Thèses : « Attentive Mechanisms »

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PROIETTI, VALENTINA MARIA. « How early and later-acquired experience affects the age bias in face recognition : an exploration of age-of-acquisition effects ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2015. http://hdl.handle.net/10281/75273.

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In this doctoral dissertation I present some of the studies conducted during my PhD aimed to investigate how face processing abilities develop across the lifespan and how the face representation system adapts to reflect each individual's social experience. As adults we are expert at processing faces; nevertheless our ability is greater for some categories of faces than for others, giving rise to recognition biases based on social dimensions such as species, race and age. These biases have been interpreted as a result of the interaction between individual motivation and perceptual experience provided by social environment, which work together in affecting the way we encode, process and mentally represent faces. The studies presented in this dissertation focused on the age bias that is the variability in face recognition abilities determined by the relation between the age of the observer and the age of the perceived face. Specifically I will discuss recent evidence suggesting the presence of a processing advantage for adult versus non-adult faces in the lifespan (from infancy to old age) and I will provide novel evidence on how the time of acquisition modulates the effects of individual experience with non –adult faces on this perceptual advantage for adult faces across the life-span. In Chapter 1 I will investigate the short- and long-term effects of early-acquired experience with a child or an infant face provided by the presence of a younger or older sibling in our participants’ family household. Study 1 and Study 2 investigated the behavioral and the neural correlates of the perceptual tuning towards adult faces and its modulation as a consequence of sibling experience, within the first year of life. These two studies show that early-acquired experience has a critical role in the emergence of neurocognitive specialization for adult faces. Study 3 provides evidence on the long-lasting effects of this early acquired experience in interaction with later-acquired experience during adulthood: recognition ability for adult and infant faces was tested in first-time mothers who were or were not exposed to sibling experience in their first years of life. Results show that experience acquired early in life has a greater impact than the one acquired later in life, as only mothers with a younger sibling were able to bootstrap perceptual learning of infant faces from exposure to their own child. These findings suggest that early-acquired experience has continuous effects into adulthood, as it preserves the system from the loss of plasticity that would otherwise take place. In Chapter 2 I will investigate the extent to which face representation system remains plastic during adulthood and old age. Results show that professional experience with older adult individuals in adulthood and social experience with peers in old age reduce the magnitude of the recognition advantage for adult faces suggesting that experience with multiple individuals is capable to modulate face processing abilities even in adulthood and old age. Lastly Study 6 investigated how face age affects the deployment of selective visual attention and whether this effect is modulated by professional experience with non-adult faces acquired later in development. Findings provided by this last work extend the few existing evidence on the impact of face dimensions, such as age and race, on visual attention and yielded novel insights into the differential mechanisms underlying the age and the race bias. Overall these studies confirmed the plasticity of the face representational system which constantly adapts to reflect the individual’s current social and perceptual experience across the whole lifespan from infancy up to old age.

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Fitzgerald, Marilyn. « Are attention bias and interpretation bias reflections of a single common mechanism or multiple independent mechanisms ? » University of Western Australia. School of Psychology, 2008. http://theses.library.uwa.edu.au/adt-WU2009.0052.

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There is abundant evidence of anxiety-linked threat-biased attention and anxiety-linked threat-biased interpretation (cf. Mathews & MacLeod, 1994, 2005). The present research aimed to determine whether these cognitive biases reflect a single common underlying mechanism (the Common Mechanism Account) or multiple independent underlying mechanisms (the Independent Mechanisms Account). To address this question, a battery of eight experimental tasks was developed; four tasks measured attention bias and four measured interpretation bias. Participants with different levels of trait anxiety, completed pairs of these tasks. The pattern of associations amongst all eight tasks was compared with the pattern of associations between the four tasks that measured attention bias and the pattern of associations between the four tasks that measured interpretation bias. Both Accounts predicted strong associations between the four tasks that measured attention bias, and between the four tasks that measured interpretation bias. However, the Common Mechanism Account predicted generally strong associations between all of the eight tasks, that were equivalent in strength to the associations between tasks measuring attention bias and to the associations between tasks measuring interpretation bias. In contrast, the Independent Mechanisms Account predicted weaker associations between all of the eight tasks than the associations either between the tasks measuring attention bias or between the tasks measuring interpretation bias. The obtained pattern of associations between internally reliable measures of anxiety-linked attention bias and anxiety-linked interpretation bias failed to support the Common Mechanism Account, but rather was consistent with the predictions of the Independent Mechanisms Account. Theoretical and applied implications of the results are discussed.

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Kerr, John H. « Arousal mechanisms, attention and sports performance ». Thesis, University of Nottingham, 1988. http://eprints.nottingham.ac.uk/10947/.

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This thesis is concerned with the relationship between arousal mechanisms, attentional processes and competitive sports performance. Theoretical interpretations of the arousal-performance relationship have traditionally followed the inverted-U hypothesis. Based on this approach, the generally accepted view in sports psychology is that high levels of arousal are detrimental to good performance. A review of the relevant psychological literature reveals the limited nature of such an approach and draws attention to alternative perspectives such as those offered by the work of Apter and that of Cox and Mackay. These more recent theoretical approaches allow more sophisticated interpretations of the individual's experience of arousal to be realised. Important here are other aspects of the individual's psychological state (cognition and emotion) as these are thought to affect his or her interpretation of arousal. Interestingly, the two theories, developed independently by Apter and by Cox and Mackay, appear consistent, one with the other, and have not previously been applied to the study of competitive sport. Several different research techniques were incorporated into a research design which used squash players of varying levels of ability to examine the various psychological factors important in their experience of and performance in competitive squash. The research techniques, some of which were innovative, proved effective indentifying the interaction of arousal and stress in relation to competitive performance. It was concluded that psychological preparation and experience (i.e. number of years, number of times per week played), along with personality characteristics and attentional strategies, contribute to success in competitive squash. Fluctuations in emotional responses characterised players whose performance was unsuccessful. By way of contrast, successful players' (i.e. successful in terms of level of ability attained, skill performance and winning games) psychological responses were more consistent. They achieved and maintained high levels of arousal both prior to and during performance. High arousal was, for successful players, accompanied by low stress and positive hedonic tone when they were subject to the demands of competitive squash games. Overall, successful players (that is skilled players in Study 2 and winners from Study 3) were highly extravert and significantly less neurotic (Eysenck) than other groups of players. Telic dominance was not a discriminating characteristic in this investigation, but successful players' attentional styles were significantly different, as defined by Nideffer's BIT and INFP subscales, to those styles or strategies employed by less capable players. Successful players generally employed psychological preparation strategies prior to and during play to a greater extent than other players. When doing so, they were more concerned with cognitive strategies, in the form of focussing and planning, than arousal modulation strategies. The present research investigation advanced knowledge about the processes involved in competitive sports, providing new and relevant information. As a result, a number of suggestions for squash coaching and player development, along with implications for cognitive intervention with sports performers, have emerged.

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Gama, Nuno. « Mechanisms of multisensory integration and attention ». Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/40400/.

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Spatial attention is an essential mechanism that helps us perceive our surroundings by bringing into consciousness environmental occurrences or objects that may be of importance. Studies of spatial attention have classically recorded behavioural responses to targets presented in a region of space where attention had previously been allocated to. Such investigations show a behavioural facilitation at the same location due to cueing, but less in known about the effects of shifts of attention when the cued location is not the location of interest. This thesis presents seven experiments aimed at investigating this by implementing and revising the attentional repulsion effect (ARE). The ARE is a perceptual localisation error when attention is diverted from the region of interest and it has been extensively studied in the visual domain, however, the rising number of ARE studies has created numerous research methodologies used to evoke the effect, which may have led to isolated reports. This thesis attempts to combine past methodologies with a new approach to quantify the effect, and will address some methodological differences evident in the literature, in order to optimise the stimulus paradigms and maximise the effect. The results show that a robust ARE can be elicited in the visual modality, but the same is not observed in the auditory modality. Furthermore, when using cues that are of different modality than the targets, the ARE is only observed in the visual target modality. Using visual cues and auditory targets will produce an attraction effect, in line with the ventriloquism theory. However, the implementation of interstimuli intervals up to 1.5 seconds would be enough to disrupt the ventriloquism illusion, but it did not alter the resulted attraction. Lastly, one question regarding the role of attention in sensory adaptation was addressed. I hypothesise that sensory adaptation could be further a contributor to the ARE given that most psychophysics paradigms of the ARE repeat the same stimuli thousands of times, uninterruptedly. The results are inconclusive mainly due to experimental design. All results are discussed in relation with theories of spatial and multimodal attention.

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Owen, Adrian Mark. « Fronto-striatal mechanisms in planning and attention ». Thesis, King's College London (University of London), 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302625.

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Gontrum, Johannes. « Attention Mechanisms for Transition-based Dependency Parsing ». Thesis, Uppsala universitet, Institutionen för lingvistik och filologi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-395491.

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Transition-based dependency parsing is known to compute the syntactic structure of a sentence efficiently, but is less accurate to predict long-distance relations between tokens as it lacks global information about the sentence. Our main contribution is the integration of attention mechanisms to replace the static token selection with a dynamic approach that takes the complete sequence into account. Though our experiments confirm that our approach fundamentally works, our models do not outperform the baseline parser. We further present a line of follow-up experiments to investigate these results. Our main conclusion is that the BiLSTM of the traditional parser is already powerful enough to encode the required global information into each token, eliminating the need for an attention-driven approach. Our secondary results indicate that the attention models require a neural network with a higher capacity to potentially extract more latent information from the word embeddings and the LSTM than the traditional parser. We further show that positional encodings are not useful for our attention models, though BERT-style positional embeddings slightly improve the results. Finally, we experiment with replacing the LSTM with a Transformer-encoder to test the impact of self-attention. The results are disappointing, though we think that more future research should be dedicated to this. For our work, we implement a UUParser-inspired dependency parser from scratch in PyTorch and extend it with, among other things, full GPU support and mini-batch processing. We publish the code under a permissive open source license at https://github.com/jgontrum/parseridge.

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Kennett, Steffan Anthony. « Links in spatial attention between touch and vision ». Thesis, Birkbeck (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343623.

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Santangelo, Valerio. « Multimodal investigation on spatial attention mechanisms : a model of shared attention resources (ShAR) ». Doctoral thesis, La Sapienza, 2005. http://hdl.handle.net/11573/917227.

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Tattersall, A. J. « Divided attention and the structure of temporary memory ». Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382717.

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Paltoglou, Aspasia Eleni. « Mechanisms of spatial and non-spatial auditory selective attention ». Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10697/.

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Selective attention is a crucial function that encompasses all perceptual modalities and which enables us to focus on the behaviorally relevant information and ignore the rest. The main goal of the thesis is to test well-established hypotheses about the mechanisms of visual selective attention in the auditory domain using behavioral and neuroimaging methods. Two fMRI studies (Experiments 1 and 2) test the hypothesis of feature-specific attentional enhancement. This hypothesis states that when attending to an object or a feature, there should be an enhancement of the response in the sensory region that is sensitive to that object or feature. Experiment 1 investigated feature-specific attentional modulation mainly within the tonotopic fields around primary auditory cortex. Experiment 2 investigated feature-specific attentional modulation mainly around non-primary auditory cortex, when attending to frequency modulation or motion of the same auditory object. Experiment 1 showed evidence for feature-specific enhancement, while Experiment 2 did not. The role of competition among concurrent auditory objects as a necessary factor in driving feature-specific enhancement is discussed. A second hypothesis from vision research is that spatial perception and attention is much more precise in the centre than in the periphery. Experiment 3 used a masking release paradigm to investigate whether the acuity of auditory spatial attention was similarly increased in the midline. Although location discrimination of sounds segregated by inter-aural time differences was more precise at the midline than at the periphery, spatial attention was not. Therefore for this task at least there was no effect of eccentricity on auditory spatial attention. The results of these three studies are discussed in view of selective attention as a flexible process that operates in different ways according to the specifics of the task.

