Visual system only responds to a quanta of light of a certain wavelength (380-760nm) -these quanta are called photons
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3 dimensions of perception of light
brightness, hue (shade of colour), saturation (depth of colour)
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lateral inhibition
interconnected neurons in retina inhibit their neighbours, result is a perceived contrast at edges of regions, however 2 patches that appear to differ have same amount of light
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binocular disparity
2 eyes to enable VS to create 3D images from 2D retinal images -diff in position of same image on the 2 retinas
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cells of retina
-5 layers light must pass through to reach receptors, photoreceptors include rods and cones
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Rods and cones
-activate bipolar cells which activate ganglion cells which form optic nerve -optic nerve carries visual info to brain
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retinal cells
-horizontal cells connect with receptor cells and bipolar cells -amacrine cells connect with bipolar and ganglion cells -fovea-thinning of retina ganglion cell layer at centre of retina (high acuity region)
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cones
cone shaped receptors, for vision in good lighting, high acuity&colour, photopic vision -only cones found in fovea-high acuity
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rods
rod shaped receptors, more sensitive for dim lighting, lacks detail and colour, scotopic vision
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parvocellular
colour, fine detail
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magnocullular
movement
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V1
primary visual cortex
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V3
form
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V4
colour perception
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V5 (MT)
motion
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mach bands
non-existent strips of brightness and darkness running alongside the edges
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