lecture 13- modern qs in learning and memory Flashcards
what is classical conditioning
associating 2 stimuli with eachother
conditional stimulus should precede/ coincide with the unconditional stimulus
describe the T maze test for flies
flies exposed to odour A with either sugar treat or shock
after training the flies can choose between A and B (normal odour)
record percentage spent with each odour
describe the Computer method for flies
1fly in each chamber
pump in different odours and track movements
describe the olfactory circitory pathway in flies
odour -> olfactory receptor neurons -> projection neurons -> kenyon cells
where are kenyon cells located, describe their firing
mushroom bodies
they require multiple simultaneous inputs to fire so they fire selectively
sample small regions of 3D space of axon projections
how does dopamine work with kenyon cells to elicit a response
dopamineric neurons modify the outputs of kenyon cells
coactivation of kenyon cells and dopamine leads to either reward/punishment response
what is the GAL4/ UAS system used for
artificial expression of arbitrary transgenes in specific cells
describe how the GAL4 / UAS system works
- GAL4 gene is placed under control of specific promotor/enhancer
- GAL4 protein is a TF that binds to UAS
- the choice of the promotor determines when and where this binds
- UAS is placed upstream of gene of interest
- Alone they dont work but when you cross a GAL4 fly with a UAS fly, the offsping inherit both so it activates transcription of the target gene
describe split GAL4 and what this can be used for
provides greater specificity in gene expression
GAL4 is split into two separate domains:
DNA-Binding Domain (DBD) – Binds to the UAS but cannot activate transcription alone.
Activation Domain (AD) – Activates transcription but cannot bind DNA alone.
Gene expression occurs only in cells where both DBD and AD are present, allowing precise targeting of specific cell populations.
which 2 structures can divide kenyon cells into certain compartments
mushroom body output neurons (MBONs)
dopainergic neurons (DANs)
describe synaptic depression between kenyon cells and their outputs
1) DANs in MB release dopamine in response to electric shock
2) DANs activate specific compartments of KC -> MBON synpases
3) dopamine triggers synaptic depression at KC -> MBON synpases which decreases MBON activation in response to conditional odour
4) the next time the fly encounters the same odour, the MBON is weaker so it avoids
How was synaptic depression in kenyon cells proved
split GAL4 system
are KC-MBON synapses depressed pre or post synaptically
pre
what is paired pulse stimulation
stimulate pre-synaptic neuron x2 in quick sucession and record excitatory postsynaptic currents (EPSCs) in the post synaptic neuron
describe paired pulse depression
2nd pulse is smaller than first as pre synaptic neuron used lots of vesicles on the first pulse
this means higher release probability (each vesicle has a higher change of being released)
describe paired pulse facilitation
2nd pulse bigger than first as leftover Ca2+ in presynaptic terminal from first pulse
this mean low release probability
what is the result of a paired pulse test for dopamine ->MBONs and what does this tell us
the original paired pulse depression turns into paired pulse facilitation
means presynaptic effect
describe learning in insect mushroom bodies
training reduces the ‘wrong’ behaviour
describe learning in the cerebellum
motor learning tries to correct the ‘wrong’ behaviour
describe learning in fish
they have electroreceptors that receive inputs from electric organ and external electric fields
this allows them to learn to ignore ‘wrong’ electric signals generated by their own electric organ
