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Cognition & Emotion II > Object Recognition > Flashcards

Object Recognition Flashcards

1
Q

THE 2 VISUAL SYSTEM PATHWAYS

A
  1. VENTRAL
    - what aka. vision for perception
    - occipital/temporal cortex
  2. DORSAL
    - where aka. vision for action
    - parietal lobe
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2
Q

POHL (1973)

A
  • what VS where in monkey visual cortex
    A
  • specific pairs of objects predict food award
  • lesions to inferotemporal/ventral cortex impair object recognition aka. WHAT
    B
  • proximity of cylinder to foodwell predicts reward
  • lesions to parietal/dorsal cortex impair spatial recognition aka. WHERE
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3
Q

WHAT VS WHERE: HUMAN NEUROPSYCHOLOGICAL EVIDENCE

A

OCCIPITOTEMPORAL/VENTRAL CORTEX LESIONS
- visual agnosia
- object recognition deficit
PARIETAL/DORSAL CORTEX LESIONS
- hemispatial neglect
- spatial awareness deficits

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4
Q

WHAT VS WHERE: KOHLER ET AL. (1995) PROCEDURE

A

TASK 1
- pps presented w/2 displays; judged if object locations were the same in both (aka. spatial locations)
TASK 2
- pps were again presented w/2 displays; had to judge if all pics = same objects in both (aka. object identities)

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5
Q

WHAT VS WHERE: KOHLER ET AL. (1995) RESULTS

A
  • object > spatial = ventral activation (primarily fusiform gyrus)
  • spatial > object = dorsal activation (inferior parietal cortex)
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6
Q

KARNATH ET AL. (2009): PROCEDURE

A
  • effects of occipitotemporal/ventral visual cortex lesion on vision for action/perception
  • tested a patient (JS) w/circumscribed lesion to ventral occipitotemporal cortex on 2 tasks:
    1) required perceptual judgement
    2) required motor action
  • performance compared against non-lesion controls
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7
Q

KARNATH ET AL. (2009): RESULTS

A
  • perception task = impaired; BUT motor task = normal performance
  • aka. ventral lesions impair vision for perception BUT not vision for action; suggests ventral/dorsal distinction may be more along such lines
  • patient DF (dif study) = similar pattern w/lesser circumscribed lesion
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8
Q

VISUAL AGNOSIA

A
  • impairment in visual perception BUT above lvl of basic sensory deficit (ie. visual field defect)
  • patient cannot recognise/copy/match/discriminate simple visual stimuli OR recognise simple shapes (ie. triangles/circles)
  • inability to group/integrate objects into whole
  • shape processing deficit
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9
Q

ASSOCIATIVE AGNOSIA

A
  • basic perception = fine BUT recognition cannot take place
  • patient can make good object copies BUT cannot recognise them
  • not due to language deficit (ie. anomia)
  • anomia = describe dog pic; say it barks/is a pet
  • associative agnosia = would not know if the dog is animate/inanimate object
  • inability to associate items w/functions
    TEUBER (1968)
  • “a normal perception stripped of its meaning”
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10
Q

ASSOCIATIVE AGNOSIA: MATCHING BY FUNCTIONS TASK

A
  • patients asked to match 2 items most closely related by functions
  • patients w/associative agnosia will choose 2 most visually similar items indicating that they’re unable to retrieve functions associated w/the objects
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11
Q

PROSOPAGNOSIA

A
  • selective deficit in facial recognition
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12
Q

AGNOSIA & OBJECT RECOGNITION: MODULAR APPROACH

A
  • object recognition = modular
  • separate brain systems for dif processes
  • dif agnosia types broadly highlight distinction between:
    1) perceptual processing (shape analysis); impaired in visual form agnosia
    2) semantic processing (associated knowledge activation (ie. function))
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13
Q

AGNOSIA & OBJECT RECOGNITON: CONSTRUCTIVE APPROACH

A
  • object recognition = constructive process
  • brain constructs representations of objects based on many dif sources of contextual info
  • these representations (not simply retinal input) are what we’re consciously aware of
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14
Q

AGNOSIA & OBJECT RECOGNITON: SEMANTIC APPROACH

A
  • object recognition = semantic process
  • info about object meaning = automatically processed when we see it (ie. its function)
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15
Q

VISUAL PATHWAYS: RETINA -> PRIMARY VISUAL CORTEX (V1)

A

1) nasal retina
2) temporal retina
3) optic nerve
4) optic chiasma
5) lateral geniculate nucleus (LGN)
6) primary visual cortex (V1)

