using monocular viewing tests (discriminating simple and complex stimuli) following monocular and orientation specific crossmodal perceptual training; and (3) psychophysical boundaries of plasticity within and among these mechanisms as dependent on task/training type and difficulty were determined by varying stimulus salience and looking at post-PL changes in response operating characteristics.
22
Austin, Alison J. "Mechanisms of attention for cues associated with rewarding and aversive outcomes". Thesis, University of Sussex, 2010. http://sro.sussex.ac.uk/id/eprint/6265/.
Testo completoAbstract (sommario):
Attentional biases arising from classical conditioning processes may contribute to the maintenance of drug addictions and anxiety disorders. This thesis examined whether attentional mechanisms for conditioned stimuli (CS) would be dominated by affective properties (Lang, Greenwald, Bradley, & Hamm, 1993), or the uncertainty of the stimulus in predicting the outcome (Pearce & Hall, 1980). In chapter one affective and uncertainty-driven mechanisms of attention are discussed in relation to rewarding and aversive outcomes. In experimental chapter 2 methodological issues are addressed. In experimental chapters three and four attentional mechanisms are tested using a discriminative conditioning procedure with visual stimuli of varying predictive certainty (CS+,CS+/-,CS-) for a monetary or noise outcome (US). Attention was measured using an eye-tracker, and emotional conditioning and learning were measured using Likert scales. It was found that attention was mediated by uncertainty (chapter 3), but increasing the intensity of the outcome switched attention to affective-driven mechanisms for the noise outcome (chapter 4). In a further experiment this effect on attention remained for the noise outcome even under conditions promoting uncertainty-driven mechanisms (chapter 6). When cigarettes were the unconditioned stimuli instead of money in the appetitive conditioning, attention was also mediated by stimulus affect (chapter 5). In chapter 7 the data are discussed and it is concluded that when the outcome is highly emotionally salient, affective-driven mechanisms of attention dominate over uncertainty.
23
Lavis, Yvonna Marie Psychology Faculty of Science UNSW. "An investigation of the mechanisms responsible for perceptual learning in humans". Publisher:University of New South Wales. Psychology, 2008. http://handle.unsw.edu.au/1959.4/42882.
Testo completoAbstract (sommario):
Discrimination between similar stimuli is enhanced more by intermixed pre-exposure than by blocked pre-exposure to those stimuli. The salience modulation account of this intermixed-blocked effect proposes that the unique elements of intermixed stimuli are more salient than those of blocked stimuli. The inhibition account proposes that inhibitory links between the unique elements of intermixed stimuli enhance discrimination. The current thesis evaluated the two accounts in their ability to explain this effect in humans. In Experiments 1 and 2, categorisation and same-different judgements were more accurate for intermixed than for blocked stimuli. This indicates that intermixed pre-exposure decreases generalisation and increases discriminability more than does blocked pre-exposure. In Experiments 3 ?? 5, same-different judgements were more accurate when at least one of the two stimuli was intermixed. This enhanced discrimination was not confined to two stimuli that had been directly intermixed. These results are better explained by salience modulation than by inhibition. Experiments 6 ?? 8 employed dot probe tasks, in which a grid stimulus was followed immediately by a probe. Neither intermixed nor blocked stimuli showed facilitated reaction times when the probe appeared in the location of the unique element. In Experiments 9 ?? 11 participants learned to categorise the intermixed unique elements more successfully than the blocked unique elements, but only when the unique elements were presented on a novel background during categorisation. Experiments 6 ?? 11 provide weak evidence that the intermixed unique elements are more salient than their blocked counterparts. In Experiment 12, participants were presented with the shape and location of a given unique element, and were required to select the correct colour. Performance was more accurate for intermixed than for blocked unique elements. In Experiment 13, participants learned to categorise intermixed, blocked and novel unique elements. Performance was better for intermixed than for blocked and novel unique elements, which did not differ. None of the proposed mechanisms for salience modulation anticipate these results. The intermixed-blocked effect in human perceptual learning is better explained by salience modulation than by inhibition. However, the salience modulation accounts that have been proposed received little support. An alternative account of salience modulation is considered.
24
Minini, Loredana. "An exploration of visuomotor and perceptual mechanisms in humans and rats". Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1444844/.
Testo completoAbstract (sommario):
Neuropsychological, neurophysiological and psychophysical evidence support the notion of two separate and largely independent cortical visual systems: a dorsal system mediating visually guided action and a ventral system mediating object perception and recognition (Goodale & Milner, 1992). This thesis is divided into three parts that explore questions related to the two-visual-systems model, two in humans and one in rats. The first part explores whether dorsal representations are based on the veridical properties of the stimuli or whether they include information produced by filling-in mechanisms of cortical visual areas. All human experiments were carried out with the ELITE and SMART motion tracking systems. Kinematic analysis showed that grasping Kanizsa illusory squares and partly-occluded objects was as accurate as grasping luminance-defined targets and it is concluded that information about interpolated regions is available to the dorsal system for the calibration of the movement parameters. A Vernier acuity task confirmed that the perceptual localization of Kanizsa and luminance-defined contours is not equally accurate in the ventral visual system. The second part explores the effect of target dimensionality on grasping, focusing on the possibility that actions aimed at targets that contain two-dimensional information could be modulated by ventral visual mechanisms. The Diagonal Illusion (DI) was chosen to investigate this possibility because it is entirely the product of three- dimensional objects. The DI exerted an effect on both perception and action, although the latter was smaller, suggesting that the effects of illusions on action previously reported are not attributable to the presence of 2D information and, by implication, that 2D information in the target array does not elicit modulation by the ventral visual system. These conclusions were confirmed by a study that found similar kinematic profiles from grasps aimed at 3D, 2D and 2D-enhanced targets. Control studies ruled out potential confounding effects resulting from curvatures of the stimuli that could have acted as obstacles and from differences in haptic feedback. It is concluded that object-directed action is mediated by dorsal visual mechanisms, irrespective of target dimensionality. The third part seeks to find evidence of ventral visual processing in rats by measuring the perception of visual illusions and object recognition in this species. The aim is to establish whether rats could provide a suitable model to further investigate the dorsal and ventral visual systems. An automated apparatus with a touch-screen and computer generated stimuli was developed to train the animals. The results from the illusion studies are not conclusive as only one out of three groups of rats was able to solve a discrimination with Kanizsa illusory figures. The preliminary results from the object recognition studies are however clearer. Rats were able to use aspect ratio to solve a discrimination with stimuli that varied in size and location suggesting that size- and location-independent object recognition occurs in this species. Probe trials confirmed these results. It is concluded that rats may have visual processes comparable to those occurring in the ventral visual system of humans and primates.
