amnesia Flashcards
what amnesia is
- Intelligence is intact
- Attentional span is intact
- Personality is unaffected
- Ability to take in new information is severely and using permanently affected.
- HM (Scoville and Milner, 1957)
- They would have daily seizures.
- Underwent surgery for the treatment of severe epilepsy - cured his epilepsy.
- Completely lost his memory for events after surgery.
- Could not recall ever having met the specialists he had been talking to after they left he room for a few minutes.
anatomy of amnesia
- HM’s surgery removed parts of his medial temporal lobes.
- Included the “hippocampus”.
- Amnesia is usually caused by damage to the medial temporal lobe or connected regions.
- Can occur in head injuries, Alzheimer’s disease, epilepsy, stroke.
new learning - anterograde amnesia
- Anterograde - after brain injury.
- HM had anterograde amnesia:
- HM was severely impaired no matter what kind of memory test was given (Corkin, 2002)
- Words, faces, tones, public events, etc
- Regardless of test format (free recall, cued recall, recognition)
· 3 amnesic patients - performance on the “Rey complex figure” test of visual memory - recall test.
- Copy it as accurate as possible, and then after 5 minutes are to re-draw it again, trying to remember all the little details.
· Recognition memory test for faces
· Teste of learning may use a recall or a recognition format.
· Typically use both verbal and visual tests.
· Relatively large number of items (many more than can be stored in working memory).
· Test after a delay (typically of a few minutes). - Patients with anterograde amnesia impaired on all tests.
which memory systems are not affected?
· Verbal and visual short-term memory
· Digit span - repeat the numbers “2…7….4….9….2….8”
· Spatial span - tap the same blocks as me, in the same order.
· Procedural memory
· Amnesics can learn new skills - mirror tracing (Corkin, 1968), also weaving, controlling a joystick, mirror reading, etc.
- Priming - degraded picture identification, 5 amnesic patients - Elizabeth Warrington
declarative memory theory
· Tulving (1972) proposed that episodic and semantic memory is different - amnesia only for episodic memory?
- Squire (1982) argued amnesia as a loss in the ability to form any new “declarative memories”
can amnesics acquire new semantic memories - no
· Bayley et al, (2008) tested new vocabulary in 2 adult amnesics.
- Each test item contained one target word (e.g., Prozac) and eight foil words (e.g., Flozac, Prozam, Grodaz, etc).
can amnesics acquire new semantic memories - yes
· Beth, Jon and Kate are typical amnesics (Vargha-Khadem et al, 1997).
· They sustained damage to the hippocampus just after birth.
· Have grossly impaired episodic memory.
- But, they completed normal schooling, have good vocabularies and knowledge about the world.
can amnesics acquire new semantic memory
· Implications for declarative memory theory.
· Squire characterised amnesia as a loss in the ability to form any new “declarative memories”
· Evidence that Beth, Jon and Kate could acquire semantic memories is evidence against that.
- But - perhaps memory processes in their brains are unusual as their brain damage occurred so early in life?
old memories (retrograde amnesia)
· Retrograde means before brain injury.
· Some retrograde memory loss is almost always present in amnesia.
· HM’s retrograde memory for famous people was generally good.
· Warrington (1996) argued that tests often used highly familiar photos of people.
· Match for how famous they were at the time.
- Amnesics are impaired at all retention intervals.
multiple trace theory
Every time a memory is retrieved, it is re-encoded and a new set of connections (trace) between the hippocampus and the cortex is made.
standard theory of consolidation versus multiple trace theory
· No consensus about who is right.
· Evidence to support both theories - from fucntional MRI as well as patient studies.
· Perhaps memories are transformed over time:
- If a memory becomes part of your general knowledge it isn’t affected by amnesia caused by medial temporal lobe damage.
- But to vividly recall a memory, you might always need you medial temporal lobes.
semantic memory
· Conceptual knowledge about the world.
· Includes:
- Knowledge of the meaning of words, objects and other stimuli perceived through the senses.
- Facts and associated information.
semnatic damage
· Difficulty in remembering the meaning of words or concepts.
· Naming errors (e.g., “dog” for rabbit).
· Problems not confined to a single modality - may include a difficulty in recognising sounds (e.g., doorbell or telephone).
· “A horse?… But what are those lines doing?” - response from a patient with semantic dementia.
· Scan of a patient with semantic dementia.
- Semantic knowledge associated with lateral temporal cortex (on the left side).
memory and executive functions
The frontal lobes are important for the strategic aspects of memory:
- Searching for the right memory.
- Checking and verifying the memory is correct
- Does it fit with the current situation?
confabulation
· Patient 1: “…he believed that he was a spaceship commander… During that period he occasionally became a “space pirate”.” Damasio et al., 1985
· GT: believed that she was in a school rather than a hospital;
thought the nurses station was the staff room. Bird et al., 2004
· “erroneous memories, either false in themselves or resulting from ‘true’ memories misplaced in context an inappropriately retrieved or interpreted” Kopelman, 1995.
· Provoked - e.g. saying that items in a test have been shown before when they were not
- Spontaneous – e.g. tries to leave a hospital because believe they have to go to work or cook a meal
