Download Hippocampal Complex

A Cognitive Neuroscience
Perspective on Memory and
Consciousness
Memphis, May 2004.
Types of Memory: Human
Explicit
Episodic
Semantic
Implicit
Perceptual
Conceptual
Motor (procedural)
Types of Memory: NonHuman
[Explicit?]
[Implicit?]
Context-dependent
Habits
Context-free
Motor (procedural)
Brenda Milner
Scoville and Milner (1957)
Penfield and Milner (1958)
HM
From: Corkin et al., Journal of Neuroscience (1997)
“ The record of the stream of consciousness which,
we believe, depends upon the integrity of the
bilateral hippocampal structures cannot be called
into activity voluntarily, except for a relatively short
period of time…Later on, a person deals with what
may be called generalizations, and he can summon
them to his purposes. All events, even “memorable”
ones, slip away from the reach of voluntary recall
unless he has talked about them or preserved them
by reflective reconsideration.
For example, one remembers a song or a poem that
one has heard repeatedly, forgets each hearing or
reading, but remembers the generalization.”
Penfield & Milner, 1958, p 494.
B. Cohesion
A. Encoding
NEOCORTEX
Event
C. Consolidation
Remembering
Event
Event
A
B
C
A
B
C
A
B
C
A
B
C
Hi
HIPPOCAMPAL HIPPOCAMPAL
COMPLEX
COMPLEX
B
A
B
C
A
B
C
B
B
C
Hi
Hi
HIPPOCAMPAL
COMPLEX
A
HIPPOCAMPAL
COMPLEX
HIPPOCAMPAL
COMPLEX
HIPPOCAMPAL
COMPLEX
B. Cohesion
NEOCORTEX
FRONTAL
Event
C. Consolidation
Remembering
Event
Event
A
B
C
A
B
C
A
B
C
A
B
C
Hi
HIPPOCAMPAL HIPPOCAMPAL
COMPLEX
COMPLEX
B
A
B
C
A
B
C
B
A
B
C
Hi
Hi
HIPPOCAMPAL
COMPLEX
FRONTAL
A. Encoding
HIPPOCAMPAL
COMPLEX
HIPPOCAMPAL
COMPLEX
HIPPOCAMPAL
COMPLEX
Working-with-Memory
1. Select and implement encoding
strategies, i.e. organize input to MTL
2. Evaluate & verify output from MTL
3. Determine correct temporal sequence
and spatial context with respect to other
events
4. Use recovered memories to guide
further memory searches, direct
thought, and plan action
Myra Fernandes
Cheryl Grady
Effect of distraction on memory?
• Can you study and watch T.V.?
• Can you write an exam when
– people are talking in the hall?
– there is a noisy fan in the room?
What is the locus of interference?
What does this tell us about the organization of
memory in the brain?
Outline
•
•
•
Divided Attention (DA) technique
A neuropsychological model of memory
Testing the model in young and old adults
• behavioural studies
• neuroimaging studies
•
Other tests of memory and other populations
•
Research in language localization
How do we encode and retrieve
items or events ?
• Measure interference under dual-task
conditions
• Examine how different distracting tasks
affect memory performance
– when performed either at encoding or retrieval
Distracting tasks at encoding or
retrieval
– Card-sorting
– Baddeley et al., 1984
– digit-monitoring
– Fernandes and Moscovitch, 2000, 2002, in press
– visuo-spatial task
– Craik et al., 1996; Anderson et al., 1998
Memory interference
50
40
30
20
10
DA encoding
DA retrieval
0
digits
visual CRT
card sort
Distracting task
Locus of Interference?
• General attentional resources:
– any task interferes with memory
• DA at encoding
• DA at retrieval


A component model of memory
Is retrieval always immune to
disruption?
STRATEGIC
RESOURCES
fruit
carpet
frontal lobes
Temporal lobe/
hippocampus
See Fernandes & Moscovitch, 2000,
2002; Moscovitch, Fernandes & Troyer,
2002 for full discussion
hammer
Method
STUDY
under full or divided attention
list of 16 UNRELATED words /condition
auditory presentation (1 word every 4 sec.)
