We suggest that basic principles from cognitive science may be used to help develop an intervention for trauma flashbacks, and propose a ‘cognitive vaccine’ approach. That is, that the delivery of specific cognitive tasks may help ‘inoculate’ against the escalation of flashbacks after a traumatic event. Post Traumatic Stress Disorder (PTSD) is a psychiatric disorder that can result from experiencing or viewing a traumatic event involving death, serious injury, or threat to self or others 
. A precursor 
and indeed the hallmark symptom of PTSD 
is vivid flashbacks to the trauma, that is, distressing, re-experiencing of the trauma in the form of intrusive, image-based, sensory-perceptual memories. For example, following a motor vehicle accident, a person may later experience intrusive flashbacks where in their mind's eye they suddenly see a vision of a looming car accompanied by the sound of crashing metal.
Although we have successful treatments for full-blown PTSD, crisis interventions to reduce the build up of symptoms in the early aftermath of trauma are lacking. Current interest in the manipulation of memories post-trauma is particularly focused on pharmacological means, for example, propranolol administration 
. In addition to the potential for side-effects with pharmacological approaches, there are potential ethical concerns if voluntary memories for human experience are suppressed 
. For example, removing flashbacks at the expense of being able to deliberately remember what happened during a trauma could compromise a trauma victim's ability to testify in court. We have also raised clinical concern over treatment innovations stemming from exciting theoretical developments 
but which advocate psychological approaches which promote the suppression of memory for traumatic experiences as way of dealing with negative sequelae, since suppression is clinically contra-indicated 
The psychological intervention with the strongest evidence-base for full-blown PTSD is trauma-focussed Cognitive Behaviour Therapy–a treatment which is only indicated when delivered weeks or months after the trauma 
. However, what can be given to trauma victims suffering flashbacks in the first few weeks? Unfortunately, using talking therapy as a crisis intervention in the immediate aftermath of trauma has caused international clinical concern 
: interventions such as critical incidence stress debriefing can worsen rather than ameliorate later trauma symptoms 
. Given the scale of traumatic events globally–war, terrorism, natural disasters, interpersonal violence–there is a huge unmet need for widely-available and easily accessible interventions. We need to develop fresh theory-driven interventions to reduce the build up of flashbacks in the early post-trauma period.
Can cognitive science suggest a way to reduce the build-up of flashbacks to trauma? We suggest that certain cognitive tasks, informed by the neuropsychological domain of working memory, may indeed be used tap into processes underlying flashback memory consolidation. This is based on two key findings: first, cognitive science has shown the brain has selective resources with limited capacity 
; second, the neurobiology of memory suggests there is a 6-hr window to disrupt memory consolidation 
. In particular, we suggest that visuospatial tasks will be useful in this regard according to the following rationale: (1) trauma flashbacks are sensory-perceptual images with visuospatial components 
. (2) visuospatial cognitive tasks compete for resources with visuospatial images 
. (3) the neurobiology of memory consolidation suggests a 6-hr time frame post-event within which memories are malleable 
. Thus (4) we predict visuospatial cognitive tasks given within 6-hr post-trauma will reduce flashbacks.
Following a long tradition in experimental psychopathology, we use the trauma film paradigm 
in our laboratory as an experimental analog of viewing real trauma and the subsequent flashbacks 
suffered in PTSD. We have previously demonstrated that the frequency of flashbacks for analog traumatic content can be manipulated experimentally by completing standardized cognitive tasks during
trauma film viewing (i.e. peri-traumatically): In healthy participants, completing a complex visuospatial working memory task 
, such as finger pattern tapping, during exposure to a trauma film subsequently reduced flashbacks of that film over 1-week compared to no task, or non-visuospatial tapping 
. Interestingly, and in line with cognitive theories of PTSD 
, verbal cognitive tasks during the film, such as counting backwards in threes, actually increased
the number of flashbacks, confirming that the effects were not simply due to distraction for general working memory resources but to the specific nature of the task 
In the current study it was critical to identify a visuospatial working memory task that would be widely-available in the real-world. Clearly a standard neuropsychological test battery visuospatial task such as the WAIS block design 
would be impractical to deliver en mass. The popular computer game “Tetris” has been demonstrated to be a visuospatial task 
, drawing on mental rotation and the type of processing we recruit when forming mental images. Playing “Tetris” can even result in participants experiencing subsequent visual images of the game itself at a later time 
, implicating its involvement with intrusive, image-based memory. The capacity of visual memory is both limited and vulnerable to proactive interference, i.e. interruption of memory for presented stimuli by the presentation of similar, but different stimuli after a time delay 
. Thus “Tetris” provides a promising candidate. Interestingly, watching violent films and playing prolonged computer games are typically associated with negative impact on psychological well being and behavior in both children and adults 
. This has led to public concern over their ready availability. However, clearly not all computer games are bad for you 
We now report the impact of a cognitive visuospatial task, a computerized mental rotation game, on the modulation of analog flashbacks to trauma. Given our earlier experimental demonstration that engaging in visuospatial tasks peri-traumatically (i.e. during trauma film viewing) reduces subsequent intrusive imagery (analog flashbacks), we tested here whether the window for intervention could be extended into the post-trauma period (i.e. after trauma film viewing). This is a critical question since in real-world trauma successful manipulation of flashbacks would need to be conducted post-event rather than peri-traumatically. Further, investigating a time-frame for intervention in the near aftermath of trauma, yet within a window of memory malleability has clear clinical implications. Recent statistics indicate that the average waiting time in an emergency department in the United States is 30-mins 
. To test the real-world application of our paradigm, we explored the manipulation of flashbacks in the laboratory 30-min after watching a trauma film.
Our suggestion to manipulate flashbacks in the aftermath of a traumatic experience is supported by various experimental demonstrations that newly formed memories are initially labile for a short time and thus subject to interference. In rats, the consolidation of fear memories can be inhibited in a dose dependent fashion with administration of either anisomycin or Rp-cAMPS in the immediate post-training phase 
. Furthermore, even established memories may be subject to manipulation upon reactivation–the triggering of previously consolidated memories may return them to a labile state and in need of reconsolidation
if they are to persist 
. In humans, the consolidation or stabilization of motor memory (in this case, a finger pattern tapping task) has been demonstrated to occur in the first 6-hours following initial learning: learning a new variation on the motor task after reactivation of the previously learned motor task can block the reconsolidation of memory for the original task 
. Although there are doubts as to whether such reconsolidation may occur for all types of memory 
, of particular interest to PTSD research is that flashbacks for trauma may be pharmacologically modulated 
, though this has not been without controversy 
. Given the potential advantages of a non-invasive procedure, we were interested in testing whether a cognitive intervention-a visuospatial task-could modulate later flashbacks to traumatic material.
We predicted that playing a visuospatial computer game requiring mental rotation of shapes (“Tetris” 
), 30-min after viewing graphic and traumatic film footage, would help reduce later involuntary flashbacks of the traumatic material, but leave voluntary memory retrieval intact. Similarly we predicted that playing “Tetris” would be associated with reduced clinical symptomatology at one week.