central visual pathways

Question 1

visual pathway from retina to cortex

Answer 1

retina –> thalamus (LGN) –> visual cortex

Question 2

how does the brain get visual signals

Answer 2

the retina transmits

Question 3

synaptic transduciton through retina

Answer 3

photoreceptors detect photons –> bipolar cells –> ganglion cells

Question 4

what is the output neuron of the retina

Answer 4

ganglion cells

Question 5

projections of the visual field onto retina

Answer 5

projects backwards and upside down

brain has to flip back

Question 6

binocular field of view

Answer 6

left visual hemi-field is “seen” by right visual cortex

• projection of binocular field of view relates to crossing of fibers in otptic chiasm
• visual signals from each retina cross over

Question 7

thalamus

Answer 7

inputs from 2 eyes are relayed to visual cortex via dorso-lateral geniculate nucleus

Question 8

how are inoputs from 2 eyes segregated

Answer 8

cell specific manner in each layer of LGN in primates/humans
- maintains organization even at thalamus
(contra/nasal: 1,4,6 and ipsi/temporal: 2,3,5)

Question 9

layers of thalamus

Answer 9

magnocellular: 1,2
parvocellular: 3,4,5,6
contralateral: 1.4.6
ipsilateral: 2,3,5

Question 10

mouse LGN inputs

Answer 10

infected with AAV to back trace inputs to thalamus

- different types of neurons all tend to come from same visual area

Question 11

optic radiations course to visual cortex

Answer 11

lateral geniculate nucleus –> meyers loop: superior and inferior retinal quadrants

Question 12

retinotopic organization in right occipital lobe

Answer 12

top of visual cortex to inferior visual field (superior retina)
- no integration of both eyes in V1
overrepresentation of inputs from fovea- high density of photoreceptors

Question 13

layer 4 of visual cortex (unsure)

Answer 13

magno, parvo and konicellular pathways remain seperated

in layer 4 of visual cortex

Question 14

columnar organization of ocular dominance

Answer 14

as you move across cortex there are specific columns of neurons that respond only to left or right alternating
- inputs from l/r eye are still segregated in layer 4

Question 15

primary visual cortex neurons

Answer 15

neurons in V1 respond only to oriented edges

• have different orientation preferences
• fire most at certain length and orientation

Question 16

organization of V1: orderly progression of columnar response

Answer 16

IV: left ear/ right eye (ocular dominance columns)
blobs
orientation columns

Question 17

how are orientation units formed

Answer 17

LGN cells: linear alignment with overlapping receptive field responds best to bar extend over fields
summed output from LGN cells each with center surround organizations results in orientation selectivity
–> V1 cell

Question 18

outputs of striate cortex

Answer 18

1,2,3,4a: extrastriate cortex

5: superior colliculus
6: LGN
inputs: mostly layer 4

Question 19

extra striate cortical areas

Answer 19

IT: inferior temporal cortex
receives input through cascade, complicated visual info
MT: maintaining retinal stability

Question 20

what do neurons in higher visual areas respond best to

Answer 20

synthesize random images and record neuorn, see what neuron responds best to adn combine images and mutate and test again til you get evolving image to see if it iis better or not until you get best stimulus
- neurons can represent high order features

Question 21

neural network

Answer 21

algorithms that take inputs (image) and represent using fewer but higher order features of it by filtering image in diff ways and assignming weights to filters so you have fewer features but they are more imformative
- each layer gets more abstract