Primary visual (v1) cortex: location & organisation Flashcards Preview

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Flashcards in Primary visual (v1) cortex: location & organisation Deck (78)
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1
Q

what does the v1 area of brain allow for us to have

A

conscious visual perception

2
Q

where is the primary visual cortex located in relation to the primary visual pathway

A

the apex

3
Q

list the steps of the primary visual pathway

A
  • retinal ganglion cells
  • optic nerve, chiasm, tract
  • lateral geniculate nucleus
  • optic radiations
  • primary v1 cortex
4
Q

what do the neurons of the LGN travel out of in the primary visual pathway

A

optic radiations

5
Q

what do the optic radiations make neural connection with

A

the primary visual area in the occipital lobe

6
Q

where is the occipital lobe located within the cerebral cortex

A

the back end

7
Q

how many layers of cells does the primary visual v1 cortex consist of

A

6

8
Q

which layer in the primary visual cortex has subdivisions

A

layer 4

9
Q

what are the names of the subdivisions of layer 4 called

A
  • 4a
  • 4b
  • 4c alpha
  • 4c beta
10
Q

which of the layers is wide

A

layer 4

11
Q

why is layer 4 in the primary visual cortex particularly wide

A

due to its 3 major subdivisions

12
Q

in which orientation are the intra-cortical connections of the primary visual cortex

A

vertical/columnar

13
Q

where is the primary visual v1 cortex located in the occipital lobe

A

mainly medial, upper & lower banks of the calcimine sulcus in each hemisphere

14
Q

what is the primary visual v1 cortex also known as

A
  • area 17

- striate cortex

15
Q

which visual hemifield does the primary visual v1 cortex represent

A

opposite

16
Q

what does unilateral damage of the primary visual v1 cortex cause

A

hemianopia

loss of vision or blind in opposite half of visual field

17
Q

give an example of the outcome of unilateral damage of the primary visual v1 cortex

A

left v1 damaged = right hemianopia

18
Q

which two lobes does the calcarine sulcus divide

A

parietal lobe from the occipital lobe

19
Q

at what angle is the calcimine sulcus to the parieto-occipital sulcus

A

90 degrees

20
Q

which matter is the calcarine sulcus found above & below the primary visual area

A

grey matter

21
Q

describe the structure of the calcarine sulcus

A

it is not a slit, but more like a U-bend with cortical tissue in its depth (is a continuous structure) called a fundus

22
Q

what is a cyto-architecture referred to of a particular region

A

its cellular organisation

23
Q

list the cellular organisation of brodmann area 17 that is in common with all other areas of the cerebral cortex

A
  • has 6 separate layers of cells in the gray matter (few in layer 1)
  • small granule or stellate (star shape) cells concentrated in layer 4
  • receives direct input from the thalamus (LGN) & has direct communication with pyramidal cells in the layer directly above and below to continue processing of the visual image
24
Q

list the cellular organisation of brodmann area 17 that is unique which is found nowhere else in the cerebral cortex

A
  • layer 4 is very wide (1/3 of cortical thickness) & has 3 separate sub-layers (A, B, C)
  • with sublayers 4a & 4b containing pyramidal and not granule cells
  • layer 4c with granule cells having separate upper (alpha) and lower (beta) sub-layers
  • layer 4b contains a band or stripe of myelinated axons
25
Q

what is the name of the band/stripe of myelinated axons located in layer 4b

A

the stria of gennari

26
Q

what do sub-layers 4a and 4b not contain

A

granule cells

27
Q

what do sub-layers 4a and 4b only contain

A

pyramidal cells

28
Q

out of the 6 layers within the grey matter, which layer does not contain cell bodies of cortical neurons

A

layer one

29
Q

which layers out of the 6 in the primary visual cortex contains cell bodies of cortical neurons

A

2-6

30
Q

what does layer 1 out of the 6 contain in the primary visual cortex

A

dendrite & axons synaptic connections

31
Q

which surface is layer 1 found just below of

A

pial surface

32
Q

how intense is layer 1 of the v1 cortex and why

A

pale

due to no neurons or cell bodies found within this layer

33
Q

which layer has the deepest intensity under the microscope and why

A

layer 4c

due to highest density of neurons and cell bodies and stellate cells

34
Q

what does layer 4c alpha and 4c beta receive input from

A

LGN

35
Q

in which layers does layer 4c alpha and 4c beta connect to cells of

A

layers above 2-4b
&
below 5-6

36
Q

how wide and tall is the grey matter of the cerebral cortex

A

2mm x 2mm

37
Q

what do stellate cells form in layer 4c

A

small ‘local circuit’ neurons, which relay information they receive from the LGN via short axons to pyramidal cells in the layers just above or below them

38
Q

how short are the dendrites of stellate cells in layer 4c

A

no longer than layer 4c

39
Q

which orientation do the axons of stellate cells in layer 4c travel

A

vertically (axons go up & down)

40
Q

what do the vertical axons of stellate cells in layer 4c connect to

A

pyramidal cells

41
Q

what sort of dendrites do pyramidal cells have and which direction do they go

A

fat vertical

going up

42
Q

what sort of circuit do pyramidal cell neurons have

A

not a local circuit neuron but is large projection neurons

43
Q

where do the axons of pyramidal cells do

A

they do not stay in v1 but will go to different locations/distant targets via long axons