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Beuth, Frederik. « Visual attention in primates and for machines - neuronal mechanisms ». Universitätsverlag Chemnitz, 2017. https://monarch.qucosa.de/id/qucosa%3A35655.

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Visual attention is an important cognitive concept for the daily life of humans, but still not fully understood. Due to this, it is also rarely utilized in computer vision systems. However, understanding visual attention is challenging as it has many and seemingly-different aspects, both at neuronal and behavioral level. Thus, it is very hard to give a uniform explanation of visual attention that can account for all aspects. To tackle this problem, this thesis has the goal to identify a common set of neuronal mechanisms, which underlie both neuronal and behavioral aspects. The mechanisms are simulated by neuro-computational models, thus, resulting in a single modeling approach to explain a wide range of phenomena at once. In the thesis, the chosen aspects are multiple neurophysiological effects, real-world object localization, and a visual masking paradigm (OSM). In each of the considered fields, the work also advances the current state-of-the-art to better understand this aspect of attention itself. The three chosen aspects highlight that the approach can account for crucial neurophysiological, functional, and behavioral properties, thus the mechanisms might constitute the general neuronal substrate of visual attention in the cortex. As outlook, our work provides for computer vision a deeper understanding and a concrete prototype of attention to incorporate this crucial aspect of human perception in future systems.:1. General introduction 2. The state-of-the-art in modeling visual attention 3. Microcircuit model of attention 4. Object localization with a model of visual attention 5. Object substitution masking 6. General conclusion
Visuelle Aufmerksamkeit ist ein wichtiges kognitives Konzept für das tägliche Leben des Menschen. Es ist aber immer noch nicht komplett verstanden, so dass es ein langjähriges Ziel der Neurowissenschaften ist, das Phänomen grundlegend zu durchdringen. Gleichzeitig wird es aufgrund des mangelnden Verständnisses nur selten in maschinellen Sehsystemen in der Informatik eingesetzt. Das Verständnis von visueller Aufmerksamkeit ist jedoch eine komplexe Herausforderung, da Aufmerksamkeit äußerst vielfältige und scheinbar unterschiedliche Aspekte besitzt. Sie verändert multipel sowohl die neuronalen Feuerraten als auch das menschliche Verhalten. Daher ist es sehr schwierig, eine einheitliche Erklärung von visueller Aufmerksamkeit zu finden, welche für alle Aspekte gleichermaßen gilt. Um dieses Problem anzugehen, hat diese Arbeit das Ziel, einen gemeinsamen Satz neuronaler Mechanismen zu identifizieren, welche sowohl den neuronalen als auch den verhaltenstechnischen Aspekten zugrunde liegen. Die Mechanismen werden in neuro-computationalen Modellen simuliert, wodurch ein einzelnes Modellierungsframework entsteht, welches zum ersten Mal viele und verschiedenste Phänomene von visueller Aufmerksamkeit auf einmal erklären kann. Als Aspekte wurden in dieser Dissertation multiple neurophysiologische Effekte, Realwelt Objektlokalisation und ein visuelles Maskierungsparadigma (OSM) gewählt. In jedem dieser betrachteten Felder wird gleichzeitig der State-of-the-Art verbessert, um auch diesen Teilbereich von Aufmerksamkeit selbst besser zu verstehen. Die drei gewählten Gebiete zeigen, dass der Ansatz grundlegende neurophysiologische, funktionale und verhaltensbezogene Eigenschaften von visueller Aufmerksamkeit erklären kann. Da die gefundenen Mechanismen somit ausreichend sind, das Phänomen so umfassend zu erklären, könnten die Mechanismen vielleicht sogar das essentielle neuronale Substrat von visueller Aufmerksamkeit im Cortex darstellen. Für die Informatik stellt die Arbeit damit ein tiefergehendes Verständnis von visueller Aufmerksamkeit dar. Darüber hinaus liefert das Framework mit seinen neuronalen Mechanismen sogar eine Referenzimplementierung um Aufmerksamkeit in zukünftige Systeme integrieren zu können. Aufmerksamkeit könnte laut der vorliegenden Forschung sehr nützlich für diese sein, da es im Gehirn eine Aufgabenspezifische Optimierung des visuellen Systems bereitstellt. Dieser Aspekt menschlicher Wahrnehmung fehlt meist in den aktuellen, starken Computervisionssystemen, so dass eine Integration in aktuelle Systeme deren Leistung sprunghaft erhöhen und eine neue Klasse definieren dürfte.:1. General introduction 2. The state-of-the-art in modeling visual attention 3. Microcircuit model of attention 4. Object localization with a model of visual attention 5. Object substitution masking 6. General conclusion

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Wallis, George J. « Selection mechanisms for working memory ». Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:1a9be8d6-9f8e-49af-8185-8be4c890010f.

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The experiments in this thesis investigated the mechanisms controlling input and output gating of working memory. In chapter 3, accuracy and reaction time data from a precision/capacity working memory task with prospective and retrospective cues were analysed. The results suggest that retrocues boost performance by facilitating output gating from working memory. In chapter 4, the role of perceptual cortex in mediating the cue benefits in this task was investigated with magnetoencephalography (MEG). The pattern of alpha (8-12Hz) power in visual cortex was modulated by cue direction following both precues and retrocues, but whilst this modulation was sustained following a precue (until presentation of the memory array) it was transient following a retrocue, suggesting that a memory representation was briefly retrieved or refreshed, but that there was not a sustained biasing of top-down input to visual cortex following retrocues. This argues against the standard model of working memory as sustained attention to internal representations, and in favour of a more dynamic view in which perceptual cortex is recruited transiently, and otherwise freed up for on-going processing. In chapter 5, the role of frontal networks in precueing and retrocueing was investigated. An fMRI meta-analysis identified control networks involved in preparatory and mnemonic selection: whilst the fronto-parietal network is recruited in both cases, the cingulo-opercular network is recruited only by retrocues. This spatial pattern was replicated with a source-space ROI analysis of MEG induced-responses. These data also characterised the time-course of control network activation shedding light on their functional roles. The fronto-parietal network was activated immediately following both precues and retrocues, consistent with a direct role in top-down influence over perceptual cortex. By contrast, the cingulo-opercular network was activated following retrocues only after the perceptual refreshing event was complete, suggesting a downstream role, perhaps in selecting representations to guide action. Chapter 6 investigated the role of reward associations in controlling access to working memory, testing behavioural predictions of two theories implicating the dopamine system and basal ganglia in control of working memory. The results supported a temporal gating account in which encountering reward associated items triggers a brief (<300ms) window in which there is a boost of encoding for WM. Chapter 7 discusses the implications of the current work and suggests some future directions.

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Cohen, Jason C. « Attention mechanisms and inhibition of return in the somatosensory system ». Related electronic resource : Current Research at SU : database of SU dissertations, recent titles available full text, 2002. http://wwwlib.umi.com/cr/syr/main.

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Yan, Shiyang. « Visual attention mechanism in deep learning and its applications ». Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3028892/.

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Recently, in computer vision, a branch of machine learning, called deep learning, has attracted high attention due to its superior performance in various computer vision tasks such as image classification, object detection, semantic segmentation, action recognition and image description generation. Deep learning aims at discovering multiple levels of distributed representations, which have been validated to be discriminatively powerful in many tasks. Visual attention is an ability of the vision system to selectively focus on the salient and relevant features in a visual scene. The core objective of visual attention is to achieve the least possible amount of visual information to be processed to solve the complex high-level tasks, e.g., object recognition, which can lead the whole vision process to become effective. The visual attention is not a new topic which has been addressed in the conventional computer vision algorithms for many years. The development and deployment of visual attention in deep learning algorithms are of vital importance since the visual attention mechanism matches well with the human visual system and also shows an improving effect in many real-world applications. This thesis is on the visual attention in deep learning, starting from the recent progress in visual attention mechanism, followed by several contributions on the visual attention mechanism targeting at diverse applications in computer vision, which include the action recognition from still images, action recognition from videos and image description generation. Firstly, the soft attention mechanism, which was initially proposed to combine with Recurrent Neural Networks (RNNs), especially the Long Short-term Memories (LSTMs), was applied in image description generation. In this thesis, instead, as one contribution to the visual attention mechanism, the soft attention mechanism is proposed to directly plug into the convolutional neural networks for the task of action recognition from still images. Specifically, a multi-branch attention network is proposed to capture the object that the human is intereating with and the scene in which the action is performing. The soft attention mechanism applying in this task plays a significant role in capturing multi-type contextual information during recognition. Also, the proposed model can be applied in two experimental settings: with and without the bounding box of the person. The experimental results show that the proposed networks achieved state-of-the-art performance on several benchmark datasets. For the action recognition from videos, our contribution is twofold: firstly, the hard attention mechanism, which selects a single part of features during recognition, is essentially a discrete unit in a neural network. This hard attention mechanism shows superior capacity in discriminating the critical information/features for the task of action recognition from videos, but is often with high variance during training, as it employs the REINFORCE algorithm as its gradient estimator. Hence, this brought another critical research question, i.e., the gradient estimation of the discrete unit in a neural network. In this thesis, a Gumbel-softmax gradient estimator is applied to achieve this goal, with much lower variance and more stable training. Secondly, to learn a hierarchical and multi-scale structure for the multi-layer RNN model, we embed discrete gates to control the information between each layer of the RNNs. To make the model differentiable, instead of using the REINFORCE-like algorithm, we propose to use Gumbel-sigmoid to estimate the gradient of these discrete gates. For the task of image captioning, there are two main contributions in this thesis: primarily, the visual attention mechanism can not only be used to reason on the global image features but also plays a vital role in the selection of relevant features from the fine-grained objects appear in the image. To form a more comprehensive image representation, as a contribution to the encoder network for image captioning, a new hierarchical attention network is proposed to fuse the global image and local object features through the construction of a hierarchical attention structure, to better the visual representation for the image captioning. Secondly, to solve an inherent problem called exposure-biased issue of the RNN-based language decoder commonly used in image captioning, instead of only relying on the supervised training scheme, an adversarial training-based policy gradient optimisation algorithm is proposed to train the networks for image captioning, with improved results on the evaluation metrics. In conclusion, comprehensive research has been carried out for the visual attention mechanism in deep learning and its applications, which include action recognition and image description generation. Related research topics have also been discussed, for example, the gradient estimation of the discrete units and the solution to the exposure-biased issue in the RNN-based language decoder. For the action recognition and image captioning, this thesis presents several contributions which proved to be effective in improving existing methods.

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Sock, Ching Low. « Giving centre stage to top-down inhibitory mechanisms for selective attention ». Doctoral thesis, Universitat Pompeu Fabra, 2020. http://hdl.handle.net/10803/670753.

