Vision and Colour Perception Flashcards
The Eye
Pupil: Light enters eye
Iris: Adjustable aperture, constricts in high light to make pupil smaller
Cornea and lens: Focuses light on retina
Accommodation: Ciliary muscles change shape of lens to bring objects into focus and different distances
Retina and Photoreceptors
Photoreceptors: Cells with light sensitive photopigments in outer segments
Rods: contain rhodopsin, respond in dim light, none in fovea
Cones: three types with photopigments most sensitive to different wavelengths ( long, medium, short) daytime vision.
Lateral Geniculate Nucleus
Magnocellular cells: Movement and flicker
Parvocellular cells: Colour and detail
Koniocellular cells: Blue- yellow…
How much of the cortex is dedicated to vision?
more than 50% - the visual cortex
Visual system
Eye - Edge detection & Contrast detection
Thalamus: Motion perception
Cortex: Orientation detection & Face detection
Cone Photoreceptors
Human Trichromacy: three cone types, Short Medium Long
Dichromatic - Trichromatic = blue and yellow split into red and green
Genetic Colour vision deficiency
Dichromats:
- Protanopia - lack red cone L
- Deuteranopia - lack green cone m
- Tritanopia lack blue cone s
Anomolus trichromats
- Deuternomoly . M shift to L
- Protanomoly ( L shifted to M).
Cone Opponency
cherry- teal
lime- violet
Achromatic
Cerebral Achromatopsia
damage to small cortical region, loss of colour perception
Humans with lesions in the extrastriate visual cortex
Top Down effects of colour perception
Memory of a typical colour of objects influences actual perception of colour
Ecological Valence Theory
Colour preference due to colour-object associations
how good/bad objects associated with that colour are
