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Psychology 479 > Chapter 13 - Occipital Lobe > Flashcards

Chapter 13 - Occipital Lobe Flashcards

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1
Q

Why is the calcarine fissure important and where is it located?

A
  • It divides the occipital lobe into two separate sections of the occipital lobe (found in the middle, medial view)
  • The upper component corresponds to the lower visual field, while the lower component corresponds to the upper visual field
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2
Q

What does the parieto-occipital sulci divide?

A
  • Separates the parietal and occipital lobes
  • Only visible on a medial view
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3
Q

Fusiform gyrus?

A
  • Plays a role in facial recognition
  • Visible on a ventral view
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4
Q

Lingual gyrus?

A
  • Plays a role in landmark recognition
  • Visible on a ventral view
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5
Q

Retinal ganglion cells (RGCs)?

A
  • Cells found in the retina
  • Transmit receptor info from the rods and cones to the brain
  • They all come together to form the optic nerve
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6
Q

Muller cells?

A
  • A type of glial cell
  • Help funnel light energy to the back of the retina
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7
Q

Rods vs. cones?

A
  • Rods - sensitive to light and moving stimuli
  • Cones - sensitive to colour and fine detail
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8
Q

Which thalamic nucleus plays a major role in the visual system?

A
  • The lateral geniculate nucleus (LGN)
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9
Q

What are the two main categories of RGCs?

A
  • Magnocellular cell (M-cells) - they’re large, receive input primarily from rods, sensitive to light and moving stimuli
  • Parvocellular cell (P-cells) - they’re small, receive inout primarily from cones, sensitive to colour and fine detail
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10
Q

How are M-cells and P-cells distributed throughout the retina?

A
  • M-cells are distributed all throughout the retina
  • P-cells are centralized at the fovea
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11
Q

What are mRGCs?

A
  • melanopsin-containing RGCs
  • Linked to the hypothalamus and help entrain circadian rhythms.
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12
Q

Which layers of the LGN correspond to which RGCs?

A
  • Layers 3-6: P-cells (i.e., cone input)
  • Layers 1-2: M-cells (i.e., rod input)
    *ventral layer starts at one and then we move up
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13
Q

What are the two major routes for visual information?

A

1) Geniculostriate system - conscious awareness of what you’re seeing, info goes to V1 and is processed
2) Tectopulvinar system - Unconsciously done, helps direct eye movement and detects movement location

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14
Q

Which RGCs are involved in the tectopulvinar system?

A
  • M-cells (makes sense cause they help detect movement)
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15
Q

Which info from each eye goes to which layers in the LGN?

A
  • Info from the contralateral side goes to layers 1, 4, and 6
  • Info from the ipsilateral side goes to layers 2, 3, and 5
    *REMEMBER, there are two thalami
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16
Q

What are ocular dominance columns?

A
  • Found in the striate cortex/V1
  • Distinguishes info between the two eyes into separate columns
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17
Q

Which layers of the striate cortex does P-cell and M-cell info make it to?

A
  • Layer 4
  • M-cells - layer 4 alpha
  • P-cells - layer 4 beta
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18
Q

Optic radiations?

A
  • Transmit info from the LGN to the striate cortex (V1)
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19
Q

Which part of the retina processes info from the nasal visual field?

A
  • The temporal retina processes info from the nasal visual field (it’s from the opposite side)
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20
Q

Which part of the retina processes info from the temporal visual field?

A
  • The nasal retina processes info from the temporal visual field
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21
Q

What’s monocular blindness and how does it occur?

A
  • Blindness in one eye
  • Occurs when the optic nerve in one eye is severed and info from one eye cannot be transmitted to the brain
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22
Q

What’s a bitemporal hemianopia and how does it occur?

A
  • There’s a loss of temporal visual visual fields in both eyes
  • Caused by damage to the medial optic chiasm
  • Makes sense cause this is where nasal retina info crosses over
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23
Q

What’s a right nasal hemianopia and how does it occur?

A
  • There’s a loss of the left hemifield in the right eye only
  • Damage is caused by right ipsilateral fibres of the chiasm being severed
    *can also happen in the left eye
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24
Q

What’s an homonymous hemianopia?

A
  • Blindness in an entire visual field
  • Caused by damage to either the optic tracts, LGN, optic radiation or R. V1 (for this case, the entire left hemifield)
25
Q

What would happen if there was a small lesion to the lower calcarine fissure in the left hemisphere?

A
  • There would be a scotoma in the upper right visual field
26
Q

What’s a quadrantanopia?

A
  • When there are visual deficits found in one quadrant of one of the visual fields
  • May be caused by damage in V1
27
Q

What was the case of patient B.K and their scotoma?

A
  • They had a tumour found below their calcarine fissure in their right primary visual cortex
  • Tumour was caused by migrainous infarction
28
Q

What’s a perimetry test?

A
  • A visual field test used to detect areas of reduced vision
29
Q

Why do humans have a normal blind spot?

A
  • Due to where the optic nerve converges at the back of the retina, there are no sensory receptors at this one area
30
Q

What’s blindsight?

A
  • The ability of patients with visual-field deficits to identify at better-than-chance levels the nature of visual stimuli that are not consciously perceived
  • Also called cortical blindness
  • Not a conscious form of perception, but they can still detect colour, motion, and location
31
Q

What’s an explanation for why blindsight can occur in those who are cortically blind?