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Selective attention determines the sensory signals that are processed at higher levels at the expense of others and is biased by higher-order brain regions which anticipate task-relevant stimuli and increase neural sensitivity to them in the sensory cortex. Often, this is thought to occur through excitation of selected neurons, but some studies have suggested that it is not the full description of the process. Increasingly, evidence has pointed to an alternative, top-down inhibitory biasing mechanism. Here, we investigated such an inhibitory model of attention. We first showed how sensitivity to stimulus features known to be task-irrelevant are reduced through top-down suppression. Secondly, we demonstrated a biologically grounded spiking model’s ability to modulate information processing and benchmarked it to physiology. Lastly, we explored the interaction between the excitatory and inhibitory models of top-down attention in a foraging agent. Our results support the inhibitory model of top-down attention as a biological attentional mechanism and show how it fits into the current zeitgeist of top-down attentional mechanisms.
L’atenció selectiva determina els senyals sensorials que es processen a nivells superiors a costa dels altres. Està esbiaixada per regions cerebrals d’ordre superior que anticipen estímuls rellevants per a la tasca i augmenten la sensibilitat neuronal a l’escorça sensorial. Sovint, es creu que això es produeix mitjançant l'excitació de neurones seleccionades, però alguns estudis han suggerit que no és la descripció completa del procés. Cada vegada més, l’evidència apunta cap a un mecanisme alternatiu de polarització inhibitiva de dalt a baix. Aquí hem investigat, aleshores, un model d’atenció inhibitori. Primer, vam demostrar com es redueix la sensibilitat a les funcions d’estímul irrellevants per tasques mitjançant la supressió de dalt a baix. En segon lloc, vam demostrar la capacitat d’un model d’espiga basat en la biologia per modular el processament de la informació i l’hem comparat amb la fisiologia. Per últim, hem explorat la interacció entre els models excitadors i inhibidors d’atenció de dalt a baix en un agent de cerca d’aliments. Els nostres resultats donen suport al model inhibitori de l’atenció de dalt a baix com a mecanisme d’atenció biològica i mostren com s’adapta al ‘zeitgeist’ actual dels mecanismes d’atenció de dalt a baix.

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Burton, Pamela Ann. « Physiological evidence of interactive object-based and space-based attention mechanisms ». Access to citation, abstract and download form provided by ProQuest Information and Learning Company ; downloadable PDF file 50.79Mb,139 p, 2005. http://wwwlib.umi.com/dissertations/fullcit/3157279.

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Cristescu, Tamara C. « Flexible mechanisms for orienting attention to words in the human brain ». Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442831.

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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/.

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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.

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Kulke, L. V. « Cortical mechanisms of visual attention in typically developing infants and adults ». Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1471117/.

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This thesis used a combined methodology of on-line eye tracking and high density EEG to study neural mechanisms of attention development in infants and adults. The extensively studied Fixation Shift Paradigm (FSP) measures the ability to shift attention between two stimuli (competition) or towards one single visible stimulus (non-competition) which improves during infancy. The novel method here overcame a number of methodological challenges to measure event-rated potentials during overt shifts of attention in competition and non-competition conditions. An experiment used eye tracking to test infants between 1 and 8 months on the FSP, establishing that this automated measure is suitable for non-verbal populations and adds precision to the developmental trends previously reported. An experiment successfully combined eye tracking and EEG to record patterns of brain activity during covert and overt attention shifts in adults. It found that neural mechanisms previously studied in covert attention shifts are similar to those in overt shifts, but differ in a frontal positivity, possibly reflecting saccade inhibition. Combined eye tracking and EEG with the original FSP showed that similar cortical mechanisms are involved in attention shifts under competition and non-competition conditions but that occipital response latencies differ at an early stage, reflecting the behavioural pattern of shorter latencies in non-competition conditions. Parallel measurements during infancy showed that the lateralisation of frontal brain responses coincides with developmental improvements in the ability to shift attention. In conclusion, the work demonstrates that, with suitable precautions taken to avoid artefacts, eye tracking and EEG can be successfully combined to monitor group-level brain mechanisms during overt attention shifts. Neurodevelopmental changes have been identified that underpin the increasing efficiency of neural attention pathways during infancy, and increased automation of responses from reliance on frontal pathways in infancy to occipital pathways in adulthood.

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Isunza, Navarro Abgeiba Yaroslava. « Evaluation of Attention Mechanisms for Just-In-Time Software Defect Prediction ». Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-288724.

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Just-In-Time Software Defect Prediction (JIT-DP) focuses on predicting errors in software at change-level with the objective of helping developers identify defects while the development process is still ongoing, and improving the quality of software applications. This work studies deep learning techniques by applying attention mechanisms that have been successful in, among others, Natural Language Processing (NLP) tasks. We introduce two networks named Convolutional Neural Network with Bidirectional Attention (BACNN) and Bidirectional Attention Code Network (BACoN) that employ a bi-directional attention mechanism between the code and message of a software change. Furthermore, we examine BERT [17] and RoBERTa [57] attention architectures for JIT-DP. More specifically, we study the effectiveness of the aforementioned attention-based models to predict defective commits compared to the current state of the art, DeepJIT [37] and TLEL [101]. Our experiments evaluate the models by using software changes from the OpenStack open source project. The results showed that attention-based networks outperformed the baseline models in terms of accuracy in the different evaluation settings. The attention-based models, particularly BERT and RoBERTa architectures, demonstrated promising results in identifying defective software changes and proved to be effective in predicting defects in changes of new software releases.
Just-In-Time Defect Prediction (JIT-DP) fokuserar på att förutspå fel i mjukvara vid ändringar i koden, med målet att hjälpa utvecklare att identifiera defekter medan utvecklingsprocessen fortfarande är pågående, och att förbättra kvaliteten hos applikationsprogramvara. Detta arbete studerar djupinlärningstekniker genom att tillämpa attentionmekanismer som har varit framgångsrika inom, bland annat, språkteknologi (NLP). Vi introducerar två nätverk vid namn Convolutional Neural Network with Bidirectional Attention (BACNN), och Bidirectional Attention Code Network (BACoN), som använder en tvåriktad attentionmekanism mellan koden och meddelandet om en mjukvaruändring. Dessutom undersöker vi BERT [17] och RoBERTa [57], attentionarkitekturer för JIT-DP. Mer specifikt studerar vi hur effektivt dessa attentionbaserade modeller kan förutspå defekta ändringar, och jämför dem med de bästa tillgängliga arkitekturerna DeePJIT [37] och TLEL [101]. Våra experiment utvärderar modellerna genom att använda mjukvaruändringar från det öppna källkodsprojektet OpenStack. Våra resultat visar att attentionbaserade nätverk överträffar referensmodellen sett till träffsäkerheten i de olika scenarierna. De attentionbaserade modellerna, framför allt BERT och RoBERTa, demonstrerade lovade resultat när det kommer till att identifiera defekta mjukvaruändringar och visade sig vara effektiva på att förutspå defekter i ändringar av nya mjukvaruversioner.

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Baker, Christopher A. « Differentiating attention and motor system-based mechanisms underlying concealed knowledge detection / ». Diss., Digital Dissertations Database. Restricted to UC campuses, 2008. http://uclibs.org/PID/11984.

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Lisi, Matteo. « Mechanisms of top-down visual spatial attention : computational and behavioral investigations ». Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3423038.

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This thesis examines the mechanisms underlying visual spatial attention. In particular I focused on top-‐down or voluntary attention, namely the ability to select relevant information and discard the irrelevant according to our goals. Given the limited processing resources of the human brain, which does not allow to process all the available information to the same degree, the ability to correctly allocate processing resources is fundamental for the accomplishment of most everyday tasks. The cost of misoriented attention is that we could miss some relevant information, with potentially serious consequences. In the first study (chapter 2) I will address the issue of the neural substrates of visual spatial attention: what are the neural mechanisms that allow the deployment of visual spatial attention? According to the premotor theory orienting attention to a location in space is equivalent to planning an eye movement to the same location, an idea strongly supported by neuroimaging and neurophysiological evidence. Accordingly, in this study I will present a model that can account for several attentional effects without requiring additional mechanisms separate from the circuits that perform sensorimotor transformations for eye movements. Moreover, it includes a mechanism that allows, within the framework of the premotor theory, to explain dissociations between attention and eye movements that may be invoked to disprove it. In the second model presented (chapter 3) I will further investigate the computational mechanisms underlying sensorimotor transformations. Specifically I will show that a representation in which the amplitude of visual responses is modulated by postural signal is both efficient and plausible, emerging also in a neural network model trained through unsupervised learning (i.e., using only signals locally available at the neuron level). Ultimately this result gives additional support to the approach adopted in the first model. Next, I will present a series of behavioral studies: in the first (chapter 4) I will show that spatial constancy of attention (i.e., the ability to sustain attention at a spatial location across eye movements) is dependent on some properties of the image, namely the presence of continuous visual landmarks at the attended locations. Importantly, this finding helps resolve contrasts between several recent results. In the second behavioral study (chapter 5), I will investigate an often neglected aspect of spatial cueing paradigms, probably the most widely used technique in studies of covert attention: the role of cue predictivity (i.e. the extent to which the spatial cue correctly indicates the location where the target stimulus will appear). Results show that, independently of participant’s awareness, changes in predictivity result in changes in spatial validity effects, and that reliable shifts of attention can take place also in the absence of a predictive cue. In sum the results question the appropriateness of using predictive cues for delineating pure voluntary shifts of spatial attention. Finally, in the last study I will use a psychophysiological measure, the diameter of the eye’s pupil, to investigate intensive aspects of attention. Event-‐related pupil dilations accurately mirrored changes in visuospatial awareness induced by a dual-‐task manipulation that consumed attentional resources. Moreover, results of the primary spatial monitoring task revealed a significant rightward bias, indicated by a greater proportion of missed targets in the left hemifield. Interestingly this result mimics the extinction to double simultaneous stimulation (i.e., the failure to respond to a stimulus when it is presented simultaneously with another stimulus) which is often found in patients with unilateral brain damage. Overall, these studies present an emerging picture of attention as a complex mechanism that even in its volitional aspects is modulated by other non-‐volitional factors, both external and internal to the individual
Questa tesi verte sull’indagine dei meccanismi alla base dell'attenzione visuo-‐spaziale e In particolare sull'attenzione top-‐down. Con questo termine si intende la capacità di selezionare le informazioni rilevanti e scartare quelle irrilevanti in maniera volontaria e sulla base dei nostri obiettivi. Il cervello umano non è in grado di processare allo stesso livello tutte le informazioni disponibili nell’ambiente in un dato momento, per questo una selezione corretta dell’informazione da elaborare è fondamentale anche per l’esecuzione delle più semplici attività quotidiane. Prestare attenzione ad informazioni irrilevanti può farci trascurare altre informazioni di importanza cruciale, con conseguenze potenzialmente gravi. Nel primo studio (capitolo 2) I affronterò con un approccio computazionale la questione dei meccanismi neurali che sottendono l’attenzione visuo-‐spaziale: quali sono le basi neurali dell’attenzione visuo-‐spaziale? Secondo la teoria premotoria, orientare l'attenzione verso una specifica posizione spaziale equivale a preparare un movimento oculare verso la medesima posizione, un’ipotesi supportata dai risultati di molteplici studi di neuroimaging e neurofisiologici, i quali hanno mostrato una notevole sovrapposizione tra i circuiti dedicati all’attenzione visiva e la programmazione di movimenti oculari. In questo capitolo presenterò un modello computazionale in grado di spiegare diversi effetti attentivi senza richiedere l’aggiunta di meccanismi specifici oltre ai circuiti oculomotori. Inoltre include un meccanismo, modellato sulla base di dati neurofisiologici, che consente di anticipare le conseguenze sensoriali di un movimento oculare sulla rappresentazione spaziale interna al modello, e di spiegare alcune recenti dimostrazioni di dissociazione tra attenzione e movimenti oculari che possono essere utilizzate per confutare la teoria premotoria. Nel capitolo successivo presenterò un secondo modello computazionale (capitolo 3) con lo scopo di investigare ulteriormente i meccanismi computazionali alla base delle trasformazioni sensorimotorie, cioè i processi che traducono l’informazione sensoriale in appropriati comandi motori. In particolare mostrerò che una rappresentazione spaziale costituita da neuroni con campi recettivi retinocentrici ,modulati in ampiezza da un segnale posturale, è sia efficiente (al fine di trasformare l’informazione visiva in coordinate motorie centrate su un effettore) che plausibile, in quanto emerge in un modello di rete neurale addestrato in maniera non supervisionata (usando cioè solo segnali disponibili localmente a livello del singolo neurone). Questo risultato supporta inoltre l’approccio utilizzato nel primo modello presentato. Successivamente presenterò una serie di studi comportamentali: nel primo (capitolo 4), mostrerò che la costanza spaziale dell’attenzione visiva rispetto ai movimenti oculari (cioè la capacità di mantenere stabilmente l'attenzione in un punto nello spazio attraverso successivi movimenti oculari), dipende fortemente da alcune proprietà dell'immagine, vale a dire la presenza continua di punti di riferimento visivi. Questo risultato aiuta a risolvere recenti controversie sull’orientamento dell’attenzione durante movimenti oculari. Nel secondo studio comportamentale (capitolo 5), indagherò un aspetto spesso trascurato relativo al paradigma di cueing spaziale (probabilmente la tecnica più utilizzata nello studio dell’attenzione spaziale): la predittività del cue (cioè la misura in cui il cue spaziale indica correttamente la posizione in cui apparirà lo stimolo bersaglio). I risultati mostrano che, indipendentemente dalla consapevolezza dei partecipanti, variazioni nella predittività producono corrispondenti variazioni degli effetti di validità del cue, e che effetti significativi di validità possono comparire anche in assenza di un cue predittivo o direzionale. Questi risultati mettono in dubbio l’appropriatezza dell’uso di cue predittivi per indagare spostamenti volontari dell’attenzione spaziale. Infine, nell'ultimo studio userò una misura psicofisiologica, il diametro della pupilla, per indagare gli aspetti relativi all’intensità del processamento visuospaziale. In particolare mostrerò come dilatazioni della pupilla evento-‐relate riflettano accuratamente variazioni nella performance in un compito di monitoraggio spaziale provocate dall’aggiunta di un doppio-‐compito. Inoltre, i risultati del compito primario spaziale rivelano la presenza di un bias consistente verso l’emispazio di destra, indicato da una percentuale maggiore di bersagli omessi nell’emispazio di sinistra. In particolare il pattern di errori rispecchia il fenomeno dell’estinzione (mancata risposta a uno stimolo quando è presentata simultaneamente con un secondo stimolo, tipicamente nell’emispazio opposto) che si trova spesso in pazienti con danno cerebrale unilaterale. In conclusione, dagli studi presentati emerge un quadro dell’attenzione volontaria visuo-‐spaziale come un meccanismo complesso, che, anche nei suoi aspetti volitivi è fortemente influenzato da altri fattori, non volitivi, sia esterni che interni all'individuo

