MVC - Memory II

Question 1

What is Hebb’s postulate, and how does it relate to memory?

Answer 1

When an axon of cell A is near enough to excite cell B or repeatedly or consistently takes part in firing it, some growth or metabolic change takes place in one or both cells such that A’s efficiency, as one of the cells firing B, is increased

Hebb’s postulate states that the activity of interconnected neurons strengthens the connections between them

Question 2

What did hippocampal studies show?

Answer 2

Experiments show that there exists at least one group of synapses in the hippocampus whose efficiency is influenced by activity which may have occurred several hours previously - a time scale long enough to be potentially useful for information storage

Question 3

How does the hippocampus process information differently from sensory cortices?

Answer 3

Unlike sensory cortices that receive raw sensory input, the hippocampus receives highly processed information from various brain regions

• This allows it to integrate and understand relationships between different types of information.

Question 4

What are the subfields of the hippocampus, and how do they contribute to memory? (4)

Answer 4

The hippocampus has several subfields, each playing a role in processing high-level information:

• Dentate gyrus (DG): Involved in initial information processing and pattern separation.
• Subiculum (Sub): Connects the hippocampus to other brain regions.
• CA3: Integrates information from various sources.
• CA1: Outputs processed information to other brain regions for memory consolidation.

Question 5

How does hippocampal plasticity enable memory formation?

Answer 5

Hippocampal plasticity refers to its ability to change and adapt. This allows it to form new memories through:

• Associations: Linking different pieces of information.
• Long-term potentiation (LTP): Strengthening synapses based on activity patterns, thought to be a cellular mechanism for memory storage.

Question 6

What is long-term potentiation in the CA3-CA1 region of the hippocampus?

Answer 6

LTP is a strengthening of synapses based on recent patterns of activity, and is considered a cellular mechanism underlying memory and learning

Question 7

What can prevent LTP?

Answer 7

A selective NMDAR antagonist (APV, D-AP5) prevents LTP.

Question 8

What is the role of NMDA receptors in LTP?

Answer 8

NMDA receptors are crucial for LTP.

• They act as coincidence detectors, requiring both glutamate binding and removal of magnesium block for activation

This ensures only strong, synchronized activity triggers LTP.

Question 9

How do mossy fiber-CA3 synapses contribute to memory encoding?

Answer 9

Mossy fiber-CA3 synapses exhibit pronounced short-term plasticity (facilitation).

Multiple stimuli in quick succession (bursts) can trigger action potentials in CA3 neurons, even if single stimuli cannot. This allows for efficient information coding and storage.

Question 10

What is “full detonator mode” and its potential role in memory?

Answer 10

After high-frequency stimulation, mossy fibers might enter a “full detonator mode” for a short time.

• This increased excitability might be critical for efficient processing and storage of information in the hippocampus.