Long-term potentiation (LTP) and long-term depression (LTD)
In this lesson, we'll cover two mechanisms that play critical roles in synaptic plasticity (and memory): long-term potentiation and long-term depression.
1) Start with these videos:
2) Next, answer these questions to test your understanding:
1. In NMDA receptor-dependent long-term potentiation (LTP), activation of NMDA receptors leads to an increase in the number of which type of receptor at the postsynaptic membrane?
- A. GABA-A receptors
- B. NMDA receptors
- C. AMPA receptors
- D. dopamine receptors
Show Answer
Correct answer: C
In NMDA receptor-dependent LTP, calcium influx through activated NMDA receptors initiates signaling cascades that promote the insertion of AMPA receptors into the postsynaptic membrane, enhancing synaptic strength.
2. NMDA glutamate receptors are involved in long-term potentiation (LTP), but their ion channels are blocked by this type of ion until depolarization causes the blockade to be removed:
- A. potassium
- B. magnesium
- C. sodium
- D. chloride
Show Answer
Correct answer: B
NMDA receptors are not activated by low levels of glutamate release because the ion channel of an NMDA receptor is typically blocked by a magnesium ion. If frequent action potentials cause greater depolarization of the neuron, however, the magnesium blockade is removed, allowing calcium ions to flow in through the NMDA receptor.
3. Which of the following best describes the meaning of the term long-term depression (LTD) in neuroscience?
- A. A long-lasting decrease in serotonin levels
- B. A long-lasting decrease in synaptic strength
- C. The inability of neurons to fire action potentials after prolonged stimulation
- D. A progressive loss of neurons in the hippocampus with aging
Show Answer
Correct answer: B
LTD is a process by which synaptic connections between neurons become weaker. It is the opposing process to long-term potentiation. Although the functions of LTD are not completely understood, it’s thought to be important to memory formation, perhaps by resetting previous synaptic changes to allow for new memories to be formed via long-term potentiation.
4. The most well-characterized mechanism underlying long-term depression (LTD) involves the removal of which receptors from the neuronal cell membrane?
- A. NMDA receptors
- B. GABA_A receptors
- C. AMPA receptors
- D. Dopamine D1 receptors
Show Answer
Correct answer: C
During long-term depression (LTD), AMPA receptors are removed from the postsynaptic membrane, which reduces the strength of synaptic transmission. This trafficking is a key cellular mechanism for weakening specific synapses and is central to synaptic plasticity and learning processes.
