consolidation and forgetting Flashcards
define forgetting
“inability to recall something that could be remembered previously”
NOT failure to encode ( must have been formed to forget it)
what is inaccessibility
when a cue is needed to retrieve memory but is not provided
can’t be disproved
Ebbinghaus and rate of forgetting
info rapidly forgotten initially then rate slows
Ebbinghaus 1885 Nonsense syllable experiment
results of which creates the forgetting curve
4 explanations of forgetting
trace decay (mems fade over time) interference (mems get confused, esp if similar) cue dependent forgetting (issue of accessibility & not availability) consolidation (new mems= fragile)
problems with trace decay
average % correct decreased after 18 secs
BUT little forgetting in Peterson and peterson’s 1st trial
Trace decay
Brown - Peterson 1958 trigrams
presented w/ 3 consonant trigrams counts backwards in 3's 0s delay = 90% correct recall 18s delay = 7% recall retention duration = 20s
trace decay
Baddeley et al 1975 ( word length effect)
more time elapses for longer words before rehearsal = longer words forgotten to greater extent
trace decay
phonological loop Baddeley & Hitch ‘74
w/out rehearsal phonological info fades from store
what is interference
ability to remember current info = disrupted by previous/future learning
more sim mems = greater confusion
2 types of interference
Proactive = old info interferes w/ learning new info retroactive = new info interferes w/ retention of old
Retroactive Interference evidence
Waugh & Norman probe digit task
implications for decay account
hear 16 digits and last digit tells u which to report (go back to last occurrence and list no. after)
manipulates how much intervening info before making report
Performance same w/ 1 no. per sec & 4 no.’s per sec.
Decay account should have resulted in poorer performance for the slower 1 per sec condition.
Proactive interference evidence
Wickens et al 1976 (3 words then count backwards 15s before recall)
4 trials w/ diff words
words from new cat = release from PI
(e.g fruit & professions)
profession words more distinct = release from PI
Problems w/ interference
doesn’t explain ebbinghaus curve (slows over time) even as more interference shld = accelerated forgetting
Overlap w/ other accounts (time based decay & cue dependency)
what is cue dependent forgetting
failure to retrieve memory as appropriate cue not presented
non- falsifiable as potential infinite no. of cues
Search engine analogy (CDF)
searching for item online
exists but can only find w/ right search term
Meeter et al (2005)
forgetting curve for newsworthy events
MCQ’s vs free recall
found perfromance better for MCQ’s (52%) than free recall (31%)
MCQ answer options = cue
Tulving and Pearlstone (1966)
recall w/ cues vs free recall
found w/ cues recall double the words
supports as shows mem exists just needs right cue
meaning of the Ebbinghaus curve
shape indicates forgetting slows over time (mems become more stable/ less fragile)
what are the 2 types of consolidation
synaptic = changes in connectivity b/w neurons (occurs rapidly) systemic = mems become independent from hippocampus & move to surrounding cortices (more long term process
Hebb ‘48
what is info storage at synapse
learning & mem repped in brain by physiological changes @ synapse
neural record of experience ( cells fire together wire together)
Info storage @ synapse
Long term potentiation (LTP)
repeated stimulation = enhanced neuron firing
structural changes & enhanced responding ( neurons in hippocampus, amygdala & cortex show LTP after learning ep.
what happens in mind-mem consolidation
mem for recent events = fragile
if disrupted recent mems won’t consolidate
new info & protein inhibitors can interfere w/ mem consolidation
sleep can aid process
behaviour approach
Muller & Pilzecker 1900
effect of delay on mem consolidation
p's learn 2 lists of words IV - group 1 learn 2nd list immediately, group 2 learn after 6 min delay DV - mem recall for 1st list, immediate = 28% delay = 48%
behaviour approach
Gais et al 2007
effect of sleep on mem consolidation (fMRI study)
IV - group 1 = learn list shortly before sleep group 2 = learn hours before sleep DV - % words forgotten 2 days later sleep = 0.5% awake = 16% different brain activity b/w groups
what interferes w/ synaptic consolidation
sleep (but not if REM)
Post trial alcohol (reduces RI rather than facilitating consolidation)
suggests new mems interfere w/ synaptic consolidation process
Anterograde amnesics & consolidation
some capable of long-term retention when interference minimised
Cowan et al 2004 recall after different intervals
Anterograde & consolidation
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
4/6 patients had better mem following the unfilled 10 min interval
Dewar et al 2009 early and later interference
Anterograde & consolidation
if p’s rehearsing in STM shld be no diff b/w early & late interference ( 1st & last 3 mins)
Performance best when no interference but also better when interference in the last 3 minutes
inconsistent w/ absence of LTM
Dewar et al 2009 retroactive interference effects
implications
patients more susceptible to RI effects
Explains why mem better when interference occurred later: provided opp to consolidate learning
More forgetting when interference is immediately after learning = synaptic consolidation is disrupted
New cog model of forgetting
explains anterograde amnesia by depletion in consolidation resources
Anterograde Traumatic Brain Injury Consolidation Failure
Yarnell and Lynch, 1970 (american football players)
Remembered the incident when leaving the field but could not recall it later = Failure to consolidate
Yarnell and Lynch, 1970 implications of anterograde amnesia
In anterograde amnesia, mems can be preserved if interference reduced ( allowing more efficient synaptic consolidation)
Retrograde Amnesia
Patient PZ
Patient PZ had just completed his memoirs prior to amnesia= good source for checking mem loss (Zola-Morgan et al., 1983)
Older memories more resilient than recent memories
Found for both semantic and episodic mems (Mann et al., 2003; Bayley et al., 2006)
Retrograde Amnesia: 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
