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PSYC131:Brain and Cognition > Core Vision > Flashcards

Core Vision Flashcards

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1
Q

Where is the retina located?

A

At the back of the eye

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2
Q

Name the two visual receptor cells in the retina

A

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

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3
Q

Describe the function of cone cells

A

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

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4
Q

Describe the function of rod cells

A

involved in the vision in dim light located in the periphery

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5
Q

How do photosensitive pigments play a role in the eye?

A

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

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6
Q

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

A

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)

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7
Q

What is a photon?

A

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

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8
Q

define transduction

A

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

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9
Q

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

A

1.the parvocellular pathway
2.the magnocellular pathway

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10
Q

what is the parvocellular pathway?

A

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

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11
Q

what is the magnocellular pathway?

A

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

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12
Q

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

A

True

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13
Q

what does LGN stand for?

A

lateral geniculate nucleus

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14
Q

what does V1 stand for?

A

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

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15
Q

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

A

Retinal Ganglia Cells

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16
Q

Which of the following best describes the ascending visual hierarchy?

A

Eye > Geniculate Nucleus > Striate Cortex > Extrastriate Cortex

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17
Q

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

A

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

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18
Q

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

A

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

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19
Q

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

A

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

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20
Q

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

A

involved in motion perception

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21
Q

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

A

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

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22
Q

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

A

it’s an ambitious and an extremely influential theoretical approach

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23
Q

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

A

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

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24
Q

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

A

binding visual features together

25
Q

Explain the Binding-by-synchrony hypothesis

A

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

26
Q

How do neurons synchronise?

A

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

27
Q

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

A

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

28
Q

What is the ventral stream?

A

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

29
Q

What is the dorsal stream?

A

■ “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

30
Q

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

A

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

31
Q

What is the Müller–Lyer illusion?

A

Both vertical lines are the same length.

32
Q

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

A
  • 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%
33
Q

Explain the link between illusions and both streams

A

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

34
Q

Explain the Ebbinghaus illusion

A

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)

35
Q

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

A

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)

36
Q

What’s the advantage of the perception action model?

A

It’s a very influential theoretical approach

37
Q

What’s the disadvantages of the perception action model?

A

-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

38
Q

How do both streams differ in connection to the brain?

A

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

39
Q

How do both streams differ in pathways?

A

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.

40
Q

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

A

4.

41
Q

Define Hue

A

The colour itself distinguishing
red from yellow or blue

42
Q

Define brightness

A

The perceived intensity of light

43
Q

Define saturation

A

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

44
Q

Define colour constancy

A

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

45
Q

Define chromatic adaptation

A

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

46
Q

Explain Land’s (1986) Retinex theory

A

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

47
Q

What is the advantage in colour constancy?

A

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

48
Q

What are the disadvantages in colour constancy?

A

-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.

49
Q

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

A

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

50
Q

Define monocular cues

A

requiring only one eye

51
Q

Explain Monocular cues in depth perception

A

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)

52
Q

Explain binocular cues and stereopsis

A

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

53
Q

How is information from
different cues combined?

A

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

54
Q

Explain how information is combined from different cues in
depth perception

A

■ 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

55
Q

What are the two main examples of perceptual constancy?

A

size and colour constancy

56
Q

explain size constancy

A

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

57
Q

explain blindsight: perception without awareness

A

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

58
Q

Explain subliminal perception

A

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

PSYC131:Brain and Cognition (14 decks)

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