1 / 16

Understanding Color Vision: The Trichromatic and Opponent Process Theories Explained

This lecture explores the fundamental aspects of color vision, focusing on the Trichromatic Theory proposed by Young-Helmholtz, which includes the roles of three types of cone receptors (red, green, blue) and their differential sensitivity to light wavelengths. The lecture contrasts this with Hering's Opponent Process Theory, which introduces antagonistic color pairs. We also delve into concepts of perceptual color, negative after-images, and the Retinex Theory, emphasizing how context influences color perception. Learn how these theories relate to the structure and function of the visual system.

mackenzie-carrigy
Télécharger la présentation

Understanding Color Vision: The Trichromatic and Opponent Process Theories Explained

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Visual System:Color Vision Lecture 16

  2. The Trichromatic Theory • Young-Helmholtz (1802) • 3 types of color receptors • Cones • Differential sensitivity to light wavelengths • red (long) • green (medium) • blue (short) ~

  3. The Trichromatic Theory • Perceived color • overall pattern of stimulation • Like mixing paint • Negative After-image?

  4. The Trichromatic Theory? • What colors do you see? • How can you see colors that weren’t there? • Negative After-image • Does it fit Trichromatic Theory? ~

  5. Hering Opponent Process Theory • Competing theory • Center-Surround organization • BP, RGC, & LGN • Antagonistic for color • Red-Green • Blue-Yellow • Black-White

  6. Hering Opponent Process Theory • Center- surround antagonistic • Each color can be excitatory (+) or inhibitory (-) • 12 combinations total ~

  7. Which Theory? • Both are correct in retina • Photoreceptors: trichromatic • Higher levels: Opponent Process • BP, RGC, & LGN • More complex at cortical level • Retinex Theory ~

  8. Retinex Theory • Perception of visual stimulus • subjective • includes context & past experiences • color & brightness constancy • Color constancy • e.g., grass in sun vs. grass in shade • perceived as same color green • e.g., Rubic’s cube ~

  9. Lateral Geniculate Nucleus • 6 layers • dorsal  ventral • 6  1 • RFs center-surround • Input from each eye • monocular • 2, 3, 5 from the ipsilateral eye • parallel processing ~

  10. LGN: Parallel Processing • Parvocellular system • layers 3-6 • small RFs • info from cones • color & form • Magnocellular system • Large RFs • layers 1 & 2 • info from rods • form only, no color ~

  11. Color Processing:Primary Visual Cortex

  12. V1 Organization • 6 layers • Most input  Layer 4 • 1st binocular receptive fields • cells get input from both eyes • ocular dominance • Modular organization • Blob cells: color processing • Wavelength specific ~

  13. Modular V1 Organization L R L B L O B 2 & 3 4 LGN 5 & 6

  14. Blob cells & Color Perception • Same color perceived differently • Double Opponent Process Cells • Different from RGC & LGN • center-surround • Center: • red  excitation • green  inhibition • Surround: • red  inhibition • green  excitation ~

  15. Double-Opponent Process Blob Cells R-G+ R-G+ R+G- R+G-

  16. Higher Level Color Processing • V1  V2  V4 • V4 in medial occipital cortex • V4 damage • disrupts color constancy • achromatopsia • unilateral – 1 visual field • bilateral – no color perception ~

More Related