Letteratura scientifica selezionata sul tema "Perceptual cues and mechanisms"
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Articoli di riviste sul tema "Perceptual cues and mechanisms"
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Xiao, Mei, May Wong, Michelle Umali e Marc Pomplun. "Using Eye-Tracking to Study Audio — Visual Perceptual Integration". Perception 36, n. 9 (settembre 2007): 1391–95. http://dx.doi.org/10.1068/p5731.
Testo completoAbstract (sommario):
Perceptual integration of audio—visual stimuli is fundamental to our everyday conscious experience. Eye-movement analysis may be a suitable tool for studying such integration, since eye movements respond to auditory as well as visual input. Previous studies have shown that additional auditory cues in visual-search tasks can guide eye movements more efficiently and reduce their latency. However, these auditory cues were task-relevant since they indicated the target position and onset time. Therefore, the observed effects may have been due to subjects using the cues as additional information to maximize their performance, without perceptually integrating them with the visual displays. Here, we combine a visual-tracking task with a continuous, task-irrelevant sound from a stationary source to demonstrate that audio—visual perceptual integration affects low-level oculomotor mechanisms. Auditory stimuli of constant, increasing, or decreasing pitch were presented. All sound categories induced more smooth-pursuit eye movement than silence, with the greatest effect occurring with stimuli of increasing pitch. A possible explanation is that integration of the visual scene with continuous sound creates the perception of continuous visual motion. Increasing pitch may amplify this effect through its common association with accelerating motion.
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Chepeliuk, Anastasia A., e Marina G. Vinogradova. "The Performance of Visual Perceptual Tasks in Patients with Schizotypal Personality Disorder". Psychology in Russia: State of the Art 14, n. 2 (2021): 42–58. http://dx.doi.org/10.11621/pir.2021.0204.
Testo completoAbstract (sommario):
Background. The most significant features for clinical diagnosis of schizotypal personality disorder (SPD) are cognitive-perceptual and disorganized symptoms. Experimental study of visual perceptual processes is important to elucidate the psychological mechanisms of cognitive-perceptual impairment in SPD. Objective. To research the performance of visual perceptual tasks in SPD. Design. Series I and II presented the subjects with visual perceptual tasks with different types of instructions (vague, verbal, or visual perceptual cues). The Wechsler Adult Intelligence Scale (WAIS-R) was also administered. The participants were 39 SPD patients, 36 obsessive-compulsive personality disorder (OCPD) patients (F.21.8, F.60.5 in ICD-10, respectively), and 102 healthy controls. Results. SPD patients had a significantly lower number of correct answers in conditions of vague instruction and verbal cues in Series I of a visual-perceptual task in comparison with healthy subjects (р ≤ 0.01). With visual perceptual cues in Series II, patients with SPD had the same number of correct answers as controls, whereas OCPD patients had the same number of correct answers as controls with verbal cues in Series I. SPD patients had significantly lower scores in most verbal and nonverbal WAIS-R subtests in comparison with controls. SPD patients differed from OCPD patients in that they had lower scores in the “Information” (p ≤ 0.05) and “Comprehension” (p ≤ 0.05) subtests. Conclusion. With visual-perceptual cues, SPD patients were able to achieve normative results in the performance of visual-perceptual tasks, whereas patients with OCPD demonstrated lower productivity. In SPD patients, the basic impairments were associated with difficulties in inhibition of peculiar responses, stability of a subjective manner of performance and inability to revise it, low orientation to the model, and slipping into subjective associations with the stimuli.
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Goda, N., S. Takahashi e Y. Ejima. "Luminance and Colour Cues in Perceptual Transparency". Perception 26, n. 1_suppl (agosto 1997): 159. http://dx.doi.org/10.1068/v970360.
Testo completoAbstract (sommario):
A series of experiments was carried out to determine the dependence of the perception of transparency on colour relationships in a four-region pattern comprising two non-overlapping regions, an overlapping region, and a background. The proportion of trials where the pattern was perceived as transparent, and the relative layering in depth of the two perceived surfaces, were determined as a function of the luminance of colour of the overlapping region while those of the non-overlapping regions were kept constant. It was found that perceptual transparency could arise from displays where the four regions were isoluminant but different in colour. The function obtained for isoluminant colour-varying patterns was quite similar to that obtained for isochromatic luminance-varying patterns. In both types of patterns, the background condition strongly affected perceptual transparency and perceived depth order in a similar way. These results suggest that perceptual transparency for both the isochromatic and the isoluminant pattern was specified in a common manner by contrast relations in a certain region of the image, and was not always constrained by the physics of transparency. The dependence of perceptual transparency on the contrast relation may be accounted for by mechanisms incorporating the filling-in process associated with antagonistic luminance and opponent-colour responses.
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Yildiz, Gizem Y., Bailey G. Evans e Philippe A. Chouinard. "The Effects of Adding Pictorial Depth Cues to the Poggendorff Illusion". Vision 6, n. 3 (18 luglio 2022): 44. http://dx.doi.org/10.3390/vision6030044.
Testo completoAbstract (sommario):
We tested if the misapplication of perceptual constancy mechanisms might explain the perceived misalignment of the oblique lines in the Poggendorff illusion. Specifically, whether these mechanisms might treat the rectangle in the middle portion of the Poggendorff stimulus as an occluder in front of one long line appearing on either side, causing an apparent decrease in the rectangle’s width and an apparent increase in the misalignment of the oblique lines. The study aimed to examine these possibilities by examining the effects of adding pictorial depth cues. In experiments 1 and 2, we presented a central rectangle composed of either large or small bricks to determine if this manipulation would change the perceived alignment of the oblique lines and the perceived width of the central rectangle, respectively. The experiments demonstrated no changes that would support a misapplication of perceptual constancy in driving the illusion, despite some evidence of perceptual size rescaling of the central rectangle. In experiment 3, we presented Poggendorff stimuli in front and at the back of a corridor background rich in texture and linear perspective depth cues to determine if adding these cues would affect the Poggendorff illusion. The central rectangle was physically large and small when presented in front and at the back of the corridor, respectively. The strength of the Poggendorff illusion varied as a function of the physical size of the central rectangle, and, contrary to our predictions, the addition of pictorial depth cues in both the central rectangle and the background decreased rather than increased the strength of the illusion. The implications of these results with regards to different theories are discussed. It could be the case that the illusion depends on both low-level and cognitive mechanisms and that deleterious effects occur on the former when the latter ascribes more certainty to the oblique lines being the same line receding into the distance.
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Donato, Rita, Adriano Contillo, Gianluca Campana, Marco Roccato, Óscar F. Gonçalves e Andrea Pavan. "Visual Perceptual Learning of Form–Motion Integration: Exploring the Involved Mechanisms with Transfer Effects and the Equivalent Noise Approach". Brain Sciences 14, n. 10 (30 settembre 2024): 997. http://dx.doi.org/10.3390/brainsci14100997.
