Core Vision

Question 1

Where is the retina located?

Answer 1

At the back of the eye

Question 2

Name the two visual receptor cells in the retina

Answer 2

rod cells and cone cells (Retinal ganglion cells receive input from a
few cones or hundreds of rods) 120 mil photoreceptors containing the nucleus

Question 3

Describe the function of cone cells

Answer 3

involved in colour and detail perception mainly located in the fovea (which is the centre of field of vision) which is usually in the middle of the retina

Question 4

Describe the function of rod cells

Answer 4

involved in the vision in dim light located in the periphery

Question 5

How do photosensitive pigments play a role in the eye?

Answer 5

it changes shape when a photo of light touches it generating an electrical impulse.

Question 6

Explain the process of projection from the eye/retinal to the visual cortex

Answer 6

1.physical energy absorbed which is the detection of photons (reception)
2.this energy is then converted into an electrochemical pattern in the neurons (transduction)
3.One-to-one correspondence between aspects of the physical stimulus and aspects of the resultant nervous system activity (coding)

Question 7

What is a photon?

Answer 7

a tiny (energy) particle or bundle of electromagnetic radiation which can travel at the speed of light.

Question 8

define transduction

Answer 8

the transportation/transformation of something from one place to another (in this case, info from the physical world is transformed into neural patterns)

Question 9

What are the two main aspects of the Retina-geniculate-striate system?

Answer 9

1.the parvocellular pathway
2.the magnocellular pathway

Question 10

what is the parvocellular pathway?

Answer 10

-it’s sensitive to colour and fine detail
-most input comes from cone cells

Question 11

what is the magnocellular pathway?

Answer 11

-it’s most sensitive to motion
-most input comes from rod cells

Question 12

True or False:the left/right visual fields are contralateral to the hemispheres

Answer 12

True

Question 13

what does LGN stand for?

Answer 13

lateral geniculate nucleus

Question 14

what does V1 stand for?

Answer 14

primary visual cortex (takes 60ms for info to arrive here)

Question 15

Which type of cells leaves the eye and synapse in the lateral geniculate nucleus?

Answer 15

Retinal Ganglia Cells

Question 16

Which of the following best describes the ascending visual hierarchy?

Answer 16

Eye > Geniculate Nucleus > Striate Cortex > Extrastriate Cortex

Question 17

Functional specialisation theory (Zeki, 1993, 2016):what’s the functions of V1/V2?

Answer 17

basic visual processing
V1=primary visual cortex (or striate cortex)
V2=the area surrounding the primary visual cortex

Question 18

Functional specialisation theory (Zeki, 1993, 2016):what’s the functions of V3 and V3A?

Answer 18

involved in form perception (especially of moving stimuli)
V3=visual areas/extrastriate cortex
V3A=a cortical area(located in the cerebral cortex)

Question 19

Functional specialisation theory (Zeki, 1993, 2016):what’s the functions of V4?

Answer 19

involved in colour and shape perception
V4=visual area 4 which is the third cortical area in the ventral stream,

Question 20

Functional specialisation theory (Zeki, 1993, 2016):what’s the function of V5/MT in humans?

Answer 20

involved in motion perception

Question 21

Functional specialisation theory (Zeki, 1993, 2016):what’s the function of LOC, OFA and FFA?

Answer 21

LOC – Object Perception
OFA – Face perception
FFA – Face perception

Question 22

What are the advantages of Zeki’s functional specialisation theory?

Answer 22

it’s an ambitious and an extremely influential theoretical approach

Question 23

What are the main three disadvantages of Zeki’s functional specialisation theory?

Answer 23

1.visual brain areas are less specialised than theoretically assumed
2.visual brain more complex than assumed (V1 associated with 50 other brain areas)
3.the binding problem remains unsolved

Question 24

Given functional specialisation, how is visual information combined and integrated?

