相关英文原文阅读 | There is a 41-year-old woman, an administrative assistant from California known in the medical literature only as "AJ," who remembers almost every day of her life since age 11. There is an 85-year-ol man, a retired lab technician called "EP," who remembers only his most recent thought. She might have the best memory in the world. He could very well have the worst. AJ and EP are extremes on the spectrum of human memory. And their cases say more than any brain scan about the extent to which our memories make us who we are. Though the rest of us are somewhere between those two poles of remembering everything and nothing, we’ve all experienced some small taste of the promise of AJ and dreaded the fate of EP. Those three pounds or so of wrinkled flesh balanced atop our spines can retain the most trivial details about childhood experiences for a lifetime but often can’t hold on to even the most important telephone number for just two minutes. Memory is strange like that. What is a memory? The best that neuroscientists can do for the moment is this: A memory is a stored pattern of connections between neurons in the brain. There are about a hundred billion of those neurons, each of which can make perhaps 5,000 to 10,000 synaptic connections with other neurons, which makes a total of about five hundred trillion to a thousand trillion synapses in the average adult brain. By comparison there are only about 32 trillion bytes of information in the entire Library of Congress’s print collection. Every sensation we remember, every thought we think, alters the connections within that vast network. Synapses are strengthened or weakened or formed anew. Our physical substance changes. Indeed, it is always changing, every moment, even as we sleep. A Canadian neurosurgeon named Wilder Penfield thought he’d proved that theory by the 1940s after using electrical probes to stimulate the brains of epileptic patients while they were lying conscious on the operating table. He was trying to pinpoint the source of their epilepsy, but he found that when his probe touched certain parts of the temporal lobe, the patients started describing vivid experiences. When he touched the same spot again, he often elicited the same descriptions. Penfield came to believe that the brain records everything to which it pays any degree of conscious attention, and that this recording is permanent. Most scientists now agree that the strange recollections triggered by Penfield were closer to fantasies or hallucinations than to memories, but the sudden reappearance of long-lost episodes from one’s past is an experience surely familiar to everyone. Still, as a recorder, the brain does a notoriously wretched job. Tragedies and humiliations seem to be etched most sharply, often with the most unbearable exactitude, while those memories we think we really need—the name of the acquaintance, the time of the appointment, the location of the car keys—have a habit of evaporating. Michael Anderson, a memory researcher at the University of Oregon in Eugene, has tried to estimate the cost of all that evaporation. According to a decade’s worth of "forgetting diaries" kept by his undergraduate students (the amount of time it takes to find the car keys, for example), Anderson calculates that people squander more than a month of every year just compensating for things they’ve forgotten. It would seem as though having a memory like AJ’s would make life qualitatively different—and better. Our culture inundates us with new information, yet so little of it is captured and cataloged in a way that it can be retrieved later. What would it mean to have all that otherwise lost knowledge at our fingertips? Would it make us more persuasive, more confident? Would it make us, in some fundamental sense, smarter? To the extent that experience is the sum of our memories and wisdom the sum of experience, having a better memory would mean knowing not only more about the world, but also more about oneself. How many worthwhile ideas have gone unthought and connections unmade because of our memory’s shortcomings? After Simonides’ discovery, the art of memory was codified with an extensive set of rules and instructions by the likes of Cicero and Quintilian and in countless medieval memory treatises. Students were taught not only what to remember but also techniques for how to remember it. In fact, there are long traditions of memory training in many cultures. The Jewish Talmud, embedded with mnemonics—techniques for preserving memories—was passed down orally for centuries. Koranic memorization is still considered a supreme achievement among devout Muslims. Traditional West African griots and South Slavic bards recount colossal epics entirely from memory. K. Anders Ericsson, a professor of psychology at Florida State University, believes that at bottom, AJ might not be all that different from the rest of us. After the initial announcement of AJ’s condition in the journal Neurocase, Ericsson suggested that what needs to be explained about AJ is not some extraordinary, unprecedented innate memory but rather her extraordinary obsession with her past. People always remember things that are important to them. Baseball fanatics often have an encyclopedic knowledge for statistics, chess masters often remember tricky gambits that took place years ago, actors often remember scripts long after performing them. Everyone has got a memory for something. Ericsson believes that if anyone cared about holding on to the past as much as AJ does, the feat of memorizing one’s life would be well within reach. Harvard psychologist Daniel Schacter has developed a taxonomy of forgetting to catalog what he calls the seven sins of memory. The sin of absentmindedness: Yo-Yo Ma forgetting his 2.5-million-dollar cello in the back of a taxi. The Vietnam War veteran still haunted by the battlefield suffers from the sin of persistence. The politician who loses a word on the tip of his tongue during a stump speech is experiencing the sin of blocking. Though we curse these failures of memory on an almost daily basis, Schacter says, that’s only because we don’t see their benefits. Each sin is really the flip side of a virtue, "a price we pay for processes and functions that serve us well in many respects." There are good evolutionary reasons why our memories fail us in the specific ways they do. If everything we looked at, smelled, heard, or thought about was immediately filed away in the enormous database that is our long-term memory, we’d be drowning in irrelevant information. Within the past decades, drug companies have elevated the search to brave new heights. Armed with a sophisticated understanding of memory’s molecular underpinnings, they’ve sought to create new drugs that amplify the brain’s natural capacity to remember. In recent years, at least three companies have been formed with the express purpose of developing memory drugs. One of those companies, Cortex Pharmaceuticals, is attempting to develop a class of molecules known as ampakines, which facilitate the transmission of the neurotransmitter glutamate. Glutamate is one of the primary excitatory chemicals passed across the synapses between neurons. By amplifying its effects, Cortex hopes to improve the brain’s underlying ability to form and retrieve memories. When administered to middle-age rats, one ampakine was able to fully reverse their age-related decline in the cellular mechanism of memory. All of this raises some troubling ethical questions. Would we choose to live in a society where people have vastly better memories? In fact, what would it even mean to have a better memory? Would it mean remembering things only exactly as they happened, free from the revisions and exaggerations that our mind naturally creates? Would it mean having a memory that forgets traumas? Would it mean having a memory that remembers only those things we want it to remember? Would it mean becoming AJ? |