Testo completoAbstract (sommario):
Background: Visual perceptual learning plays a crucial role in shaping our understanding of how the human brain integrates visual cues to construct coherent perceptual experiences. The visual system is continually challenged to integrate a multitude of visual cues, including form and motion, to create a unified representation of the surrounding visual scene. This process involves both the processing of local signals and their integration into a coherent global percept. Over the past several decades, researchers have explored the mechanisms underlying this integration, focusing on concepts such as internal noise and sampling efficiency, which pertain to local and global processing, respectively. Objectives and Methods: In this study, we investigated the influence of visual perceptual learning on non-directional motion processing using dynamic Glass patterns (GPs) and modified Random-Dot Kinematograms (mRDKs). We also explored the mechanisms of learning transfer to different stimuli and tasks. Specifically, we aimed to assess whether visual perceptual learning based on illusory directional motion, triggered by form and motion cues (dynamic GPs), transfers to stimuli that elicit comparable illusory motion, such as mRDKs. Additionally, we examined whether training on form and motion coherence thresholds improves internal noise filtering and sampling efficiency. Results: Our results revealed significant learning effects on the trained task, enhancing the perception of dynamic GPs. Furthermore, there was a substantial learning transfer to the non-trained stimulus (mRDKs) and partial transfer to a different task. The data also showed differences in coherence thresholds between dynamic GPs and mRDKs, with GPs showing lower coherence thresholds than mRDKs. Finally, an interaction between visual stimulus type and session for sampling efficiency revealed that the effect of training session on participants’ performance varied depending on the type of visual stimulus, with dynamic GPs being influenced differently than mRDKs. Conclusion: These findings highlight the complexity of perceptual learning and suggest that the transfer of learning effects may be influenced by the specific characteristics of both the training stimuli and tasks, providing valuable insights for future research in visual processing.
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Sperandio, Irene, Irene Sperandio e Philippe A. Chouinard. "The Mechanisms of Size Constancy". Multisensory Research 28, n. 3-4 (2015): 253–83. http://dx.doi.org/10.1163/22134808-00002483.
Testo completoAbstract (sommario):
Size constancy is the result of cognitive scaling operations that enable us to perceive an object as having the same size when presented at different viewing distances. In this article, we review the literature on size and distance perception to form an overarching synthesis of how the brain might combine retinal images and distance cues of retinal and extra-retinal origin to produce a perceptual visual experience of a world where objects have a constant size. A convergence of evidence from visual psychophysics, neurophysiology, neuropsychology, electrophysiology and neuroimaging highlight the primary visual cortex (V1) as an important node in mediating size–distance scaling. It is now evident that this brain area is involved in the integration of multiple signals for the purposes of size perception and does much more than fulfil the role of an entry position in a series of hierarchical cortical events. We also discuss how information from other sensory modalities can also contribute to size–distance scaling and shape our perceptual visual experience.
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Shapcott, Katharine A., Joscha T. Schmiedt, Kleopatra Kouroupaki, Ricardo Kienitz, Andreea Lazar, Wolf Singer e Michael C. Schmid. "Reward-Related Suppression of Neural Activity in Macaque Visual Area V4". Cerebral Cortex 30, n. 9 (30 aprile 2020): 4871–81. http://dx.doi.org/10.1093/cercor/bhaa079.
Testo completoAbstract (sommario):
Abstract In order for organisms to survive, they need to detect rewarding stimuli, for example, food or a mate, in a complex environment with many competing stimuli. These rewarding stimuli should be detected even if they are nonsalient or irrelevant to the current goal. The value-driven theory of attentional selection proposes that this detection takes place through reward-associated stimuli automatically engaging attentional mechanisms. But how this is achieved in the brain is not very well understood. Here, we investigate the effect of differential reward on the multiunit activity in visual area V4 of monkeys performing a perceptual judgment task. Surprisingly, instead of finding reward-related increases in neural responses to the perceptual target, we observed a large suppression at the onset of the reward indicating cues. Therefore, while previous research showed that reward increases neural activity, here we report a decrease. More suppression was caused by cues associated with higher reward than with lower reward, although neither cue was informative about the perceptually correct choice. This finding of reward-associated neural suppression further highlights normalization as a general cortical mechanism and is consistent with predictions of the value-driven attention theory.
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Schaller, Mark. "The behavioural immune system and the psychology of human sociality". Philosophical Transactions of the Royal Society B: Biological Sciences 366, n. 1583 (12 dicembre 2011): 3418–26. http://dx.doi.org/10.1098/rstb.2011.0029.
Testo completoAbstract (sommario):
Because immunological defence against pathogens is costly and merely reactive, human anti-pathogen defence is also characterized by proactive behavioural mechanisms that inhibit contact with pathogens in the first place. This behavioural immune system comprises psychological processes that infer infection risk from perceptual cues, and that respond to these perceptual cues through the activation of aversive emotions, cognitions and behavioural impulses. These processes are engaged flexibly, producing context–contingent variation in the nature and magnitude of aversive responses. These processes have important implications for human social cognition and social behaviour—including implications for social gregariousness, person perception, intergroup prejudice, mate preferences, sexual behaviour and conformity. Empirical evidence bearing on these many implications is reviewed and discussed. This review also identifies important directions for future research on the human behavioural immune system—including the need for enquiry into underlying mechanisms, additional behavioural consequences and implications for human health and well-being.
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Palmer, Colin J., Nathan Caruana, Colin W. G. Clifford e Kiley J. Seymour. "Perceptual integration of head and eye cues to gaze direction in schizophrenia". Royal Society Open Science 5, n. 12 (dicembre 2018): 180885. http://dx.doi.org/10.1098/rsos.180885.
Testo completoAbstract (sommario):
The perceptual mechanisms that underlie social experience in schizophrenia are increasingly becoming a target of empirical research. In the context of low-level vision, there is evidence for a reduction in the integration of sensory features in schizophrenia (e.g. increased thresholds for contour detection and motion coherence). In the context of higher-level vision, comparable differences in the integration of sensory features of the face could in theory impair the recognition of important social cues. Here we examine how the sense of where other people are looking relies upon the integration of eye-region cues and head-region cues. Adults with schizophrenia viewed face images designed to elicit the ‘Wollaston illusion’, a perceptual phenomenon in which the perceived gaze direction associated with a given pair of eyes is modulated by the surrounding sensory context. We performed computational modelling of these psychophysical data to quantify individual differences in the use of facial cues to gaze direction. We find that adults with schizophrenia exhibit a robust perceptual effect whereby their sense of other people's direction of gaze is strongly biased by sensory cues relating to head orientation in addition to eye region information. These results indicate that the visual integration of facial cues to gaze direction in schizophrenia is intact, helping to constrain theories of reduced integrative processing in higher-level and lower-level vision. In addition, robust gaze processing was evident in the tested participants despite reduced performance on a theory of mind task designed to assess higher-level social cognition.
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Merfeld, Daniel M., Sukyung Park, Claire Gianna-Poulin, F. Owen Black e Scott Wood. "Vestibular Perception and Action Employ Qualitatively Different Mechanisms. II. VOR and Perceptual Responses During Combined Tilt&Translation". Journal of Neurophysiology 94, n. 1 (luglio 2005): 199–205. http://dx.doi.org/10.1152/jn.00905.2004.
