Covers the front of the eye & helps focus incoming light, light is bent inward.
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Describe iris & pupil
Coloured part of the eye, circular muscles in iris contract to constrict pupil, controls amount of light entering eye.
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Describe the lens
Focuses light on the retina, muscles flex the lens to accommodate different focal points in the outside world, lens becomes less flexible in long-sightedness.
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Describe retina & fovea
Retina is thin light sensitive lining on the back of the eye, centre of this is the fovea which has high density of photoreceptors, responsible for colour vision, optic disc causes blind spot.
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What is transduction?
When light hits the back of the eye, the processing starts at the retina, light passes through ganglion cells & then polar cells to get to the light sensitive cells, light gets changed into chemical signals which become action potentials.
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What are the different pigments?
Rhodopsin a pigment found in rods, Opsin is found in cones, depolarisation happens in the dark when sodium channels open & release glutamine, hyperpolarisation happens in the light when sodium channels close.
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What are the different photoreceptor types?
Cones- responsible for daytime vision, colour vision, rods- sensitive to low levels of light, monochromatic info, sensitive to movement, action potentials occur in ganglion cells.
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Describe the visual pathway
Retina cells extend into midbrain, info is then passed onto visual cortex, one visual pathway is for seeing what we look at (cortical), another is for controlling where we look (subcortical).
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What are the different types of ganglion cells?
Magnocellular- carry motion info, fast response, input mainly from rods, parvocellular- carry colour & fine detail, slow response, input mainly from cones.
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What was Goodale & Miler's experiment?
On visual agnosia patient, the patient couldn't recognise objects by sight but could by touch, couldn't match orientation but could post a card into a slot, concluded that there is a what pathway & a how pathway.
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What are the different pathways?
Ventral stream- the what stream ventral temporal cortex, dorsal stream- the where stream projects to posterior parietal cortex, orientation, visual attention, localisation, grasp.
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Describe how motion perception works
Simple neural circuits allow simple motion to be detected in retinal cells, full understanding of motion requires integration of many local signals, when parts of the brain involved with vision break down this is known as Akinetopsia which is trouble seei
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What is unilateral visual neglect & prosopagnosia?
When they can only draw one side of a picture, impairment of covert visual attention. This is associated with lesions in the right temporal cortex, cannot identify pictures of family.
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Other cards in this set
Card 2
Front
Describe iris & pupil
Back
Coloured part of the eye, circular muscles in iris contract to constrict pupil, controls amount of light entering eye.
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