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Lecture 22 – Psyco 350, B1Winter, 2011

N. R. Brown

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Outline• Memory Issues in PTSD

• Background• Dual-representation Theory (& Data)

Holmes, Brewin, & Hennessy, 2003• The Mnemonic Model (& Data)

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Post-traumatic Stress Disorder:Background

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DSM-IV Criterion A The person has been exposed to a traumatic event in

which both of the following have been present: 

(1 – The Event) The person experienced, witnessed, or was confronted with an event or events that involved actual or threatened death or serious injury, or a threat to the physical integrity of self or others

(2 – Peritraumatic Reaction) the person's response involved intense fear, helplessness, or horror.

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DSM-IV Criteria B-FB. reexperiencing of the traumatic event C. avoidance of stimuli associated w/ trauma and

numbing of general responsivenessD. increased arousal E. symptoms present for more than 1 monthF. clinically significant impairment in social,

occupational, or other important areas of functioning

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Dual- Representation Theory (DRT)

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DRT: Holmes, Brewin, & Hennesy (2004)

Two type of event information1. Verbally Accessible Memory (VAM)

“ordinary autobiographical memory”requires “high-level of conscious processing”

2. Situationally Accessible Memory (SAM)“stores sensory information, mostly… in the form of visual images”

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DRT: SAM on Its OwnSAM Retrieval:

triggered by exposure to “relevant” cues accessed automatically

Reaction to SAM:re-experience eventemotion-laden flashbacksstrong affective response

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DRT: Further AssumptionsVAM blocks SAM:

controls & contextualizes SAM-based responses

WM-systems & the creation SAMs & VAMS:Verbal WM required for VAMsVisuo-spatial WM required for SAMs

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DRT: ImplicationsCreation of PTSD-evoking representations:

Dissociative reactions to traumatic event knocks-out WM capacity necessary for VAM creation

SAM encoded regardless VAM-less SAMs PTSD symptoms

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Testing DRT w/ Dual Task DesignGeneral Paradigm:

Watch horrific film while engaged in either:(a) spatial task (b) verbal task

General Predictions:spatial task knock out SAM reduce PTSD symptomsverbal task knock out VAM increase PTSD symptoms.

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The Experiment(s)Participants:

Healthy, young adults 20/group

Materials:12.5 min film – actual traffic accidents

Instructions:Watch film for later memory test

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The Experiment(s)Concurrent Tasks (between-subjects):

Control – no concurrent taskVisual-spatial inference – tap out a preseficed pattern on buttonsVerbal-interference – count backwards by 3s

Main DV:# of intrusive memories recalled in 7-day diary

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The Experiment(s)Expectation:

Counting interferes w/ VAM creationTapping interferes w/ SAM creation

Prediction:# intrusive memories:counting > control > interference

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Results: # of Intrusions

Control Tapping

# of

Intru

sion

s

0

1

2

3

4

5

6

7

8

9

10 Exp. 2As predicated:• tapping <

control

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Results: # of Intrusions

Control Tapping

# of

Intru

sion

s

0

1

2

3

4

5

6

7

8

9

10

Control Counting

Exp. 2 Exp. 3As predicated:• tapping <

control• counting >

control

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DRT: DiscussionDRT correctly predictions intrusion patterns.But:• Are these data PTSD-relevant?• If so,

– How do VAM-less SAMs create PTSD?– How do VAMs inhibit SAM-trigged responses?– PTSD in non-humans?

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The Mnemonic “Model”

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A Memory-based Model of Post-traumatic Stress Disorder: Evaluating Basic Assumptions Underlying PTSD Diagnosis

A telling and misleading title.

Rubin, Berntsen, & Klindt-Johansen. (2009) Psychological Review

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The “Models”

DSM ModelProximal Event: A1 event & A2 reaction

Response: Symptoms

Mnemonic Model

Proximal Event: A1 event & A2 reaction

Response: Symptoms

Memory for A1& A2

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“most direct evidence for ... memory ...as a causal agent is that observation that eliminating or enhancing memory in various ways changes PTSD symptom severity”

Support for Mnemonic Position

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Amnesia reduces or eliminates PTSD • Organic amnesia – traumatic brain injury • Pharmacologically-induced amnesia

– Propranolol treatment reduced PTSD symptoms in emergency room patients (Pitman et al, 2002)

• Childhood Amnesia– Before 3: No PTSD– 3-to-7: PTSD symptoms increase w/ age– After 7: PTSD unrelated to age

Memory & PTSD

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PTSD symptoms , as availability of traumatic memory

• Method: correlate Centrality of Event Scale (CES; B&R, 2006, 2007) w/ PTSD symptom.– CES measures importance of traumatic event:

• To personal identity• As a turning point • As a reference point

• Results: r’s ranging from .35 to .51

Memory & PTSD

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• Is the DSM “model” a strawman?• What is required to make the mnemonic

“model” a model?• Does anyone ever consider the material

consequences of traumatic events and their relation to PTSD?

Questions