25
Borrie, Stephanie Anna. "Perceptual learning of dysarthric speech". Thesis, University of Canterbury. Department of Communication Disorders, 2011. http://hdl.handle.net/10092/5480.
Testo completoAbstract (sommario):
Perceptual learning, when applied to speech, describes experience-evoked adjustments to the cognitive-perceptual processes required for recognising spoken language. It provides the theoretical basis for improved understanding of a speech signal that is initially difficult to perceive. Reduced intelligibility is a frequent and debilitating symptom of dysarthria, a speech disorder associated with neurological disease or injury. The current thesis investigated perceptual learning of dysarthric speech, by jointly considering intelligibility improvements and associated learning mechanisms for listeners familiarised with the neurologically degraded signal. Moderate hypokinetic dysarthria was employed as the test case in the three phases of this programme of research.
The initial research phase established strong empirical evidence of improved recognition of dysarthric speech following a familiarisation experience. Sixty normal hearing listeners were randomly assigned to one of three groups and familiarised with passage readings under the following conditions: (1) neurologically intact speech (control) (n = 20), dysarthric speech (passive familiarisation) (n = 20), and (3) dysarthric speech coupled with written information (explicit familiarisation) (n = 20). Subsequent phrase transcription analysis revealed that the intelligibility scores of both groups familiarised with dysarthric speech were significantly higher than those of the control group. Furthermore, performance gains were superior, in both size and longevity, when the familiarisation conditions were explicit. A condition discrepancy in segmentation strategies, in which attention towards syllabic stress contrast cues increased following explicit familiarisation but decreased following passive familiarisation, indicated that performance differences were more than simply magnitude of benefit. Thus, it was speculated that the learning that occurred with passive familiarisation may be qualitatively different to that which occurred with explicit familiarisation.
The second phase of the research programme followed up on the initial findings and examined whether the key variable behind the use of particular segmentation strategies was simply the presence or absence of written information during familiarisation. Forty normal hearing listeners were randomly assigned to one of two groups and were familiarised with experimental phrases under either passive (n = 20) or explicit (n = 20) learning conditions. Subsequent phrase transcription analysis revealed that regardless of condition, all listeners utilised syllabic stress contrast cues to segment speech following familiarisation with phrases that emphasised this prosodic perception cue. Furthermore, the study revealed that, in addition to familiarisation condition, intelligibility gains were dependent on the type of the familiarisation stimuli employed. Taken together, the first two research phases demonstrated that perceptual learning of dysarthric speech is influenced by the information afforded within the familiarisation procedure.
The final research phase examined the role of indexical information in perceptual learning of dysarthric speech. Forty normal hearing listeners were randomly assigned to one of two groups and were familiarised with dysarthric speech via a training task that emphasised either the linguistic (word identification) (n = 20) or indexical (speaker identification) (n = 20) properties of the signal. Intelligibility gains for listeners trained to identify indexical information paralleled those achieved by listeners trained to identify linguistic information. Similarly, underlying error patterns were also comparable between the two training groups. Thus, phase three revealed that both indexical and linguistic features of the dysarthric signal are learnable, and can be used to promote subsequent processing of dysarthric speech.
In summary, this thesis has demonstrated that listeners can learn to better understand neurologically degraded speech. Furthermore, it has offered insight into how the information afforded by the specific familiarisation procedure is differentially leveraged to improve perceptual performance during subsequent encounters with the dysarthric signal. Thus, this programme of research affords preliminary evidence towards the development of a theoretical framework that exploits perceptual learning for the treatment of dysarthria.
26
Martino, Francesco. "Intrinsic and extrinsic stimulus factors of perceptual slant in depth". Doctoral thesis, Università degli studi di Padova, 2008. http://hdl.handle.net/11577/3427205.
Testo completoAbstract (sommario):
This works aims at studying the interaction the interaction of depth-cues according to a spatial-topological criterium. The first section describe a set-theoretic model, which aims to provide a general description of the problem. Attention is paid to the distinction between intrinsic and extrinsic sources of information about depth. The following chapters present three different experimetnal works, aiming at showing how the presence and the interaction between extrinsic and intrinsic factors plays a major role in depth perception. Conclusion propose an application of the this ideas based on the "Constraint Network" theory.Il presente lavoro di ricerca si propone di indagare l'interazione di fattori di che determinano la percezione della profondità distinti secondo criteri spaziali-topologici. La prima parte presenta un modello formale di tipo insiemistico, che ha lo scopo di fornire una descrizione generale del problema. Particolare attenzione è rivolta alla distinzione tra fattori intriseci e fattori estrinseci. La tesi presenta quindi tre diversi lavori sperimentali, che hanno lo scopo di dimostrare come la presenza e l'interazione di fattori intriseci o estrinseci sia un fattore importante nella percezione della tridimensionalità. La tesi si conclude con una proposta di applicazione legata alla teoria della Rete di Vincoli.
27
Edgar, Nicole M. "Mechanisms of Compass Orientation in C57BL/6 Laboratory Mice". Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/32850.
