Call number: LD2668 .T4 1959 P37

Healthy ageing in the absence of neurodegenerative diseases is accompanied by a variety of perceptual and cognitive changes, which can occur on various distinct but interacting levels. Much research has been devoted to understanding how basic cognitive functions such as working memory and attention change with age. However, only more recently has age-related changes on perceptual functions been investigated, thus less is understood. My thesis aimed to address this gap in the literature, by exploring age-related changes in visual perception, specifically changes related to visual temporal processing of natural and biological stimuli. Also investigated was the extent to which age-related changes in perceptual and cognitive functions affect each other. Chapter 2 investigated the time course of visual processing of natural scene categorisation in older adults. Younger, young-old and old-old adults performed a go/no-go task, in which they had to respond to images of animals whilst ignoring images of landscapes. The results showed that the temporal processing of complex scenes is impaired in healthy older adults and this deficit becomes more pronounced with increasing age. Chapter 3 assessed whether age-related decline in biological motion perception is mediated by impaired attentional abilities. Younger and older adults performed a series of tasks assessing biological motion perception and visual attention. The results indicated that age-related changes in biological motion perception are not driven by general attentional decline. Lastly, Chapter 4 explored whether age-related changes in biological motion and attention tasks can be explained by differences in the allocation of attention. Younger and older adults performed a conjunctive visual search, and two biological motion tasks, while their eye movements were being tracked. The results illustrated that differences in the allocation of attention cannot explain age-related differences found on biological motion perception and attention tasks. Overall, my findings provide substantial evidence to suggest that both visual perceptual and cognitive abilities change with healthy ageing. However, my results also indicate that certain aspects of these two functions remain relatively preserved in older adulthood.

Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. / Microfiche copy available in Archives and Barker. / Bibliography: p.101-102. / M.S.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph.D.)--York University, 2004. Graduate Programme in Biology. / Typescript. Includes bibliographical references (leaves 292-305). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ99265

Thesis (Ph. D.)--University of California, San Diego, and San Diego State University, 2004. / Vita. Includes bibliographical references.

Thesis (M.Sc.)--York University, 2008. Graduate Programme in Higher Education. / Typescript. Includes bibliographical references. 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:MR45975

Thesis (Ph. D.)--University of California, San Diego and San Diego State University, 2003. / Vita. Includes bibliographical references (leaves 182-208).

Motion coding in the brain undoubtedly reflects the statistics of retinal image motion occurring in the natural environment. Measuring the statistics of motion in natural scenes is an important tool for building our understanding of how the brain works. Unfortunately, there are statistics that are either impossible or prohibitively difficult to measure. For this reason, it is useful to measure scene statistics in artificial movies derived from simulated environments. This is a novel and important methodological approach that allows us to ask questions about optimal coding that are impossible otherwise. This dissertation describes a course of research that develops this research methodology, the simulated scene statistical approach. This dissertation applied the artificial scene statistical approach to understanding the visual statistics of motion during navigation through forest environments. An environmental model of forest scenes was developed based on previously measured range and surface texture statistics. Spatiotemporal power spectra were measured in both simulated and natural scenes for the task of first person motion through a forest environment. These image statistics measurements helped validate the environmental model. Next, the environmental model was used to simulate across-domain statistics to study the ideal aperture size of motion sensors. It was found that across a variety of different scene conditions, the optimal aperture size of motion sensors increases with the speed to which the sensor is tuned. This is an important constraint for understanding both how the brain encodes motion as well as for designing computer motion detectors. This theoretical research inspired a psychophysical experiment estimating the receptive-field size of human foveal motion discrimination. It was found that for narrow-band stimuli the ideal aperture size increases with spatial frequency, but is unchanging with respect to velocity or temporal frequency. This dissertation shows an approach to the study of vision that has applications in psychophysics, neuroscience and computer vision. The emphasis on accurate and validated environmental models for simulating scene statistics can help improve our understanding of the structure and function of the human visual system and also help us build more accurate and robust computer vision systems. / text

The detection of visual stimuli involves neurons which are selectively responsive to components of a visual scene. In the early stages of visual processing, it is commonly accepted that neurons respond to the changes in luminance associated with objects and object boundaries. However, recent experiments have demonstrated that some neurons can also respond to features which are not defined by luminance variations. These features are termed "second-order" because they require more complex processing, and neurons which respond to second-order features are necessarily nonlinear. / In this thesis, I undertook a three dimensional physiological characterization (i.e. tuning of orientation, spatial frequency and temporal frequency) of such nonlinear neurons in order to shed light on their processing capabilities. In particular we sought to address the following issues: (1) whether the temporal and spatial properties underlying second-order motion are similar to those underlying luminance based ("first-order") motion; (2) whether these properties remain constant using different types of second-order stimuli, suggesting that neurons' responses are invariant to the physical attributes comprising the stimulus; and (3) whether second-order processing is a cortical mechanism or can occur at an earlier stage of the visual system (e.g. in the lateral geniculate nucleus). Taken together these results have a dual function; they provide insight into the complex cellular processing of higher order features, and they provide a general framework for the generation of second-order models.