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Hayes, Taylor Ray. « Mechanisms of Visual Relational Reasoning ». The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1416933187.

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Highlander, Tyler Clayton. « Conditional Dilated Attention Tracking Model - C-DATM ». Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1564652134758139.

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Koleszar, Thomas W. « The generation of IPDP micropulsations, with special attention to frequency shift mechanisms ». Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29132.

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Short period geomagnetic micropulsations termed IPDPs (Intervals of Pulsations of Diminishing Period) are investigated using ground station data, geosynchronous satellite magnetograms, and the Kp and Dst geomagnetic indices. A model for the generation of IPDPs is described, and consideration is given to three mechanisms which could be responsible for the IPDP frequency rise: the inward motion, azimuthal drift, and increasing background magnetic field mechanisms. A simplified IPDP generation model containing the first two of these mechanisms is tested by computer simulation. Results from this simulation indicate the possibility of significant source region inward motion without actual plasmapause displacement, and the possibility of eastward developing IPDPs. Using amplitude variations along a north-south line of ground stations, two methods, each applicable under different ionospheric propagation conditions, are developed for quantitatively determining the inward motion of the IPDP source region. A system for qualitatively determining the potential influence of the increasing background field mechanism on an IPDP using the Dst index and geosynchronous satellite magnetograms is also formulated. Lastly, a technique for the assessment of the effects of the azimuthal drift mechanism, in conjunction with the inward motion mechanism, is developed. This technique assumes that only these two mechanisms are operating. In addition to addressing the frequency shift mechanisms, it provides estimates of the injection boundary position and the magnitude of any (ring current created) magnetic field depression in the IPDP source region. The frequency rises of two IPDPs are analyzed in detail using these methods. In both cases, the inward motion effect is the dominant factor in producing the frequency rise, with the increasing background field mechanism having no significant effect. The azimuthal drift mechanism is a secondary factor in creating one event's frequency rise, and actually suppresses the frequency rise of the other event. The computer simulation calculations also generally show the inward motion mechanism to be the dominant effect in producing IPDP frequency rises. Longitudinal variations within an IPDP event are also examined. The results of this examination are consistent with the IPDP generation model used here, which includes showing significant variations between stations spaced comparatively closely in longitude.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate

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West, Vicki Hopfinger Joseph B. « Comparisons of the neural mechanisms of voluntary, reflexive, and socially-directed attention ». Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,747.

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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.
Title from electronic title page (viewed Dec. 18, 2007). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Psychology." Discipline: Psychology; Department/School: Psychology.

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Carmel, David Podhorzer. « Top-down control of visual attention and awareness : cognitive and neural mechanisms ». Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1444603/.

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Recent behavioural and neural research suggests that awareness is intimately related to top-down cognitive functions such as attention. Here I present a characterization of this relationship, guided by Lavie's load theory. Load theory proposes that perception has limited capacity but proceeds automatically on all stimuli (whether relevant to the task at hand or not) until capacity is exhausted, and that the allocation of processing resources to certain stimuli (rather than to other, competing ones) is guided by executive control functions such as working memory. The theory predicts that increasing the perceptual load of a task will consume capacity, therefore reducing processing of stimuli external to that task it also predicts that increasing working memory load will impair executive control, leading to increased processing of salient ignored stimuli. Here I show that these predictions hold not only for indirect measures of perceptual processing, as has been demonstrated previously, but also for visual awareness - the subjective experience of seeing and being able to report the nature of a visual stimulus. I find that under high perceptual load, observers become less aware of the very presence of other stimuli, even when these stimuli are fully expected and serve as targets. I also show that perceptual load affects the temporal resolution of visual awareness - under high load, the ability to detect a temporal pattern (luminance flicker) is reduced, leading to a subjective percept of steady illumination. In a neuroimaging study, I show that subjective awareness of flicker is associated with activity in frontal and parietal brain regions previously associated with attention and awareness. Next, I investigate the role of executive control in visual awareness by examining the effect of working memory load on binocular rivalry, a fundamental form of visual competition. I find that high working memory load reduces dominance durations in rivalry, suggesting that working memory may serve to maintain perceptual biases during competitive interactions in visual awareness. Finally, I use Transcranial Magnetic Stimulation to establish a causal role for the previously described right parietal involvement in the control of binocular rivalry. This research therefore indicates that top- down cognitive and neural mechanisms are involved in determining whether visual stimuli will reach awareness, and in shaping the subjective nature of the experience such stimuli evoke.

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MacNamara, Kailey. « Behavioral and Neural Mechanisms of Social Heterogeneity in Attention Deficit/Hyperactivity Disorder ». FIU Digital Commons, 2017. http://digitalcommons.fiu.edu/etd/3390.

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Attention-deficit/hyperactivity disorder (ADHD) is one of the most common child-onset neurodevelopment disorders, affecting 5% of children in the United States (American Psychiatric Association, 2013). Treatment matching in ADHD is difficult and unsatisfactory; the same general treatment algorithm is recommended for all children. It is therefore important to consider the development of specialized treatment programs based on a variety of behavioral and neurological biomarkers. Unfortunately, due to its multi-faceted classification, the heterogeneity of this behavioral disorder is under-investigated (Costa Dias et al., 2015). Scientific research in this area is especially limited as the severity of ADHD goes undiagnosed, children tend to have difficulties remaining still in MRI scanners, and the hyperactivity-impulsivity that is associated with ADHD may cause further challenges when trying to remain motionless in the scanner. Furthermore, tasks such as Facial Emotion Perception Task (FEPT) and Theory of Mind (ToM) have not been used to analyze social and behavioral deficits in children with ADHD. More research needs to be allocated to helping uncover the neural substrates underlying the inattention and hyperactivity traits of this disorder. For this reason, we acquired functional magnetic resonance imaging (fMRI) data from five children with ADHD performing the FEPT and ToM tasks. The results showed the children have an easier and quick time correctly identifying happy emotional states, as compared to the fearful, angry, and neutral conditions. Results from the FEPT task also revealed that the participants were thinking and reasoning more (i.e., taking longer to deduce an ending) when identifying emotions than identifying animals. The ToM task showed that the default mode network (DMN) may not be fully suppressed when the children are choosing the correct cartoon ending, and therefore the children may be having lapses in attention. These findings may assist the current hypothesis that the default mode network has reduced network homogeneity in people with ADHD. Overall, the findings presented in this thesis provide a good diving board into discovering the reason(s) for the social cognition and emotion recognition impairments associated with ADHD, but further research is needed in order to one day pinpoint and ultimately correct the regions(s) of dysfunction.

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Walters-Symons, Rosanna Mary. « Attention, gaze, response programming : examining the cognitive mechanisms underpinning the quiet eye ». Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/28336.

