Posttraumatic stress disorder (PTSD) is a debilitating form of mental illness affecting many of our soldiers returning from Iraq and Afghanistan. The proposed study will utilize functional magnetic resonance imaging (fMRI), structural MRI, and diffusion tensor imaging (DTI) to test the hypothesis that soldiers with PTSD show alterations in the function and structure of two key brain areas, the anterior cingulate cortex (ACC) and amygdala, as well as reduced functional and structural connectivity between these areas.
This research will employ two well-validated fMRI tasks: (1) the emotional conflict task investigates temporal dynamics of emotion processing in terms of the impact of conflicting emotional stimuli on the processing of subsequent emotional stimuli (Etkin et al., 2006; Egner et al., 2008); (2) the emotional anticipation task investigates temporal dynamics of emotion processing during the anticipation of and response to emotional stimuli (Nitschke et al., 2006; Mackiewicz et al., 2006). Forty OEF/OIF veterans will be enrolled in this study, with 20 in each of two groups: combat-exposed veterans with PTSD, and veterans with combat exposure but no PTSD. Soldiers with PTSD will receive Cognitive Processing Therapy, a form of psychotherapy shown to be effective for the treatment of PTSD (Monson et al., 2006; Resick et al., 2008). All soldiers with PTSD will be scanned prior to the start of treatment and upon competion of three months of treament.
This design will allow us to examine two important issues regarding treatment: (1) whether pretreatment brain activity predicts response to treatment, as we recently found for generalized anxiety disorder (Nitschke te al. 2009; Whalen et al., 2008); and (2) whether treatment results in the normalization of neural abnormalities identified prior to the start of treatment.
Prior to treatment, we predict that PTSD soldiers will exhibit greater amygdala activity, less ACC activity, and less ACC-amygdala functional connectivity than combat-exposed soldiers without PTSD. These patterns are expected to normalize following treatment. Structural differences at the start of treatment are also hypothesized, with PTSD soldiers expected to show smaller ACC volumes and reduced white matter tracts (structural connectivity) between the ACC and amygdala. Finally, building on our recent findings for generalized anxiety disorder (Nitschke et al., 2009), pretreatment ACC activity is expected to predict better outcomes following three months of treatment.
The discovery of neural abnormalities and the degree of normalization following treatment should add to the body of work already being used in developing new clinical tools for directly targeting specific brain regions in anxiety and depression, such as neurofeedback, transcranial magnetic stimulation, epidural electrocortical stimulation, and deep brain stimulation. Psychotherapy clients may benefit from greater focus of intervention strategies on anticipatory processes or resolving emotional conflict.
The proposed study will have immediate, direct benefits for our returning soldiers suffering from PTSD by providing them with empirically supported efficacious treatment as well as potential long-term benefits by gathering data that further informs understanding of PTSD and how to best treat it.