A
  • The tectopulvinar system still works, so the individual can still unconsciously detect visual functions such as location, movement, and line orientation
  • The pulvinar is a nucleus in the thalamus
32
Q

What are the three major parallel pathways found after visual info reaches V2?

A

1) Dorsal stream (“how” stream)
2) Ventral stream (“what” stream)
3) STS (superior temporal sulcus stream)

33
Q

What’s the STS stream?

A
  • Part of a multimodal cortex characterized by polysensory neurons
  • Potential point of interaction between dorsal and ventral streams
  • May provide a perceptual representation of biological motion (i.e., the actions of others
  • May be involved in language and tool use
  • It’s a conscious stream
34
Q

T/F: The dorsal stream is unconscious.

A
  • TRUE
35
Q

What evidence for the three parallel streams was provided using experiments on monkeys in the 1980s?

A
  • Visual neurons in the posterior parietal region are only active when the brain ACTS on visual info
  • VIsuomotor and visuospatial impairments are often associated with lesions to the parietal cortex
36
Q

What would happen if there was an injury to the “what” pathway (ventral stream)?

A
  • Visual form agnosia would occur
  • Individual would be unable to identify or copy drawings of objects, but they would be able to unconsciously make actions to properly pick them up
  • Ex. cannot identify a mug in front of them, but would make proper hand forms to grasp the handle
37
Q

What would happen if there was an injury to the “how” pathway (dorsal stream)?

A
  • Optic ataxia would occur
  • Individual has a deficit in the visual control of reaching and other movements
  • Ex. The grip points on the objects they try to grasp are completely random
38
Q

What does the visual motor posting task assess?

A
  • To assess whether a patient can properly orient the envelope to fit into the slot
  • Ex. Patient DF with damage to the ventral stream is unable to imagine orienting the envelope cause they cannot match the slot to the envelope in their head. But when asked to physically guide the envelope into the slot, they can do it easily because their dorsal stream is still intact
39
Q

Apperceptive agnosia vs. Associative agnosia?

A
  • Apperceptive agnosia - elementary sensory functions appear intact, but a perceptual deficit prevents object recognition (i.e., unable to draw, copy, or recognize a figure)
  • Associative agnosia - inability to identify/recognize an object, despite its apparent perception (i.e., can copy a drawing, but cannot identify it
40
Q

What are the causes of the different agnosias?

A
  • Apperceptive - bilateral damage to lateral occipital lobes
  • Associative - deficit of a higher level of cognitive processing than apperceptive agnosia (not as bad), might be damage to the anterior end of the temporal lobes in the ventral stream
41
Q

Which stream is responsible for object perception?

A
  • The ventral stream
42
Q

Which components of the visual system are considered the extrastriate cortex?

A
  • V2-V5
43
Q

Which Broadmann’s area corresponds to V1?

A
  • BA17
44
Q

T/F: V1 and V2 are anatomically and functionally heterogenous

A
  • TRUE
45
Q

What do the different stripes in V2 correspond to in terms of function?

A
  • Thin stripes - colour perception
  • Thick stripes - movement
  • Pale stripes - Form
46
Q

What do the different blobs in V1 correspond to in terms of function?

A
  • Blobs - colour perception
  • Interblobs - form and motion perception
47
Q

What are V3, V4, and V5 responsible for?

A
  • V3 - form
  • V4 - colour
  • V5 - motion
48
Q

Which areas of V1 correlate to which areas in V2 and then which areas of the visual cortex do they expand to?

A
  • V1 Blobs -> V2 thin stripes -> V3 -> temporal lobe
  • V1 interblobs -> V2 thick and pale stripes -> V3 (thick) and V4/V5 (pale) -> Parietal lobe (V5) and temporal lobe (V4)
49
Q

What would a lesion to V4 cause?

A
  • Lack colour perception and cognition
  • i.e., would see, imagine, recall everything in black and white
50
Q

What would a lesion to V5 cause?

A
  • Lack of motion perception
  • i.e., any object in motion disappears and then would reappear later, like teleportation
  • Could not pour liquids
51
Q

What would a lesion to V3 and V4 together cause?

A
  • Lack form perception
  • This would be a larger lesion
52
Q

What did case L.M. demonstrate regarding V5 and the perception of form?

A
  • Patient could not see motion, but colour and object recognition remained intact
  • Clear indication that the brain processes the movement of form, separately from the form itself
  • V5 likely involved in both dorsal and ventral stream processing
53
Q

What are the five general categories of visual processing?

A

1) Vision for action
2) Action for vision
3) Visual recognition
4) Visual space
5) Visual attention

54
Q

What’s vision for action?

A
  • Visual processing required to direct specific movements
  • Movement may result from a conscious decision to reach for the mug, but hands form proper shape automatically
  • Regions include guide grasping, eye movements, head movement etc.
55
Q

What’s action for vision?

A
  • More of a top-down process
  • Attending to specific parts of a stimulus/object
  • Important for perception
56
Q

Egocentric vs. Allocentric space?

A
  • Egocentric - an object’s location relative to the observer (central to controlling your actions towards objects)
  • Allocentric - an object’s location relative to other objects, independent of the observer’s perspective (usually at a distance; depends on identifying features of the world)
57
Q

What’s Prosopagnosia?

A
  • Facial recognition deficit
  • Caused by right or bilateral lesions below the calcarine fissure at the temporal junction (fusiform gyrus)
58
Q

What’s Alexia?

A
  • Inability to read
  • Often caused by a left occipitotemporal lesion, causing a right hemianopia

Psychology 479 (13 decks)

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