Testo completoAbstract (sommario):
Compass orientation or menotaxis is defined as the ability to orient at a specific angle relative to a directional cue. Cues used for compass orientation include the sun, stars, moon, geomagnetic field and polarized light. While there is evidence in a variety of organisms for compass orientation, the ability of mammals to use cues for compass orientation has been relatively unexplored. The goal of this research was to explore whether laboratory mice could use either magnetic or auditory cues for compass orientation. The results indicate that mice are able to learn to position their nest using a magnetic compass. The development of a magnetic compass assay in laboratory mice will allow the investigation of the mechanism of magnetic compass orientation in mammals, a goal that has been unattainable to this point.In addition, this research has provided preliminary evidence that mice are able to learn to position their nests using an auditory compass. While there is evidence in several organisms for place navigation using auditory cues (i.e. the ability to locate a specific spatial position using auditory cues), this is the first evidence in any organism for an auditory compass (i.e. the ability to calculate a directional heading relative to an auditory cue).In conclusion, both experiments provide evidence for specialized compass systems in mice and suggest that further research is necessary to fully understand the role of these systems in the behavioral ecology of mice.Master of Science
28
Doyle, J. R. "Primitive perceptual mechanisms in reading : Familiarity effects in a signal detection task". Thesis, University of Sussex, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372716.
Testo completo
29
Uesaki, Maiko. "Brain Mechanisms Underlying Integration of Optic Flow and Vestibular Cues to Self-motion". Kyoto University, 2018. http://hdl.handle.net/2433/232163.
Testo completoAbstract (sommario):
Kyoto University (京都大学)0048
新制・課程博士
博士(文学)
甲第20828号
文博第758号
新制||文||655(附属図書館)
京都大学大学院文学研究科行動文化学専攻
(主査)教授 蘆田 宏, 教授 板倉 昭二, 教授 Anderson James Russell, 准教授 ALTMANN Christian
学位規則第4条第1項該当
30
McLaughlin, Timothy David. "The Expression of Gender in Synthetic Actors: Modeling and Motion Control Over Invariant Perceptual Cues Leading to Gender Recognition". Texas A&M University, 1994. http://hdl.handle.net/1969.1/90681.
Testo completoAbstract (sommario):
A perception based strategy for communicating the gender of computer animated
characters is evaluated. Motivated by the idea that effective character animation
involves the expression of character traits through motion, this study
builds upon previous work in the areas of computer animation and ecological psychology
in an effort to more fully characterize the dynamic information which
leads to the perception of gender. Information specifying the masculinity or femininity
of a walking figure is considered in relation to the range across which the
indexes may be exaggerated and applied to objects not normally considered male
or female.
31
Zhao, Weiying. "Mechanisms in the perceptual and respiratory-related evoked potential response to inspiratory loads". [Gainesville, Fla.] : University of Florida, 2001. http://purl.fcla.edu/fcla/etd/UFE0000368.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Florida, 2001.Title from title page of source document. Document formatted into pages; contains xii, 122 p.; also contains graphics. Includes vita. Includes bibliographical references.
32
Chen, Jing, e 陈静. "An investigation of visual cues and the neural mechanisms on human motor control behaviour". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B47849587.
Testo completoAbstract (sommario):
Accurate perception and control of self-motion is vital for human survival. Most
animals rely on vision for navigating through complex environments. In this
thesis, I investigated how vision influence perception and guide self-motion
from two aspects: (1) what visual information humans pick up from the
environment to form their perception and guide their self-motion; (2) how the
degeneration of the basal ganglia and cerebellum, the two largest subcortical
nuclei connecting the visual and motor areas of the brain, affect the controller’s
performance.
Study 1 examined the condition under which optic-flow information
beyond velocity field helps heading perception. I systematically varied the
amount of information in velocity field through manipulations of field of view
(FOV). The amount of optic-flow information beyond velocity field was
manipulated by two types of displays. I found heading bias increased with the
reduction of FOV only when optic-flow information beyond velocity field was
not available.
Study 2 investigated whether the information investigated in Study 1 is
sufficient and necessary for active control of heading. I used the similar display
simulations as study 1 with the exception that the vehicle orientation was
perturbed pseudo-randomly. Participants used a joystick, under both velocity
and acceleration control dynamics, to continuously rotate the vehicle orientation
back to its heading direction. The results showed that participants’ accurate
performance under condition that only provided velocity field information was
further improved when optic-flow information beyond velocity field was
available.
Study 3 examined the relative contributions of three visual cues (i.e.,
heading from optic flow, bearing, and splay angle) for lane-keeping control.
Observers controlled the car’s lateral movement to stay in the center of the lane
while facing two random perturbations affecting the use of bearing or splay
angle information. I found that performance improved with enriched flow
information. In the presence of splay angles, participants ignored bearing angle
information.
Study 4 investigated the roles of the basal ganglia and cerebellum in
motor control task using brain-damaged patients. Participant’s task was to use
the joystick to keep a blob in the center of the display while the horizontal
position of the blob was perturbed pseudo-randomly. This task is not a
self-motion task but mimics real-world lane-keeping control. Both the
Parkinson’s disease patients and cerebellar patients showed impaired motor
control performance in comparison with the healthy controls.
In conclusion, the visual information used for motor control in general
depends on the task. For traveling along a curved path, the velocity field
contains sufficient information for heading perception and heading control.
Optic-flow information beyond velocity field improves heading perception
when the velocity field does not contain sufficient information. It also helps
heading control when available. For lane-keeping control, adding optic flow
information improves participants’ performance. Splay angle information plays
a more important role than does bearing angle information. The visual
information used for motor control changes when certain brain areas are
damaged. Parkinson’s disease patients and cerebellar patients show the inability
to process visual input effectively for online motor control.published_or_final_version
Psychology
Doctoral
Doctor of Philosophy
33
Landler, Lukas. "Spontaneous directional preferences in taxonomically and ecologically distinct organisms: examining cues and underlying mechanisms". Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/73328.
