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Memory
• Working Memory
• Long term Memory
– Deficits: HM, Alzheimer’s, Semantic Dementia
• Implicit Memory
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
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
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Faster presentation rate
Patient HM
30 secs filled delay
Primacy
Recency
Privileged rehearsal
better LTM encoding
STM contribution
Types of Knowledge
(long-term memory)
Declarative
Semantic
Memory
2+2, sky is blue
Procedural
Episodic
Memory
The Eagles won; ‘cook’ was a word in the list
Affected by Amnesia
This distinction emphasizes the kind of information represented
(i.e. knowledge reported verbally vs motor skills).
Another Possible architecture of:
Long-term Memory Systems
Implicit Memory
Explicit Memory
Priming
Semantic
Memory
Motor Skill
Learning
Episodic
Memory
2+2, sun is blue
Affected by Amnesia
Classical
Conditioning
Instrumental
Learning
This emphasizes how information is accessed (conscious vs automatic)
Anatomy of
Explicit Memory
Fornix
Posterior
Parahippocampal
cortex
Mammillary
body
Hippocampal formation
Mediotemporal Lobe (MTL)
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
fMRI in normal subjects provide convergent evidence for the
Role of hippocampus on episodic memory
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)
Amnesia
Bitemporal Lobectomy (patient HM)
- treatment for epileptic seizures
- It caused anterograde amnesia, but
normal IQ, digit span, conversation,
motor learning
Impaired Long-term Memory Encoding
(chaplin vs. Britney spears;
Old memories ok)
-Spared Working memory
(digit span, recall)
-Spared Implicit memory
- conceptual
- perceptual
- motor
Implicit memory:
Conceptual Priming in anterograde amnesia
• Study phase: “is this word pleasant or not? “rape”, “love”, “sincere”, …..”
• Test phase:
– Free Recall: Name the words on the list
– Word Stem Completion: Complete “sco_ _ _”
• Impaired recall
but normal stem completion
(i.e., as likely as normals to complete stems
with words that were observed earlier).
(Graf, Squire, & Mandler, 1984)
Implicit memory:
Perceptual priming
Implicit memory motor: sequence learning task
implicit memory: rule learning
• Tower of Hanoi game
– HM cannot remember playing, but solves
quickly.
Start Position
Goal 2 (2 moves)
Goal 10 (5 moves)
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
• Patient MS
– 29 year old, right handed male
– Intractable epilepsy: surgery removed right BA 17,18, part of 19.
– Hemianopic (blind in left field)
• Compared to MTL amnesics and healthy controls.
Explicit memory task
Shown 24 words, later shown 48
words (24 from 1st phase, 24 new
foils): asked to say if words were
previously seen.
Amnesics poor, visual lesion patient
fine.
Gabrieli et al. (1995)
• Implicit memory: word completion task
– Shown/Heard 24 words ‘stick’, later asked to complete 48 stems, 24 could be
solved with items from 1st phase (‘sti__’) and 24 unrelated stems (‘sta__’).
– Healthy people show priming effect (faster if solution seen previously). This
effect is much bigger if words were seen (physical match) rather than heard.
– Amensics show normal priming. Shows implicit memory.
– MS visual priming is no greater than auditory priming. Therefore, shows no extra
benefit for physical match of stem and previously seen word.
Conclusion
Double dissociation
Explicit memory has some distinct processing from
implicit memory.
‘Conceptual’ priming intact in MS, perceptual
priming damaged
Anterograde Amnesia: causes
Fornix
Mammillary body
(Korsakoff Patients)
Hippocampal formation - HM
Other causes of amnesia
include
– Chronic alcoholism (atrophy
of mamillary body due to vitamin
depletion, thiamin)
– Alzheimer’s disease
(midtemporal atrophy)
– Electroconvulsive therapy
– Left frontal stroke (example)
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
Long-term Memory Systems
Implicit Memory
Explicit Memory
Priming
Semantic
Memory
2+2, sun is blue
Motor Skill
Learning
Episodic
Memory
Classical
Conditioning
Instrumental
Learning
Semantic dementia: Loss of semantic memories caused by progressive
degeneration of the neocortex of the left lateral temporal lobe.
Graham et al. 2000
• Graham et al. suggest double dissociation:
– Early Alzheimer's patients
– ‘Semantic dementia’ patients
Alzheimers Patient
Semantic Dementia
Hippocampus atrophy
Temporal lobe atophy
B: Test stimuli
• A: Semantic naming task (‘phone’)
– Correct answer: ‘phone’.
Memory tested 30 minutes later:
• B: Episodic memory task (perceptually
identical)
– Correct answer: ‘I saw a phone earlier’
• C: Episodic memory task (perceptually
different)
– Correct answer: ‘I saw a phone earlier’.
C: Semantic memory
• Semantic
dementia
patients have
difficulty
naming items.
• AD patients are
fine at this task.
D: Episodic memory
• AD patients
– poor episodic memory.
• SD patients
– OK with identical items
– Poor with perceptually
different (especially if
unable to name item in
picture naming phase).
E: Conclusions
• Suggests semantic and episodic memory may be
separate.
– Hippocampal formation: encoding episodic memories
– Temporal lobe: storage of semantic memories.
– Additional support from Vargha-Khadem (1997), who
reports 4 patients with selective hippocampal damage:
all show impaired episodic but intact semantic memory.
• Note: all sustained hippocampal damage early in life, so does
not necessarily generalize to adult brain.
Interaction of different brain
regions
• Lesions in animals and functional imaging suggest
network of regions work together to encode 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)
Contextual information
Spatial alternation task (left, right, left)
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Copyright © Allyn & Bacon 2007
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From Patterson, 2007, NatNeuroRev
From Patterson, 2007, NatNeuroRev
From Patterson, 2007, NatNeuroRev
From Patterson, 2007, NatNeuroRev
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Copyright © Allyn & Bacon 2007
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Copyright © Allyn & Bacon 2007
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Copyright © Allyn & Bacon 2007
Delayed non-match to sample
• Familiarity vs. explicit memory
Long-term Memory Systems
Implicit Memory
Explicit Memory
Priming
Semantic
Memory
Motor Skill
Learning
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-ter
increase in the excitability of the neuron that receives such input
Long-term potentiation in the rat hippocampus