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neuroscience > Central Visual Processing I > Flashcards

Central Visual Processing I Flashcards

1
Q

In the visual system as you go from the retina to V1 to V2 to V4 and the temporal cortex….what happens to the receptive fields?

A

The receptive fields get larger because higher order visual processing requires integration and analysis over greater and greater regions of space

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2
Q

What is the most important target of the retinal ganglion cells for visual perception?

A

The retino-geniculo-striate pathway

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3
Q

Where does the reticulo-geniculo striate pathway end?

A

The primary visual cortex (area 17, striate cortex, or V1)

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4
Q

What is the reticulo-geniculo striate pathway responsible for?

A

Form, color, and depth vision, visual motion perception, visual object recognition and localization

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5
Q

What is a second important target of the retina?

A

superior colliculus

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6
Q

What is the pathway from the retina to the superior colliculis responsible for?

A

Eye movements and head/ attentional orientation

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7
Q

What is retinotopy?

A

A faithful spatial representation of visual space/ position

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8
Q

How is intensity/ luminance visual information transduced, processed, and represented?

A

Photons absorbed/ transduced by photo-pigments, rods vs cones

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9
Q

How is differential spectral absorption transduced, processed and represented?

A

3 cone types (color opponency

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10
Q

How is spatial contrast transduced, processed and represented?

A

Center-surround receptive fields (edge detection)

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11
Q

Due to the optics of the eye, what happens to visual field mapping onto the retina?

A

Visual field mapping onto the retina is inverted and flipped

Ex: The superior nasal visual field maps to inferior (central) temporal retina

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12
Q

How do retinal ganglion cell axons leave the eye?

A

Optice nerve

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13
Q

Do nasal or temporalhemiretinal axons cross the optic chiasm?

A

Nasal! Temporal do not cross.

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14
Q

At which levels are the visual field representations crossed?

A

At the level of the optic tract, LGN and cortex

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15
Q

How is the LGN organized?

A

It is organized into 6 layers that presevers eye of origin

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16
Q

Going from layer 1 to layer 6….what is the contra/ ipsa order of the layers?

A

Contral, ipsa, ipsa, contra, ipsa, contra

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17
Q

How does the LGN provide input to V1?

A

The LGN creates the optic radiation to V1

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18
Q

What is the primary layer in the striate cortex (V1) that the LGN projects to?

A

Layer 4

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19
Q

Is the input to V1 segregated in an eye-specific and retinotopic manner?

A

Yes it is!

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20
Q

What is the basis for the occular dominance columns of V1?

A

The segregation of eye specific input into V1

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21
Q

When does eye specific information being to combine?

A

It beings to combine and interact within the circuitry of V1

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22
Q

How are retinal receptive fields constrcucted?

A

They are constructed by retinal circuitry and are center-surround of two signs, sometimes with differing cone types in center vs surround (the creates a color opponent cell)

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23
Q

What are the two Center-surround receptive fields in the retina?

A

On-center and OFF- center

24
Q

What are the receptor systems that vision is divided into in the retina?

A

Rods and 3 classes of cones (R-long, G- medium, B- short)

25
Q

What are the signaling pathways that vision is divided into in the retina?

A

Parvo pathwya, Magno pathway, Konio pathway

26
Q

Where is the origin of the M, P ad K pathways?

A

The retina

27
Q

What is the Magno system specialized for?

A

High temporal resolution (speed) and higher contrast gain, and possibly motion perception

28
Q

What is the Parvo pathway specialized for?

A

Emphasizes higher visual acuity and color

29
Q

What is the Konion system specialized for?

A

Color perception

30
Q

How many M layers are in the LGN? How many P layers?

A

M layers= 2

P layers= 4

31
Q

How are K layers presented in the LGN?

A

They are in between (intercalated) the 6 layers if the LGN

32
Q

Which visual field, Ipsilateral or contralateral, does the LGN recieve visual input from?

A

Contralateral

33
Q

What layer of V1 does the LGN receive feedback from?

A

Layer 6 of V1

34
Q

Describe the cells of the LGN?

A

Center-surround receptive fields

35
Q

What happens to the M, P, and K pathways when they get to the visual cortex?

A

They intermix substantially….excpet the M pathway is partially segregated in the outputs of V1 and in higher visual cortex

36
Q

In V1, what is the most cortex devoted to?

A

More cortex is devoted to central vision

37
Q

Describe the anatomical structure of V1:

A

It is 2 mm thick sheet of cells, it has 6 layers

38
Q

Where does output from V1 come from?

A

Output from V1 comes from layers 2 and 3 (and then goes to extrastriate cortex (V2)

39
Q

What does layer 5 of the V1 do?

A

It does to the superior colliculus

40
Q

What is ocular dominance in regards to V1 neurons?

A

Eye preference— the cells of V1 receive input primarily from one eye

41
Q

What is a binocular V1 neuron?

A

A neuron that receives input from both eyes

42
Q

How can the ocular dominance property of a single neuron be predicted?

A

It can be predicted if you know where the cell is located relative to the pattern of the ocular dominance columns

43
Q

Do V1 neurons have center-surround receptive fields?

A

No they USUALLY do not have center-surround…rather they have oriented receptive fields and are orientation tuned.

Some are center-surrond receptive fields and are color-selective (color opponent)

44
Q

What does orientation tuning refer to?

A

It refers to the preference of a cell to be stimulated by an edge of light presented at a particular angle (horizontal, vertical or inbetween)

45
Q

Why does V1 want to created oriented cells?

A

Orientation tuning is the early stage of form vision analysis. The visual system needs to determine within a visual scene what objects and what is background. The borders can be thought of as edges of differing orientation

46
Q

What are the two color opponent signals that are created in the retina and propagated into V1?

A

Red vs Green and Blue vs Yellow

47
Q

Functionally, how is V1 organized?

A

It is columnar in organization. Each column has similar receptive field properties

48
Q

How do ocular dominance columns alternate in V1?

A

They alternate between left eye and right eye

49
Q

What are blobs in V1?

A

CO (cytochrome oxidase) blobs are centered on the OD columns and contain monocular, unoriented color cells

50
Q

What is a hypercolumn?

A

A hypercolumn is a collection of functional cortical columns that cover the entire range of possible values of one stimulus parameter for a given point in visual space

51
Q

Where are hypercolumns found?

A

They are found in V1

52
Q

What are the two major visual processing streams after V2?

A

The dorsal pathway and the ventral pathway

53
Q

Where does the dorsal pathway go and what does it do?

A

The parietal visual cortex—- it is most concerned with motion perception and the localization of visual objects

Where pathway

54
Q

Where does the ventral pathway go and what does it do?

A

The temporal visual cortex and is concerned with object and pattern recognition

What pathway

55
Q

Is V2 retinotopically organized?

A

Yes, it is and it has larger receptive fields than V2

56
Q

What do V2 stripes suggest?

A

They suggest a separation of the visual processing for form, color, motion and depth

neuroscience (33 decks)

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