Lecture 17 - CNS Plasticity and Learning

Question 1

postnatal growth of the brain is guided by:

Answer 1

learning

Question 2

what is the critical period for visual cortex development in humans?

Answer 2

6 months - 3 years

Question 3

true or false: projections to the visual cortex are made randomly

Answer 3

false

Question 4

eye closure for a couple of days during the critical period induces:

Answer 4

movement of spines as part of synaptic plasticity (use it or lose it)

Question 5

act as the housekeepers of the nervous system by doing the actual synaptic pruning or enchantment

Answer 5

microglia with GABAb receptors

Question 6

GABA neurons adjust the level of activity and guides:

Answer 6

anatomical plasticity

Question 7

what is the effect of enhancing inhibitory GABA signalling on the critical period?

Answer 7

widens the critical period and increases plasticity

Question 8

synaptic stabilization contributes to termination of critical period, and this may be due to:

Answer 8

• myelination (and associated nogo myelin), which occurs at the end of the critical period
• development of the adult perineuronal net (PNN)
• reduction in growth potential of adult neurons, compared to neonatal neurons
• reductions in growth factors like BDNF and neuromodulators like noradrenaline

Question 9

what does “Nogo” do?

Answer 9

inhibits neuronal growth via axonal nogo receptors

Question 10

a web of proteoglycans (CSPG) that wrap around certain neurons, especially inhibitory neurons

Answer 10

the perineuronal net (PNN)

Question 11

the mature perineuronal net (PNN) inhibits ____ around GABA neurons

Answer 11

neuronal plasticity

Question 12

true or false: critical periods occur for all skills and vary in duration

Answer 12

true

Question 13

social deprivation in an orphanage increases:

Answer 13

cognitive dysfunction

Question 14

children without social interaction in the critical period have:

Answer 14

a less related frontal cortex

Question 15

critical period plasticity may be restored in adults by techniques used in:

Answer 15

spinal cord injury treatment

Question 16

list six potential treatments that can be used to restore critical-period plasticity

Answer 16

1) blocking myelin inhibition of growth
2) degrading the perineuronal net (PNN) with chondroitinase
3) transplantation of immature GABAergic neurons
4) increasing neuromodulators via antidepressants
5) training or enriched environment to increase BDNF
6) microglial-neuronal communication increases GABA neuron plasticity

Question 17

see slide 496

Answer 17

transplanted neurons woohoo

Question 18

what are the effects of an enriched environment on the cerebral cortex?

Answer 18

• increases cortical thickness
• increases the size of neurons
• increases the number of spines/synapses
• increases BDNF

Question 19

monocular deprivation results in:

Answer 19

enhanced somatosensory discrimination (other senses become heightened)

Question 20

how is it possible for enhanced somatosensory discrimination to occur in the presence of monocular deprivation?

Answer 20

due to microglia phagocytosing inhibitory inputs to the visual cortex, which enables greater responses to somatosensory stimulation

Question 21

____ strip off GABA inhibition to adapt to injury

Answer 21

microglia

Question 22

ture or false: it is possible for sensation in the phantom limb to be evoked from face simulation 4 weeks after an amputation and cortical remapping

Answer 22

true (unused brain areas get taken over by neighbouring regions)

Question 23

the _____ resists external distubances and can be readily studied in humans to examine plasticity and learning

Answer 23

monosynaptic stretch reflex (knee-jerk reaction)

Question 24

is the monosynaptic stretch reflex excitatory or inhibitory?

Answer 24

excitatory (EPSP)

Question 25

turns off antagonist motorneurons when making a movement

Answer 25

reciprocal inhibition

Question 26

turns off reflex pathways when not needed by GABAb receptors on the terminal of sensory afferents

Answer 26

presynaptic inhibition

Question 27

presynaptic inhibition allows learning of skilled movements by:

Answer 27

lowering unwanted reflexes and increasing sensation (ex: dancers or climbers)

Question 28

list the two major points of Nashner's experiment on the adaptation of postural stretch reflexes

Answer 28

- ankle extensor stretch reflexes reduce body sway if the foot is displaces horizontally --> the CNS augments the reflex in successive trials - the same reflexes increase body sway in a toe-up rotation about the ankle joint --> the CNS attenuates them in successive trials

Question 29

context-dependence and adaptation of reflexes may be controlled by:

Answer 29

the cerebellum and brainstem reticular formation

Question 30

postural muscles are often activated involuntarily prior to _____ in order to compensate for the expected shifts in the centre of gravity

Answer 30

voluntary movement of limbs

Question 31

delays in the stretch reflex can cause:

Answer 31

instability and tremor (especially in certain postures or with peripheral demyelination/spinal cord injury)

Question 32

review slides 501-505

Answer 32

decent diagrams

Question 33

with spinal cord injury, nerve injury, stroke, or cerbral palsy the reflex pathwyas are disrupted, leading to:

Answer 33

spasticity

Question 34

when reciprocal inhibition of muscles is reduced there is co-contraction of the muscles, leading to:

Answer 34

stiffness

Question 35

when presynaptic inhibition is reduced, this leads to:

Answer 35

exaggerated reflexes

Question 36

after injury, sensory terminal sprouting and microglia plasticity can increase reflexes by:

Answer 36

making inappropriate connections

Question 37

reduced reciprocal inhibition, reduced presynaptic inhibition, sensory terminal sprouting and microglia plasticity all lead to:

Answer 37

exaggerated reflexes and large reflex driven tremors (clonus)

Question 38

in motorneurons, intrinsic voltage-dependent persistent Na+ and Ca++ currents increase with injury, leading to:

Answer 38

sustained muscle spasms

Question 39

with inury, serotonin innervation of the spinal cord is ____, but 5-HT2 receptors on motorneurons become _____, which further augments _____

Answer 39

lost, constitutively active, spasms

Question 40

what are treatments for muscle spasticity and tremors?

Answer 40

GABA agonists, 5-HT antagonists, botox, surgery, rehab