Transcript Traumatic memory

Imagery Rescripting and Dual
Representation Theory
Chris R. Brewin
Traumatic Stress Clinic
Camden & Islington Mental Health
and Social Care Trust
Subdepartment of Clinical Health
Psychology, UCL
November 2005
© Chris R. Brewin©
Little understanding of
PTSD treatment
• Why are both exposure and cognitive
methods effective?
• Do they work the same way? (associative
processes vs. explicit verbal reasoning)
• What is “emotional processing” and does it
provide an adequate basis to explain how
trauma treatment works?
• Are memories in fact “processed” or
“transformed”?
November 2005
© Chris R. Brewin©
Things to explain
• Different types of memory
– ordinary memories
– flashbacks
• Normal recovery processes
• What goes wrong in PTSD?
• What’s so special about constructing a
trauma narrative?
November 2005
© Chris R. Brewin©
Single vs. dual
representations
•The standard view (e.g. Foa): trauma memories
are fragmented; narratives must be organised
•Dual representations (Janet, Brown & Kulik,
Pillemer): separate image-based representations
(highly sensory, automatic retrieval, reliving) and
verbal representations (under conscious control,
can be edited)
November 2005
© Chris R. Brewin©
Two systems of reasoning
•One is associative and automatic. It computes
similarities and differences between inputs and
stored information
•The other is rule-based and deliberate. The world
is described in conceptual terms by describing a
process that is logical or causal
November 2005
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Brain systems controlling fear responses
Cortex
Sensory
input
Hippocampus
+
Amygdala
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© Chris R. Brewin©
+ve
+ ve
Fear
system
Brain systems controlling fear responses
Non-hippocampal route
• Rapid
• Low-level feature &
object detection
• Little coding of context
• Low-level pattern
matching system
• Activates fear
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Hippocampal route
• Relatively slow
• High-level feature
discrimination
• Encodes temporal and
spatial context
• Can be used flexibly to
increase and decrease
fear
© Chris R. Brewin©
Dual representation model
VAM
system
Trauma
stimuli
Contents of
consciousness
Meaning
analysis
SAM
system
November 2005
Thoughts
Rumination
Primary and
secondary
emotions
Flashbacks
Reliving
Primary
emotions
© Chris R. Brewin©
Verbally Accessible Memory
(VAM system)
• Information initially stored in hippocampus
• Through rehearsal becomes consolidated into
the long-term autobiographical memory store
• Memory enhanced by moderate levels of
arousal but impaired by very high arousal
• Constructive process supporting explicit
memory, strategic retrieval, meaning-making,
sense of self, and social interaction
November 2005
© Chris R. Brewin©
Situationally accessible memory
(SAM system)
• High levels of fear create indelible nonhippocampally-based representations
• Remains informationally isolated (dissociated)
• Triggered automatically in all-or-none fashion
• Unresponsive to social situations
• Supports flashbacks, performance on implicit
memory tasks
• Information directed very rapidly to amygdala
November 2005
© Chris R. Brewin©
Is this the same as implicit and explicit
memory?
• No, because implicit memory does not have a
conscious component. In contrast, flashbacks
usually involve conscious awareness of the
trauma
• At the same time the SAM system has many
characteristics usually ascribed to implicit
memory
November 2005
© Chris R. Brewin©
Characteristics of VAMs and
SAMs
VAMs
SAMs
• Integrated with and
interact with other
autobiographical data
• Can be retrieved and
edited
• Sense of context
including present and
past
November 2005
• Reliving in present
• Fragmented sensory
data or ‘video clips’
• Absence of context
• Do not interact with
autobiographical
memory system
• Cannot be directly
retrieved or edited
© Chris R. Brewin©
A narrative study of ordinary memories
and flashbacks (Hellawell & Brewin,
2002, 2004)
57 patients with a DSM-IV diagnosis of PTSD completed a
written narrative of their traumatic event (26 combat
veterans, 22 assault victims, and 9 accident victims). After
completing the narrative patients identified those sections
corresponding to flashbacks and ordinary memories. Word
counts were conducted on these sections and proportional
scores calculated to correct for the total number of words
used in flashback and ordinary memory sections.
November 2005
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Features of ordinary memories vs.
flashbacks (proportions of total text)
Ordinary
Content
Visual
Proprioceptive
Auditory
Olfactory
Taste
Motion
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Flashbacks
memories
1.05
.48
.40
.02
.00
1.50
© Chris R. Brewin©
Z
3.06
1.39
1.40
.33
.03
3.65
4.82***
3.73***
4.16***
2.90**
1.83
6.53***
Features of ordinary memories vs.
