PS4529/30 Applications of Cognitive Neuroscience
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Transcript of PS4529/30 Applications of Cognitive Neuroscience
PS4529/30PS4529/30ApplicationsApplicationsof Cognitiveof CognitiveNeuroscienceNeuroscience
Consensus View of Long-Term Memory
ENCODING RETRIEVAL
Seeing Word
Hearing Word
MTL
MTL
MTL
MTL
A Specific Example
• The constructive memory framework (CMF)• Schacter, DL, Norman, KA, and Koutstaal, W.
(1998). The cognitive neuroscience of constructive memory. Annual Review of Psychology, 49, 289-318.
• Invokes multiple brain regions• Some involved in encoding and retrieval• Some involved in either encoding or retrieval
• Comprising multiple functions that must interact dynamically with one another
CMF Neuroanatomy
• The hippocampal formation ‘Indexing’ of episodes: exactly how is unknown Necessary both for encoding and retrieval Damage leads to dense retrograde and anterograde
amnesia
• The frontal lobes Strategic control over memory: exactly how is again
unknown! Damage leads to confabulations, delusions, heightened
false memory, source amnesia
• The entire ‘association’ neocortex Representation of experienced content Damage should lead to loss of specific content of prior
episodes
CMF Retrieval Functions
Retrieval ‘focus’
Access to the records of attended information via a retrieval cue (by hippocampal pattern completion)
Inhibition of irrelevant information
Re-activation of episodic content (held in the neocortex)
Monitoring/evaluating retrieval products (prefrontally mediated)
How Many Experiences Have you Had?
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Conway’s SMS Model
The Self Memory System (SMS) has two principle components:-
• 1. Autobiographical knowledge base– organised specifically to support our
sense of self
• 2. The (working) Self– comprises a goal hierarchy, and various
other internal mechanisms
Autobiographical Knowledge Base
‘Self’
Episodic Memory tied to specific experiences
(e.g. the CMF)
Retrieval
Consolidation
Encoding
Self-relatedsemantic knowledge
Abstracted from specificexperiences
Goal Hierarchy
Take a peek inside yourself…
Conceptual Self
Self
Autobiographical Knowledge Base
semantic knowledge
Episodic Memory(CMF)
Key point: the SMS system is ‘goal-driven’
The SMS greatly extends the CMF
• Conway: “all daily experiences are destined to be forgotten”– Unless they support longer-term goals
• In the short term, accurate memories are vital– Where did I leave my keys
• In the long-term, coherence (between goals) is vital– The ‘Husband-Hermit’ or ‘Saint-Sinner’ dilemma
SMS Goals• Short term (e.g. daily)
– Take the car for a service…– Find the keys…– Post the letter…
Overriding principle: accuracy!
• Long-term– Get a job– Learn how to drive– Buy a house– Become a solitary religious hermit– Be a loving husband
• Overriding principle: coherence
But: there is an accuracy-coherence trade-off!
Potential for conflict!
How is the trade-off achieved?
• The goal hierarchy maintains a stable and coherent set of short and long term goals
Goal Hierarchy
Eat and drink (everyday)Keep warm (everyday)
Have a conversation (most days)Watch TV (particular times)
Find the car keys (in 5 minutes)Avoid tripping up (when I walk)
Post the letter (sometime today)Dentist appointment (this week)
Revise (next month)Obtain graduation ball tickets (next few
months)Find a less annoying partner (yesterday!)
Get a 2:1 (next couple of years)Loose weight (before going on holiday)
The SMS: key points
• New memories are not formed ‘automatically’ from our experiences– But, experiences are always encoded (e.g. as per the CMF).
• An ABM is formed (and retrieved) only when the (working) self interacts with the autobiographical knowledge base
– Such interactions are entirely goal-driven
• Hence, specific experiences will be forgotten unless they relevant to a goal - within the goal hierarchy
• Stable self-image emerges from the coherence imposed by the goal hierarchy, perhaps at the expense of accuracy
Autobiographical Knowledge Base
‘Self’
Episodic Memory tied to specific experiences
(e.g. the CMF)
Retrieval
Consolidation
Encoding
Self-relatedsemantic knowledge
Abstracted from specificexperiences
Is this: (1) A scientifically acceptable and (2) A forensically useful model?
Can ERPs reveal exactly what is happening in the brain while people remember their past?
cueonset
Ecphory/inhibition
MonitoringRetrieval Perception/attention
Patterncompletion/
Binding
‘selective attention’
Stimuli
Time 0.1 0.2 0.40.3 0.5 0.70 0.6
Constructive Memory Framework
Focussed Search
Retrieve / Inhibit Monitor
Stimuli
0Time - 1 3 4 65 7 92 8
Retrieval success!!Retrieval failure
ERP correlates of retrieval from long-term memory
Stimuli
Time 0.1 0.2 0.40.3 0.5 0.70 0.6
Ecphory?