Testo completoAbstract (sommario):
The focus of this research was the spontaneous magnetic alignment responses of animals. We show that snapping turtles (Chelydra serpentina) and crayfish (Cambarus sciotensis) spontaneously align their body axes relative to the magnetic field. In snapping turtles, this response is sensitive to low-level radio frequency fields, consistent with a mechanism involving a light-dependent radical pair mechanism. Findings from the turtle experiments also suggest that the Earth's magnetic field plays an important role in encoding spatial information in novel surroundings, and may help to organize multiple locales into a 'mental map' of familiar space. Given the importance of magnetic input in many aspects of spatial behavior, another important finding was that magnetic alignment of yearling turtles was disrupted by high levels of maternally transferred mercury, an industrial waste product found at high levels in some fresh water ecosystems. In crayfish, we investigated the effects of ectosymbionts (Annelida: Branchiobdellida) on magnetic alignment responses. Interestingly, the response of crayfish to magnetic cues parallels the complex symbiotic interaction between crayfish and their ectosymbiotic worms, which changes from mutualistic to parasitic with increasing worm density. Our working hypothesis was that these changes in spatial behavior may increase or decrease contact to other crayfish, and therefore increase or decrease transmission rates. Next, to address the ontogeny of the SMA, we attempted to replicate an earlier study showing a possible magnetic alignment response in chicken embryos. Although chicken embryos did show non-random alignment, we were not able to find a magnetic effect. Alignment is also an important feature of animal constructions and is very likely to have fitness consequences, which we explored in woodpecker cavity alignments in a meta-analysis of available global data. The latitudinal and continental pattern in 23 species of woodpeckers suggests that an alignment response can have the proximate function to regulate microclimate in the cavity and therefore, presumably, optimize incubation temperatures and increase hatching success. Overall, the presented findings show how experimental and observational studies of spontaneous alignment behavior can provide insight into the ecology and sensory biology of a wide range of animals.Ph. D.
34
Walshe, Ross Calen. "Operation of eye-movement control mechanisms during the perception of naturalistic scenes". Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/20966.
Testo completoAbstract (sommario):
Understanding of visual scenes takes place within very brief episodes known as fixations. To explore the extent of the scene, the eye shifts between fixation locations at intervals of roughly 300 ms. Currently, it is a matter of open inquiry as to what factors influence the timing of these movements. This thesis focuses on understanding the mechanisms that govern the rapid adjustment of fixation and saccade timings when novel stimulus information is encountered during a fixation. In part I, I use an experimental technique known as the fixation-contingent scene quality paradigm to control the quality of incoming visual scene information. This approach is used to assess how fixation timing adapts to moment-by-moment changes in the quality level of the stimulus. I find that quality changes tend to result in an increase in fixation durations and this occurs whether the quality is increased or decreased. Using distributional analytic techniques, I argue that these results reflect the combined influence of a rapid surprise related process and a slower acting encoding related influence. In part II, I study how fixation durations are influenced by the underlying saccade programming mechanisms. An important assumption within the eye-movement control literature is that there exists a threshold called the point-of-no-return. Once this point has been reached, a saccade may no longer be modified or cancelled. I adapt a classic psychophysical technique known as the double-step procedure to study the point-of-no-return within scene viewing tasks. I also provide a measurement of the saccadic dead time, the last point in time that a saccade may be modified. In Part III, a formal model of fixation durations in high-level tasks is presented. I build on recent modelling work and develop a formal account for the early-surprise late-encoding modulation account of fixation durations in scene viewing tasks. The model is tested against data observed in Part I of the thesis. I demonstrate that the model does a very good job of predicting these distributions with relatively few assumptions. In summary, I use experimental techniques in combination with computational modelling to reveal how a composite of low-level (saccade programming) and high-level (information processing) considerations can, and must, be taken into consideration when understanding eye-movement control behaviour in scene viewing tasks.
35
Van, Horn Nicholas M. "Perceptual Learning And Visual Short-Term Memory: The Limitations And Mechanisms Of Interacting Processes". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408731180.
Testo completo
36
Harland, Duane Peter. "Optical cues and vision-based discrimination mechanisms underlying predatory versatility in jumping spiders (Araneae: Salticidae)". Thesis, University of Canterbury. Zoology, 2000. http://hdl.handle.net/10092/5869.
Testo completoAbstract (sommario):
Experimental studies of behaviour were carried out on jumping spiders (Salticidae), with particular attention given to araneophagic species in the genus Portia. Portia fimbriata was the primary species used in experiments. The objective of the research was to clarify mechanisms underlying visual perception, with this being part of a larger aim of understanding animal cognition. Literature on the structure and function of salticid eyes was reviewed in depth, with hypotheses and directions for future work highlighted. Distances at which salticid species distinguish prey insects from conspecific rivals was investigated using adult males of 37 salticid species. The discrimination distances recorded for most species imply higher levels of spatial acuity than has generally be appreciated for salticids. The longest discrimination distances found were for Mogrus neglectus, (max. 320 mm or 42 body lengths), with Portia fimbriata coming close (280 mm or 47 body lengths). P. fimbriata is unique among Portia spp.: all species of Portia prey routinely on other spiders (araneophagy), but P. fimbriata also has a specialised method of stalking and capturing other salticids. Optical cues by which P. fimbriata distinguishes salticid from non-salticid prey were investigated. P. fimbriata’s reactions to 114 salticid species were established. Except for Myrmarachne spp. (ant mimics), all salticids (both sympatric and allopatric species, species with aberrant body form and highly camouflaged species) triggered salticid-specific tactics by P. fimbriata. Experiments with odourless lures made from dead prey on which various combinations of features were altered imply that the large principal eyes of salticid prey provide optical cues that are critical for triggering P. fimbriata’s salticid-specific predatory tactics. Cues from the legs of prey salticids influence whether P. fimbriata’s stalks at all, but not whether salticid specific tactics are adopted. Cues from the cephalothorax and abdomen also influenced stalking tendency, but more weakly than cues from the legs. Using specially developed virtual 3D lures, presented to P. fimbriata on a projector screen, details concerning cues from the principal eyes of salticids were investigated. To be identified as a salticid, evidently there must be at least one principal eye on the face that is large and round. P. fimbriata distinguishes the orientation of salticid prey. A hypothetical model of how P. fimbriata distinguishes salticid orientation is discussed. That Portia spp. distinguishes the orientation of other non-salticid web-building spiders is also established in experiments where live prey is used. Using lures made from Badumna longinquus, a web-building spider, orientation-revealing optical cues were investigated. The research in this thesis suggests a framework for future studies.
