Vision

Question 1

What does an ambiguous image lead too?

Answer 1

People not seeing the image, but once they’ve seen it, it will always be there - changed brain forever

Question 2

What are the problems of vision?

Answer 2

Vision is hard to interpret - the eye has a 2D surface (receives things in 2D) but the world is 3D. The angle you look at something changes how you interpret it
The brain has an ambiguous signal, and needs to make sense of it, 2D projection needs to be unpacked and understood by the brain

Question 3

What is computer vision?

Answer 3

Computer vision allows us to pick things out but this can go wrong, they can make more mistakes than we would

Question 4

How does light enter the eye?

Answer 4

It has an opening to it, it comes in through the cornea

Question 5

Where does light travel through?

Answer 5

Through the lens, the lens can be changed to focus on things

Question 6

Where does light hit?

Answer 6

Retina - the back of the eye

Question 7

What does the retina contain?

Answer 7

Cells sensitive to light - photoreceptors

Question 8

What does light pass through before it gets to photoreceptors?

Answer 8

Cells

Question 9

What do photoreceptors contain?

Answer 9

Photopigments - light sensitive molecules why change when light hits them

Question 10

Why are photoreceptors on the edge?

Answer 10

Because they need good nutrients

Question 11

What are the two types of photoreceptors?

Answer 11

Cones - 3 types, sensitive to different wavelengths, day time vision
Rods - contain rhodopsin, respond in dim light

Question 12

What happens in the retinal ganglion cells?

Answer 12

This is the point that we start to process information that is coming in

Question 13

What do retinal ganglion cells code for?

Answer 13

Different properties of the visual stimulus
Each one is responsible for coding something about one thing about the retina - taking input from loads, and processing it

Question 14

What are the two channels of retinal ganglion cells?

Answer 14

Midgit ganglion - small, few connections
Parosol - large
Each project to parvocellular pathway
Cells have receptive fields, - the part of the retina the ganglion is connected too

Question 15

What do single cell recordings on retinal ganglion cells show?

Answer 15

Shine light on receptor field and measure AP
no light - baseline activity
light fills RT - baseline activity
light fills centre - activity increases
light fills surround - activity decreases

Question 16

What did the single cell recordings findings lead too?

Answer 16

On centre, off surround retail ganglion cells- lateral inhibition occurs where take input from a region of the retina, can code when light is specifically in the centre

Question 17

What is lateral inhibition?

Answer 17

Ability of a neutron to reduce activity of its neighbours - disables the spreading of AP’s

Question 18

What are retinal ganglion cells good at?

Answer 18

Detecting sharp edges, this is useful as edges contain a lot of information

Question 19

What are retinal ganglion cells bad at?

Answer 19

Spotting gradual change

Question 20

Perceptual effects

Answer 20

Illusory effect of grey patches, occurs due to an on centre off surround receptive field, inhibitory surround has more inhibition (more light)

Question 21

Simultaneous contrasts

Answer 21

Perceiving 2 pics as different contrasts because of what is surrounding the image, e.g. less surrounding, less inhibition appears light, when more light, appears darer
brain uses contrasts to code and understand what is going on

Question 22

What is the lateral geniculate nucleus?

Answer 22

It is in the thalamus, where all the senses go apart from smell
the gateway where we put mechanism and processes which are important for processing
organised into layers

Question 23

What are the 3 layers of the lateral geniculate nucleus?

Answer 23

Midget - projects to the parvcallular, responsible for colour and detail - red/green differences, makes sense they are smaller as interested in colour

Parasol - projects to magnocellular layers, detection of movement and flicker. larger trying to detect movement so needs to be big so doesn’t go in and out too quick without seeing moevement

Konicellular cells - in between parvocellular and magnocellular layer, blue yellow discrimination

Question 24

Where is the primary visual cortex?

Answer 24

At the back of the brain

Question 25

What is the function of the visual cortex?

Answer 25

50% of dedicated to vision

lots of segments

Question 26

What is the role of V1?

Answer 26

Retinotopic map - each point of visual field maps onto V1 so neighbouring neurons code for neighbouring parts - biased to representing the centre of visual field with more detail, when looking at nose, there will be more detail

Question 27

What does retinotopic map refer too?

Answer 27

Maintaining a map of what is out there

Question 28

What do cells in the visual cortex respond too?

Answer 28

For each given point in visual cortex, there are cells which respond to each orientation - retinotopically organised so neighbours represents orientation next to it

Question 29

If a cat has lots of AP’s to vertical lines, what does it mean?

Answer 29

That this part of the cortex codes orientation

Question 30

What is a critical period?

Answer 30

Kittens raised in tubes with vertical/horizontal stripes. No neurons responded to the orientation that they weren’t in - use it or lose it

Question 31

Beyond V1

Answer 31

Doral pathway - at the back - where? projects to motor system

Ventral - front - what? projects to hippocampus, memories

processig hierarchy at V4, detects shapes