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Psychology 475: Human Neuropsychology > Chapter 13: Occipital Lobe > Flashcards

Chapter 13: Occipital Lobe Flashcards

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1
Q

Why is vision important for humans?

A
  • we devote a large portion of our brain to vision
  • the largest amount of brain devoted to a single sensation
  • most of our daily activities and thoughts are guided by visual information
  • the brain is so dependent upon visual input that you dream when you are asleep and hallucinate after losing sight
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2
Q

Goodales study comparing early blind and late blind echolocators find

A
  • EB: robust echolocation- specific activity in calcarine cortex, BUT NOT IN AUDITORY CORTEX
  • the same was seen in LB thought not as extensive
  • EB and LB showed increase BOLD activity in the calcarine sulcus for recording that contain echoes
  • EB mainly shows increased activity in the calcarine sulcus of the RH
  • LB shows activity at the apex of the occipital lobes of the RH and LH as well as in the calcarine sulcus of the LH
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3
Q

What areas of the brain are active in early blind patients for echolocation

A
  • the calcarine sulcus of the RH
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4
Q

What areas of the brain are active in late blind patients for echolocation

A
  • LB shows activity at the apex of the occipital lobes of the RH and LH as well as in the calcarine sulcus of the LH
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5
Q

What is echolocation

A
  • blind people have learned to navigate using echolocation by making brief auditory clicks, shaking keys or snapping their fingers.
  • when these sounds are echoed off surrounding objects, the blind echolocators can locate and identify objects
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6
Q

What is a Gyrus

A
  • folds on the brain
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7
Q

What is a sulcus

A
  • ridges in the brain
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8
Q

Why do our brains have sulcus and gyrus

A
  • all has to do with surface area
  • there is a very fixed place where the brain fits into the skull , it adapted to developing folds and ridges so you can fit more brain in a small area
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9
Q

where is the occipital lobe located

A
  • behind the parietal-occipital sulus

- but overlapping with many adjacent parietal and temporal regions

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10
Q

Are there clear landmarks that separate the temporal or parietal cortex?

A
  • no there are no clear landmarks

- BUT WITHIN the occipital lobe there are clear landmarks

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11
Q

What is the most prominent landmark within the occipital lobe

A
  • the calcarine sulcus
  • contains much of the primary visual cortex
  • lingual gyrus contains v2
  • fusiform gyrus contains v4
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12
Q

Where does the anatomy we know of the occipital lobe come from

A
  • monkeys

- mostly because it is possible to do invasive studies in monkeys that you cannot do in humans

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13
Q

Who was the first to map the monkey occipital cortex

A
  • Krobinian Broadman
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14
Q

Explain the shape of the human occipital lobe in regards to other lobes

A
  • human occipital lobe extends beyond into the parietal and temporal lobes
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15
Q

How many layers is the typical neocortex comprised of? what is different about the occipital lobe

A
  • 6 layers
  • it is possible to see more in area V1
  • Cortical layer IV alone features four distinct layers and appears as thick as a tripe which gives the visual cortex the nickname the striate cortex
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16
Q

How much of the brain does V1 and V2 together take up?

A

11%

- but V1 is the largest single area in the cortex

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17
Q

What is the function of V1

A
  • it is functionally heterogenous meaning it has multiple functions
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18
Q

What happens what you stain V1 with Cytochrome Oxidase?

A
  • you gets blobs and interblobs
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19
Q

What are blobs

A
  • blobs are critical for the perception of color
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20
Q

What are interblobs

A
  • interblobs are involved in form and motion perception
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21
Q

What happens when you stain V2 with Cytochrome Oxidase?

A
  • reveals stripes rather than blobs and interblobs

- thick , thin and pale stripes

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22
Q

what are thick, thin and pale stripes and where are they found

A
  • V2
  • thick stripes: form perception
  • thin stripes: color perception
  • pale stripes: motion perception
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23
Q

What is V3 involved in ?

A
  • perception of dynamic form

- the shapes of objects in motion

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24
Q

What is area V3A involved in

A
  • form in the dorsal stream
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25
Q

What is V4 involved in ?

A
  • perception of color and form

- does the majority of color processing

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26
Q

What is V5 involved in ?

A
  • motion
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27
Q

Which areas in the occipital lobe are involved in the perception of color

A
  • V1/V2/V4
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28
Q

Why is color so important in primates?

