Amnesia, Unlearning & Forgetting Flashcards
HM: result of surgery to alleviate severe temporal lobe epilepsy
Boswell: due to Herpes simplex encephalitis
Both: damage fairly extensive, but hippocampi most damaged in both.
Almost all hippocampi on both sides + neighbouring cortical regions (entorhinal, perirhinal and parrahippocampal cortex)
What’s the Hippocampus?
Infolding of the cerebral cortex along inner edge of temporal lobe
Relevance of hippocampus to anterograde amnesia
Key region; with damage long term declarative memory formation is very impaired
Unlike in the neighbouring regions
But hippocampus isn’t important in storing memories
Old memories still affected but less than new
Korsakoff’s syndrome:
Causes
Thiamine Deficiency, usually as a result of long-term alcohol abuse
Korsakoff Syndrome:
Effects
Both RA & AA Amnesia
(declarative memory affected)
Neuropathology is widespread, but relatively little effect on hippocampus
Regions damaged that are responsible for memory dysfunction: Mamillary bodies, parts of thalamus they connect to, & regions of frontal cortex
AMNESIA: eye-blink conditioning procedure
Describe: Procedure
Delay procedure with delay interval of 1.25 seconds where:
Tone beeps, 1.25 seconds later (while tone still beeps), puff air into subjects eyes
Done whilst participants watching film with headphones (same as earlier)
AMNESIA: eye-blink Delay conditioning procedure
Describe: Participants
Group of normal people
Group of AA with hippocampal damage
AMNESIA: eye-blink Delay conditioning procedure
Describe: Results
Both types of participants acquired CRs
None of amnesics formed declarative memory of having undergone procedure, all normals did (though some normals failed to make declarative memory of CS-US relationship)
What type of learning are Eye-blink conditioning procedures used to study?
Eye-blink conditioning is used for studying associative learning
AMNESIA Trace conditioning procedure
Describe: Procedure
Trace procedure where tone in headphones stops before air puff (while participants watch a film)
AMNESIA Trace conditioning procedure
Describe: Results
Amnesics failed to acquire CRs
Similar results achieved with rats
AMNESIA Delay & Trace conditioning procedure (rats)
Describe: Results What it tells us
Removal of hippocampi prior to conditioning: CR acquired if delay procedure is used but not trace procedure
Removal of hippocampi after conditioning (rats): CRs acquired with trace procedure
Conclusion: Results consistent:
role of hippocamppus is to retain information about CS over trace interval (short period of time)
So, CRs acquired before hippocampal removal should not be affected (no retrograde effects)
As, hippocampus damage does not produce RA in people so does not abolish previous CRs acquired in trace conditioning
Define: Delayed Conditioning procedure?
Delayed Conditioning: Tone sounds and then immediately puff air into participants eyes.
The tone and the puff are very close in time.
Define: Trace Conditioning procedure?
The sound tones but then you wait for a bit (let’s call this the “trace interval”) before puffing the air. There’s a gap between the bell and the puff.
Describe: what happens with removal of the hippocampus before conditioning? (Delayed vs Trace conditioning)
Participants can still learn to blink their eyes with delayed conditioning (since the tone and puff happen almost at the same time).
But, they won’t learn it with trace conditioning because they can’t remember the bell during the gap (trace interval).
This suggests that the hippocampus helps remember the bell during that gap
Describe: What happens if the hippocampus is removed after the conditioning?
If you train the pet with trace conditioning first and then remove the hippocampus, the participants still remembers to blink its eyes when it hears the tone. This means that once the memory is made, the hippocampus is not needed to keep it.
Describe: importance for hippocampus in memory?
The hippocampus is important for learning new things when there’s a gap in the information (like the gap between the tone and the air puff).
But once something is learned, even if the hippocampus is removed, the CR is not affected
AMNESIA Delay & Trace conditioning procedure (humans)
Describe: Results What it tells us
In experiments with humans, people watch a movie and might not notice that a tone is predicting a puff of air to their eye.
If they don’t notice (don’t acquire declarative knowledge), they won’t learn to blink with trace conditioning. They might be too distracted by the movie to remember the bell during the gap.
Without the hippocampus retaining the bell information over the gap, they don’t learn the relationship between the tone and the puff (no blinking with trace conditioning). However, they would learn with delayed conditioning because there’s no gap to remember.
People can learn without noticing the connection if the hippocampus keeps the information during the gap, but if they’re distracted, they might not learn with trace conditioning
