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Phys Psyc I > Ch 3: neuronal plasticity > Flashcards

Ch 3: neuronal plasticity Flashcards

1
Q

Why did researchers choose to study Aplysia?

A
  • because this animal has a relatively small number of very large neurons
  • they can exhibit behaviours that can be modified with experience
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2
Q

name the reflex which is mostly studied in aplysia

A

the gill withdrawal reflex

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3
Q

briefly outline classical (pavlonian) conditioning

A 
Before conditioning:
Food=unconditioned stimulus
salivation=unconditioned response
After conditioning:
Bell=conditioned stimulus
salivation=conditioned response
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4
Q

When aplysia is relaxed, the __ and ___ are visible from above

A

siphon and gills

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5
Q

When the siphon is touched, what happens?

A

the siphon and gills are withdrawn and covered by protective flaps to protect them from rough seas or predators

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6
Q

describe sensitization of the gill withdrawal reflex

A

When an aplysia receives a noxious stimulus, the gill withdrawal reflex is potentiated (strengthened).
Subsequent light touch on the siphon now causes the gill to be withdrawn for much longer than before.
Animal becomes “sensitized” to future threats after experiencing the noxious stimulus.

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7
Q

Why is response longer due to sensitization of the gill withdrawal reflex? (physiologically)

A
  • the behavioural sensitization causes a slight increase in the duration of the APs that sensory neurons generate in response to touching the siphon
  • longer APs causes greater Ca2+ influx into PRESYNAPTIC TERMINAL
  • this increases the release of GLUTAMATE that is released onto the motor neuron
  • this increases the amplitude of the EPSPs in the motor neuron by more than 100%
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8
Q

blocking ___ receptors on sensory neurons activated by noxious stimulation of the skin prevents ability of noxious stimuli to induce sensitization

A

serotonin

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9
Q

Role of serotonin in sensitization

A
  1. serotonin binds to G protein-coupled serotonin receptor on the sensory neuron
  2. this activates adenylate cyclase, which synthesizes cAMP from ATP
  3. increased [intracellular cAMP] activates protein kinase A (PKA), which phosphorylates voltage-gated K+ channels in the neuronal membrane, lowering their probability of being open.
  4. Closed K+ channels reduces K+ influx during falling phase of AP, making repolarization take longer.
  5. broadening of AP increases Ca2+ influx into the axon terminal and boosts NT release

DURATION OF AP INCREASES AS A RESULT OF SEROTONIN

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10
Q

what sort of experimental manipulation could you do that would prevent short-term sensitization in Aplysia?

A

apply serotonin receptor blocker

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11
Q

threshold for response has been ____ in sensitization

A

lowered

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12
Q

The role of CREB in long-term sensitization

A
  • repeated noxious stimulation leads to repeated release of serotonin.
  • as a result, levels of activated PKA rise and some of the activated PKA enters the sensory neuron’s nucleus, where it phosphorylates CREB (transcription factor)
  • phosphorylated CREB binds to CRE sequences , causing it to interact with nearby RNA polymerases
  • RNA polymerases transcribe the downstream gene
  • transcribed mRNAs are translated into proteins and shipped from the nucleus to other parts of the neuron.
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13
Q

CREB is necessary for the induction of ___ ___ ____

A

long-term sensitization

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14
Q

When a motor neuron endured tetanic stimulation, what was observed when responded to a single stimulus half a minute later?

A

half a minute later, the motor neuron’s response to a single stimulus is much LARGER than it had been before the tetanic stimulation.
POST-TETANIC POTENTIATION.

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15
Q

post-tetanic potentiation results mainly from:

A

a buildup of Ca2+ in the presynaptic terminal

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16
Q

major function of the hippocampus in rodents is ___ ___

A

spatial memory

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17
Q

lesion to the ___ causes humans to become unable to form new episodic memories

A

hippocampus

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18
Q

hippocampal LTP

A

-when axons of the perforant path (which project from the neocortex to the dentate gyrus in the hippocampus) were stimulated, the amplitude of the EPSPs in the dentate gyrus increases by more than 100%

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19
Q

simplified Hebb’s rule

A

neurons that fire together wire together

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20
Q

Hebb’s rule predicts that LTP should be observed only when…

A

presynaptic stimulation is accompanied by postsynaptic stimulation

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21
Q

Does the removal of the hippocampus take away the ability of an animal to be classically conditioned?

