What is the difference between remembering an event, imagining it in the future or experience it in the present? Is the completeness and vividness of the present the only difference? A recent paper by L. Nyberg and others has examine the question. The article is behind a pay wall but a good review is available at Physorg (here). Below is the paper’s abstract:

“Mental time travel” refers to conscious experience of remembering the personal past and imagining the personal future. Little is known about its neural correlates. Here, using functional magnetic resonance imaging, we explored the hypothesis that mental time travel into “nonpresent” times (past and future) is enabled by a special conscious state (chronesthesia). Well-trained subjects repeatedly imagined taking one and the same short walk in a familiar environment, doing so either in the imagined past, present, or future. In an additional condition, they recollected an instance in which they actually performed the same short walk in the same familiar setting. This design allowed us to measure brain activity correlated with “pure” conscious states of different moments of subjective time. The results showed that the left lateral parietal cortex was differentially activated by nonpresent subjective times compared with the present (past and future > present). A similar pattern was observed in the left frontal cortex, cerebellum, and thalamus. There was no evidence that the hippocampal region is involved in subjective time travel. These findings provide support for theoretical ideas concerning chronesthesia and mental time travel.

It has to be stressed that all the sessions where imagined whether they were placed in the past, present or future and so there should be very little difference in the content of consciousness, only the time associated with the content changed.

The strongest difference is between the present and not present time. There is much less difference between past and future. It also is interesting that the effect of time travel is so widespread in the brain – at number of processes must have to be aware that this is not a ‘now’ conscious content.