Future Imagining And Episodic Memory
Neuroimaging and lesion studies suggest that imagining the future (i.e. envision future personal experiences) is strongly connected with retrospective memory (i.e. remembering past experiences). Two recent papers published on Neuropsychologia investigated the relationship of retrospective memory and future imagining, as well as their common neural correlates.
Kwan, Carson, Addis, and Rosenbaum (2010) report the case of H.C., a young woman with developmental amnesia associated with bilateral hippocampal loss. Episodic memory seems to depend on hippocampal function (Yancey & Phelps, 2001; Maguire, 2001). Compared to matched controls H.C. was found to be impaired both in tasks requiring past and future event generation. Her performance was similarly deficient in both tasks. According to Kwan and colleagues:
These results indicate that mental time travel can be compromised in hippocampal amnesia, whether acquired in early or later life, possibly as a result of a deﬁcit in reassembling and binding together details of stored information from earlier episodes
Maguire, Vargha-Khadem, and Hassabis (2010) report the cases of two patients (P01 and Jon) with dense amnesia and 50% volume loss in both hippocampi. P01 suffered from adult-acquired amnesia, but unlike previously reported cases was found to be unimpaired at future imagining tasks. The authors suggested that P01 could have been an atypical case, and in order to investigate this they identified another patient with similar neuropsychological profile, Jon. In spite of his dense amnesia, Jon was able to imagine future experiences in a comparable manner to control participants. According to one of the possible explanations proposed by Maguire and colleagues:
Activity in their residual hippocampal tissue supports the ability to imagine new scenarios, and that this is the key feature. Residual hippocampal tissue was active in both patients and in similar circumstances to control participants. Whilst we cannot deﬁnitely relate function to these hippocampal activations, we suggest the activations might indicate some preserved hippocampal function which is also sufficient to support their preserved ability to imagine scenarios
Kwan, D., Carson, N., Addis, D., & Rosenbaum, R. (2010). Deficits in past remembering extend to future imagining in a case of developmental amnesia Neuropsychologia, 48 (11), 3179-3186 DOI: 10.1016/j.neuropsychologia.2010.06.011
Maguire, E., Vargha-Khadem, F., & Hassabis, D. (2010). Imagining fictitious and future experiences: Evidence from developmental amnesia Neuropsychologia, 48 (11), 3187-3192 DOI: 10.1016/j.neuropsychologia.2010.06.037