A
  • needed to differentiate edible fruits and poisonous snakes and changing leaves
  • or a partially obstructed yellow banana is quickly seen with colors but in gray scale it would be difficult to detect
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29
Q

Why is it important to study the connections in the brain?

A
  • because nothing in the brain functions in a vacuum

- everything is connected to something else

30
Q

What was the original belief about the level of processing in the occipital lobe?

A
  • it was originally believed that informations moved from V1-V2-V3 etc
  • in hierarchical format
  • but this is way to simple
31
Q

What is the visual pathway in the occipital lobe?

A
  • V1: the first processing level receiving inputs from the Lateral Geniculate nucleus of the THALAMUS and all other occipital areas
  • V2: secondary processing location and also projects onward to major visual areas
  • after V2 there are three distinct parallel pathways that emerge en route to the parietal cortex and inferior temporal cortex (Dorsal , ventral and STS)
32
Q

What does the Dorsal Stream do for the visual system

A
  • the dorsal stream participates in the visual guidance of movements and involves connections from V2 to the parietal lobe
33
Q

What does the Ventral Stream do for the visual system

A
  • involved in the recognition of objects and motion perception
  • V1 to temporal
  • responsible for recognizing objects
34
Q

What does the Superior Temporal Sulcus do for the occipital lobe (STS)

A
  • involved in processing biological movements such as face perception, walking
  • may be uniquely human
  • was only found in 2018
35
Q

What is the function of V1 and V2 together and apart

A
  • “mailboxes”
  • segregate the visual information
  • seperate colour, form and motion
  • information from the blobs in V1 goes to V4 for color processing
  • information from V1 goes to V2 then to V3/MT for motion
36
Q

What happens when theres damage to are V3

A
  • affect form perception

- to completely eliminate form perception you would need a lesion in both V3 and V4

37
Q

What happens with damage to V4

A
  • loss of color perception and a world of grey
  • these patients also lose the ability to remember what colors looked liked before the injury and they cant imagine those colose or think about color
38
Q

What happens with damage to V5

A
  • results in loss of vision of motion

- individuals can see objects when they are at rest but they vanish as soon as the objects move

39
Q

What happens with damage to V1

A
  • basically blind
  • there are a few sneaky ways that info can get to higher levels without travelling through V1
    (blindsight ex)
  • evidence shows that you need V1 t make sense of the info that the higher levels are processing
  • VISUAL PROCESSING CONTINUES BEYOND THE OCCIPITAL LOBES
  • they continue into all other lobes
40
Q

What are the 5 Visual Functions?

A
  1. vision for action
  2. action for vision
  3. visual recognition
  4. visual space
  5. visual attention
41
Q

What is vision for action

A

this type of visual function is required to direct specific movement
ex. when grabbing a cup our vision guides our movement s
- need heavy integration from the parietal cortex to carry out the extensive variety of movements needed
- this can be done with or without attention
-

42
Q

What is action for vision

A
  • Action for Vision – This is a top-down process…the individual actively searches parts of a target object and attends to it selectively. When you look at an object you don’t stare at one place, your eyes are continuously scanning.
  • LVF bias for faces
  • your eyes will continue to due this if you are imagining something, asked to mental rotate something, thinking about what someone was wearing yesterday
  • if you close your eyes this stos
  • probably why we close our eyes in the dark
  • action for vision may interfere with task until the eyes are closed
  • closing eyes improves performance on tasks in the dark
43
Q

What Is visual recognition

A

-but we enjoy the ability to recognize objects and to respond to visual information. We can recognize different faces, letters and symbols and assign meaning to them. This involves the temporal lobe and the ventral pathways

44
Q

What is visual space

A
  • a function that allows up to use visual info that comes from specific locations in space permitting you to direct movements to objects in space and assign meaning to those objects. Visual space is relative tho
    2 ways objects can be described :
    1. egocentric space
    2. allocentric sapce
  • Different aspects of visual processing most likely occurs in both the parietal and temporal visual regions.
45
Q

What is Egocentric space

A

Egocentric Space- objects have a location relative to you (linked to vision for action – how you respond to objects and whatnot in your space)

46
Q

What is Allocentric Space

A

Allocentric Space – objects have a location relative to other objects – based more on spatial memory and visual recognition of other objects.

47
Q

What is Visual Attention

A

Probably one of the most important processes….you need to selectively attend to appropriate visual information. Think about the class right now (or should be in) you can technically see the person in front of you, what they are wearing..etc, but you chose to attend to what I am doing up here etc.

