Lec9: Long Term Depression (LTD)

Question 1

Why are three reasons that it is important to be able to decrease synaptic plasticity, not only increase it?

Answer 1

1. Prevents saturation (because LTP is saturable) - Therefore, prevents loss of plasticity
2. Creates dynamic short-term memory - because it can be continually made and replaced quickly
   3.

Question 2

How is LTD induced?

Answer 2

Low Frequency Stimulation, leading to small Ca2+ influx which activates protein phosphatases.

Question 3

What is LFS numerically?

Answer 3

Stimulation at frequency 1Hz for 5-10 minutes.

Question 4

What factor determines whether LTP or LTD is induced?

Answer 4

Level of Ca2+ influx:

1. > 5micromoles = LTP
2. 1micromole = LTD

Question 5

What do protein phosphatases do?

Answer 5

Dephosphorylate AMPAR, so they are removed form post-synaptic membrane and therefore postsynaptic current is decreased.

Question 6

Through what process are AMPAR removed from postsynaptic membrane?

Answer 6

Endocytosis.

Question 7

What were the two types of LTP discovered in live animals? Draw a graph.

Answer 7

Decremental + Stable.

Question 8

List and describe all 7 pieces of evidence for the existence of LTP/LTD.

Answer 8

1. Inducable by in vivo stimulation paradigms
2. Robustly expressed in major memory+learning pathways
3. Drugs blocking LTP/LTD in slices block learning in live animals
4. Enhancing synapses increases learning ability
5. In vivo recordings of synaptic plasticity (NMDAR moving into synaptic membrane during learning)
6. Drugs that rescue plasticity also rescue memory
7. Learning+memory deficits also present with synaptic plasticity deficits