Vision

Question 1

The problem of vision

Answer 1

• the retina sees a 2D projection of a 3D world
• could think one objects seen at different orientation as different objects
• or could see different objects of the same shape as the same object when really they are different

Question 2

The eye

Answer 2

retina, pupil, iris, cornea and lens, accommodation

Question 3

pupil

Answer 3

light enters eye

Question 4

iris

Answer 4

adjustable aperture

constricts in bright light to make pupil smaller

Question 5

cornea and lens

Answer 5

focuses light onto retina

Question 6

accomodation

Answer 6

ciliary muscles change shape of lens to bring objects into focus at different distances

Question 7

retina composition

Answer 7

photoreceptors (rods and cones)

Question 8

photoreceptors

Answer 8

cells with light sensitive photopigments in outer segments

results in an action potential

Question 9

rods

Answer 9

contain rhodopsin

respond in dim light
- e.g. at night

none is fovea

Question 10

cones

Answer 10

three types

sensitive to daylight and colour vision

Question 11

retinal ganglion cells

Answer 11

downstream from photoreceptors

last stage of retinal processing

begin to process visual info

large parasol and small midget

Question 12

Large parasol ganglion cells

Answer 12

• large receptive fields
• connected to large areas of the retina
• and to a large no. of photoreceptors
• magnocellular system

Question 13

small midget ganglion cells

Answer 13

• smaller receptive fields
• small areas of the retina and t a small no. of photoreceptors
• parvocellular system

Question 14

recepetive field

Answer 14

the part of the retina from which the ganglion cells receives input

Question 15

no light in receptive field

Answer 15

baseline activity

Question 16

light fills receptive field

Answer 16

baseline activity

Question 17

light fills centre of receptive field

Answer 17

activity increases

Question 18

light fills surrounding of receptive field

Answer 18

activity decreases

Question 19

on centre, off surround

Answer 19

excitation on centre
inhibition on surrounding

Question 20

off centre, on surround

Answer 20

other way around
excitation on surrounding inhibition on centre

Question 21

retinal ganglion processing make us good at..

Answer 21

picking out edges

Question 22

retinal ganglion processing makes us bad at..

Answer 22

spotting gradual change

Question 23

Lateral Geniculate Nucleus (LGN)

Answer 23

• part of thalamus
• layers
• each layer has different roles within vision
• parvocellular - outer
• magnocellular - inner
• koniocellular cells - in between layers

Question 24

magnocellular pathway conveys info on ..

Answer 24

movement and flicker

Question 25

parvocellular pathway conveys info on ..

Answer 25

colour and detail

Question 26

koniocellular cells convey info about ..

Answer 26

blue-yellow

Question 27

Primary visual cortex (V1)

Answer 27

• up to 50% of cortex is dedicated to vision - visual cortex and beyond
• V1 aka striate cortex

Question 28

Retinotopy

Answer 28

• visual mapping
• two adjacent parts of visual field have adjacent neurones in the cortex

Question 29

Hubel and Wiesel

Answer 29

• experimented on cats
• found cells sensitive to different orientations of vertical lines

Question 30

critical periods

Answer 30

• need to see lines with different orientations in order to form behaviours and cells responsive to different line orientations during a critical period of life

Question 31

dorsal stream

Answer 31

along top

• plan movements
• where things are in space
• where?

Question 32

ventral stream

Answer 32

along bottom

• projects to memory areas
• colour info
• what?