L11 - Habituation and Sensitisation

Question 1

What are the 4 different types of memory?

Answer 1

Declarative
Non-declarative
Short term
Long term

Question 2

What is declarative memory?

Answer 2

Something you learn and memorise

Question 3

What is non-declarative memory?

Answer 3

Skills

Question 4

Presynapse neurotransmitter release method

Answer 4

1. When the action potential arrives voltage gated Ca channels open
2. Stimulates movement of vesicle to synaptic membrane
3. Triggers release of neurotransmitter

Question 5

What proteins are involved at the presynapse?

Answer 5

SNARE proteins

Question 6

What is a way of regulating neurotransmitter release?

Answer 6

Bring the synaptic vesicle closer to where Ca enters

- Uses a variety of proteins

Question 7

What is the readily releasable pool?

Answer 7

As soon as Ca enters they fuse and release immediately

Question 8

What is the reserve/resting pool?

Answer 8

Take a while to fuse and release after Ca entry

Question 9

What types of receptor are NMDA and AMPA?

Answer 9

Part of the NMDA receptor family
They are ionotropic
When glutamate binds - receptor opens and Ca/Na enter

Question 10

What are some examples of invertebrate model organisms?

Answer 10

Snails, worms, insects

Question 11

What can you teach snails?

Answer 11

Teach snails to associate a particular smell with a positive reward

Question 12

What are the advantages of simple invertebrate systems?

Answer 12

Neuron size
Circuit complexity easier – also disadvantage as doesn’t give direct relevance to humans
Temperature dependence – most live in lower temperatures
Mapping – they have characteristic neurons

Question 13

What are the two simple forms of memory?

Answer 13

Habituation

Sensitisation

Question 14

What is habituation?

Answer 14

Form of adaptation where repeated presentation of stimulus leads to less sensitisation

Question 15

What is sensitisation?

Answer 15

Form of adaptation where repeated presentation of stimulus leads to sensitisation

Question 16

What are some examples of habituation in humans?

Answer 16

Habituation of eye blink reflex
Habituation of repetitive non-harmful stimulus presentation
Habituation of visual attention
Habituation of emotional response

Question 17

What are aplysia?

Answer 17

Type of snail with two important organs – siphon and gill

Question 18

What reflex do aplysia show?

Answer 18

Show a gill and siphon withdrawal reflex
Water jet or touch to siphon elicits gill withdrawal
- Sensory neuron is activated
- Activates motor neuron causing gill muscle to contract

Question 19

What form of memory do aplysia show?

Answer 19

They show habituation – repeated stimuli reduces reflex

• 10-15 at 10-60 seconds apart
• Occurs at abdominal ganglion synapse

Question 20

How do you test where habituation occurs?

Answer 20

Insert electrodes at presynaptic and postsynaptic neuron
Stimulate the neuron and see if you get a response
- Greater response from presynaptic neuron that postsynaptic

Question 21

What is the mechanism of habituation?

Answer 21

Results from a reduced synaptic strength
Results from a reduced transmitter release
- Depletion of readily releasable pool
- >50% lower quantal release

Question 22

What increases the gill withdrawal reflex of aplasia?

Answer 22

Sensitisation by tail pinch or shock

Question 23

What does sensitisation of the gill withdrawal reflex involve?

Answer 23

Involves pre-synaptic input from sensory neurons

- Does not just involve single sensory and motor neuron

Question 24

Sensitisation of the gill withdrawal reflex method

Answer 24

Pre-synaptic input occurs via L29 neuron from the sensitising stimulus

1. Synapses with the normal sensory neuron and serotonin released
2. Activation of G-protein
3. G-protein binds to adenylyl cyclase
4. Production of cAMP
5. Activated PKA

Question 25

Mechanism of sensitisation?

Answer 25

Simple Bear model
- pkA phosphorylates and inactivates K channels
- Longer depolarisation means more vesicular release
Serotonin-ergic feedback from other sensory neuron

Question 26

What is associative learning similar to?

Answer 26

Pavlovian conditioning

Question 27

What is an example of associative learning in invertebrates?

Answer 27

Weak siphon touch (conditioned) paired with strong shock (unconditioned)
Response to conditional stimulus increases

Question 28

Associative learning - simple bear model

Answer 28

Ca influx (conditioned) synergises 5-HT effect (unconditioned)

Question 29

What is the difference between associative learning and sensitisation?

Answer 29

Paired unconditioned and conditioned stimulus – associative
Unpaired unconditioned and conditioned stimulus – not associative learning
Unconditioned stimulus alone – sensitisation

Question 30

What are the mechanisms of sensitisation and conditioning?

Answer 30

Complex models

• Multiple intracellular signalling pathways
• Varying activation thresholds
• Pre and post synaptic
• Long term involves the nucleus