In Science this week, MIT neuroscientist Susumu Tonegawa and colleagues describe their recent research illuminating the biological mechanisms behind the sensation of déjà vu. (The journal paper is locked up, but there’s a good Scientific American account of the research.) The authors conclude that a set of neurons located in the hippocampus — specifically in an area called the dentate gyrus — fire to create a blueprint of a particular location. When that neural circuit is triggered incorrectly, set off perhaps by similarity between elements of a new location and one we have been to, we experience the sensation of déjà vu. Tonegawa used a clever mouse model to provide evidence for the hypothesis (from the MIT description):
In experiments with mice genetically engineered to lack a certain gene in the dentate gyrus, Tonegawa and colleagues pinpointed the signaling pathway underlying the recall of specific places.
Different sets of mice were placed in two similar chambers, one of which gave them a mild foot shock. After three days, the mice began to freeze in fear in both chambers, even the one in which they had never been harmed.
Within two weeks, the normal mice learned to associate only one chamber with the foot shocks while recognizing the second as safe. The genetically engineered mice “had a significant but transient deficit in their ability to distinguish similar contexts,” McHugh said.
The theory fits well with the Chris Moulin’s research at the University of Leeds, which I wrote about in the New York Times Magazine last year. The neurons Tonegawa identified in the hippocampus mirror the “recollective experience circuit” that Moulin and his colleagues hypothesized as the source of déjà vécu, a condition of persistent déjà vu: Read More
Here’s the full déjà vu story, for those who don’t have a Times account:
Déjà Vu, Again and Again
Pat Shapiro is a vibrant woman of 77, with silver hair, animated blue eyes and a certain air of elegance about her. She lives with her husband, Don, in a white two-story Colonial in Dover, Mass., a picturesque town set on the Charles River
east west of Boston. After 56 years of marriage, Pat and Don have a playful repartee that borders on “Ozzie and Harriet,” and her still-sharp mind is on display in their running banter. “Don, we haven’t had an ‘icebox’ in years,” she’ll say, interrupting one of his winding stories. “It’s called a refrigerator.”Her short-term memory isn’t quite what it used to be, she says, but it’s nothing that impacts her life. “Her long-term memory is meticulous,” Don says. “She can remember details from our trips to Europe years ago that I can’t.”
Left out of my recent story on déjà vecu were some of the more interesting studies trying to create déjà vu-like sensations in a laboratory, in order to better understand what causes the everyday version of the phenomenon. Akira O’Connor, a grad student of Chris Moulin (the déjà vecu researcher in the article) has had success using hypnosis to create a similar strange sensation of familiarity. Alan Brown at SMU and Elizabeth Marsh at Duke University also have a clever experiment, testing the theory that actual memories can sometimes trigger déjà vu. Here’s my outtake section on the research:
“There is almost a bit of a loneliness about déjà vu to start with,” Akira O’Connor, Moulin’s graduate student, told me one morning at the University. “When you get it, you wonder if you are the only person in the world to have had that feeling.” O’Connor, whose research involves trying to induce déjà vu through hypnosis, was bothered by frequent déjà vus as a teenager. Then he read Joseph Heller’s Catch 22, with its lengthy discussions of what Heller describes as “a weird, occult sensation of having experienced the identical situation before in some prior time or existence.” Reading Catch 22, O’Connor says, “let me know that I wasn’t going mad.”
The worst thing about researching or writing about déjà vu? The jokes. “It’s f*&#ing terrible,” Chris Moulin said when I asked him about the barrage of déjà vu humor faced by any scientist who decides to tackle it as a serious scientific topic. Even I’ve pretty much heard them all over the last couple of months, including from the British customs agent who asked me what my purpose was in the country
“I’m here interviewing a scientist about déjà vu.”
“Déjà vu, eh?” Pause. “Haven’t I seen you here before?”
And then, of course, there is the forever-quoted line from Yogi Berra, “it’s like déjà vu all over again,” and the use of the term to describe anything familiar. Try doing a Google search on it, you’ll get a sense of the frustration that Moulin described to me:
“I get the Google alerts, ‘déjà vu all over again, Yankees beat Red Sox,’” he said. “In Medline or Pubmed, it’s things like ‘Phsophorization and Myelination: Déjà Vu All Over Again.’ It must be hilarious in biochemistry.” Perhaps most frustrating from a scientific perspective, he pointed out, “is that it’s not even bloody déjà vu!”
I should post this twice, just to drive home the point. But you get the idea.