Lecture 10- Memory disorders Flashcards
What are the two causes of amnesia?
Organic and psychogenic
What is organic cause of amnesia?
Acute damage to the brain and degenerative disease
What is psychogenic cause of amnesia?
Psychological
What are the forms of amnesia?
Retrograde and anterograde
What are the main features of the amnesic syndrome?
Pronounced anterograde amnesia (inability to encode and retrieve memories for events after)
Variable retrograde amnesia (inability to retrieve memories acquired before)
Intact STM
Preserved genetic intelligence
Skills are uneffected
Some residual learning capacity
What parts of the brain are important for memory?
Amygdala
Basal ganglia
Cerebellum
Frontal lobe
Occipital lobe
What is the amygdala implicated in?
Emotional content for episodic memories
What is the basal ganglia implicated in?
Important for learning motor skills
What is the cerebellum implicated in?
Memory for automatised skills
What is the frontal lobe implicated in?
Working memory (central executive), source monitoring and prospective memory
What is the occipital lobe implicated in?
Visul perspectiv representation memory
What happened to HM?
Bilateral removal of the medial temporal lobe and 2/3 of the hippocampus
Personality is unchanged and IQ is up
Unable to encode and retrieve new episodic memories and developed severe anterograde amnesia
What was normal with HM?
STM and learning of new procedural memories
Who looked at HM?
Squire
What did Squire find?
HM’s impairment was severe as the bilateral damage included parahippocampal and was not restricted to the hippocampus
HM had deficits in declarative memory
Who looked at the brain structures in amnesia?
Squire
What did Squire find?
Anterior hippocampus and hippocampal gyrus are concerned with the retention of current experience
Medial temporal- formation of new memories
What is Korsakoff’s syndrome?
Caused by a thiamine deficiency due to chronic alcoholism. Damage to the diencephalon. Patients appear drunk, uncoordinated and confused
What is amnesia in Korsakoff’s syndrome?
STM is normal
Encoding and retrieval of new episodic LTM is impaired
Retrograde amnesia stretches back years
Temporal gradient of retrograde amnesia
What is viral encephalitis caused by?
Herpes virus crossing blood-brain barrier
What are the characteristics of viral encephalitis?
Onset of acute fever, headache and nausea
What damage can viral encephalitis have?
Extensive bilateral temporal lobe damage
What is the amnesia in viral encephalitis?
Similar to Korsakoff
Deficits of spatial and semantic memory
Flatter temporal gradient
How common is amnesia in Alzheimer’s disease?
62%
How common is amnesia in vascular?
17%
What are the characteristics of amnesia due to dementia?
Progressive neural disease
General degeneration of the brain (atrophy due to the growth of neural plaque and tangles)
Who looked at amnesia due to dementia?
Morris and Kopelman
What did Morris and Kopelman find?
Patterns of impairments involve information processing deficits superimposed upon an amnesic syndrome
What is transient global amnesia?
Sudden onset of anterograde amnesia and retrograde amnesia
What are the characteristics of transient global amnesia?
No loss of personal identity
Anxiety
Agitated
Repetitive questioning
Rare
Recognising family members
Who does transient global amnesia effect the most?
Over 50s and more often men
What are the triggers of transient global amnesia?
Emotional upset and vigorious exercise
What evidence does amnesia provide with STM and LTM?
Dissociation between STM and LTM and the explicit and implicit
What memory does amnesia usually effect?
Episodic and semantic
What does amnesia not effect?
Normal priming effects
Motor skills
Learning of procedural skills
What are the theories of anterograde amnesia?
Faulty encoding
Accelerating forgetting
Faulty retrieval
Faulty encoding and storage of contextual information
Who looked at amnesia and encoding?
Cermak
What did Cermak find?
Amnesic deficits are due to a lack of deep encoding
Who looked at accelerating forgetting?
Huppert and Piercy
What did Huppert and Piercy find?
Patients with hippocampal lesions forget faster than controls even after material has been adequately learned
Who looked at retrieval deficits?
Kritchevsky
What did Kritchevsky find?
Transient amnesia shows tat retrieval deficits can cause amnesia and once amnesia resolves memories that were unavailable can be retrieved normally
Who looked at why retrieval deficit occur?
Warrington and Weiskrantz
What did Warrington and Weiskrantz find?
Retrieval deficit is due to response competition. Partial information helps overcome competition
Is recognition or recall impaired in retrieval deficits?
Recall
What does contextual information allow?
Distinguishing between similar memories
Who did the test of the contextual deficit theory ?
Huppert and Piercy
What did Huppert and Piercy do?
Two groups: amnesic (Korsakoff patients) and the control
Presented a set of pictures on day 1 and a set of pictures of day 2
Some were presented on both days
Recognition test after the day 2 pictures
Both groups asked to do 2 tasks: asked if they have ever seem recognition and then day 2 recognition if the pictures had been seen only on day 2
What are the problems of the contextual deficit theory?
Semantic memories can be impaired
Definition of context is vague
Context processing deficit s vary substantially across patient groups (Squire)
What is Ribot’s law of retrograde amnesia?
Recent memories are more likely to be lost
What is temporal gradient due to?
Slow scale consolidation processes as earlier memories have had longer to be consolidated
Who did the standard consolidation theory?
Dudai
What is the standard consolidation theory?
Episodic memories are initially encoded and stored in the hippocampus and retrieval of the memories require reactivating of the hippocampus
Overtime the hippocampal memory trace becomes less important and the cortex can retrieve the memory without the hippocampus
Older memories are spared in retrograde amnesia
What are the types of psychogenic amnesia?
Fugue states and dissociative amnesia
What are the fugue state triggers?
Severe stress, depressed mood, history of transient organic amnesia (Kihlstrom and Schacter)
How long does psychogenic amnesia last?
A few hours or days
What happens after recovery from fugue states?
All the memories are lost
What does dissociative types of psychogenic amnesia?
Refers to loss of memory for specific events due to trauma with no anterograde amnesia
What is amnesic syndrome associated with (Baddeley)?
Amnesic syndrome is associated with damage to the temporal lobe, hippocampus or mamillary bodies
