Lecture 7- Consolidation and forgetting Flashcards
what is forgetting
we get lots of material
not a failure to encode this material as it as never internalised
one must have formed a memory in order to forget it
forgetting is the inability to recall somethingnow that could have been recalled earlier on occasion
define forgetting in reference to inaccessibility
sometimes we need a cue in order to recall that memory - in absence of that cue we have an issue with inaccessibility
we cant disprove the inaccessibility account of forgetting
- therefore when discussing forgetting we don’t dissociate unavailable / lost memories and inaccessible ones
what is the curve called hich is also known as the curve of forgettig
ebbinghaus curve of forgetting
- nonsense syllable experiment
what was the method in ebbinghaus study
Over the course of days, he kept relearning lists of nonsense syllables (e.g., RUR, HAL, BEIS, etc.)
Forgetting was measured as percent savings (a comparison of immediate testing versus testing after a delay)
Information is rapidly forgotten at first (non-linear)
what are the 4 explanations of forgetting and explain
Trace decay
Memories just fade over time
Interference
Memories (particularly if similar) get confused
Cue-dependent forgetting
Issue of accessibility and not availability
Consolidation
New memories are fragile
they are not mutually exclusive
what is trace decay
memories fade over time
what is a practical example of trace decay
Model of working memory: the phonological loop (Baddeley & Hitch, 1974)
Without rehearsal the phonological information fades from the store
( decay of phonological loop- but if keep rehearsing will store )
Word Length Effect (Baddeley et al., 1975)
More time elapses for longer words before rehearsal
Therefore longer words should be forgot to a greater extent …
what is the Word Length Effect (Baddeley et al., 1975) for trace decay
Word Length Effect (Baddeley et al., 1975)
More time elapses for longer words before rehearsal
Therefore longer words should be forgot to a greater extent …
eg if phon loop = 9 seconds, takes longer to fit in longer words than shorter words to be able to remember
what are the common problems with trace decay
Brown-Peterson (1958)
Subjects presented with 3-consonant trigrams (BDK)
Required to count backwards by threes
0-sec delay: 90% correct recall
18-sec delay: 7% recall
Retention duration ~20 sec
- shows average of the trials = more forgetting and the forgetting rate of the first trial indicates less forgetting - all additional trials show INTERFERENCE with forgetting
- sleeping
info lost at same rate when sleeping or not sleeping
but sleeping has less decay - so isnt only area of importance
what is interference
our ability to remeber current information is disrupted by previous and future learning
- effects not simply due to passage of time
- more similar memories = more confusion
what are the two types of interference
Proactive
Old information interferes with learning new information
Waiter: first order of a shift interferes with memory of last order
Retroactive
New information interferes with retention of old information
Waiter: last order of a shift interferes with memory of first order
what is the evidence for Retrieval interferance
- Waugh and Norman probe digit task View 16 digits and last digit tells you which to report 1596234789024815 -> 9 1596234789024817 -> 8 1596234789024812 -> 4
Performance was the same with one number per second and 4 numbers per second.
Decay account should have resulted in poorer performance for the slower 1 per second condition.
Wickens 1976
- pps listen to 3 words counted backwards for 15 seconds then recalled words
- 4 trials- diff words on each trial
- words Words from a new category caused a release from PI
what are the problems with interferance
Does not explain why rate of forgetting (Ebbinghaus) slows over time
As even more interference should result in accelerated forgetting
Overlap with other accounts
Time-based decay
Cue-dependency
what can cue dependant forgetting be likened to
The Search-Engine Analogy
Searching for a specific item online
The web-page exists somewhere but in order to find it you need the right search-term (or cue)
what is cue dependant forgetting
Cue dependent forgetting = failure to retrieve as the appropriate cue has not been presented
Memory exists but issues in accessing that memory
explain meeter 2005 assessment on cue dependant forgetting
Meeter et al. (2005) examined the forgetting curve for newsworthy events
Performance was better for multiple choice questions (52%) compared to free recall (31%)
The MCQ answer options operated as a cue
Forgetting why you entered a room
Must go back to where you were in order to remember (back to where the cues are)
explain tulving and perstones 1996 assessment on cue dependant forgetting
Tulving and Pearlstone (1966) found that participants recalled twice as many words when given a cue compared to free recall
Memory exists but requires the appropriate cue
But performance not at 100% so other explanations needed?
Or perhaps the appropriate cue has not yet been presented
what are the weaknesses of cue dependent forgetting
- not falsifiable
performance isnt 100% with cues
why is the context important in cue dependent forgetting
Memory is better when the context at learning and retrieval is the same
Context operates as a cue to recall
what does the shape of the ebbinghaus curve assume
The shape of the Ebbinghaus curve indicates that forgetting slows down over time.
Put another way, memories become more stable / less fragile over time.
