Mental Time Travel
How does the brain zip back and forth in time?
Posted Dec 23, 2010
Remembering the past and envisioning the future: These are the closest we can get to "time travel," and a new study has investigated how this process works in the human brain.
Results of the study -- performed by Lars Nyberg of Sweden's Umea University, Reza Habib of Southern Illinois University, and Alice S. N. Kim, Brian Levine, and Endel Tulving of the University of Toronto -- appear in a recent issue of the Proceedings of the National Academy of Sciences.
Chronesthesia is the technical term for the brain's ability to maintain simultaneous awareness of past, present and future and to "travel" back and forth between them.
Interviewed by a reporter from PhysOrg.com, Tulving said:
"Mental time travel consists of two independent sets of processes: (1) those that determine the contents of any act of such ‘travel': what happens, who are the 'actors,' where does the action occur; it is similar to the contents of watching a movie - everything that you see on the screen; and (2) those that determine the subjective moment of time in which the action takes place -- past, present, or future.
"In cognitive neuroscience, we know quite a bit (relatively speaking) about perceived, remembered, known, and imagined space," he said. "We know essentially nothing about perceived, remembered, known, and imagined time. When you remember something that you did last night, you are consciously aware not only that the event happened and that you were ‘there,' as an observer or participant ('episodic memory'), but also that it happened yesterday, that is, at a time that is no more. The question we are asking is, how do you know that it happened at a time other than 'now'?"
The study is titled "Consciousness of subjective time in the brain."
The researchers asked participants to repeatedly think about "taking a short walk in a familiar environment in either the imagined past, the real past, the present, or the imagined future." This helped them identify which areas of the brain are linked with thinking about the same event at different times. These are certain regions in the left lateral parietal cortex, left frontal cortex, cerebellum, and thalamus.
Tulving told PhysOrg.com:
"Until now, the processes that determine contents and the processes that determine time have not been separated in functional neuroimaging studies of chronesthesia; especially, there have been no studies in which brain regions involved in time alone, rather than time together with action, have been identified," Tulving said. "The concept of chronesthesia is essentially brand new. ... Therefore, I would say, the most important result of our study is the novel finding that there seem to exist brain regions that are more active in the (imagined) past and the (imagined) future than they are in the (imagined) present. That is, we found some evidence for chronesthesia."