Testo completoAbstract (sommario):
II. VOR and perceptual responses during combined Tilt&Translation. To compare and contrast the neural mechanisms that contribute to vestibular perception and action, we measured vestibuloocular reflexes (VOR) and perceptions of tilt and translation. We took advantage of the well-known ambiguity that the otolith organs respond to both linear acceleration and tilt with respect to gravity and investigated the mechanisms by which this ambiguity is resolved. A new motion paradigm that combined roll tilt with inter-aural translation (“ Tilt&Translation”) was used; subjects were sinusoidally (0.8 Hz) roll tilted but with their ears above or below the rotation axis. This paradigm provided sinusoidal roll canal cues that were the same across trials while providing otolith cues that varied linearly with ear position relative to the earth-horizontal rotation axis. We found that perceived tilt and translation depended on canal cues, with substantial roll tilt and inter-aural translation perceptions reported even when the otolith organs measured no inter-aural force. These findings match internal model predictions that rotational cues from the canals influence the neural processing of otolith cues. We also found horizontal translational VORs that varied linearly with radius; a minimal response was measured when the otolith organs transduced little or no inter-aural force. Hence, the horizontal translational VOR was dependent on otolith cues but independent of canal cues. These findings match predictions that translational VORs are elicited by simple filtering of otolith signals. We conclude that internal models govern human perception of tilt and translation at 0.8 Hz and that high-pass filtering governs the human translational VOR at this same frequency.
Tesi sul tema "Perceptual cues and mechanisms"
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Driller, Karina. "From Cue to Construct : Cues, Mechanisms, and Stability in Haptic Perception". Electronic Thesis or Diss., Sorbonne université, 2024. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2024SORUS418.pdf.
Testo completoAbstract (sommario):
La perception haptique sert d'interface principale avec le monde physique. Sans elle, notre capacité à comprendre et à répondre à un monde rempli d'objets et de sujets serait profondément altérée. Cette thèse traite de la manière dont nous reconstruisons perceptuellement ce qui est en contact avec notre peau à partir d'entrées mécaniques pertinentes sur le plan comportemental lors des interactions haptiques. Ces informations permettent au système sensoriel d'atteindre ses objectifs, dont l'exploration et la manipulation fine des objets. Après une introduction (Chapitre 1) couvrant les concepts liés à l'émergence des percepts haptiques stables, la thèse présente une série d'études expérimentales visant à découvrir les indices et mécanismes utilisés pour reconstruire différentes interactions haptiques. Comme les interactions haptiques commencent par la détection du contact, le Chapitre 2 identifie quelles informations le système sensoriel utilise pour détecter ce contact. Cette première partie révèle un métamère d'intensité pour le codage des événements d'impact et suggère que l'énergie transférée (le travail mécanique) est un indice important, mais pas le seul facteur dans la décomposition perceptuelle des interactions peau-objet. L'accent passe ensuite à des interactions plus complexes. Comme les indices de texture et de matériau sont cruciaux pour la préhension et le glissement, une attention particulière est accordée à la perception haptique de la rugosité et de la compliance, couvrant trois chapitres. Compte tenu de la complexité de cette perception, le Chapitre 3 explore comment capturer cette complexité sans compromettre le contrôle expérimental, via le développement d'une base de données de stimuli bien caractérisés. Dans le Chapitre 4, l'expérience explore ensuite la contribution des ondes de propagation vibratoires en éliminant les informations cutanées via une anesthésie du doigt. Nous identifions les ondes comme un indice pertinent pour la perception de la rugosité pour certains, mais pas tous. La douceur perçue est, elle, fortement réduite sans informations tactiles locales. Le Chapitre 5 explore l'influence combinée des caractéristiques de surface et de l'élasticité dans la perception de la rugosité et de la douceur, mettant en lumière une confusion perceptuelle dans la reconstruction de la rugosité. Le travail révèle des métamères de rugosité, des zones où différentes combinaisons d'indices mènent à des perceptions identiques. Le dernier chapitre (Chapitre 6) explore les conséquences du timing perçu lors des interactions haptiques lorsque les indices tactiles locaux sont supprimés. Une tâche de liaison temporelle est utilisée pour éclairer le rôle des indices cutanés dans l'estimation du temps d'interaction peau-bouton. Ensemble, ces travaux soulignent l'importance de bien déterminer les contributions des indices et mécanismes physiques, mécaniques, neuronaux et perceptuels pour comprendre la reconstruction du monde tactileHaptic perception serves as our primary interface to the physical world. Without it, our ability to understand and respond to a world full of objects and subjects would be profoundly impaired. This dissertation addresses the problem of how we perceptually reconstruct what is in contact with our skin from behaviorally-relevant mechanical inputs during haptic interactions. Behaviorally-relevant information is defined as the kind of information that allows the sensory system to achieve its goals, and a primary goal of the somatosensory system is to enable the exploration and dexterous manipulation of objects.Following an introduction (Chapter 1), which covers fundamental concepts related to the emergence of stable haptic percepts, the dissertation comprises a series of experimental studies aimed at uncovering the essential cues and mechanisms used to perceptually reconstruct different haptic interactions. Because most haptic interactions start with the detection of contact, the first challenge taken in Chapter 2 is to identify what information the sensory system uses to detect the onset of skin contact during basic impact events. This first part of the dissertation uncovers a basic intensity metamer in the encoding of impact events and suggests the total amount of energy transferred by a force (i.e., the mechanical work) as an important cue, but not the sole determinant in the perceptual decomposition of haptic skin-object interactions.The focus then moves towards more complex everyday-like skin-object interactions. Because texture and material cues are critical to grasp and sliding behavior, special emphasis is placed on haptic texture and material perception (i.e., roughness and compliance perception), spanning three full chapters of this dissertation. Given the high-dimensional nature of haptic material and texture perception, Chapter 3 first explores how we can capture the complexity of haptic interactions with naturalistic surfaces without compromising on the experimental control needed to link specific cues to perceptual phenomena. This problem is addressed via the development of a dual-property stimulus database containing well-characterized stimuli which resemble the statistics of naturally occurring rough and compliant surfaces.In a following experiment, Chapter 4 then explores the contribution of vibratory propagation waves in perceptually reconstructing these surfaces by eliminating cutaneous information using local anesthesia of the index finger. We identify propagation waves as a behaviorally-relevant and sufficient cue for roughness perception for some, but not all participants. The perceived softness of these surfaces, on the other hand, is strongly diminished when local tactile information is removed. Subsequently, Chapter 5 explores the combined influence of surface features and material elasticity in mediating roughness and softness perception and highlights a perceptual confound in the reconstruction of surface roughness. The work uncovers roughness metamers, that is, regions where different cue combinations lead to identical perceptual outcomes.The final empirical chapter of this dissertation (Chapter 6) uncovers the consequence of the perceived timing of dynamic haptic interactions when behaviorally-relevant local tactile cues are removed. A temporal-binding task is used to illuminate the role of cutaneous cues in estimating the time course of mechanical skin-button interaction.Together, the work presented in this dissertation highlights the importance of correctly determining the contributions of physical, mechanical, neural, and perceptual-level cues and mechanisms in understanding the reconstruction of our world of touch
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Jones, Peter R. "Mechanisms of auditory perceptual learning". Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13376/.
