Erasing False Memories?

A pill to erase memories?

In Jonah Lehrer's cover story in the current issue of WIRED, he surveys research on the feasibility of using drugs to erase traumatic memories. Each time we remember a particular long-term memory, we take it down from the neurological shelf on which it is stored and make it vulnerable to breakage or change. In fact, the scientists featured in Lehrer's piece pose, memories are inevitably altered (not reinforced) each time they are retrieved. To put them back safely on the shelf, even in their new, altered state, our brains apparently need to make some proteins to lock them safely back in place. But if a PTSD patient, say, recalls a traumatic memory and is simultaneously given a drug that blocks protein synthesis where that memory is stored, Wham! the memory gets whacked before it can be put back on the storage shelf. Voila, the PTSD is gone. The leading candidate drug is a form of protein kinase called PKMzeta. Lehrer, and the neuroscientists he profiles in the piece, seem to expect this technique to become precise, reliable, and safe. That remains to be seen.

The piece is provocative and fun, but Lehrer's makes, I think, a weak argument that since memories are all falible and mutable anyway, there's no real problem with erasing the ones we don't like. Sure memories, and the mechanism by which we keep them, are imperfect. That's why we try so hard to anchor the important ones outside of our brains in other ways: by documenting them and by sharing them with others to keep our perceived reality from drifting too far from the historical one. We can't overestimate the importance of preserving our tenuous link to historical reality, though, either as individuals or as a society. In a world as perilous as ours, we can't afford to forget what's really happened. Remembering with fidelity, hard as it is, is key to moving forward safely and successfully. If we start to whack unpleasant memories, we do so at our collective peril.

WE Remember, Because HM Forgot

Henry Gustav Molaison

So many big moments in the history of neuroscience are the products of efforts to understand or treat epilepsy. Look for instance at this fine recent story by Mo Costandi in the Guardian memorializing one of the most important figures in the field, a man who for decades was known simply as HM. Henry Molaison (whose full name was only released upon his death two years ago) had been dogged by seizures since childhood and was so desperate to shake them that, in 1953, he agreed to have his hippocampus removed. His surgeon knew HM's seizures were originating there, but no one knew what the side effects would be. The surgery had its intended effect; his seizures were reduced from dozens a year to about two. But in exchange for that gain, he lost the ability to make new memories, a condition known as severe anterograde amnesia.

The main character in Memento, the excellent movie about an amnesiac driven to keep progressing into the future by preserving his past with Post-Its, annotated Polaroids, and tattoos, was purportedly modeled after Molaison.

Before Molaison, most neuroscientists believed memory to be distributed all through the brain.  The first paper about the case, published by Molaison's  surgeon, William Beecher Scoville, and neuroscientist Brenda Milner (both at the Montreal Neurological Institute) showed that though even without his hippocampus Molaison could still retain small amounts of information for short periods of time, he couldn't store them anywhere before they were supplanted by new ones. This suggested, for the first time, that memory has distinct long- and short-term components. Memory research has never been the same, and today no one doubts the central role of that weird little seahorse-shaped part of the limbic system known as the hippocampus in creating and quickening new memories; it is now arguably the most intensively studied part of the brain.

Molaison died two years ago, at 82, but his brain (still being studied at the Brain Observatory UC San Diego) is still revealing secrets about the nature of memory and what makes it work--and cease working.

It's hard to say where memory research would be today if it weren't for Molaison and his epilepsy; possibly decades behind where it is now.  Let's not forget him...or the many other courageous and generous patients with epilepsy who shed so much light on this field.

Eternal Sunshine of the Traumatized Mind

Terry McDermott's good book, 101 Theory Drive: A Neuroscientist's Quest for Memory, tells the story of Gary Lynch a UC Irvine biologist who's spent his entire career looking for the material basis of memory in the brain. According to Lynch's hypothesis, the brain employs Long Term Potentiation (LTP) to convert experience into lasting synaptic relationships. Once considered fringe, the LTP explanation of memory--physical connections between brain cells are made stronger when they communicate, making subsequent communication more efficient--is now mainstream. But the precise mechanisms remained a mystery until Lynch's lab began to shed light on them in the past few years.

