Living in the Moment; No Past, No Future
Neuroscientist Kathleen McDermott of Washington University began by quoting famous memory researcher Endel Tulving, who called our ability to remember the past and to anticipate the future “mental time travel.” You don’t use the phrase “time travel” lightly in front of a group of physicists for whom the concept is not a convenient metaphor but a very real possibility. But when you hear about how our minds glide through time—and how our memory provides a link not only to the past but also to the future—you see Tulving’s point.
McDermott outlined the case of Patient K.C., who has even worse amnesia than the better-known H.M. on whom the film Memento was based. K.C. developed both retrograde and anterograde amnesia from a motorcycle crash in 1981. (The literature doesn’t say whether he was wearing a helmet, but let this be a lesson.) He can’t remember anything that happened more than a few minutes ago. He retains facts and skills, but can’t remember actually doing anything or being anywhere.
Tellingly, not only can he not recall the past, he can’t envision the future. When researchers ask him to picture himself somewhere he might go, he says that all he sees is “a big blankness.” Another patient McDermott has worked with can explain the future in the abstract, but says he can’t imagine himself in it.
To investigate the perception of past and future in people without brain injuries, McDermott did fMRI brain scans of 21 college students, asking them to recall a specific incident in their past and then envision themselves in a specific future scenario. Subjectively, the two feel very different. Yet the scans showed the same patterns of activity. Areas scattered all over the brain lit up; our temporal perception is distributed. As a control, McDermott also asked the students to remember events involving Bill Clinton (presumably, ones they were not personally involved in), and the patterns were very different. In a follow-up study, McDermott asked 27 students to anticipate an event in both a familiar and an unfamiliar place. The brain scan for the familiar one resembled the one for the act of remembering; the unfamiliar one was the odd man out.