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Visual physiology of the Antarctic amphipod Abyssorchomene plebs
Title
Visual physiology of the Antarctic amphipod Abyssorchomene plebs.
Creator
Cohen, Jonathan H., Frank, Tamara M., Harbor Branch Oceanographic Institute
Date Issued
2006
PURL
http://purl.flvc.org/FCLA/DT/3171579
Subject Headings
Amphipoda, Physiological optics, Gammaridae, Aquatic biodiversity, Marine biology
Format
Document (PDF)
effect of spatial attention on pupil dynamics
Title
The effect of spatial attention on pupil dynamics.
Creator
Daniels, Lori B., Charles E. Schmidt College of Science, Department of Psychology
Abstract/Description
Although it is well known that the pupil responds dynamically to changes in ambient light levels, the results from this dissertation show for the first time that the pupil also responds dynamically to changes in spatially distributed attention. Using a variety of orientating tasks, subjects alternated between focusing attention on a central stimulus and spreading attention over a larger area. Fourier analysis of the fluctuating pupil diameter indicated that: 1) pupil diameter changed at the...
Show moreAlthough it is well known that the pupil responds dynamically to changes in ambient light levels, the results from this dissertation show for the first time that the pupil also responds dynamically to changes in spatially distributed attention. Using a variety of orientating tasks, subjects alternated between focusing attention on a central stimulus and spreading attention over a larger area. Fourier analysis of the fluctuating pupil diameter indicated that: 1) pupil diameter changed at the rate of attention variation, dilating with broadly spread attention and contracting with narrowly focused attention, and 2) pupillary differences required changes in attentional spread; there were no differences in pupil diameter between sustained broad and sustained spread attention. Given that broadly spread attention increases the relative activation of large receptive fields and narrowly focused attention increases the relative activation of small receptive fields (Balz & Hock, 1997), the results of this study indicate that these attentional effects on receptive field activation can be mediated by changes in pupil diameter. That is, under broad attention, the corresponding pupillary dilation observed would increase spherical aberration, blurring the image thereby reducing high spatial frequency information and decreasing the activation of relatively small cortical receptive fields compared to relatively large receptive fields. This increased perception of low spatial frequencies would be beneficial in cases where attention is spread over a large area. Alternatively, under narrow attention the resulting pupillary constriction reduces spherical aberration sharpening the image and preserving high spatial frequency information resulting in a relatively increased response of small receptive fields.
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Date Issued
2010
PURL
http://purl.flvc.org/FAU/1870692
Subject Headings
Visual perception, Eye, Physiology, Optics, Adaptive, Visual pathways
Format
Document (PDF)
The Effects of Dichoptic and Isoluminant-Chromatic Stimuli on the Perception of Object and Objectless Motion
Title
The Effects of Dichoptic and Isoluminant-Chromatic Stimuli on the Perception of Object and Objectless Motion.
Creator
Seifert, Matthew S., Hong, Sang Wook, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Psychology
Abstract/Description
Visual motion can be conveyed by a variety of information sources in the environment, and those types of information may be detected at various levels by different motion-perceiving mechanisms in the visual system. High-level visual information has been demonstrated to have 3rd order, or salience-based properties (Lu & Sperling, 1995). The perceptual system they describe that computes motion from these types of information shares several characteristics with Hock and colleagues' counterchange...
Show moreVisual motion can be conveyed by a variety of information sources in the environment, and those types of information may be detected at various levels by different motion-perceiving mechanisms in the visual system. High-level visual information has been demonstrated to have 3rd order, or salience-based properties (Lu & Sperling, 1995). The perceptual system they describe that computes motion from these types of information shares several characteristics with Hock and colleagues' counterchange detection system, notably flexibility with respect to types of input from which motion can be computed, which comes at the cost of diminished processing speed. The mechanism of counterchange detection is well suited to processing visual features often present in environmental scenes, e.g., objects and surfaces, and may be a mechanism of 3rd order motion. Consistent with reported properties of 3rd order motion, the current experiments tested count erchange-, luminance-, and color-based motion stimuli with 3 objectives: to identify whether the 3 systems framework generalizes beyond the stimulus type with which it was defined, to test whether counterchange shares similarities with the 3rd order system with respect to dichoptic integration, and perception of isoluminant color-based motion, and to test subjectively objectless sources of motion-defining information (spreading luminance and hue) to see if they display properties of the 1st order system derived from sine wave gratings. Results indicate that counterchange-based stimuli displayed predicted properties of dichoptic integration, and perception at isoluminance, but putative 1st order (spreading) stimuli also displayed these properties. This may suggest that object-like surfaces, even when not directly the source of motion information, can contribute to computation of motion. Further, these results highlight the difficulty of generalizing from one theoretical framework to another, and specifically, of psychophysically testing high-level information while isolating contributions from low level information upon which high level visual stimuli are built.
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Date Issued
2015
PURL
http://purl.flvc.org/fau/fd/FA00004545, http://purl.flvc.org/fau/fd/FA00004545
Subject Headings
Movement, Psychology of, Perceptual motor processes, Physiological optics, Space and time, Visual perception
Format
Document (PDF)