Transcript Long-term memory

Memory – Outline
• Long-term memory (LTM)
– Types: episodic, semantic
– Stages
• Memory loss (amnesia)
– Brain regions & diseases
• Implicit Long-term memory
• Spatial memory
Possible architecture of:
Long-term Memory
Implicit Memory
Explicit Memory
Motor Skills
Semantic
Memory
Episodic
Memory
?
Affected by Amnesia
Perceptual
learning
Other types
Classical
Conditioning
Episodic Memory = Relational Memory
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•
•
What did you do at home last Wednesday?
A temporal context (last Wednesday)
A physical context (home)
A set of memory events (turkey, annoying parents,
tiredness, watching the game)
A relation between the events and the context
Stages of Explicit Long-Term Memory
Encoding
Acquire information
via perceptual system
Storage
Establish a
‘permanent record’
Retrieval
Reactivate the
permanent record
Object Representation,
based on activation of
perceptual & motor areas
Stimulus
banana
Perceptual
Processes
Episodic
Memory
Encoding
word
action
shape
In Context:
‘today’
‘at home’
location
temporal lobe is the hub that
color
relates all object’s properties
& context into an integrated
A medio-temporal lobe lesion causes Amnesia! memory
Storage of Memories (consolidation)
Episodic
Memory
Encoding
Storage
(Consolidation)
Old memory
(10 years later)
(new memory)
In Context:
‘today’
‘at home’
temporal lobe is the hub that
relates all object’s properties
into an integrated memory
temporal lobe is not needed
anymore
Consolidation hypothesis of amnesia
Episodic
Memory
Encoding
Storage
(Consolidation)
Old memory
(10 years later)
(new memory)
In Context:
‘today’
‘at home’
RECENT
MEMORIES
ARE LOST
temporal lobe is the hub that
relates all object’s properties
into an integrated memory
OLD
MEMORIES
ARE SPARED
temporal lobe is not needed
anymore
Retrograde Amnesia
(Pre-Damage)
Old memory
(spared)
Anterograde Amnesia
(Post-Damage)
Recent memory
(lost)
1960’s
1970’s
New memories
(not encoded)
1980’s
Brain
Damage
(1975)
1990’s
Semantic memory: a deficit in amnesia?
• Semantic memory is usually spared in amnesia
• but most is acquired early in life (‘what’s an apple?’)
• May be it is spared because its an old memory
• Test: would amnesics learn new knowledge?
– ipod
– Britney spears?
‘Elvis’
?
???
‘Chaplin’
1930’s
1950’s
1960’s
1980’s
Brain
Damage
(1970)
???
1990’s
Anatomy of episodic memory
Lateral View
temporal lobe is the hub that
relates all object’s properties
into an integrated concept
Ventral View
Coronal View
Mediotemporal lobe, area
removed in amnesic patient H.M.
Anatomy of episodic memory:
Neuroimaging evidence
Task: Read these
words and try to
remember them
Task: Recall as
many words as
possible
Porcupine
Lawyer
Peace
Simple
Octagon
Walk
..
..
Trigger
Applause
Porcupine
------Peace
----Octagon
Walk
..
..
-------Applause
30’
delay
ENCODING
Method: use fMRI to
measure brain activity
RETRIEVAL
Data analysis:
Contrast brain activity
during encoding of:
words that would later
be recalled (peace)
vs.
words that would be
forgotten (simple)
Results: activation of
hippocampus while
encoding to-be
recalled words (peace)
Anatomy of episodic memory:
Neuroimaging evidence
% of participants
that correctly
recallled the word
hippocampus activity
Conclusion: fMRI in normal subjects provide
convergent evidence for the
role of hippocampus in episodic memory encoding
Results: activation of
hippocampus while
encoding to-be
recalled words (peace)
Anatomy of episodic memory:
evidence from infantile amnesia (?)
• We are unable to recall personal experiences that took
place before about 3 years of age,
• probably because the hippocampus is not yet developed,
so we can’t retain new explicit memories
Neuroanatomy of episodic memory:
Evidence from a famous case
• Patient H.M.
