Brain activation during script-driven imagery induced dissociative responses in PTSD: a functional magnetic resonance imaging investigation

BACKGROUND: The goal of this study was to examine the neuronal circuitry underlying dissociative responses to traumatic script-driven imagery in sexual-abuse-related posttraumatic stress disorder (PTSD). Pilot studies in our laboratory have shown that PTSD patients had very different responses to traumatic script-driven imagery. Approximately 70% of patients relived their traumatic experience and showed an increase in heart rate while recalling the traumatic memory. The other 30% of patients had a dissociative response with no concomitant increase in heart rate. This article focuses on the latter group. METHODS: The neuronal circuitry underlying dissociative responses in PTSD was studied using the traumatic script-driven symptom provocation paradigm adapted to functional magnetic resonance imaging (fMRI) at a 4 Tesla field strength in 7 subjects with sexual-abuse-related PTSD and 10 control subjects. RESULTS: Compared with control subjects, PTSD patients in a dissociative state showed more activation in the superior and middle temporal gyri (BA 38), the inferior frontal gyrus (BA 47), the occipital lobe (BA 19), the parietal lobe (BA 7), the medial frontal gyrus (BA 10), the medial cortex (BA 9), and the anterior cingulate gyrus (BA 24 and 32). CONCLUSIONS: These findings suggest that prefrontal and limbic structures underlie dissociative responses in PTSD. Differences observed clinically, psychophysiologically, and neurobiologically between patients who respond to traumatic script-driven imagery with dissociative versus nondissociative responses may suggest different neuronal mechanisms underlying these two distinct reactions.