7- Acquired Brain Injury Flashcards
What surgery did HM have?
Temporal lobe bilateral surgery
What did HM’s surgery not affect?
Remained of normal intelligence and had no psychological illness
What did HM’s surgery negatively result in and what did this mean?
Intense anterograde amnesia- destroyed ability to form new memories and recognise new people
What did studying HM show us?
There are separate memory forms
3 things that weren’t affected by HM’s surgery
Working memory, old and new procedural memory, facts/events from before damage
What memory was affected by HM’s surgery?
New facts/events memory
What amnesia was caused by HM’s surgery and what did this show?
Severe anterograde amnesia showing the hippocampus is critical for forming new memories
What type of processing is there that shows that the hippocampus provides a high-level brain function?
Lots of visual processing until any sensory info reaches the hippocampus
Where do other senses show a complex processing similar to visual processing?
Upstream of the hippocampus
Why are high-level brain areas expected to be very difficult to understand?
Due to responses being very complex
Who discovered place cells in the hippocampus in 1971?
O’Keefe and Dostrovosky
When do place cells fire?
When an animal is in a specific space region
What do multi-electrode recordings show?
That place fields of these cells provide a spatial ‘map’
Which lesions impair spatial navigation?
Dorsal hippocampal lesions
What do hippocampal place cells provide?
Spatial context for a memory
What did Maguire et al (2000) find?
London taxi drivers have a larger posterior hippocampus compared to experience-matched bus drivers
How did experience relate to brain structure (Maguire et al, 2000)?
More experience means a larger posterior hippocampus
What does the hippocampus bind and support?
Binds together different aspects of an event and supports recollection
Who suggested the Relational Theory of Hippocampal Function?
Cohen & Eichenbaum, 1993
How is an ‘episode’ (memory) formed according to the Relational Theory of Hippocampal Function?
Hippocampus supports ‘binding together’ of all perceptually and conceptually distinct aspects and elements that make up the memory
What does hippocampal damage tell us about memory?
There are dissociable systems
What is the hippocampus crucial for?
Forming new memories
What is the hippocampus not crucial for?
Recall of older memories
How is the hippocampus shown to be crucial for certain functions but not for others?
Anterograde not retrograde amnesia observed
Memories needing to be ‘consolidated’ and hippocampal-independent over time shows what?
Memories are stored elsewhere in the brain
Which brain structure acts as a ‘relay station’ in memory formation?
Thalamus
Where is the thalamus located?
Near centre of the brain
How do nerve fibres project out of the thalamus?
In all directions
What brain structure does the thalamus have many connections to?
The hippocampus
What other brain structure is the thalamus densely connected to?
The cerebral cortex
What is the thalamus thought to be critical for?
Information transfer from hippocampus to cortex
How is Korsakoff’s syndrome caused?
By thiamine deficiency due to alcoholism
What does Korakoff’s syndrome result in?
Thalamus damage
What does Korsakoff’s syndrome suggest about the thalamus?
It is important to form memories
Which memories are better preserved in Korsakoff’s syndrome?
Earlier memories
What does Korsakoff’s syndrome suggest happens over a long timeframe?
Memories are stored in a way not requiring the thalamus
How is sensory information bound together in hippocampal formation?
To form a memory ‘episode’
How does info get slowly transformed to the cortex?
Via the thalamus acting as a ‘bridge’
What is an alternative view of how memories are consolidated?
Over time, memories become more ‘semantic’ and stored according to meaning
What is suggested by giving semantic knowledge tests to patients with hippocampal lesions?
That the cortex can learn semantic info independent of the hippocampus
What was intact in patients with hippocampal lesions?
Earlier knowledge recall
What did patients with large hippocampal lesions exhibit?
Some capacity for new word learning, names and faces- but low performance
2 limitations of case studies of hippocampal damage
- Damage is not usually confined to a single brain structure
- Cases are often rare/unique- makes drawing generalisable conclusions difficult
How is a stroke defined?
A disruption of blood supply and subsequent brain damage
What are the 2 types of stroke?
Ischemic and haemorrhagic
What is the cause of ischemic strokes?
Blood clots
How many strokes are ischemic strokes?
85%
How are ischemic strokes characterised?
Constriction/blockage of blood vessels- brain starved of oxygen
How is a haemorrhagic stroke characterised?
Rupture of blood vessels
Why do symptoms of an ischemic stroke occur suddenly?
Because brain tissue death occurs in minutes
What happens to the cells surrounding an ischemic stroke location?
They are deprived of blood/oxygen
How can doctors usually identify where stroke damage occurred?
Based on symptoms
What can show the extent of stroke damage?
Brain imaging
3 ways the brain responds physically to stroke damage via repair processes
- Creating new blood vessels
- Axonal growth and remyelination
- Creating new synapses and neurons
How may the brain respond functionally to stroke damage by reorganisation?
Surrounding brain region or opposite hemisphere takes on function
What do repair processes and reorganisation show?
Recovery of function is possible
Can people still make full recoveries after severe strokes?
Yes
When does most stroke recovery take place?
Over the first 3 months
Why are people very quickly given intense rehabilitation programs after a stroke?
Recovery takes place very soon after
When is rehabilitation most important?
During the first 3 months
When does motor function most often nearly completely recover?
Within the first few months
What are the most common cognitive impairments after strokes?
In psychomotor speed and executive function
Over the first 6 months following a stroke, how is recovery?
Some recovery of function is possible, particularly in executive function and visual memory
From 6 months onwards following a stroke, how is recovery?
Limited scope for improvement
What determines whether or not strokes cause cognitive problems?
Which brain region(s) have been affected
How many stroke patients experience cognitive impairment or decline?
About 2/3
How many stroke patients go on to develop dementia?
About 1/3
How much greater is dementia development risk among individuals who have experienced stroke?
10 times greater
What can knowledge of stroke damaged regions inform?
Knowledge of which brain regions link to specific functions
What 3 language problems can a stroke cause?
Aphasia, agraphia, alexia
What is aphasia?
Problems producing speech
2 types of aphasia
Broca’s aphasia, Wernicke’s aphasia
What characterises Broca’s aphasia?
Limited speech production
What characterises Wernicke’s aphasia?
Fluent, nonsense speech
What is difficulties accessing semantics in aphasia associated with?
Damage to temporoparietal in left hemisphere
What do aphasia patients show that the temporoparietal regions are important for?
Storing word meanings
What does aphasia show about the left prefrontal regions?
They are important for controlling access to word meanings
How is agraphia characterised?
Spelling and writing problems
How is alexia also known?
Word blindness/visual aphasia
What causes alexia?
Damage to visual/temporal regions in left hemisphere
What problems are involved in alexia?
Reading problems
