Resting metabolic activity in the cingulate cortex and vulnerability to posttraumatic stress disorder

Abstract

Context: Recent neuroimaging research has revealed functional abnormalities in the anterior cingulate cortex, amygdala, and hippocampus in individuals with posttraumatic stress disorder (PTSD).

Objective: To determine whether resting functional abnormalities found in PTSD are acquired characteristics or familial risk factors.

Design: Cross-sectional design including identical twins discordant for trauma exposure.

Setting: Academic medical center.

Participants: Combat-exposed veterans with PTSD (n = 14) and their identical co-twins not exposed to combat (n = 14) as well as combat-exposed veterans without PTSD (n = 19) and their identical co-twins not exposed to combat (n = 19).

Main outcome measures: We used positron emission tomography and fluorodeoxyglucose 18 to examine resting regional cerebral metabolic rate for glucose (rCMRglu).

Results: Veterans with PTSD and their co-twins had significantly higher resting rCMRglu in the dorsal anterior cingulate cortex/midcingulate cortex (dACC/MCC) compared with veterans without PTSD and their co-twins. Resting rCMRglu in the dACC/MCC in unexposed co-twins was positively correlated with combat exposure severity, PTSD symptom severity, and alcohol use in their exposed twins.

Conclusions: Enhanced resting metabolic activity in the dACC/MCC appears to represent a familial risk factor for developing PTSD after exposure to psychological trauma.

Figures

Figure 1

Main effect of PTSD Diagnosis on regional cerebral metabolic rates for glucose (rCMRglu). This image shows resting rCMRglu in dorsal anterior cingulate/mid cingulate cortex that is greater in trauma-exposed twins with PTSD and their unexposed identical co-twins, compared with trauma-exposed twins without PTSD and their identical co-twins. FDG data are superimposed on a standard SPM2 T1 template and displayed according to neurological convention. The accompanying bar graphs present group means; error bars represent standard error of the mean. MNI=Montreal Neurological Institute

Figure 2

rCMRglu correlation between co-twins. Individual subjects’ rCMRglu values from the dorsal anterior cingulate/mid cingulate cortex cluster (k=109) plotted by pairs, with the value of the combat-unexposed (Ux) twin shown on the x-axis and that of the combat-exposed (Ex) twin on the y-axis; open circles represent non-PTSD pairs and closed circles PTSD pairs.

Figure 3

rCMRglu correlations with clinical variables. The scatterplots show the zero-order correlations between rCMRglu values extracted from the dorsal anterior cingulate/midcingulate cortex for combat-unexposed (Ux) co-twins and a.) their own Michigan Alcoholism Screening Test scores, b.) their combat-exposed (Ex) twins’ Michigan alcoholism Screening Test scores; c.) their Ex twins’ combat severity scores, and d.) their Ex twins’ lifetime Clinician-Administered PTSD Scale scores.