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Thesis (Ph. D.)--Cornell University, January, 2007. / Vita. Includes bibliographical references (leaves 214-229).

Thesis (Ph. D. in Physics)--Vanderbilt University, Dec. 2007. / Title from title screen. Includes bibliographical references.

How does the visual cortex represent and process color? Experimental evidence from macaque monkey suggests that cells selective for color are organized into small, spatially separated blobs in V1, and stripes in V2. This organization is strikingly different from that of orientation and ocular dominance maps, which consist of large, spatially contiguous patterns. In this dissertation, a self-organizing model of the early visual cortex is constructed using natural color image input. The modeled V1 develops realistic color-selective receptive fields, ocular dominance stripes, orientation maps, and color-selective regions, while the modeled V2 also creates realistic colorselective and orientation-selective neurons. V1 color-selective regions are generally located in the center of ocular dominance stripes as they are in biological maps; the model predicts that color-selective regions become more widespread in both cortical regions when the amount of color in the training images is increased. The model also predicts that in V1 there are three types of color-selective regions (red-selective, greenselective, and blue-selective), and that a unique cortical activation pattern exists for each of the HSV colors. In both V1 and V2, when regions of different color-selectivity are located nearby, bands of color form with gradually changing color preferences. The model also develops lateral connections between cells that are selective for similar orientations, matching previous experimental results, and predicts that cells selective for color primarily connect to other cells with similar chromatic preferences. Thus the model replicates the known data on the organization of color preferences in V1 and V2, provides a detailed explanation for how this structure develops and functions, and leads to concrete predictions to test in future experiments.

No description available.

The detection threshold of a luminance-defined Gabor is improved by two high contrast, aligned flanking Gabors, an effect termed collinear facilitation. However, the neural basis of collinear facilitation is not well understood. This thesis focuses on a number of issues in collinear facilitation to better our understanding of its neural basis. (1) Cortical sites: the cortical site of collinear facilitation was investigated, and results showed that collinear facilitation is a purely monocular phenomenon. (2) Temporal properties: Collinear facilitation has fast dynamics for initiation and once collinear facilitation occurs it either decays slowly or is associated with a sustained detection. (3) Selectivity to other types of stimuli: chromatic stimuli (which isolated the S-cone opponent and the L/M cone opponent mechanisms) and 2nd order stimuli (a 2D white noise or ID noise multiplied with a Gabor envelope) were used and the results showed that collinear facilitation occurs in chromatic processing, and that some 2nd order stimuli also exhibit collinear facilitation. However, there was no interaction between luminance and chromatic systems nor between 1st and 2nd order mechanisms, suggesting independent processing streams for collinear facilitation. All of these results supported the conclusion that collinear facilitation is not a general property of cortical neurons in V1 since most V1 neurons are binocular, sensitive to both chromatic and achromatic stimuli and sensitive to both 1 st and 2nd order stimuli. Furthermore, the temporal properties of collinear facilitation suggest complex dynamic interactions, not simply explained by the passive propagation of long-range recurrent intra-cortical connections between flanks and target.

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Thesis (M.S. in Applied Physics)--Naval Postgraduate School, December 2008. / Thesis Advisor(s): Karunasiri, Gamani ; Tummala, Murali. "December 2008." Description based on title screen as viewed on January 29, 2009. Includes bibliographical references (p. 69-71). Also available in print.

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [58]-64).

Thesis (Ph.D.). / Written for the Dept. of Physiology. Title from title page of PDF (viewed 2009/06/10). Includes bibliographical references.