BMS248 Lecture 12 - Drosophila Olfactory Learning Flashcards
(26 cards)
In classical conditioning when should the conditioned stimulus occur in regards to the unconditioned stimulus?
The conditioned stimulus shoiuld coincide with or precede the unconditioned stimulus - I.e. the conditioned stimulus predicts the unconditioned stimulus
What is the drosophila olfactory pathway beginning at the odour?
- Odour
- Olfactory receptor neurons
- Projection neurons (2nd order)
- Kenyon cells (3rd order) - CS
- Dopaminergic neurons - US
- Mushroom body output neurons
3rd order neurons (Kenyon cells) sample what to respond to respond selectively to odours?
2nd order - projection neurons
What do drosophila Kenyon cells receive input from? What do they require to fire?
Multiple projection neurons
Require multiple simultaneous inputs to fire from projection neurons - sparse coding
What type of memory are Kenyon cells the site of?
Associative memory storage - DA + KC = plasticity at the synapse
What does the GAL4/UAS system allow you to artificially express in specific cells?
Arbitrary transgenes - GAL4 binds to UAS which recruits transcription factors to initiate transcription downstream of UAS
What is the split-GAL4 system? Advantages?
Has an extra activation domain which is required to drive gene expression - increased specificity
What cell type is the mushroom body made up of?
Kenyon cells
Kenyon cell axons are subdivided into compartments by
innervation by what two types of neurons?
- Mushroom body output neurons (MBONs)
- Dopaminergic neurons (DANs)
- innervation patterns match
How are Kenyon cell axons subdivided?
One-to-one matching of dopaminergic neurons (DANs) and mushroom body output neurons (MBONs), tiling axons of Kenyon cells
Some MBONs lead to what BEHAVIOUR when activated optogenetically?
Approach/avoidance behaviour
Some DANs, when activated optogenetically can entrain what MEMORY?
Aversive or appetitive memory
Reward DANs encode the same areas as what kind of MBONs?
Reward DAN - Avoidance MBON
Punishment DAN - Approach MBON
(Opposite)
During learning, dopamine signalling has what effect on synapses between KCs and MBONs?
During learning, DANs locally depress synapses between KCs and MBONs - leading to the ‘wrong’ action.
I.e. avoidance behaviour arises from a weakening of synapses on ‘approach’ MBONs
What is the difference between forward and backward pairing?
Forward pairing - CS before US - e.g. odour then reward
Backward pairing - US before CS
In FORWARD pairing (i.e. learning) what happens to the response at KC-MBON synapses?
Depressed - decrease in respond after pairing - due to cAMP
In BACKWARD pairing what happens to the response at KC-MBON synapses?
Potentiate - increase in response after pairing - due to Ca2+
What are the two types of Kenyon cell dopamine receptors and their signalling pathways?
- DopR1 - Gs - ^ cAMP - aquisition
- DopR2 - Gq - ^ ER Ca2+ - forgetting
What pairing is DopR1 associated with?
Acquisition of memory - forward pairing - depression
What pairing is DopR2 associated with?
Forgetting memory - backward pairing - potentiation
What can be used to measure the activity of DopR1?
EPAC - sensor for cAMP
What can be used to measure the activity of DopR2?
ER-GCaMP - measures ER calcium
What is released during forward conditioning compared to backward?
cAMP released during both forward and backward conditioning.
Whereas Ca2+ release only for backward.
ER Ca2+ release is only allowed if IP3 –> Ca2+ - how?
The channel is a coincidence detector - calcium locks channel into a closed position if Ca –> IP3 - order of events
