Episodic Memory 1 + 2 Flashcards
The medial temporal lobe declarative memory system
- describe the changes encountered by HM after the resection of the medial temporal lobe.
- was has this told us about the MTL related to memory?
- Profound anterograde amnesia - inability to learn new information. Including personal experiences (eg meeting new researchers). Could not lay down new autobiographical memories
- Limited retrograde amnesia - 1-2 years prior to the surgery he could not remember BUT his more distant past was spared
HENCE the MTL is crucial for acquiring new long-term memories and plays a time-limited role in their storage and retrieval. After several years the memories must become independent of hippocampus, which is why the more distant past was spared.
The medial temporal lobe declarative memory system
Not all types of memory depend on the MTL. This is evident from HM, as _______ memory (facts, general knowledge) was spared and he could even acquire new _______ knowledge.
Also, his ______ memory was spared (skill learning) and he was able to learn and improve on tasks such as _______ ______ and motor sequence learning.
HM’s _____ _____ _____ was also spared (he could remember a digit sequence)
Finally, ______ which is a form of implicit memory was also spared.
semantic
semantic
procedural
mirror drawing
short term memory
priming
Long term memory is thought of as being divided into _______ and ________ (implicit) memory.
The former is located primarily in the _______ ______ ______, ______ nuclei and mammillary bodies (middle diencephalon. It can be further divided into ______ memory, which are memories that have a context; time and place, and _______ memory, or facts about the world, yourself, objects, language, etc.
The latter includes things like _____ memory (eg: riding a bike), priming, and _______ conditioning.
declarative
non-declarative
medial temporal lobe
thalamic
episodic
semantic
procedural
classical
Which memory types do autonoetic and noetic consciousness map onto?
autonoetic - episodic memory - putting yourself back into that experience
noetic - semantic memory - facts - just knowing
The medial temporal lobe declarative memory system
The hippocampal complex is made up of the _______ proper and then ________ complex. Signals enter and leave the complex via the ________ cortex which _______ the hippocampus. The EC also has projections to the _______ cortex (PR) and ____________ cortex (PH), both of which have been shown to be important for different aspects of memory, _______ of the hippocampus
hippocampus subicular entorhinal envelops perirhinal parahippocampal independent
The medial temporal lobe declarative memory system
The perirhinal cortex (PRC)
- location? projections?
- function?
- evidence?
- anterior part of parahippocampal gyrus
- projects to anterior parts of hippocampus
- familiarity-based item recognition NOT CONTEXT dependent
- learning associations between objects (eg: banana is yellow)
- disriminating between objects with lots of featural overlap
- lesions lead to impairments in recognising objects, words, faces
- activations here during learning objects correlate with familiarity/recognition later on
- fMRI studies
1. confidence in recognition correlated positively with BOLD response
2. no differences in recognition between item only and item+source. Hence, it generalises over context.
The medial temporal lobe declarative memory system
The parahippocampal cortex (PHC)
- location? projections?
- function?
- evidence?
- posterior part of parahippocampal gyrus
- projects to posterior parts of hippocampus
- recollection of context information
- autobiographical memory - personally meaningful experiences
- spatial memory and navigation
- scene perception (PPA)
- activation in PHC during learning and retrieval are high when context is successfully remembered (eg learning a list of words from a green list or red list)
- recollection is also more accurate when the context is successfully remembered, compared to when not remembered
Projections from the PRC and PHC are very _______. However, it is theoried that the PHC has a similar role to the _______ in contextualising memories. They have similar ______ patterns.
segregated
hippocampus
activation
Long-term memory consolidation
- standard consolidation theory states…
- information is initially represented in all areas of the cortex (vision, spatial, etc)
- then it is consolidated into a memory trace by the MTL (this short period of consolidation is sec-mins)
- this is followed by a prolonged period of long-term system consolidation (takes years)
Hence, the MTL is initially important for the retrieval of these memories, but then it is fully consolidated in the neocortex and becomes independent of the MTL (and immune to it’s damage like HM)
Long-term memory consolidation
Standard consolidation theory sees memory as a _______ construct (generalises types of memory, including semantic and episodic memory BUT not ______ knowledge and _______)
There is a _______ gradient in ______ memory, that is, events and facts acquired more recently are more _______ affected and more distant memories better _____.
unitary
conceptual
language
temporal
retrograde
severely
preserved
Long-term memory consolidation
Describe the challenges to standard consolidation theory
- some patients don’t show clear temporal gradient. Even HM, when retested, does have some issues with distant memories
- some people don’t remember distant memories of childhood
- old memories, even when retained, have been shown to be lacking in rich detail. And especially lacking in the detail needed to “re-experience” the event (so has become a bit more like a semantic memory)
- temporal gradient evident with semantic memories only (more distant ones are remembered) BUT autobiographic memory (context-driven) often completely impaired
Long-term memory consolidation
- multiple trace theory has used the case of KC to postulate…
KC
Severely impaired episodic memory for personally
experienced events (autobiographical memory)
– Covers whole life
• Temporal gradient for semantic memories pertaining to general semantic facts, public events, famous people (lost info from the last 5 years)
- event is encoded across the cortex
- the hippocampal complex binds this into a memory trace - it keeps an index of where things are stored AND provides context
- retrieval (or reactivation) occurs in different neuronal and experiential context (the brain is different, and the context is different. You recall the memory in that different time) SO a new memory trace is laid down by hippocampus.
The new memory trace is different, as new information is added to it. BUT all memory traces are similar in semantic information…they only differ in spatial context.
Long-term memory consolidation
Multiple traces facilitates the extraction of ______ information common to all, which becomes ________ of context.
Multiple trace theory also means that, older memories are more resistant to _____ as there are several routes of _______.
factual
independent
damage
retrieval
Long-term memory consolidation
What does multiple trace theory tell us about episodic and semantic memory?
It highlights that there is a temporal gradient for semantic information
AND
There is no temporal gradient for autobiographic/context-driven (episodic) memories as these continue to rely on the hippocampus throughout
Long-term memory consolidation
Describe the imaging evidence from multiple trace theory
- no difference in patterns of hippocampal activation for recent and remote memories (age of the memory doesn’t make a difference)
- hippocampal activation correlated with the vividness of re-experiencing the memory for BOTH recent and remote memories
