The Magic of Memory —By Laurence Cherry Our memories are probably our most cherished possessions. More than anything else we own, they belong uniquely to us, defining our personalities and our views of the world. Each of us can summon thousands of memories at will: our first day at school, a favorite family pet, a summerhouse we loved. And yet the marvel of memory continues to be a tantalizing (挑逗性的) mystery. Nevertheless, within the past few years great advances have been made in understanding what memory is, how it works, and how it may possibly be improved. 'We're standing at the brink of a whole new era in memory re search,' says Dr. Steven Ferris, a psychologist at the Millhauser Geriatric (老年医学的) Clinic. 'For the first time, there's a general feeling that we're really on the right track.' For years, the prevailing theory was that remembering was somehow connected to electrical activity inside the brain. But within the past decade, it's become clear that chemical changes must also be involved, otherwise our memories could never survive deep-freeze, coma, anesthesia (麻醉) and other events that radically disrupt the brain's electrical activity. Ingenious re search over the past few years has demonstrated that biochemical changes do indeed accompany learning and remembering. In one dramatic experiment, mice, who usually prefer the safety of darkness, were taught to fear the dark and were then killed. Extracts of their brains were injected into untrained mice, and they then began to shun the dark. Other experimenters have shown that the amounts of certain chemicals, such as RNA (核糖核酸), radically in crease with learning, as do the amounts of certain neurotransmitters (神经传递素 )—chemicals released by brain cells that help conduct nerve impulses from one brain cell to another. Memory, then, is also chemical in nature, al though exactly in what way remains a mystery. Almost all memory researchers now agree that our brains record—and on some level remember—everything that ever happens to us. Many people who've narrowly escaped sudden death, such as soldiers and mountain climbers, have reported that in the few seconds that seemed left to them a stream of long-lost memories flashed before them. The first experimental confirmation that the brain does record every experience in this minute way came some years ago from Dr. Wilder Penfield of the Montreal Neurological Institute. He hoped to cure epileptics (癫痫病人) by stimulating a part of their brains called the temporal cortex (脑的颞皮层) with a mild electric current. Because the brain is immune to pain, Penfield was able to operate with his patients fully awake. To his astonishment, simply by touching the brains of some patients with the tip of his wire-thin electrode (电极) he was able to evoke astonishingly precise and vivid memories. 'I see a guy coming through the fence at the baseball game,' exclaimed one patient, whenever Penfield touched the upper part of his left temporal lobe (脑叶). 'It's the middle of the game, and I'm back there watching him)' Another woman reported being back at a con cert she had once attended and could even hum along with the orchestra whenever her brain was stimulated. Investigators using hypnosis (催眠术) have been as astonished as Penfield at the amazing capacity of our memories. Once in a trance (昏睡), good hypnotic subjects can report detailed recollections of events that took place days, months, even decades ago—which, when checked against old records and diaries, turn out to be accurate. 'Everything, absolutely everything, is remembered,' says one hypnotist. Even senile patients, who can hardly remember recent events at all, retain the ability to remember new experiences, but only ver