Visual 2

Question 1

Simple cells

respond to ____

receptive fields created from ____

shape of receptive field

Answer 1

respond to more complex stim and receptive fields than ganglion cells

receptive field created from converging LGN neruon with center-surround field in layer 4

shape = straight line, orientation important !!!

Question 2

hierarchical processing for simple cells

what does that mean?

Answer 2

many similar cells spatially offset receptive field converge on higher order cell to create new receptive field

Question 3

complex cells

difference from simple cells?

major input?

Answer 3

simple cells = require line/edge in visual field

complex cells = line or edge can be anywhere within receptive field (like when lines/edge move across field)

input = convergance of several simple cells with position offset (any simple cell can fire complex cell)

created by simple cells up and down hypercolumn

Question 4

simple cell best stim by?

Answer 4

line of light covering all ON areas without affecting OFF

diffuse light = useless

position and orientation of light crucial

Question 5

input to simple cell?

Answer 5

convergance of cells in LGN thalamus in layer 4

Question 6

cells in V1 are organized how?

each of which corresponds to ?

Answer 6

organized in array of hypercolumns

each corresponds to point in retina

Question 7

each column in hypercolumn responds to ____

major cell in hypercolumn

Answer 7

responds to particularly orientation
adjacent columns = adjacent retinal locations

blob cells receive input from parvo cells of LGN for color processing

Question 8

structure of microcolumn within hypercolumn

how many layers

LGN axons terminate where?

what are the 2 parts in each hypercolumn

Answer 8

layer 1 = surface of brain
layer 6 = border of white matter

LGN axon terminate in layer 4 to form simple cell

contralateral, ipsilateral ocular dominance columns

Question 9

inputs to layer 4 of primary visual cortex from 6 layers of LGN remain ___

what part of hypercolumn is binocular

orientations of lines in visual field correspond to what in hypercolumn

all cells in vertical column share what?

Answer 9

completely segregated according to eye of origin (ipsi or contralat)

upper 4 layers are binocular

orientation of lines in visual field = different rays radiating from central blobs

same column = sensitive to same orientation

Question 10

what does it mean by sensitive period in development of cortex

Answer 10

connections can be altered by visual experience

for humans = 2-3 years
for kittens = 3 months, synapss max sensitive to deprivation at 4-6 weeks

longer period of monocular deprivation, less connections

Question 11

if one eye closed for 3-6 days and then reopene does the cortex recover

Answer 11

no it does not, connections once lost are gone

Question 12

one week of moncular deprivation in infants can cause __

Answer 12

amblyopia = reduced acuity

depends on cell studied (retina before cortical) and differs for receptive field property

Question 13

meaning of ocular dominance

Answer 13

ocular dominance = meausre of relative synaptic input of a cell from each eye

Question 14

7 categories of ocular dominance
category 1 cells driven by ___

category 4 driven by ___

category 7 drive by ____

Answer 14

category 1 = driven by cell contralateral to cortical cell

category 4 = driven equal by both eyes

category 7 = driven by cell ipsila tto cortical cell

1 and 7 = monocularly driven
all others = binocular of varying eye pref

Question 15

describe monocular deprivation
experiments

results?

Answer 15

if one eye suture closed, blind in that eye but ganglion cells and LGN still work

= cortical blindness so all cortical cells respond to eye still open = PERMANENT

no changes in adult

“use it or lose it” “disuse atrophy”

Question 16

binocular deprivation experiments

results?

Answer 16

if both eyes closed, primary cortex normal (more non-responsive cells but most binocular and still functional)

behaviorally blind = higher order visual cells disrupted

competition btwn converging synaptic inputs from 2 eyes not disuse atrophy

Question 17

alternating monocular deprivation

Answer 17

if one eye deprived and then reopened no cortical cells can be driven by deprived eye

but if other eye then depressed, reopened eye recovers

shows competition, active suppression by active eys from converging inputs

Question 18

conditions under which effects of abnormal developmental experiments can be reversed

Answer 18

congenital strabismus or cataracts still have normal vision if repaired soon

if not repair by 2 years old, permanent deficit

Question 19

another way to treat kid with cataract in one eye?

Answer 19

put patch on still functional eye to restore competitive balance between two eyes

Question 20

output of hypercolumn goes where?

Answer 20

output = layer 3 and 6 to higher cortical areas