Stereopsis is a par excellence demonstration of the computational power that neural systems can encapsulate. How is the brain capable of swiftly transforming a stream of binocular two-dimensional signals into a cohesive three-dimensional percept? Many brain regions have been implicated in stereoscopic processing, but their roles remain poorly understood. This dissertation focuses on the contributions of primary and dorsomedial visual cortex. Using convolutional neural networks, we found that disparity encoding in primary visual cortex can be explained by shallow, feed-forward networks optimized to extract absolute depth from naturalistic images. These networks develop physiologically plausible receptive fields, and predict neural responses to highly unnatural stimuli commonly used in the laboratory. They do not necessarily relate to our experience of depth, but seem to act as a bottleneck for depth perception. Conversely, neural activity in downstream specialized areas is likely to be a more faithful correlate of depth perception. Using ultra-high field functional magnetic resonance imaging in humans, we revealed systematic and reproducible cortical organization for stereoscopic depth in dorsal visual areas V3A and V3B/KO. Within these regions, depth selectivity was inversely related to depth magnitude — a key characteristic of stereoscopic perception. Finally, we report evidence for a differential contribution of cortical layers in stereoscopic depth perception.

The Winnipeg River Drainage Basin (WRDB), located in the boreal forest region of Canada, is a pivotal region of focus for the assessment of water availability to determine susceptibility to drought in the past. To date, there have been relatively few paleolimnological studies focusing on how lake levels have changed in the past and whether these changes have been synchronous in the WRDB. This study investigates temporal patterns in effective moisture from Little Raleigh Lake over the last two millennia. Analyses are based on diatoms from two near-shore sediment cores from different locations and water depth in Little Raleigh Lake. Changes in diatom assemblages are used to reconstruct quantitative estimates of effective moisture in the past through the calibration of a diatom-inferred depth model developed from diatom assemblages in surficial sediments along a depth transect in Little Raleigh Lake. Declines of ~1-3m occurred during the late Holocene, with prolonged periods of aridity consistent with the timing of the Medieval Climate Anamoly (~950-1250AD) and the Little Ice Age (~1650-1750AD). The nearshore core retrieved closer to the present-day ecotone between the benthic and planktonic diatom assemblages was more sensitive to tracking water level changes in the lake than the deeper core. Conditions during the last two millennia can be used for the assessment of water availability in the past, and may offer insight on future conditions under increasing temperatures. / Thesis (Master, Biology) -- Queen's University, 2011-07-29 17:09:49.155

Visual images from the two eyes are transmitted to the brain. Because the eyes are horizontally separated, there is a horizontal disparity between the two images. The amount of disparity between the images of a given point depends on the distance of that point from the viewer's point of fixation. A natural visual environment contains surfaces at many different depths. Therefore, the brain must process a spatial distribution of disparities. How are these disparities spatially put together? Brief (about 200 msec) static Cyclopean random-dot stereograms were used as stimuli for vergence and depth discrimination to answer this question. The results indicated a large averaging region for vergence, and a smaller pooling region for depth discrimination. Vergence responded to the mean disparity of two transparent planes. When a disparate target was present in a fixation plane surround, vergence improved as target size was increased, with a saturation at 3-6 degrees. Depth discrimination thresholds improved with target size, reaching a minimum at 1-3 degrees, but increased for larger targets. Depth discrimination showed a dependence on the extent of a disparity pedestal surrounding the target, consistent with vergence facilitation. Vergence might, therefore, implement a coarse-to-fine reduction in binocular matching noise. Interocular decorrelation can be considered as multiple chance matches at different disparities. The spatial pooling limits found for disparity were replicated when interocular decorrelation was discriminated. The disparity of the random dots also influenced the apparent horizontal. alignment of neighbouring monocular lines. This finding suggests that disparity averaging takes place at an early stage of visual processing. The following possible explanations were considered: 1) Disparities are detected in different spatial frequency channels (Marr and Poggio, 1979). 2) Second-order luminance patterns are matched between the two eyes using non-linear channels. 3) Secondary disparity filters process disparities extracted from linear filters.

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Thesis (M. S.)--Psychology, Georgia Institute of Technology, 2005. / Randall W. Engle, Ph.D., Committee Member ; Paul M. Corballis, Ph.D., Committee Chair ; Daniel H. Spieler, Ph.D., Committee Member. Includes bibliographical references.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 106-108). Also available via the Internet.

Thesis (Ph. D.)--Carleton University, 2001. / Includes bibliographical references (p. 119-125). Also available in electronic format on the Internet.

Thesis (Ph.D.)--York University, 2009. Graduate Programme in Psychology. / Typescript. Includes bibliographical references (leaves 181-198). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:NR51739

In light of the conflicting data regarding depth perception and the retardate, it was the purpose of this study to reinvestigate whether or not significant differences exist in depth perceptual abilities among mental retardates. A standard depth perception apparatus was utilized to test the groups of brain-injured, familial and idiopathic subjects.

The estranged relationship with landscape exhibited by contemporary cultures has been well documented by prominent theorists. Design professionals can begin to reconcile culture and landscape by proposing interventions in everyday landscapes which embrace uncertainty, acknowledge the temporal nature of phenomena, and introduce elements of ambiguity while simultaneously creating pleasing, functional environments. Such interventions encourage meaningful, imaginative experience, encourage multiple readings, and suggest renewed ways of dwelling in landscape. The methodology for this thesis is a two part examination of contemporary approaches to the production of space in significant cultural landscapes. Part one, a position paper, reviews relevant literature and outlines a position to guide design proposals. Part two tests the principals and theories developed in the position paper through proposals for interventions at two sites. The context for the design component is the Crooked Road Musical Heritage Trail. The Crooked Road is an ideal setting in which to explore the potential of interventions that seek to reconcile culture and landscape. It offers participants a framework for the experience of both regional landscape and culture in the form of traditional music rich in landscape themes. Proposals are developed for an abandoned homestead on Shooting Creek and the Floyd Country Store, both in Floyd County, Virginia, along the Crooked Road. The approach to intervention developed in these proposals is intended to guide the development of additional sites along the Crooked Road with the goals of enriching the landscape experience of participants, strengthening regional sense of place, and reconciling estranged relationships with landscape. / Master of Landscape Architecture