Soldiers with PTSD see a world full of threat : MEG reveals enhanced tuning to combat-related cues Todd, Rebecca M.; MacDonald, Matt J.; Sedge, Paul; Robertson, Amanda; Jetly, Rakesh; Taylor, Margot J.; Pang, Elizabeth W.
Background. Post-traumatic stress disorder (PTSD) is linked to elevated arousal and alterations in cognitive processes. Yet whether a traumatic experience is linked to neural and behavioural differences in selective attentional tuning to traumatic stimuli is not known. The present study examined selective awareness of threat stimuli and underlying temporal-spatial patterns of brain activation associated with PTSD. Methods. Participants were 44 soldiers from the Canadian Armed Forces, 22 with PTSD and 22 without. All completed neuropsychological tests and clinical assessments. Magnetoencephalography (MEG) data were collected while participants identified two targets in a rapidly presented stream of words. The first target was a number and the second target (T2) was either a combat-related or neutral word. The difference in accuracy for combat-related vs. neutral words was used as a measure of attentional bias. Results. All soldiers showed a bias for combat-related words. This bias was enhanced in the PTSD group, and behavioural differences were associated with distinct patterns of brain activity. At early latencies non-PTSD soldiers showed activation of midline frontal regions associated with fear regulation (90-340ms after T2 presentation), whereas those with PTSD showed greater visual cortex activation linked to enhanced visual processing of trauma stimuli (200-300ms). Conclusions. These findings suggest that attentional biases in PTSD are linked to deficits in very rapid regulatory activation observed in healthy controls. Thus, sufferers with PTSD may literally see a world more populated by traumatic cues, contributing to a positive feedback loop that perpetuates the effects of trauma.
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