Testo completoAbstract (sommario):
Practice improves performance on many basic auditory tasks. However, while the phenomenon of auditory perceptual learning is well established, little is known about the mechanisms underlying such improvements. What is learned during auditory perceptual learning? This thesis attempts to answer this question by applying models of performance to behavioural response data, and examining which parameters change with practice. On a simple pure tone discrimination task, learning is shown to primarily represent a reduction in internal noise, with encoding efficiency, attentiveness and bias appearing invariant. In a more complex auditory detection task, learning and development are also shown to involve improvements in listening strategy, with listeners becoming better able to selectively-attend to task-relevant information. Finally, task performance is potentially constrained not just by the strength of the sensory evidence, but also by the efficiency of the wider decision process that the sensory evidence informs. Thus, in the final chapters learning is also shown to involve reductions in both stationary and nonstationary bias. In short, learning is shown to be subserved by multiple mechanisms that: operate in parallel, vary in importance depending on the task demands, and incorporate both sensory and non-sensory processes. The methods of analysis described herein are shown to effectively partition components of perception in normal hearing children and adults, and may help to understand learning processes needed for the rehabilitation of listening difficulties.
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Hancock, Sarah. "Perceptual mechanisms underlying binocular rivalry". Thesis, University of York, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437581.
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Seaborn, Matthew. "Colour content based image retrieval using spatial and perceptual cues". Thesis, Brunel University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342391.
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Al-Dossari, Munira. "Biases and mechanisms in perceptual memory". Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/12208.
Testo completoAbstract (sommario):
Intermittent presentation of an ambiguous visual stimulus leads to a memory effect in which the percept on one presentation is usually the same as on the previous presentation. This effect is a form of perceptual memory. The aim of this research was to compare and examine the different explanations of biases in this form of perceptual memory. The mechanism of the stabilisation of ambiguous perception during intermittent presentation of ambiguous stimuli was also investigated. The Participants were adult humans who voluntarily participated in the experiments. An ambiguous percept was created using binocular rivalry: most of the rivalry stimuli consisted of a grating to one eye and an orthogonal grating to the other eye. In order to measure biases in perceptual memory, ambiguous stimuli were presented intermittently with varying monocular contrasts. To investigate the mechanism of perceptual memory, brief monocular test stimuli were presented in the intervals between the rivalry stimuli, and the threshold response to the test stimuli was measured. Psychometric functions of monocular contrast predominance thresholds are used throughout this thesis. To start with, a new method of measuring the psychometric function is described. On each trial the stimulus contrast was sampled from a Gaussian probability density, and the reported percept on each trial was binned to calculate the psychometric function. This method has the advantage over conventional techniques, such as the method of constant stimuli, that this method reduces the potentially confounding factors such as adaptation. Furthermore, this method appears to be effective in concentrating the trials around the threshold region of the curve where usually there is less stimulus certainty allowing the achievement of a cleaner estimation of the slope. There were four following main results: First, a chronic bias towards the right-eye was established which was not stimulus specific rather eye specific. The probability of a right-eye percept was calculated as a function of right-eye contrast, with the sum of the two monocular contrasts equal to 1. This psychometric function was not centred over a contrast of 0.5. Instead the probability of seeing a right-eye percept was greater than 0.5 at this contrast, meaning that there was a chronic bias towards the right-eye stimulus. This bias persisted when the orientations were swapped between eyes, meaning that it was eye- rather than stimulus-specific. Second, there was a substantial variation in the strength of the bias among participants. This was demonstrated by analysing the same psychometric functions according to the perceptual history. The level of function was found more convincing when consecutive percepts were identical in comparison with that when the percepts were different. This percept-induced bias is the well-known perceptual stabilisation effect, the main focus of this thesis. The strength of the bias was measured as the lateral shift between the two psychometric functions. Surprisingly, the bias differed substantially between Participants; for the standard participant cohort the range was 0 – 0.28 contrast units with a mean of 0.11. Third, a comparison between psychometric functions resulted in response to intermittent rivalry and continuous rivalry demonstrated that there was a greater influence of noisy neural processes during intermittent rivalry and the intermittent rivalry produced a stronger chronic bias towards the right eye when compared with that of the continuous rivalry. This conclusion was reached by measuring psychometric functions during intermittent rivalry and continuous rivalry and by making a comparative analysis of the results. The contrast of both monocular stimuli varied such that they always summed to 1, and the rivalry stimuli were viewed continuously. The slope of the psychometric functions was about half of that obtained during intermittent rivalry, indicating a greater influence of noisy neural processes. The chronic bias was towards the right eye, as before, but weaker than for intermittent rivalry. Fourth, it was demonstrated that the threshold for discriminating the test stimulus was lower for the match case than for mismatch, but the reduction was only statistically significant when the participant’s percept-induced bias was taken into account. To demonstrate this mechanism of perceptual stabilisation was investigated by using intermittently presented rivalry stimuli, and inserting a brief monocular test stimulus into the intervals between rivalry stimuli. The spatial form of the test stimulus matched that of the right-eye rivalry stimulus, and the form of the test stimulus therefore matched or mismatched the rivalry percept. In conclusion, this research has established a new and more effective method of measuring psychometric functions which provides a better picture of the responses as well as a robust measure of the threshold. It has been further demonstrated that in response to intermittently presented ambiguous stimuli a chronic bias towards the right eye and a temporary bias in the direction of the previous percept are established in perceptual memory. Similarly, a bias towards the right eye is also demonstrated when the stimulus is presented continuously. Furthermore, the research has helped to improve our understanding of the mechanisms of perceptual memory by demonstrating the establishment of a relatively weak, but statistically significant threshold due to the effects of percept.
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Housley, Meghan K. "The Positivity-Cues-Familiarity Effect and Initial Stimulus Valence". Miami University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=miami1185554049.
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Hamaoui, Kamil. "The perceptual grouping of musical sequences : pitch and timing as competing cues /". Diss., Connect to a 24 p. preview or request complete full text in PDF formate. Access restricted to UC IP addresses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3236630.
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Simon, Laurent. "Development of multichannel recording and reproduction techniques based on auditory perceptual cues". Thesis, University of Surrey, 2011. http://epubs.surrey.ac.uk/844355/.
