Deficits in remembering the past and imagining the future in patients with prefrontal lesions.

OBJECTIVE: Neuroimaging studies suggest that remembering the past and imagining the future engage a common brain network including several areas of the prefrontal cortex. Although patients with prefrontal damage often are described as blind to the future consequences of their decisions, and inclined to 'live in the here and now', little is known as to how the prefrontal cortex mediates past and future mental time travel.

METHOD: Nine patients with prefrontal lesions and nine healthy controls generated past and future events in response to different time periods. Event transcriptions were scored using the Autobiographical Interview protocol (Levine, Svoboda, Hay, Winocur, & Moscovitch, 2002), which provides a reliable system for categorizing internal (episodic) and external (semantic) information. For each event, participants answered a series of questions to assess self-reported phenomenal characteristics.

RESULTS: Patients with prefrontal lesions exhibited deficits in both remembering past events and imagining future events by generating fewer internal details than controls. This effect of group was larger in the past condition than in the future condition. In contrast, no group differences were seen in the number of external details, which were at the same level for patients and controls for both temporal conditions. There were no group differences in ratings of phenomenal characteristics.

CONCLUSION: Our findings suggest that damage to prefrontal structures adversely affects the retrieval of past and the construction of future events. In particular, prefrontal structures are critical for the production of episodic event-specific details when engaging in past and future mental time travel.