L19 Synaptic Plasticity

Question 1

Outline the mechanism underlying synaptic strengthening

Answer 1

Repeated HFS lasts days/months

Perforant pathway

Question 2

What is alcohol?

Answer 2

NMDA receptor antagonists

Question 3

What are benzodiazepines?

Answer 3

Indirect agonist of GABA alpha receptors
Their binding increases receptor affinity for GABA, increase frequency of channel opening
Have anxiolytics, hypnotic and muscle relaxant properties
A possible side effect in high doses is anterograde amnesia

Question 4

What is the explicit memory?

Answer 4

Facts/semantic

Events/episodic

Question 5

Define learning

Answer 5

The response of the brain to environmental events and involved adaptive changes in synaptic connectivity which in turn alter behaviour

Question 6

What is meant by wiring?

Answer 6

The way in which our neurons are connected by synaptic connections
These are plastic and malleable so can be changed

Question 7

What does Hebb say about learning and memory?

Answer 7

Cell assembly- neurons have reciprocal connections between them
External stimulus causes activation of the cell assembly
If activation of the cell assembly occurs for long enough, consolidation occurs by a growth process and the reciprocal connections are made more effective
Neurons become wired together- permanent modification of the cell assembly
If only part of the assembly is activated, the strengthened connections could cause the whole assembly to become activated.
The entire stimulus may be recognised from just part of it

Question 8

What rule of synaptic modification exist?

Answer 8

Neurons that fire together wire together

Neurons that fire out of sync lose their link

Question 9

Give the effect of stimulation of an individual hippocampal neuron before and after learning

Answer 9

May not be enough to create an EPSP great enough to fire an action potential before learning but after repetition it will elicit an AP

Question 10

What do PKC and CaMKII do?

Answer 10

Phosphorylase existing AMPA receptors, increasing their effectiveness
Stimulate the insertion of new AMPA receptors in the membrane
LTP

Question 11

What is required for long term memory?

Answer 11

Protein synthesis

Question 12

What are the characteristics of Korsakoff’s syndrome?

Answer 12

Confusion, confabulation, severe memory impairment and apathy

Question 13

What is meant by memory consolidation?

Answer 13

Converting memory into permanent form

Question 14

Evidence for role of NMDA reecptors

Answer 14

Rats given an NMDA receptor blocker fail to learn the rules of the water maze no matter how much training they receive

Question 15

How does CaMKII contribute to long-term potentiation?

Answer 15

CaMKII is an autophosphorylated protein kinase and persistant activity of CaMKII can maintain synaptic potentiation e.g keeping AMPA receptors phosphorylated

Question 16

What is the problem of phosphorylation as a long-term memory mechanism?

Answer 16

Phosphate groups lost over time therefore phosphorylation of a protein is not permanent

Question 17

What is the role of NMDA receptor in LTP?

Answer 17

Ca2+ through the NMDA receptor occurs only when the presynaptic and postsynaptic elements are active at the same time

Question 18

What does the entry of Ca2+ through NMDA receptor then cause?

Answer 18

Activation of PKC
CaMKII
Leading to phosphorylation of existing AMPA receptors, increasing their effectiveness and stimulates the insertion of new AMPA receptors into the membrane