10 - Learning and Memory - LTD<P mechanisms

Question 1

What is procedural memory?

Answer 1

Skills and association largely unavailable to the conscious mind.

Question 2

What is declarative memory?

Answer 2

Memory that is available to the conscious mind can be encoded in symbols and language.

Question 3

What is explicit memory?

Answer 3

Memory that can be consciously recalled. eg declarative

Question 4

What is implicit memory?

Answer 4

Memory that cannot be consciously recalled. eg procedural memory, classical conditioning.

Question 5

What are some advantages that simple systems have?

Answer 5

• Their neuronal size
• Circuit complexity
• Mapping tools

Question 6

What are 2 simple forms of memory?

Answer 6

Habituation and sensitisation.

Question 7

What is habituation?

Answer 7

• A form a memory where the amplitude of response decreases when the stimulus is applied many times.
• Causes a depletion in the synaptic vesicle pool.

Question 8

What is sensitisation?

Answer 8

A form of memory where the amplitude of response increases when the stimulus is applied many times

Question 9

What kind of habituation does Aplysia Californica show?

Answer 9

The gill withdrawal reflex, the reflex slows down as the stimuli is repeated.

Question 10

What is the neuronal basis of habituation?

Answer 10

When the pre-synaptic neuron is stimulated the amplitude stays the same but when the post-synaptic neuron is stimulated the amplitude starts to decrease.
- Shows reduced synaptic strength.

Question 11

What is the cellular basis of habituation?

Answer 11

A reduced neurotransmitter release due to a depletion of the readily releasable pool (RRP).

Question 12

What would be a sensitisation response from Aplysia Californica?

Answer 12

An increased gill withdrawal reflex evoked by the tail pinch or the shock.

Question 13

What input does the sensitisation response from Aplysia involve?

Answer 13

Pre-synaptic input to the sensory neuron also the action of serotonin and G-Protein action.

Question 14

What is the example of a neuron that senses the sensitising stimulus?

Answer 14

L29

Question 15

What is the molecular basis of sensitisation?

Answer 15

pkA phosphorylates and inactivates the potassium ion channels and a longer depolarisation means more vesicular release.

Question 16

What is the Hebbian synapse?

Answer 16

A synapse where the coordinated activity of a pre-synaptic terminal and a post-synaptic neuron strengthen the synaptic connections between them.

Question 17

What is the simplified version of the hippocampal circuit?

Answer 17

• input comes in through the entorhinal cortex and goes to the denate gyrus in what is known as the Perforant pathway.
• Input then travels from the denate gyrus to the Ca3 through mossy fibres.
  -The Ca3 to Ca1 though Schaffer collaterals
• All the output then leaves via the fornix and the subiculum.

Question 18

Where does LTP normally take place?

Answer 18

In Ca3 to Ca1 synapses which are glutamatergic.

Question 19

What kind of stimulus comes from long term potentiation?

Answer 19

A high frequency stimulus which resembles the human Q rhythm and produces long lasting potentiation.

Question 20

How does LTP show input specificity?

Answer 20

By only acting on the neuron that is activated, this increases the amplitude of the EPSP.

Question 21

What is cooperativity in LTP?

Answer 21

When 2 pathways converging on the same target can both be strengthened if they fire together. (although one pathway may be quite weak)

Question 22

What are the 3 types of glutamate receptors?

Answer 22

AMPAR (non-NMDA), NMDAR and mGluR.

Question 23

What kind of receptor is the AMPA receptor?

Answer 23

The main ionotropic receptor which is more permeable to sodium and potassium ions.

Question 24

What kind of receptor is the NMDA receptor?

Answer 24

An ionotropic receptor which is more permeable to calcium ions.

Question 25

What kind of receptor is a mGlut receptor?

Answer 25

A metabotropic receptor.

Question 26

How does LTP occur?

Answer 26

• Could be by pre-synaptic changes but evidence suggests that it is a post synaptic event
• NMDA receptors open releasing calcium ions into the post-synaptic neuron
• Calcium then activates kinases eg caMKII which phosphorylates different proteins leading to an increase in amplitude of the EPSP.

Question 27

Why do NMDA receptors need to be pre-activated by a depolarising input?

Answer 27

Because they have a voltage gated magnesium block, the pre-activation is done by a glutamate in the allosteric site.

Question 28

How is early LTP activated?

Answer 28

• NMDA receptor mediated calcium ions activate calmodulin kinase II (CaMKII) due to the increase in calcium ions.
• Calcium and calmodulin bind to CaMKII and cause conformational change which leads to the activation of the protein which will then be phosphorylated.

Question 28

How is early LTP activated?

Answer 28

• NMDA receptor mediated calcium ions activate calmodulin kinase II (CaMKII) due to the increase in calcium ions, calcium and calmodulin then bind.

Question 29

What does the binding of calcium and calmodulin to CaMKII cause?

Answer 29

Conformational change which leads to the activation of the protein which ill then be phosphorylated.

Question 30

What does phosphorylation of the protein do for AMPA?

Answer 30

Enhances the AMPA currents which may involve AMPAfication (the increase in the number of AMPA receptors.)

Question 31

How is Late LTP activated?

Answer 31

BY cAMP signalling, this activates pKA which may activate other proteins and translocate to the nucleus and phosphorylate proteins there.

Question 32

How do we know LTP is linked to memory?

Answer 32

Because inhibiting LTP inhibits some memory formation

Question 33

What are the LTD inputs in the cerebellum?

Answer 33

Positive mossy and climbing fibres.

Question 34

What are the LTD outputs in The cerebellum?

Answer 34

Negative purkinje fibres.