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2 edition of Effects of pixel noise and stimulus structure on visual detection performance. found in the catalog.

Effects of pixel noise and stimulus structure on visual detection performance.

Helja Tuulikki Kukkonen

Effects of pixel noise and stimulus structure on visual detection performance.

by Helja Tuulikki Kukkonen

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  • 35 Currently reading

Published by Aston University. Department of Vision Sciences in Birmingham .
Written in English


Edition Notes

Thesis (PhD) - Aston University, 1994.

ID Numbers
Open LibraryOL13843801M

Each stimulus movie subtended a visual angle of deg (76 × 76 monitor pixels). Movie duration was ms (16 frames at Hz). All stimuli were windowed with a .   Attention has also been shown to improve the perception of attended stimuli and consequently behavioral performance—likely by reducing noise, effects on performance visual stimulus to.

Smoothing the data reduces effects of image noise but introduces a larger partial-volume effect. Consequently, variations of the maximum pixel value with sphere or tumor size are substantial for both smoothed and nonsmoothed images, but the underlying mechanisms are different. For any electronic measuring system, the signal-to-noise ratio (SNR) characterizes the quality of a measurement and determines the ultimate performance of the system. Careful control of noise components, both in the design and operation of a CCD system, is necessary to ensure that the signal level relative to noise is adequate to allow capture of accurate image information.

  The short delay between the onset of the stimulus (0 s) and the peak of the GSR effect (around 2 s) matches the time course previously measured for other effects on GSR in healthy volunteers, such as the use of a click sound or a concurrent electrical and acoustic pulse to create a startle response (see Kucera et al., Kucera, P.   In the standard Hughson-Westlake hearing tests (Carhart and Jerger ), patient responses like a button press, raised hand, or verbal response are used to assess detection of brief test signals such as tones of varying pitch and level. Because of its reliance on voluntary responses, Hughson-Westlake audiometry is not suitable for patients who cannot .


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Effects of pixel noise and stimulus structure on visual detection performance by Helja Tuulikki Kukkonen Download PDF EPUB FB2

Visual target detection in displays consisting of multiple simple stimuli is a mainstay in visual science. or a signal among N image patches that otherwise consist of only pixel noise. the present study is still a far cry from studying the effect of stimulus structure on decision-making in natural scenes, for several reasons.

First, the Cited by: 8. Effects of pixel noise and stimulus structure on visual detection performance. (Thesis) ' ' Kukkonen HT Publisher: University of Aston in Birmingham [] Metadata Source: The British Library Type: Thesis. Abstract. No abstract provided.

Menu. Formats. Abstract. EThOS. Power analysis and subjects. An a priori power analysis (G*Power version ; Faul et al., ) indicated that a sample size of seven subjects per group would be sufficient to detect a significant effect on detection performance in the visual–noise experiment with a power of for an α level of These values are based on previous work investigating the effect of noise Cited by:   In the visual system, SCCs, also termed noise correlations, have traditionally been considered to be independent of the stimulus and hence have been thought to impede stimulus encoding.

Studies on stimulus-independent aspects of SCCs in the primary visual cortex (V1) sought to capture correlation patterns that were solely accounted for by Cited by: 6. Harper [D.W. Harper, Signal detection analysis of effect of white noise intensity on sensitivity to visual flicker, Percept. Mot.

Skills 48 () –] demonstrated that the visual flicker sensitivity was an inverted U-like function of the intensity of different levels of auditory noise from 50 to 90 dB (SPL), without concomitant changes in the response by: R.

Clough, A.I. Kirkland, in Advances in Imaging and Electron Physics, Integrating Detection. Integrating detection is the traditional mode of operation, with a long history in CCD devices based on passive pixel this mode, charge is stored in each pixel, accumulated for a defined exposure time and subsequently read out in one of several possible.

Measurements showing the effect of noise on motion detection is the pixel visual angle space-time plots and (C,F) still frames of the visual stimulus in two conditions of the experiment. Auditory suppression effect on visual discrimination (Exp.