37
葉慧敏 e Wai-man Ip. "Birds of a feather and birds flocking together: static versus dynamic perceptual cues could lead totrait- versus goal-based group perception". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31243162.
Testo completo
38
Baccam, Alexandra. "Mechanisms involved in the cross-talk between humoral and mechanical cues underlying muscle wasting in cachexia". Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS107/document.
Testo completoAbstract (sommario):
Cachexie est syndrome multifactoriel associé a une maladie chronique ou incurable et caractérisé par un importante fonte musculaire. En fait, l’exercice physique améliore la qualité de vie et la survie des patients cancéreux. Dans un modèle animal de cachexie dû au cancer, nous avons démontré que la course sur roue contre la cachexie par la libération du flux d’autophagie. Les effets de l’exercice pléitropique incluent la modification des facteurs circulants en faveur d’un environnement anti-inflammatoire et l’activation des voies de mécanotransduction dans les cellules musculaires. Notre but est d'évaluer si la mécanotransduction est suffisante à elle seule pour mimer l’exercice en présence de facteurs pro-cachétiques d'origine tumorale. Le facteur de réponse au sérum (SRF est un facteur de transcription important pour homéostasie musculaire, qui est activé avec son co-facteur MRTF par la mécanotransduction de façon dépendant à la polymérisation de l'actin. Nous utilisons une culture mixte de C2C12 myotubes et myoblastes traitée avec un milieu condition par des C26 (CM) en absence ou en présence d'étirements cycliques qui miment la stimulation mécanique. Nous avons démontré in vitro que le CM a un effet négatif sur les cultures de cellules musculaires, sur l'atrophie des myotubes, sur le recrutement et la fusion des myoblastes, et que ces effets sont contrecarrés par l'étirement mécanique. Nous avons montré que le CM inhibe l'activité transcriptionnelle de SRF-MRTF, alors que l'étirement mécanique rétablit cette activité ; en plus, des expériences de perte de fonction ont démontré que SRF est nécessaire pour médier les effets bénéfiques des stimulations mécaniques sur les cellules musculaires. Au moins une part des effets de l’exercice observés étaient médiés par la balance des facteurs pro- et anti-myogeniques de la superfamille TGF-b. Nous proposons que les effets positifs de l’exercice sur les patients cancéreux et les souris pourraient être spécifiquement dûs a la réponse mécanique des fibres musculaires affectant la sécrétion des myokinesCachexia is a multifactorial syndrome associated to chronic or acute disease (cancer, HIV,…) and characterized by severe muscle wasting. In fact, exercise training improves quality of life and survival of cancer patients. In an animal model of cancer cachexia we demonstrated that wheel running counteracts cachexia by releasing the autophagic flux. Exercise pleitropic effects include the alteration of circulating factors in favour of an anti-inflammatory environment and the activation of mechanotransduction pathways in muscle cells. Our goal is to assess whether mechanostransduciton per se is sufficient to elicit exercise effects in the presence of pro-cachectic factors of tumor origin. Serum response factor (SRF) is a transcription factor of pivotal importance for muscle homeostasis, which is activated with its co-factor MRTF by mechanostranduction in a way dependent on actin polymerisation. We use mixed cultures of C2C12 myotubes and myoblasts treated with C26 conditioned medium (CM) in the absence or presence of cyclic stretch to mimic the mechanical stimulation occurring upon exercise. In vitro we showed that CM had a negative effect on muscle cell cultures, both in terms of myotube atrophy and of myoblast recruitment and fusion, and that these effects were counteracted by cyclic stretch. We showed that CM repressed SRF-MRTF transcriptional activity, while mechanical stretch rescued their transcriptional activity; in addition, loss of function experiments demonstrated that SRF was necessary to mediate the beneficial effects of mechanical stimulation on muscle cells. At least part of the observed effects was mediated by the balance of pro- and anti-myogenic factor of the TGF-b superfamily. We propose that the positive effects of exercise on cancer patients and mice may be specifically due to a mechanical response of muscle fibers affecting the secretion of myokines
Cachexia è una sindrome di multifactorial associata a malattia cronica o acuta (cancro, HIV.) e caratterizzò da spreco di muscolo severo. Infatti, l'esercizio addestrando migliora qualità della vita e sopravvivenza di pazienti di cancro. In un modello animale di cachexia di cancro noi dimostrammo quello ruota correndo contrattacca cachexia rilasciando il flusso di autophagic. Gli effetti di pleitropic di esercizio includono la modifica di fattori circolanti nel favore di un ambiente antinfiammatorio e l'attivazione di sentieri di mechanotransduction in celle di muscolo. La nostra meta è stimare se mechanostransduciton per se è sufficiente per suscitare effetti di esercizio nella presenza di pro-cachectic fattori di origine di tumore. Il fattore (SRF) di risposta di siero è un fattore di trascrizione dell'importanza importantissima per omeostasi di muscolo che è attivato col suo co-coefficiente MRTF da mechanostranduction in un modo dipendente su polymerisation di actin. Noi usiamo le culture mescolate del myotubes di C2C12 e myoblasts trattate con C26 condizionarono mezzo (Cm) nell'assenza o presenza di stiramento ciclico a mimico la stimolazione meccanica che accade su esercizio. In vitro noi mostrammo che il Cm aveva un effetto negativo su culture di cella di muscolo, ambo nelle condizioni di atrofia di myotube e di assunzione di myoblast e fusione, e che questi effetti furono contrattaccati da stiramento ciclico. Noi mostrammo che il Cm represse l'attività di transcriptional di SRF-MRTF, mentre lo stiramento meccanico liberò la loro attività di transcriptional; in somma, perdita di esperimenti di funzione dimostrò, che SRF era necessario per interporre gli effetti benefici di stimolazione meccanica su celle di muscolo. Almeno parte degli effetti osservati fu interposta dall'equilibrio di pro - ed anti-myogenic fattore del TGF. il superfamily. Noi proponiamo che gli effetti positivi di esercizio su pazienti di cancro e topi specificamente possono essere a causa di una risposta meccanica di fibre di muscolo che colpiscono l'occultamento di myokines
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Farris, Coreen. "Perceptual and decisional processing of diagnostic and non-diagnostic cues of women's sexual interest influence of alcohol intoxication and sexual coercion history /". [Bloomington, Ind.] : Indiana University, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3319899.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--Indiana University, Dept. of Phychological and Brain Sciences, 2008.Title from PDF t.p. (viewed on May 13, 2009). Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 5021. Advisers: Richard J. Viken; Teresa A. Treat.
