The Visual System 1
- Created by: meg_lou
- Created on: 29-04-17 12:17
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- The Visual System 1
- Structure of the eye
- Light
- Our eye detects different wavelengths and intensities of light
- Human visual spectrum between 380-760 nanometers
- Travels at 186,000 mps
- Wavelength = colour
- Wave amplitude = brightness
- The eye
- 1. Eye detects change in wavelength and intensity of light
- 2. Cornea gathers light and it passes through
- 3. Light reaches the pupil
- 4. Iris regulates amount of light
- Light entering eye is dark or aroused (dilate)
- Light entering eye is bright (constricted)
- Lens focuses light onto the retina to bring image into focus
- The retina
- 2 types of light-sensitive receptors on the retina
- Cones for colour = 6 million
- Cones that absorb long wavelength light (red), middle wavelength light (green) and short wavelength light (blue
- Rods for dim light = 120 million
- Cones for colour = 6 million
- 2 types of light-sensitive receptors on the retina
- Light
- From the retina to the PVC
- Colour
- Trichromatic theory of colour
- People with normal colour vision needed 3 different wavelengths to match any wavelength in the visible spectrum
- Doesn't explain how extensive attention to one colour produces its complimentary colour
- Colour blindness is red/greeen, yellow/blue
- Colours are linked
- Opponent process theory
- Colours are linked together no two members of a pair can be seen at the same location
- E.g. never see something that is a bluish yellow colour
- E.g. Red-green cell signals red when it is excited and signals green when inhibited
- Explains colour blindness - will confuse either red/green or blue/yellow
- 2 different classes of cells for encoding colour and brightness
- Colours are linked together no two members of a pair can be seen at the same location
- Trichromatic theory of colour
- Structure of the retina
- Ganglion cell axons come together to form optic nerve
- Has blindspots
- Pathway receptor cells reach brain via action potentials
- Path from retina is optic chiasm, 80% lateral geniculate nucleus of the thalamus, PVC
- Colour
- Cortical visual areas
- Ventral
- 'What' stream for face recognition and objects
- Dorsal
- 'Where/how' stream for location and visuomotor skills
- Includes mirror neurons that respond to sight of another's actions
- Layers of lateral geniculate nucleus
- Parvocellular
- Composed on neutrons with small cell bodies
- Sensitive to colour
- Magnocellular
- Insensitive to colour but responsive to movement
- Parvocellular
- Ventral
- Structure of the eye
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