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The quiet eye (QE) - the final fixation or tracking gaze on a specific location that has an onset prior to the start of a final, critical movement (Vickers, 2007) - has emerged as a key predictor of proficient performance in targeting and interceptive tasks over the last 20 years. Since Vickers’ seminal study in golf putting, the QE has been examined in over 28 different motor tasks, with a longer QE duration often referred to as a characteristic of superior performance and a measure of optimal visuo-motor control. However, the underpinnings of QE are not fully understood, with many researchers advocating the need to better identify and understand the mechanisms that underlie the QE (Williams, 2016; Gonzalez et al., 2015). Consequently, the overriding goal of this thesis was to examine the function of the QE duration, what it represents and how it exerts an influence, by exploring the attentional underpinnings of the QE and the prominent cognitive mechanism of response programming. In study 1 (chapter 4), the manipulation of different parameters of golf putting and the examination of different response programming functions (pre-programming vs online control) during the QE enabled me to build on previous explorations of the response programming function by investigating QE’s response to specific iterations of increased task demands. Experienced golfers revealed that longer QE durations were found for more complex iterations of the task and more sensitive analyses of the QE proportions suggest that the early QE (prior to movement initiation) is closely related to force production and impact quality. While the increases in QE were not functional in terms of supporting improved performance, the longer QE durations may have had a positive, insulating effect. In study 2 (chapter 5), a re-examination of Vickers’ seminal work in golf putting was performed, taking into account an error recovery perspective. This 3 explored the influence of trial-to-trial dependence on the functionality of the QE duration and the possible compensatory mechanism that assists in the re-parameterisation of putting mechanics following an unsuccessful trial. The results reveal that experienced golfers had consistently longer QE durations than novices but there was no difference in QE between randomly chosen hits and misses. However, QE durations were significantly longer on hits following a miss, reflecting a potential error recovery mechanism. Importantly, QE durations were significantly lower on misses following a miss, suggesting that motivation moderates the adoption of a compensatory longer QE strategy. These findings indicate that the QE is influenced by the allocation of attentional effort. To explore this notion further, in study 3 (chapter 6), two experiments were undertaken. Experiment 1 examined the QE’s response to attentional effort that is activated via goal motivation and experiment 2 examined the effect of disrupting the allocation of attentional effort on the QE using a dual-task paradigm. The early proportion of the QE was sensitive to motivation, indicating that the QE is not purely determined by the demands of the task and golfers have the ability to apply attentional effort, and therefore QE, strategically (exp. 1). The results also support the assumption that QE reflects overt attentional control but question the sensitivity of QE to detect movements in the locus of attentional effort that does not activate shifts in gaze (covert attention) (exp. 2). The results in this thesis conclude that, while significant contributions to understanding what the QE represents and how it may exert its influence are made, there still remains unanswered questions and tensions that require exploration.

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O'Dea, Namrita Kumar. « Fatigue mechanisms in sedentary and endurance trained adults : effects of nutritional countermeasures ». Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53584.

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Physical inactivity is a major risk factor for chronic disease; yet the majority of the population does not meet physical activity recommendations, with fatigue being a primary underlying reason. Common nutritional supplements such as caffeine (CAF) and carbohydrate (CHO) are frequently taken prior to and during exercise and can delay fatigue, particularly in trained athletes; but, whether these same reductions in fatigue translate to habitually sedentary individuals is less clear. The main goal of this research was to investigate the influence of nutritional aids: CAF, low-calorie CHO, and their combination CAF+CHO to delay physical and mental fatigue in healthy but sedentary men and women compared to endurance-trained counterparts. The minimum amount of CHO that could elicit a benefit without eliciting a metabolic response when ingested remains unclear. Thus, our first aim was to evaluate glycemic response after ingestion of CHO drinks ranging from 0-6% CHO; and, to determine effects of two methods of CHO administration (ingest and oral rinse without ingestion) on sustained attention during a mentally fatiguing cognitive task. In agreement with evidence that “low calorie beverages” do not appear to alter blood glucose, a 0.4% CHO solution (<2 g CHO) elicited the most similar response to artificially sweetened placebo and was evaluated further. Compared to oral rinse of a small amount (<2 g) of CHO or control (0 g CHO), ingestion of an equivalent “dose” (<2 g CHO) in the 0.4% CHO solution maintained sustained attention, providing evidence that ingesting a low-CHO drink may be more effective than simply rinsing, in a fasted state. Oral rinse of CHO did not, however, provide any benefit compared to rinsing a control solution. Our second aim was to evaluate the efficacy of ingesting a moderate dose of CAF (3 mg/kg), low-CHO, and the combination of CAF+CHO on exercise capacity in trained (ET) versus sedentary (SED) groups. As expected, CAF reduced perceived effort during exercise and increased endurance capacity (longer total time to volitional fatigue and longer duration before rating vigorous intensity exercise as “very hard”), for ET and SED. However, addition of <2 g CHO did not provide further improvement with CAF; or any benefit when ingested alone, compared to placebo. CAF and CHO did not influence blood glucose but CAF resulted in higher blood lactate compared to no-CAF. As expected, ET had higher fat oxidation than SED; and, CAF increased CHO oxidation but not fat oxidation. CAF tended to maintain maximal voluntary contractile (MVC) strength in the quadriceps after exercise; but, CAF did not influence voluntary muscle activation or appear to have a direct effect on skeletal muscle since electrically evoked strength was not altered with CAF. Since acute exercise also benefits cognition independent of CAF or CHO, our third aim was to determine: (1) the effect of moderate intensity exercise (MOD-EX) on sustained attention in comparison to seated rest; and 2) whether CAF provides additional benefit to sustained attention and perceptual measures when combined with exercise. As expected, compared to an equivalent duration of rest, MOD-EX improved sustained attention following mental fatigue in both groups; and, when coupled with CAF, provided greater benefit to sustained attention and perceived mental energy. Although CAF’s beneficial effect on sustained attention persisted after exercise to volitional fatigue, it did not improve perceptual measures of reduced mental energy and increased mental fatigue at the point of physical fatigue. Our research investigated nutritional aids that are not only beneficial for athletes, but also widely consumed by the general population despite their lack of regular physical activity. In response to public health recommendations for reducing sugar intake, low-sugar/low-calorie drinks have been heavily marketed to the population despite much research to support their efficacy. Our findings suggest that low-CHO can be ergogenic during a sedentary mental task in a fasted state, perhaps through central mechanisms. Although CHO mouth rinse is evidenced to be efficacious for exercise performance without ingestion, we did not find that ingestion of low-CHO provides any significant benefit during moderate to vigorous exercise following a small meal. However, a moderate dose of CAF was ergogenic for both ET and SED. Future work should not only investigate additional exercise interventions; but also different CHO and CAF doses and administration protocols, and their relative metabolic implications.

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Bretherton, Paul. « The neural mechanisms of attention : exploring threat-related suppression and enhancement using ERPs ». Thesis, University of Roehampton, 2016. https://pure.roehampton.ac.uk/portal/en/studentthesis/the-neural-mechanisms-of-attention(87e183ac-3a36-40e6-9c69-91f7c1209e87).html.

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The capacity of the visual system to process information about multiple objects at any given moment in time is limited. This is because not all information can be processed equally or in parallel and subsequently reach consciousness. Previous research has utilized behavioural experiments to explore visual attention. More recently research, however, has used electroencephalography (EEG) to measuring the electrical brain activity in the posterior scalp. By time locking visual stimulus events to fluctuations in scalp activity researchers have been able to estimate the time course of attentional changes by measuring changes in these event-related potentials (ERP). One component in particular (N2pc) has been a reliable tool in measuring either the suppression of, or the shift of attentional to, both ignored and attended items in the visual scene. The N2pc is measured by comparing the ERP activity contralateral and ipsilateral to the visual field of interest. More recently, evidence has been presented that the mechanisms of attention thought to be represented by the N2pc (suppression and attentional selection) could be separated into different ERP components (Pd: indexing attentional suppression of an ignored item; and Nt: indexing attentional selection of the target) and measured independently. In six experiments, using ERPs, this thesis employs these components to explore the mechanisms and strategies of the human attentional system. Additionally, this thesis focuses on the impact of different types of simultaneous processing load on the attentional system and how the mechanisms of this system are influenced. Experiment 1 explores the idea that the type or valence of information to be ignored may influence the ability to suppress it. Results of this experiment 4 show that neither the type nor valence of the irrelevant information modulated the amplitude of the distractor positivity (Pd), indicating suppression of the irrelevant distractor was not altered. Noted in experiment 1 was also the presence of an early negativity (Ne) that appeared to represent attentional capture of the ignored lateral stimulus. Experiment 2 demonstrated that the valence of the lateral target did not alter the target negativity (Nt), indicating a different pattern of results between the Nt and the N2pc reported in previous studies (e.g. Eimer & Kiss, 2007; Feldmann-Wüstefeld et al., 2010). Experiment 2 also showed a similarity of the target negativity (Nt) to the early negativity (Ne; the N2pc like component observed in exp 1) toward face and non-face stimuli. This comparison supported the idea that the early negativity (Ne) reflected attentional capture of the ignored lateral distractor and as a result was relabelled the distractor negativity (Nd) in subsequent experiments. Experiment 3 showed that the salience of the lateral image did not modulate the Pd as should be the case if the Pd reflected sensory-level processing. An early contralateral negativity (similar to the Nd observed in exp 1) was altered by the salience of the distractor which added support to the hypothesis that this reflects attentional capture of the lateral ignored image. Experiment 4 attempted to manipulate working memory (WM) to assess the effect of WM load on attentional capture and suppression. While the results did indicate modulation of suppression under WM load, the limitations of the design of experiment 4 made any definitive interpretation of the results unreliable. The results of experiment 5 showed that suppression, as indexed by the Pd, was not altered by cognitive load. However, reductions in attentional capture under high cognitive load, as indexed by the distractor negativity (Nd), were observed and contradict the results of previous experiments (c.f. Lavie & De Fockert, 2005) 5 where cognitive load resulted in an increase in attentional capture. Although, there appears to be some issue in the authors interpretation of the results of these experiments (see chapter 6 for discussion). The results of Experiment 6 show the opposite effect with a significant increase in the laterality of the Pd under high perceptual load. A similar increase in the laterality of the Pd was not reflected in terms of valence though, where suppression of threat related distractors was not altered under high perceptual load. The hypothesis that an increase in perceptual load will result in a decrease in attentional capture was generally supported by the results of experiment 6. Under high perceptual load angry face distractors captured attention, as indexed by the laterality of the Nd, with neutral face distractors showing a reduction in attentional capture. While under low perceptual load, both angry and neutral face distractors resulted in a significant (and similar) laterality of the Nd. The thesis concludes by discussing issues concerning Lavie’s Load Theory of attention and outlines some potential misinterpretations of previous data that have led to the proposal that cognitive load results in a decrease in attentional resources and therefore a decrease in attentional capture of ignored stimuli. It is argued in this thesis that the results of Lavie and de Fockert (2005), which concluded that the increase in cognitive load resulted in a decrease in attentional capture, are more likely to be due to changes in attentional capture (i.e. a reduction) and changes in RT (i.e. an increase), under cognitive load being separate responses to the availability of resources, one that focusses attention on the goal directed task and the other that results in extended processing time to carry out the more difficult task. In this case both ‘changes’ appear to work to prioritise resources in favour of the goal directed task.

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Stephenson, Lisa. « Follow my lead : behavioural and neural mechanisms of gaze leading in joint attention ». Thesis, University of East Anglia, 2018. https://ueaeprints.uea.ac.uk/68417/.

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Monitoring others’ actions, and our control over those actions, is essential to human social reciprocity. One such everyday social interaction is joint attention when one person follows another’s direction of gaze to a referent object. When initiating joint attention (also known as “gaze leading”), reciprocal gaze responses must be processed rapidly. Therefore, we need to detect and sense agency over these social outcomes. If we cause an outcome, a compression of perception of time occurs between our action and its outcome. This phenomenon is termed temporal binding (also called intentional binding), believed to evidence an implicit sense of agency. Using a temporal binding paradigm, Experiments 1-5 evidence an implicit sense of agency for gaze shift responses to gaze leading. Using an old/new recognition paradigm, Experiments 6-7 evidence equal, high performance for recognition of unfamiliar faces for both previously encountered congruent and incongruent gaze responses to gaze leading. Experiment 8 employed electroencephalography to explore whether the neural system differentiates congruency of gaze shift elicited by gaze leading, finding, for the first time, N170-like evidence of this. Combining previous literature and the new findings in this thesis, a new neuro-cognitive model of joint and shared attention is proposed. This encapsulates the processes at work for both the gaze leader and gaze follower, the associated neural mechanisms and the subsequent social cognition processes which can ensue.