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Ip, Wai-man. "Birds of a feather and birds flocking together : static versus dynamic perceptual cues could lead to trait- versus goal-based group perception /". Hong Kong : University of Hong Kong, 2002. http://sunzi.lib.hku.hk/hkuto/record.jsp?B25139435.
Testo completo
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Panitz, Christian [Verfasser], e Erik M. [Akademischer Betreuer] Müller. "Cortico-Cardiac Processing of Affective-Motivational Cues - Mechanisms and Individual Differences / Christian Panitz ; Betreuer: Erik M. Müller". Marburg : Philipps-Universität Marburg, 2017. http://d-nb.info/1149551097/34.
Testo completo
42
Harris, Anna Kathleen. "The Impact of Warning Label Exposure on Attentional Bias to Smoking Cues in Smokers and Nonsmokers". W&M ScholarWorks, 2013. https://scholarworks.wm.edu/etd/1539626741.
Testo completo
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Meaux, Eric. "Approche perceptive pour la spatialisation / localisation sonore 3D". Thesis, La Rochelle, 2022. http://www.theses.fr/2022LAROS004.
Testo completoAbstract (sommario):
La localisation sonore est le procédé utilisé par les êtres humains pour repérer un son dans l’espace. Afin de localiser ces sons, le cerveau traite l’information reçue, et crée des indices acoustiques. L’approche de la thèse pour la localisation sonore perceptive, reposant sur le travail d’Harald Viste pour la localisation de l’azimut, consiste à utiliser ces indices acoustiques dans un algorithme. L’algorithme initial est légèrement simplifié dans cette thèse, et testé dans des conditions réelles. De plus, une approche perceptive innovante pour la localisation de l’élévation est également présentée. La spatialisation sonore est le procédé inverse, permettant de produire un son que l’on percevra à la position souhaitée dans l’espace. Du fait de l’impossibilité d’avoir un système de diffusion en tout point de l’espace, il est nécessaire de recourir à des algorithmes de spatialisation, permettant par exemple des diffusions via des hautparleurs. L’approche perceptive de la thèse, basée sur le travail de Joan Mouba, est d’utiliser les indices acoustiques de la localisation sonore, dans ce travail en les créant dans les sources sonores spatialisées. Ce travail de thèse approfondit les recherches initiales, crée des outils pour aboutir à une proposition de méthode de spatialisation sonore perceptive 3D nommée STAR (Synthetic Transaural Audio Rendering), tout en validant la méthode par des tests rigoureusement menésSound localization is the process used by humans to locate sound in space. In order to locate these sounds, the brain processes the information received, and creates acoustic cues. The thesis approach to perceptual sound localization, based on Harald Viste’s work for azimuth localization, is to use these acoustic cues in an algorithm to locate a sound source. The initial algorithm is slightly simplified in this thesis, and tested in real conditions. In addition a perceptual approach for the location of the elevation is also presented. Sound spatialization is the reverse process, making it possible to produce a sound that will be perceived at the position of the desired space. Due to the impossibility of having a broadcast system at any point in space, it is necessary to use spatialization algorithms, for example allowing broadcasts through loudspeakers. The perceptual approach of the thesis, based on the work of Joan Mouba, is to use the acoustic cues of sound localization, this time by creating them in spatialized sound sources. This thesis work deepens the initial research, notably proposes a 3D perceptual sound spatialization method called STAR (Synthetic Transaural Audio Rendering), while validating the method through tests
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Oh, Soo Hee. "Top-Down Processes in Simulated Combined Electric-Acoustic Hearing: The Effect of Context and the Role of Low-Frequency Cues in the Perception of Temporally Interrupted Speech". Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5379.
Testo completoAbstract (sommario):
In recent years, the number of unilateral cochlear implant (CI) users with functional residual-hearing has increased and bimodal hearing has become more prevalent. According to the multi-source speech perception model, both bottom-up and top-down processes are important components of speech perception in bimodal hearing. Additionally, these two components are thought to interact with each other to different degrees depending on the nature of the speech materials and the quality of the bottom-up cues. Previous studies have documented the benefits of bimodal hearing as compared with a CI alone, but most of them have focused on the importance of bottom-up, low-frequency cues. Because only a few studies have investigated top-down processing in bimodal hearing, relatively little is known about the top-down mechanisms that contribute to bimodal benefit, or the interactions that may occur between bottom-up and top-down processes during bimodal speech perception.
The research described in this dissertation investigated top-down processes of bimodal hearing, and potential interactions between top-down and bottom-up processes, in the perception of temporally interrupted speech. Temporally interrupted sentences were used to assess listeners' ability to fill in missing segments of speech by using top-down processing. Young normal hearing listeners were tested in simulated bimodal listening conditions in which noise band vocoded sentences were presented to one ear with or without low-pass (LP) filtered speech or LP harmonic complexes (LPHCs) presented to the contralateral ear. Sentences were square-wave gated at a rate of 5 Hz with a 50 percent duty cycle. Two factors that were expected to influence bimodal benefit were examined: the amount of linguistic context available in the speech stimuli, and the continuity of low-frequency cues.