flashbacks
Content
Ordinary
memories
Flashbacks
Proportion of total text
Mention of death
.31
Primary emotions
.53
Secondary emotions 1.49
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© Chris R. Brewin©
.54
1.60
.62
Z
3.58***
3.74***
3.68***
Task performance during
narrative
Cognitive Task
Baseline
Ordinary
Memory
Flashback
Memory
Post-narrative
F
Trailmaking
(seconds)
51.08a 43.38b 52.10a 32.81c 16.86*
Oral
subtraction
(no. correct)
20.21a 18.64b 18.86b 21.40a 7.86*
November 2005
© Chris R. Brewin©
Understanding symptoms
VAM-related
SAM-related
• Ordinary memories
• Evaluative thoughts
• Concerns about the
future
• Secondary emotions
– sadness
– guilt
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• Flashbacks
• Nightmares
• Trauma-specific
(primary) emotions
– fear
– helplessness
– horror
© Chris R. Brewin©
Specific responses in PTSD
• The trauma threatens identity through its
potential impact on the integrity of the body, of
the mind, or of important relationships
• The release of hormones such as cortisol impair
functioning of brain structures such as the
prefrontal cortex and hippocampus that are
critical for memory and identity
• This is experienced as a disruption to identity
(depersonalisation) or to the person’s relation to
the world (derealisation)
November 2005
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Specific responses in PTSD
• Conscious attention is narrowly focussed on
threatening aspects of the situation
• Verbally accessible (VAM) memories dependent
on processing by a sparse network of neurones
in the hippocampus (fast learning system) are
fragmented and incomplete
• Sensory images linked with emotional responses
are recorded in an alternative, fast, situationally
accessible memory (SAM) system not dependent
on hippocampal processing
November 2005
© Chris R. Brewin©
Psychological consequences
• Because image-based (SAM) memories are more
detailed, they are automatically retrieved by a
wider range of trauma reminders
• Because the memories involve lower levels of
information-processing they have no mechanism
for encoding context e.g. time
• When these memories are retrieved they are
therefore reexperienced in the present
• Memories intrude in parallel with other thoughts
November 2005
© Chris R. Brewin©
Normal recovery process 1
• Traumatic information laid down in VAM
(limited) and SAM memory systems
• Over next few days flashbacks lead to
copying of extra information from the
SAM to the VAM system
• Limited capacity system means little
information transferred at one time
November 2005
© Chris R. Brewin©
Normal recovery process 2
• VAM memory creates copies locating
context and time
• Trauma reminders lead to retrieval
competition between SAM memories
and VAM copies
• If good match to SAM memories, VAM
copies begin to inhibit amygdala from
responding inappropriately
November 2005
© Chris R. Brewin©
Many trauma cues, fear system activated
Incomplete
VAM memory
F1-F10
Sensory
input
F1-F20
SAM memory
F1-F20
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© Chris R. Brewin©
Fear
system
activated
Dual representation model
VAM
system
Trauma
stimuli
Contents of
consciousness
Meaning
analysis
SAM
system
November 2005
Thoughts
Rumination
Primary and
secondary
emotions
Flashbacks
Reliving
Primary
emotions
© Chris R. Brewin©
Many trauma cues, fear system inhibited
Complete
VAM memory
F1-F20
Sensory
input
F1-F20
SAM memory
F1-F20
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© Chris R. Brewin©
Fear
system
activated
What goes wrong in PTSD? - 1
• The VAM system fails to make a good
copy of the information in SAM
– impairment of consciousness
– dissociation (induced by helplessness)
– deliberate avoidance
• Information remains isolated in SAM
• When SAMs are triggered the fear
system is not inhibited
November 2005
© Chris R. Brewin©
What goes wrong in PTSD? - 2
• Interference with previous knowledge
or goals, leading to secondary emotions
such as anger or shame
• Intrusion of involuntary VAMs and
related thoughts triggered by external
or internal cues
• VAM intrusions may or may not lead to
repeated SAM intrusions (flashbacks)
November 2005
© Chris R. Brewin©
Therapy - flashbacks and
nightmares
– Detailed oral narrative
– Detailed written narrative
– Prolonged exposure
– EMDR
– Imaginal rescripting
These are all based on an automatic,
associative form of reasoning
November 2005
© Chris R. Brewin©
Therapy principles
Identify content of flashbacks
Focus exposure on these and on other
moments of intense emotion (hotspots)
Modulate arousal so that individual is
fully aware and does not dissociate
(graded exposure, 3rd person
narratives, typing vs. writing)
November 2005
© Chris R. Brewin©
Therapy principles
Develop detailed VAM memory that can
compete with SAMs and has associative links
to safety cues and other memories
Enhance retrievability through practice, selfgeneration, or distinctiveness
Increase distinctiveness through rescripting
Check for avoidance and safety behaviors
Check for additional triggers with in vivo
exercises
November 2005
© Chris R. Brewin©
Recap
• The original memories are not “processed” or
“transformed” but remain intact
• “Processing” consists of the construction of
new memories that are similar enough to be
retrieved by trauma reminders but different
enough to preserve positive feelings
• The principles of constructivism and retrieval
competition provide a parsimonious
explanation of response to treatment
November 2005
© Chris R. Brewin©
“
Bibliography
Brewin, C.R. (2003). Posttraumatic stress disorder: Malady or myth?
New Haven: Yale University Press.
Brewin, C.R. (2001). A cognitive neuroscience account of posttraumatic
stress disorder and its treatment. Behaviour Research and Therapy,
39, 373-393.
Hellawell, S.J. & Brewin, C.R. (2002). A comparison of flashbacks and
ordinary autobiographical memories of trauma: Cognitive resources
and behavioural observations. Behaviour Research and Therapy, 40,
1139-1152.
Hellawell, S.J. & Brewin, C.R. (2004). A comparison of flashbacks and
ordinary autobiographical memories of trauma: Content and
language. Behaviour Research and Therapy, 42, 1-12.
Holmes, E.A., Brewin, C.R., & Hennessy, R.G. (2004). Trauma films,
information processing, and intrusive memory development. Journal
of Experimental Psychology: General, 133, 3-22.
November 2005
© Chris R. Brewin©