L11 - Habituation and Sensitisation Flashcards
What are the 4 different types of memory?
Declarative
Non-declarative
Short term
Long term
What is declarative memory?
Something you learn and memorise
What is non-declarative memory?
Skills
Presynapse neurotransmitter release method
- When the action potential arrives voltage gated Ca channels open
- Stimulates movement of vesicle to synaptic membrane
- Triggers release of neurotransmitter
What proteins are involved at the presynapse?
SNARE proteins
What is a way of regulating neurotransmitter release?
Bring the synaptic vesicle closer to where Ca enters
- Uses a variety of proteins
What is the readily releasable pool?
As soon as Ca enters they fuse and release immediately
What is the reserve/resting pool?
Take a while to fuse and release after Ca entry
What types of receptor are NMDA and AMPA?
Part of the NMDA receptor family
They are ionotropic
When glutamate binds - receptor opens and Ca/Na enter
What are some examples of invertebrate model organisms?
Snails, worms, insects
What can you teach snails?
Teach snails to associate a particular smell with a positive reward
What are the advantages of simple invertebrate systems?
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
What are the two simple forms of memory?
Habituation
Sensitisation
What is habituation?
Form of adaptation where repeated presentation of stimulus leads to less sensitisation
What is sensitisation?
Form of adaptation where repeated presentation of stimulus leads to sensitisation
What are some examples of habituation in humans?
Habituation of eye blink reflex
Habituation of repetitive non-harmful stimulus presentation
Habituation of visual attention
Habituation of emotional response
What are aplysia?
Type of snail with two important organs – siphon and gill
What reflex do aplysia show?
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
What form of memory do aplysia show?
They show habituation – repeated stimuli reduces reflex
- 10-15 at 10-60 seconds apart
- Occurs at abdominal ganglion synapse
How do you test where habituation occurs?
Insert electrodes at presynaptic and postsynaptic neuron
Stimulate the neuron and see if you get a response
- Greater response from presynaptic neuron that postsynaptic
What is the mechanism of habituation?
Results from a reduced synaptic strength
Results from a reduced transmitter release
- Depletion of readily releasable pool
- >50% lower quantal release
What increases the gill withdrawal reflex of aplasia?
Sensitisation by tail pinch or shock
What does sensitisation of the gill withdrawal reflex involve?
Involves pre-synaptic input from sensory neurons
- Does not just involve single sensory and motor neuron
Sensitisation of the gill withdrawal reflex method
Pre-synaptic input occurs via L29 neuron from the sensitising stimulus
- Synapses with the normal sensory neuron and serotonin released
- Activation of G-protein
- G-protein binds to adenylyl cyclase
- Production of cAMP
- Activated PKA
Mechanism of sensitisation?
Simple Bear model
- pkA phosphorylates and inactivates K channels
- Longer depolarisation means more vesicular release
Serotonin-ergic feedback from other sensory neuron
What is associative learning similar to?
Pavlovian conditioning
What is an example of associative learning in invertebrates?
Weak siphon touch (conditioned) paired with strong shock (unconditioned)
Response to conditional stimulus increases
Associative learning - simple bear model
Ca influx (conditioned) synergises 5-HT effect (unconditioned)
What is the difference between associative learning and sensitisation?
Paired unconditioned and conditioned stimulus – associative
Unpaired unconditioned and conditioned stimulus – not associative learning
Unconditioned stimulus alone – sensitisation
What are the mechanisms of sensitisation and conditioning?
Complex models
- Multiple intracellular signalling pathways
- Varying activation thresholds
- Pre and post synaptic
- Long term involves the nucleus