1) We presented Gabor patches (1 × 1 deg, 4 cycle/deg, σ = deg, deg of phase angle) as target stimuli at the right side of the visual field (4 deg apart from the center) against a gray background ( cd/m 2) for 24 ms.A gray ring (2 deg) was also presented around the target and its luminance.

decision making; psychophysics; visual perception; Signal detection theory (SDT) proposes that sensitivity can be calculated by comparing true- and false-positive rates (1, 2).In a typical detection task, subjects are asked to judge whether a noisy stimulus does or does not contain a low-energy signal, allowing researchers to classify stimuli judged as containing the signal into.

Using attention (score ) and noise-effect (noise - no noise) as variables a Spearman rank-order correlation revealed positive correlation between attention and noise (r, N = 51, p; a medium effect size according to Cohen's d). The higher score on inattention the larger was the positive effect of noise and vice versa, attentive.

The present paper provides an overview of research concerning both acute and chronic effects of exposure to noise on children's cognitive performance. Experimental studies addressing the impact of acute exposure showed negative effects on speech perception and listening comprehension.

These effects are more pronounced in children as compared to adults. Cortical states associated with lower noise correlations, suppressed firing, and elevated gamma power before stimulus onset accurately predicted single trials of visual behavior.

During the stimulus, the absence of oscillations in L4, higher stimulus-evoked firing, and lower pairwise noise correlations predicted stimulus detection. Thermal noise can be reduced by increasing the load resistance, and dark-current noise can be reduced by decreasing the reverse saturation current through material improvement and junction structure optimization.

However, shot noise cannot be reduced because it is intrinsically associated with photo-detection process, which sets the fundamental. To create each stimulus pair, a normalised 8-bit monochrome (meaningful) signal image was randomly positioned within a pixel grid of random 2D noise of similar dimensions and mean luminance and with an amplitude spectra of 1/f (where f is the spatial frequency) to create pink-noise (as opposed to a a flat amplitude spectrum across spatial.

More generally, random “noise” can be introduced into any stimulus, including a visual display. Noise added to the stimulus can probe the computations underlying perception of the stimulus.

With power and precision, the noise, by restricting the information available, places fundamental constraints on attainable performance and processing. Estimated stimulus-detection thresholds fell within the contrast range spanned by the face stimuli (i.e., where the 95% confidence interval of objective stimulus-discrimination performance.

Auditory noise is a sound, a random variation in air pressure. More generally, random “noise” can be introduced into any stimulus, including a visual display. Noise added to the stimulus can probe the computations underlying perception of the stimulus.

With power and precision, the noise, by restricting the information available, places fundamental constraints on attainable performance. Therefore, stimulus detection in the visual periphery should benefit from large pupils. When large pupils are associated with a dark environment, as is typically the case in real life, this benefit should be even stronger, because the increased signal-to-noise ratio due to large pupils is accompanied by reduced light scatter due to the dark.

Noise is typically conceived of as being detrimental for cognitive performance; however, a recent computational model based on the concepts of stochastic resonance and dopamine related internal noise postulates that a moderate amount of auditive noise benefit individuals in hypodopaminergic states.

On the basis of this model we predicted that. Receptive-field structure. Receptive fields were mapped by correlating pixel values of the white-noise stimulus (white pixels, 1; black pixels, -1) with spikes that followed them at multiple time delays (Reid et al., ).These spatial and temporal maps are in units of spikes per second, and we will refer to them as the visual response.

To quantify the effects of noise on perception, data were fitted with the 36, a model where perceptual performance is limited by three different sources of inefficiency: external noise.Studies of visual detection of a signal superimposed on one of two identical backgrounds show performance degradation when the background has high contrast and is similar in spatial frequency and/or orientation to the signal.

To account for this finding, models include a contrast gain control mechanism that pools activity across spatial frequency, orientation and space to. Selective attention lends relevant sensory input priority access to higher-level brain areas and ultimately to behavior.

Recent studies have suggested that those neurons in visual areas that are activated by an attended stimulus engage in enhanced gamma-band (30–70 Hz) synchronization compared with neurons activated by a distracter.

Such precise .