Lecture 26

Question 1

the major retinal projection to the brain is the ____ pathway

Answer 1

retinogeniculostriate pathway

Question 2

where is the the striate cortex

Answer 2

very back of the brain

occipital lobe

Question 3

where does the visual signals from each eye split

Answer 3

optic chism

Question 4

how many LGN layers

Answer 4

6

Question 5

LGN receives info from

Answer 5

retina

Question 6

LGN is major relay site in the

Answer 6

thalamus

Question 7

what happens in LGN when sleeping

Answer 7

inhibition of inhibitory neurons

Question 8

parvocellular layer

Answer 8

small cell bodies

Question 9

magnocellular layer

Answer 9

large cell bodies

Question 10

koniocellular layer

Answer 10

very small cell bodies

Question 11

visual signal in LGN organized in ))))))

Answer 11

retinotopic maner

Question 12

retinoyopic organization

Answer 12

each layer on LGN receives info from 1 eye
maps complete half of the visual field
objects in right visual field activates all 6 layers of left LGN

Question 13

M ganglion cells

Answer 13

project from retina to magnocellular layer

for large, fast moving objects

Question 14

P ganglion cells

Answer 14

project from retina to parvocellular layer

for details of stationary objects

Question 15

retinal ganglions project to 3 other subcortical structeres …

Answer 15

• superior colliculus
• Pretectum and Edinger-Westphal nucleus
• Suprachiasmatic nucleus (SCN)

Question 16

superior colliculus

Answer 16

• RGCs form a retinotopic map in the SC
• SC integrates visual, auditory and somatosensory inputs and sends motor outputs to motor areas of the brainstem
• Controls saccades, rapid eye movements that orient fovea

Question 17

Pretectum and Edinger-Westphal nucleus

Answer 17

• Iris control: in too bright light/dim light conditions, send motor output back to eye via cranial nerve III to adjust pupil diameter
• Lens control: if image is out of focus, send motor output to ciliary muscle -> changes accommodation

Question 18

Suprachiasmatic nucleus (SCN)

Answer 18

• A special group of retinal ganglion cells is photosensitive (responds to ambient light levels)
• Project to SCN, which serves as the circadian clock that derives circadian rhythms
• SCN projects to pineal gland which produces the hormone melatonin in high levels of darkness

Question 19

how many layers of striate cortex

Answer 19

6

Question 20

layers 2 and 3 of striate cortex

Answer 20

mainly coordinate info with other visual cortical areas

Question 21

layer 4

Answer 21

thickest layer, 4A 4B 4C
most LGN fibers terminate in 4C
• Magnocellular axons project onto upper part of layer 4C
• Parvocellular axons project to lower part of layer 4C

Question 22

layers 5 and 6

Answer 22

mainly communicate with sumcortical structures (LGN, SC)

Question 23

Topographical mapping

Answer 23

adjacent regions of the visual fields are mapped onto adjacent areas in the V1

Question 24

Cortical magnification

Answer 24

visual map is distorted on the visual cortex, cortical representation of the fovea is greatly magnified compared with the cortical representation of peripheral vision

Question 25

is there a linear or non linear representation in V1

Answer 25

non linear

Question 26

why does foveal region gets more space in the V1

Answer 26

normally most important info is normally in the centre of our vision, and the greater density of retinal ganglion cells in the fovea

Question 27

Visual crowding in the periphery

Answer 27

Objects that can be easily identified in isolation but seem jumbled up when surrounded by other objects

Question 28

where to inputs from 2 eyes intermingle (binocular)

Answer 28

neurons above and below 4C

Question 29

what is the role of binocular neurons

Answer 29

to compare the image from each eyes which are slightly different, increase fine depth perception

Question 30

orientation selectivity

Answer 30

receptive fields that are bars will respond most when light aligned perfectly with excitatory area

Question 31

how are LN receptive fields made

Answer 31

LGN neurons feed into V1 neurons in a precise manned

Question 32

directional sensitivity

Answer 32

neuron shows significantly greater firing to stimulus movement in a particular direction

Question 33

colour contrast detection pathways ultimately lead to

Answer 33

blobs in V1

Question 34

cells in parvocellular pathway provide info on what colours

Answer 34

red and green

Question 35

cells in koniocellular pathway provide info on what colours

Answer 35

blue and yellow