what are the two types of consolidation
Synaptic: changes in the connectivity between neurons (occurs quite rapidly)
Systemic: memories become independent from the hippocampus and move to the surrounding cortices (more long-term process)
what did hebb suggest about information being stored at teh synapses
Hebb (1948)
Learning and memory represented in the brain by physiological changes at the synapse
Neural record of experience
Cells that fire together wire together
as neurons fire= strengthening or inhibitions of wiring
how does long term potentiation suggest aboyt info being stored at the synapses
Long-term potentiation (LTP)
Enhanced firing of neurons after repeated stimulation
Structural changes and enhanced responding
Neurons in the hippocampus, amygdala, and cortex show a long-term enhanced response (“potentiation”) after a learning episode
what are the structural changes which occur when memories are consolodated
- single presenattion of stimulus= less activation
- structural changes due to repeated exposure to material - which enhances te firing rate
what can happen if memorys are disrupted
Memory for recent events is fragile
If disrupted, recent memories can fail to be consolidated
New information can interfere with memory consolidation
Protein synthesis inhibitors can disrupt memory consolidation
Sleep can aid the consolidation process
name something which can disrupt memory consolidation
protein synthesis
name something which can enhance memory consolidation
sleep can aid consolidation
- less forgetting when sleep= more ability to consolidate due to less interfering items
describe Mullers evidence for the behavioural approach to consolidation - IV
One group learned the second list immediately after the first list
The other group experienced a six-minute delay between learning the lists
describe Mullers evidence for the behavioural approach to consolidation - dv
Memory (recall) for the first list of words
describe Mullers evidence for the behavioural approach to consolidation - procedure and results
Muller and Pilzecker (1900) had participants learn two lists of words
recall when recalled immediately = 28%
48% if after 6 mins
shows performance increased as had time to consolidate
but rehearsal may have occured- therefore no decay
how does sleep affect consolidation
sleep can aid consolidation
- less forgetting when sleep= more ability to consolidate due to less interfering items
describe phsiological evidence for memory consoloidation
Gais et al. (2007) the effect of sleep on memory consolidation
Measured brain activity using fMRI
Results
Found differential brain activity between the two groups during retrieval
in what type of amnesia has Synaptic Consolidation been seen
antereograde
what is synaptic consoloidation
Periods of acute anterograde amnesia assist memories formed just prior to amnesia
Sleep (Jenkins & Dallenbach, 1924: but not if REM, e.g. Phihal & Born, 1997; 1999)
Post-trial alcohol (e.g. Lamberty et al., 1990)
Due to RI reduction rather than facilitating consolidation (Tyson & Schirmuly, 1994)
Suggests that new memories interfere with the (synaptic) consolidation process
But isn’t this just the effect of retroactive interference?!
This has been examined in the context of anterograde amnesia …
what are the 2 types of amnesia
antereograde and reterograde
explain antereograde amnesia
Inability to acquire new memories following incident
But some learning persists…
antero= future
explain reterograde amnesia
Inability to remember memories prior to the incident
Often temporally graded
retro= past
who is often used in sudies about antereograded amnesia
Classic example (patient HM: Milner, 1966)
Surgery to alleviate serve epilepsy
Lesion of the medial temporal lobe
Severe anterograde amnesia
But some learning: improvement on the mirror tracing task despite no episodic recall of task, or memory for the experimenters (Corkin, 1968)
what evidence is there for learning in HM
Evidence of learning even if not declerative memories
But some learning: improvement on the mirror tracing task despite no episodic recall of task, or memory for the experimenters (Corkin, 1968)
what type of memory cant be encoded in anterograde amnesia
cant encode memories from stm to ltm
can retrieve them
Inconsistent with the view that in anterograde amnesia patients, STM is intact but LTM is impaired
Evidence for LTM remaining
explain cowans study about ho some amnesic patients capable of long-term retention when interference is minimised
Cowan et al. (2004)
6 densely amnesic given a list of 15 words to remember
Recall test was (i) immediately, (ii) following an unfilled interval, or (iii) following a filled interval
4 out of 6 patients had better memory following the unfilled 10 minute interval
Benefited from a ‘minimisation of (retroactive) interference’?
Do these patients have a greater susceptibility to interference?
Or do they just rehearse in the STM for 10 minutes?
The rehearsal interpretation was examined by Dewar et al. (2009)
If participants rehearsing in STM there should be no difference between early and late interference (as both would abolish rehearsal) ….
Performance best when no interference but also better when interference in the last 3 minutes
Inconsistent with an absence of LTM!
Dewar et al. (2009) argue that forgetting in amnesic patients is …
is due to retroactive-interference-induced impairment of synaptic consolidation
That is, these patients are more susceptible to the effects of retroactive interference
Explains why memory better when interference occurred later: this provided an opportunity to consolidate learning
More forgetting when interference is immediately after learning as synaptic consolidation is disrupted
how does the new cognitive model of forgetting explain antereograded amnesia
Anterograde amnesia explained by a depletion in consolidation resources
depletion of consolidation resources in anterograde amnesia
whats another injury which can be explained by the new cog model of forgetting
This model can also explain temporary anterograde amnesia following Traumatic Brain Injury
Examination of American Football players post-blow-to-the-head (‘dinged’) (Yarnell and Lynch, 1970)
Remembered the incident when leaving the field but could not recall it later
Failure to consolidate
what is systemic consolidation
In systemic consolidation, memories are purportedly moved out of the hippocampus into the surrounding cortices
A longer term process
Months to years
Can systemic consolidation explain other amnesia effects?
how are memories preserved in anterograde amnesia
In anterograde amnesia, memories can be preserved if interference is reduced (thereby allowing more efficient synaptic consolidation)
what is a key methodological issue with assessing retrograde amnesia and how can this be resolved
Key Methodological Issue: How do you know what individuals knew prior to injury?
Solution: Use well-known events or ask family members
how is retrograde amnesia characterised
Retrograde amnesia is often characterised by graded decline in recent memories (Kopelman, 1989)
Patient PZ had just completed his memoirs prior to amnesia: therefore good source for checking memory loss (Zola-Morgan et al., 1983)
Older memories more resilient than recent memories
Found for both semantic and episodic memories (Mann et al., 2003; Bayley et al., 2006)
how is retrograde amnesia explained by systemic consolidation
Temporally graded amnesia (greater loss for more recent memories) is consistent with systemic consolidation
Assumes that hippocampus and associated areas operate as an intermediate storage structure
Older memories get moved into the neocortex (outer layer of brain)
Therefore, damage to the hippocampus (and/or associated areas or connections) affects new memories
Older memories survive as not hippocampal-dependent
