November 2005© Chris R. Brewin© Imagery Rescripting and Dual Representation Theory Chris R. Brewin...

November 2005 © Chris R. Brewin©

Imagery Rescripting and Dual Representation

TheoryChris R. Brewin

Traumatic Stress ClinicCamden & Islington Mental

Health and Social Care TrustSubdepartment of Clinical Health Psychology, UCL


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”?


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?


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)


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


Brain systems controlling fear

responses

Sensoryinput

Cortex Hippocampus

AmygdalaFear

system+ ve

+ +ve


Brain systems controlling fear responses

Non-hippocampal route Hippocampal route

• Rapid• Low-level feature &

object detection• Little coding of

context• Low-level pattern

matching system• Activates fear

• Relatively slow• High-level feature

discrimination• Encodes temporal

and spatial context• Can be used flexibly

to increase and decrease fear


Dual representation model

Trauma stimuli

VAMsystem

SAM system

Contents ofconsciousness

Meaninganalysis

ThoughtsRuminationPrimary and secondary emotions

FlashbacksRelivingPrimary emotions


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


Situationally accessible memory (SAM system)

• High levels of fear create indelible non-hippocampally-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


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


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

• 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


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.


Features of ordinary memories vs. flashbacks (proportions of

total text) Ordinary Flashbacks

Content memories

Z

Visual 1.05 3.06

4.82***

Proprioceptive .48 1.39

3.73***

Auditory .40 1.40

4.16***

Olfactory .02 .33

2.90**

Taste .00 .03

1.83

Motion 1.50 3.65

6.53***


Features of ordinary memories vs. flashbacks

Ordinary Flashbacks Content memories Z

Proportion of total text

Mention of death .31 .54

3.58***

Primary emotions .53 1.60

3.74***

Secondary emotions 1.49 .62

3.68***


Task performance during narrative

Cognitive Task Baseline Ordinary Flashback Post-narrative F Memory Memory

Trail-making (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*


Understanding symptomsVAM-related SAM-

related• Ordinary memories• Evaluative thoughts• Concerns about the

future• Secondary emotions

– sadness– guilt

• Flashbacks• Nightmares• Trauma-specific

(primary) emotions– fear– helplessness– horror


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)


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


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


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


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


Many trauma cues, fear system

activated

Sensoryinput

F1-F20

IncompleteVAM memory

F1-F10

SAM memoryF1-F20

Fearsystem

activated


Dual representation model

Trauma stimuli

VAMsystem

SAM system

Contents ofconsciousness

Meaninganalysis

ThoughtsRuminationPrimary and secondary emotions

FlashbacksRelivingPrimary emotions


Many trauma cues, fear system

inhibited

Sensoryinput

F1-F20

CompleteVAM memory

F1-F20

SAM memoryF1-F20

Fearsystem

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


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)


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


Therapy principles

Identify content of flashbacksFocus 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)


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, self-generation, or distinctiveness

Increase distinctiveness through rescripting

Check for avoidance and safety behaviorsCheck for additional triggers with in vivo

exercises


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


“ BibliographyBrewin, 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.

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