learning and memory

Question 1

DEFINE: unconditioned stimulus

Answer 1

stimulus innately producing a behaviour

Question 2

DEFINE: neutral stimulus

Answer 2

stimulus producing no conditioned response

Question 3

Split-GAL4 system

Answer 3

1. split Gal4 into activation domain and DNA binding domain
2. attach zipper domain to activation domain and another zipper domain to DNA binding domain
3. express activation domain + zipper domain under control of enhancer 1
   express DNA binding domain + zipper domain under control of enhancer 2 (different enhancer)
4. gal4 will only bind to UAS and activate transcription of gene in cells where both DNA binding domain and activation domain are expressed

Question 4

what cells are the mushroom body made up of?

Answer 4

kenyon cells

Question 5

mushroom body output neurons

Answer 5

receive input from kenyon cells

Question 6

how would you show that mushroom body output neurons lead to avoidance/approach behaviour using optogenetics?

Answer 6

1. use split-GAL4 system to express optogenetic activator in specific mushroom body output neurons (e.g. the neurons coding avoidance behaviour)
2. place flies in behaviour chamber with 4 different quadrants
3. shine light in half of the chamber. light activates neurons.
4. flies avoid the light? —-> mushroom body output neurons code avoidance behaviour
5. repeat for a different mushroom body output neuron (e.g. neuron coding approach behaviour)
6. flies approach the light? —> mushroom body output neuron codes approach behaviour

Question 7

how does learning occur in neural circuits?

Answer 7

e.g. reward dopaminergic neuron and avoidance mushroom body output neuron innervate the same compartment in the mushroom body
reward dopamine signalling depresses synapse between kenyon cells and avoidance output neuron - weakens synapse
less avoidance behaviour
reward behaviour unaffected

Question 8

what is STDP

Answer 8

spike timing dependent plasticity

Question 9

NMDA receptor

Answer 9

ionotrophic glutamate receptor

Ca2+ channel

Question 10

DEFINE: habituation

Answer 10

repeated presentation of stimulus leads to a decreased behavioural response

Question 11

DEFINE: sensitisation

Answer 11

repeated presentation of stimulus leads to an increased behavioural response

Question 12

why does habituation happen?

Answer 12

• reduced synaptic strength - post-synaptic neuron responds less to stimulus
• reduced neurotransmitter release because readily releasable pool in pre-synaptic neuron depleted

Question 13

why does sensitisation happen?

Answer 13

1. sensory neuron A (senses sensitizing stimulus) synapses onto pre-synaptic terminal of sensory neuron B (senses mild stimulus)
2. sensory neuron A releases serotonin
3. serotonin binds to g-protein coupled serotonin receptor on pre-synaptic terminal of sensory neuron B
4. activates adenylyl cyclase
5. adenylyl cyclase converts ATP to cAMP
6. cAMP activates PKA
7. PKA phosphorylates K+ channel, inactivating it
   * results in longer depolarisation so more Ca2+ enters pre-synaptic terminal and causes more vesicular release of neurotransmitters