Answer 24

binding visual features together

Question 25

Explain the Binding-by-synchrony hypothesis

Answer 25

– Neurons that code difference dimensions start to oscillate in synchrony/connect together. (unclear how and why the synchrony might occur.) – Precise synchrony is implausible

Question 26

How do neurons synchronise?

Answer 26

they switch between low and high excitability to synchronise allowing better communication.

Question 27

What are the main features of the Perception-action model (Milner & Goodale, 1977)

Answer 27

the dorsal and ventral stream (they're not really early visual systems)

Question 28

What is the ventral stream?

Answer 28

■ “What” pathway ■ Vision-for-perception ■ Allocentric (object-centred) coding ■ Sustained representation (lasts roughly a second) ■ Usually conscious awareness ■ Input from the fovea

Question 29

What is the dorsal stream?

Answer 29

■ “Where” pathway ■ Vision-for-action e.g., returning a tennis ball (fast reaction) using visual info to control action ■ Egocentric (body-centred) coding ■ Short-lived representations ■ Usually unconscious

Question 30

What's the key difference between the dorsal and ventral streams?

Answer 30

Ventral is consciousness representation whereas dorsal is rapid action and as they're both specialised any damage in the brain will have a different effect

Question 31

What is the Müller–Lyer illusion?

Answer 31

Both vertical lines are the same length.

Question 32

What were the findings of Bruno et al., 2008?

Answer 32

* When pointing (using vision-for-action system), illusion size was 5.5% * When verbalising a response (using vision-for-perception system), the illusion size was 22.4%

Question 33

Explain the link between illusions and both streams

Answer 33

illusions are mediated by the ventral stream and action the dorsal so pointing doesn’t have as much as an effect

Question 34

Explain the Ebbinghaus illusion

Answer 34

Both centre circles are same size but the one in the top figure looks larger than the one in the bottom figure * Illusion greater with vision-for-perception system than vision-for-action system * Only perceptual judgements influenced by distance between the centre circle and contextual circles (Knol et al., 2017)

Question 35

What are the complexities of grasping movements in relation to the streams?

Answer 35

Grasping objects requires both the ventral stream (vision-for perception) and dorsal stream (vision-for-action) when: 1. Information from memory required to control grasping movements 2. Conceptual knowledge needed to make most appropriate grasping movement (e.g., grasping a toothbrush by its handle rather than bristles)

Question 36

What's the advantage of the perception action model?

Answer 36

It's a very influential theoretical approach

Question 37

What's the disadvantages of the perception action model?

Answer 37

-Two systems less independent and more interactive than assumed theoretically (isn't necessarily a disadvantage just showing it's getting more precise theory wise) ■ Patients with optic ataxia and visual form agnosia have problems with BOTH vision-for-perception and vision-for-action: no clear double dissociation ■ Findings with visual illusions are variable There are two dorsal systems: 1. dorso-dorsal systems used to grasp object rapidly; 2. ventro-dorsal system using memorised object knowledge to use objects appropriately

Question 38

How do both streams differ in connection to the brain?

Answer 38

The ventral stream connects V4, LOC and IT WHEREAS the dorsal stream connects V5 to the posterior parietal lobes.

Question 39

How do both streams differ in pathways?

Answer 39

The ventral stream is an extension of the parvocellular pathway, stemming from cones in the foveal region WHEREAS the dorsal stream is an extension of the magnocellular pathway.

Question 40

What is the correct answer?: The ventral stream 1. Supports conscious perception of objects and scenes 2. Generates known visual illusions 3. Controls rapid motor responses like returning a tennis serve 4. A and B but not C

Answer 40

4.

Question 41

Define Hue

Answer 41

The colour itself distinguishing red from yellow or blue

Question 42

Define brightness

Answer 42

The perceived intensity of light

Question 43

Define saturation

Answer 43

Allows us to determine whether colour is vivid or pale; influenced by the amount of white present

Question 44

Define colour constancy

Answer 44

A perceived colour will remain the same despite changes in the wavelengths in the illuminant (light source)

Question 45

Define chromatic adaptation

Answer 45

Sensitivity to illuminant/light source of any given colour decreases over time.

