title: Luminance and color inputs to mid-level and high-level vision.
abstract: We investigated the interdependence of activity within the luminance (L + M) and opponent chromatic (L - M and S - [L + M]) postreceptoral mechanisms in mid-level and high-level vision. Mid-level processes extract contours and perform figure-background organization whereas high-level processes depend on additional semantic input, such as object knowledge. We collected mid-level (good/poor continuation) and high-level (object/nonobject) two-alternative forced-choice discrimination threshold data over a range of conditions that isolate mechanisms or simultaneously stimulate them. The L - M mechanism drove discrimination in the presence of very low luminance inputs. Contrast-dependent interactions between the luminance and L - M as well as combined L - M and S - (L + M) inputs were also found, but S - (L + M) signals, on their own, did not interact with luminance. Mean mid-level and high-level thresholds were related, with luminance providing inputs capable of sustaining performance over a broader, linearly corresponding range of contrasts when compared to L - M signals. The observed interactions are likely to be driven by L - M signals and relatively low luminance signals (approximately 0.05-0.09 L + M contrast) facilitating each other. The results are consistent with previous findings on low-level interactions between chromatic and luminance signals and demonstrate that functional interdependence between the geniculate mechanisms extends to the highest stages of the visual hierarchy.
authors: School of Psychology, University of Aberdeen, Aberdeen, UK.
authors: Ben J
authors: BJ
authors: Jennings
authors: Jasna
authors: J
authors: Martinovic
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D003116:Color; D003118:Color Perception / Q000502:physiology*; D003119:Color Perception Tests / Q000379:methods; D004192:Discrimination, Psychological / Q000502:physiology*; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008027:Light; D010775:Photic Stimulation / Q000379:methods; D014795:Visual Pathways / Q000502:physiology*
keywords: color; good continuation; luminance; object classification; perceptual organization; postreceptoral mechanisms; visual pathways