RETRIEVAL
under full or divided attention
free recall for 60 sec.
Digitmonitoring
Wordmonitoring
97
ladder
63
hammer
35
radio
canary
82
Predictions
• DA at encoding
– Both tasks will interfere with memory
• competition for resources
• DA at retrieval
– only word-monitoring will interfere
• structural interference
Memory interference
DA encoding
DA retrieval
50
40
30
Interference
from DA at retrieval
larger when distracting
task uses same materials
as the memory task
20
10
0
digit
word
Monitoring task
Fernandes & Moscovitch, 2000, JEP:general
A component model of memory
Behavioural results
Memory Interference
40
• N=8 young only
35
30
• Material-specific effect
of DA maintained
25
20
15
– larger interference effect
on memory in DA
animacy blocks
10
5
0
DA digit
DA animacy
Distracting task
Full Attention
relative to DA digits
R
L
Full attention relative
to DA animacy
Left fusiform - greater activation under DA
animacy
Left fusiform greater activation under
DA digits
Right and left superior temporal gyrus,
left amygdala/ parahippocampus, right
hippocampus - LESS activation under
DA animacy
DA digits compared to DA animacy
Right and left parahippocampus LESS activation under DA animacy
R
L
Right (and left) anterior cingulate LESS activation under DA animacy
Memory Consolidation: History
•
•
•
•
•
Ribot (1881)
Müller & Pilzecker (1900)
Burnham (1904)
Russel & Nathan (1947)
Hebb (1949)
Burnham’s (1904) Idea
“The fixing of an impression depends on a
physiological process. It takes time for an
impression to become so fixed that it can be
reproduced after a long interval; for it to become
part of the permanent store of memory
considerable time may be necessary. This we may
suppose is not merely a process of making a
permanent impression upon the nerve cells, but
also a process of association, of organization of the
new impressions with the old ones”
Consolidation Theory or Hypothesis
• Memory formation is a time-dependent process in
which memory is transferred from short- to longterm storage.
• Hippocampus is critical to the process of
transferring information to other (neocortical)
structures.
• Once the consolidation process is complete,
memories can be retained and retrieved directly from
other structures without hippocampal intervention.
PERCENT CORRECT
FAMOUS FACES
DECADE
From: Marslen-Wilson & Teuber, Neuropsychologia (1975).
Rapid Consolidation (Cohesion)
and
Prolonged Consolidation
Autobiographical Memory in People
with Temporal Lobe Epilepsy
Indre Viskontas
Mary Pat McAndrews
Morris Moscovitch
Personal Semantics
Autobiographical Memory- Lifespan
Autobiographical Memory- Early
Robyn Westmacott
Sandra Black
Morris Freedman
Peter Gao
Stefan Kohler
Larry Leach
Sandra Priselac
Jill Rich
Shayna Rosenbaum
Kathy Stokes
Amnesic Patient K.C.
