Last Lecture
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Frontal Lobe Anatomy
Inhibition and voluntary
control
A model task: working
memory
+
This Lecture
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Long Term Memory
 role of hippocampus in consolidation
 role of frontal regions in encoding and
retrieval
 right frontal regions and representation of
self...
Announcements
FINAL EXAM:
 182


Dennison
Wednesday, 4/19
4:00 pm - 6:00 pm.
 Please
contact us immediately if
this poses a conflict.
Long Term Memory and its
Dysfunction
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Memory: the ability to retain & recollect the
contents of our experience
 typically multimodal
 rich in associations
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The ability to acquire new skills & demonstrate
improved performance as a result of
experience.
Human Amnesia
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Anterograde: Inability to acquire NEW memories.
Retrograde: Inability to recollect OLD memories.
Human Amnesia
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Scoville & Milner (1957) H.M.
bilateral removal of
hippocampus (medial
temporal lobes).
Wada testing to avoid
bilateral
hippocampectomies.
Unilateral removals:
material-specific deficit:
(Right- nonverbal; Left:
verbal)
Case H.M.-- PROFOUND ANTEROGRADE
AMNESIA
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High Average intelligence
STM: normal- digit span 7 forward; 5 backward
Can converse normally, perform mental math
No post-operative personality changes
Unable to acquire new memories...
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all modalities
all material (verbal, nonverbal)
names, people, places, events, route finding
all are affected.
Early animal models of HM were
unsuccessful
WHY?
(Hint: remember what happened with
blindsight)
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Testing the wrong type of memory
What Amnesics can learn:
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Milner (1962) mirror drawing
Warrington & Weiskrantz (1968) perceptual
learning (degraded cues, priming)
Weiskrantz & Warrington (1979) classical
conditioning
Types of Long Term Memory
Declarative/Explicit
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consciously accessible
Episodic: personal/public episodes
Semantic: facts, events, routes
Tested with recall / recognition:
 "Have you seen this before?"; "Can you
remember...?"; "Is this one of the items
you studied...?”
Nondeclarative/Procedural/Implicit
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Does not require conscious recollection
Examples:
 conditioning
 skills (motor skills, mirror reading)
 priming (e.g. stem completion)
Skill Acquisition
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Mirror drawing improves
Amnesics = Controls
An example of the dichotomy...
Phase 1
Phase 2
Read & rate words
(living/non):
Lead
Bear
Fear
Work...
EXPLICIT TEST:
"Complete stem with a word you
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just read"
lea_
bea_
OR IMPLICIT TEST: "Complete
stem with first word that
comes to mind"
 lea_ ---> lead or leaf
 bea_ ---> beat or bear
Priming is spared in Amnesia
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Amnesics cannot recall
study items.
But stored
representation is
accessed automatically.
80
70
60
50
40
Controls
Amnesics
30
20
10
0
Cued
Recall
Fill-in
The Hippocampal circuit
& Explicit Memory
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Hippocampus - part of a circuit
with input to & from parietal,
temporal, frontal lobes & limbic
system (amygdala).
Hippocampus
The Hippocampal circuit
& Explicit Memory
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Hippocampus - part of a circuit
with input to & from parietal,
temporal, frontal lobes & limbic
system (amygdala).
CA1 , CA2 , CA3 layers of HPC
form a circuit allowing access
to cortex
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CA1 layer - sensitive to anoxia &
epileptic activity (CASE R.B.)
Damage to HPC or its
inputs/outputs --> LTM
impairment
Role of Hippocampus in
Explicit Memory
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NOT the location of LTM
NOT necessary for retrieval of LTM
NOT the location of STM
HPC: immediate experience --> LT memories CONSOLIDATION
Explicit memory - stores single events w/ context.
Learning is fast (one-trial learning-- but forgetting endures).
Representations are
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accessible by various cognitive systems
modality-general
give rise to sense of familiarity.
Implicit memory...
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Reactivation of the processing structures engaged
during learning.
Learning is incremental, gradual, slow
Representations are specific to a task and or the
learning modality.
Involves multiple systems (cortex, basal ganglia)
More on the encoding and retrieval of explicit LTM...
Frontal Contributions to LTM
Recency Judgments
knowledge of temporal
context
 give a list of items
 probe w/ two items
asking:
“Which one of
these items
came most
recently?”
Frontal Contributions Source Memory
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ability to identify
(remember) the context in
which a memory was
acquired
task: judge which of two
characters uttered a
particular fact.
Mt. Everest
Keeps growing
90
80
Controls
Frontal
70
60
50
40
30
20
10
0
True/False
Psyd/Hypno
Marco Polo
was Venetian
HERA: Hemispheric Encoding/Retrieval
Asymmetry
(Tulving et al., 1994)
PET studies w/normal subjects show
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Left Hem. is critical to encoding
into LTM
 Lateral Prefrontal areas
 all materials: verbal & nonverbal
 Why? associating meaning with
events
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Right Hem. is critical to retrieval
from LTM
 Lateral Prefrontal areas
 all materials: verbal &
nonverbal
 Why? memory requires reflection
about self / personal experience
Right Frontal Lobe & Self
Craik et al., 1999 - PET study with 4 conditions
How well does the word stubborn describe...
You?
 Lee Bollinger?
 How socially desireable?
 How many syllables?
RESULT: Only self-referential instruction activated Right
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prefrontal cortex ( same areas activated by memory retrieval)
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Conclusion: Right frontal regions are important for
representation of self.
Memory Summary
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WM vs. LTM
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Explicit (personal episodes, semantics/facts)
 Amnesia -- anterograde or retrograde
 Establishing new explicit memories requires
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LTM: IMPLICIT vs. EXPLICIT
encoding, consolidation, retreival
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hippocampus -- consolidation (HM & RB)
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HERA:
 Left frontal- encoding (context info)
 Right frontal- retrieval (self)