One of the many rewarding parts of Eternal Sunshine of the Spotless Mind is the fact that the film contains almost no dialogue that sounds like actual neuroscience. The film, as you may already know, tells the story of two star-crossed lovers whose stars have gotten so crossed that they decide to erase their memories of each other, using the services of a company called Lacuna Inc. Lacuna's offices have been cunningly art-directed to look like a low-rent plastic surgeon's, which is precisely the point. Memory erasure, in Eternal Sunshine's world, is just the next logical step up from breast augmentation and Prozac. When Clementine (Kate Winslet's character) first decides to shed her memories of Joel (played by Jim Carrey), she does it "on a lark," the way you might get your forehead Botoxed on a whim. But despite the futurist premise, Sunshine spares us the gratuitous speech explaining How It All Works. There's no animated "Mr. DNA" à la Jurassic Park * or some hopeless jargon about "hacking into the neocortex." The closest you get is a nervous conversation between Joel and his doctor: "Is there any risk of brain damage?" The doctor replies, "Technically speaking, the procedure is brain damage. It's on a par with a night of heavy drinking, nothing you'll miss."
For the record, using today's technology, it is not possible to selectively erase an entire person from your memory. But Eternal Sunshine still demonstrates a remarkably nuanced understanding of how the brain forms memories, particularly memories about intense emotional experiences. The film displays a more subtle model of memory formation than the acclaimed thriller Memento, in which a man incapable of forming long-term memories hunts down a killer; he furiously scribbles clues onto Polaroids before his memory fades to black.
Memento revolved around an older model of memory formation, from the days when the brain was imagined as a wetware computer. The fading of memory in Memento is about the loss of pure information, like an erased hard drive. In Eternal Sunshine, the richness of memory is as much about emotion as raw data. There's a wonderful throwaway line at one point in the film, where Joel is reliving a memory of hiding under the kitchen table as a 4-year-old, calling out for his mother. "I really want her to pick me up," the grown-up Joel says, as he relives the experience. "It's amazing how strong this feeling is."
The emphasis on feeling over data processing puts Eternal Sunshine squarely in the mainstream of the brain sciences today. We now know that the brain stores emotional memories very differently from unemotional ones. Negative emotional memories, for instance, tend to capture more details about the experience than positive ones: You remember the general feeling of a nice day at the beach, but you remember every little detail of the two seconds when that Buick crashed into you back in high school. Particularly traumatic memories appear to be captured by two separate parts of the brain: the hippocampus, the normal seat of memory, and the amygdala, one of the brain's emotional centers. People incapable of forming long-term memories thanks to hippocampal damage can nonetheless form subconscious memories of traumatic events if their amygdala is intact. Someone suffering from the Memento condition would likely have a feeling of general unease encountering a person or a situation that had caused them harm in the past, though they wouldn't be able to put their finger on what was making them uncomfortable. In Eternal Sunshine, something like this happens. There are several instances in the movie where Clementine appears to have a trace emotional memory of an event that has been wiped from her waking mind.
Eternal Sunshine plays on this idea of traumatic memories being stored in separate regions of the brain in another way, too. In the dazzling, mind-bending sequence at the center of the film, as Joel's memories of Clementine are being steadily eliminated, the unconscious Joel decides that he doesn't want to go through with the erasure after all. Unable to wake himself up, he embarks on a kind of psychic journey with a remembered Clementine, trying to escape the high-tech censor that's steadily stripping away his recollection. As the situation gets increasingly desperate, Clementine suggests burying a memory of her in some place in his brain that she doesn't belong, buried far away from the probing scanner. She suggests a moment of intense humiliation from Joel's youth, and in a flash they're in a memory of a Joel's mother walking in on teenage Joel masturbating.
The fact that Joel is re-experiencing these memories as they're being deleted is consistent with one influential recent theory about how targeted memory erasure might be possible.
For a long time, memory researchers assumed that memories were like volumes stored in a library. When your brain remembered something, it was simply searching through the stacks and then reading aloud from whatever passage it discovered. But some scientists now believe that memories effectively get rewritten every time they're activated, thanks to a process called reconsolidation. To create a synaptic connection between two neurons—the associative link that is at the heart of all neuronal learning—you need protein synthesis. Studies on rats suggest that if you block protein synthesis during the execution of learned behavior—pushing a lever to get food, for instance—the learned behavior disappears. It appears that instead of simply recalling a memory that had been forged days or months ago, the brain is forging it all over again, in a new associative context. In a sense, when we remember something, we create a new memory, one that is shaped by the changes that have happened to our brain since the memory last occurred to us.
Theoretically, if you could block protein synthesis in a human brain while triggering a memory, you could make a targeted erasure. The technicians at Lacuna Inc. appear to be doing something along these lines in the film. When Joel first arrives, he's asked to bring in all the objects he associates with Clementine, and he's recorded giving a long description of all his thoughts and feelings about her. While he's exploring these memories of his ex-girlfriend, the techies scan his brain activity with a machine that looks suspiciously like a salon hair dryer but that generates images similar to a real fMRI machine. They refer to this process as making a "map of Clementine." The next day they give Joel some kind of pill that knocks him out and systematically re-triggers all the memories they've recorded. As they're re-triggered, the memories disintegrate while a machine erases them. There's no science babble in the mix, but the basic sequence is broadly compatible with the reconsolidation theory.
Eternal Sunshine of the Spotless Mind is remarkably in sync with modern neuroscience, but in one respect the film put its emphasis in the wrong place. To be fair, it's a failing shared with a host of recent films about memory loss: Memento, 50 First Dates, Paycheck. Selective erasure of memories may not be a feasible procedure in the near future, but cosmetic memory enhancement is likely to be a reality in the next 10 years, just as targeted mood enhancers like Prozac have become commonplace over the past 10. You won't be able to sharpen your memory of a single person, but you may well be able to take a pill that will increase your general faculties of recollection. This is the ultimate irony of Eternal Sunshine and films like it. While the culture frets over the perils of high-tech erasure, we should really be worrying about the opposite: what will happen when we remember too much.