Classical Conditioning in Drosophila

Question 1

What is a conditioned and unconditioned stimulus and 2 examples of each?

Answer 1

1. Conditioned = A conditioned stimulus is a previously neutral stimulus that, through repeated association with an unconditioned stimulus, acquires the ability to elicit a response e.g. bell or odour
2. Unconditioned = A stimulus that naturally and automatically triggers a response without any prior learning or conditioning e.g. reward (food) or punishment (shock)

Question 2

What is a) forward learning b) reverse learning and 2 examples of each?

Answer 2

a) Conditioned before or coincide with unconditioned stimulus
>Odour (conditioned) before or coincide with food (unconditioned reward)
>Odour (conditioned) before or coincide with shock (unconditioned punishment)

b) Unconditioned stimulus before conditioned stimulus.
>Food (unconditioned reward) before Odour (conditioned)
>Shock (unconditioned punishment) before Odour (conditioned)

Question 3

Describe the mechanisms of Forward Learning when a) Odour before/coincide with Food b) Odour before/ coincide with Shock?

Answer 3

a. Odour (conditioned) then food (unconditioned reward)
1. DopR1 activation
2. Gs -> adenylyl cyclase -> cAMP -> PkA -> LDP
3. Reward DANs cause the LDP of avoid MBONs so the fly gains acquisition of association that approaching the odour rewards with food.

b. Odour (conditioned) then shock (unconditioned punishment)
1. DopR1 activation
2. Gs -> adenylyl cyclase -> cAMP -> PkA -> LDP
3. Punishment DANs cause LDP of approach MBONs so the fly gains acquisition of association to avoid odour as approaching the odour leads to punishment of shock.

Question 4

Describe the mechanisms of Reverse Learning when a) Food is before Odour b) Shock is before Odour?

Answer 4

a) Food (unconditioned reward) then Odour (conditioned)
1. DopR2 activated first
2. Gq -> IP3 bound to IP3 receptors before cAMP from DopR1 -> ER Ca2+ release -> LTP
3. Reward DANs potentiate the depressed avoid MBONs so the fly forgets the association of approaching the odour to get a reward (as now the food is uncorrelated to the odour).

b) Shock (unconditioned punishment) then Odour (conditioned)
1. DopR2 activated first
2. Gq -> IP3 bound to IP3 receptors before cAMP from DopR1 -> ER Ca2+ release -> LTP
3. Punishment DANs potentiate the depressed approach MBONs so the fly forgets the association of avoiding the odour so it doesn’t get shocked (as now shock is uncorrelated to the odour).

Question 5

What are the 2 connections DANs form with MBONs in the Mushroom Body?

Answer 5

1. Reward DANs connect to Avoidance MBONs
2. Punishment DANs connect to Approach MBONs