Color Vision and Perception Quiz

Visual System and Color Perception

• The lateral geniculate nucleus (LGN) and cortex differentiate cone responses and create cone-opponent cells.
• Three color opponent channels: L-cone (red), M-cone (green), and S-cone (blue).
• Color constancy requires the presence of surrounding colors and adequate illumination to maintain consistent color perception.
• Color is described as a non-physical property because it is a perceptual experience influenced by human perception rather than physical attributes of objects.
• Color vision begins with three types of cone receptors (S, M, L) that detect specific wavelengths of light.
• Color deficiency alters the experience of color, often resulting in the inability to distinguish certain colors.
• Differentiation of cone responses in the LGN and cortex leads to the creation of color-opponent cells.
• The percept of color without physical stimulation suggests that color perception is an interpretative mental process.
• The visible part of the electromagnetic spectrum ranges from approximately 380nm to 750nm.
• Differences in wavelength are interpreted as variations in color through the activation of specific cone photoreceptors.
• The human range of the electromagnetic spectrum is approximately 380nm to 750nm for light and color perception.
• Chronological order of color perception: Light detection, Neural signal processing, Color perception.
• Two lighting conditions relevant to color detection: Photopic (bright light) and Scotopic (dim light).
• Photopic lighting conditions stimulate cone receptors and saturate rod receptors.
• Scotopic lighting conditions are dim enough to stimulate rod receptors but not cone receptors.
• Mesopic lighting conditions stimulate cones without saturating rods, common in low light.
• Photopic conditions are typically found in sunlight and bright indoor lighting.
• Scotopic conditions are associated with moonlight and very dim indoor lighting.
• A well-lit room suggests the presence of photopic lighting conditions.
• Cones are primarily stimulated in photopic lighting conditions.
• Color vision relies on three types of cones, allowing for color detection.
• Three types of cone photoreceptors exist within photopic vision: S-cones (short), M-cones (medium), and L-cones (long).
• S-cones detect short wavelengths, while M-cones are sensitive to medium wavelengths.
• Referring to cones as "short," "medium," and "long" is more accurate than their color names (blue, green, red).
• Color discrimination refers to the ability to distinguish between different colors based on varying wavelengths.
• Univariance problem: A single photoreceptor cannot distinguish between different wavelengths from light intensity alone.
• Rod receptors are ineffective in distinguishing between low and high-frequency light sources in photopic conditions.
• Rod photoreceptors experience hyperpolarization in response to light, but the firing rate doesn’t effectively convey color differences.
• Rods are sensitive to scotopic light levels and contain the photopigment rhodopsin.
• Rods struggle to discern color differences, resulting in a monochromatic perception under scotopic conditions.
• Under scotopic conditions, the environment appears color-drained due to rod dominance.
• Under bright lighting, S-, M-, and L-cones remain active, differentiating various wavelengths.
• Under blue lighting, S-cones respond strongly, while M and L cone responses are minimal.
• Stimulation of all three cone types by the same stimulus under photopic conditions enables color perception.
• Color detection occurs primarily in the retina, where cones react to light.
• According to Trichromatic theory, color is defined by the output of three cone types.
• Perceptual experience of color is determined by the activation levels of the cone receptors.
• Spatially close red and green light activating L and M cone receptors creates a perception of yellow (color mixing).
• Metamers are distinct light sources that appear the same in color perception due to the combination of cone activation.
• The fundamental concept is that our color experience is a construct of perceptual processing rather than a direct representation of light.
• Disparate light sources can be perceived as the same color based on neural processing patterns.

LGN and Color Opponency

• LGN is responsible for creating and differentiating cone responses, leading to cone-opponent cells.
• On-off LGN cells have center-surround receptive fields that are responsive to wavelength lengths.
• The main function of cone-opponent cells in the LGN is to enhance contrast and differentiate colors.
• On-off LGN cells respond to increasing light in the center and decrease in the surround, while off-on cells do the opposite.
• Center-surround organization in the LGN contributes to color discrimination by varying response to different wavelengths.
• Cone-opponent cells compare and process input from multiple cone types to create more complex visual information.
• Off-on LGN cells exhibit increased firing when light dims in the center and brightens in the surround.
• Color discrimination in the visual system is determined by the balance of activation between different cone receptors.
• Assigning perceived colors to lights and surfaces helps navigate and interpret the visual world.
• RGB color space is defined by three primary colors (Red, Green, Blue) that can create a spectrum of colors.
• HSB color space components include Hue, Saturation, and Brightness, defining color representation.
• Color spaces are frameworks used to systematize color perception for various applications.
• The HSB color space defines Hue as the attribute representing the color type.
• Saturation in HSB refers to the intensity of color (vibrancy).
• Brightness in the HSB context denotes how light or dark a color appears.
• Photopic vision is compatible with color space implementations and the trichromatic theory.
• Opponency theory suggests color perception is based on three mechanisms that relate opposing colors.
• Opponent color combination example: Red vs. Green exhibits the principle of color opponency.
• Excitation of L-cone and inhibition of M-cone in LGN produces specific color responses.
• Opponency in color arises from the interaction between different mechanisms processing light wavelengths.
• Illegal color combinations, such as bluish-yellow, do not appear in human perception, aligning with Hering's color theory.