questions of learning and memory

Question 1

how do third order neurones respond selectively to odours

Answer 1

sample second order neurones and respond

Question 2

what are kenyon cells

Answer 2

• in mushroom body
• each cell only responds to few odours
• receive input from multiple projection neurons and require multiple simultaneous inputs to fire (thus fire very selectively)
• sample small regions in PN “coding space”
  recieve dopaminergic transmission and edit behavioural output

Question 3

how is the dense combinational code turned into a sparse selective code for odour recognition

Answer 3

kenyon cells receive input from multiple projection neurons and require multiple simultaneous inputs to fire selectively

Question 4

what is the GAL4/UAS system

Answer 4

• binary expression system
• allows us to artificially express arbitrary transgenes in specific cells

Question 5

what is GAL4

Answer 5

yeast transcription factor
- insert into genome and control under enhancer which puts GAL4 into certain cells of body → cellular specificity
- TF binds to DNA sequence = upstream activating sequence → recruits TF to initiate transcription downstream of UAS

Question 6

what happens if you split the GAL4 system

Answer 6

split into 2 separate proteins
1 half = DNA binding domain = binds to uas
1 half = activation domain = recruits tf
only in overlap where both halves of GAL4 expression = zip together and express UAS transgene

Question 7

what is the mushroom body

Answer 7

• structure in fly brain = olfactory activity
• forms circuit for associative memory
• encode dopaminergic neurones = form different compartments of axonal lobe
• based on punishment = less = approach, more = avoid

Question 8

how are kenyon cells organised in mushroom body

Answer 8

• cell axons are subdivided into compartments by innervation of mushroom body output neurons (MBONs)

Question 9

what are MBONS

Answer 9

mushroom body output neurons
determines value = good or bad experience
Some MBONs lead to approach/avoidance behaviour when activated optogenetically
activation/deactivation leads to approach and avoidance behaviour

Question 10

role of DANS

Answer 10

dopamine activated neurones
can entrain aversive or appetitive memory

Question 11

what order are response and conditioned stimulus in for correct conditioning

Answer 11

odour -> punishment = avoid
punishment -> odour = relief = approach

Question 12

how do flies know whether CS or response comes first

Answer 12

1. electrically stim kenyon cells
2. recording MBON
3. artificially stim dopa neurone using art receptor + ligand
4. measure response of MBON to kenyon cell = measures synaptic strength

Question 13

which type of cells in MB are linked to odour detection

Answer 13

kenyon

Question 14

which type of cells in MB are linked to reward detection

Answer 14

DANS

Question 15

what happens when kenyon cells and DANS are activated at same time

Answer 15

activation at same time = synaptic depression

Question 16

difference between dopr1 and dopr2

Answer 16

• signal through different gpcr pathways
• 1 = Gs → AC → cAMP
• 2 = Gq → PLC → IP3 → Ca2+ release

Question 17

how is ER Ca release sensitive to order?

Answer 17

• IP3 receptor = sensitive to Ca
• Ca = signal for when kenyon cell is active
• IP3 → Ca = open
• Ca → IP3 = not open
• 2 possible binding sites for Ca
• if no ip3 = only red binding site available = locks receptor into conformation
• no ca = green is open → channel opens

Question 18

what happens if ca binds to ER channel first

Answer 18

ca → locks → no ip3

Question 19

what happens if ip3 binds to ER channel first

Answer 19

ip3 → ca binds → open

Question 20

do we have similar odour detection structure as drosophila

Answer 20

• similar structure in cerebellum
  
  • mossy fibres → more neurones (granule) → purkinje cells
  • synapse between gran and purkinje fibres is modified by climbing fibres

Question 21

what carries error signals

Answer 21

climbing fibres modify sinapse between granular and purkinje fibres