NB14-3 - Memory and Amnesias

Question 1

Describe the two types of memory

Answer 1

Declarative (explicit) - rembering facts and events; conscious memory

Procedural (implicit) - rembering skills/habits, conditioning; unconscious memory

Question 2

Describe the stages of memory. Include the terms used to describe movement from one stage to another.

Answer 2

1. Sensory memory
2. Short-term (working) memory
3. Long-term memory

The sensory memory receives the initial sensory input. If we pay attention to that information it gets moved to short-term memory. Rehearsal of that information helps to keep it in the short-term memory longer and encode it for storage in long-term memory so that later it can be retrieved for use. The more that information is rehearsed, encoded, and retrieved, the more it becomes consolidated in the long-term memory.

Question 3

List and describe the different amnesias

Answer 3

• Retrograde - can’t remember anything for a period of time just before the injury, but can steadily remember more and more the further back you go until complete recall is possible. No issues with memory after the trauma has been resolved
• Anterograde - can remember fine before the trauma but can’t remember anything after the trauma
• Infantile - early childhood events cannot be recalled
• Transient Global - temporary but almost total disruption of short-term memory
• Dissociative - psychological reaction
• Wernicke-Korsakoff (diencephalic) - caused by thaimin deficiency; symptoms include confusion, confabulation, and sever memory impairment
  *

Question 4

Answer 4

A

Question 5

Describe the synaptic plasticity that takes place to form short-term and long-term memory.

Answer 5

Short-Term - transient changes in synaptic function

Long-Term - more permanent alteration of cellular function

Both lead to a strong relationship between neuronal firing.

Question 6

Answer 6

Question 7

List the components of the hippocampal trisynaptic circuit we need to know. What is the purpose of this pathway?

Answer 7

1. Sensory stimuli information synpases in the entorhinal cortex
2. Information is then carried via the perforant pathway to synapse on the dentate gyrus
3. Information is then carried via the mossy fibers to synapse on the CA3 pyramidal cells
4. Information is then carried via the schaffer collaterals to synapse on the CA1 pyramidal cells
5. Information is then carried via the subiculum back to the entorhinal cortex

This pathway generates synaptic plasticity for memory formation

Question 8

What is the standard consolidation theory of memory formation?

Answer 8

The hippocampus causes two areas of the brain to fire together which is essentially memory (ie - the visual cortex perceives a drawn circle and the area of your brain that knows what a circle is also lights up). After enough instances of these two areas firing together, the hippocampus is no longer required for them to fire together (due to plasticity) and this is thought to be how a short-term memory is consolidated into long-term memory.

Question 9

Answer 9

B

Question 10

Describe how LTP occurs in both the short-term and long-term.

Answer 10

If a neuon has a high AP frequency, the increase in Ca++ influx at the synaptic terminal will lead to the activation of 2nd messenger pathways that will cause:

• An increase in AMPA receptors and AMPA channel conductance which will make it easier for that neuron to have an AP in the short term
• An increase in the number of new synapses via formation of new dendritic spines and increased synatpic boutons which will make it easier for that neuron to have an AP in the long term
• This will also cause release of retrograde messengers which will stimulate release of more NT from the presynaptic neuron

Question 11

Answer 11

A

Question 12

Describe how long term depression occurs and why it is important.

Answer 12

It essentially is the opposite of LTP

While it is important for memory for some neurons to fire together, it is also important for other neurons not to fire together.