5.9 Flashcards
rods and cones send impulses along the optic nerve to the
Brain
Light is detected by the
Rods and cones in the retina
Each eye has its own
Visual field
The visual field is the
Region of the environment from which the eye collects light
The visual fields of our 2 eyes overlap, because both eyes are close together and forward facing. This is called
Binocular vision
Light from the right hand side of the visual field focuses on the left side of each retina and light from the left-hand side of visual field focuses on the
Right-hand side of each retina
1)Action potentials from the rods and cones in the retinas pass along the
Optic nerve to the occipital line at the back of the brain
2)Action potentials enter an area known as the
Visual cortex
3)The left and right optic nerves come together at the
Optic chiasma
4) at the optic chiasma about half of the sensory neurones in each optic nerve cross to the other sure of the brain. From here, sensory neurones lass to the
Lateral geniculate nucleus (LGN) and then to the visual cortex
5) As a result, sensory information from both eyes passes to
Each cerebral hemisphere
Each eye is looking at the environment from a slightly different position. This means that the images received from each eye will be very slightly different. The visual cortex processes both images to produce a
Single perceived image
Binocular vision is very useful for judging distances. The brain is able to judge depth and distance from a comparisons of the
2 different images received from each eye
The visual cortex is the part of the brain that interprets or perceives what we see. The images are actually recognised when impulses pass to the
Visual association area
Each part of the visual cortex is devoted to one part of the retina, so the brain can recognise which part of the retina the
Impulses have come from
The bottom up theories propose that perception occurs from using all the
Information available to the eyes
(Bottom-up) there is no need to process the information as the eyes receive
Sufficient information themselves
(Bottom-up) this sufficient information includes how many features?
7
(Bottom-up) feature 1:
Combining 2 images can perceive depth and distance
(Bottom-up)feature 2
The closer an object is to the eye the more the eye are converged
(Bottom up) feature 3:
Closer objects are in front of more distant objects
Bottom up feature 4
Objects closer to the eye can be seen in more detail
Bottom up feature 5
Parallel lines converge (come together) as they spread into the distance
Bottom up feature 6
As you move along, the point you are moving towards remains stationary while the rest of the view moves away from this point - info about speed and direction
Bottom up feature 7:
Clues about distance and speed can be gained from environment
Top down theories of perception are also called
Constructivist theories
Top down theories state that perception does not just rely on the information from the senses but also
Past knowledge, experience and expectations
Evidence for top down theories comes from
Studying visual illusions
(Top down) when we look at a person in the distance or near to us, we perceive them both as being the same
Size even though they cast different images on the retina. Top-down theorists explain they this is because of our
Past experiences
2 theories of visual perception:
Bottom-up
Top-down
