| Among our sensory modalities the visual modality is the one providing the highest information load. We live in an extremely rich visual environment; in general, one has to deal with constantly moving colored surface patches during visual information processing. In the present thesis I describe our work done on color vision, and visual motion processing.;We used computer-based psychophysics to test color vision in glaucoma and Best's vitelliform macular dystrophy. We found that color vision deficiencies are present in all cone pathways in both diseases despite the common views that associate glaucoma with selective blue-yellow deficits, and Best disease with selective red-green deficits. We also found that color vision deficits correlate well with standard clinical parameters used for staging in both pathologies.;We used psychophysics and/or functional magnetic resonance imaging (fMRI) to study center-surround interactions in surface integration, the interference between different observed motion types, and the effect of learning on surface segmentation.;By using psychophysics to study how moving surfaces are integrated we found strong surround influences on central ambiguous percepts. This effect depended on the inherent integration/segmentation bias of the surrounds, the presence/absence of local cues providing disambiguation, and the presence/absence of global context interfering with selected elements of the central moving surfaces.;We showed using fMRI that the interaction of real and apparent motion may lead to additive adaptation without saturation of hMT+ responses, while the interaction of motion aftereffects and apparent motion reflects interference. Moreover, neural substrates of illusory motion aftereffects can be identified when selective attention is directed to concomitant non-motion features and are masked by concurrent apparent/real motion tasks.;We found that learning results in increased detection thresholds and decreased fMRI responses for task-irrelevant motion direction compared to the task-relevant motion direction throughout the visual cortex. |
