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A Intro to Neuro > Vision 3 > Flashcards

Vision 3 Flashcards

1
Q

Primary Visual Cortex (V1, Area 17, Striate Cortex)

A
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2
Q

Ocular dominance columns

A
  • Originate from layer 4C: inputs from the L and R eye remain segregated
  • Layer 4C is monocular → last time in visual pathway where input from the two eyes is separated
  • V1 layers outside of layer 4C are binocular, but are still “dominated” by one eye depending on their proximity to left eye input in layer 4C or right eye input in layer 4C → produces ocular dominance columns
  • Ocular dominance columns run perpendicular to V1 layers
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3
Q

Where do ocular dominance columns originate?

A

4C

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4
Q

In ocular dominance columns, is input from the right and left eyes segregated or integrated?

A

Segregated

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5
Q

Which layer is the last to be monocular (input from the two eyes is separated)?

A

4C

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6
Q

V1 layers outside of layer 4C are __

A

Binocular

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7
Q

Even though V1 layers outside of layer 4C are binocular, they are still ___

A

Dominated by one eye –> produces ocular dominance columns

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8
Q

Ocular dominance columns run ___ to V1 layers

A

Perpendicular

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9
Q

Summary table of RFs in V1

A
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10
Q

RF properties in layer 4C

A
  • Center/surround antagonistic RF similar to LGN
  • Some color, some B/W
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11
Q

RF properties of layers 2, 3, 4A, 4B, 5, 6

A
  • Orientation selectivity
  • Direction selectivity
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12
Q

Orientation selectivity

A
  • Certain orientation gives highest response
  • Response can be graded: Angles closest to the best orientation cause stronger response than angles farther to best orientation (perpendicular → weakest response)
  • Form orientation columns
    ○ Similar concept to ocular dominance columns
    ○ BUT on perpendicular axis to ocular dominance columns
    ○ Spatial sequence follows gradual rotation
  • Used for edge detection → form perception
    (based on distributed code of activity of selective neurons spread across columns → gives you whole picture)
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13
Q

Direction Selectivity

A
  • Makes up a subset of neurons that are
    orientation selective
  • Response based on orientation AND
    direction of movement
  • Responses also graded: Closer direction produce closer response than farther directions (opposite direction produces the weakest)
  • Used for motion perception (also based on distributed code of direction-selective neurons)
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14
Q

Simple vs. Complex

A
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15
Q

Simple cell

A
  • Orientation selective
  • Distinct on/off areas
  • Presumably constructed of collinear center-surround RF inputs
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16
Q

Complex cell

A
  • Orientation selective
  • On/off areas overlap
  • Presumably constructed from the summation of inputs from multiple simple cells preferring the same orientation
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17
Q

V1 Cortical Modules

A
  • Each cortical module is necessary and sufficient to analyze a particular point
  • Removal → blind spot in visual field
  • 2 pairs of ocular dominance columns (2 left columns and 2 right columns, in alternating order)
  • 2 complete samplings of all 180° of possible orientation columns
  • Also contain 16 cytochrome oxidase blobs
    ○ nonM-nonP RGCs → koniocellular layers of LGN → blobs in layers II and III
    ○ Many neurons color selective so potentially involved in analysis of object color
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18
Q

Cytochrome oxidase blobs

A

Potentially invovled in analysis of object color

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19
Q

Summary: Types of Processing

A
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20
Q

Ocular dominance columns/binocularity is for ___

A

Depth perception (stereoscopic)

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21
Q

Direction selectivity is for ___

A

Motor perception

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22
Q

Orientation selectivity is for ___

A

Form perception

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23
Q

Cytochrome oxidase blobs are for ___

A

Color perception/processing

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24
Q

Dorsal Stream: “Where”

A
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25
Q

Ventral Stream: “What”

A
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26
Q

Reminder: Parallel Processing Streams

A
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27
Q

Final Points and Thoughts on Perception…

A

● There is a hierarchy of visual information from occipital lobe to parietal
and temporal lobes → processing gets more specialized
● Neurons tend to be broadly tuned (broad sensitivity) → addresses
biggest weakness of narrow tuning (resistance to cell death)
● Implications for consciousness (visual perception without visual input)
○ Imagining object may activate same neurons that encode seeing
that object
○ Visual attention exemplified by binocular rivalry (each eye
receives different sensory info → alternate between perceived
images)
● **Note: Many of these topics are developing areas of research and
have not been definitively proven!

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28
Q

I am a neurologist, presented with a patient who is having difficulty seeing continuous motion. She claims that her entire visual world is experienced in choppy “frames”. What type of lesion might be causing her deficits? What is her clinical diagnosis?

A

Dorsal stream deficits (ex. Magnocellular LGN, area MT/MST), akinetopsia

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29
Q

I have a neuron, located somewhere along the visual pathway (but before the diencephalon). When I shine light in the center of this neuron’s RF, it causes depolarization and firing of an AP. What might the identity of my neuron be?

