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Brain Dysfunction > Lecture 4 - Occipital & Parietal Lobes > Flashcards

Lecture 4 - Occipital & Parietal Lobes Flashcards

1
Q

To which cortex does the right visual field project to ?

A

Left visual cortex

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2
Q

To which cortex does the peripheral visual field project to ?

A

Medial visual cortex

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2
Q

To which cortex does the central visual field project to ?

A

Peripheral visual cortex

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3
Q

To which cortex does the upper visual field project to ?

A

Lower visual cortex

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4
Q

In which lobe can be found the different visual cortices ?

A

Occipital lobe

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5
Q

What does the primary visual cortex (V1) mainly process ?

A

Delineation & Orientation

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6
Q

Which cortices mainly process form & texture ?

A

V2, V3 & V4

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7
Q

What are V3 & V4 specialized in ?

A
  • V3 : shape of objects in motion
  • V4 : form & color
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8
Q

Which area is principally involved in object recognition ?

A

Area LO

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9
Q

What does V8 mainly processes ?

A

Color

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10
Q

Which cortices are specialized in processing visual motion ?

A

V3a/MT/V5

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11
Q

How is functional heterogeneity demonstrated in areas V1 and V2 ?

A

V1 :
- Blobs : color perception
- Interblob regions : form & motion perception
V2 :
- Thick stripes
- Thin stripes
- Interstripes

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12
Q

What are the 3 main pathways that emerge from area V1 in visual processing ?

A
  • Dorsal (occipitoparietal) stream : vision for action (how)
  • Ventral (occipitotemporal) stream : object recognition & perception (what)
  • STS (superior temporal sulcus) pathway : vision for location (where)
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13
Q

How do lesions in areas V4 and V5 affect visual perception ?

A
  • V4 : achromatopsia (only see shades of gray)
  • V5 : impairs ability to perceive objects in motion
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14
Q

What is the primary function of the dorsal stream in visual processing ?

A

Guiding movement based on visual information (vision for action)

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15
Q

What’s the difference between allocentric & egocentric orientation ?

A

Allocentric : determining spatial location of objects relative to each other
Egocentric : determining spatial location of objects relative to self

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16
Q

Which cortical area is primarily involved in egocentric orientation in space ?

A

Parietal cortex

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17
Q

What are scotomas and where do lesions causing them occur ?

A
  • Scotomas : small blind spots
  • Lesions : within V1
18
Q

What are the possible visual disorders caused by lesions at different levels of the visual pathway ?

A
  • Monocular blindness (optic nerve, before chiasm) -> one eye
  • Bitemporal hemianopia (optic chiasm) -> temporal fields
  • R/L Nasal hemianopia or Binasal hemianopia (lateral chiasm) -> nasal fields
  • Homonymous hemianopia (optic tract, after chiasm) -> one visual field
  • Quadrantanopia (after LGN) -> one visual quadrant
  • Macular sparing (V1) -> one visual field
19
Q

What is cortical blindness and where do lesions causing it occur ?

A
  • Cortical blindness : total or partial loss of vision despite normal eyes
  • Lesions : within V1
20
Q

What’s blindsight, and which visual areas are involved?

A
  • Blindsight : ability to respond to visual stimuli without conscious awareness
  • Areas : V1 & V2
21
Q

What’s agnosia and where do lesions causing it occur ?

A
  • Agnosia : inability to recognize objects despite intact perception, - Lesions : ventral stream (temporal lobe)
22
Q

How does information processing differ before and after the optic chiasm ?

A
  • Lesions before : affects one eye
  • Lesions after : affects both eyes & one visual field
23
Q

What are the different types of agnosia ?

A
  • Object agnosia : apperceptive & associative agnosia
  • Other agnosia : prosopagnosia, alexia, visuospatial agnosia
24
Q

What’s the difference between apperceptive & associative agnosia ?