Experiment 1 evaluated the effect of sentence context on bimodal benefit for temporally interrupted sentences from the City University of New York (CUNY) and Institute of Electrical and Electronics and Engineers (IEEE) sentence corpuses. It was hypothesized that acoustic low-frequency information would facilitate linguistic top-down processing such that the higher context CUNY sentences would produce more bimodal benefit than the lower context IEEE sentences. Three vocoder channel conditions were tested for each type of sentence (8-, 12-, and 16-channels for CUNY; 12-, 16-, and 32-channels for IEEE), in combination with either LP speech or LPHCs. Bimodal benefit was compared for similar amounts of spectral degradation (matched-channels) and similar ranges of baseline performance. Two gain measures, percentage point gain and normalized gain, were examined.
Experiment 1 revealed clear effects of context on bimodal benefit for temporally interrupted speech, when LP speech was presented to the residual-hearing ear, thereby providing additional support for the notion that low-frequency cues can enhance listeners' use of top-down processing. However, the bimodal benefits observed for temporally interrupted speech were considerably smaller than those observed in an earlier study that used continuous speech. In addition, unlike previous findings for continuous speech, no bimodal benefits were observed when LPHCs were presented to the LP ear.
Experiments 2 and 3 further investigated the effects of low-frequency cues on bimodal benefit by systematically restoring continuity to temporally interrupted signals in the vocoder and/or LP ears. Stimuli were 12-channel CUNY sentences presented to the vocoder ear, and LPHCs presented to the LP ear. Signal continuity was restored to the vocoder ear by filling silent gaps in sentences with envelope-modulated, speech-shaped noise. Continuity was restored to signals in the LP ear by filling gaps with envelope-modulated LP noise or by using continuous LPHCs. It was hypothesized that the restoration of continuity in one or both ears would improve bimodal benefit relative to the condition in which both ears received temporally interrupted stimuli.
The results from Experiments 2 and 3 showed that restoring continuity to the simulated residual-hearing or CI ear improved bimodal benefits, but that the greatest improvement was observed when continuity was restored to both ears. These findings support the conclusion that temporal interruption disrupts top-down enhancement effects in bimodal hearing. Lexical segmentation and perceptual continuity were identified as factors that could potentially explain the increased bimodal benefit for continuous, as compared to temporally interrupted, speech.
Taken together, the findings from Experiments 1-3 provide additional evidence that low-frequency sensory information can provide bimodal benefit for speech that is spectrally and/or temporally degraded by improving listeners' ability to make use of top-down processing. Findings further suggest that temporal degradation reduces top-down enhancement effects in bimodal hearing, thereby reducing bimodal benefit for temporally interrupted speech as compared to continuous speech.
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Alvarez, Bryan Dean. "Behavioral and brain mechanisms of grapheme-color synesthesia and their relationships with perceptual binding and visual imagery". Thesis, University of California, Berkeley, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3616537.
Testo completoAbstract (sommario):
Synesthesia is an unusual blending of the senses that occurs in about four percent or more of the human population. Much effort has been devoted to establishing criteria to define what synesthesia is ever since the phenomenon reemerged as a fascination within the scientific community in the late 1970s. To date, the most common criteria for synesthesia are that synesthetic experiences be automatic, consistent, rely on an external stimulus that triggers the phenomenological experience, and that this experience is fully conscious to the mind. This framework allows for some differentiation of synesthetes compared to non-synesthetes within the human population, and yet it also creates a self-selecting bias in the synesthetic population; if the scientific community defines criteria for synesthesia, and then only studies people whom fit those criteria, the resulting data will likely validate the definitions if only because they have been defined that way. What is left unknown are ways that synesthetes, as a community of otherwise normal human beings, vary in subtle ways, both in their psychophysical behavior and in their neurobiological form and function in relation to other human beings who do not experience any form of conscious, unusual sensory blendings yet defined as synesthesia.
The studies described in this thesis explore whether perception in the population of individuals currently defined as synesthetes is in fact uniquely different from perception in the rest of the human population. These unique differences in perception are also used here to better inform our understanding of the functions of the human brain. Chapter 2 introduces the concept of perceptual binding and its relation to synesthesia. Some synesthetes experience colors that are associated with letters and numbers, and these so-called grapheme-color synesthetes may rely on similar brain mechanisms to bind their synesthetic colors to space as the ones they (and most humans) use to bind color to space normally. Chapter 3 addresses the question of binding with regard to an unusual phenomenon specific to grapheme-color synesthetes: that it is possible for some of these synesthetes to experience two colors that are spatially co-localized without blending. The results of this behavioral study will be shown to correlate with the vividness of visual imagery, a measure that extends beyond synesthetic phenomenology. Finally, Chapter 4 demonstrates how synesthetes differ from well-matched non-synesthetes in relation to behavior and the anatomy of the brain. Specifically, synesthetes have more vivid visual imagery as a population, more arborized white matter, and show a positive correlation between vivid imagery and increased axonal branching that is absent in non-synesthete controls. Together, these studies suggest that the brains of synesthetes rely on attention-specific mechanisms used by most humans to bind color to space. However, synesthesia as a whole may not simply be one end of a continuum of brain differences. Rather, synesthetes may be unique both in their phenomenological experiences of the world, and in some ways, the organization of the brain that creates them.
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Reichert, David Paul. "Deep Boltzmann machines as hierarchical generative models of perceptual inference in the cortex". Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/8300.
