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About 10,000 papers for “Visual processing”

Visual Processing By Adaptive Decorrelation

William D. Ross · 1996

Visual processing provides organisms with behaviorally relevant information about what is where in their environments. Challenges including environmental variability, and limitations on processing time and capacity make this task difficult. A model is presented which suggests how the visual system copes with these challenges by both passive and active mechanisms which work to decorrelate system responses to events that demand different behavioral responses. Passive mechanisms decorrelate neural responses along significant feature dimensions in parallel across image space. While limited foveal and attentional resources are actively deployed to locate and recognize objects. It is proposed that attention acts to select those features and regions which can best resolve behavioral uncertainties. Operationally, limited resources are deployed to regions or feature dimensions for which competing interpretations make contradictory predictions. It is this information that can best decorrelate ca...

Cited by 0

Ontology based visual information processing

Christopher Phillip Town · 2004

Despite the dramatic growth of digital image and video data in recent years, many challenges remain in enabling computers to interpret visual content. This thesis addresses the problem of how high-level representations of visual data may be automatically derived by integrating different kinds of evidence and incorporating prior knowledge. A central contribution of the thesis is the development and realisation of an inference framework for computer vision founded on the application of ontologies and ontological languages as a novel methodology for active knowledge representation. Three applications of the approach are presented: The first describes a novel query paradigm called OQUEL (ontological query language) for the content-based retrieval of images. The language is based on an extensible ontology which encompasses both high-level and low-level visual properties and relations. Query sentences are prescriptions of desired image content in terms of English language words. The second application extends the notion of ontological query languages to the field of automatic event detection from video footage. It is shown how the

Cited by 0

Cortical Dynamics in Visual Processing

Kimberly Reinhold · eScholarship (California Digital Library) · 2015

Recurrent circuits are a hallmark of mammalian sensory cortex. How they impact dynamics of sensory representation is not understood. Because recurrent circuits provide a majority of the synaptic excitation to cortical neurons in response to sensory stimulation, the intrinsic dynamics of these cortical recurrent circuits are expected to be a critical determinant of the timing of the sensory response in cortex. Previous methods could not isolate dynamics of these intra-cortical recurrent circuits from those of thalamic afferents during sensory processing. I now accomplish this by developing an approach to optogenetically silence thalamus in a model system: the mouse visual pathway. Silencing thalamus revealed the time course over which visually evoked activity in visual cortex was maintained by the intra-cortical recurrent circuits themselves, in isolation from thalamic input. I found that, at all time points during the cortical sensory-evoked response, optogenetically silencing thalamus led to a fast decay of sensory-evoked activity in cortical recurrent circuits. This activity decay time course was fit by a 10 ms network time constant, similar to a neuron’s integration time window. This decay time course was invariant across all tested visual stimulation conditions and behavioral states but depended on cortical inhibition. In awake mice, the dynamics of this time course predicted the time-locking of cortical activity to thalamic input at frequencies <15 Hz and the attenuation of the cortical response to higher frequencies. Under anesthesia, however, dynamics of depression at thalamocortical synapses disrupted the fidelity of sensory transmission. Thus, I determine sensory-evoked dynamics intrinsic to the intra-cortical recurrent circuits in isolation from thalamus and show how these dynamics transform afferent input in time.

Cited by 0Open access

Conditioned Sounds Enhance Visual Processing

Fabrizio Leo, Uta Noppeney · PLoS ONE · 2014

This psychophysics study investigated whether prior auditory conditioning influences how a sound interacts with visual perception. In the conditioning phase, subjects were presented with three pure tones ( = conditioned stimuli, CS) that were paired with positive, negative or neutral unconditioned stimuli. As unconditioned reinforcers we employed pictures (highly pleasant, unpleasant and neutral) or monetary outcomes (+50 euro cents, -50 cents, 0 cents). In the subsequent visual selective attention paradigm, subjects were presented with near-threshold Gabors displayed in their left or right hemifield. Critically, the Gabors were presented in synchrony with one of the conditioned sounds. Subjects discriminated whether the Gabors were presented in their left or right hemifields. Participants determined the location more accurately when the Gabors were presented in synchrony with positive relative to neutral sounds irrespective of reinforcer type. Thus, previously rewarded relative to neutral sounds increased the bottom-up salience of the visual Gabors. Our results are the first demonstration that prior auditory conditioning is a potent mechanism to modulate the effect of sounds on visual perception.