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Raafat, R. M. « Attention and automaticity in social judgments from facial appearance : cognitive and neural mechanisms ». Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1468622/.

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Recent evidence from behavioural and cognitive-neuroscience experiments has already yielded exciting discoveries into how we might code, process and perform judgments of facial social stimuli (indeed research into the latter provides a good vehicle for examining vision and object recognition in general). Nevertheless, the evidence regarding the role of top down control in face processing and the significance of the role of attentional capacity limits is contradictory or indeed absent in certain facial social trait judgments such as trustworthiness. In this thesis, I seek to present a portrayal of these roles, directed by load theory. Load theory suggests that perception has limited capacity but proceeds automatically on all stimuli until capacity is exhausted. Whether this process applies to arguably exceptional stimulus classes such as faces is contentious. Moreover, how this is related to social facial judgments such as trustworthiness, as compared to other evaluations such as threat and dominance judgments is unknown, as up until now, research on face-attention interactions has focused on directing visuospatial attention to emotional visual information rather than to facial trait judgments such as trustworthiness. In spite of this, the theory's predictions are clear; increasing the perceptual load of a task should consume capacity, thereby reducing processing of stimuli external to that task. Here I show that these predictions hold only for certain types of facial image evaluations but not for others. In a series of experiments that applied load theory, employing a combined visual search and face judgment task (where the level of attentional load in the search task was manipulated by varying the search set size of similar non-target letters), I find that under high perceptual load, observers become moderately less able to classify certain facial targets e.g. trustworthy ones as compared to dominant ones, even when these stimuli are fully expected and serve as targets. I also show the robustness of perceptual load effects by countering possible confounds and alternative explanations. Potential order effects are countered by reversing the order of the experiment, indicating that a possible attenuated short term memory imprint for the facial stimuli does not change the pattern of results previously experimentally demonstrated. Additionally, I find that high working memory load does not reduce social judgment evaluations under load, suggesting that perceptual biases during competitive interactions in visual processing are causative of the earlier demonstrated load effects. Following on from the modest but resilient results for trustworthiness modulation experimentally demonstrated here, the issue of bias for trustworthiness judgments is addressed in a signal detection paradigm (allowing bias to be discounted as a likely explanation of load effects). In the wake of the relatively robust results for trustworthiness perceptual load modulation, a new avenue for trustworthy judgments under attention is explored, investigating the possible role of dopamine in such evaluations in a clinical cohort of Parkinson's disease (PD) patients (as contrasted to age matched controls). PD has been linked with facial expression judgment impairment, although, this impairment could be subordinate to other cognitive processes enmeshed in facial evaluation, such as selective attention. Our results once again point to a pervasive role for perceptual load modulation of facial judgments, rather than a specific attentional deficit of PD. Finally, I explore the neurobiological correlates associated with facial social evaluations under perceptual load. In a neuroimaging study, I show neural responses to trustworthy facial images interact with attentional demands, demonstrating reduced activity under high perceptual load. I found high load only affects the facial components of trustworthiness (as compared to neutral faces) in cortical areas involved in social and facial processing (but not the facial signal components of untrustworthiness as compared to their neutral counterparts). The effects of load being specific to the trustworthy aspects of faces coheres with earlier presented behavioural results. As a final point, the demonstrated findings of negative-linear effects in the amygdala are consistent with prior research underlining the role of the amygdala in facial trustworthy judgments. This research presented here, although subtle in some experiments, provides convergent evidence that top-down cognitive and neural mechanisms are involved in influencing the degree to which facial visual judgments are processed. The results demonstrate the role of attentional modulation in facial social judgments and illuminate a possible role of perceptual load and attention in the facial automaticity debate. Both the type of facial judgment and category of facial valence are factors which determine the efficacy of perceptual load effects in facial evaluations.

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Martel, Michelle M. « Hormonal associations with childhood ADHD and associated trait and neuropsychological mechanisms ». Diss., Connect to online resource - MSU authorized users, 2007.

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Parker, Amanda Louise. « A cross-modal investigation into the relationships between bistable perception and a global temporal mechanism ». Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/9545.

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When the two eyes are presented with sufficiently different images, Binocular Rivalry (BR) occurs. BR is a form of bistable perception involving stochastic alternations in awareness between distinct images shown to each eye. It has been suggested that the dynamics of BR are due to the activity of a central temporal process and are linked to involuntary mechanisms of selective attention (aka exogenous attention). To test these ideas, stimuli designed to evoke exogenous attention and central temporal processes were employed during BR observation. These stimuli included auditory and visual looming motion and streams of transient events of varied temporal rate and pattern. Although these stimuli exerted a strong impact over some aspects of BR, they were unable to override its characteristic stochastic pattern of alternations completely. It is concluded that BR is subject to distributed influences, but ultimately, is achieved in neural processing areas specific to the binocular conflict.

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Magimairaj, Beula M. « Attentional mechanisms in children's complex memory span performance ». Ohio : Ohio University, 2010. http://www.ohiolink.edu/etd/view.cgi?ohiou1267650640.

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Chen, Guozhang. « Dynamical and computational mechanisms of biological and artificial neural circuits ». Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23710.

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Spatiotemporal activity dynamics with criticality have been widely observed in the cortex. In this thesis, we focus on elucidating the fundamental computational roles of these critical circuit dynamics in both biological and artificial neural networks. We first propose a novel neural computation mechanism, Computing by Modulating Spontaneous Activity (CMSA), for understanding visual perception. Using biophysically plausible circuit models, we demonstrate that spontaneous activity patterns with criticality are modulated by external stimuli to give rise to neural responses. We find that CMSA mechanism of generating neural responses provides profound computational advantages, such as speeding up cortical processing. CMSA mechanism provides a unifying explanation for many experimental findings at both the single-neuron and circuit levels. We further demonstrate that dynamical wave patterns, emerging from the non-equilibrium critical regime of a new type of models that integrate essential structural and neurophysiological properties of cortical circuits, exhibit Lévy walk-like movement. Such Lévy dynamics modulated by salient inputs provide a mechanistic account of recent key experimental findings on spatial attention sampling, including the theta-band sampling rate, theta-gamma coupling. This dynamical mechanism of attention, when applied to natural stimuli, can better explain the attention maps and attention sampling paths found in psychophysical studies than the classical winner-take-all model of attention. Finally, we demonstrate that Lévy walk-like learning dynamics also emerge from deep neural networks trained with stochastic gradient descent (SGD) algorithm, and that such learning dynamics enable the SGD optimizer to escape from local minima. This discovery of deep learning provides a framework for understanding the strengths and weaknesses of different network architectures and the development of new learning methods.

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Patriquin, Michelle A. « Music and Children with Autism Spectrum Disorders : Potential Autonomic Mechanisms of Social Attention Improvement ». Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/77008.

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Autism Spectrum Disorders (ASD) are an urgent health concern as new reports indicate approximately 1 in 110 children are affected by ASD (Centers for Disease Control and Prevention, 2009). Although children with ASD struggle with social interactions, quantitative meta-analyses have revealed that traditional social skill interventions only produce minimal effects (Bellini, Peters, Benner, & Hopf, 2007). Due to these minimal effects, this study diverged from the common understanding of social skill deficits and introduced an autonomic nervous system circuit as one root of social behavior problems. Children with ASD show a "fight-flight" (i.e., sympathetic) state at baseline and to unfamiliar individuals (e.g., Bal et al., 2010). Research indicates, however, that music has the ability to calm cardiovascular functioning (Iwanaga, Kobayashi, & Kawasaki, 2005) and improve social behaviors in children with ASD (Whipple, 2004). This study recruited participants (N = 23) between 4-7 years old with a previously diagnosed ASD. Each participant was assigned to a Music group, n = 11, or an Audiobook group, n = 12. The 90-minute experimental session consisted of a receptive vocabulary assessment and psychophysiological monitoring during a baseline video, social engagement task, listening period, and a recovery video. A soothed autonomic state was measured by increased high frequency heart rate variability and decreased heart rate. Results indicated a significant soothing effect for the Music group. Moreover, the Music group evidenced a significant increase in social attention (e.g., joint attention and sharing emotions) relative to the Audiobook group. Mediation analyses may reveal partial mediation for the soothed autonomic state on the relationship between group and social attention improvements. Thus, these results suggest that social skill interventions may not be targeting a core element of social deficits (i.e., over-aroused autonomic state).
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Napolitano, Amanda C. « Modality dominance in young children underlying mechanisms and broader implications / ». Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1146171556.

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Elshafei, Hesham. « Neurophysiological Mechanisms of Auditory Distractibility in the Healthy, Aging or Damaged Human Brain ». Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1255/document.

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Les mécanismes volontaires (V) et involontaires (I) de l’attention reposent sur les réseaux dorsal et ventral, convergeant dans le cortex préfrontal latéral (lPFC). La distractibilité accrue liée au vieillissement ou à une lésion frontale pourrait être due à une altération de l’équilibre entre ces mécanismes V et I, essentiel mais rarement étudié. Notre objectif est de tester, dans la modalité auditive, si (1) les oscillations alpha coordonnent l'activité du réseau dorsal, (2) les oscillations gamma celle du réseau ventral, (3) le couplage oscillatoire dans le lPFC maintient l’équilibre entre les deux réseaux. Ce travail vise également à étudier les corrélats oscillatoires de la distractibilité accrue liée au vieillissement ou à une atteinte frontale. Des données MEEG ont été enregistrées alors que des participants réalisaient le Competitive Attention Test, qui permet d’étudier simultanément les mécanismes V et I de l’attention. Nous avons montré que les oscillations alpha reflètent l’activation des mécanismes facilitateurs et suppresseurs de l’attention V, et la communication au sein du réseau dorsal ; alors que les oscillations gamma indexent l’activation du réseau ventral. De plus, le lPFC serait impliqué dans la communication au sein des deux réseaux, et le PFC médian dans l’équilibre attentionnel V/I. Nous avons également montré que la distractibilité accrue était liée à un déficit d’attention V au cours du vieillissement, et à une altération des processus V et I après lésion frontale. Ce travail de thèse offre donc une meilleure compréhension de la dynamique cérébrale oscillatoire sur laquelle repose l'équilibre attentionnel V/I, et donc la distractibilité
Top-down (TD) and bottom-up (BU) mechanisms of attention are supported by dorsal and ventral networks that mainly overlap in the lateral prefrontal cortex (lPFC). A balance between these mechanisms is essential, yet rarely investigated. Increased distractibility observed during ageing or after frontal damage could result from jeopardizing this balance. It has been proposed that distinct oscillatory frequencies support the activation of these two attention networks. Our main aim was to test, in the auditory modality, whether (1) alpha oscillations would coordinate activity within the dorsal TD network, (2) gamma activity would index the activation of the ventral BU network, (3) the lPFC would support the balance between these networks through oscillatory coupling. We also aimed to investigate the oscillatory correlates of the increased distractibility associated with ageing or frontal damage. MEEG data were recorded while participants performed the Competitive Attention Test, which enables simultaneous investigation of BU and TD attention mechanisms. We showed that alpha oscillations indexed facilitatory and suppressive mechanisms of TD attention, and communication within the dorsal network; while gamma oscillations indexed the ventral network activation. Moreover, the lPFC subtended communication in the two networks; with the TD/BU interaction occurring in the medial PFC. We also showed that ageing-related distractibility was of TD deficit origin. Finally, preliminary results suggest that lPFC damage can impact both TD and BU attention. This thesis provides novel insights into the brain oscillatory dynamics of the TD/BU attentional balance supporting distractibility

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Raykos, Bronwyn C. « Attentional and interpretive biases : independent dimensions of individual difference or expressions of a common selective processing mechanism ? » University of Western Australia. School of Psychology, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0018.

