Neural activity associated with repetitive simulation of episodic counterfactual thoughts.

When people revisit past autobiographical events they often imagine alternative ways in which such events could have occurred. Often these episodic counterfactual thoughts (eCFT) are momentary and fleeting, but sometimes they are simulated frequently and repeatedly. However, little is known about the neural differences between frequently versus infrequently repeated eCFT. The current study explores this issue. In a three-session study, participants were asked to simulate alternative ways positive, negative, and neutral autobiographical memories could have occurred. Half of these eCFT were repeatedly re-simulated while the other half were not. Immediately after, participants were asked to simulate all these eCFT again while undergoing fMRI. A partial least squares analysis on the resultant fMRI data revealed that eCFT that were not frequently repeated preferentially engaged brain regions including middle (BA 21) and superior temporal gyri (BA 38/39), middle (BA 11) and superior frontal gyri (BA 9), and hippocampus. By contrast, frequently repeated eCFT preferentially engaged regions including medial frontal gyri (BA 10), anterior cingulate cortex, insula, and inferior parietal lobule (BA 40). Direct contrasts for each type of eCFT were also conducted. The results of these analyses suggest differential contributions of regions traditionally associated with eCFT, such as BA 10, anterior cingulate cortex, and hippocampus, as a function of kind of eCFT and frequency of repetition. Consequences for future research on eCFT and rumination are considered.