Lecture 5 - Autobiographical Memory, Forms of Amnesia and Systems Consolidation

episodic memory

episodic memory

memory for accurate and detail representation of personal events, associated with a time and place, autobiography that is not particularly event specific

semantic memory

represents accumulated experiences, overarching representation of listening to lectures for example, enhances coherence of self knowledge and identity over time, how we structure autobiographical memory

what is the autobiographical memory interview (AMI)?

quantifies person's episodic and semantic autobiographical memories and uses personal narratives to assess bias towards episodic or semantic autobiographical information, probes memory across the lifespan, tries to match stimuli between participants

what are the common cues/probes used for AMI?

childhood bday party, early adulthood would be first day at job, recent events like holidays, etc

internal details (AMI)

similar to episodic, pertained directly to main event described by the participant, event, time, place, perceptual detail (percep), thought/emotion (T/Em)

external details (AMI)

semantic factual information or details pertaining to events other than main event, something that reminds them of another event, things that are not exactly specific to that event

perceptual details

things you actually see

thought/emotion

how you or others are feeling 

age related differences study

when comparing young vs old people the younger group was found to have more internal details so more specificity in memory and are biased towards episodic details reflecting happening, locations, perceptions and thoughts, the old group was found to have more external details, more semantic, biased towards details not connected to a particular time and place and also reported less episodic re-experiencing so less time travelling

• age related bias for semantic details in autobiographical details

infantile amnesia

not remembering memories from 2 to 3.5 years old, occurs in animals as well as humans, at ages 3 and 4 we start talking so maybe that prevents us from forgetting, reason might be because at 3 to 4 we start developing a sense of self

childhood amnesia

memories in this period exist but are fewer than expected given delay alone

reminiscence bump

more memories than expected between ages 15-35 yrs so in adolescence and early adulthood, better encoding and retention in LTM due to peak neural processing and lots of novelty, recall in this phase is organized around cultural life scripts

life scripts

shared expectations concerning the order and timing of life events in a prototypical life course, children generate it then show reminiscence bump when narrating their personal futures

what is the structure of life scripts?

most things mentioned happen in the reminiscence bump, accounts for some of the reminiscence bump

non life script memories

might be that it happens close to life script events like honeymoon after your wedding

cognitive view of reminiscence bump

many of these events of this time are novel

neurological view of reminiscence bump

neural processes are at their peak neither maturing nor declining

identity formation view of reminiscence bump

a person's identity is formed; decisions made about social identity, vocation, etc. These decisions that shape one’s future and thus many actions are associated with them

what are the two main issues at stake regarding the MTL?

assumption is that the MTL is unitary performing the declarative memory function, episodic and semantic memory are therefore both supported by that system in the same way but is that really true?

hippocampal amnesia patients

have lesions in these areas only

MTL amnesia patients

have hippocampal lesions and lesions in surrounding MTL cortex so the perirhinal, parahippocampal and entorhinal cortex

what is the traditional view of how the MTL works?

its a unitary declarative memory system so all structures contribute to declarative memory, this means that any part of it should therefore produce a deficit in declarative memory

what is the traditional view of the role of the hippocampus?

that in episodic memory it is time limited and memories are consolidated to the neocortex overtime, old episodic memories consolidate to the neocortex too and should be of equal quality meaning that it is independent of perception, working memory and implicit memory

MTL unitary system experiment

took 3 people who sustained selective hippocampal lesions early in life, then they were tested as adults and scored on immediate recall of short paragraph or tested on recall ½ an hour later

MTL unitary system experiment results

in the control individuals 80% of details were recalled immediately and after a ½ delay but in the 3 individuals with hippocampal lesions 40-60% of information was recalled immediately and hardly anything was recalled after a ½ delay

• episodic memory was impaired but semantic was preserved so the hippocampus was thought to be the core of declarative memory but not necessary for all forms of declarative memory

MTL unitary memory system experiment (replication study patient SS)

failed to acquire any new semantic knowledge as her damage was extended to the medial temporal lobe which included the hippocampus and cortex

MTL unitary memory system experiment (replication study patient PS)

had selective hippocampal damage, so could recognize new vocabulary and famous people that came into the public domain after her lesion

what are the two views of the MTL function?

option 1 is that it is a unitary memory system but option 2 is that it has separate subsystems in the MTL that deal with semantic being perirhinal and entorhinal while episodic memory deals with the hippocampus

butcher on the bus phenomenon

may fail to recollect details about a person but nevertheless have a sense of familiarity

recollection vs familiarity (modern view)

hippocampus is necessary for conscious recollection where MTL cortex and especially perirhinal is necessary for familiarity based recognition memory so ideally the modern view of MTL suggests that there would be no problem with familiarity if damage is restricted to the hippocampus

recollection vs familiarity experiment

show a bunch of words and add in a recognition task (establishes familiarity), if they say old to the item you ask if they remember that or know that? (recollection vs familiarity component), look at the number of details they are able to recall

recollection vs familiarity experiment results

patient 1(intact HC but removed PHC) does ok with recollection but does badly with familiarity, consistent with the butcher on the bus phenomenon while patient 2 (removed HC) is the opposite does badly with recollection but good with familiarity

• HC is involved in recollection and PHC is involved in familiarity so consistent with the modern view of MTL organization

traditional view experiment

participants are shown a face that is laid over on top of scenes and people have to judge which of the faces appeared after the scene

anoxic patients

patients that are affected by severe lack of oxygen in tissues or organs or in a place or environment

perirhinal cortex

hierarchal system for perception

perirhinal cortex experiment

had 3 features that characterized a group of objects and had to say if they are the same, differ on one feature or across all 3 features

anterograde amnesia

inability to learn new info after injury

retrograde amnesia

loss of memory prior to the incident

ribot’s law of retrograde amnesia

more recent memories are lost and old memories retained, follows a graded loss of memories over 20 yrs, the dissolution of memory is inversely related to the recency of the event

quality of the memory rather than the time experiment

‘imagine you are lying on a white sandy beach’ (sentence acts as the cue), then define or explain what happens, there is the vividness score so you could be coming up with things but they aren’t really vivid memories which goes against the quality theory because if it was the quality of time there would be a deficit even when time isn’t involved, patients with hippocampal damage can acquire new semantic information so it could be that there’s a time component but there is a difference in terms of quality

autobiographical memories in amnesia experiment

participants are prompted with one question and one sort of theme or unique event (ex: getting married), when retelling there seems to be a story but there isnt really a coherent structure, they are asked very specific probes to get to the details, could be when or where type questions to get those episodic like memories but semantic and episodic memories are involved in the same type of memory so you can see that factual memory is intact

role of hippocampus according to autobiographical memories study in amnesia

its necessary for recollection of rich perceptual aspects and temporally specific details of past experiences, story elements and gist of information are more resilient to hippocampal damage cause they are semanticised in memories