Table 3. Twin Analyses: Voxelwise Analyses of Stressful Versus Neutral Imagery in All Participants.
| MNI Coordinates | |||||||
|---|---|---|---|---|---|---|---|
| Comparison | Region | z Score | k | x | y | z | |
| Main Effect of PTSD Diagnosis | |||||||
| P+ > P- | none | - | - | - | - | - | |
| P- > P+ | a priori | none | - | - | - | - | - |
| non-a priori | postcentral gyrus | 4.36 | 12 | -48 | -32 | 42 | |
|
| |||||||
| Main Effect of Exposure | |||||||
| Ex > Ux | none | - | - | - | - | - | |
| Ux > Ex | none | - | - | - | - | - | |
|
| |||||||
| PTSD Diagnosis x Exposure Interaction | |||||||
| ExP+ < all other groups | a priori | ACC | 3.71 | 22 | 10 | 26 | 44 |
| MFG | 3.58 | 31 | -8 | 40 | 46 | ||
| non-a priori | none | - | - | - | - | - | |
Participant Groups:P+ twin pairs in which the exposed twin has PTSD; P- twin pairs in which the exposed twin does not have PTSD; Ex, combat-exposed twins; Ux, combat-unexposed twins
Abbreviations: MNI, Montreal Neurological Institute; k = cluster size at the significance threshold (see below); ACC, anterior cingulate cortex; MFG, medial frontal gyrus.
For a priori regions, a significance threshold was applied at z≥3.29, p≤.0005, 2-tailed.
For non-a priori regions, the applied significance threshold was z≥4.27, p≤.00002, 2-tailed. Significant a priori regions are listed in bold print.