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16
Q

PRIMARY VISUAL CORTEX (V1)

A
  • structured retinotopically
    -dif visual field regions (IRL) = perceived in dif V1 regions
  • correspondence (mapping) between spatial structure of primary visual cortex/spatial structure of IRL
  • cortical magnification: disproportionately large V1 area is dedicated to visual field centre (corresponding to eye’s fovea)
17
Q

PROCESSING COMPLEXITY: V1 -> EXTRASTRIATE CORTEX

A
  • processing complexity ^ V1 -> extrastriate cortex:
    V1) neurons sensitive to simple visual features (ie. line orientation/spatial frequency/colour)
    LO) begin to see sensitivity of more complex features (ie. geometric shape)
    V5) plays key role in motion processing
18
Q

KOURTZI & KANWISHER (2001): PROCEDURE

A

LATERAL OCCIPITAL COMPLEX (LOC)
- specialised brain region; integrates features into shapes according to fMRI
- subjects viewed 3 dif types of object (familiar/novel/non-objects)
- 2/3 required feature integration into shapes
- other objects = just disjointed features collection

19
Q

KOURTZI & KANWISHER (2001): RESULTS

A
  • lateral occipital complex activation (part of ventral processing stream) = ^ for familiar/novel objects > scrambled non-objects
  • aka. lateral occipital complex plays role in integrating feature into whole shapes
20
Q

LATERL OCCIPITAL COMPLEX (LOC): PROPERTIES

A
  • largely non-retinotopic area activated by both contralateral/ipsilateral visual fields
  • LOC = not simply sensitive to retinal input
  • seems to encode higher-lvl shape representations even when not defined purely by retinal input
    MENDOLA ET AL. (1999)
  • fMRI evidence that LOC responds to shapes defined by illusory contours
21
Q

FMRI ADAPTATION

A
  • used to map dif component processes of object recognition onto dif regions in ventral visual pathway
  • can investigate sensitivity of neuron groups to dif object properties
  • ie. a neuron sensitive to object identity “knows” pics of car from dif angles = all same object as it reduces its response w/repeated presentations
  • reduction occurs even when repetition occurs from dif POVs aka. neuron = insensitive to POV
22
Q

VUILLEUMIER ET AL. (2002): PROCEDURE

A
  • fMRI adaptation; extent to which activation decreases w/repetitions
  • when you present same object/word x2 -> activation tends to decrease as neurons “adapt” responses to object via varying dif stimuli properties you can access extent to which brain region processes the property
  • eg. dif frequency tones; you may present via dif lengths/frequencies; neurons that process frequency will adapt response to tones of same frequency even if length = dif
23
Q

VUILLEUMIER ET AL. (2002): RESULTS

A
  • found reduced activation in left fusiform cortex to same object from dif POV relative to when dif objects were presented
  • aka. region treats top 2 pics as the same even if presented from dif angles; indicates region may play role in object constancy (enabling us to recognise object under multiple dif contexts/POVs)
24
Q

YEE ET AL. (2010): PROCEDURE

A
  • presented pairs of words that had similar:
    1) function (flashlight-lantern)
    2) shape (marble-grape)
    3) function & shape (pencil-pen)
    4) unrelated (saucer-needle)
    5) identical (drill-drill)
    6) manipulation (defined as type of movement you make when manipulating it)
25
Q

YEE ET AL. (2010): RESULTS

A
  • several brain areas showed adaptation to function esp. in medial temporal lobe (ventral stream)
  • suggests that these neurons actually represent object function aka. objects can be represented in these regions via their functions explaining how neuron loss can result in associative agnosia
26
Q

VENTRAL VISUAL PATHWAY: SEPARATE MODULES

A

LATERAL OCCIPITAL CORTEX
- for integrating features into shapes
LEFT FUSIFORM CORTEX
- for viewpoint invariant representation of objects
LEFT MEDIAL TEMPORAL CORTEX
- for representation of objects’ functions

27
Q

SUMMARY

A
  • 2 visual systems (distinction supported by evidence):
    1) ventral (what/perception)
    2) dorsal (where/action)
  • agnosia:
    1) visual form VS associative agnosia
    2) implications for object recognition system
  • mapping function -> structure in ventral visual pathway; anatomically separate brain regions mediate dif object recognition aspects:
    1) lateral occipital cortex (shape)
    2) left fusiform cortex (object constancy (POV invariant representation))
    3) left temporal cortex (function)

Cognition & Emotion II (15 decks)

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