Sight and Visual Pathways

Question 1

how can vision be experienced differently?

Answer 1

through
- motion
- 3D vision
- HD
- technicolour

Question 2

where does sensory processing start?

Answer 2

in the eye, as the retina is part of the brain

Question 3

what must the retina cope with?

Answer 3

transmitting the right amount of data in order to see the world clearly, but not enough to require a greater processing power

Question 4

how do retinal images begin?

Answer 4

the wrong way around and flipped side to side - variable resolution

Question 5

what must the brain do to retinal images?

Answer 5

change to the correct image outside of our conscious awareness
- shows how conscious perceptions of reality are different to mental interpretations of excited visual neurones

Question 6

how does the eye grab information?

Answer 6

through receptive fields

Question 7

receptive fields

Answer 7

region in the sensory periphery within which stimuli influence the electrical activity of sensory cells

Question 8

when do photoreceptors only respond?

Answer 8

when light falls on their receptive field

Question 9

output of photoreceptors

Answer 9

take the form of action potentials in retinal ganglion cells, whose axons take up the optic nerve

Question 10

what happens to receptive fields as they get deeper into the brain?

Answer 10

get more structured and specific

Question 11

how are receptive fields organised?

Answer 11

to detect changes in vision, by having different regions which turn cells on and off

Question 12

where are retinal ganglion cells?

Answer 12

on the inner surface of the retina

Question 13

what are retinal ganglion cells?

Answer 13

the output of the eye, which can have different receptive fields

this changes understanding of how the brain detects contrast and change

Question 14

receptive fields of RGC

Answer 14

on-centre and off-surround cells become active and fire AP when receiving information that is greater when compared to the surround

Question 15

other types of RPG receptive fields

Answer 15

off-centre and on-surround

Question 16

the consequence of centre-surround antagonism

Answer 16

“simultaneous contrast illusion”

Question 17

“simultaneous contrast illusion”

Answer 17

1. on-centre receptive fields (on the darker background) are not inhibited, as there is less light to activate the off-surround, so the bar appears lighter
2. on-centre cell (on the lighter background) is inhibited because there is more light to activate the off-surround, so the bar appears darker

Question 18

how is retinal output used to signal changes?

Answer 18

by detecting edges over space, which breaks pictures apart due to centre-surround features and high sensitivity

Question 19

what does edge detection provide the brain with?

Answer 19

lots of information about a scene to distinguish objects from their background

Question 20

what do RGC respond to?

Answer 20

sudden changes in light over time

however, if this light stays on for a prolonged period of time then cells become inhibited

Question 21

craik o’brien cornsweet illusion is a consequence of…

Answer 21

seeing only edges, as images containing only edges pass through the retina unchanged, whereas normal images are converted into edges

• interpreted in the same way by the brain

Question 22

what are troxler fading and after-images?

Answer 22

an optical illusion where the fixation point disappears after focusing on this for a short period of time

Question 23

how are after-images produced?

Answer 23

sudden removal of a prolonged image causes an after-image, as inhibition has a time lag

Question 24

what does output from the retina reach?

Answer 24

the lateral geniculate nucleus

Question 25

what is the LGN?

Answer 25

where information from the left and right VF combines in the brain, and RGC become specialised for motion or colour

Question 26

what cells appear in the LGN?

Answer 26

parvocellular and magnocellular

Question 27

parvocellular cells

Answer 27

respond to red-green colour, slow response, sensitive to detail, fine-detail resolution information

Question 28

what do parvocellular cells respond to?

Answer 28

magnocellular cells
- used for motion, faster response, peripheral dominant, course detail

Question 29

the LGN is the main…

Answer 29

relay point from the optic nerve on the way to the cortex

Question 30

what is the LGN important for?

Answer 30

filtering what information reaches the cortex, by serving as the spotlight of attention to highlight information from certain parts of the VF

Question 31

LGN and cortex

Answer 31

LGN provides top-down input to cortex

Question 32

LGN layers

Answer 32

six layers - 3 are from ganglion cells, and 3 from eye axons

information is represented in both LGNS for each eye, kept segregated

different layers contain different information about motion and colour

Question 33

layers 1 and 2

Answer 33

receive information about motion

Question 34

layers 3, 4, 5, 6

Answer 34

receive information about colour

Question 35

which LGN sees which VF?

Answer 35

left LGN sees the right VF
right LGN sees the left VF

information arrives in separate halves of the brain before entering the visual cortex

Question 36

division of visual pathways

Answer 36

dorsal stream
ventral stream

Question 37

dorsal stream

Answer 37

where objects are processed in space, motion, and depth

V3, V5/MT, V6, V7

Question 38

ventral stream

Answer 38

recognising faces, places, and objects

V1, V2, V4, V8, LOC, OFA, FFA, PPA