title: Intrusive memories to traumatic footage: the neural basis of their encoding and involuntary recall.
abstract: BACKGROUND
  A hallmark symptom after psychological trauma is the presence of intrusive memories. It is unclear why only some moments of trauma become intrusive, and how these memories involuntarily return to mind. Understanding the neural mechanisms involved in the encoding and involuntary recall of intrusive memories may elucidate these questions.
  
  
  METHODS
  Participants (n = 35) underwent functional magnetic resonance imaging (fMRI) while being exposed to traumatic film footage. After film viewing, participants indicated within the scanner, while undergoing fMRI, if they experienced an intrusive memory of the film. Further intrusive memories in daily life were recorded for 7 days. After 7 days, participants completed a recognition memory test. Intrusive memory encoding was captured by comparing activity at the time of viewing 'Intrusive scenes' (scenes recalled involuntarily), 'Control scenes' (scenes never recalled involuntarily) and 'Potential scenes' (scenes recalled involuntarily by others but not that individual). Signal change associated with intrusive memory involuntary recall was modelled using finite impulse response basis functions.
  
  
  RESULTS
  We found a widespread pattern of increased activation for Intrusive v. both Potential and Control scenes at encoding. The left inferior frontal gyrus and middle temporal gyrus showed increased activity in Intrusive scenes compared with Potential scenes, but not in Intrusive scenes compared with Control scenes. This pattern of activation persisted when taking recognition memory performance into account. Intrusive memory involuntary recall was characterized by activity in frontal regions, notably the left inferior frontal gyrus.
  
  
  CONCLUSIONS
  The left inferior frontal gyrus may be implicated in both the encoding and involuntary recall of intrusive memories.
authors.affiliation: Department of Psychiatry,University of Oxford,Warneford Hospital,Oxford OX3 7NG,UK.
authors.forename: I A
authors.initials: IA
authors.lastname: Clark
authors.affiliation: Medical Research Council Cognition and Brain Sciences Unit,15 Chaucer Road,Cambridge CB2 7EF,UK.
authors.forename: E A
authors.initials: EA
authors.lastname: Holmes
authors.affiliation: Department of Psychiatry,Oxford Centre for Human Brain Activity (OHBA),Warneford Hospital,Oxford OX3 7NG,UK.
authors.forename: M W
authors.initials: MW
authors.lastname: Woolrich
authors.affiliation: Department of Psychiatry,University of Oxford,Warneford Hospital,Oxford OX3 7NG,UK.
authors.forename: C E
authors.initials: CE
authors.lastname: Mackay
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D061212:Memory, Episodic; D011939:Mental Recall; D017397:Prefrontal Cortex / Q000503:physiopathology*; D000067073:Psychological Trauma / Q000503:physiopathology*; D013313:Stress Disorders, Post-Traumatic / Q000523:psychology; D013702:Temporal Lobe / Q000503:physiopathology*; D006113:United Kingdom; D055815:Young Adult
keywords: Dorsolateral prefrontal cortex; flashbacks; functional magnetic resonance imaging; intrusive memories; left inferior frontal gyrus