Lecture 4 - Occipital & Parietal Lobes Flashcards by Clémentine Cordier

To which cortex does the right visual field project to ?

Left visual cortex

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To which cortex does the peripheral visual field project to ?

Medial visual cortex

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To which cortex does the central visual field project to ?

Peripheral visual cortex

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To which cortex does the upper visual field project to ?

Lower visual cortex

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In which lobe can be found the different visual cortices ?

Occipital lobe

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

Delineation & Orientation

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Which cortices mainly process form & texture ?

V2, V3 & V4

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What are V3 & V4 specialized in ?

V3 : shape of objects in motion
V4 : form & color

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Which area is principally involved in object recognition ?

Area LO

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What does V8 mainly processes ?

Color

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Which cortices are specialized in processing visual motion ?

V3a/MT/V5

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How is functional heterogeneity demonstrated in areas V1 and V2 ?

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

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

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

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

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

Guiding movement based on visual information (vision for action)

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What’s the difference between allocentric & egocentric orientation ?

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

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

Parietal cortex

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What are scotomas and where do lesions causing them occur ?

Scotomas : small blind spots
Lesions : within V1

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

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

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

Cortical blindness : total or partial loss of vision despite normal eyes
Lesions : within V1

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

Blindsight : ability to respond to visual stimuli without conscious awareness
Areas : V1 & V2

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

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

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

Lesions before : affects one eye
Lesions after : affects both eyes & one visual field

What are the different types of agnosia ?

Object agnosia : apperceptive & associative agnosia
Other agnosia : prosopagnosia, alexia, visuospatial agnosia

What's the difference between apperceptive & associative agnosia ?

- 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

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

- Prosopagnosia : Inability to recognize faces - Lesions : bilateral damage near Fusiform gyrus

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

- Alexia : inability to construct whole words from separate letter & to access word memory - Lesions : left fusiform gyrus

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

- 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

How can the parietal lobe be subdivided into ?

- Primary somatosensory cortex (anterior zone) - Secondary somatosensory cortex (posterior zone) - Polymodal cortex

What are the specificities of the anterior parietal lobe ?

- Somatic sensations & perceptions - Tactile, position of own limbs

What are the specificities of the posterior parietal lobe ?

- Integration information from somatic & visual areas to control movement - Eye movement - Reaching - Grasping - Involves spatial information

Name the cortical areas to which the parietal lobes project information

- Motor areas : prefrontal, premotor, supplementary motor & frontal eye field areas - Dorsolateral prefrontal cortex (DLPFC)

What's the somatosensory cortex mainly responsible for processing ?

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

What is astereognosis ?

Inability to recognize an object by touch

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

- 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

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

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

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

Somatosensory symptoms

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

- Balint syndrome (bilateral) - Contralateral neglect (R) - Gerstmann syndrome (L) - Apraxia - Spatial cognition

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

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

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

- Visual neglect : neglect of sensory information in the contralateral (L) field - Lesions : R dorsal parietal

What are the 2 theories about visual neglect ?

- Defective integration of sensation into a percept - Defective attention or orientation

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

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

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

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

What are the 2 types of apraxia ?

- 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