L4 Aplysia STM

Question 1

what is the US/CS in Aplysia conditioning?

Answer 1

• electric shock is US
• Gill withdrawal is UR
• Weak tactile, non-noxious stimulus is CS - produces little gill withdrawal

Question 2

Aplysia nervous system

Answer 2

10 major ganglia each containing about 2000 neurons

Question 3

ST habituation circuit in Aplysia

Answer 3

• Change in NT release at sensory neuron terminal (locus for change)
• Ca2+-mediated inhibition of release machinery (SNAREs and associated proteins vis a GTP binding protein Arf)
• Smaller ESPSs are less likely to generate APs in the MN
• no change in postsynaptic response

Question 4

ST sensitisation circuit

Answer 4

• change in NT release induced by activity in a different pathway - heterogenous
• 5Ht-R-mediated activation of PKA and PKC and modulation of ion channel function to broaden AP and increase intraC Ca2+
• neural change underlying sensitisation is increase ESPS size at SN-MN synapses
• larger ESPSs are more likely to generate APs in the MNs
• locus of change is presynaptic SN terminal

Question 5

What specifically works to induce sensitisation?

Answer 5

modulating interneuron is serotonergic (5-HT), blocked by PKC and PKA inhibitors

Question 6

What happens in conditioning if CS precedes US?

Answer 6

calmodulin more effectively primes AC than if US precedes CS

Question 7

what type of receptor is involved in conditioning?

Answer 7

NMDA
- glutamate receptor, blocked by Mg2+
- electrostatic attraction to the negativity inside the neuron
- once membrane potential depolarised, attraction decreases no more Mg2+ blocking and cations can flow

Question 8

Coincidence detectors

Answer 8

pre-synaptic - Adenylyl cyclase
post-synaptic - NMDA receptors
modifications occuring in more than one location acting as way of detecting the coincidence and driving association

Question 9

How does habituation learning occur in Aplysia (short-term)

Answer 9

non associative, pre-synaptic, Ca2+-mediated silencing of release

Question 10

How does Sensitisation learning occur in Aplysia (Short term)

Answer 10

Non-associaticve, pre-synaptic, 5HT –> increase CAMP –> decrease K+ channel and increase Ca2+ channel –> increase NT release

Question 11

How does conditioning in Aplysia occur (Short term)

Answer 11

Associative
- Pre-synaptic - CS followed by US –> increase cAMP –> decrease K+ and increase Ca2+ channels –> Increase NT release
- Post-synaptic - increase NT –> NMDA-R –> Ca2+ entry –> Post-synaptic change –> retrograde messenger further potentiates cAMP production