Week 4 Flashcards

1
Q

What do synapses exhibit?

A

Many forms of plasticity

Due to molecular and structural changes

Changes may represent more permanent changes in brain function

Contribute to learning and memory in

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2
Q

How is the nervous system changed by a specific learning task?

A
  1. Exploit the relative simplicity of CNS in some invertebrates
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3
Q

What did Eric Kendal et al use Aplysia Californica to study?

A
  1. Elemental forms of behavioural and synaptic plasticity
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4
Q

What does Aplysia exhibit?

A

Several forms of plasticity

E.g. applying a tactile stimulus to siphon of Aplysia results in withdrawal of animal gills

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5
Q

What does repeated siphon stimulation cause?

A
  1. Gill withdrawal to weaken

Animal becomes less response to repeated occurrence to a stimulus (e.g. habituation)

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6
Q

What form of plasticity does GWS exhibit?

A

Sensitisation

Aplysia that have habituated to siphon touching

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7
Q

What elicits a strong gill withdrawal?

A

A strong electrical stimulus to the tail paired with a light touch of the siphon

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8
Q

What does sensitisation allow an animal to generalise?

A
  1. Aversive response elicited by a noxious stimuli to a variety of non-noxious stimuli
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9
Q

Aplysia that receives a single stimulus to tail?

A

GWR remains enhanced over an hour

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10
Q

How can behaviour be altered for days/weeks?

A

Repeated pairing of tail and siphon stimuli

Demonstrate simple form of long term memory

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11
Q

What gives prolonged sensitisation of GWR?

A

Repeated tail shock for several days

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12
Q

How does CNS make it possible to define a synaptic circuit involved in gill withdrawal?

A
  1. The small number of neurons in CNS

2. Monitor activities of inidividual neurons and synapses in these circuits

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13
Q

How can the cell bodies of many neurons involved in gill withdrawal be recognised?

A
  1. Size
  2. Shape
  3. Position within abdominal Ganglia
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14
Q

What are short term sensitisation be mediated by?

A
  1. Signal transduction cascade that involve neurotransmitter, second messengers , one or more protein kinase and ion channels
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15
Q

What does the signal transduction cascade enhance?

A
  1. Synaptic transmission between sensory and motor neuron within gill-withdrawal circuit
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16
Q

What is thought to underlie long-term sensitisation?

A

Serotonin induced enhancement of glutamate release that mediate short term sensitisation

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17
Q

During long-term sensitisation how long is the circuit affected by?

A
  1. Several weeks
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18
Q

What is prolonged plasticity evidently due to?

A
  1. Gene expression

2. Protein synthesis

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19
Q

How is the transcriptional activated CREB activated?

A

Repeated training (additional tail shocks)

Serotonin activates PKA involved in short term-sensitization

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20
Q

What does CREB binding to CAMP response element CRE increase?

A
  1. The rate of transcription downstream genes
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21
Q

What stimulates the degradation of regulatory subunit of PKA?

A
  1. Ubiquitous hydroxylase
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22
Q

What is the molecular mechanism of short term sensitization?

A
  1. Serotonin released by the facilitatory interneuron bund to G-protein coupled serotonin receptors on pre-synaptic terminal of siphon sensory neuron activating the G protein
  2. The activated G-protein dissociates from the receptor and binds to and activates other signalling molecule such as - adenylyl cyclase
  3. Adenylyl Cyclase stimulates the production of second messengers CAMP from ATP
  4. The CAMP bindings to PKA
  5. Liberating catalytic subunit of PKA can phosphorylate several proteins which include potassium channels
  6. When a sensory neuron synapse is depolarised, calcium channel open and calcium ions enter terminals
  7. Phosphorylation of potassium channels by PKa results in fewer open potassium ion channel - prolongs the duration of de-polarisation and increasing influx of calcium
  8. The enhanced influx of calcium - more neurotransmitter being released
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23
Q

Eat accounts for gill withdrawal during habituation and sensitisation?

A
  1. Only a few different types of neurons
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24
Q

What do the critical neurons include?

A
  1. The sensory neuron that innervate siphon
  2. Motor neuron that in innervate muscles in the gill
  3. Interneurons that receive input from a variety of sensory neurons
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25
Q

What does touching the siphon activate?

A

Sensory neuron which form excitatory synapse that release glutamate to both interneuron and motor neuron

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26
Q

What effects can be seen when monitoring electrical activity of the neuron?

A

The effect that touching the siphon has in both post-synaptic target

27
Q

What do both habituation and sensitisation appear to arise from?

A

Plastic changes in synaptic transmission of circuit

28
Q

What Happens during habituation?

