Recitation Week 6 Study Part 1

Question 1

When it comes to memory and the flow of axons stimulated, put the following in order:

DG - dentate gyrus
CA1 pyramidal cells
CA3 pyramidal cells
EC - entorhinal cortex
Mossy Fibers
Schaeffer Collaterals
Perforant Path

Answer 1

1) Entorhinal cortex
via the 2) Perforant Path
3) Stimulates the Dentate Gyrus
which via the 4) Mossy Fibers
5) Stimulates the CA3 pyramidal cells
which via the 6) Schaeffer Collaterals
7) Stimulates the CA1 pyramidal cells

Question 2

Which parts of the above reside in the hippocampus?

Answer 2

DG, CA3, CA1, Mossy Fibers, Schaeffer Collaterals

Question 3

Which of the above are the primary output cells of the Hippocampus?

Answer 3

CA1 pyramidal cells which have extensive connections to the striatum

Question 4

If you were to stimulate a Schaeffer collateral, where would you place the recording electrode?

Answer 4

In the CA1 pyramidal neurons which are downstream in synapse 3 of the perforant path

Question 5

which of these is NOT an axon bundle in the trisynaptic circuit?
a) mossy fibers
b) perforant path
c) Schaeffer collaterals
d) pyramidal path

Answer 5

d) pyramidal path

Question 6

Describe the 6 steps of Memory Retrieval

Answer 6

1) Repeated behavioral/sensory experience
2) Creates a weak stimulation of pre-synaptic neurons
3) Which creates Glu release
4) Which allows more AMPA receptors to let in more Na+
5) Which creates a larger EPSP in the post-synaptic neuron
6) Which leads to a stronger memory and memory retrieval

Question 7

What is LTP?

Answer 7

Neurons responding more strongly to the same stimulus due to more AMPA receptors which cause greater Glu sensitivity

Question 8

Describe the 6 steps in Memory Acquisition

Answer 8

1) Behavioral/sensory experience
2) Weak stimulation of pre-synaptic neurons (with the pre/post synaptic neurons creating an engram)
3) Glu is released
4) AMPA receptors let in Na+
5) EPSP is created in post-synaptic neuron
6) Short term memory is acquired

Question 9

Describe the 8 steps of Memory Consolidation

Answer 9

1) A behavior/sensory experience is repeated
2) This creates a strong stimulation of pre-synaptic neurons
3) Which increases Glu release
4) Which allows AMPA receptors to allow more Na+
5) Which results in NMDA receptors letting in Ca2+ and more Na+
6) The Ca2+ activates protein kinases
7) Protein kinases add more AMPA receptors to the post-synaptic dendrite
8) Which leads to Long Term Memory

Question 10

Describe the 7 steps of Long-Term Depression

Answer 10

1) Repeated weak/moderate stimulation of pre-synaptic neuron
2) Which slightly increases Glu release
3) Which allows the AMPA receptors to let in some (but less) Na+
4) Which allows NMDA receptors to let in some (but less) Ca2+ and some (but less) Na+
5) With the lesser Ca2+ concentrations activating protein phosphatases
6) Which cause protein phosphatases to remove AMPA receptors from the post-synaptic dendrite
7) Which leads to memory loss/depression

Question 11

Which will not occur in the opening of NMDA receptors?
a) hyperpolarization of postsynaptic neuron
b) Glu binds to NMDA receptor
c) Glu binds to AMPA receptor, Na+ enters postsynaptic cell
d) Depolarization of postsynaptic neuron

Answer 11

a) hyperpolarization of the postsynaptic neuron

Hyperpolarization, which would make the inside of the neuron more negative compared to the outside, does not facilitate the opening of NMDA receptors. Instead, depolarization is required to remove the block and allow the receptor to conduct ions.

for b, c and d:

b) Glu binds to NMDA receptor: Glutamate (Glu) binding to the NMDA receptor is a critical step for the receptor’s activation. However, for NMDA receptors to open, the postsynaptic neuron must be depolarized to remove the Mg2+ block from the receptor channel.

c) Glu binds to AMPA receptor, Na+ enters postsynaptic cell: This is a precursor event to the activation of NMDA receptors. The binding of glutamate to AMPA receptors causes them to open, allowing Na+ to enter the postsynaptic cell, leading to depolarization. This depolarization is necessary for the activation of NMDA receptors by removing the Mg2+ block.

d) Depolarization of the postsynaptic neuron: This is a crucial step for the activation of NMDA receptors. The depolarization, often initiated by the activation of AMPA receptors, removes the Mg2+ ion that blocks the NMDA receptor channel in a voltage-dependent manner, allowing for the influx of Ca2+ and other ions when glutamate is bound to the NMDA receptor.