Normal Control Subject
Patient KC: scores on
Autobiographical Memory Interview
Personal
Autobiographical
semantics
Interview
(maximum=21) (maximum=9)
Childhood
16.0
2
Early adult life
13.5
3
Recent life
8.0
1
K.C.'s scores on semantic and episodic variables in the photograph
description task
100%
Score
80%
60%
Semantic
Episodic
40%
20%
0%
Late 50's Early 60's Late 60's Early 70's Late 70's
80's
90's
Names of famous People
1940s: Joseph Cotten; Johnny Longden
1950s: Althea Gibson; Buddy Holly
1960s: Janet Leigh;
Barbara Billinglsly
1970s: Loretta Switt;
Phil Esposito
1980s: Gary Coleman; Ben Johnson
1990s: Tonya Harding; Monica Lewinsky
K.C.'s performance on the
name categorization task
80%
Control
60%
K.C. Guess
K.C. Explicit
40%
20%
0%
19
40
19
45
19
50
19
55
19
60
19
65
19
70
19
75
19
80
19
85
19
90
19
95
-
Percentage Correct
100%
Time Period
Words Entering the Language
1940s: Gasser;
Hep-cat
1950s: Honcho;
Univac
1960s: Hippie;
Psychedelic
1970s: Velcro;
Disco
1980s: Microwave; Nuke
1990s: Homophobia; Viagra
Asaf Gilboa
Cheryl Grady
Gordon Winocur
Morris Moscovitch
Remote Autobiographical
Memory
• Standard model- more neocortical
activation for remote and more hippocampal
activity for recent
• MTT- equivalent activity across time
periods for both cortex and hippocampus
Examples of Stimuli
Self Photo
Other Photo
Procedure
• Subjects instructed to remember and “re-live” the
events portrayed in the “self” photos including
things not directly seen (e.g. weather, emotions)
• For “other” photos they were asked to imagine a
scenario to describe what was seen in the photo
• After scanning people were asked to rate each
photo on a 7-point scale for vividness,
pleasantness, arousal and importance
• Three photos ranked most highly for vividness
from each time period were used for an extended
autobiographical interview
Experiment
• Measure brain activity with fMRI (1.5 T)
• Three to four time periods
–
–
–
–
childhood
teen/ early adult
middle years
Recent
• Photos matched for content as much as
possible
fMRI Design
Self
Other
fix
Self
fix
Other
fix
30 sec stimulus presentation (5 blocks of
each type of photo per run)
6 sec fixation in between each photo
Mid-section showing the retrosplenial and
medial frontal activation
[Rem] - [Rec]
(p<0.005)
Recent photos
(p<0.001)
Remote photos
(p<0.001)
Primary regions activated
Remote events (ROI’s: ITG (37); Medial PFC (10); Retrospl. (31); temporoparietal (39))
X=50
X=28
X=-4
X=-14
X=-40
X=-1
X=-10
X=-35
Recent events:
X=29
X=12
Coronal section showing left hippocampal
activation
(-27 -18 -15)
(-27 -18 -15)
(-29 -19 -15)
t= -7.66
[Rem] - [Rec]
t= 18.54
Recent photos
t= 9.1
Remote photos
Coronal section showing left hippocampal
activation
Remote Events
(-33,-19,-15) t=5.41
Recent Events
(-32,-18,-15) t=9.53
Remote vs. Recent
(-32,-19,-14) t=-3.49
Direct comparison of old photos that were
vividly remembered with photos that were not
Activations in vividly vs. poorly recalled
remote events: Hippocampus
X=-27
Y=-21
Z=-16
Foci of left hippocampal
activations across subjects
Remote events
Recent events
MEMORY DEVELOPMENT
• Initially, memories are episodic and
context-dependent
• Over time, episodic memories are
transformed into semantic memories
• HPC is important for recovering episodic
memories or memories that are linked to
the context in which they were acquired
• RA depends on the type of memory tested
-- not its age.