A

Transmission at glutamatergic synapse between sensory and motor neuron is depressed

Decreasing ability of siphon stimuli

Depression is pre-synaptic

Reduction in number of synaptic vesicles available for release in axon terminals

29
Q

What activated sensory neuron that innervate the tail?

A

Tail shock that excites sensitisation

30
Q

What does the sensory neuron that excite modulatory interneuron release?

A
  1. Serotonin onto pre-synaptic terminal of sensory neuron of siphon
31
Q

What does serotonin enhance?

A

Transmitter release from siphon-sensory neuron terminal leading to increased synaptic excitation of other motor neurons

32
Q

What can elicit a strong gill withdrawal response?

A

Light touch on the siphon

33
Q

How long does the modulation of sensory neuron - motor neuron synapse last?

A

Approx an hour which is similar to short-term sensitization of gill withdrawal produced by applying a single shock to tail

34
Q

Habituation and sensitisation

A

Processes that are shifting the strength of connections in opposite directions

35
Q

Long term sensitization

A

Acquire connections

36
Q

Short term sensitization

A

Loose connections

37
Q

Define learning

A

The process of acquiring, through experience, new and relatively enduring information of behaviours

38
Q

What did Pavlov do?

A

Paired the presence of meat powder which got dogs to drool with lots of different neutral stimuli

39
Q

Define associative learning

A

When a subject links certain events, behaviours or stimuli together in the process of conditioning

40
Q

What is the unconditioned stimulus

A

Meat

41
Q

Unconditioned response

A

Salivation in response to meat

42
Q

Conditioned stimulus

A

Bell

43
Q

Conditioned response

A

Salivation in response to bell

44
Q

What is the most common procedure of associative learning in Aplysia?

A
  1. Apply tactile CS to the mantle followed by a shock (US) to tail
45
Q

What is CS-

A

Light touch to siphon delivered to shock to the tail

46
Q

What is CS+

A

Light touch was delivered to mantle before shock oto tail

47
Q

What is the US in Aplysia?

A

Electrical shock to tail

48
Q

What is conditioned stimulus (CS) is Aplysia?

A

Delivered light touch to part of animal that will not trigger GWS

49
Q

Strengthening of a synapse?

A

Shock is delivered to tail in association with mantle shelf being stimulated

50
Q

What is a co-regulator or adenylate cyclase?

A

Calmodulin

51
Q

What do you get an increase of in CS+ pathway but not in C- pathway ?

A
  1. Increase in active zones

2. Synaptic connections for sensory neurons

52
Q

What changes are occurring in C+ pathway?

A
  1. Structural changes

2. Caused by changes in gene expression

53
Q

What is the classic approach to Drosophila?

A
  1. Ability to generate mutants
54
Q

What can Drosophila be exposed to?

A
  1. Mutagens
  2. Progeny can have mutagens in genome and generate different strains
  3. Screen different Mutant strains to see whether any particular strains have deficiency in them
55
Q

What did the normal flies do?

A
  1. Presented with electric shock
  2. That electric shock is paired with a presentation of some sort of olfactory stimulus
  3. They will learn to associate that chemical with electric shock and will avoid going into that little tube
56
Q

What were the examples of other Drosophila mutants that have been identified that are deficient in learning task?

A
  1. RUTABAGA (Rut)
  2. CABBAGE (cab)
  3. TURNIP (tur)
  4. RADISH (rad)
  5. AMNESIAC (amn)
57
Q

What is DUNCE?

A
  1. Mutants can learn in short term (within 30 seconds of training)
  2. Memory decays rapidly after this
  3. Mutations affects long term memory
  4. The gene affected codes for CAMP-phosphodiesterase (hydrolyses CAMP)
  5. Abnormally high CAMP levels
58
Q

RUTABAGA

A
  1. The gene affected encodes a Ca2+/calmodulin regulated adenylyl cyclase
59
Q

CABBAGE

A

The identity of cab gene product is not known

60
Q

TURNIP

A
  1. Rapidly forgetting mutant
  2. Olfactory learning paradigms
  3. Reduced levels of PkC activity
  4. The tur gene product may be required for activation of PKC
61
Q

Radish

A
  1. Encodes a protein with 23-predicted cyclic AMP dependent protein kinase A phosphorylation sequences
62
Q

Amnesiac

A

Normal learning

Rapid forgetting in olfactory learning task

Encodes a neuropeptide that is related to mammalian neuropeptide Pituitary Adenylate Cyclase Activating Polypeptide (PACAP)

63
Q

What has independent research on Aplysia and Drosophila identify?

A
  1. CAMP signalling as an important player in mechanism of learning and memory