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Flashcards in Central Visual Processing II Lec13 Deck (47)
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1
Q

Synaptic plasticity is the ability of a
synapse between two neurons to
change in ___ or ___

A

strength or effectiveness.

2
Q

. Input from the LGN into V1 maintain ___ segregation and setup the OD columns in V1

A

monocular

3
Q

Visual deprivation and
competition study

1 is a cell
that is completely dominated by ____ eye
input

A

contralateral

4
Q

Visual deprivation and
competition study

 

, 7 is dominated by the ___ eye

A

ipsilateral

5
Q

Visual deprivation and
competition study

 

__
is a binocular cell equally driven by either eye. 

A

4

6
Q

Visual deprivation and


competition

In the normal adult primate, how many 1,7,4s are there?

A

equal numbers of cells driven by each eye (i.e. the
numbers of cells with OD=1,2,3 about equal cells
with OD=5,6,7),

7
Q

Experiment: monocular deprivation (MD)
- One eyelid is sutured soon after birth and it
remains closed for 6 months 

 

after opening eyelid

what was the distribution of the OD scale?

A

all were either 1s or 7s meaning 

t nearly all cells are driven by the eye that wasn’t
sutured close

8
Q

Experiment: monocular deprivation (MD)
- One eyelid is sutured soon after birth and it
remains closed for 6 months and then open

all cells designated 1s and 7s

 

was this change permanent?

A

yes

9
Q

Experiment: monocular deprivation (MD)
- One eyelid is sutured soon after birth and it
remains closed for 6 months and then open

all cells designated 1s and 7s

 

where in the brain were there changes?

A

in V1 itself, not in the retina, because
the eye, retina, LGN, optic radiations, etc were found
all to be normal.

10
Q

what condition resutls from monocular deprivation

(all cells driven by eye that wasn't sutured closed?)

A

amblyopia.

11
Q

Intravitreal injection in one eye, of 3H-proline in a v1 monocular deprived and a v1 normal monkey

what changes were noticed in the cortex?

A

- Under monocular deprivation, the “good” eye (non-deprived) has taken over the territory normally
occupied by the other (occluded, deprived) eye

12
Q

Normal OD columns exhibit a roughly equal ___ of
bands for each of the two eyes

A

width

13
Q

Normal OD columns exhibit a roughly equal width of
bands for each of the two eyes, whereas in monocular deprivation, the deprived eye bands are much
___

A

thinner 

14
Q

critical period in humans

A

birth and 6-8 years 

 

s (in a kitten, 6 months in a monkey, 6-8 years in a
human child).

15
Q

A few ___ of deprivation
can permanently altered the development of the OD
columns during the critical period 

A

days

16
Q

The effects of a brief period of monocular deprivation
may be partially reversed if, 

A

during critical period

1. sutured eye is opened

2. nonsutured eye is sutured

* allows it to regain its cortical territory

17
Q

- Binocular deprivation (BD) during the critical period
seems to ___ the critical period somewhat

A

lengthen

18
Q

- The binocular deprivation experiments show that the
effects of MD are not simply the result of “disuse”, but
instead indicate an

A

 active competition

19
Q

strabismus, as a
___ disorder

A

peripheral

20
Q

 amblyopia, as a ___
disorder. 

A

central

21
Q

Strabismus invovles the

A

extracocualr muscles

22
Q

strabismus is caused by a a misalignment of the two

eyes preventing

A

proper binocular vision

23
Q

what can strbismus lead to if occuring in the young

A

ambylopia

24
Q

Amblyopia: (lazy eye), a central disorder resulting from
 

A

an imbalance or lack of visual coordination between the
two eyes during development

25
Q

Amblyopia deficits include

A

poor vision or acuity in one eye

compared to the stronger eye

26
Q

causes of Amblyopia: include

A

1. strabismus

2. refractive errors

3. cataracts

27
Q

Amblyopia is Characterized

by an abnormal development of connections in the ___

A

visual cortex

28
Q

what eye does a patch go on in ambyopia? what can be a side effect? 

A

on good eye

can cause poor bionuclar depth (stereopsis)

29
Q

- Normal development requires both a match in strength of input from each eye AND a 

A

coordination of
inputs

30
Q

r alternation of two strong eyes, or amblyopia (one weak eye) USUALLY LEADS TO 

A

poor stereopsis (depth vision) 

31
Q

Proper binocular visual development requires

A

 1. the proper convergence of the two eyes

2. matching
refraction and image quality

32
Q

injection of 3h proline in one eye in adult reveals

A

ocular domiannce in v1

33
Q

injection of 3h proline in one eye in the fetus reveals

A

no ocular dominance columns

34
Q

strabismus in an adult can lead to

A

diplopia

35
Q

Hebb’s hypothesis:

A

 “Cells that fire together
wire together”

36
Q

 
Experiments establishing, activity-based, Hebbian competition include:

A

1. diff. between bincoular deprivation and monocular deprivation

2. TTX silence retinal output supress MD

3. GABA application silencing cortical cells supress MD

4.  Artificial electrical stimulation of the optic nerves after TTX injection in the eyes, synchronous or

asynchronous 

37
Q

what two experiments supressed moncular depirivation

A

injections fo TTX silencing retinal ouput (ganglion cells)

GABA in cotex blocking cortical cells

38
Q

electrostim is applied synchronously to the two optic nerves, ___ OD columns form. 

A

no segregated OD columns form. 

39
Q

electrostim is applied asynchronously to the two optic nerves, ___ OD columns form. 

A

OD columns form

40
Q

___ of NMDA receptors reduce ocular dominance plasticity and the refinement of
receptive-field properties

A

Antagonists

41
Q

 The overall concentration of NMDA receptors in the visual cortex peaks with the 

A

critical period for
ocular dominance plasticity

42
Q

The NMDA contribution to the visual response drops in layers ___ as ocular dominance
columns segregate. 

A

4-6

43
Q

Examples of adult cortical plasticity: (4) 

A

1. recovery from brain injury

2. Rapid fill-in of the cortical representation after a retinal lesion, then axonal growth

3. - Analogous cortical reorganization of somatotopic maps under conditions of digit re-afferentation

4. phantum limb

44
Q

By depriving the sensory cortex of input what happened intially?

A

 was silent in the region
deprived of input.

45
Q

By depriving the sensory cortex of input what happened over time?

A

that cortical region
became active again, resulting in a shift in the
topographic maps

46
Q

. The input
deprived cortex had “stolen” input from __ cortex,
using the same mechanisms of competition and plasticity
seen in the developing brain.

A

adjacent

47
Q

activity in only one axon synapse may be insuffiecent to drive the post synaptic cell to threshold so it triggers ___ strengthening mechanism

A

hebbian