Learning and memory I Flashcards
What are the 2 ways to describe memory?
1) Declarative or non-declarative
2) Long-term or short term
What is declarative memory?
Something you learn in terms of KNOWLEDGE (information, facts)
What is non-declarative memory?
Skills (walk, play instrument etc.)
What are the key players in memory formation?
Presynapses
What happens when an action potential arrives at the presynapse?
- Voltage gated Ca2+ channels open - Ca2+ into the cell
- Ca2+ inside the cell increases, causing the release of neurotransmitter into the synaptic cleft by increasing the fusion of synaptic vesicles to the presynapse
What proteins are involved in regulating the docking of vesicles at the presynaptic membrane?
SNARE proteins
Where are Ca2+ binding proteins present?
On the membrane of vesicles
What is one way to control the release of neurotransmitter into the synaptic cleft?
By regulating the distance between the VESICLES and the Ca2+ CHANNELS
How many different types of vesicles are there in the presynaptic terminal?
What classifies them into their types?
3 different types
Classified by their ‘readiness’ to fuse with the presynaptic membrane
What are the 3 types of vesicles in the presynaptic terminal?
1) Readily available pool vesicles
2) Proximal pool
3) Reserve/resting pool
Where are readily available vesicles present?
When are they releases?
Present at the active zone of the presynapse
INSTANTLY fuse when there is a Ca2+ influx
Where is the proximal pool of vesicles present?
What do they become when Ca2+ influx?
Present slightly away from the active zone
Not released instantly, but become READILY RELEASABLE vesicles shortly after the Ca2+ influx
What does the regulation mechanism inside the presynaptic terminal do?
Regulates the time of the reserve pool into the proximal pool and into the readily releasable pool
What is important for short-term memory in adaptation?
The DEPLETION of the READILY RELEASABLE pool of vesicles in the presynaptic terminal
How many different types of glutamate receptors are there
What are they called?
3 different classes:
- NDMA receptors
- Non-NDMA receptors (AMPA receptors)
- mGlut receptors
Which of the glutamate receptors are ionotropic?
Metabotropic?
Ionotropic - NDMA and non-NDMA
Metabotropic - mGlut
Which of the glutamate receptors is permeable for Ca2+ as well as Na2+?
NDMA
Which of the glutamate receptors is important in memory?
NDMA
Which of the glutamate receptors is G protein coupled?
mGlut
Which of the ionic glutamate receptors is not permeable to Ca2+?
non-NDMA (AMPA)
How can invertebrates learn?
What are the advantages of this?
Learn with a positive reward
Advantages:
- Neurons are larger
- Easier circuit complexity
- No temperature-dependance
- Mapping of neurons is easy
What are the disadvantages of using invertebrates to model learning?
Circuitry doesn’t give direct relevance to humans - can only understand the basics of key mechanisms
How is mapping of invertebrate neurons easier than in humans?
- Neurons are characteristic
- Can identify every neuron
- Have the exact number of neurons in each individual
What are 2 simple types of memory present in invertebrates?
1) Habituation
2) Sensitisation
What is habituation?
Where repeated presentation of a stimulus results in a DECREASE in response to that stimulus
(DESENSITISATION)
What is the one condition of habituation?
Only occurs if the stimulus is NOT harmful
What is sensitisation?
Where repeated presentation of a stimulus results in an INCREASE in behavioural response to that stimulus
What are examples of habituation in humans?
1) Blink reflex
2) Repetitive non-harmful stimulus presentation
3) Visual attention
4) Emotional response (eg. more exams you take, the less nervous you get)
What is an aplysia?
A sea snail (invertebrate)
What are the 2 important organs in aplysia?
What are they important in?
Siphon - important in locomotion
Gill - important in respiration
What happens in aplysia when you touch the gill?
What is responsible for this movement?
It is withdrawn
Neural circuit is responsible:
- Sensory neuron (activated when the siphon is touched)
- Motor neuron
What does repeated stimuli of the gill cause?
Habituation - reduces the gill reflex
How can you test if the habituation mechanism of the gill reflex is localised to the siphon?
Is this the case?
Record from the sensory neuron cell body:
- If repeatedly touch the siphon and see habituation at the level of the cell body - must be localised to the siphon
However, NOT the case
How can you test if the habituation mechanism of the gill reflex is at the level of the synapse between the sensory neuron and the motor neuron?
Is this the case?
Using 2 electrodes:
- Insert one into the sensory neuron
- One into the motor neuron
- Inject current into the sensory neuron and observe the response of the motor neuron
- If habituation occurs - see the response in the post synaptic neuron get smaller
This IS the case
How does habituation occur?
Describe this
Due to reduced neurotransmitter release:
- Readily releasable pool of vesicles is depleted
- Reducing the number of vesicles that can be released in the NEXT stimulation
Is sensitisation more or less pronounced than habituation?
More pronounced
Describe how we can sensitise the aplysia
- Produce a small electic shock to the tail of the aplysia BEFORE touching the siphon
- This produces a larger gill withdrawal reflex
THEN,
- No longer provide the electric shock
- When touch the siphon, produces a larger response than if didn’t have the electric shock applied
What sensory neurons is involved in the sensitisation of the gill reflex in aplysia?
How?
Sensory neuron L29:
- Is ACTIVATED when provide an electric shock
- This neuron synapses onto the presynaptic site of the sensory neuron
- Presynapse of L29 releases SEROTONIN - activates serotonin receptors (GPCR)
- This activtes adneylyl cyclase in the sensory neuron presynapse
- Activates PKA
- PKA phosphorylates many other proteins, causing conformational changes and changes in function
What is the sensory neuron that senses the touch of the siphon postsynaptic for?
Presynaptic for?
Postsynaptic for the L29 neuron
Presynaptic for the motor neuron that travels to the gill
What is the mechanism of sensitisation?
1) pKA phosphorylates and inactivates K+ channels, causing a LONGER DEPOLARISATION
2) Ca2+ works LONGER
3) More Ca+ enter presynaptic site
4) More neuroT release
What is the difference between habituation and sensitisation?
Habituation - depletion of the readily releasable vesicle pool
Sensitisation - serotonergic feedback causing more neurotransmitter release
What is associative learning?
A learning process in which a response becomes associated with a particular stimulus
What happens in associative learning?
- Pair a conditional stimulus with a non-conditional stimulus
- Remove the non-conditional stimulus
- The conditional stimulus will be able to produce the same response as the non-conditioned stimulus
What is the non-conditional stimulus?
The stimulus that normally evokes a particular response
What is the conditional stimulus?
The stimulus that doesn’t normally evoke that response
Why is the presentation of the stimulus crucial in associative learning?
If they are not presented at the same time - don’t get associative learning
What is the synapse used in associative learning?
The same synapse as used in sensitisation - between the L29 and the other sensory neuron
What happens when CS is paired with US?
How?
Have a longer response that is BIGGER than sensitisation:
- BOTH neurons are activated at the SAME time
- Release of BOTH serotonin (from L29) and Ca2+ (from the other sensory neuron)
- Adenylyl cyclase then works more and synergiese 5-HT effect (US)
What is synergisation?
Combined activity produces a JOINT greater effect than the sum of their SEPARATE effects
What are the differences between sensitisation and conditioning?
Many different mechanisms
What does long-term sensitisation involve?
The nucleus - change of gene expression
How can inhibitory interneurons be sensitised?
During habituation