A

ON-RGC. We know that ON-bipolar cells and ON-RGCs will depolarize to
light in their RFs. However, only ON-RGCs fire APs! Since the question asked about
neurons before the diencephalon, thalamic neurons would not be a correct
answer.

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30
Q

I am performing single-cell electrophysiology to record from a
neuron in V1. I find that when I present a candy bar, oriented horizontally to the
neuron, it fires at maximum frequency. What could I do to achieve minimal
firing? What RF property is this neuron demonstrating?

A

Rotate the bar 90 degrees (perpendicular/vertical). The neuron is
exhibiting orientation selectivity.

31
Q

I’ve somehow managed to record from my friend’s brain without her knowing. I decide to show her some beautiful (and very colorful) artwork. What areas of cortex would I expect to be active?

A

V1, V4

32
Q

What areas are associated with the dorsal (where) stream?

A
  • Area V5/MT
  • Area SMT
33
Q

Damage to the dorsal stream can produce ___

A

Akinetopsia (like living in a stop-motion film)

34
Q

What areas are associated with the ventral (what) stream?

A
  • Area V4: color and orientation selectivity
  • Area IT: faces, other objects of biological significance
35
Q

Damage to area V4 can lead to ___

A

Achromatopsia (difficulty perceiving color in the absence of damaged cones, LGN, or V1)

36
Q

Face perception

A
  • Fusiform face area in fusiform gyrus most responsive to faces
  • Damage can lead to prosopagnosia (inability to recognize faces)
37
Q

Where does input to the LGN come from?

A
  • 20% from retina
  • 80% from V1
38
Q

Location of LGN

A

Thalamus

39
Q

The layers of the LGN are numbered 1 to 6 from ___ to ___

A

Ventral to dorsal

40
Q

What is the most ventral layer of the LGN?

A

1

41
Q

What is the most dorsal layer of the LGN?

A

6

42
Q

Where do layers 1 and 2 of the LGN get input from?

A

Magno cells (biggest, 1&2 also biggest so sink to the bottom)

43
Q

Where do layers 3, 4, and 5 of the LGN get input from?

A

Parvo cells

44
Q

Where do koniocellular layers of the LGN (K1-K6) get input from?

A

nonM-nonP cells

45
Q

Damage to which portion of the visual system is most closely associated with akinetopsia?

A

Area V5

46
Q

What distinguishes orientation and direction selective cells in area V1?

a) Direction selective cells are more common
b) Direction selective cells are a subset of the orientation selective cells
c) Direction selective cells are involved in form perception but orientation selective cells are
not
d) Direction selective cells are more common in parvo layers and orientation selective cells
are more common in magno layers

A

b) Direction selective cells are a subset of the orientation selective cells

47
Q

What is the relationship between orientation and direction selective cells?

A

Direction selective cells are a subset of orientation selective cells

48
Q

Which of the following would justify classifying a V1 neuron as direction selective

a) the cell responds to stimuli of biological significance that move in any direction
b) the cell responds to a stimulus moving leftward but not rightward
c) the cell responds to a bar of light moving down but not to the right
d) the cell is located in layer 4c beta

A

b) the cell responds to a stimulus moving leftward but not rightward

49
Q

Magnocellular retinal ganglion cells project to neurons in other brain structures in a way that
is distinct from other ganglion cells. Magno cells dominate in all the following structures
EXCEPT

a) LGN layer 1
b) V1 layer 4c alpha
c) V1 layers 2/3
d) area V5

A

c) V1 layers 2/3

50
Q

Penny the tiny unicorn is going to medical school and her (ethically dubious) assignment is to lesion the left LGN in a way such that all neurons receiving input from parvo ganglion cells in the left eye are destroyed. What layers must be lesioned to do this?

a) 2 and 3
b) 4 and 6
c) 1 and 6
d) 3 and 5

A

d) 3 and 5

51
Q

An area of the brain that has been reported to contain neurons particularly responsive to
images of faces is

a) IT
b) MT
c) AT
d) V5

A

a) IT

52
Q

All the following V1 layers receive direct input from the LGN EXCEPT

a) 2/3
b) 4B
c) 4c alpha
d) 4c beta

A

b) 4B

53
Q

Does area 4B receive direct input from the LGN?

