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You searched for subject:(Metacontrast masking). Showing records 1 – 2 of 2 total matches.

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York University

1. Daar, Marwan Abdallah. Masking in Central Visual Field Under a Variety of Temporal and Spatial Configurations.

Degree: PhD, Psychology(Functional Area: Brain, Behaviour & Cognitive Science, 2018, York University

For over a century, visual maskingwhere one stimulus reduces the visibility of another stimulushas been used as a powerful tool to explore the visual system. Two major forms have emerged: backward masking and common onset masking. These two forms, which are characterized by the temporal properties of the stimuli, are often used to probe different underlying masking mechanisms, and the two forms typically employ a unique set of spatial characteristics of the mask. This clustering of stimulus properties makes it challenging to assess the effect of each stimulus property by itself. This dissertation describes an attempt to isolate the effects of these properties. In the first set of experiments various masking schedules are tested, including backward, common onset, and variations between, while keeping the spatial properties of the stimuli constant. In the second set of experiments four-dot common onset masking is explored in detail, and in one of the experiments, a single masking schedule is tested while varying the spatial properties of the mask. Across all experiments, target stimuli are presented foveally. A computational model is developed to account for data across both sets of experiments. Three important findings emerge. First, masking can be successfully obtained in central visual field using a variety of stimulus properties. Second, there is compelling evidence that persisting traces of these stimuli play an important role in masking. Third, there is strong evidence of both spatially local and global masking effects. Advisors/Committee Members: Wilson, Hugh R. (advisor).

Subjects/Keywords: Neurosciences; Visual masking; Object substitution masking; OSM; Metacontrast; Backward masking; Computational neuroscience; Psychophysics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Daar, M. A. (2018). Masking in Central Visual Field Under a Variety of Temporal and Spatial Configurations. (Doctoral Dissertation). York University. Retrieved from http://hdl.handle.net/10315/34358

Chicago Manual of Style (16th Edition):

Daar, Marwan Abdallah. “Masking in Central Visual Field Under a Variety of Temporal and Spatial Configurations.” 2018. Doctoral Dissertation, York University. Accessed December 04, 2020. http://hdl.handle.net/10315/34358.

MLA Handbook (7th Edition):

Daar, Marwan Abdallah. “Masking in Central Visual Field Under a Variety of Temporal and Spatial Configurations.” 2018. Web. 04 Dec 2020.

Vancouver:

Daar MA. Masking in Central Visual Field Under a Variety of Temporal and Spatial Configurations. [Internet] [Doctoral dissertation]. York University; 2018. [cited 2020 Dec 04]. Available from: http://hdl.handle.net/10315/34358.

Council of Science Editors:

Daar MA. Masking in Central Visual Field Under a Variety of Temporal and Spatial Configurations. [Doctoral Dissertation]. York University; 2018. Available from: http://hdl.handle.net/10315/34358


University of Houston

2. -1178-347X. A Statistical Approach to Visual Masking and Spatial Attention.

Degree: PhD, Electrical Engineering, University of Houston

A stimulus (mask) reduces the visibility of another stimulus (target) when they are presented in close spatio-temporal vicinity of each other, a phenomenon called visual masking. Visual masking has been extensively studied to understand the dynamics of information processing in the visual system. Visual spatial attention is also known to modulate information processing and transfer within the visual system. Since both processes control the transfer of information from sensory memory to visual short-term memory (VSTM), a natural question is whether these processes interact or operate independently. Here, we modeled visual masking by using a statistical framework, and used this theoretical framework along with psychophysical experiments to determine whether and how masking and attention interact. In a psychophysical experiment, observers were asked to report the orientation of a target bar under three different masking paradigms. The distribution of response errors was modeled by using statistical mixture-models. Our results show that in all three types of masking, the reduction of a target’s signal-to-noise ratio (SNR) was the primary process whereby masking occurred. We interpret these findings as the mask reducing the target’s SNR (i) by suppressing or interrupting the signal of the target in para-/meta- contrast, (ii) by increasing noise in pattern masking by noise, and (iii) a combination of the two in pattern masking by structure. Recent evidence suggests that the studies that reported interactions between masking and attention suffered from ceiling and/or floor effects. We investigated interactions between metacontrast masking and attention by using an experimental design in which saturation effects were avoided. In these experiments, attention was controlled either by set-size or by spatial pre-cues. We examined attention-masking interactions based on two types of dependent-variables: (i) the mean absolute response errors and (ii) the distribution of signed response errors. Our results show that both the voluntary (endogenous) and reflexive (exogenous) mechanisms of attention affect observers’ performance without interacting with masking. Statistical modeling of response errors suggests that attention and metacontrast masking exert their effects mainly through independent modulations of the guessing component of the mixture model. Taken together, our results suggest that visual masking and attention operate independently. Advisors/Committee Members: Ogmen, Haluk (advisor), Breitmeyer, Bruno G. (committee member), Jansen, Ben H. (committee member), Sheth, Bhavin R. (committee member), Zouridakis, George (committee member).

Subjects/Keywords: Visual masking; Spatial attention; Bayesian models; Metacontrast masking; Paracontrast masking; Pattern masking by noise; Pattern masking by structure

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

-1178-347X. (n.d.). A Statistical Approach to Visual Masking and Spatial Attention. (Doctoral Dissertation). University of Houston. Retrieved from http://hdl.handle.net/10657/3350

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete
No year of publication.

Chicago Manual of Style (16th Edition):

-1178-347X. “A Statistical Approach to Visual Masking and Spatial Attention.” Doctoral Dissertation, University of Houston. Accessed December 04, 2020. http://hdl.handle.net/10657/3350.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete
No year of publication.

MLA Handbook (7th Edition):

-1178-347X. “A Statistical Approach to Visual Masking and Spatial Attention.” Web. 04 Dec 2020.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete
No year of publication.

Vancouver:

-1178-347X. A Statistical Approach to Visual Masking and Spatial Attention. [Internet] [Doctoral dissertation]. University of Houston; [cited 2020 Dec 04]. Available from: http://hdl.handle.net/10657/3350.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete
No year of publication.

Council of Science Editors:

-1178-347X. A Statistical Approach to Visual Masking and Spatial Attention. [Doctoral Dissertation]. University of Houston; Available from: http://hdl.handle.net/10657/3350

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete
No year of publication.

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