Vision 2 Flashcards
What was studies in relation to colour vision?
Types of cones Trichromatic theory Opponent process theory Colour blindness Sensory integration
Light is a form of ___________ radiation
classified according to ___________ (how long
is one cycle)
electromagnetic
wavelength
Humans can perceive light waves in the range of about?
380-740nm (nanometers)
Light waves of incredibly high frequency are? (what colour)
Ultraviolet
Light waves of incredibly low frequency are? (what colour)
Infrared
What is preferential absorption?
Different photoreceptors in retina are sensitive to different wavelengths (eg. S-cones, M-cones and L-cones)
What do we perceive different wavelengths as?
colour
What determines the brightness of light?
The amplitude (height) of the waves
Colour perception is not inherent. What are the 3 steps to colour perception?
- Detection: light must be detected by our retina
- Discrimination: have to be able to tell different wavelengths apart
- Appearance: different colours go with different objects
What is meant by photopic?
light intensities that are bright enough to stimulate the cone receptors and saturate the rod receptors (E.g., sunlight, bright in door lighting)
What is meant by Scotopic?
light intensities that are bright enough to stimulate the rod receptors but too dim to stimulate the cone receptors (E.g., moonlight, dim indoor lighting)
What are the 4 different kinds of photoreceptors involved in discrimination?
1 rod type
3 cone types
What are the 3 different types of cone receptors and what are they sensitive to?
S-cones: short wavelengths (420 nm)
M-cones: medium wavelengths (535nm)
L-cones: long wavelengths (565 nm)
What is the problem of univariance?
For any single photoreceptor, there’s an infinite pairing of wavelengths that produce the same response rate
What is the Trichromatic theory?
Colour perception as the result of the pattern of activation from all three kinds of cones
Why do we see one colour, not a bunch of colours all jumbled together?
because we are restricted by our trichromatic visual system
What are two wavelengths that are the same in two different colour combinations?
A single wavelength of ‘yellow’ light
AND
A mixture of ‘red’ and ‘green’ lights
What are Metamers?
Any pair of stimuli that are perceived of as identical
even though they are physically different
What are two ways you can mix colours?
Additive colour mixture = the mixing of lights
Subtractive colour mixture = the mixing of pigments/ paints
What phenomena can’t be explained by the Trichromatic theory?
Afterimages
What combinations of colour can we see?
Greeny-yellow
Bluish-green
Yellowy-red (orange)
What combinations of colour can’t we see?
Greeny-red
Yellowy-blue
Whitish-black
What does the Opponent process theory of colour suggest?
That colour perception is controlled by the activity of two opponent systems; a blue-yellow mechanism and a red-green mechanism
What is the difference between red and green when examining their opponent neurons?
RED: positive (or excitatory) response
GREEN: negative (or inhibitory) response
Where are Cone opponent cells are found?
In the retina, LGN and V1
What is Deuteranope?
Colourblindness where a person has no M-cones and they can’t see green
What are the 3 types of colourblindness?
deuteranope
Protanopia
Tritanopia
What is Protanopia?
Colourblindness where a person has no L-cones and they can’t see red
What is Tritanopia?
Colourblindness where a person has no S-cones and they can’t see blue
What does Sensory integration suggest?
We rarely experience each of the individual sense in isolation because some brain regions combine information from different sensory modes (e.g., the superior colliculus, orbitofrontal cortex, thalamus)
Combining our senses may give us the 2 survival advantages of?
Allowing us to generate an internal coherent internal representation of the world
Increased accuracy and reliability of experience
What is Synaesthesia?
experiencing reliable sensory associations between apparently unrelated phenomena (eg. colours that elicit sound sensations)
What is suggested to be a cause of synaesthesia?
Cross-modal connections between normally separate brain areas produces brain cross activation (may be genetic)
What is 1 type of Screening test used to see if you have synaesthesia?
Ramachandran & Hubbarb (2s & 5s grid)