48
Q

How did vision first evolve?

A
  • for motion
49
Q

What is the “what” pathway and what is the How “ pathway

A
  • dorsal stream is the how pathway (guides movement) ventral stream is the what pathway (object recognition).
  • was concluded by Milner and goodale experiments
50
Q

What is the Dorsal Stream involved in

A
  • guiding movement

- How

51
Q

What is the ventral stream involved in

A
  • identifying objects

- we are only actually conscious of a small amount of what the brain is actually doing

52
Q

What is the STS Stream involved In

A
  • provides perceptual representation of biological motion
  • actions of other
  • combination of parietal and temporal processing
53
Q

What are the three visual pathways to recognize objects

A
  • Dorsal (How)
  • Ventral (What)
  • STS
54
Q

What is Top-Down Processing

A
  • TD begin with the most general and move toward the more specific
  • these perceptions are heavily influenced by our expectations and prior knowledge
  • AKA
    your brain applies what it knows to fill in the blanks and anticipate what’s next
55
Q

What is Bottom-Up Processing

A
  • an explanation for perceptions that start with an incoming stimulus and working upwards until a representation of the object is formed in our minds
56
Q

What does the speed with which we interpret visual information suggest?

A
  • that our brain is employing memories about past experiences to make predictions about future or moment-to-moment information that is coming in
  • a professional baseball player or tennis player has to make decisions within milliseconds
  • there must be extensive connections between the prefrontal cortex and both the temporal and occipital lobes to make these interpretations
57
Q

What happens if there is destruction of the retina or optic nerve In one eye

A
  • they would still see the left visual field and this is called Monocular blindness
    (3 and 4 on diagram)
58
Q

What happens is there is a lesion of the medial region of the optic chiasm which severs the crossing of fibres?

A

This is called bitemporal hemianopia and includes a loss of vision in both temporal fields
(1 and 4 in diagram)

59
Q

What happens with a lesion of the lateral chiasm

A
  • This is called right nasal hemianopia and results in loss of one nasal field of vision.
60
Q

What happens with a complete cut of the optic tract, LGN, or area V1

A

This is called homonymous hemianopia or blindness of one entire visual field. So if we sever the connection to the left optic tract we would lose all of the right visual field.

61
Q

Based on the blindness in the visual fields, what can you determine about the injury

A
  • whether the injury is to the eyes or to the optic tract/nerve/brain
62
Q

What is Quadrant Anopia

A
  • Lose ¼ of the visual field. Generally a smaller lesion/not full loss of the optic tract or V1.
63
Q

What is Macular Sparing

A
  • macular sparing occurs only when the damage is unilateral , preserves centre of the visual field
  • bilateral damage is not common, and usually results from something like carbon dioxide poisoning rather than stroke
  • this helps differentiates damage to occipital lobes versus the optic nerve or thalamus
64
Q

How much of the visual field can be lost with macular sparring

A

either complete loss of 1/4 or 1/2 of the visual field

65
Q

both hemianopia and quadranopia is that the border between the impaired visual area and the adjacent intact visual field is?

A
  • sharp
66
Q

What do small occipital lobe lesions often produce?

A

Scotoma

  • Is an area of dimished acuity surrounded by a field of normal vision. Usually caused by a small stroke.
  • You often don’t even know you have it…similar to the blind spot.
  • Need to trick your brain to prove that it is there. Mainly because your eyes are constantly moving.
67
Q

How do you test for a Scotoma

A
  • have patient sit still and not avert their gaze

- then put an object in the scotoma and if nothing is reported you move it into their visual field

68
Q

The fact we can get dissociative symptoms shows what about our belief in unified visual experience

A
  • that it is false

- the brain must treat objects differently if they are moving or still

69
Q

What happens if a patient gets a Bilateral Medial Temporal lobectomy to the anterior 2/3 of ______? and what was the new symptom formed

A
  • two thirds of hishippocampi,parahippocampal cortices,entorhinal cortices,piriform cortices, andamygdala
  • resulted in inability to form new memories
70
Q

Which areas are involved in color processing

A

V1/V2/V4

71
Q

damage in the visual cortex causes what symptoms

A
  • could detect the presence of light but otherwise blind

- retained ability to imagine colors

72
Q

How could you test the different outcomes of V1 +V2 vs V4 damage?

A

Primates (better colour vision).

Psychology 475: Human Neuropsychology (8 decks)

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