chapter 23

Question 1

what extends from the growth cone to guide the developing axon toward its proper destination

Answer 1

filopodia

Question 2

the entire nervous system develops from the..

Answer 2

ectoderm

Question 3

once a cell commits to a type of glial cell, will it be able to divide again

Answer 3

no

Question 4

trimester and neron development

Answer 4

1st-neurogenesis
2nd-migration
3rd-differentiation

Question 5

how do pioneer axons find their target in the developing human brain

Answer 5

other neurons give chemical signals, either chemoattractents or chemorepellents

Question 6

ocular dominance

Answer 6

binocular organization of the cortex

Question 7

monocular deprivation

Answer 7

one eyelid is sealed closed shortly after birth

open eye columns expand in width while closed eye columns shrink

Question 8

how is monocular deprivation reversed

Answer 8

closing the previously opened and opening the previously closed-this is called reversed occulusion

Question 9

critical period for ocular dominance

Answer 9

last until 6 weeks of age

Question 10

what does the establishment of binocular receptive fields depend on

Answer 10

correlated patterns of activity that arise from the two eyes as a consequence of vision

Question 11

binocular vision

Answer 11

vision using two eyes with overlapping fields of view, allowing good perception of depth.

Question 12

types of vergence

Answer 12

convergence and divergence

Question 13

convergence

Answer 13

coordinated contraction of both medial rectus muscles brings both eyes toward the midline (ie, the nose)

Question 14

divergence

Answer 14

coordinated contraction of both lateral rectus muscles brings both eyes toward the periphery

Question 15

our vision vs rats vision

Answer 15

our vision is convergent, so we have good depth perception. rats eyes are divergent so it can see further behind

Question 16

where can ocular dominance shifts occur

Answer 16

in all mammals that have binocular vision

Question 17

binocular competition

Answer 17

inputs from two eyes actively compete for synaptic control of post synaptic neuron

if activity of two eyes is correlated and equal in strength, the two inputs will be retained on the same cortical cell

if balance is disrupted by depriving one eye, the more active input will somehow displace the deprived synapses or cause them to be less effective

Question 18

ocular dominance columns

Answer 18

are stripes of neurons in the visual cortex of certain mammals (including humans) that respond preferentially to input from one eye or the other

Question 19

is visually driven retinal activity sufficient for modifications of binocularity?

Answer 19

no, it requires for one to pay attention to visual stimuli and use vision to guide behavior

ex-if animal is kept anesthetized, even though cortical neurons respond briskly, synaptic plasticity requires the release of “enabling factors” that are linked to behavioral state such as attention

Question 20

rules for synaptic placticity

Answer 20

neurons that fire together wire together

neurons that fire out of sink lose their link

Question 21

what does it mean by neurons that fire together wire together

Answer 21

if presynaptic neuron is active and postsynaptic neuron is strongly active under the influence of other inputs, the dynapse of the presynaptic anxon is strengthened

Question 22

what does it mean when neurons that fire out of sync lose their link

Answer 22

when presynaptic axon is active and post synaptic neuron is weakly activated by other inputs the synapsed formed by the presynaptic axon is weakened

Question 23

optic chiasm

Answer 23

visual signals from the left hemifields of both eyes are sent to the right hemisphere of the brain, while the signals from the right hemifields of both eyes are sent to the left hemisphere of the brain

Question 24

So each hemisphere of the brain is responsible for processing the visual information in…

Answer 24

opposite visual field from both eyes

Question 25

in the lgn, axons from eyes are sorted out again, how are they sorted

Answer 25

by ganglion cell type

by eye of origin (ipsilateral or contralateral

retinotopic position

Question 26

neural progenerators

Answer 26

dividing cells