The world around us contains a variety of visual information, both first-order (luminance-defined) and second-order (defined by characteristics other than luminance). Previous studies suggest that the human visual cortex employs distinct mechanisms for segregating regions whose borders are defined by modulations of first- and second-order properties. This study uses a new approach of human psychophysics and fMRI experiments to explore the brain responses to both first-order and second-order (orientation, spatial frequency and contrast) texture borders. The results reveal differential activation among these modulations both in known retinotopic areas and in higher occipital/parietal regions. Orientation modulated textures elicit significantly different responses compared to modulations of other properties; whereas spatial frequency and contrast modulated textures produce similar responses. These findings suggest that higher visual cortical areas are heavily involved in texture processing, with a functional dissociation between segregating textures with modulations of (a) orientation, (b) spatial frequency or contrast and (c) luminance.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.82621 |
| Date | January 2004 |
| Creators | Mortin, Catherine Leanne |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Engineering (Department of Biomedical Engineering) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002198600, proquestno: AAIMR12635, Theses scanned by UMI/ProQuest. |
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