Lecture 18 - Amnesia Flashcards
What is amnesia and its consequences?
- Disorder of memory with preserved intellect and language
- Difficult to maintain job/relationships
What are the two types of amnesia?
- Anterograde: a problem in encoding, storing or retrieving info that can be used in the future (making new memories)
- Retrograde: A problem accessing events that happened in the past
What causes Amnesia?
- Alzheimers: most common cause. Not pure form because it becomes complicated with other symptoms of dementia (gradual)
- Korsakoff Syndrome: Chronic alcoholism = pure form of amnesia (gradual)
- Herpes simplex encephalitis: virus of brain e.g Clive Wearing (distinct)
- Temporal lobe surgery: amnesia occurs because of deliberate surgery procedures
What happened to HM?
- Epilepsy at 10
- Removal of Medial Temporal Lobes including hippocampus
- No more seizures but bad memory problems
- Anterograde deficit is extremely severe
- Retrograde deficit extends back to 16
What was preserved in amnesia?
- STM: digit span
- Procedural memory: mirror drawing task
- Implicit memory: behaviour is influenced by prev experience despite not being consciously aware of it e.g doctor shook hands with amnesia patients everyday, one day it hurt, patient next day refused to shake hands without knowing why
- Can give people degraded pictures of words = quicker recall when presented again
- Study where ppts were given a list of words to read and asked either to recall word (explicit) or generate first word that comes to mind (implicit). Explicit = impaired
How is episodic memory measured?
- Free recall/recognition
- Dual process: Familiarity (without context) and recollection (with context)
What was a study on John?
- Had anoxia: damage to hippocampus due to lack of oxygen
- Performs same as controls in recognition, but recall is substantially impaired
- Used Remember/Know categories as much as controls but had no justification for remember responses = used strength responses instead (how strong memory is)
- Issue of recollection not familiarity
What about other hypoxic patients?
- Greater deficit in recall
- Recollection is impaired
What did Aggleton propose?
- Hippocampus used for recollection
- Perirhinal region used for familiarity
- Dispute that there are 2 processes or if it just strong/weak memory processes
What tests were used to test retrograde amnesia?
- Test range of events e.g news/horse races
- Probe method: recall personal memory and then date it based of a cue
- Autobiographical Memory Interview: ask ppt to remember specific info from a range of time periods & recollect specific personal event from the period
What is Ribot's Law?
- Memories from earlier in life are easier to recall
- PZ had acute onset of amnesia and found recall worsened after years
- Temporal gradient found
What are explanations of retrograde amnesia?
- Standard consolidation models: assume info is consolidated by transferring it from one brain region to another = accounts for Ribot's Law
- Areas of memory activate different cortexes e.g emotion is in a particular cortex and hippocampus coordinates this.
- When consolidated, hippocampus replays activity in cortexes, more consolidated = cortexes are connected = no hippocampus needed for earlier memories
- Multiple-Trace hypothesis: assumes hippocampus is important for encoding and long-term retrieval
- Long-term consolidation results in redundant traces in hippocampus = multiple replicas of earlier experiences = older memories have more traces = okay against partial hippocampal damage
What about Semantic memory in amnesia?
- In dementia: deficits in semantic memory
- Retrieve lexical knowledge using spelling and irregular word forms = performed 1 SD of matched controls
- New semantic knowledge: new words introduced since onset of amnesia = unable to define
- Amount of damage to MTL = magnitude of deficits in acquiring new semantic info
- Can learn new info when anchored to previously acquired knowledge