– He suffered from seizures, which were
treated in 1953, at the age of 29, with
– Bilateral removal of medio-temporal lobe
– Surgery led to anterograde amnesia
– He was spared in other domains
• digit span,
• conversation,
• motor learning
– He died in 2008.
Neuroanatomy of episodic memory:
Evidence from a famous case
• Patient H.M.: A detailed
comparison of HM’s brain to
that of normal brain
Causes of Amnesia
Fornix
Mammillary body
(Korsakoff Patients)
Hippocampal formation – HM, Alzheimer’s disease
Coronal View
Causes of Amnesia
Atrophy of mammillary bodies
due to vitamin depletion
(Korsakoff’s syndrome)
Usually in patients with chronic
alcoholism
Mammillary body
Mammillary body
Causes of amnesia
Coronal View
Saggittal Cut
-Lack of Oxygen (Anoxia)
usually due to cardiac arrest
Enlarged view:
Normal hippocampus
Anoxia
Causes of amnesia
Alzheimer’s disease
(midtemporal lobe atrophy)
Coronal view
Lateral view
Dorsal view
Causes of Amnesia:
- Alzheimer’s Disease
• Gradual decline (dementia)
• It affects:
– 13% of > 65 y-old,
– 42% of > 85 y-old
• Brain pathology
– Plaques and tangles
• early = hippocampus,
• later = cortex and others
– Loss of acetylcholine cells
Possible architecture of:
Long-term Memory
Implicit Memory
Explicit Memory
Motor Skills
Semantic
Memory
Episodic
Memory
Affected by Amnesia
Perceptual
learning
Other types
Classical
Conditioning
Implicit memory:
Perceptual priming
Implicit memory: motor sequence learning task
Implicit Memory: Mirror drawing task
Implicit memory: classical conditioning
– Eyeblink response
implicit memory: rule learning
• Tower of Hanoi game
– Amnesics cannot remember playing, but they get faster at
solving the game.
Start Position
Goal 2 (2 moves)
Goal 10 (5 moves)
Implicit memory: Conceptual Priming
• Study phase:
– “is this word pleasant or not? “rape”, “love”, “sincere”, …..”
• Test phase:
A. Free Recall: Name the words on the list
B. Word Stem Completion: Complete “sco_ _ _”
• Results:
A. Impaired free recall, but
B. Normal stem completion:
- as likely as normals to complete stems with studied words
(Graf, Squire, & Mandler, 1984)
Summary
•
Medial Temporal Lobe Amnesics
–
–
•
Explicit memory: unable to create
Implicit memory: relatively intact
So far: single dissociation
–
2 possibilities:
1. Implicit/Explicit 2 independent systems
2. Implicit simply easier, relies on residual processing of a single,
partially damaged system
–
Double dissociation would support claim of 2 independent
systems
Evidence for double dissociation:
Patient MS
– Intractable epilepsy:
– surgery removed right occipital lobe (BA 17,18, part of 19).
– Hemianopic (blind in left field)
Evidence for double dissociation:
Explicit Memory: Recognition Task
– Read 24 words --> delay --> read 48 words
• 24 from study phase,
• 24 new foils
– Task: have you seen this word?
Results:
– Middle Temporal Lobe Amnesics (e.g. HM): impaired
– Visual Cortex lesion (patient MS): normal
Gabrieli et al. (1995)
Evidence for double dissociation:
Implicit Memory: Word-stem completion task
– Read or Listen 24 words (‘colt’) --> delay --> Read 48 word-stems (‘co__’)
• 24 from study phase, (e.g., ‘co___’)
• 24 new unrelated stems (e.g., ‘li__”)
– Task: complete word stem
Results:
– Healthy adults: Visual Priming
(faster reading of previously read words than previously heard words).
