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Neurobiology (3350) > Lecture 22 - Synaptic plasticity and Learning > Flashcards

Lecture 22 - Synaptic plasticity and Learning Flashcards

1
Q

Non-associative learning

A
  • when synaptic or neural function changes over times
  • Habituation - learning to ignore stimulation that lacks meaning
  • Sensitization - Learning to intensify response to stimuli. a response that is steady until some event occurs and causes a larger response
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2
Q

Associate learning

A
  • Learning to associate something to another through some repitition to have a novel response to stimuli
  • Classical conditioning - pair an unconditional stimulus with a conditional stimulus to get a conditioned response
  • instrumental conditioning - learn to associate a response with a meaningful stimulus
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3
Q

What are some Experimental advantages in using invertebrate nervous systems

A

– Small nervous systems
– Large neurons
– Identifiable neurons
– Identifiable circuits
– Simple genetics

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4
Q

Describe the experiment of the Nonassociative Learning in Aplysia (sea slug)

A
  • Researcher identified different reflexes and showed how they underwent changes.
  • the reflex is initiated by a water jet made on the siphon, which refracts the gill.
  • The retraction of the gill eventually went away (no more responses), therefore habituation
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5
Q

What did the experiment of the Nonassociative Learning in Aplysia (sea slug) find in relation to L7?

A
  • he found that habituation results from presynaptic modification at L7
  • Meaning that there were changes at the presynaptic neuron that lead to habituation
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6
Q

Explain Hebbian modifications

A

They refer to changes in synaptic strength due to synaptic activity and can be caused by things like increase in NT release, changes in NT receptor (number, function) or changes in dendritic spine size

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7
Q

What is L7

A

a motor neuron in a sea slug responsible for moving the gill

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8
Q

What did the experiment of the Nonassociative Learning in Aplysia (sea slug) find in relation to electrical stimulations?

A
  • Repeated electrical stimulation of a sensory neuron leads to a progressively smaller EPSP in the postsynaptic motor neuron
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9
Q

What happened after repeated stimulation in the associative Learning in Aplysia (sea slug) experiment in relation to NT?

A
  • there were decreases in neurotransmitter vesicle release with repeated stimulation of the siphon
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10
Q

Which other neuron did the associative Learning in Aplysia (sea slug) find

A

**neuron L29 **

  • L29 responds to eletrical stimuli to the head and releases serotonin
  • has an axoaxonic synapse at the same neuron as the sensory neuron on the siphon
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11
Q

Explain an example of sensitization in the associative Learning in Aplysia (sea slug) experiment

A

If you apply an electrical stimulation to the head, the reflex becomes stronger

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12
Q

Explain the mechanism for sensitization for the gill-withdrawal reflex

A
  1. When L29 receives an electrical stimulation (to the head), it releases serotonin on the sensory neuron leading to the activation of serotonergic receptors (G-protein) and of intracellular pathways
  2. Sensory synapse releases more NT whenever the syphon is sprayed (with water) causing depolarization
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13
Q

What is the Cerebellum important for?

A
  • Important site for motor learning
  • compares what were trying to do and what were actually doing
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14
Q

Which cells do motor commands come from?

A

Purkinje cells

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15
Q

Purkinje cells receive input from where?

A
  • parallel fibers - what were trying to do
  • climbing fibers - what is actually happening
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16
Q

How to induce Long-term depression (LTD) in the cerebellar cortex?

A
  • Put a pair of electrodes (1 on parallel fibers & other on climbing fibers)
  • Every minute, stimulate parallel fiber and see postsynaptic response (mostly stead). At time zero, stimulate strongly the climbing fibers and then restart stimulating the parallel fibers
  • Findings - response stays reduced for a long time after on parallel fibers
17
Q

The Mechanisms of cerebellar LTD is due to what?

A

Rise in [Ca2+]i and [Na+]i and the activation of protein kinase C

18
Q

mechanism of LTD induction in the cerebellum.

A
  1. Activation of climbing fiber
  2. Strong depolarization of Purkinje cell dendrite
  3. activation of voltage-gated Ca channels
  4. Parallel fiber activation leads to Na entry through AMPA receptors
  5. Generation of diacylglycerol (DAG) via stimulation of the metabotropic receptor.
  6. DAG activates protein kinase C (PKC).
19
Q

Under which conditions can DAG activate PKC?

A

When there’s Calcium

20
Q

Explain the importance of PKC’s target, AMPA.

A

PKc target is AMPA receptor (it phosphorylates it), which
leads to endocytosis (internalization of AMPA/removal of AMPA) so that the next time the parallell fiber is activated, there are less AMPA receptors and response is weaker

21
Q

What opens calcium channels at synaptic LTD in cerebellum?

A

Depolarization

22
Q

What is an important difference in the synapses between invertebrate and vertebrates in relation to learning?

A
  • invertebrate - decrease opening of presynaptic potassium channels
  • Vertebrate -decrease opening of postsynaptic AMPA receptor channels
23
Q

CA3 neurons have synapses that go where?

A

to CA1 neurons

  • call schaffer collateral
24
Q

Explain Roger Nicoll’s experiment on long-term potentiation in CA1

A
  • The response of a CA1 neuron is monitored as two inputs are alternately stimulated (q5m). LTP is induced in input 1 by giving this input a high frequency tetanus and return to q5m.
  • results in high EPSP on synapses
  • Specific to input 1 without modification in input 2
25
Q

Ca2+ entering through the NMDA receptor activates protein kinases. This can cause LTP by ?

A
  1. changing the effectiveness of existing postsynaptic AMPA receptors or
  2. stimulating the insertion of new AMPA receptors.
26
Q

What makes the potential membrane rise only at the input 1 and not 2 in Nicolls experiment? / Why is the calcium rise only lead to AMPA receptors being added to this synapse and not other synapses?

A

Compartmentalize because the dendritic spine make it such that the calcium rise only occurs within that compartment

27
Q

Describe how calcium go in through NMDA receptors

A
  • NMDA receptors are blocked by Mg
  • Mg is only removed in response to depolarization
  • following depolarization, Ca goes into the postsynapse
28
Q

What is the role of calcium in synaptic plasticity in hippocampus

A

Calcium activates kinases, which leads to more AMPA receptors being transcribed and inserted into membrane

29
Q

An application of a weak stimuli on input 1 leads to what?

A
  • a depressed response to stimulation of this input
  • long-term depression (LTD)
30
Q

When the postsynaptic cell is weakly depolarized by other inputs active synapses undergo

A

LTD instead of LTP

31
Q

Why are weaking synapses important?

A

for forgetting things or not paying attention to certain things

32
Q

What are differences of LTP and LTD in relation to AMPA?

A

LTP increases AMPA
LTD occurs due to removal of AMPA

33
Q

High frequency stimulations lead to what?

A
  • Lots of calcium in postsynapse which activate PK
34
Q

Low frequency stimulations lead to what?

A
  • modest changes in calcium which activates protein phosphatase (which remove phosphate groups)
35
Q

Synaptic strength is due to what?

A

changes in AMPA receptors AND the extra physical dimension of the spine

36
Q

Describe CaMKII

A
  • a protein kinase
  • either active or silent
  • once active, stays active for long time through autophosphorylation
37
Q

Long-term memory associated with what?

A

formation of new synapses

38
Q

Rat in complex (enriched) environment Show

A

increase in number of neuron synapses by about 25%, which require genes and new proteins

Neurobiology (3350) (8 decks)

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