W6L2 - Neuroanatomy & Biochemistry of Memory

Question 1

What are extra-temporal connections to the MTL

Answer 1

1. ) Papez Circuit
2. ) Frontal Lobes
3. ) Dienecephalon

Question 2

What is the Limbic System and what does it regulate

Answer 2

Limbic System = Amygdala + Papez Circuit

Regulates emotional expression & experience

Question 3

What is the role of the Amygdala in memory. Some examples

Answer 3

Emotionally arousing experiences (Joy? Fear?)

– Classical fear conditioning

Question 4

Leision of Amygdala in Memory

Answer 4

• Loss of conditioned fear and impairment of new
  fear learning
• Reduced memory for emotionally laden events

Question 5

What is the role of the Papez Circuit in memory.

Answer 5

Declarative Memory

Question 6

What are the parts of Papez Circuit (in order)

Answer 6

1) Hippocampus >
2) Fornix >
3) Mamillary Body (part of Dienecephalon Hypothalamus ) >
4) Anterior Thalamus Nuclei (part of Dienecephalon Thalamus) > Cingulate Gyrus

Closed Circuit

Question 7

Leision of Papez Circuit in Memory

Answer 7

Declarative memory impairment (esp. poor relational

memory/encoding)

Question 8

Where is leision of Papez Circuit most servere

Answer 8

When hippocampus or Anteior Thalamus Nuclei (ATN) are lesioned

Question 9

What is the role of the Frontal Lobes in memory.

Answer 9

• Developing and implementing strategies for appropriate memory ENCODING and RETRIEVAL

Question 10

Leision of Frontal Lobes in Memory

Answer 10

1.) Impairment in developing and implementing strategies for appropriate memory
ENCODING and RETRIEVAL

2.) Impairment in remembering contextual details e.g.
source of information, chronological order of
memories (DLPF)

3.) Confabulation – production of statements involving
bizarre distortions of memory

Question 11

What does the Frontal Lobe contain

Answer 11

Posterior Frontal Lobe: Motor Cortex (Motor & Premotor)

Anterior Frontal Lobe: Cognitive Control Processes (PFC)

Question 12

Where are the rich connections in frontal lobes connected to

Answer 12

Rich reciprocal connections:

1. ) Within frontal lobes itself (DLPFC, AFPC, VLPFC, MPFC)
2. ) With MTL (hippocampus, neocortical association areas, etc)

Question 13

What is the Dienecephalon

Answer 13

Dienecephalon = Thalamus + Hypothalamus

Question 14

What does the hypothalamus contain. And hence?

Answer 14

Mamillary bodies (Also in Papez Circuit)

Hence, impairment = loss of declarative memory (esp. relational)

Question 15

What does the thalamus contain.

Answer 15

ATN (Papez Circuit)
Medio Dorsal Nuclei (MDM)
Internal Medullary Lamina (IML)

Question 16

Which parts of leisons of thalamus most likely to cause memory loss

Answer 16

Anterior and Medial more likely. Posterior & Lateral less likely

Question 17

Damage of mammillo-thalamic tract (connects anterior thalamus to hippocampus)

Answer 17

Amnesic Type - Relational memory

Question 18

Damage of Medio Dorsal Nucleus (MDN) and/or Internal Medullary Lamina (IML) damage; spared mammillo-thalamtic tract (MTT)

Answer 18

Specific retrieval difficulties (preserved recognition) - Top Down cannot recall, but given prompt can.

Question 19

Damage of Medio Dorsal Nucleus (MDN)

Answer 19

Deficits in selecting the appropriate information to be retrieved – ‘Active retrieval’

Question 20

Damage of Intralaminar/Midline

Answer 20

Deficits also in selecting appropriate information, but more so seen in semantic memory

Question 21

Summary of leisions of the 3 areas

Answer 21

1.) Papez’s circuit lesion => impaired relational
memory/encoding (hippocampal type of amnesia)

2. ) Frontal Lobes => impaired ability to organise the encoding, retrieval and maintenance of memories
3. ) Dorso-medial, intralaminar and midline nuclei => impaired memory due to reduced mental flexibility and inappropriate selection of information retrieval

Question 22

Biochemistry: What does learning require

Answer 22

Synaptic Plasticity

Question 23

What is synaptic plasticity

Answer 23

Biochemistry of synapses change to alter the

effect on post-synaptic neuron

Question 24

What is LTP

Answer 24

Long-term increase in excitability of a neuron to a particular synaptic input caused by repeated high
frequency activity of that input

Question 25

What is Hebb’s Law

Answer 25

When an axon of cell A…excites cell B by repeatedly firing it, change takes place in 1/both cells to increase A’s efficiency

Question 26

Evidence for LTP

Answer 26

1.) Baseline EPSP measured for single electrical stimulus
2.) 100 electrical stimuli delivered rapidly
3.) Increased EPSP for subsequent single
electrical stimulus (LTP)

Question 27

Biochemically, how does LTP cause synaptic changes?

Answer 27

Pre-Synaptic:
- Increased glutamate by pre-synaptic terminal button

Post-synaptic

• New receptors
• Increased receptor sensitivity to glutamate
• Increase protein synthesis in post-synaptic dendrites

Question 28

Where does synaptic change occur

Answer 28

1. ) Hippocampal Formation: Hippocampus (esp. dentate gryus + CA1), entorhinal cortex
2. ) Others: Frontal Lobes, Thalamus, Amygdala, Visual Cortex

Question 29

What are 3 other mechanisms of neural plasticity

Answer 29

1. ) Long term depression
2. ) Habituation
3. ) Sensitization

Question 30

How does Long Term Depression affect neural plasticity

Answer 30

Low frequency stimulation at synapse decrease synaptic strength

Question 31

How does Habituation affect neural plasticity

Answer 31

Repeated stimulation reduces strength of synaptic response via. reduced NT release

Question 32

How does Sensitization affect neural plasticity

Answer 32

Single noxious stimulus causes exaggerated synaptic response to repeat presentation of noxious stimulus