Cited by 12Open access

Intracortical Interactions in Visual Processing

J. I. Nelson · 1986

Abstract : Microelectrodes were used to record responses from single cells in the visual system of cats, at the level of the visual cortex. Interactions were discovered and measured between the cell under study and neighboring cells, when these neighbors were stimulated with large patterns. The interactions obey specific rules. It is argued that these rules are ideal for separating and strengthening the neural response to one object from the response of myriad other neurons to a cluttered background. The next step in this project will be multielectrode array studies to isolate and identify the neurons participating in these interactions.

Cited by 0

Visual Communications and Image Processing

Visual Communications and Image Processing · 2023

In view of the scratches and red spots caused by the impact of time, environment and shooting equipment on the old photos, this paper uses MATLAB as image processing simulation software to carry out the research and implementation of image inpainting algorithm.By comparing and analyzing the repair effect and operational efficiency of the three basic models based on partial differential equations: BSCB model, TV model, and CDD model, the method of introducing weights into the TV model is selected to perform simple repair on color photos and black and white photos with scratches and red dots, and the repair results of old photos are presented through the MATLAB GUI interface.The experimental results show that the introduction of weight values in the TV model not only has a significant effect on solving the problem of unidirectional extension of the equal illuminance line in the TV model, but also has a good effect on repairing scratches and red dots in small-scale color and black and white photos.

Cited by 24Open access

Serotonergic modulation of visual processing

Mir-Shahram Safari · Neuroscience and Neurological Surgery · 2024

Neuromodulators are chemicals that alter the activity of neural networks. They can have -immediate or delayed effects on neurons, affecting their properties at both nearby and distant synapses. Neuromodulators can influence neurons in various ways, allowing even small neural Networks generate a diverse range of functional outcomes. This diversity is crucial for the flexibility and adaptability of neural functions, including sensory processing.

Cited by 0Open access

Early processing of visual information

David Marr · Philosophical transactions of the Royal Society of London. Series B, Biological sciences · 1976

Abstract An introduction is given to a theory of early visual information processing. The theory has been implemented, and examples are given of images at various stages of analysis. It is argued that the first step of consequence is to compute a primitive but rich description of the grey-level changes present in an image. The description is expressed in a vocabulary of kinds of intensity change (EDGE, SHADING-EDGE, EXTENDED-EDGE, LINE, BLOB etc.). Modifying parameters are bound to the elements in the description, specifying their POSITION, ORIENTATION, TERMINATION points, CONTRAST, SIZE and FUZZINESS. This description is obtained from the intensity array by fixed techniques, and it is called the primal sketch. For most images, the primal sketch is large and unwieldy. The second important step in visual information processing is to group its contents in a way that is appropriate for later recognition. From our ability to interpret drawings with little semantic content, one may infer the presence in our perceptual equipment of symbolic processes that can define ‘ placetokens’ in an image in various ways, and can group them according to certain rules. Homomorphic techniques fail to account for many of these grouping phenomena, whose explanations require mechanisms of construction rather than mechanisms of detection. The necessary grouping of elements in the primal sketch may be achieved by a mechanism that has available the processes inferred from above, together with the ability to select items by first order discriminations acting on the elements’ parameters. Only occasionally do these mechanisms use downward-flowing information about the contents of the particular image being processed. It is argued that ‘non-attentive’ vision is in practice implemented by these grouping operations and first order discriminations acting on the primal sketch. The class of computations so obtained differs slightly from the class of second order operations on the intensity array. The extraction of a form from the primal sketch using these techniques amounts to the separation of figure from ground. It is concluded that most of the separation can be carried out by using techniques that do not depend upon the particular image in question. Therefore, figure-ground separation can normally precede the description of the shape of the extracted form. Up to this point, higher-level knowledge and purpose are brought to bear on only a few of the decisions taken during the processing. This relegates the widespread use of downward-flowing information to a later stage than is found in current machine-vision programs, and implies that such knowledge should influence the control of, rather than interfering with, the actual data-processing that is taking place lower down.