A

Naur

54
Q

In which layer of primary visual cortex would you find the largest percentage of neurons with
large monocular center surround receptive fields that are not selective for color?

a) 2
b) 3
c) 4c alpha
d) 4c beta

A

c) 4C alpha

55
Q

Perception of some visual attributes appears to be based on a distributed code and the relative
activation of neurons with different preferences. This appears to be true for all the following
attributes EXCEPT

a) Color
b) Direction of motion
c) Light level
d) Orientation

A

c) Light level

56
Q

The primary direct target of axons from the konio layers of the LGN is which layer of primary
visual cortex?

a) Layer 2/3
b) Layer 4B
c) Layer 4C alpha
d) Layer 4C beta

A

a) Layer 2/3

57
Q

A stroke can cause blindness restricted to the upper right hemifield if it occurs
where:

a) Right parietal lobe
b) Left parietal lobe
c) Right temporal lobe
d) Left temporal lobe

A

d) Left temporal lobe

58
Q

The following statements about cytochrome oxidase blobs are all correct EXCEPT

a) They are centered on ocular dominance columns/stripes
b) A portion of their input comes from layer 4C beta
c) The neurons in blobs are less metabolically active than neurons in the interblob areas
d) They appear to play a special role in color perception

A

c) The neurons in blobs are less metabolically active than neurons in the interblob areas

59
Q

All the following statements about retinotopy are correct EXCEPT

a) The coverage factor in V1 is less than 1
b) Each cone in the retina influences neurons in roughly the same size area in V1
c) Nearby neurons in the LGN project to neighboring areas in V1
d) The totality of the cones in the fovea influence the firing of more V1 neurons than the
totality of cones from an equivalently sized part of the peripheral retina

A

a) The coverage factor in V1 is less than 1

60
Q

Orientation selectivity is least commonly seen in which layer of V1

a) layer 2 interblob areas
b) layer 4c
c) layer 5
d) layer 6

A

b) layer 4c

Orientation selectivity refers to the ability of neurons to respond preferentially to edges or bars of light at specific orientations. In the primary visual cortex (V1), orientation-selective cells are predominantly found in layers outside of layer 4C.

61
Q

Ocular dominance columns in area V1 are thought to be involved in

a) depth perception
b) motion perception
c) color perception
d) form perception

A

a) depth perception

62
Q

The majority of the input to layer 6 of the LGN comes from

a) layer 5 of primary visual cortex
b) layer 6 of primary visual cortex
c) the ipsilateral eye
d) the contralateral eye

A

b) layer 6 of primary visual cortex

63
Q

Which structure in the visual system contains cytochrome oxidase blobs

a) retina
b) LGN
c) V1
d) V2

A

c) V1

64
Q

Neurons in layer 4B of primary visual cortex send axons to visual areas in the parietal lobe.
Which type of LGN input goes into V1 layer 4B?

a) Konio
b) Magno
c) NonM-NonP
d) Parvo

A

b) Magno

Layer 4B of the primary visual cortex (V1) is associated with processing motion and spatial information. The magnocellular (Magno) pathway from the lateral geniculate nucleus (LGN) is specialized for these functions, making it the primary input that influences neurons in layer 4B.

65
Q

Layer 4B of the primary visual cortex (V1) is associated with processing ___

A

Motion and spatial information

66
Q

All the following statements about the human LGN are true EXCEPT

a) its activity is different in sleep vs wakefulness
b) its activity is influenced by visual attention
c) it contains both monocular and binocular neurons
d) it contains both color-sensitive and color-insensitive neurons

A

c) it contains both monocular and binocular neurons

The LGN primarily contains monocular neurons that respond to input from one eye at a time. Binocular neurons (which respond to input from both eyes simultaneously) are mainly found in the primary visual cortex (V1), not the LGN.

67
Q

V1 layers 4c alpha and 4b project to specialized motion-sensitive areas in which lobe of the
brain

a) temporal
b) parietal
c) frontal
d) occipital

A

b) Parietal

Dorsal stream

68
Q

Layer 4B output

A

M output to dorsal (parietal) visual areas (remember 4B gets M input)

69
Q

Layers 2&3 output

A

M, P, K output to central (temporal) visual areas (remember 2&3 get input from M, P, K)

70
Q

Layer 5 output

A

Superior colliculus (eye movement)

71
Q

Layer 6 output

A

LGN

72
Q

Layer 4C of V1

A

-Receives direct input from LGN
-RFs are similar to LGN RFs:
- Monocular input from ipsi or contralateral eye
- Center/surround antagonistic RFs

73
Q

Blob pathway

A

nonM-nonP cells in retina –> koniocellular layers of LGN –> cytochrome oxidase blobs in layers 2 and 3 –> occipital, temporal lobes (=ventral)

for analysis of color

74
Q

The term ocular dominance refers to which of the following observations

a) Neurons in alternating layers of area V1 are connected to the left or right eye
b) There are patches of neurons in layer 2 of V1 that respond to only the left eye and there is
a sharp boundary between these and neurons in neighboring patches that respond to only
the right eye
c) Neurons extending from the pia to the white matter in V1 tend to respond more strongly
to stimuli in one eye or the other
d) There are bands of neurons across the layers of the LGN that are connected to the left or
right eye

A

c) Neurons extending from the pia to the white matter in V1 tend to respond more strongly

A Intro to Neuro (17 decks)

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