Testo completoAbstract (sommario):
In order to capture and reproduce sound all around the listener in a perceptually realistic way, a recording technique (microphone layout) and a reproduction system (loudspeaker layout) capable of accurate 360° imaging are required. In order to develop the reproduction system, binaural and loudspeaker-based localisation cues were investigated in a literature review. The necessary loudspeaker-based localisation cues to manipulate the location of a sound image were analysed, and these showed that the common 5.1 surround sound loudspeaker arrangement could produce stable images to the front of the listener but not to the side. An 8-channel loudspeaker configuration arranged as a regular octagon was therefore chosen based on attempting to recreate plausible interaural cues for all locations. The performance of this was compared to a 5.1 loudspeaker system in terms of localisation accuracy. It was shown that the octagonal loudspeaker configuration produces more stable and more accurate images all around the listener. The octagonal loudspeaker arrangement required new microphone techniques for optimum recording and reproduction. An overview of the current literature showed how localisation curves can be used to design microphone arrays, and the other physical and perceptual parameters that need to be considered in microphone array design. This showed that it is useful to derive localisation curves for the new loudspeaker configuration, as these can be used to optimise the microphone array's sound imaging accuracy. An experiment was therefore conducted to measure the localisation curves, and it showed that localisation curves are different for the loudspeaker pairs to the front, side or the rear of the listener. It also showed that to the side of the listener, interchannel time differences have little influence on the perceived location of the sound event. The derivation of these localisation curves enabled the development of a microphone array design tool that predicts the localisation profile of a microphone array as a function of its geometrical set-up and the directivities of the microphones. The predictions of this tool were evaluated by comparing sound image positions for recordings of ten sound sources with ten different microphone arrays. This showed that the error of prediction is small when the crosstalk due to the microphone array is low. A linear regression model was created and shown to reasonably model the error of prediction as a function of the crosstalk level and crosstalk delay.
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Kwok, Rebecca Martha. "Visual mechanisms subserving perceptual judgement and action". Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408703.
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Wang, Xueying. "Mechanisms of Simple Perceptual Decision Making Processes". The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1249662470.
Testo completoLibri sul tema "Perceptual cues and mechanisms"
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Stine, Gabriel. Neural mechanisms for forming and terminating a perceptual decision. [New York, N.Y.?]: [publisher not identified], 2022.
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Zanon, Sandra Lia. Effects of combined perceptual and conceptual retrieval cues on primed word-fragment completion. Ottawa: National Library of Canada, 1993.
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Jan, Gauffin, e Hammarberg Britta, a cura di. Vocal fold physiology: Acoustic, perceptual, and physiological aspects of voice mechanisms. San Diego, Calif: Singular Pub. Group, 1991.
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Hinkle, William. Neural Mechanisms Mediating the Effects of Food Cues and Acute Exercise: A functional Magnetic Resonance Imaging and Functional Connectivity Investigation. [New York, N.Y.?]: [publisher not identified], 2013.
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Sundar, S. Shyam. Social psychology of interactivity in human-website interaction. A cura di Adam N. Joinson, Katelyn Y. A. McKenna, Tom Postmes e Ulf-Dietrich Reips. Oxford University Press, 2012. http://dx.doi.org/10.1093/oxfordhb/9780199561803.013.0007.
Testo completoAbstract (sommario):
This article discusses interactivity as a modality feature, source feature, and message feature. It argues that the ultimate effect of interactivity does not lie so much in its function as a peripheral cue in the message context, but as a technological feature that boosts social-psychological effects of content by creating greater user engagement with it. Interactivity can manifest itself by extending the range and functionality of all three basic elements of mediated communication – source, modality, message – and, through theoretical mechanisms involving concepts such as perceptual bandwidth, customization, and contingency, it can determine the manner in which content is psychologically processed by users.
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Johnson, Samuel G. B., e Woo-kyoung Ahn. Causal Mechanisms. A cura di Michael R. Waldmann. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780199399550.013.12.
Testo completoAbstract (sommario):
This chapter reviews empirical and theoretical results concerning knowledge of causal mechanisms—beliefs about how and why events are causally linked. First, it reviews the effects of mechanism knowledge, showing that mechanism knowledge can override other cues to causality (including covariation evidence and temporal cues) and structural constraints (the Markov condition), and that mechanisms play a key role in various forms of inductive inference. Second, it examines several theories of how mechanisms are mentally represented—as associations, forces or powers, icons, abstract placeholders, networks, or schemas—and the empirical evidence bearing on each theory. Finally, it describes ways that people acquire mechanism knowledge, discussing the contributions from statistical induction, testimony, reasoning, and perception. For each of these topics, it highlights key open questions for future research.
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Liebenthal, Einat, e Lynne E. Bernstein, a cura di. Neural Mechanisms of Perceptual Categorization as Precursors to Speech Perception. Frontiers Media SA, 2017. http://dx.doi.org/10.3389/978-2-88945-158-6.
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Gauffin, Jan, e Britta Hammarberg. Vocal Fold Physiology: Acoustic, Perceptual, and Physiological Aspects of Voice Mechanisms. Singular Publishing Group, 1991.
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Mattavelli, Giulia, Alessia Celeghin e Noemi Mazzoni, a cura di. Explicit and Implicit Emotion Processing: Neural Basis, Perceptual and Cognitive Mechanisms. Frontiers Media SA, 2021. http://dx.doi.org/10.3389/978-2-88966-177-0.
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Centre for Vision Research International Conference on Perceptual Organization. Centre for Vision Research, York University, 2015. http://dx.doi.org/10.25071/10315/39500.
Testo completoAbstract (sommario):
A principal challenge for both human and machine vision systems is to integrate and organize the diversity of cues received from the environment into the coherent global representations required to make good decisions and take effective actions. This conference brings together an interdisciplinary roster of leading researchers in both biological and computer vision to report and discuss the latest research on this process of perceptual organization.
Capitoli di libri sul tema "Perceptual cues and mechanisms"
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Picinali, Lorenzo, e Brian F. G. Katz. "System-to-User and User-to-System Adaptations in Binaural Audio". In Sonic Interactions in Virtual Environments, 115–43. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-04021-4_4.
Testo completoAbstract (sommario):
AbstractThis chapter concerns concepts of adaption in a binaural audio context (i.e. headphone-based three-dimensional audio rendering and associated spatial hearing aspects), considering first the adaptation of the rendering system to the acoustic and perceptual properties of the user, and second the adaptation of the user to the rendering quality of the system. We start with an overview of the basic mechanisms of human sound source localisation, introducing expressions such as localisation cues and interaural differences, and the concept of the Head-Related Transfer Function (HRTF), which is the basis of most 3D spatialisation systems in VR. The chapter then moves to more complex concepts and processes, such as HRTF selection (system-to-user adaptation) and HRTF accommodation (user-to-system adaptation). State-of-the-art HRTF modelling and selection methods are presented, looking at various approaches and at how these have been evaluated. Similarly, the process of HRTF accommodation is detailed, with a case study employed as an example. Finally, the potential of these two approaches are discussed, considering their combined use in a practical context, as well as introducing a few open challenges for future research.
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Jansson, Gunnar. "Perceptual Theory and Sensory Substitution". In Brain Mechanisms and Spatial Vision, 451–65. Dordrecht: Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5071-9_18.
