Modern questions in learning and memory Flashcards
What do kenyon cells receive input from?
Multiple projection neurons
What do Kenyon cells require to fire?
multiple simultaneous inputs
What do 3rd order neurons do?
Sample 2nd order neurons to respond selectively to odours
How much of the coding space are Kenyon cells sampling?
Very small part
What happens when a fly receives reward or punishment?
- Activation of dopaminergic neurons
- Co-activation of odor specific subset of kenyon cells
- synaptic plasticity at the output synapses of the kenyon cells activated
What do changes in olfactory associative memory lead to?>
Changes in behaviour
What can overlapping and subsequent activation of Kenyon cells lead to?
If an odour and a particular subset of Kenyon cells are associated with a bad odour and a new odour overlaps with some of these cells it can also lead to avoidance
What does the Gal4/UAS system allow us to do?
Artificially express arbitrary transgenes in specific cells
How does Gal 4 work?
Bind to UAS (upstream activating system)
Recruits RNA polymerase
Induces the transcription of anything following UAS
Can combine Gal4 and UAS to transcribe any gene you want
What does the split Gal 4 system allow?
Greater specificity
What is the mushroom body made up of?
Kenyon cells
What is it innervated by?
Dopaminergic neurons (dont overlap)
What is there 1:1 matching between?
Dopaminergic neurons and output neurons
In Kenyon cells what does stimulation of a reward neuron lead to? (approach or avoid)
Stimulation of reward leads to a WEAKENING of the avoidance behaviour
What happens if you shock a fly before an odour? (what behaviour does this lead to?)
Approach behaviour because the odour marks the end of the negative stimulus
So from above, how can stimulation of the same of dopaminergic neurons lead to different responses?
2 types of dopamine receptor
What do you potentiate if a reward comes right before an odour?
the avoidance neuron
What happens if you reward comes right after or overlaps odour?
you depress and behaviour becomes a conditioned approach
What type of G protein is the dDA1 dopamine receptor? (DopR1)
Gs
What pathway does the dDA1 receptor represent?
Aquisition
What type of G protein is the Damb receptor? (DopR2)
Gq
What pathway is the DopR2 receptor involved in?
forgetting
Which pathway therefore is important for potentiating the synapse and which for depressing? (think its not that obvious)
Acquisition pathway important for depressing and vice versa
What is the analogy to the cerebellum?
Projection neurons going onto kenyon cells = Mossy fibres going onto granule cells in the cerebellum forming parallel fibres which are intersected by purkinje cells
What are synapses between the granule cells and the Pukinje cells depressed by?
Climbing fibres
What do climbing fibres carry?
messages that say you have made a mistake (depression)
What drives motor learning?
LTD between granule cells and purkinje cells this drives motor leaning
What is the problem that the electric fish has?
The electricity it produces is also picked up by its own cells
How does error correction get around this problem for the electric fish?
- Electric organ sends efferent copy
- Granule cells active are cancelled out by matching efferent copy
- by depressing synapse between granule cell and purkinje cell
What is the difference between sensitisation and associative learning?
the same neurons are stimulated, but simultaneously in associative learning
