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Lecture 5

PSC 130 Lecture Notes - Lecture 5: Retrograde Amnesia, Memory Consolidation

Course Code
PSC 130

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January 24, 2017:
I. Chapter 9: Forgetting
A. Why Do We Forget?
1. Consolidation Theory memory is solidified gradually after the encoding event
Jenkins & Dallenback (1924) Effects of sleep on recall
a. *Sleep slowed forgetting
i. Much more forgetting if subjects were made to stay awake
ii. Reason why sleep: to consolidate the important parts of the day for your memory ;
remind yourself to slowly forget information
b. Consolidation process
i. If we forget, it’s because we did not have time to consolidate memories/information
Squire (1984) temporally graded retrograde amnesia memory loss for events just prior to the
a. *Info encoded more than 3 years prior to the lesion was not forgotten
b. Systems consolidation the hippocampus is initially involved in memory storage, but
memories are transferred to the cortex over time
Quire, Clark, & Knowlton (2001)
a. *Graded retrograde amnesia is seen in many species
2. A challenge to systems consolidation theory:
a. The temporal gradient can be as strong as 40 years in humans
i. Ex: Parker et al. (1900) famous faces test
b. “It is difficult to conceive of an adaptive basis for a consolidation process that is almost as
long as the average human life span throughout much of history. According to this notion,
most people would not have consolidated any autobiographical memories before they died.”
(Nadel & Moscovitch, 1997)
c. What would you expect from an fMRI test?
i. You should see recent memories involves hippocampus
ii. Older memories involve cortex, not hippocampus
d. Stark & Squire (2000) fMRI for older and newer memories
i. Study: line drawings (1/2 hours, 1 day, 1 week prior to scan)
ii. Test: recognition memory (in scanner)
iii. *Hippocampal activation did not decrease with age of memory
iv. No evidence for consolidation
3. Trace Decay Theory memory traces are eroded by the passage of time
a. Things are encoded, neural connections are made; over time things get erased (or decayed,
slowly disintegrates) and you will forget
b. Everything decays, general principle of entropy
c. The passage of time is sufficient for things to be forgotten
4. Interference Theory older memories are more difficult to retrieve because there is more
from other memories
a. Once good representation for a memory is made, it remains in memory
b. It gets harder to retrieve it because over time, other memories make more interference for
retrieving it
c. You never forget it, but have trouble retrieving it
5. How can we distinguish between decay and interference?
a. General paradigm:
i. Study Recall
ii. Study Unfilled Delay Recall {Decay}
iii. Study Filled Delay Recall {Decay + Interference}
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