Cited by 1,042

Introduction to visual data processing

Arbeitsgemeinschaft fuer Wirtschaftliche Verwaltung e.V. (AWV), Eschborn (Germany) · OpenGrey (Institut de l'Information Scientifique et Technique) · 1985

Copy held by FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische Informationsbibliothek

Cited by 0

Visual Speech Processing and Recognition

Constantine Kotropoulos, Ioannis Pitas · IGI Global eBooks · 2009

This chapter addresses both low- and high-level problems in visual speech processing and recognition In particular, mouth region segmentation and lip contour extraction are addressed first. Next, visual speech recognition with parallel support vector machines and temporal Viterbi lattices is demonstrated on a small vocabulary task.

Cited by 0

Emotions in visual word processing

Annekathrin Schacht · edoc Publication server (Humboldt University of Berlin) · 2008

Die Einflüsse von Emotionen auf Informationsverarbeitungsprozesse zählen zu einem der zentralen Aspekte kognitionspsychologischer und neurowissenschaftlicher Forschung. Studien zur Prozessierung affektiver Bilder und emotionaler Gesichtsausdrücke haben gezeigt, daß emotionale Stimuli – vermutlich aufgrund ihrer starken intrinsischen Relevanz für den Organismus – in besonderem Maße Aufmerksamkeit binden und hierdurch einer präferierten und elaborierteren Weiterverarbeitung zugeführt werden. Evidenz zur Aktivierung und Verarbeitung emotionaler Valenz in der visuellen Wortverarbeitung ist hingegen gering und größtenteils inkonsistent. In einer Serie von Experimenten, die in der vorliegenden Arbeit zusammenfassend beschrieben und diskutiert werden, wurde mit Hilfe Ereigniskorrelierter Potentiale (EKPs) versucht, die Effekte emotionaler Valenz von deutschsprachigen Verben innerhalb des Wortverarbeitungsprozesses zu lokalisieren. In den EKPs zeigen sich – hinsichtlich ihrer Latenz und Topographie – dissoziierbare emotionsrelatierte Komponenten, die mit unterschiedlichen Stufen der Verarbeitungsprozesse in Verbindung gebracht werden können. Die Befunde legen nahe, daß die emotionale Valenz von Verben auf einer (post-) lexikalischen Verarbeitungsstufe aktiviert wird. Dieser frühen Registrierung liegen wahrscheinlich domänenunspezifische neuronale Mechanismen zugrunde, die weitestgehend ressourcen- und aufgabenunabhängig wirken. Auf späteren Stufen hingegen scheinen emotions-relatierte Prozesse durch zahlreiche weitere Faktoren beeinflußt zu werden. Die Modulation der Dynamik früher, nicht aber später Emotionsprozessierung durch nicht-valente Kontextinformation sowie in Abhängigkeit der Stimulusdomäne legt einen zeitlich variablen Verarbeitungsprozeß emotionaler Information nahe, der mit streng seriellen Modellen der Informationsverarbeitung nicht vereinbar ist, und möglicherweise der flexiblen Verhaltensanpassung an verschiedene Umweltbedingungen dient.

Cited by 0Open access

Visual exploration of XQuery processing

Michal Andrzej. Dobosz · Digital WPI · 2004

This project involves the creation of a graphical user interface for XEAR, the XML To SQL Translation System. This graphical user interface shows the process of converting an XML Query into an SQL Query, having that query being applied to a relational database, and finally producing an XML document as the result. The foremost goal of this project is to showcase the entire process so that the user can understand and appreciate what is happening.

Cited by 0