Testo completoAbstract (sommario):
The mammalian neocortex is integral to all aspects of cognition, in particular perception across all sensory modalities. Whether computational principles can be identified that would explain why the cortex is so versatile and capable of adapting to various inputs is not clear. One well-known hypothesis is that the cortex implements a generative model, actively synthesising internal explanations of the sensory input. This ‘analysis by synthesis’ could be instantiated in the top-down connections in the hierarchy of cortical regions, and allow the cortex to evaluate its internal model and thus learn good representations of sensory input over time. Few computational models however exist that implement these principles. In this thesis, we investigate the deep Boltzmann machine (DBM) as a model of analysis by synthesis in the cortex, and demonstrate how three distinct perceptual phenomena can be interpreted in this light: visual hallucinations, bistable perception, and object-based attention. A common thread is that in all cases, the internally synthesised explanations go beyond, or deviate from, what is in the visual input. The DBM was recently introduced in machine learning, but combines several properties of interest for biological application. It constitutes a hierarchical generative model and carries both the semantics of a connectionist neural network and a probabilistic model. Thus, we can consider neuronal mechanisms but also (approximate) probabilistic inference, which has been proposed to underlie cortical processing, and contribute to the ongoing discussion concerning probabilistic or Bayesian models of cognition. Concretely, making use of the model’s capability to synthesise internal representations of sensory input, we model complex visual hallucinations resulting from loss of vision in Charles Bonnet syndrome.We demonstrate that homeostatic regulation of neuronal firing could be the underlying cause, reproduce various aspects of the syndrome, and examine a role for the neuromodulator acetylcholine. Next, we relate bistable perception to approximate, sampling-based probabilistic inference, and show how neuronal adaptation can be incorporated by providing a biological interpretation for a recently developed sampling algorithm. Finally, we explore how analysis by synthesis could be related to attentional feedback processing, employing the generative aspect of the DBM to implement a form of object-based attention. We thus present a model that uniquely combines several computational principles (sampling, neural processing, unsupervised learning) and is general enough to uniquely address a range of distinct perceptual phenomena. The connection to machine learning ensures theoretical grounding and practical evaluation of the underlying principles. Our results lend further credence to the hypothesis of a generative model in the brain, and promise fruitful interaction between neuroscience and Deep Learning approaches.
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[Verfasser], Ferreira de Sá Diana S., e Hartmut [Akademischer Betreuer] Schächinger. "Reward-related processing of visual food cues: neuroendocrine and stress mechanisms / Diana S. Ferreira de Sá ; Betreuer: Hartmut Schächinger". Trier : Universität Trier, 2015. http://d-nb.info/1197701273/34.
Testo completo
48
Galois, Patrick. "Turtle nest sensory perception by raccoon (Procyon lotor) and striped skunk (Mephitis mephitis) : an approach through discrimination learning of potential nest cues". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42038.
Testo completoAbstract (sommario):
Egg predation may be the most important mortality factor for North American turtles. This predation can destroy 50-90% of nests in an area. The major predators are striped skunks (Mephitis mephitis) and raccoons (Procyon lotor). Despite differences in their habits and diet, these species appear equally efficient in turtle egg predation, even though these eggs represent a very small portion of their annual food intake. Sight, olfaction, touch and hearing could be used by these predators to find the nests. The aim of this study was to document intra and inter-specific differences in the perception of possible nest-cues used by raccoon and striped skunk. Choice-tests based on food-conditioning were carried out with two visual cues (dark and smooth surface), one olfactory cue (turtle urine) and one tactile cue (soil compaction). Subject performances (number of trials to obtain 80% success rate in the different tests) were compared to assess intra and inter-species, and skunk inter-age differences in sensory perception and learning abilities. As expected raccoons learned the tactile cue discrimination faster than the visual cue discriminations. The tactile cue discrimination was learned as fast as the olfactory cue. As expected skunks learned the olfactory cue discrimination faster than other cue discriminations. When compared, the olfactory cue appeared to be as important for both species even though raccoons had faster learning rates than skunks in all the tests except for one visual test. Juvenile skunks learned faster than adult skunks with four out of six juveniles performing better in the olfactory test. Olfaction may play an important role in nest localization by raccoons and skunks, and sight may also play a role for raccoons. Learning turtle nest cues while with their mother could facilitate their future ability in locating turtle nests.
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Schönstein, David. "Individual of spectral cues for applications in virtual auditory space : study of inter-subject differences in Head-Related Transfer Functions using perceptual judgements from listening tests". Paris 6, 2012. http://www.theses.fr/2012PA066488.
Testo completo
50
Frangou, Polytimi. "Inhibitory mechanisms for visual learning in the human brain". Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/280767.
Testo completoAbstract (sommario):
Identifying targets in cluttered scenes is critical for our interactions in complex environments. Our visual system is challenged to both detect elusive targets that we may want to avoid or chase and discriminate between targets that are highly similar. These tasks require our visual system to become an expert at detecting distinctive features that help us differentiate between indistinguishable targets. As the human brain is trained on this type of visual tasks, we observe changes in its function that correspond to improved performance. We use functional brain imaging, to measure learning-dependent modulations of brain activation and investigate the processes that mediate functional brain plasticity. I propose that dissociable brain mechanisms are engaged when detecting targets in clutter vs. discriminating between highly similar targets: for the former, background clutter needs to be suppressed for the target to be recognised, whereas for the latter, neurons are tuned to respond to fine differences. Although GABAergic inhibition is known to suppress redundant neuronal populations and tune neuronal representations, its role in visual learning remains largely unexplored. Here, I propose that GABAergic inhibition plays an important role in visual plasticity through training on these tasks. The purpose of my PhD is to investigate the inhibitory mechanisms that mediate visual perceptual learning; in particular, learning to detect patterns in visual clutter and discriminate between highly similar patterns. I show that BOLD signals as measured by functional Magnetic Resonance Imaging (fMRI) do not differentiate between the two proposed mechanisms. In contrast, Magnetic Resonance Spectroscopy (MRS) provides strong evidence for the distinct involvement of GABAergic inhibition in visual plasticity. Further, my findings show GABA changes during the time-course of learning providing evidence for a distinct role of GABA in learning-dependent plasticity across different brain regions involved in visual learning. Finally, I test the causal link between inhibitory contributions and visual plasticity using a brain stimulation intervention that perturbs the excitation-inhibition balance in the visual cortex and facilitates learning.