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Logothetis, Nikos K., David A. Leopold e David L. Sheinberg. "6. Neural mechanisms of perceptual organization". In Neural Basis of Consciousness, 87–103. Amsterdam: John Benjamins Publishing Company, 2003. http://dx.doi.org/10.1075/aicr.49.09log.
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Siegert, Ingo, Oliver Jokisch, Alicia Flores Lotz, Franziska Trojahn, Martin Meszaros e Michael Maruschke. "Acoustic Cues for the Perceptual Assessment of Surround Sound". In Speech and Computer, 65–75. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-66429-3_6.
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Paplu, S., H. Ahmed, A. Ashok, S. Akkus e K. Berns. "Multimodal Perceptual Cues for Context-Aware Human-Robot Interaction". In Proceedings of SYROM 2022 & ROBOTICS 2022, 283–94. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-25655-4_29.
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He, Entang, Jing Lin, Zhejun Liu e Yize Zhang. "Research on Perceptual Cues of Interactive Narrative in Virtual Reality". In Human Interface and the Management of Information. Information Presentation and Visualization, 283–96. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-78321-1_22.
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Bazely, D. R. "Rules and Cues Used by Sheep Foraging in Monocultures". In Behavioural Mechanisms of Food Selection, 343–67. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-75118-9_18.
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Bharucha, J. J. "Cognitive and brain mechanisms in perceptual learning". In Music, Language, Speech and Brain, 349–58. London: Macmillan Education UK, 1991. http://dx.doi.org/10.1007/978-1-349-12670-5_33.
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Trevarthen, Colwyn B. "Neuroembryology and the Development of Perceptual Mechanisms". In Postnatal Growth Neurobiology, 301–83. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4899-0522-2_13.
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Sahoo, Somnath, e Kongara Hanumantha Rao. "Molecular Cues and Mechanisms of Pathogenesis in Candida". In Recent Advances in Human Fungal Diseases, 157–73. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-4909-6_6.
Testo completoAtti di convegni sul tema "Perceptual cues and mechanisms"
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Hoque, Adila, Seok Hun Kim e Kyle B. Reed. "Gait Response to Rhythmic Cues: Influence of Adaptation Mechanisms and Entrainment Levels". In 2024 46th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 1–6. IEEE, 2024. https://doi.org/10.1109/embc53108.2024.10782901.
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Feit, Andrew, e Berenice Mettler. "Information-Based Analysis of Visual Cues in Human Guidance". In Vertical Flight Society 72nd Annual Forum & Technology Display, 1–13. The Vertical Flight Society, 2016. http://dx.doi.org/10.4050/f-0072-2016-11578.
Testo completoAbstract (sommario):
Perception plays a central role in such humans' motion guidance skills as precision rotorcraft landing or driving a car. This paper investigates the information available in visible cues, relative to a first-person motion guidance task, in terms of sensory-motor guidance primitives. Human subjects performed a motion guidance task in a 3D simulation system, using only visual information. Guidance primitive patterns were identified from recorded subject motion and perception behavior. Information transfer between visual measurements and vehicle motion is quantified from the resulting data to identify both model-based and nonrepresentational guidance strategies. Results show that subjects use separate guidance primitive modes during distinct phases of a trajectory. This understanding of perceptual and guidance primitive elements in human behavior has applications ranging from improved augmented cuing for human pilots to advancing artificial perception in autonomous vehicle systems.
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Verma, Abhishek, e Berenice Mettler. "Analysis of Human Guidance and Perceptual Behavior in Navigation of Unknown Environments". In Vertical Flight Society 72nd Annual Forum & Technology Display, 1–11. The Vertical Flight Society, 2016. http://dx.doi.org/10.4050/f-0072-2016-11526.
Testo completoAbstract (sommario):
The human brain is able to generate guidance strategies in unknown environments and improve performance over multiple trials. Such capabilities are challenging to implement in autonomous systems. This research uses a computational framework based on a spatial value function and invariants, described as interaction patterns, in the function to investigate human planning and learning in unknown environments. A simulation system was used for human guidance experiments in a simulated obstacle field unknown to the subjects before the experiments. The system recorded vehicle trajectory, control inputs, and human gaze over multiple trials, between specified start and goal locations. Human guidance policy is evaluated in comparison with an optimal control baseline, formulated using interaction patterns in a Dubins optimal solution. The subjects' control characteristics explain why exploratory behavior varies from one individual to the next. The authors utilize gaze spatial density and an information gain model, employing gaze location data, to investigate the visual cues that support guidance and navigation.
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Morcos, Michael, Edward Bachelder, Martine Godfroy-Cooper, Spencer Fishman e Umberto Saetti. "Full-Body Haptic and Spatial Audio Cueing Algorithms for Augmented Pilot Perception". In Vertical Flight Society 80th Annual Forum & Technology Display, 1–18. The Vertical Flight Society, 2024. http://dx.doi.org/10.4050/f-0080-2024-1179.
Testo completoAbstract (sommario):
This paper illustrates the development, implementation, and testing of full-body haptic and spatial audio cueing algorithms for augmented pilot perception. Cueing algorithms are developed for roll-axis compensatory tracking tasks where the pilot acts on the displayed error between a desired input and the comparable vehicle output motion to produce a control action. The error is displayed to the pilot using multiple cueing modalities: visual, haptic, audio, and combinations of these. For the visual and combined visual haptic/audio modalities, visual cues are also considered in degraded visual environments (DVE). Full-body haptic and spatial audio algorithms that are based on a proportional derivative (PD) compensation strategy on the tracking error are found to provide satisfactory pilot vehicle system (PVS) performance for the task in consideration in absence of visual cueing, and to improve PVS performance in DVE when used in combination with visual feedback. These results are consistent with previous studies on the use of secondary perceptual cues for augmentation of human perception. The combination of these results indicate that the use of secondary sensory cues such as full-body haptics and spatial audio to augment the pilot perception can lead to improved/partially-restored PVS performance when primary sensory cues like vision are impaired or denied.
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Rampane, Liga, Zane Zelca e Chaima Salmi. "POLYLACTIC ACID/ZINC OXIDE NANOSTRUCTURED FIBROUS MATERIAL BY NEEDLELESS ONE SOLVENT ELECTROSPINNING FOR PROTECTION AGAINST TICK-BORNE DISEASES". In SGEM International Multidisciplinary Scientific GeoConference 24, 69–76. STEF92 Technology, 2024. https://doi.org/10.5593/sgem2024/6.1/s24.12.
