Any study of memory is, in the main, a study of its frailty. In “Remember,” an engrossing survey of the latest research, Lisa Genova explains that a healthy brain quickly forgets most of what passes into conscious awareness. The fragments of experience that do get encoded into long-term memory are then subject to “creative editing.” To remember an event is to reimagine it; in the reimagining, we inadvertently introduce new information, often colored by our current emotional state. A dream, a suggestion, and even the mere passage of time can warp a memory. It is sobering to realize that three out of four prisoners who are later exonerated through DNA evidence were initially convicted on the basis of eyewitness testimony. “You can be 100 percent confident in your vivid memory,” Genova writes, “and still be 100 percent wrong.”
Forgetfulness is our “default setting,” and that’s a good thing. The sixty or so members of our species whose brains are not sieves have their own diagnosis: highly superior autobiographical memory, or hyperthymesia. While the average person can list no more than ten events for any given year of life, people living with H.S.A.M. “remember in excruciatingly vivid detail the very worst, most painful days of their lives.” The most studied case concerns Solomon Shereshevsky, an early-twentieth-century Russian journalist who, like Borges’s Funes the Memorious, “felt burdened by excessive and often irrelevant information and had enormous difficulty filtering, prioritizing, and forgetting what he didn’t want or need.” Desperate to empty his mind, Shereshevsky practiced, with some success, various visualization exercises: he’d imagine setting fire to his memories or picture them scrawled on a giant chalkboard and then erased. (He also turned to the comforts of the bottle and died of complications from alcoholism, although Genova doesn’t mention this.)
An efficient memory system, Genova writes, involves “a finely orchestrated balancing act between data storage and data disposal.” To retain an encounter, deliberate attention alone will get you most of the way there. “If you don’t have Alzheimer’s and you pay attention to what your partner is saying, you’re going to remember what they said.” (Distracted spouses, take note.) Also, get enough sleep. (An exhausted Yo-Yo Ma once left his eighteenth-century Venetian cello, worth $2.5 million, in the trunk of a New York City yellow cab.) Other strategies include leaning on external cues, such as checklists—every year, U.S. surgeons collectively leave hundreds of surgical instruments inside their patients’ bodies—chunking information into meaningful units, and the method of loci, or visualizing information in a familiar environment. Joshua Foer employed the latter device, also known as a “memory palace,” to win the 2006 U.S. Memory Championship.
The business of “motivated forgetting” is more complicated. Genova advises aspiring amnesiacs to avoid anything that might trigger an unwanted memory. “The more you’re able to leave it alone, the more it will weaken and be forgotten,” she writes. Easier said than done, especially with respect to the recurring, sticky memories that characterize conditions such as P.T.S.D. Here, Genova points to promising therapies that take advantage of the brain’s natural tendency to edit episodic memories with every retrieval. In the safe keeping of a psychiatrist’s office (and sometimes with the benefit of MDMA), a patient deliberately revisits the painful memory “with the intention of introducing changes,” revising and gradually overwriting the panic-inducing memory with a “gentler, emotionally neutral version of what happened.” Not quite “Eternal Sunshine,” but if it works, it works.
Genova, a neuroscientist by training, has spent most of her working life writing fiction about characters with various neurological maladies. Her novel “Still Alice,” from 2007, centered on a Harvard psychology professor who is diagnosed with early-onset Alzheimer’s. In “Remember,” her first nonfiction work, Genova assures her readers that only two per cent of Alzheimer’s cases are of the strictly inherited, early-onset kind. For most of us, our chances of developing the disease are highly amenable to interventions, as it takes fifteen to twenty years for the amyloid plaque that is mounting in our brains to reach a tipping point, “triggering a molecular cascade that causes tangles, neuroinflammation, cell death, and pathological forgetting.” What do those interventions look like? Genova’s guidance is backed by current science, but is mostly just parental: exercise, avoid chronic stress, adopt a Mediterranean diet, and enjoy your morning coffee—but not so much as to compromise deep sleep, which is when “your glial cells flush away any metabolic debris that has accumulated in your synapses.”
One of the more interesting studies that Genova cites followed six hundred and seventy-eight elderly nuns over two decades, subjecting them to all manner of physical and cognitive tests. When a nun died, her brain was collected for autopsy. Curiously, a number of the nuns whose brains showed plaques, tangles, and shrinkage exhibited “no behavioral signs” of Alzheimer’s disease. The researchers theorized that these nuns had a high degree of “cognitive reserve”; they tended to have more years of formal education, active social lives, and “mentally stimulating” hobbies. Even as many old neural pathways collapsed, they were paving “new neural roads” and taking detours along as-yet undamaged connections, thereby masking, if not postponing, the onset of the disease. All pretty straightforward. Now all we have to do is build a society in which everyone has the time and resources for adequate sleep, exercise, nutrition, self-care, and a few good hobbies.