44
Q

how are the local cortical circuits organised

A

mainly in vertical columns

45
Q

why are the local circuits organised in vertical columns

A

because granule cell axons run mainly vertically across the layers to make excitatory synapses on the prominent vertically-oriented (primary) dendrites & dendritic spines of all pyramidal cells

46
Q

which input to granule/stellate cells in layer 4c receive

A

LGN

47
Q

what do pyramidal cells in layers 2-4b connect to

A

other nearby extra striate (beyond striate cortex) areas of visual association cortex which are other areas of the cerebral cortex

48
Q

what sort of connections do pyramidal cells below layer 4c have

A

descending sub cortical connections eg layer 5 not to the LGN but to the superior colliculus (which is lower down) and layer 6 supplies excitatory connections back to the LGN which supplies the input

49
Q

what do pyramidal and granule/stellate cells use as their neurotransmitter

A

glutamate

50
Q

which v1 cortical cells are inhibitory

A

basket cells
&
chandelier cells

51
Q

what are the neurotransmitters of the inhibitory cells of the v1 cortical cells

A

GABA

52
Q

what are the inhibitory cells of the v1 cortical cells involved with

A

lateral GABA-ergic inhibitory processes that also influences the RF properties of nearby pyramidal cells

53
Q

which brodmann area is found on the upper bank of the medial calcarine sulcus

A

18

54
Q

which brodmann area is found on the lower bank of the medial calcarine sulcus

A

18

55
Q

which brodmann area is the myelinated stria only found in

A

17

56
Q

which brodmann area is the calcarine sulcus fundus

A

17

57
Q

what is the U bend

A

where the grey matter is continuous

58
Q

what is the name of the U bend of grey matter

A

fundus of calcarine sulcus

59
Q

what does the striate cortex only found in v1 area 17 contain

A

has a continuous band of myelinated axons (white matter) running in grey matter of the calcarine sulcus

60
Q

what layers does the stria of gennari straddle along

A

4c alpha & 4b

61
Q

list the chemical organisation of area v1 that is in common with all other areas in the cerebral cortex

A
  • neurons in all cell layers of v1 have mitochondria
  • which contain the metabolic enzyme cytochrome oxidase (CO) (& found in all mitochondria of body & all neurons of body have this)
  • can be visualised with special staining techniques
62
Q

list the properties of the pattern of cytochrome oxidase activity which is found nowhere else in the cortex apart from v1

A
  • columns of intensely CO stained cells in layers 2-4b & weaker in layers 5-6
  • apporox 0.25mm wide
  • separated by columns of less CO stained cells in these layers of width
  • view horizontally across the layers, the CO-rich cells form a regular polka dot arrangement across whole of v1
  • with polka dot to dot centre spacing of ~0.5mm
63
Q

what is the name of the cytochrome rich cells

A

the cytochrome oxidase blobs

64
Q

what is the name of the cytochrome poor cells

A

the inter blob cells which contains less cytochrome oxidase

65
Q

which layer is uniformly cytochrome oxidase rich

A

4c

66
Q

where are there columns rich of cytochrome oxidase

A

above and below layer 4c

67
Q

when viewing layer 3 of primary v1 cortex under a microscope, what do the dark dots represent

A

blobs

68
Q

when viewing layer 3 of primary v1 cortex under a microscope, what do the lighter patches represent

A

interblobs (surrounded by blobs)

69
Q

when viewing layer 3 of primary v1 cortex under a microscope, what do the holes represent

A

blood vessels

70
Q

what are the neurons in the blobs

A
colour selective 
(interested in chromatic sensitivity placed in their RFs)
71
Q

what are the neurons in the inter blobs

A
contour selective 
(interested in responding to different lines and edges/form processing)
72
Q

what property do inter blobs have

A

orientation selectivity

73
Q

list the series of connections which start by the midget ganglion cells of the retina

A
  • midget ganglion cell axons connect to the parvo cellular layer 3-6 of the LGN
  • which go through the parvo cell pathway & make connections with the 4c beta granule cells
  • which provide inputs for
    1. blob cells (involved in red green colour processing)
    2. inter blob cells (involved in form processing)
74
Q

list the series of connections which start by the parasol/magno ganglion cells of the retina

A
  • parasol ganglion cell axons connect to the mango cellular layer 1 & 2 of the LGN
  • which go through the magno cell pathway & make connections with the 4c alpha granule cells
  • which provide inputs for
    1. inter blob cells (involved in form processing)
    2. layer 4b (contours and direction in space)
75
Q

list the series of connections which start by the small bi-stratified ganglion cells of the retina

A
  • small bi-stratified cell axons connect to the koniocellular layers of the LGN
  • which go through the konio cell pathway & provide direct inputs for the blob cells (involved wavelength selective blue yellow processing which is different to other blobs)
76
Q

what is the properties of contours & direction in space where a contour is moving in layer 4b called

A

direction selectivity

77
Q

what is direction selectivity of layer 4b involved in

A

motion pathway

78
Q

why do 4c alpha granule cells also make connections with inter blob cells as well as 4c beta cells

A

to contribute to form processing