Testo completoAbstract (sommario):
Ticks (Ixodidae and Argasidae) pose significant health risks as vectors for infectious diseases, with their prevalence expanding across Europe and North America. Ticks employ sophisticated sensory mechanisms, notably utilizing Haller's organs, to locate and sense their hosts. These sensory structures detect various cues, including chemosensation, changes in atmospheric CO2 concentration, and radiant heat emitted by potential hosts. Once a host is detected, landing is facilitated by electrostatic attraction, accelerating the precise positioning of the tick for feeding. Reports indicate that ZnO nanoparticles exhibit acaricidal activity. The strong thermal and electrical conductivity of ZnO may effectively impede tick host-seeking mechanisms. This study focuses on fabricating ZnO-containing nanostructured polylactic acid (PLA) fiber material for tick repellency. In this research, acetone, chosen for its low toxicity and compatibility with natural acaricides, is utilized in a single-solvent system to produce nanofibers with long-lasting acaricidal properties. Successful electrospinning of acetone-based systems has been limited to needle electrospinning. Here, we present a method employing needleless electrospinning to fabricate ZnO nanoparticle-loaded PLA nanofibers by using pike-type electrode. The PLA-ZnO solutions were characterized by density, conductivity, viscosity, and other parameters, while the resulting fiber mats underwent analysis via FTIR, SEM, and evaluation of thermal conductivity. Optimization of spinning parameters including critical voltage, collector distance, and environmental factors such as temperature and humidity was conducted. Our study demonstrates the creation of PLA-ZnO fibers in a single solvent system through needleless electrospinning. Obtained membranes contain 1-3 wt% ZnO within an 8-10 wt% PLA matrix solution and exhibit heightened electrical conductivity. This advancement underscores the potential of ZnO in tick-repellent materials and strategies against tick-borne diseases.
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Dansie, Christopher, e Don R. Brown. "Visualizing Sequential Information With Perceptual Cues". In ASME 1999 Design Engineering Technical Conferences. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/detc99/eim-9027.
Testo completoAbstract (sommario):
Abstract A new visualization technique is presented that utilizes interactive three-dimensional graphics and perceptual cues to visualize unstructured, sequential data. Upon evaluation the optimum values, trends and relationships between segments and sequences are quickly seen using the perceptual abilities of the human visual system. This research is applied to visualizing logistics information, were decisions are made based upon multivariate, and sequential information. Using this technique the user can analyze route parameters visually rather than computationally to aid in the decision making process. The visualization is accomplished through a custom software system written in Java utilizing the Java3D API to generate the three-dimensional visualization.
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Rezaeirowshan, Babak, Coloma Ballester e Gloria Haro. "Monocular Depth Ordering using Perceptual Occlusion Cues". In International Conference on Computer Vision Theory and Applications. SCITEPRESS - Science and Technology Publications, 2016. http://dx.doi.org/10.5220/0005726404310441.
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Sherrah, J., e S. Gong. "Fusion of Perceptual Cues using Covariance Estimation". In British Machine Vision Conference 1999. British Machine Vision Association, 1999. http://dx.doi.org/10.5244/c.13.56.
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Chaida, Anthi. "Perceptual cues for sentence intonation in Greek". In 3rd Tutorial and Research Workshop on Experimental Linguistics. ExLing Society, 2019. http://dx.doi.org/10.36505/exling-2010/03/0006/000126.
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Krahmer, Emiel, Zsófia Ruttkay, Marc Swerts e Wieger Wesselink. "Perceptual evaluation of audiovisual cues for prominence". In 7th International Conference on Spoken Language Processing (ICSLP 2002). ISCA: ISCA, 2002. http://dx.doi.org/10.21437/icslp.2002-436.
Testo completoRapporti di organizzazioni sul tema "Perceptual cues and mechanisms"
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Ditterich, Jochen. Neural and Computational Mechanisms of Perceptual Decisions Between Multiple Alternatives Based on Multiple Sources of Evidence. Fort Belvoir, VA: Defense Technical Information Center, luglio 2010. http://dx.doi.org/10.21236/ada567245.
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Samach, Alon, Douglas Cook e Jaime Kigel. Molecular mechanisms of plant reproductive adaptation to aridity gradients. United States Department of Agriculture, gennaio 2008. http://dx.doi.org/10.32747/2008.7696513.bard.
Testo completoAbstract (sommario):
Annual plants have developed a range of different mechanisms to avoid flowering (exposure of reproductive organs to the environment) under adverse environmental conditions. Seasonal environmental events such as gradual changes in day length and temperature affect the timing of transition to flowering in many annual and perennial plants. Research in Arabidopsis and additional species suggest that some environmental signals converge on transcriptional regulation of common floral integrators such as FLOWERING LOCUS T (FT). Here we studied environmental induction of flowering in the model legume Medicago truncatula. Similarly to Arabidopsis, the transition to flowering in M. truncatula is hastened by long photoperiods and long periods of vernalization (4°C for 2-3 weeks). Ecotypes collected in Israel retain a vernalization response even though winter temperatures are way above 4°C. Here we show that this species is also highly responsive (flowers earlier) to mild ambient temperatures up to 19°C simulating winter conditions in its natural habitat. Physiological experiments allowed us to time the transition to flowering due to low temperatures, and to compare it to vernalization. We have made use of natural variation, and induced mutants to identify key genes involved in this process, and we provide here data suggesting that an FT gene in M.truncatula is transcriptionally regulated by different environmental cues. Flowering time was found to be correlated with MtFTA and MtFTB expression levels. Mutation in the MtFTA gene showed a late flowering phenotype, while over-expressing MtFTA in Arabidopsis complemented the ft- phenotype. We found that combination of 4°C and 12°C resulted in a synergistic increase in MtFTB expression, while combining 4°C and long photoperiods caused a synergistic increase in MtFTA expression. These results suggest that the two vernalization temperatures work through distinct mechanisms. The early flowering kalil mutant expressed higher levels of MtFTA and not MtFTB suggesting that the KALIL protein represses MtFTA specifically. The desert ecotype Sde Boker flowers earlier in response to short treatments of 8-12oc vernalization and expresses higher levels of MtFTA. This suggests a possible mechanism this desert ecotype developed to flower as fast as possible and finish its growth cycle before the dry period. MtFTA and FT expression are induced by common environmental cues in each species, and expression is repressed under short days. Replacing FT with the MtFTA gene (including regulatory elements) caused high MtFTA expression and early flowering under short days suggesting that the mechanism used to repress flowering under short days has diversified between the two species.The circadian regulated gene, GIGANTEA (GI) encodes a unique protein in Arabidopsis that is involved in flowering mechanism. In this research we characterized how the expression of the M.truncatula GI ortholog is regulated by light and temperature in comparison to its regulation in Arabidopsis. In Arabidopsis GI was found to be involved in temperature compensation to the clock. In addition, GI was found to be involved in mediating the effect of temperature on flowering time. We tested the influence of cold temperature on the MtGI gene in M.truncatula and found correlation between MtGI levels and extended periods of 12°C treatment. MtGI elevation that was found mostly after plants were removed from the cold influence preceded the induction of MtFT expression. This data suggests that MtGI might be involved in 12°C cold perception with respect to flowering in M.truncatula. GI seems to integrate diverse environmental inputs and translates them to the proper physiological and developmental outputs, acting through several different pathways. These research enabled to correlate between temperature and circadian clock in M.truncatula and achieved a better understanding of the flowering mechanism of this species.
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Savaldi-Goldstein, Sigal, e Siobhan M. Brady. Mechanisms underlying root system architecture adaptation to low phosphate environment. United States Department of Agriculture, gennaio 2015. http://dx.doi.org/10.32747/2015.7600024.bard.