Monitoring?
Implicit Memory?
Familiarity?
Donaldson, Allan and Wilding (2003)Mecklinger (2000)Rugg and Wilding (2000)
F-N400
LP effect
RF effect
Content only (versus failure)
Content and Context
LP effect magnitude X content relation
Using ERPs to investigate the notion of encoding-retrieval overlap
1. By manipulating the content of what is encoded and retrieved.
2. By manipulating the timing of encoding and retrieval, to make them coincide.
1. Manipulating Content
• Operationally define different classes of study episode
• Record EEG when instances of each class of episode are recollected
• Form ERPs to each class of recollected episode
• Contrast the magnitude and topography of ERPs for each class of recollected episode
Encoding and Retrieval in vivo…
Olfactory (Gottfried et al, 2004)
and within ‘sensory domain’ too (Woodruff et al., 2005)
MTL
Encoding
MTL
Retrieval
TIMEVisual
Auditory
MTL
Encoding
MTL
Retrieval
Do ERPs revealDo ERPs revealmodality specific retrieval processes?modality specific retrieval processes?
• Subjects SAW and HEARD words at study
• Performed a word-stem (e.g. MOT__) cued recall task
• ERPs were formed to stems completed with Studied SEEN items Studied HEARD items Unstudied NEW items
• ERP retrieval effects for each sensory modality:- SEEN – NEW difference HEARD – NEW difference
Allan, Robb and Rugg (2000), Neuropsychologia, 38 1188-1205.
No!ERPs are insensitive to
differences in modality at retrieval
Recall auditory episodeRecall visual episode
As retrieval ends…
As retrievalbegins…
ERP Modality Experiment: ConclusionsERP Modality Experiment: Conclusions
• Multiple retrieval processes, active at different times– Onset ~ 0.5s after retrieval cue!
• Retrieval of ‘visual’ and ‘auditory’ episodes involves common processes. No evidence for modality specific retrieval processes.
• ERPs reflect a ‘core component’ of retrieval? – Changes in neocortical activity driven by the
Hippocampus during early stages of retrieval (prior to modality specific activations)?
– Or: attention to retrieval products?
Episodic Memory Mechanisms
ConsolidationMechanisms
AttentionalControl
Encoding Storage Retrieval
AttentionalControl
SemanticRecords
PerceptualRecords
Binding
ContextSemanticRecords
PerceptualRecords
Binding
Context
• Gain precise control over the relative timing of events experienced in different modalities.
• Stress the system by forcing it to handle very rapidly changing inputs, to reveal what the temporal limits are.
• Examine resulting performance behaviourally
• And use high temporal resolution neurophysiological data to expose the underlying functional states
2. Can we simultaneously encode and retrieve?
Allan and Allen (2005), Journal of Neuroscience, 25, 8122-9130.
Does encoding temporarily stop when retrieval occurs?
How Many Experiences Have you Had?
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HOUR DAY WEEK MONTH YEAR DECADE
TIME
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of e
piso
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(log)
Visual
Auditory
+/- 200msec period of stimulus onset asynchrony (SOA) jitter, in 10 time bins (41 – 194msec)
E == encode (animacy task)
R == retrieve (old/new recognition)
Key
Phase 1
Phase 2
Phase 3
E E E
R
E
R
E
R R R
3-Phase Dual-task Paradigm3-Phase Dual-task Paradigm
Stimulus-Onset Asynchrony (SOA)
Encode time-line begins
WILD
Retrieve time-line begins
Time controlled ‘jitter’
Expt. 1 SOA range: 50-200msecExpt. 2 SOA range: 50-2000msec
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% c
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Full Hit 71.85 62.66
DA Hit 72.03 49.38
Full CR 79.21 71.04
DA CR 76.88
phase 2 phase 3
Dual-task Performance (Expt. 1)Dual-task Performance (Expt. 1)
Effect of ‘ignoring’ retrieval cues
Retrieval under full attention
Retrieval under distractedattention
LP effect minimal/absent under DA, replaced by F-N400but no reliable topographic differences (Allan and Allen, 2005)
• Encoding stabilised at a temporal gap of ~600msec(see Expt. 2), i.e. just as the ERP effect begins.
– retrieval cue processing is complete.– neocortical trace reactivation has commenced.– so ‘automatic’ encoding of experience can begin again?
• Retrieval shows a subtle alteration towards reliance on familiarity
• Mode-shifting between encoding and retrieval in human memory is relatively sluggish
•The LP effect may reflect the attention paid to retrieval products, not the representational nature of those products
Conclusions
Next week -
Do these ERP effects objectively indicate the presence / absence of an episodic memory?