Traumatic memory is a key symptom in psychological trauma victims and may remain vivid for several years. Psychotherapy has shown that neither the psychopathological signs of trauma nor the expression of traumatic memories are static over time. However, few studies have investigated the neural substrates of psychotherapy-related symptom changes.

We studied 16 subthreshold post-traumatic stress disorder (PTSD) subjects by using a script-driven symptom provocation paradigm adapted for single photon emission computed tomography (SPECT) that was read aloud during traumatic memory retrieval both before and after exposure-based and cognitive restructuring therapy. Their neural activity levels were compared with a control group comprising 11 waiting-list subthreshold PTSD patients, who were age- and profile-matched with the psychotherapy group.

Significantly higher activity was observed in the parietal lobes, left hippocampus, thalamus and left prefrontal cortex during memory retrieval after psychotherapy. Positive correlations were found between activity changes in the left prefrontal cortex and left thalamus, and also between the left prefrontal cortex and left parietal lobe.

Neural mechanisms involved in subthreshold PTSD may share neural similarities with those underlying the fragmented and non-verbal nature of traumatic memories in full PTSD. Moreover, psychotherapy may influence the development of a narrative pattern overlaying the declarative memory neural substrates.