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BSC Zoology - Neuroscience > Lecture 7- Vision II: Central processing > Flashcards

Lecture 7- Vision II: Central processing Flashcards

1
Q

What are the characteristics of the M ganglion cells?

A

-magnocellular=large cells -large receptive fields -make up about 10% of ganglion cells -motion detection, flicker and analysis of gross features -can tell if sth is moving or not, not good at fine detail

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2
Q

What are the characteristics of the P ganglion cells?

A

-parvocellular= small cells -more numerous (about 80% of ganglion cells) -provide fine detail (visual acuity) and colour vision

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3
Q

What is this picture showing?

A

-this pic shows the AP of a P ganglion cels as reacting to different frequencies of light -one ganglion cell, it responds best to one wavaelength= black it is important for carrying info for colour

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4
Q

What is the output region of the ganglion cells?

A

-many brain regions -mainly the lateral geniculate nucleus (LGN) in the thalamus

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5
Q

What is the visual pathway?

A
  1. Retina
  2. Optic nerve
  3. LGN
  4. Optical radiations
  5. Visual cortex
    - starts in the retina= the axons of optic nerve then synapse with the thalamus (LGN), then the LGN neurons have optic radiations (white matter) goes all the way back to the visual cortex V1
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6
Q

Where is the optic chiasm and what happens there?

A
  • lies at the base of the brain, anterior to the pituitary
  • the fibres from right and left optic nerves combine to form the optic chasm
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7
Q

What fibres cross at the optic chiasm?

A

-nasal

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8
Q

What hemisphere is the right visual field “viewed” by?

A

-left

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9
Q

What hemisphere is the left visual field “viewed” by?

A

-right

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10
Q

Explain:

A

-the nasal fibres cross over -get information from both eyes in each hemisphere -partial crossing of the visual field

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11
Q

How many layers are there in the LGN?

A

-6 -contain 2 typesof cells

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12
Q

What layers do the magnocellular cells and the parvocellular cells occupy in the LGN?

A

-6 layers -Magno=1 and 2 (one layer for info from each eye) -Parvo =3,4,5,6= two of these for info from each eye

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13
Q

What cells in the LGN do the the P and M ganglion cells target?

A

P ganglion= parvocellular cells M ganglion= magnocellular cells

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14
Q

What is the function of the thalamus?

A

-functional relay station for sensory information -except for taste!

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15
Q

Is the visual information separated or mixed in the LGN?

A

-separated, keep M and P streams of information separate, and information from each of the eyes is also kept separate

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16
Q

What are the optic radiations?

A
  • the axons of the magnocellular and parvocellular LGN neurons carrying information to the visual cortex
  • white matter, big, enclose the ventricles
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17
Q

Where do the LGN neurons project to?

A

-the primary visual cortex

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18
Q

Where is the primary visual cortex located?

A

-occipital lobe, around the calcarine fissure (gap) -very far back in the brain -if you cut corpus callosum medially= then there

19
Q

What does it mean that V1 is retinotopic?

A

-whatever the retina sees= the brain will see= retinotopic map= the neurons in V1 will see the same things as the retina sees –Neighbouring cells within the retina project to neighbouring cells in the LGN & Vis Cortex.

20
Q

Where is each of the visual fields (left/right) represented in the primary visual cortex?

A

-on the contralateral visual cortex -right field of vision= left V1 -left field of vision= right V1

21
Q

Does each V1 separate which part of the visual field is presented where?

A
  • yes
  • central part of vision is on the outermost part of the V1
  • more peripheral part of the visual field is closer to the midline
22
Q

What part of vision is the most vulnerable?

A

-central -closest to the outside in the V1

23
Q

How many layers does the visual cortex have?

A

6

24
Q

What layer of the V1 do LGN neurons input to?

A

4C -P= to layer 4Cbeta -M= to layer 4Calpha

25
Q

How are cortical (V1) neurons orientation selective?

A

-neurons respond best to bars moving in particular orientation

26
Q

What are orientation columns in the V1?

A
  • the cortex is extremely ordered
  • in each little area the neurons in all 6 layers will respond to the same direction of the bar of light
  • part of the way the information is divided into different bits
27
Q

What does this picture demonstrate?

A
  • each of the four pics= how different spots in the V1 will see it
  • deconstructing what we see
  • then brain has to put back together
28
Q

What are occular dominance columns?

A
  • input from the LGN in the V1 segregated into small regions called occular dominance columns
  • section 4C
  • infromation from the left eye is thus still separated from the right eye
  • it goes: right, left, righ, left…
29
Q

What is the pathway of the P ganglion cells?

A

-feed into the parvocellular LGN cells, then via optic radiations (their axons) to the V1 into the 4C beta layer

30
Q

What is the pathway of the M ganglion cells?

A

-feed into the magnocellular LGN cells, then via optic radiations (their axons) to the the V1 into the 4C alpha layer

31
Q

Where does the mixing of visual information occur?

A

in the layer 4B and 3

32
Q

What happens to the visual information after V1?

A
  • divided into two large cortical streams
  • DORSAL pathway
  • VENTRAL pathway
33
Q

What does the dorsal pathway do?

A

-the where -where in the visual field something is

34
Q

What does the ventral pathway do?

A

-the what -what am I seeing? part of information

35
Q

What is the MT area?

A

-part of the dorsal stream -middle temporal (MT) lobe is an area specialised for processing of object motion

36
Q

Where does the MT receive information from?

A

-receives retinotopic information from a number of cortical areas (V2 and V3) -receives input from cells in layer 4B of the V1 (so the M type GCs and LGN)

37
Q

What does the visual system operate on?

A

-about comparison = what is the colour next to – red vs green – blue vs yellow =imprtant comparison -context of the colour

38
Q

What parts are part of the ventral stream?

A

V1, V2, V4

39
Q

Where does the V4 receive input from?

A

-the blob and interblob regions of the primary visual cortex via V2

40
Q

What are the receptive fields like in V4 and what is V4 for?

A

-large -both orientation selective and colour selective -important for perception of shape and colour

41
Q

What is the area IT?

A
  • inferior temporal
  • major output area of V4 -neurons respond to a wide variety of abstract shapes and colours
  • important for visual memory and perception
  • important for perception of faces
  • when see faces= neurons stimulated -the information from the whole pathway is added up here
42
Q

What was wrong with David?

A

-David cannot recognize faces, can tell people only by what their voices are like -think motion perception is off -at the periphery of his vision= can’t see -couldn’t recognize the prime minister on a photo -lesion affecting the fusiform gyrus (area IT) -also caused a visual field defect, must have been back of the chiasm as the effect is the same in each eye

43
Q

What was wrong with Giselle?

A

-cars appear out of nowhere, pouring coffee very difficult= appears frozen until cup overflows -visual acuity and colour vision norma -visual fields= normal -lesion in the MT -she had a tiny stroke in her middle temporal lobe= area spcialised for processing motion

44
Q

What are the blob and interblob regions?

A
  • areas of 4C beta of V1 (so Parvocellular cells feed into here)
  • blob= colour info
  • interblob receive the same infor bur react to diretcion of colour

BSC Zoology - Neuroscience (35 decks)

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