Elizabeth Warrington
Endel Tulving
Marcel Kinsbourne &
Frank Wood
Semantic and Episodic Memory
are Dissociable
Tulving’s Remember/Know
Distinction
Remember: Re-experiencing,
recollection
Know: Familiarity or semantic
knowledge
NEOCORTICAL MODULES
BBQs
Loves
Semantic
Cycles
Swims
Episodic
HIPPOCAMPAL COMPLEX
NEOCORTICAL MODULES
BBQs
Loves
Semantic
Cycles
Swims
Episodic
HIPPOCAMPAL COMPLEX
NEOCORTICAL MODULES
BBQs
Loves
Semantic
Cycles
Swims
Episodic
HIPPOCAMPAL COMPLEX
“KNOW”
Cue:
NEOCORTICAL MODULES
BBQs
Loves
Semantic
Cycles
Swims
Episodic
HIPPOCAMPAL COMPLEX
NEOCORTICAL MODULES
BBQs
Loves
Paints
Golfs
Semantic
Multiple Trace
Formation
Episodic
HIPPOCAMPAL COMPLEX
NEOCORTICAL MODULES
BBQs
Loves
Paints
Golfs
Semantic
Multiple Trace
Formation
Episodic
HIPPOCAMPAL COMPLEX
NEOCORTICAL MODULES
BBQs
Loves
Paints
Golfs
Semantic
Multiple Trace
Formation
Episodic
HIPPOCAMPAL COMPLEX
“REMEMBER”
Cue:
NEOCORTICAL MODULES
BBQs
Loves
Paints
Golfs
Semantic
Episodic
HIPPOCAMPAL COMPLEX
NEOCORTICAL MODULES
BBQs
Loves
BBQs
Loves
Paints
Golfs
Cycles
Swims
Semantic
Multiple Trace
Formation
Episodic
HIPPOCAMPAL COMPLEX
Items associated with “know” responses
are represented only in semantic memory
and mediated by neocortical modules. Items
associated with “remember” responses have
added representation in episodic memory
mediated by the hippocampal complex
The added representation for “remember”
items should contribute to better performance
over “know” items on a variety of tests
including: naming, classification, and memory
“know”
semantic
knowledge
performance
memory
“remember”
semantic
memory
episodic
memory
knowledge
performance
45-55 year old controls
1400
RT/VOT (msec)
1200
1000
Fame
Judgement
800
Speeded
Reading
600
400
High R
Low R
Non famous
65-80 year old controls
1500
RT/VOT (msec)
1300
1100
Fame
Judgment
900
Reading
700
500
High R
Low R
Non famous
The advantage for remember over know
items should be reduced in people with
episodic memory loss such as medial
temporal lobe amnesia and Alzheimer’s
disease.
AD patients (n=15)
3400
3200
3000
Fame Judgment
Reading
RT (msec)
2800
2600
2400
2200
2000
1800
1600
1400
1200
High R
Low R
Non famous
MTL Amnesic patients (n=4)
1700
Fame
Judgment
RT/VOT (msec)
1500
1300
Reading
1100
900
700
500
High R
Low R
Non famous
The advantage for remember over know
items should be enhanced in people with
semantic
memory
loss
but
relatively
preserved episodic memory, - as in semantic
dementia
SD patients (n=2)
4000
Fame Judgment
Reading
RT (msec)
3500
3000
2500
2000
1500
1000
High R
Low R
Non famous
Summary of Studies of Patients
with Hippocampal Complex
Lesions
•Autobiographical Memory:
Extensive RA, sometimes even
without a temporal gradient
•Semantic Memory:
Limited RA, most often with a
temporal gradient
Multiple Trace Theory of
Hippocampal-Neocortical
Interactions
Autobiographical Memory
1.HP automatically encodes all attended
information
2.Traces are sparsely encoded in distributed
representations which act as pointers to the
neocortical (NC) ensembles which mediate
the attended information.
3.The memory trace consists of the HP-NC
ensemble.
Multiple Trace Theory of
Hippocampal-Neocortical
Interactions (cont’d)
Autobiographical Memory
4.Each re-activation of a memory trace
(recollection or remembering) occurs in
a different context
5.This results in a new sparse
distributed trace in HP and a new HPNC ensemble
6.each such trace shares some NC
representations with previous traces
Multiple Trace Theory of
Hippocampal-Neocortical
Interactions
Semantic Memory
Reactivation of memory traces
accomplishes two things:
(a) slowly instructing the development
of NC traces that reflect the statistical
properties of the world and/or of
memories - the gist is extracted
(b)facilitating link formation between
representations of elements of episodes
Conclusions
1. The Hippocampal Complex is needed for
storage and retrieval of rich,
autobiographical memories as long as they
exist. Such memories are NOT transferred to
neocortex.
2. The HP Complex contributes to the
Neocortical strengthening and development
of semantic memories of words, concepts,
events, people and space - and even the gist
of autobiographical memories.
3.Semantic memories may retain an
autobiographical component which remains
HP dependent.
Overall Conclusion
Hippocampal Complex:
1. Storage and retrieval of detailed,
remote autobiographical and spatial
memories.
2. Support formation and
assimilation of semantic memory in
neocortex and other structures.