A

no

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22
Q

The hippocampus receives its major input from layers __ and ___ of the ____ ____

A

the hippocampus receives its major input from layers 2 and 3 of the ENTORHINAL CORTEX (EC)

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23
Q

The hippocampus outputs to layer __ of the ____ ____

A

the hippocampus outputs to layer 5 of the ENTORHINAL CORTEX (EC)

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24
Q

Hippocampal slice preparation

A
  • researchers dissect the brain out of a deeply anesthetized animal and sliced it into slabs.
  • slabs were bathed in highly oxygenated solution to keep neurons alive for many hours
  • stimulating and recording electrodes can be placed more easily in slices than in vivo
  • drugs can be added to view their effects
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25
Q

briefly explain the circuit for classical conditioning (e.g., in a rabbit with puff air in eye)

A
  • rabbits have a third eyelid which closes when air is puffed in their eye
  • experimenters play a tone and then puff eye, causing blink
  • rabbit is classically conditioned to blink at tone
  • MUST BE AN INDIRECT CONNECTION BETWEEN THE EAR AND THE EYE
  • SYNAPSES ARE STRENGTHENED BY THE SIMULTANEOUS ACTIVATION OF AUDITORY AND SOMATOSENSORY SYNAPSES
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26
Q

AP5 2-amino-5phosphonopentanoate is a drug that blocks ____ ____

A

NMDA receptors

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27
Q

what is a dendritic spike?

A

an AP which occurs in the dendrite of some types of pyramidal cells

28
Q

AMPA receptor

A

an ionotropic glutamate receptor that controls a sodium channel; when open, it produces EPSPs

29
Q

CaM-KII

A

type II calcium-calmodulin kinase

  • an enzyme that must be activated by Ca2+
  • may play a role in the establishment of LTP
30
Q

Mechanism of LTP Induction (triggering)

A
  1. as the postsynaptic cell membrane is depolarized, the magnesium block in the NMDA receptor is removed and the NMDA channel opens in response to glutamate
  2. binding of glutamate causes influx of calcium and sodium ions
  3. postsynaptic calcium binds with calmodulin, generatnig a calcium/calmodulin complex which activates calcium/calmodulin kinase II (CaMKII)
  4. activation of CamKII promotes insertion of additional AMPA receptors into the postsynaptic membrane. Also phosphorylates AMPA receptors, which increases rate of ion flow.

POSTSYNAPTIC CELL BECOMES MORE RESPONSIVE TO PRESYNAPTIC GLUTAMATE

31
Q

Mechanism of LTP stabilization

A

Dendritic protein synthesis:

  • ribosomes which translate mRNA into protein are located inside the dendrites (in or near the spines) of hippocampal neurons.
  • Proteins involved: CaMKII and ARC
  • activity-related cytoskeleta protein (ARC) expression increases due to stron postsynaptic activity. Newly transcribed Arc mRNA is shipped from the nuceus into the dendrites, where it is translated
32
Q

LTP _____ involves the activation of CaMKII, which then boosts AMPA receptor number and ion flow in the activated synapses

A

LTP INDUCTION involves the activation of CaMKII, which then boosts AMPA receptor number and ion flow in the activated synapses

33
Q

Synaptic tagging hypothesis

A

synapses that were active during a postsynaptic depolarization can be marked with a molecular synaptic tag that is recognizable by newly synthesized proteins. These go to work selectively at those tagged synapses.

34
Q

LTP ____ requires protein synthesis

A

LTP STABILIZATION requires protein synthesis

35
Q

How can LTP be destabilized?

A
  • by zeta inhibitory peptide (ZIP).
  • When ZIP is applied to potentiated synapses, SYNAPTIC STRENGTHS RETURN TO THEIR PRESTIMULATED LEVELS OF STRENGTH.
  • likely inhibits PKM-zeta enzyme which enhances synaptic transmission through AMPA receptors
36
Q

give an example of how synaptic strength can be increased by presynaptic changes and one by postsynaptic changes

A
  • presynaptic: more NTs released per AP

- postsynaptic: more glutamate receptors

37
Q

Why is it important that Matsuzaki et al. in their spine growth experiment bathed the hippocampal slice in a magnesium-free solution?

A

Removing Magnesium allows the released glutamate to bind to NMDA receptors even at low membrane pot’s

38
Q

blocking protein synthesis with emetine blocks LTP ____ but not its ____

A

blocking protein synthesis with emetine blocks LTP STABILIZATION but not its INDUCTION

39
Q

what is the name of the phenomenon in which synapses are being weakened for many hours after certain patterns of presynaptic stimulation?

A

long-term depression (LTD)

40
Q

basic function of the cerebellum

A

fine-tunes movements (and some cognitive processes) by learning from errors and then adjusting its output accordingly

41
Q

the cerebellum contains some very large neurons called ____ _____, and a greater number of small neurons called ____ ____ _____

A

the cerebellum contains some very large neurons called PURKINJE CELLS, and a greater number of small neurons called CEREBELLUM GRANULE CELLS.

42
Q

axons of granule cells are called:

A

parallel fibers

43
Q

fiber which wraps itself around the Purkinje cell dendrites is called:

A

climbing fiber

44
Q

What occurs when the climbing fiber fires an AP?

A

it releases glutamate, the Purkinje cell becomes STRONGLY depolarized and fires its own AP

45
Q

What occurs when glutamate is released from parallel fibers?

A

-synapses between Purkinje fibers and parallel fibers are WEAK, therefore glu evokes small postsynatic depolarizations that only trigger APs if several fibers fire at once

46
Q

what causes the parallel fiber input to decrease in strength?

