Burr DC, Ross J., MORRONE, MARIA CONCETTA · CINECA IRIS Institutial research information system (University of Pisa) · 1986
The fundamental sinusoidal components of a chequerboard pattern are oriented at 45 degrees to the orientation of the chequerboard edges. Removal of one of the fundamental sinusoids (at +45 degrees) creates a useful pattern for studying the mechanisms of visual analysis. Close up, the pattern appears to be oriented +45 degrees, although there is no global energy at that orientation, implying local analysis. At a distance, the perceived diagonality switches to -45 degrees implying access to global information. Measurements show that contrast thresholds for seeing diagonality at +45 degrees follow closely those for detecting the 5th harmonic component of the pattern, over a wide range of spatial frequencies and luminances. Low pass filtering also causes the pattern to be perceived according to its global energy, provided that the cutoff frequency is set to remove the fifth harmonic. We conclude that, at least for this particular stimulus, the visual system performs a local analysis if the fifth harmonic is visible and a global analysis if not.
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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
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S. J. Grice, M. W. Spratling, A. Karmiloff-Smith et al. · 2001
Two developmental disorders, autism and Williams Syndrome, are both commonly described as having difficulties in integrating perceptual features, i.e., binding spatially separate elements into a whole. It is already known that healthy adults and infants display electroencephalographic (EEG) gamma band bursts (around 40Hz) when the brain is required to achieve such binding . Here we explore gamma band EEG in autism and Williams Syndrome and demonstrate differential abnormalities in the two phenotypes. We show that despite putative processing similarities at the cognitive level, binding in Williams Syndrome and autism can be dissociated at the neurophysiological level by different abnormalities in underlying brain oscillatory activity. Our study is the first to identify that binding related gamma EEG can be disordered in humans.
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Author(s Elliott Mark, J. Synchronization, E. Schröger et al. · 2003
Provided by the author(s) and NUI Galway in accordance with publisher policies. Please cite the published
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Urs Schwarz, Uwe J. Ilg · Neuroreport · 1999
The smooth pursuit system is traditionally employed using a single small target moving on a homogeneous background. It still is not fully understood, however, how accurate tracking is sustained in the presence of a structured background, which will activate global motion processing in the opposite direction as a consequence of the ongoing eye movement. To further study this interaction, we used brief shifts of a textured background injected at various times during the initiation of smooth pursuit. While shifts opposite to the target direction did not alter smooth pursuit performance, those in the same direction resulted in a marked transient perturbation of the pursuit. These results suggest a simple yet limited mechanism that adjusts the sensitivity of global motion processing.
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Colorado State University · PsycEXTRA Dataset · 1997
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William H. Merigan · 2008
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Kaixin Shen, Honglei An, Yongshan Huang et al. · 2020
Finite state machine impedance control method has been applied extensively in prosthesis control. However, extensive parametric configurations are required. Forthermore, there is no uniform official joint trajectory curve available which must therefore be obtained through virtual constraints. Following complete data processing, parameter configuration is needed to adjust appropriate joint trajectory, and is extremely time intensive. This article provides a smarter GUI interface for data processing. A curve fitting method that can be modified in real time is proposed. This curve fitting method is based on Bezier least squares method and uses MATLAB software to construct a visual GUI with certain generalization ability. The final smooth curve data can be extracted. Experimental data is derived from the knee and ankle trajectories of human motion.
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Georges Grinstein, Robert F. Erbacher · 1998
Recent advances in concurrent architecture technology have led to a dramatic increase in the number of types of systems available as well as the number of systems in actual use. In contrast, software technology has not kept pace. Software tools have yet to be developed which fully compensate for the added difficulties and complexities inherent in programming concurrent architectures. Consequently, the tools used to aid in the development and debugging of applications for these types of architectures are often insufficient for the task. This makes it extremely difficult and time consuming to develop correct and efficient concurrent applications. The availability of high end graphics systems with most concurrent hardware provides an opportunity to extend development and debugging tools to use these graphics capabilities, where applicable.
In this research, we explored interactive computational steering, data analysis (as opposed to processor or control analysis), analysis of data operations, often using direct manipulation techniques, all in support of the development of concurrent applications.
We extended interactive computational steering beyond the ability to merely steer data values instantaneously. This resulted in techniques for the steering of operations, allowing the user to modify the application dynamically during execution. We also extended data steering to incorporate a persistent mode. In the persistent mode, once the user has specified the values for designated variable elements, the environment does not allow them to change.
Operation visualization techniques that are merged with the data display provide the user with a single focus and aid in the correlation of data, program status, and loop status information. The environment presents the operation visualizations in such a way that the user can also use them to debug the execution stack.