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[Truncated abstract] Attentional and interpretive biases are important dimensions of individual difference that have been implicated in the etiology and maintenance of a range of clinical problems. Yet there has been no systematic investigation into the relationship between these dimensions of individual difference. The current research program tested predictions derived from two competing theoretical accounts of the relationship between attentional and interpretive biases. The Common Mechanism Account proposes that cognitive biases represent concurrent manifestations of a single underlying selective processing mechanism. The Independent Mechanism account proposes that independent mechanisms underlie each bias. . . An apparent contradiction is that the manipulation of one bias served to also modify the other bias, despite the observation that the magnitude of the resulting change in both biases was uncorrelated. Neither the Common Mechanism nor the Independent Pathways accounts can adequately explain this pattern of results. A new account is proposed, in which attentional and interpretive biases are viewed as representing mechanisms that are related but that are not the same. Theoretical and applied implications of these findings are discussed, including the possibility that the two biases each may best predict emotional reactions to quite different stressful events and that training programs designed to attenuate allocation of attentional resources to threat may serve to reduce both attentional and interpretive selectivity in emotionally vulnerable individuals.

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Rohenkohl, Gustavo. « Temporal orienting in the human brain : neural mechanisms of control and modulation ». Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:95d78d46-6398-48ce-8ff9-30b4fd192e3f.

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The main aim of the experiments reported in this thesis was to explore the neural mechanisms underlying the temporal orienting of attention. In Chapter 3, I explored the possible dissociation between exogenous and endogenous temporal orienting by comparing reaction times to targets appearing after rhythmic or symbolic cues. Behavioural results provided evidence for the existence of dissociable exogenous and endogenous types of temporal orienting of attention. The experiment in Chapter 4 combined spatiotemporal expectations using rhythmic moving cues to test the modulatory effect of exogenous temporal orienting in the brain. Specifically, I used EEG to test the effect of temporal orienting on perceptual and motor stages of target analysis, as well as on anticipatory oscillatory brain activity. The time-frequency analysis revealed that rhythmic cues can entrain slow brains oscillations, providing a putative mechanism for enhancing the perceptual processing of expected events. Spatiotemporal expectations also modulated the amplitude of visual responses and the timing and amount of preparatory motor activity. In Chapter 5, I used a novel task to explore the neural modulatory effects of spatial and temporal expectations acting in isolation or in coordination. For the first time, the analysis of early visual responses demonstrated that temporal expectations alone, independently of spatial orienting, can enhance early visual perceptual processes. The time-frequency analysis in this experiment showed a desynchronisation of alpha oscillations focused over central-parietal electrodes induced by rhythmic cues that were independent of spatial expectations. When rhythmic cues carried spatiotemporal information, the alpha desynchronisation also spread over contralateral occipital electrodes. In Chapter 6, fMRI was used to test the possible neural dissociation between motor and temporal orienting. The results confirmed the large overlap between these two processes, but also indicated independent behavioural and neural effects of temporal orienting. Temporal orienting activated the left IPS across motor conditions, further implicating the left IPS in temporal orienting. Based on the results of these experiments, directions for future studies are discussed.

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Wang, Jing. « Hyperspectral Image Classification Based on Deep Learning and Module Inspired by Human Attention Mechanism ». Thesis, Griffith University, 2020. http://hdl.handle.net/10072/397634.

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Hyperspectral imaging technology acquires image data in a number of continuous narrow bands of the electromagnetic wave. The obtained hyperspectral images contain details of spectral re ectance of targets in addition to spatial information. The ability to characterize abundant spectral details of hyperspectral image makes it particularly suitable for remote sensing image analysis. Hyperspectral remote sensing image classi cation is one of the most important applications in remote sensing, and is the main research problem of this thesis. Researchers have already proposed a large variety of methods for hyperspectral image classi cation in the last few decades, which can be categorized into traditional methods and deep learning based methods. Recently, with the development of high performance computing and collection of large datasets, deep learning methods have been state of the art in hyperspectral image classi cation. Most of the existing deep learning methods take in the hyperspectral image and learn discriminant features in plain convolutional or fully connected layers. This learning manner treats all raw pixels and extracted features equally. However, human brains do not perform recognition task with equal consideration of every involved element. For recognition or classi cation tasks, it is possible that some parts of inputs or features are more important, while others are useless. Our visual system has the capability of attending to the signi cant aspects and ignoring irrelevant components. This has greatly contributed to our cognition ability and e ciency. Inspired by the attention mechanism of human brain, we design corresponding attention modules in the context of arti cial neural network for hyperspectral image classi cation. In addition, human visual system is a universal feature extractor and classi er in the sense that we can perform classi cation across multiple image styles, modalities and distributions. On the contrary, current deep learning based hyperspectral classi - cation paradigms require an individual model for every data domain. This is expensive and ine cient. Following similar philosophy of attention mechanism, we design domain attention modules for multi-domain hyperspectral image classi cation. In this thesis, we propose three attention modules for deep learning based hyperspectral image classi cation. In the rst work, we introduce attention based feature weighting networks for improving the classi cation accuracy of current plain neural networks. In a deep network for hyperspectral application, a hierarchy of spectral or spatial features are extracted layer by layer. Each layer contains the same semantic level of features. To model the importance of features in the same level, attention modules are designed by branching from current feature maps. In the attention branch, three steps are executed: summarizing information from current layer, modeling relationship among the features with fully connected or convolution layers, and outputting weighting masks to be multiplied with the original features. We propose feature weighting attention modules for spectral CNN, spatial CNN and spectral-spatial CNN, respectively. In the second work, we design attention modules speci cally attending to the bands of hyperspectral image. Compared to hidden features extracted in hidden layers of neural networks which have less interpretability and physical meaning, spectral bands of hyperspectral images correspond directly to real wavelength in the physical world. Thus attending to bands has special importance in a couple of aspects. First, it in uences the design and cost of hyperspectral sensor. Second, it is directly related to the dimension of the obtained raw data. Our band attention module can perform both band weighting and band selection. For band weighting, it has the ability to assign sample-wise weights to hyperspectral images and can interfere with the feature learning process in the early stage. For band selection, we carefully design an additional parallel input to the attention module for obtaining xed selected band sets and an activation function for ltering insigni cant bands in the training process. In the third work, we propose attention mechanisms to address multi-domain hyperspectral image classi cation. Di erent hyperspectral datasets have di erent data modalities, statistical distributions, or spectral dimensionalities. This brings signi cant challenges for a single network to learn all the tasks. The domain shift problem can be alleviated by adjusting the network towards the property of speci c domains. To this end, domain attention modules are designed to attend to the domain of the input data for adapting the network accordingly. Two domain attention modules: hard domain attention and soft domain attention are proposed. For the hard domain attention network, the attention mechanism is implemented by a muxer switch. According to the labels of data domain, a set of small domain speci c adapters are selected and connected to a main backbone network. In this way, the majority of network parameters are shared by all domains with only a small number of domain speci c parameters. For the soft domain attention network, we build the attention mechanism based on squeeze and excitation (SE) block. Several parallel SE blocks are applied as the feature adapters. On top of them, a higher level domain attention SE block is placed to achieve domain assignment.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Info & Comm Tech
Science, Environment, Engineering and Technology
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Wilson, Steven. « Mechanisms of attention and awareness : parameters and assessment of pre-attentional awareness using change blindness task ». Thesis, University of Lincoln, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496078.

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Moadab, Ida. « The Role of Mindfulness and Self-Compassion in the Neural Mechanisms of Attention and Self-Monitoring ». Thesis, University of Oregon, 2013. http://hdl.handle.net/1794/13402.

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The present study sought to investigate the effects of meditation practice on the neural mechanisms of attention and self-monitoring by comparing a group of experienced meditators to matched controls. Self-report measures of mindfulness and self-compassion were assessed to examine whether meditation-related improvements in attention and self-monitoring were linked to increases in these qualities. Thus, differences between groups (meditator versus control) on all variables and relationships among variables (attention, self-monitoring, self-compassion, and mindfulness) were explored. Results indicate that individuals with meditation experience showed enhancement in neural networks related to selective attention and attentional allocation, as evidenced by larger P1/N1 and P3b amplitudes, relative to controls. Meditators also showed improved self-monitoring of their errors, as indexed by enhanced Pe amplitudes, when compared to controls. Importantly, greater number of years of meditation experience was linked to larger Pe amplitudes, providing evidence that more practice with meditation was associated with greater error awareness. At the same time, meditators showed greater levels of mindfulness and self-compassion when compared to controls. Importantly, each of the neural indices was linked to greater levels of mindfulness and self-compassion. Specifically, self-kindness was correlated with each of these ERP components and to percentage of alpha power during meditation, and the mindfulness facet of observing fully mediated the relationship between meditation experience and P1 amplitudes. These findings suggest that the qualities that are enhanced with meditation are associated with enhancements in attentional control and awareness of errors. This study is an exciting step toward future intervention studies that combine multiple sources of information (self-report, neural measures, and behavior) to clarify the nature of the associations among these variables so that the mechanisms of mindfulness can be more fully understood.

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Buonocore, Antimo. « Remote distractor effects in saccadic, manual and covert attention tasks ». Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/5850.

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The Remote Distractor Effect (RDE) is a robust phenomenon where a saccade to a lateralised target is delayed by the appearance of a distractor in the contralateral hemifield (Walker, Kentridge, & Findlay, 1995). The main aim of this thesis was to test whether the RDE generalises to response modalities other then the eyes. In Chapter 2, the RDE was tested on saccadic and simple manual keypress responses, and on a choice discrimination task requiring a covert shift of attention. The RDE was observed for saccades, but not simple manual responses, suggesting that spatially oriented responses may be necessary for the phenomenon. However, it was unclear whether distractor interference occurred in the covert task. Chapter 4 compared the effects of distractors between spatially equivalent tasks requiring saccadic and manual aiming responses respectively. Again, the RDE was observed for the eyes but not for the hands. This dissociation was also replicated in a more naturalistic task in which participants were free to move their eyes during manual aiming. In order to examine the time-course of distractor effects for the eyes and the hands, a third experiment investigated distractor effects across a wider range of target-distractor delays, finding no RDE for manual aiming responses at distractor delays of 0, 100, or 150 ms. The failure of the RDE to generalise to manual aiming suggests that target selection mechanisms are not shared between hand and eye movements. Chapter 5 further investigated the role of distractors during covert discrimination. The first experiment showed that distractor appearance did not interfere with discrimination performance. A second experiment, in which participants were also asked to saccade toward the target, confirmed the lack of RDE for covert discrimination while saccades were slower in distractor trials. The dissociation between covert and overt orienting suggests important differences between shifts of covert attention and preparation of eye movements. Finally, Chapter 6 investigated the mechanism driving the RDE. In particular it was assessed whether saccadic inhibition (Reingold & Stampe, 2002) is responsible for the increase in saccadic latency induced by remote distractors. Examination of the distributions of saccadic latencies at different distractor delays showed that each distractor produced a discrete dip in saccadic frequency, time-locked to distractor onset, conforming closely to the character of saccadic inhibition. It is concluded that saccadic inhibition underlies the remote distractor effect.