Testo completoAbstract (sommario):
In order to advance our understanding towards potential biotechnology improvement of plant performance, we studied root responses to limited P in two different plants, Arabidopsis and tomato. Arabidopsis is among the most studied model plants that allows rapid application of molecular and developmental experiments while tomato is an important crop, with application in agriculture. Using Arabidopsis we found that steroid hormones modulate the extent of root elongation in response to limited P, by controlling the accumulation of iron in the root. We also found that the availability of P and iron control the activity of the steroid hormone in the root. Finally, we revealed the genes involved in this nutrient-hormone interaction. Hence, the ferroxidase LPR1 that promotes iron accumulation in response to low P is repressed by the transcription factor BES1/BZR1. Low P inhibits the steroid hormone pathway by enhancing the accumulation of BKI1. High levels of BKI1 inhibit the activity of the steroid hormone receptor at the cell surface and iron accumulation increases inside the root, resulting in a slow growth. Together, the extent of root elongation depends on interactions between an internal cue (steroid hormone) and cues derived from the availability of P and iron in the environment. Using tomato, we found that the response of two cultivated tomato varieties (M82 and New Yorker) to limited P is distinct from that of the wild species, Solanumpennellii. This is implicated at both the levels of root development and whole plant physiology. Specifically, while the root system architecture of cultivated tomato is modulated by limited P availability, that of the wild type species remained unaffected. The wild species appears to be always behaving as if it is always in phosphate deprived conditions, despite sufficient levels of phosphate. Hyper-accumulation of metals appears to mediate this response. Together, this knowledge will be used to isolate new genes controlling plant adaptation to limited P environment.
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Wagner, D. Ry, Eliezer Lifschitz e Steve A. Kay. Molecular Genetic Analysis of Flowering in Arabidopsis and Tomato. United States Department of Agriculture, maggio 2002. http://dx.doi.org/10.32747/2002.7585198.bard.
Testo completoAbstract (sommario):
The primary objectives for the US lab included: the characterization of ELF3 transcription and translation; the creation and characterization of various transgenic lines that misexpress ELF3; defining genetic pathways related to ELF3 function regulating floral initiation in Arabidopsis; and the identification of genes that either interact with or are regulated by ELF3. Light quality, photoperiod, and temperature often act as important and, for some species, essential environmental cues for the initiation of flowering. However, there is relatively little information on the molecular mechanisms that directly regulate the developmental pathway from the reception of the inductive light signals to the onset of flowering and the initiation of floral meristems. The ELF3 gene was identified as possibly having a role in light-mediated floral regulation since elj3 mutants not only flower early, but exhibit light-dependent circadian defects. We began investigating ELF3's role in light signalling and flowering by cloning the ELF3 gene. ELF3 is a novel gene only present in plant species; however, there is an ELF3 homolog within Arabidopsis. The Arabidopsis elj3 mutation causes arrhythmic circadian output in continuous light; however, we show conclusively normal circadian function with no alteration of period length in elj3 mutants in dark conditions and that the light-dependent arrhythmia observed in elj3 mutants is pleiotropic on multiple outputs regardless of phase. Plants overexpressing ELF3 have an increased period length in constant light and flower late in long-days; furthermore, etiolated ELF3-overexpressing seedlings exhibit a decreased acute CAB2 response after a red light pulse, whereas the null mutant is hypersensitive to acute induction. This finding suggests that ELF3 negatively regulates light input to both the clock and its outputs. To determine whether ELF3's action is phase dependent, we examined clock resetting by light pulses and constructed phase response curves. Absence of ELF3 activity causes a significant alteration of the phase response curve during the subjective night, and overexpression of ELF3 results in decreased sensitivity to the resetting stimulus, suggesting that ELF3 antagonizes light input to the clock during the night. Indeed, the ELF3 protein interacts with the photoreceptor PHYB in the yeast two-hybrid assay and in vitro. The phase ofELF3 function correlates with its peak expression levels of transcript and protein in the subjective night. ELF3 action, therefore, represents a mechanism by which the oscillator modulates light resetting. Furthermore, flowering time is dependent upon proper expression ofELF3. Scientifically, we've made a big leap in the understanding of the circadian system and how it is coupled so tightly with light reception in terms of period length and clock resetting. Agriculturally, understanding more about the way in which the clock perceives and relays temporal information to pathways such as those involved in the floral transition can lead to increased crop yields by enabling plants to be grown in suboptimal conditions.
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Eshed-Williams, Leor, e Daniel Zilberman. Genetic and cellular networks regulating cell fate at the shoot apical meristem. United States Department of Agriculture, gennaio 2014. http://dx.doi.org/10.32747/2014.7699862.bard.
Testo completoAbstract (sommario):
The shoot apical meristem establishes plant architecture by continuously producing new lateral organs such as leaves, axillary meristems and flowers throughout the plant life cycle. This unique capacity is achieved by a group of self-renewing pluripotent stem cells that give rise to founder cells, which can differentiate into multiple cell and tissue types in response to environmental and developmental cues. Cell fate specification at the shoot apical meristem is programmed primarily by transcription factors acting in a complex gene regulatory network. In this project we proposed to provide significant understanding of meristem maintenance and cell fate specification by studying four transcription factors acting at the meristem. Our original aim was to identify the direct target genes of WUS, STM, KNAT6 and CNA transcription factor in a genome wide scale and the manner by which they regulate their targets. Our goal was to integrate this data into a regulatory model of cell fate specification in the SAM and to identify key genes within the model for further study. We have generated transgenic plants carrying the four TF with two different tags and preformed chromatin Immunoprecipitation (ChIP) assay to identify the TF direct target genes. Due to unforeseen obstacles we have been delayed in achieving this aim but hope to accomplish it soon. Using the GR inducible system, genetic approach and transcriptome analysis [mRNA-seq] we provided a new look at meristem activity and its regulation of morphogenesis and phyllotaxy and propose a coherent framework for the role of many factors acting in meristem development and maintenance. We provided evidence for 3 different mechanisms for the regulation of WUS expression, DNA methylation, a second receptor pathway - the ERECTA receptor and the CNA TF that negatively regulates WUS expression in its own domain, the Organizing Center. We found that once the WUS expression level surpasses a certain threshold it alters cell identity at the periphery of the inflorescence meristem from floral meristem to carpel fate [FM]. When WUS expression highly elevated in the FM, the meristem turn into indeterminate. We showed that WUS activate cytokinine, inhibit auxin response and represses the genes required for root identity fate and that gradual increase in WUCHEL activity leads to gradual meristem enlargement that affect phyllotaxis. We also propose a model in which the direction of WUS domain expansion laterally or upward affects meristem structure differently. We preformed mRNA-seq on meristems with different size and structure followed by k-means clustering and identified groups of genes that are expressed in specific domains at the meristem. We will integrate this data with the ChIP-seq of the 4 TF to add another layer to the genetic network regulating meristem activity.