Finally, we show how users can apply the techniques developed during the course of this research to aid in the comprehension and debugging of concurrent programs. Examples show how the techniques can be used to find potential errors in two example concurrent applications or to verify that errors do not exist.
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Thomas D. Albright, Gene R. Stoner · Annual Review of Neuroscience · 2002
The visual image formed on the retina represents an amalgam of visual scene properties, including the reflectances of surfaces, their relative positions, and the type of illumination. The challenge facing the visual system is to extract the "meaning" of the image by decomposing it into its environmental causes. For each local region of the image, that extraction of meaning is only possible if information from other regions is taken into account. Of particular importance is a set of image cues revealing surface occlusion and/or lighting conditions. These information-rich cues direct the perceptual interpretation of other more ambiguous image regions. This context-dependent transformation from image to perception has profound-but frequently under-appreciated-implications for neurophysiological studies of visual processing: To demonstrate that neuronal responses are correlated with perception of visual scene properties, rather than visual image features, neuronal sensitivity must be assessed in varied contexts that differentially influence perceptual interpretation. We review a number of recent studies that have used this context-based approach to explore the neuronal bases of visual scene perception.
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A. H. C. van der Heijden · 1990
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Caitlin Williams Kiley, W. Martin Usrey · 2022
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B. G. Rosenberg · International Journal of Man-Machine Studies · 1971
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Society of Exploration Geophysicists eBooks · 2020
In this chapter we will pictorially review the algorithms that help convert field seismic data into subsurface images through after-stack migration. The figures on the right are taken from previous chapters in both volumes and illustrate key operations.
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2012
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Aman B. Saleem · Spiral (Imperial College London) · 2009
One of the goals of neuroscience is to understand how animals perceive sensory information. This thesis focuses on visual systems, to unravel how neuronal structures process aspects of the visual environment. To characterise the receptive field of a neuron, we developed spike-triggered independent component analysis. Alongside characterising the receptive field of a neuron, this method provides an insight into its underlying network structure. When applied to recordings from the H1 neuron of blowflies, it accurately recovered the sub-structure of the neuron. This sub-structure was studied further by recording H1's response to plaid stimuli. Based on the response, H1 can be classified as a component cell. We then fitted an anatomically inspired model to the response, and found the critical component to explain H1's response to be a sigmoid non-linearity at output of elementary movement detectors. The simpler blowfly visual system can help us understand elementary sensory information processing mechanisms. How does the more complex mammalian cortex implement these principles in its network? To study this, we used multi-electrode arrays to characterise the receptive field properties of neurons in the visual cortex of anaesthetised mice. Based on these recordings, we estimated the cortical limits on the performance of a visual task; the behavioural performance observed by Prusky and Douglas (2004) is within these limits. Our recordings were carried out in anaesthetised animals. During anaesthesia, cortical UP states are considered "fragments of wakefulness" and from simultaneous whole-cell and extracellular recordings, we found these states to be revealed in the phase of local field potentials. This finding was used to develop a method of detecting cortical state based on extracellular recordings, which allows us to explore information processing during different cortical states. Across this thesis, we have developed, tested and applied methods that help improve our understanding of information processing in visual systems.
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Feldmann, I., Kauff, P., Eisert, P. · Lecture notes in computer science · 2003
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Jayanta Mukhopadhyay, Shashaank Aswatha Mattur · 2025
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Massaro, Dominic W., Sanocki, Thomas · Digital Commons - University of South Florida (University of South Florida) · 1993
The first half of the title of this book, Visual Processes in Reading, might seem redundant because reading is necessarily a visual act. However, reading is influenced by nonvisual information. Our concern is with visual processing, but nonvisual information (in many different forms) contributes to our perceptual experience of reading text. The goal of this chapter is to present a theoretical framework for visual information processing in reading and to sample relevant research. After presenting the model, we address the issue of what visual information is used in word identification. The results are consistent with the view that identification of a word depends on processing its component letters. Therefore, it is important to describe the visual information contributing to letter recognition. After considering letter recognition per se, we discuss a way of using visual information to increase the amount of orthographic and phonological information conveyed by letters. Then we return to the observed perceptual advantage for words and consider competing theoretical explanations. In particular, we focus on an account that emphasizes knowledge of spelling regularities (orthographic structure) and an account that utilizes specific words. We evaluate these accounts in terms of how they handle effects of processing time and other variables in word perception tasks. Finally, we close with consideration of effects of the discourse context on word recognition.
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Salai Dhavamathi Janarthanan · The Ophthalmology - Open Journal · 2017
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