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Magimairaj, Beula M. « Attentional Mechanisms in Children’s Complex Memory Span Performance ». Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1267650640.

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Doherty, Jason Michael. « What limits dual-tasking in working memory ? : an investigation of the effect of sub-task demand on maintenance mechanisms employed during dual-tasking ». Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/25884.

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A number of models of working memory have been proposed since the seminal work of Baddeley and Hitch (1974) on the Multiple Component Model (MCM). Subsequent MCM research focussed on developing a theoretical framework based on modality-specific stores that can operate in parallel during dual-tasking. The MCM can be contrasted with theories of working memory that assume an attention-based domain-general shared resource responsible for both short term retention as well as on-line cognition, such as the Time-Based Resource Sharing (TBRS) model (Barrouillet, Bernardin, & Camos, 2004; Barrouillet, Bernardin, Portrat, Vergauwe, & Camos, 2007). The TBRS model assumes that short-term memory is dependent on access to attention, and any diversion of attention results in increased forgetting. The model describes ‘refreshing’ as the process of serially bringing memory items briefly into the focus of attention. Barrouillet and colleagues have demonstrated in numerous studies that memory spans lower as the cognitive demand of the secondary task increases - findings that are incompatible with the MCM. However, Camos, Mora, and Oberauer (2011) found that both sub-vocal rehearsal (the verbal maintenance mechanism described in the MCM) and attention-based refreshing can be selectively employed by participants depending on task demands. Since TBRS methodology compares spans measured under different cognitive load levels that are the same for every participant, we were interested in whether ensuring that secondary task demand was set within each participant’s abilities would avoid ‘over-taxing’ the working memory system and reduce dual-task costs. Our initial investigations re-measured memory and processing spans under dual-task conditions with secondary tasks’ demand titrated according to each individual’s measured ability (Experiments 1 and 2, and Doherty & Logie, 2016). We found that memory span was unaffected when processing demand was titrated, but that processing performance was lower when memory load was set above participants’ span. Subsequent experiments (3-8) investigated the effect of setting memory and processing load ‘below span’, ‘at span’, and ‘above span’ on memory and processing accuracy during dual-tasking. Overall it was found that processing resources can be reallocated to support memory performance but memory resources cannot be reallocated to support processing performance. We interpret the results as evidence for specialised memory resources and rehearsal mechanisms that can be supplemented by attention-based processes once storage capacities are exceeded. Experiments 6-8 aimed to encourage the use of phonological- or attention-based rehearsal mechanisms for verbal short term memory by either introducing articulatory suppression (AS) or shortening available encoding time for memory items. It was found that participants exhibited shared-resource effects when they completed the dual-task under AS, suggesting a shift to attention-based rehearsal. When encoding time was limited participants’ memory performance during dual-tasking was unaffected by concurrent processing load, suggesting the use of a rehearsal method which did not require access to attention. Experiment 9 investigated whether participants could dynamically allocate attention to one task or the other, and found that while ‘priority’ tasks received no benefit, non-priority tasks exhibited a marked decrement in performance. We conclude that the perceived incompatibility between the MCM and attention-based theories of working memory such as the TBRS model may be more apparent than real, and suggest that future research should incorporate procedures and methodological considerations that take into account findings from both literatures.

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García, García Manuel Antonio. « The role of COMT, DAT and DRD2 polymorphisms on brain mechanisms of involuntary attention and cognitive control ». Doctoral thesis, Universitat de Barcelona, 2009. http://hdl.handle.net/10803/2722.

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Our genetic background plays a role in the way we face environmental changes and adapt our behavior adequately to the requirements of everyday life. The present research focuses on the role of three genes related to dopamine (DA) transmission on relevant cognitive processes, such as shifting attention when required by the environmental demands or processing of unexpected but potentially relevant events. Prefrontal cortex (PFC) and striatum dopamine activity seem to play different roles in attentional processing and interact to regulate stability and flexible update of context information. Therefore, we studied the action of genes regulating PFC dopamine action (i.e., Catechol-O-Methyltransferase; COMT), reuptake of dopamine diffused on extrasynaptic striatal space (i.e., Dopamine Transporter; DAT) and the concentration of D2-type dopamine receptors (i.e., dopamine D2 receptors; DRD2).

The results of these studies provide evidence for a relevant role of COMT, DAT1 and DRD2 genes in cognitive processes, which helps to understand cognitive disruption associated to dopamine dysregulation in psychiatric disorders.
Els nostres gens juguen un rol important en la manera que enfrontem els canvis de l'ambient i adaptem la nostre conducta adequadament. El present treball de recerca se centra en el paper de tres gens relacionats amb la dopamina (DA) sobre processos cognitius, com el canvi de l'atenció quan és requerit per les demandes ambientals o el processament d'esdeveniments inesperats però potencialment rellevants. L'activitat dopaminèrgica al còrtex prefrontal (PFC) i a l'estriat semblen jugar papers diferents en el processament atencional i interaccionen per a regular l'estabilitat i flexibilitat de l'actualització de la informació contextual. Per això, vam estudiar l'acció de gens que regulaven l'acció de la dopamina del PFC (i.e. Catechol-O-Methyltransferase; COMT), la resposta de dopamina difosa en l'espai extrasinàptic estriatal (i.e. Transportador de Dopamina; DAT) i la concentració de receptors de dopamina de tipus D2 (i.e. receptors D2 de dopamina; DRD2).

Els participants amb diversos al·lels dels gens estudiats van realitzar dues versions diferents d'un paradigma de distracció auditiu visual, en el qual se'ls demanava que ignoressin tons estàndards freqüents i sons ambientals nous rars que precedien els objectius pertinents de la tasca. En dos estudis, vam manipular l'efecte d'un context emocional sobre el processament d'esdeveniments nous inesperats, donada la potencial rellevància d'un esdeveniment nou durant una situació d'amenaça en la qual pot ser nociu. En tres estudis, els participants amb al·lels diferents o combinacions d'al·lels van realitzar un paradigma de commutació de tasca, en el qual l'actualització d'informació sensorial i de tasca es podria dissociar. Al llarg dels sis estudis, se van emprar mesures conductuals i electrofisiològiques enregistrades al cuir cabellut, com els anàlisis de l'electroencefalograma (EEG) al domini del temps promitjant els potencials cerebrals relacionats a esdeveniments (ERP), i l'activitat oscil·latòria cerebral al domini temps- freqüència.

Tres estudis van mostrar el paper del gen del DAT en el control cognitiu de l'atenció, suggerint així la pertinència de la DA estriatal en la flexibilitat cognitiva. Els nostres resultats suggereixen un processament independent del context dels canvis sensorials per la reconfiguració del set de la tasca en individus amb l'al·lel de 9 repeticions de DAT (9R+) relacionats amb una major disponibilitat de dopamina estriatal. Tanmateix, aquests individus van mostrar una detecció primerenca de la rellevància per la tasca dels canvis sensorials. El gen del DAT regulava la modulació del processament de la novetat per un context emocional. Els individus 9R+ van mostrar una resposta cerebral més gran als estimuls novedosos.

Dos estudis van mostrar el paper de la interacció dels gens de la COMT i del DRD2 sobre processos atencionals. S'ha suggerit que els individus amb l'al·lel de COMT Val i l'al·lel de DRD2 A1 (A1+) i COMT Met sense l'al·lel de DRD2 A1 (A1-) mostren una interacció equilibrada de dopamina prefrontal i estriatal. Aquests grups van mostrar distracció conductual, mentre que els individus ValA1- i els individus MetA1+ no van ser distrets per sons nous en un paradigma de distracció visual auditiu. Els grups, tanmateix, no-distrets resultaven processar esdeveniments nous a través de la restauracio d'activitat neuronal a 40 Hz. A més, aquells amb una interacció equilibrada semblaven tornar a configurar la informació de la tasca quan era necessari, mentre que aquells amb dopamina PFC o estriatal extremes tornarien a configurar el set de la tasca després de cada canvi sensorial.

Els resultats dels estudis de la tesi proporcionen una evidència del paper rellevant dels gens de la COMT, el DAT1 i el DRD2 en processos cognitius, i ajuden a entendre els dèficits cognitius associats a la disregulació de la dopamina en trastorns psiquiàtrics.

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Pomè, Antonella. « Attentional mechanisms and number representation ». Doctoral thesis, 2020. http://hdl.handle.net/2158/1206037.

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The work presented in this thesis has explored attentional mechanisms and numerosity representations in visual estimation through a variety of methods. After a brief literature review, in chapter 2 I present a study of visual attention that demonstrates a clear example of how perception is influenced by past experience (Priming of Pop-out). Besides the classical measures of Reaction Times, I investigated whether attentional mechanisms can be measured with pupillometry measures. The results suggest that pupillometry may be a valid, non-invasive and fast tool to evaluate some cognitive and perceptual processes, particularly in clinical populations (such as ASD) when behavioral measures may fail. The focus of the thesis then shifts to investigate another capacity of the visual system: estimating number of objects in a visual scene. In Chapter 3 I investigated whether reaction times, which have classically been used to assess differences between very low and intermediate number, can be used to prove the existence of a third regime of number perception, that comes in to play when the items on the scene are too packed to be perceived independently. The results show that not only do thresholds change from intermediate to high densities, but reaction times also follow this pattern. In Chapter 4 I present a study showing how linking elements influence number perception at various ranges of numerosity. Contribution of both number and texture-density are examined. This study strengthens the idea that the Approximate Number System operates only when items are sparse enough to permit spatial segregation. After that limit, ANS gives way to another separate perceptual system responding to texture-density: for sparse stimuli, numerosity – but not element density – can be directly perceived, without being calculated indirectly from other perceptual features. In the fifth and sixth Chapter, I move back to attentional mechanisms, with particular interest in number estimation processes. In the fifth chapter, the role of visual and auditory attentional resources on discrimination thresholds over all the three ranges (subitizing, estimation and texture-density) was investigated. Attentional load greatly affected the subitizing range, to the extent that thresholds became similar to those of the estimation range. More important, numerosities higher than 60-80 dots were more affected by attentional load (both visual and auditory) than lower (non-subitizing) numerosities. Following this, the last empirical chapter assessed the contribution of increasing attentional engagement, instead of decreasing it, on enumeration of numerosity. Here, we examined whether presentation of a visual cue that increased attentional engagement in a given task can facilitate the estimation process, leading to less compressive representation of number in space compared to when attention is diverted elsewhere. Results revealed that enumeration of a collection of dots in the location previously cued led to more precise and accurate (and linear) judgements than enumeration in uncued locations. Overall, this thesis assessed the distinction between intermediate and large numerosity using reaction times, precision, linking elements, and attentional techniques. All studies point to the existence of separate regimes of number perception. Moreover, data on location and object-based attention may suggest that researches focusing on a mechanism that can improve rather than impair enumeration processes could prove helpful when considering rehabilitation in conditions such as dyscalculia. Finally, data on priming effects support an increasing body of evidence that pupillometry can be very useful in tracking perceptual processes, providing information that cannot be gathered from standard psychophysics. Likewise, it would seem that these pupillometry measures may be more sensitive to variations in perceptual styles, and their dependency on personality traits.

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