The juice is in the details, but basically Lynch found that synapses change their relationships to their neighbors by changing the shape of their dendritic spines. I'll come back to the book soon (when I finish it), but I have to mention it now because instead of finishing McDermott I just watched Eternal Sunhine of the Spotless Mind, the 2004 Oscar winning movie about memory erasing technology. It's a great film, even more fun to watch than 101 Theory Drive is to read. I can't help drawing a line between the two since Gary Lynch's Big Hope is that by explaining LTP he can then begin to locate individual memories, to make, in his words, a "memory map" of the brain.  That's essentially what Dr. Howard Mierzwiak, played by Tom Wilkinson, does in Eternal Sunshine.  He explains that there is an emotional core which gives away the location of  each of our memories and, out of his shabby little Brooklyn clinic, Mierzwiak maps his patients' painful memories and removes them like errant hairs.

In mid-treatment, Joel Barish (Jim Carrey), who is trying to escape the agony of his broken heart, realizes that his memories are, well, important, even if they hurt. He and his ex, played by Kate Winslet, play hide-and-seek through Barish's memory, hiding (camouflaged by emotional traumas) in unexpected memory regions (like exile under the kitchen table from Barish's childhood) that the good doctor can't find...or can't conscience removing.

 A real memory-altering therapy is being studied at Massachusetts General Hospital, according to an excellent article by Charles Slack in the current issue of Proto.  Harvard psychiatrist Roger Pitman is giving propranolol, a beta-blocker commonly used to regulate heartbeats in arrhythmia patients, to soldiers suffering from Post Traumatic Stress Disorder (PTSD). Propranolol seems to counteract the effect of stress hormones that bloom when traumatic memories are recalled. The test subjects keep the memory, but seem to lose the intense emotion associated with it. Not yet tried, as far as I know, on suffering lovers, like the Jim Carrey and Kate Winslet characters in Eternal Sunshine.  But if it works, its just a matter of time before psychiatrists use it to erase all kinds of memory pain. Imagine the power of  being able to regulate the emotional volume of bad memories. Especially if you had a memory map to guide you. For one thing, you could keep sending traumatized soldiers back into the killing fields again and again. Or hapless romantics back into the battlefields of love.

Good? Bad? I don't know.

Remember to Forget

Mental Floss Magazine posted a fascinating article about super-autobiographical memory last week. The piece profiles four adults who share the ability to recall tiny, seemingly insignificant details from long ago. The possibility that everything we experience is stored somewhere in our brain goes back to experiments by British neurosurgeon Wilder Penfield, who provoked specific, long-forgotten memories in his patients by touching parts of their temporal lobes with an electric probe. One epileptic patient relived a childhood experience of smelling burnt toast each time Penfield stimulated a particular location on her cortex.
     If the people profiled in Mental Floss can control their access to the huge database in their brains, why can’t the rest of us? The coming decades may explain why, or they may show us how we can recover long-forgotten details, too. But I suspect that we will also learn that our ability to forget—to flush destructive or superfluous data or memories--is at least as important as our ability to remember.  Especially if the data we’re talking about contains viral components that can keep our brains pinwheeling while other key bits of data--our lives-- pass us by.  Those of us who can’t remember every episode of Flipper should  thank our lucky stars.
   One hot and relevant area of current research focuses on the role of attention in helping the brain decide what to hold onto and what to flush. Take a look, for instance, at this Journal of Neuroscience paper by Adam Gazzaley and Theodore P. Zanto showing how "top-down" attention is related to memory acquisition. Choosing what to remember and what to let slide sounds good, but  I wonder if our conscious minds can always be trusted to know what's important to remember and what's not?