Episodic Future Thinking Following vmPFC Damage: Impaired Event Construction, Maintenance, or Narration?

Objective: Functional neuroimaging and lesion studies show that the ventromedial prefrontal cortex (vmPFC) is implicated in episodic future thinking (EFT), yet its role remains unclear. In this study, we sought to (a) confirm recent findings of impaired EFT in patients with lesions to the vmPFC (vmPFC patients) using a new task, and (b) investigate the influence of nonepisodic mechanisms, namely, narrative construction and working memory maintenance, on vmPFC patients' EFT performance. Method: vmPFC patients and healthy participants imagined future events using pictures as cues, described pictures, or described pictures while maintaining them in working memory after an observation phase. Results: Compared with the controls, vmPFC patients produced less specific reports across all conditions, as indicated by fewer internal (episodic) but a similar number of external (semantic) details. However, controlling for description and working memory performance did not eliminate group differences in EFT. Moreover, vmPFC damage reduced the proportion of internal-to-total details for EFT only. Conclusions: These results indicate that EFT problems in vmPFC patients are not merely the reflection of problems in maintaining in working memory and narrating events, but, more likely, of an impairment upstream, in creating novel events.