– Middle Temporal Lobe Amnesics (HM): Visual Priming
– Visual Cortex Lesion (MS): no Visual Priming
– Conceptual priming (across-domains) is spared in all groups
Gabrieli et al. (1995)
Evidence for double dissociation:
• Summary
– Visual cortex lesion (patient MS):
• Spared Explicit memory
• Impaired visual priming
– Middle temporal lobe lesion (patient HM, Alzheimer)
• Impaired Explicit memory
• Spared visual priming
– Double dissociation:
• Two independent systems
– one for visual priming (implicit memory),
– the other for explicit memory
Spatial memory
• Anatomy:
– Medial temporal lobe:
• Hippocampus
• Posterior parahippocampal area
• Evidence
– Human Neuropsychology
• HM
• London taxi drivers
– Animal research
Medial temporal lobe (MRI)
Folded shape
stained
hippocampus
3. Posterior 4. Amygdala
1. Hippocampus
2. Perirhinal cortex parahippocampal
cortex
Mastering London Topography Changes
Hippocampal Structure in Taxi Drivers (humans)
Bird species with good spatial memory
have larger hippocampi
Spatial memory:
Animal research
Spatial memory: Animal research
Place fields are stationary over
time
Place cell:
A neuron that becomes active when the animal is in a particular
location in the environment; most typically found in the
hippocampal formation (in dorsal hippoc, which is analogous to
human post hippoc)
Notes
• Episodic Memory: specific personal experiences from a particular
time and place. For example, I remember that “Ted Kennedy died
(last week)”. ‘porcupine was on the list I read 20 mins ago’
• Semantic memory: world knoweldge. The sky is blue. Dogs are
mammals, are pets, have four legs,
• Perceptual learning: getting accustomed to Diego’s accent
• Classical conditioning: pavlov’s dog
Spared slides
Recall vs. Recognition
• Recognition relies on
– Recollection: remembering specific info from the
study episode (i.e., is context dependent
– Familiarity: context free
– Recognition
Amnesia
Other causes of amnesia include
- Anoxia (CA1 atrophy)
Interestingly, a genetic mutation
inactivating NMDA receptors in
CA1 leads to:
-Lack of Long-term potentiation
-Poor spatial memory in the
watermaze
-Large & unfocused spatial
receptive fields
Some strategies for communicating with someone
who has Alzheimer’s Disease
Problem
Strategy
Asking the same questions
over & over
Distract with other subjects,
avoid arguing
Denying memory problems,
blaming others
Don’t force recognition of
memory problems; be
sympathetic
Failing to recognize familiar
people, objects
Agree things look different,
calmly remind
Memory
Retrieval
Sensory
Memory
Short-term
Working
Memory
Long-term
Memory
(knowledge)
Encoding
200 ms
‘Vision’
20 secs
Implicit memory
Working Memory
fMRI study of WM, showing distinct activation to faces and scenes
Working Memory & Long-term memory
in a single task:
the Free Recall Task
(& serial position function)
Subjects:
- hear items (usually 10-40 words), then
- they say or write all the items they can remember, in any order.
Serial Position Function
Probability of
reporting
the item
?
12
………
Position in Original List
30
1. Monster
2. Camera
3. Tricycle
4. Melon
5. Window
6. Guest
7. Quiet
8. Cherish
9. Waiting
10. Rabbitt
11. Computer
12. Child
13. Chicken
14. Ghost
15. Slave
Faster presentation rate
30 secs filled delay
Patient HM
Primacy
Recency
Privileged rehearsal
better LTM encoding
STM contribution
Relational Memory
•
•
•
•
What did you do at home last Wednesday?
A temporal context (last Wednesday)
A physical context (home)
A set of memory events (turkey, annoying
parents, tiredness, watching the game)
A relation between the events and the context
(relational memory)
SPARE SLIDES
From Patterson, 2007, NatNeuroRev
60
Copyright © Allyn & Bacon 2007
61
Copyright © Allyn & Bacon 2007
62
Copyright © Allyn & Bacon 2007
Delayed non-match to sample
• Familiarity vs. explicit memory
Long-term Memory Systems
Implicit Memory
Explicit Memory
Motor Skill
Learning
Priming
Semantic
Memory
Episodic
Memory
Classical
Conditioning
Instrumental
Learning
Chapter 13: Single cell recording
Instrumental learning
Classical Conditioning (associative Learning)
What is the bases of such learning?
Synaptic plasticity: “cells that fire together, wire together” (Donald Hebb)
Long-term potentiation: Following increased input there is a long-term
increase in the excitability of the neuron that receives such input
Long-term potentiation in the rat hippocampus