• vendredi 01 juillet 2005 : ESIL
  Les informations sont en anglais (et les transparents sont en anglais également) mais la conférence sera présentée en français.
  
  
  • 10h00 : COLOR VISION: Investigating Higher Order Color Mechanisms - Gloria MENEGAZ
    
    Résumé :
    The processing of color information is of prime importance for the perception of the environment and the interpretation of its semantic. Though, the spectral properties of chromatic detection mechanisms are still mostly unknown. Color vision interacts strongly with other vision mechanisms like those subserving pattern sensitivity which makes the definition of models for color vision a highly complex task. Color "appearance" depends on many factors, both physiological and contextual. Among these are the number and the distribution of the photoreceptors in the retina, the illumination conditions and the presence of surrounding colors (simultaneous contrast). Many different phenomena need to be jointly modeled for a complete representation of color appearance when considering color spatial distributions, like textures and, more in general, natural scenes. After a brief overview on the basis of color vision, this seminar will illustrate a psycho-physical experiment aiming at investigating the post-receptoral mechanisms for color perception. Contrast detection thresholds were measured for a signal with a Gaussian spatial profile, modulated in the equiluminant plane in the presence of spatial, chromatic noise. The noise was distributed within a sector in the equiluminant plane, centered on the signal direction. Results showed that contrast thresholds were unaffected by the width of the noise sector, as previously found for temporally modulated stimuli, which is consistent with the existence of spectrally broadband linear detection mechanisms tuned to the signal color direction and supports the hypothesis of higher-order color mechanisms with sensitivities tuned to intermediate directions in the color space.