mech of colour vision Flashcards
what is trichromatic theory
this is the idea that we have three hues, red, blue and green and the other hues are simple just a combination of these three primaries.
According to the trichromatic theory of colour vision, all colours in the spectrum can be produced by combining red, green, and blue. The three types of cones are each responsive to one of the colours.
what is the idea of colour-matching
that by varying the intensities of these three primaries, you are able to generate different colours. such that any colour can be obtained by adjusting the intensities of these three spectrums of light (blue, green, and red). If two physically different specras elicit the same cone signal, then the subjective colour would be the same due to similar intensities of light wavelength being reflected.
what are opponent colours and provide the four unique hues+ what is colour opponent theory
Opponent colours are at the opposite end of the spectra and come in pairs. green and red. blue and yellow. such that no hue can be yellowy blue or greeny red.
According to this theory, colour is processed in opponent pairs: black-white, yellow-blue, and green-red. The basic idea is that some cells of the visual system are excited by one of the opponent colours and inhibited by the other. So, a cell that was excited by wavelengths associated with green would be inhibited by wavelengths associated with red, and vice versa.
what is the colour after illusion
There will be neural mechanisms that signal green that are activated when viewing a green-colored object, and the same is true for all unique hues. But in this case, if we look at a greeny environment, such that when you switch to staring at a bright white (this stimulation is broadband), it will stimulate the green and red equally, hence why you would see it as white, but since the green is adapted, you will activate the red neural mechanism and see the white as red.
what is the opponent processing theory for chromatic channels and luminance channels?
chromatic channels: L-M = red signal greater, M-L =green signal greater, S-(L+M)+ = yellow signal greater, and S+(L+M)- = blue signal greater.
luminance channels, which include the sum of L and M used for achromatic signalling (black,white, or grey), sum up the input of L+M cones, which is used as a signal for luminance.
what receptive field diagram would signal best for achromatic and chromatic colors
For achromatic, it is best to have a contrasting receptive field for a better signalling response. But for chromatic colours, it is best for the entire receptive field to be stimulated by a signal wavelength for a better signal response, with a spatial period thats double the receptive field
what happens with a receptive field of l cones in the center and m cones in the surround, that is being stimulated by 480nm of light.
the L cone will respond less, i.e., with greater inhibition, and the M cones will respond greatly, such that there is less inhibition and more excitation, thus the net signal will be inhibition.
what is the color opponency circuitry
The koniocellular pathway involves yellow vs blue signalling which is connected to small bistratified ganglion cells that go to the layers in between the p and m LGN layers.
the parvocellular pathway involves red vs green signalling which is connected to midget ganglion cells that go to layers 3-6 of the LGN then higher centres for processing.
describe colour constancy in terms of the illuminant spectrum , ssr, and the overall reflected spectrum
whilst the ssr is the same ie the same colour, if the illumination differs ie indoor vs outdoor lighting, the overall reflected spectrum will be different as the ssr will seem to be distorted due to illumination, so it should be perceived different however the perceived colour will be the same as or brain can ignore the difference in illumination
what are the implications of colour constancy
-If the real-world property of colour is SSR, then the job of the visual
system may be to estimate real SSR
-For a given object, wavelength composition of light reaching the eye (and
therefore relative cone responses) will change if wavelength composition of
illuminant changes.However, perception of object colour appearance does not normally change.this suggets that the brian has been adapted to block or attentuate changes in luminace/light source to provde an estimation of the real wavelength composition of an object being refelcted off its surface into the eye.
what is simultaneous colour contrast?
when the colour of an object is the same but the contrasting surroundings make it appear different, either lighter or darker in colour, the overall colour appearance will be different even though they have the same wavelength
differentiate between color constancy and simultaneous color contrast
- Colour constancy shows that wavelength can change while colour appearance remains constant
- Simultaneous colour contrast shows that colour appearance can change even though wavelength
remains constant
