Synaptic Plasticity

Question 1

How are memories stored?

Answer 1

Through changes in synaptic strength (synaptic plasticity).

Question 2

What is synaptic plasticity?

Answer 2

The ability of synapses to strengthen or weaken based on activity.

Question 3

What does “fire together, wire together” mean?

Answer 3

Neurons active at the same time strengthen their synaptic connections.

Question 4

What is LTP?

Answer 4

Long-lasting strengthening of synapses after high-frequency stimulation.

Question 5

Where is classic LTP studied?

Answer 5

CA3 → CA1 synapse in the hippocampus.

Question 6

What happens to EPSPs after high-frequency stimulation?

Answer 6

EPSPs become larger at the stimulated synapse.

Question 7

Is LTP input specific?

Answer 7

Yes, only the active synapse is strengthened.

Question 8

What is cooperativity in LTP?

Answer 8

Multiple weak inputs can combine to trigger LTP (spatial summation).

Question 9

What is specificity in LTP?

Answer 9

Only synapses active during depolarization are strengthened.

Question 10

What do AMPA receptors require?

Answer 10

Glutamate; allow Na+ and K+ flow.

Question 11

What do NMDA receptors require?

Answer 11

Glutamate + depolarization to remove the Mg2+ block.

Question 12

Why is NMDA a coincidence detector?

Answer 12

It opens only when glutamate binds AND the membrane is depolarized.

Question 13

What ions enter through NMDA receptors?

Answer 13

Na+, K+, and Ca2+.

Question 14

Why is Ca²⁺ important for LTP?

Answer 14

Ca²⁺ activates kinases that strengthen synapses.

Question 15

How does Ca²⁺ strengthen synapses?

Answer 15

Increases AMPA receptor conductance and inserts more AMPA receptors into the membrane.

Question 16

What happens if NMDA receptors are blocked?

Answer 16

LTP cannot occur and learning is impaired.

Question 17

Does increasing NMDA receptors improve memory?

Answer 17

Yes, it enhances learning.

Question 18

What is LTD?

Answer 18

Long-lasting weakening of synapses caused by low-frequency stimulation.

Question 19

How does LTD occur?

Answer 19

Small, slow Ca²⁺ influx activates phosphatases that remove AMPA receptors.

Question 20

Is LTD input specific?

Answer 20

Yes, only the synapse receiving low-frequency signals is weakened.

Question 21

What does “out of sync, lose your link” mean?

Answer 21

Asynchronous firing leads to synaptic weakening (LTD).

Question 22

What is STDP?

Answer 22

A form of plasticity determined by timing of pre- vs postsynaptic spikes.

Question 23

What happens if presynaptic fires BEFORE postsynaptic?

Answer 23

LTP (the input contributed to firing).

Question 24

What happens if presynaptic fires AFTER postsynaptic?

Answer 24

LTD (the input did not contribute).

Question 25

What determines LTP vs LTD?

Answer 25

The amount and timing of Ca²⁺ influx.

Question 26

What triggers LTP?

Answer 26

Large, fast Ca²⁺ influx and activation of kinases.

Question 27

What triggers LTD?

Answer 27

Small, slow Ca²⁺ influx and activation of phosphatases.

Question 28

Where is most studied plasticity found?

Answer 28

The hippocampus, especially CA3→CA1.