Primary visual (v1) cortex: location & organisation

Question 1

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

Answer 1

conscious visual perception

Question 2

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

Answer 2

the apex

Question 3

list the steps of the primary visual pathway

Answer 3

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

Question 4

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

Answer 4

optic radiations

Question 5

what do the optic radiations make neural connection with

Answer 5

the primary visual area in the occipital lobe

Question 6

where is the occipital lobe located within the cerebral cortex

Answer 6

the back end

Question 7

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

Answer 7

6

Question 8

which layer in the primary visual cortex has subdivisions

Answer 8

layer 4

Question 9

what are the names of the subdivisions of layer 4 called

Answer 9

• 4a
• 4b
• 4c alpha
• 4c beta

Question 10

which of the layers is wide

Answer 10

layer 4

Question 11

why is layer 4 in the primary visual cortex particularly wide

Answer 11

due to its 3 major subdivisions

Question 12

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

Answer 12

vertical/columnar

Question 13

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

Answer 13

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

Question 14

what is the primary visual v1 cortex also known as

Answer 14

• area 17

- striate cortex

Question 15

which visual hemifield does the primary visual v1 cortex represent

Answer 15

opposite

Question 16

what does unilateral damage of the primary visual v1 cortex cause

Answer 16

hemianopia

loss of vision or blind in opposite half of visual field

Question 17

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

Answer 17

left v1 damaged = right hemianopia

Question 18

which two lobes does the calcarine sulcus divide

Answer 18

parietal lobe from the occipital lobe

Question 19

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

Answer 19

90 degrees

Question 20

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

Answer 20

grey matter

Question 21

describe the structure of the calcarine sulcus

Answer 21

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

Question 22

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

Answer 22

its cellular organisation

Question 23

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

Answer 23

• 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

Question 24

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

Answer 24

• 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

Question 25

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

Answer 25

the stria of gennari

Question 26

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

Answer 26

granule cells

Question 27

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

Answer 27

pyramidal cells

Question 28

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

Answer 28

layer one

Question 29

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

Answer 29

2-6

Question 30

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

Answer 30

dendrite & axons synaptic connections

Question 31

which surface is layer 1 found just below of

Answer 31

pial surface

Question 32

how intense is layer 1 of the v1 cortex and why

Answer 32

pale | due to no neurons or cell bodies found within this layer

Question 33

which layer has the deepest intensity under the microscope and why

Answer 33

layer 4c | due to highest density of neurons and cell bodies and stellate cells

Question 34

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

Answer 34

LGN

Question 35

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

Answer 35

layers above 2-4b & below 5-6

Question 36

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

Answer 36

2mm x 2mm

Question 37

what do stellate cells form in layer 4c

Answer 37

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

Question 38

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

Answer 38

no longer than layer 4c

Question 39

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

Answer 39

vertically (axons go up & down)

Question 40

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

Answer 40

pyramidal cells

Question 41

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

Answer 41

fat vertical | going up

Question 42

what sort of circuit do pyramidal cell neurons have

Answer 42

not a local circuit neuron but is large projection neurons

Question 43

where do the axons of pyramidal cells do

Answer 43

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

Question 44

how are the local cortical circuits organised

Answer 44

mainly in vertical columns

Question 45

why are the local circuits organised in vertical columns

Answer 45

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

Question 46

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

Answer 46

LGN

Question 47

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

Answer 47

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

Question 48

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

Answer 48

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

Question 49

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

Answer 49

glutamate

Question 50

which v1 cortical cells are inhibitory

Answer 50

basket cells & chandelier cells

Question 51

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

Answer 51

GABA

Question 52

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

Answer 52

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

Question 53

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

Answer 53

18

Question 54

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

Answer 54

18

Question 55

which brodmann area is the myelinated stria only found in

Answer 55

17

Question 56

which brodmann area is the calcarine sulcus fundus

Answer 56

17

Question 57

what is the U bend

Answer 57

where the grey matter is continuous

Question 58

what is the name of the U bend of grey matter

Answer 58

fundus of calcarine sulcus

Question 59

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

Answer 59

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

Question 60

what layers does the stria of gennari straddle along

Answer 60

4c alpha & 4b

Question 61

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

Answer 61

- 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

Question 62

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

Answer 62

- 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

Question 63

what is the name of the cytochrome rich cells

Answer 63

the cytochrome oxidase blobs

Question 64

what is the name of the cytochrome poor cells

Answer 64

the inter blob cells which contains less cytochrome oxidase

Question 65

which layer is uniformly cytochrome oxidase rich

Answer 65

4c

Question 66

where are there columns rich of cytochrome oxidase

Answer 66

above and below layer 4c

Question 67

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

Answer 67

blobs

Question 68

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

Answer 68

interblobs (surrounded by blobs)

Question 69

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

Answer 69

blood vessels

Question 70

what are the neurons in the blobs

Answer 70

``` colour selective (interested in chromatic sensitivity placed in their RFs) ```

Question 71

what are the neurons in the inter blobs

Answer 71

``` contour selective (interested in responding to different lines and edges/form processing) ```

Question 72

what property do inter blobs have

Answer 72

orientation selectivity

Question 73

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

Answer 73

- 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)

Question 74

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

Answer 74

- 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)

Question 75

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

Answer 75

- 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)

Question 76

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

Answer 76

direction selectivity

Question 77

what is direction selectivity of layer 4b involved in

Answer 77

motion pathway

Question 78

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

Answer 78

to contribute to form processing