W6L2 - Neuroanatomy & Biochemistry of Memory Flashcards
What are extra-temporal connections to the MTL
- Papez Circuit
- Frontal Lobes
- Dienecephalon
What is the Limbic System and what does it regulate
Limbic System = Amygdala + Papez Circuit
- Emotional expression and experiences
What is the role of the Amygdala in memory? What happens if it’s leisoned?
Role of Amygdala
- Memory for emotionally arousing experiences (Not necessarily fear)
- Fear conditioning
- Rich representations of emotional experiences
Lesioned
- Loss of conditioned fear
- Impairment of new fear learning
- Reduced memory for emotionally laden events (Not necessarily fear)
What are the parts of Papez Circuit (in order)
- Hippocampus
- Fornix
- Mamillary Body - Part of Hypothalamus
- Anterior Thalamus Nuclei - Part of Thalamus
- Cingulate Gyrus
[Closed Circuit]
What is the role of the Papez Circuit in memory? Lesion to which part is memory most reliably imparied?
Declarative Memory
General View
- Relational memory/encoding, similar to MTL
- Most reliable when hippocampus or ATN are leisoned. But other parts also cause relational damage
- Damage tend to be spread anyways
What does the Frontal Lobe contain
- Posterior Frontal Lobe
- Motor and premotor cortex
- Motor programming
- Anterior Frontal Lobe
- Prefontal cortex
- Cognitive Control Processes
Leision of Frontal Lobes in Memory
- Impairment in developing and implementing strategies for appropriate memory encoding and retrieval
- Impairment in remembering contextual details (DLPFC)
- E.g., Sources of information, chronological order of memories
- Confabulation (VLPFC)
- Production of statements involving bizarre distortions of memory
Where are the rich connections in frontal lobes connected to
Rich reciprocal connections:
- ) Within frontal lobes itself
- ) With MTL (hippocampus, neocortical association areas, etc)
(With hippocampus via fornix)
What is the Dienecephalon
Dienecephalon = Thalamus + Hypothalamus
What does the hypothalamus contain? Hence?
- Mamillary bodies (In Papez Circuit)
- Impairment = loss of declarative memory (relational)
What does the thalamus contain
- ATN (Papez Circuit)
- Mammillo-thalamic tract (MMT): Connects ATN with hipocampus
- Medio Dorsal Nuclei (MDM) / Dorsal Medial Nuclei
- Internal Medullary Lamina (IML) / Midline
Which parts of leisons of thalamus most likely to cause memory loss
Anterior and Medial
- More likely
- Most connected to frontal lobes
- Anterior (part of Papez circuit)
- Medial
Posterior and Lateral
- Less likely
Damage of mammillo-thalamic tract (connects ATN to hippocampus) and ATN
Declarative (Relational memory)
Damage of Medio Dorsal Nucleus (MDN) and/or Internal Medullary Lamina (IML) damage; but spared mammillo-thalamtic tract (MTT)?
Specific retrieval difficulties
- Impaired Recall
- Preserved Recognition
- Top Down cannot recall, but can recall under prompt
Damage of Medio Dorsal Nucleus (MDN) and Intralaminar/Midline Nucleus?
Medio Dorsal Nucleus
- Deficits in selecting the appropriate information to be retrieved
- ‘Active retrieval’
Intralaminar/Midline
- Deficits seen in semantic memory, memory retrieval
Evidence for LTP
- Baseline EPSP measured for single electrical stimulus
- 100 electrical stimuli delivered rapidly
- Increased EPSP for subsequent single electrical stimulus
- LTP
Biochemically, how does LTP cause synaptic changes? Describe the changes at the level of the pre and post-synaptic
(Glutamate)
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