A

activation of parallel and climbing fiber inputs SIMULTANEOUSLY, and doing so REPEATEDLY

47
Q

Mechanism of LTD

A
  • NMDA receptors in the climbing fiber synapses and voltage-gated calcium channels allow for influx of calcium
  • parallel fibers DO NOT contain NMDA receptors. Activation of their METABOTROPIC GLUTAMATE RECEPTORS causes IP3 cascade which leads to release of Ca2+ from intracellular organelles.
  • coincident activation of both parallel and climbing fibers together cause sharp increase in postsynaptic Ca2+, which triggers persistent activation of protein kinase C.
  • Protein kinase C removes AMPA receptors from the postsynaptic side of the synapse.

REMOVAL OF AMPA RECEPTORS WEAKENS SYNAPSE

48
Q

some synapses exhibit ___ if postsynaptic activity follows presynaptic activity and ___ if postsynaptic activity precedes presynaptic activity. (spike timing-dependent activity)

A

some synapses exhibit LTP if postsynaptic activity follows presynaptic activity and LTD if postsynaptic activity precedes presynaptic activity.

49
Q

what does it mean for synaptic pasticity to be “anti-Hebbian?”

A

cells that fire together should become less strongly interconnected, as occurs in LTDs

50
Q

Synaptic scaling refers to…

A

Neurons STRENGTHEN their synaptic inputs when they’ve been relatively INACTIVE,
and WEAKEN them when they have been very ACTIVE.

51
Q

EPSC stands for:

A

excitatory postsynaptic current

52
Q

tetrodoxin

A

a drug that blocks voltage-gated sodium channels

53
Q

EPSC vs EPSP

A

EPSC measures current rather than membrane voltage

54
Q

bicuculine

A

blocks GABA receptors and therefore increases neuronal firing rates

55
Q

neurons in cultures with tetrodoxin displayed ___ EPSCs and neurons in cultures with bicuculine displayed _____ EPSCs

A

neurons in cultures with tetrodoxin displayed LARGER EPSCs and neurons in cultures with bicuculine displayed REDUCED EPSCs

56
Q

spiny neurons that control singing in songbirds ____ their rate of spine turnover when young birds learn to sing. This indicates that…

A

spiny neurons that control singing in songbirds REDUCE their rate of spine turnover when young birds learn to sing. This indicates that THE ACT OF LEARNING INVOLVES STABILIZATION OF NEWLY FORMED SPINES.

57
Q

T/F:eye-blink conditioning in mice causes new axon branches to sprout from new synapses

A

true

58
Q

explain axon sprouting during blink conditioning experiment

A

Axon tracers were used to visualize axons that project from the pons to the deep cerebellar nuclei.
-projections were more extensive in eye-blink conditioned mice than in pseudoconditioned or untrained mice.

59
Q

What is a tonotopic map?

A

the sound frequency to which cortical neurons respond most strongly varies systematically across the auditory cortex, creating a tonotopic map, which is PLASTIC

60
Q

learning-related plasticity in the auditory cortex of rats experiment:

A
  • thirsty rats were trained to press a bar for water whenever they heard a 6kHz tone.
  • Experimenters compared stimulus preferences of neurons in the primary auditory cortex of trained and untrained rats.
  • They found the cortical territory containing neurons tuned to 6kHz had EXPANDED IN TRAINED RATS and the territory dedicated to high frequencies had SHRUNK.
61
Q

what does a cortical motor map show?

A

a cortical motor map shows which neurons are involved in which movement

62
Q

describe the experiment in which rat training altered MOTOR CORTEX MAP

A

-adult rats were trained to reach through a hole and grasp a slowly moving pellet (skilled task)
-other group was trained to push a lever for food (unskilled task)
-experimenters used electrical microstimulation to map the MOTOR CORTEX in both groups
-they found that forelimb’s wrist and toes representation were larger in skilled group than in the unskilled group
-they also found that areas devoted to elbow and shoulder movement diminished
EXPANSION OF TERRITORY INVOLVED IN CONTROLLING THE LEARNED MOVEMENT AT THE EXPENSE OF OTHER AREAS

63
Q

a paraplegic woman learned to control a robotic arm using a ___ ____ ____

A

a paraplegic woman learned to control a robotic arm using a BRAIN-MACHINE INTERFACE

64
Q

Brain-machine interfaces use a decoder to ___ the subject’s intended movements and translates them into ____ that move the robot arm

A

Brain-machine interfaces use a decoder to INFER the subject’s intended movements and translates them into COMMAND that move the robot arm

65
Q

Why do researchers ask subjects who are paralyzed to imagine moving a robotic arm?

A

because neural activity during imagined movements correlates with activity during actual movements.
Researchers can use these correlations to construct the decoder.

66
Q

Total brain and cerebral cortex mass are ___ in rats that grew up in enriched environments

A

INCREASED

67
Q

what does the effect of environmental enrichment have on cortical neuron density and synapse density?

A

environmental enrichment DECREASES cortical neuron density WITHOUT CHANGING synapse density.
THE NUMBER OF SYNAPSES PER NEURON IS THUS INCREASED.

Phys Psyc I (8 decks)

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