Question 46

Explain Land's (1986) Retinex theory

Answer 46

Observers compare light reflected from a surface against that reflected from adjacent surfaces

Question 47

What is the advantage in colour constancy?

Answer 47

Several factors influencing colour constancy have been identified including object familiarity which influences early visual processing (Vandenbroucke et al., 2016)

Question 48

What are the disadvantages in colour constancy?

Answer 48

-Little is known about how factors combine to produce colour constancy -artificial visual environments used in research simpler than those in the natural world -Generally less colour constancy when observers try to make objective judgements about colour (e.g., what colour is it?) rather than subjective ones (e.g., what colour does it look like? -Large individual differences in colour constancy poorly understood.

Question 49

What describes the phenomena of colour constancy? i.e. why does colour remain constant?

Answer 49

Objects appear to have an intrinsic(natural/essential) colour, despite variations in lighting and reflection.

Question 50

Define monocular cues

Answer 50

requiring only one eye

Question 51

Explain Monocular cues in depth perception

Answer 51

Linear perspective: based on laws of optics (can have crossing lines) Texture: objects slanting away have a texture gradient Interposition: a nearer object hides part of a more distant one Familiar size: the distance of familiar objects is easier to judge than that of unfamiliar ones Blur: ambiguous (far away or in peripheral vision?) Motion parallax: movement in one part of retinal image relative to another (speed of motion is proportionate to the depth)

Question 52

Explain binocular cues and stereopsis

Answer 52

Stereopsis enhances depth perception (and allows us to see the environment in 3D) ■ Stereopsis based on slight difference/disparity between the two retinal mages (binocular disparity) as the retinal image in each eye is different ■ Stereopsis is powerful at short distances only ■ Individuals with amblyopia (“lazy eye”) have impaired stereoscopic depth perception -binocular disparity can be seen in 3D cinemas

Question 53

How is information from different cues combined?

Answer 53

Additivity– Information from all cues is combined or integrated Selection– Information from a single cue is used, ignoring information from the other cue/s Weighting of cues– More reliable cues (e.g., those providing consistent information) weighted more

Question 54

Explain how information is combined from different cues in depth perception

Answer 54

■ Small conflicts between cues=adherence to additivity notion and weighting of more reliable cues ■ Large conflicts between cues= heavy reliance on only one cue: selection ■ Depth perception is often close to optimal ■ In natural environments with rich information available, observers rely on a global assessment of environmental structure rather than specific cues ■ This is very different from processing cues independently followed by integrating information from them

Question 55

What are the two main examples of perceptual constancy?

Answer 55

size and colour constancy

Question 56

explain size constancy

Answer 56

Size perception of objects depends on the memory of their familiar size + perceptual information ■ It is better with familiar objects having invariant size (e.g., bicycles) than variable size (e.g., TV sets) -size constancy extracts info from the ways things are, not how it appears to be

Question 57

explain blindsight: perception without awareness

Answer 57

The ability to respond appropriately to visual stimuli lacking conscious visual experience in patients with damaged primary visual cortex (V1) (the brain reorganised itself so information can bypass V1) Type-1 blindsight: no conscious experience; Type-2 blindsight: some residual awareness ■ Blindsight patients often show evidence of degraded conscious vision when sensitive measures of conscious awareness are used ■ The reorganisation of brain connectivity in blindsight patients explains many findings

Question 58

Explain subliminal perception

Answer 58

Subliminal perception involves: – Subjective measure: the Observer’s failure to report awareness of a stimulus – Objective measure: the Observer’s ability to make accurate forced-choice decisions about a stimulus -Numerous studies support subliminal perception but less evidence for subliminal perception with more sensitive measures of conscious awareness: partial awareness? – Evidence of weak awareness + response bias (reluctance to report awareness) (Koivisto & Grassini, 2016) -Subliminal is quick flash might be conscious but perhaps quickly forget what was flashed on the screen