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Understanding Memory Mechanisms in PTSD: Overview of Dual-Representation Theory and Findings

This lecture focuses on the complexities of memory in Post-Traumatic Stress Disorder (PTSD), exploring the Dual-Representation Theory (DRT) as proposed by Holmes, Brewin, and Hennessy (2003). The presentation begins with an overview of PTSD, including DSM-IV criteria and the significance of traumatic memory. It outlines the dichotomy between Verbal Accessible Memory (VAM) and Situationally Accessible Memory (SAM), explaining their roles in PTSD symptoms. Experimental findings illustrate how memory interference can affect the recall of traumatic experiences, offering insights into therapeutic implications.

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Understanding Memory Mechanisms in PTSD: Overview of Dual-Representation Theory and Findings

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  1. Lecture 22 – Psyco 350, B1Winter, 2011 N. R. Brown Psyco 350 Lec #22– Slide 1

  2. Outline • Memory Issues in PTSD • Background • Dual-representation Theory (& Data) Holmes, Brewin, & Hennessy, 2003 • The Mnemonic Model (& Data) Psyco 350 Lec #22– Slide 2

  3. Post-traumatic Stress Disorder:Background Psyco 350 Lec #22– Slide 3

  4. 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. Psyco 350 Lec #22– Slide 4

  5. DSM-IV Criteria B-F B. reexperiencing of the traumatic event C. avoidance of stimuli associated w/ trauma and numbing of general responsiveness D. increased arousal symptoms present for more than 1 month clinically significant impairment in social, occupational, or other important areas of functioning Psyco 350 Lec #22– Slide 5

  6. Dual- Representation Theory (DRT) Psyco 350 Lec #22– Slide 6

  7. DRT: Holmes, Brewin, & Hennesy (2004) Two type of event information 1. 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” Psyco 350 Lec #22– Slide 7

  8. DRT: SAM on Its Own SAM Retrieval: triggered by exposure to “relevant” cues accessed automatically Reaction to SAM: re-experience event emotion-laden flashbacks strong affective response Psyco 350 Lec #22– Slide 8

  9. DRT: Further Assumptions VAM blocks SAM: controls & contextualizes SAM-based responses WM-systems & the creation SAMs & VAMS: Verbal WM required for VAMs Visuo-spatial WM required for SAMs Psyco 350 Lec #22– Slide 9

  10. DRT: Implications Creation 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 Psyco 350 Lec #22– Slide 10

  11. Testing DRT w/ Dual Task Design General Paradigm: Watch horrific film while engaged in either: (a) spatial task (b) verbal task General Predictions: spatial task  knock out SAM  reduce PTSD symptoms verbal task  knock out VAM  increase PTSD symptoms. Psyco 350 Lec #22– Slide 11

  12. The Experiment(s) Participants: Healthy, young adults  20/group Materials: 12.5 min film – actual traffic accidents Instructions: Watch film for later memory test Psyco 350 Lec #22– Slide 12

  13. The Experiment(s) Concurrent Tasks (between-subjects): Control – no concurrent task Visual-spatial inference – tap out a preseficed pattern on buttons Verbal-interference – count backwards by 3s Main DV: # of intrusive memories recalled in 7-day diary Psyco 350 Lec #22– Slide 13

  14. The Experiment(s) Expectation: Counting interferes w/ VAM creation Tapping interferes w/ SAM creation Prediction: # intrusive memories: counting > control > interference Psyco 350 Lec #22– Slide 14

  15. Results: # of Intrusions • As predicated: • tapping < control Psyco 350 Lec #22– Slide 15

  16. Results: # of Intrusions • As predicated: • tapping < control • counting > control Psyco 350 Lec #22– Slide 16

  17. DRT: Discussion DRT 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? Psyco 350 Lec #22– Slide 17

  18. The Mnemonic “Model” Psyco 350 Lec #22– Slide 18

  19. Rubin, Berntsen, & Klindt-Johansen. (2009) Psychological Review A Memory-based Model of Post-traumatic Stress Disorder: Evaluating Basic Assumptions Underlying PTSD Diagnosis A telling and misleading title. Psyco 350 Lec #22– Slide 19

  20. The “Models” DSM Model Proximal Event: A1 event & A2 reaction Response: Symptoms Mnemonic Model Proximal Event: A1 event & A2 reaction Response: Symptoms Memory for A1& A2 Psyco 350 Lec #22– Slide 20

  21. Support for Mnemonic Position “most direct evidence for ... memory ...as a causal agent is that observation that eliminating or enhancing memory in various ways changes PTSD symptom severity” Psyco 350 Lec #22– Slide 21

  22. Memory & PTSD 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 Psyco 350 Lec #22– Slide 22

  23. Memory & PTSD 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 Psyco 350 Lec #22– Slide 23

  24. Questions 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? Psyco 350 Lec #22– Slide 24

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