A
  • Apperceptive : inability to develop a percept of the structure of the object, mostly due to large bilateral or R-sided lesions
  • Associative : inability to identify an object while percept is intact, mostly due to L-sided ventral stream lesions
25
Q

What’s prosopagnosia and where do lesions causing it occur ?

A
  • Prosopagnosia : Inability to recognize faces
  • Lesions : bilateral damage near Fusiform gyrus
26
Q

What’s Alexia and where do lesions causing it occur ?

A
  • Alexia : inability to construct whole words from separate letter & to access word memory
  • Lesions : left fusiform gyrus
27
Q

What does damage to the visual pathways lead to in comparison to damage to cortical regions ?

A
  • Visual pathway : loss of all vision a specific part of the visual field
  • Cortical regions : loss of specific visual information, while others are still perceived
28
Q

How can the parietal lobe be subdivided into ?

A
  • Primary somatosensory cortex (anterior zone)
  • Secondary somatosensory cortex (posterior zone)
  • Polymodal cortex
29
Q

What are the specificities of the anterior parietal lobe ?

A
  • Somatic sensations & perceptions
  • Tactile, position of own limbs
30
Q

What are the specificities of the posterior parietal lobe ?

A
  • Integration information from somatic & visual areas to control movement
  • Eye movement
  • Reaching
  • Grasping
  • Involves spatial information
31
Q

Name the cortical areas to which the parietal lobes project information

A
  • Motor areas : prefrontal, premotor, supplementary motor & frontal eye field areas
  • Dorsolateral prefrontal cortex (DLPFC)
32
Q

What’s the somatosensory cortex mainly responsible for processing ?

A

Somatic sensations & perceptions : touch, pressure, pain, trembling, temperature

33
Q

What is astereognosis ?

A

Inability to recognize an object by touch

34
Q

To what types of agnosia can lead anterior parietal lobe lesions ?

A
  • Asomatognosia : loss of knowledge or sense of one’s own body
  • Anosognosia : unawareness on ones own illness
  • Finger agnosia : unable to point or show their fingers
35
Q

What is extinction and what sensory deficit is associated with it ?

A

Extinction : inability to perceive two identical objects simultaneously, while being able to perceive two different objects
- Deficit : Inability to feel touch on both sides of their body simultaneously

36
Q

What type of deficit are associated with anterior parietal lobe lesions ?

A

Somatosensory symptoms

37
Q

What symptoms/deficits are associated with posterior parietal lobe lesions ?

A
  • Balint syndrome (bilateral)
  • Contralateral neglect (R)
  • Gerstmann syndrome (L)
  • Apraxia
  • Spatial cognition
38
Q

What’s Balint syndrome and where do lesions causing it occur ?

A

Balint syndrome : full visual field & intact recognition/identification but inability to fixate eyes on specific stimuli (+ simult agnosia & optic ataxia)
- Lesions : Bilateral dorsal parietal

39
Q

What’s visual neglect and where do lesions causing it occur ?

A
  • Visual neglect : neglect of sensory information in the contralateral (L) field
  • Lesions : R dorsal parietal
40
Q

What are the 2 theories about visual neglect ?

A
  • Defective integration of sensation into a percept
  • Defective attention or orientation
41
Q

What’s Gerstman syndrome and where do lesions causing it occur ?

A
  • Gerstman syndrome : finger agnosia, acalculia, L-R confusion, agraphia, apraxia
  • Lesions : Angular gyros, area PG
42
Q

What’s Apraxia and where do lesions causing it occur ?

A
  • Apraxia : movement disorder characterized by the loss of skilled movement (normal intellectual abilities)
  • Lesions : posterior parietal cortex & connection to frontal cortex
43
Q

What are the 2 types of apraxia ?

A
  • Ideomotor apraxia (L) : inability to gesture or to copy series of movements (but able for facial movements)
  • Constructional apraxia (R) : inability to assemble a puzzle, constructing & draw in 2 or 3D

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