Lecture 6 - Models for Studying L & M Flashcards
What kind of stimuli were paired by Pavlov?
Paired an unconditioned stimulus(food) with a neutral stimulus (bell)
What is the unconditioned stimulus and the response in Aplysia?
Touch siphon - gill withdrawal
How do you sensitise Aplysia?
Pair electric shock to touch on siphon will give you a very strong gill withdrawal
Hows many neurons does Aplysia have?
Around 20000
Why is Aplysia used as a model?
Cell bodies of neurons are 1mm in diameter so injection is easy
How can you change the term of the learned behaviour in Aplysia?
Repeated pairing (more shocks in a row on more days)
What is the neural circuitry of the tail shock?
Sensory neuron synapses on modulatory interneuron which then synapses (with serotonin) onto the axon of the sensory neuron innervating the siphon.
What happens as you touch the siphon more and more with out a shock?
The sensory neuron from it releases less and less glutamate onto the interneuron and motor neuron of the gill
How does the shock change the neural circuitry?
Modulatory interneuron synapses and releases serotonin onto the axons of the sensory neuron from the siphon, increasing the amount of glutamate being released from that onto the interneuron and motor neuron of the gill. (presynaptic facilitation)
How does the modulatory interneuron cause presynaptic facilitation?
The serotonin increases PKA by making 5-HT bind to the PKA receptors leading to more NT release
Who used Aplysia as a model?
Candell
Why is the fly a good model?
Allows you to change what, where and when proteins are expressed
What experiment did Dudai et al (1976) do with flies?
Taught to avoid an odor (OCT) by giving them an electric shock when exposed to it.
When offered the choice of the shock odor and an odor they didn’t know, most went to the latter (MCH)
What form of learning do the Aplysia and flies show?
Implicit learning
What is dunce?
The first memory mutant fly found
What is dunce’s mutation in?
cAMP phosphodiesterase (degrades cAMP)
What is rutabaga?
Second memory mutant found
What is rutabaga’s mutation in?
Adenylyl cyclase (forms cAMP)
What were the results of Dudai’s odor experiment and what does this suggest?
dunce and rutabaga had a memory performance of about 40% wheras WT was 90%.
Double mutant was 17%.
cAMP important in learning.
What did cued fear conditioning in rats involve?
Sound played before electric shock, rats froze when they heard the sound.
Could measure several things like freezing time and blood pressure
What is contextual learning?
Changing the environment but giving the same negative stimulus - the rat animal will know next time the environment changes and freeze
What is fear extinction?
Giving the conditioned neutral stimulus over and over with out the negative stimulus (eg shock) so the animal forgets
What parts of the brain are involved in cued fear conditioning?
amygdala
What parts of the brain are involved in contextual conditioning?
amygdala and hippocampus
What are two good examples of operant conditioning?
Skinner box and Pavlov’s dogs
How can you test implicit memory and some elements of explicit memory?
Morris water maze
Features of Morris water maze
- 3 visual cues around the room
- Small platform in opaque water
What things are measured in the morris water maze?
- Latency - time taken to get to platform
- Platform crossings - around the platform
- Time spent in quadrants - see if its correct
What experiment did Bourtchuladze et al (1994) do?
- Had mice with disruption in gene encoding CREB (a TF activated by cAMP and Ca)
- Did spatial learning in morris water maze
What were the results of Bourtchuladze et al (1994)’s experiment?
CREB mutants show a significantly decreased memory
What were the controls in Bourtchuladze’s experiment to check the mutants had the same sensory and motor functions?
- Mutants and WT exposed to unpleasant stimuli, flinching, jumping and vocalising measured
What did Bourtchuladze show with intensive training?
Showed that if the mutants were trained much harder they were just as effective as the controls
