Learning and memory 2 Flashcards
Why is the Aplyisa used extensively in neuroscience?
because Aplysia only has around 20000 neurones so it is much easier to relate specific neurones to behaviour
Who won a nobel prize for his work with Aplysia?
Eric Candel
What forms of learning does Aplysia have?
non-associative and associative
What is non-associative learning?
• Non-associative learning: change in animals behaviour as a function of experience with particular kinds of stimuli (no temporal relationship between stimuli and response)
- Habituation: loss of response because of repeated stimulus
- Dishabituation: recovery of innate response
- Sensitisation: response stronger than normal (e.g. if a student had experienced a real fire they are more sensitive to fire alarms)
what is an example of associative learning?
Classical conditioning
What was a non-associative learning experiment carried out with Aplysia?
In experiment Aplysia were kept in an aquarian with parapodium and mantle showing the gill, the movement of the gill was recorded to trace the amplification and response to a specific stimulus. The gill was then poked to elicit a response (siphon stimuli). After first stimuli there was a strong response. As poking carried on the gill response decreases. However, if a stimulus is then given a strong stimulus such as an electric shock, the response was back to normal after that (sensitisation)
How is classical conditioning shown in Aplysia?
- Tail shock is unconditioned stimulus
- Siphon stimulus is conditioned stimulus
- Group 1: siphon stimulation paired with tail shock
- Group 2: 2 stimuli were unpaired
- Group 3: received tail shock alone constituting a sensitisation control
- The paired stimuli showed much greater response to CS alone, then the US did then the unpaired
what are features of associative learning in Aplysia?
- No learning with backward pairing
- Optimal learning occurred only if CS preceded US by 0.5s – time influences learning
What is key in formulating long term memory?
Training
What is distributed vs massed training?
- Distributed training (10 trials every day for 4 days) – better than mass training
- Massed training (40 trials in one day)
What does Aplysia show long term memory for?
- Aplysia shows LT memory for habituation
- Aplysia shows LT memory for sensitisation
- Aplysia shows LT memory for classical conditioning
Give features of Aplysia’s nervous system
- Nervous system consists of ganglia
- Ganglia communicate through connectives
- Ganglia arranged in bilaterally symmetrical pairs
- Abdominal ganglion is unpaired
Controls heart rate, blood circulation and respiration
Contains primary sensory neurons, interneurons and motor neurons involved in the gill and siphon withdrawal reflex
What does synaptic analysis show about Aplysia learning?
- Influx on calcium into the cell, release of neurotransmitters, EPSP
- Sensitisation input (tail shock) -> marked increase in duration of sensory AP (spike broadening
- Spike broadening induces increase in depolarisation in century neuron terminals -> increased calcium release -> increased transmitter released -> increased EPSP (presynaptic facilitation)
What is the importance of serotonin in sensitisation and presynaptic facilitation?
- Induces facilitation
- Increases sensory neurone excitability
- Increased in motor neuron EPSP
- Increase in reflex amplitude
What does biophysical analysis in the sensory neuron tell us about aplysia sensitisation?
- Tells us about ionic events contributing to reflex
1. Serotonin temporarily closes potassium channel (S current) in sensory neuron
2. Outward potassium current is slowed
3. Repolarisation of membrane potential is slowed -> spike broadening
4. Increase calcium influx
5. Increase in transmitter release
