Why is memory important?
- Adaptive behaviour.
- Self-identity.
- Practical important of memory failures
Autobiographical Memory: gives rise to our self-identity, eroded in AD
Describe a simple model of memory.
How do you encode Long Term Memory?
- The way you encode information is quite key to establishing how likely you are to forget it later.
When you process things in a meaninful fashion you are more likely to remember it.
- Can encode using physical, acoustic and semantic means.
- Semantic encoding provides more powerful and distinctive cues for later recall - reduces interference.
Interference is when you can’t retrieve information from LTM because of interference from other similar memories.
What is context dependency in long term memory?
Doctors explain things to patient in a hospital but they forget it, or forget to apply it - because they encode the information in a different setting. (hospital vs home).
i.e. Divers learn list of words on land or under water, and then recall on land or under water.
Mood Dependency: Depressed Mood -> Recall Upsetting Events -> Sad thoughts -> Depressed Mood
Why do we forget Long Term and Short Term Memories?
Short Term Memory
- Things ‘slip out’ over time when we are distracted (decay and displacement).
Long Term Memory
- Cues are ineffective - can’t access the memory.
- Many similar memories that cues don’t seperate - interference.
- Involuntary memory following a good match between encoding and retrieval state.
What are the common causes of amnesia?
Common Causes
- Viral Infections (especially herpes simplex encephalitis)
- Long-term alcoholism: Korsakoff’s syndrome.
- Anoxia (cardiac arrest, carbon monoxide poisoning).
- Head Injury.
- Alzheimer’s disease.
All Associated with damage to medial temporal lobes
What areas of the brain are associated with memory damage?
Hippocampus most famous in long-term memory but not isolated in forming long term memory.
Para-hippocampal cortex encodes spatial memory and talks to hippocampus all the time.
Fornix = a major output of the hippocampus.
If it’s damaged as a result of a road traffic accident then you can have amnesia.
Give an example of somantic information
Changing your name after getting married
What is anterograde amnesia?
Anterograde amnesia - stuff that happens after the briain damage. i.e. the patient can’t remember his wife being in the room.
This is important because we need to understand that not all long term memories are dependant on the hippocampus.
There is a theory that information (LTI) is transferred from the hippocampus to the cortex over time.
This could happen during sleep.
What information is preserved in amnesia?
Semantic information - people with amnesia have normal results on tests such as in naming definitions, naming pictures, understanding sentences.
Conclusion: hippocampus is not the final store of knowledge.
Semantic memory is factual knowledge.
Also preserved in amnesia: Non-declarative memory
- In fact, not all long term learning is disrupted in amnesia - some long term learning is spared.
- One patient was able to learn procedural memory (motor stuff).
- This further demonstrates that the hippocampus isn’t required for long term memory.
Memories that are declarative or explicit - that’s a conscious form of memory. These are memories that you can actually talk about. They are based on your conscious experience.
Concious memory is episodic and semantic memory.
Only episodic memory is really impaired.
Give an overview of how these memory systems are interlinked/
Describe the role of the hippocampus in memory formation.
If you want to create an episodic memory you need to know where you were, what happened, who you were with. (i.e. place, object, people). Hippocampus involved in long-term potentiation.
Why are childhood memories spared in amnesia?
Childhood memories and facts are stored in neocortex around hippocampus.
Explain how Semantic Dementia causes damage.
- People with semantic dementia have atrophy quite focused in the frontal lobes.
- Progressive loss of conceptual knowledge - they don’t know what words mean anymore, difficulties recognising objects and faces.
What memories are intact in patients with semantic dementia?
- Memory for recent events.
- Phonology/syntax.
- Visual-spacial skills.
- Non-verbal reasoning.
What is the nature of memory loss in patient’s with semantic dementia?
- People with amneisa have a temporal gradient and have particular difficulties in forming new memories, that’s the same in AD.
But in patients with somantic dementia, you get reverse - they can tell you what happened recently but its their childhood memories which are most disrupted in somantic memory, because of damage to neo-cortical memory stores.
What are the two types of LTM stores?
Hippocampus
- Episodic memory
- Unique episodes involving people/places/objects
- Damaged in dementia.
Anterior Temporal Lobes
- Semantic memory
- Similarities between experiences to form concepts
- Damaged in smenatic dementia.
