Memory plays a critical role in intelligence. Memory also serves to define our identity -- who we think we are.

A new class of drug may increase alertness without any of the jitteriness of over-stimulation, suggest the results of a small clinical trial released this week.

A compound dubbed CX717, a member of the new class called ampakines, significantly improved performance on tests of memory, attention, alertness, reaction time and problem solving in healthy men deprived of sleep.

The study was carried out by Julia Boyle at the Sleep Research Centre at the University of Surrey, UK, and her colleagues on behalf of Cortex Pharmaceuticals Inc., based in Irvine, California, US.

It would be hard to imagine improving on the intelligence of computer engineer Bjoern Stenger, a doctoral candidate at Cambridge University. Yet for several hours, a pill seemed to make him even brainier.

Participating in a research project, Stenger downed a green gelatin cap containing a drug called modafinil. Within an hour, his attention sharpened. So did his memory. He aced a series of mental-agility tests. If his brainpower would normally rate a 10, the drug raised it to 15, he said.

"I was quite focused," said Stenger. "It was also kind of fun."

The age of smart drugs is dawning. Modafinil is just one in an array of brain-boosting medications — some already on pharmacy shelves and others in development — that promise an era of sharper thinking through chemistry.

These drugs may change the way we think. And by doing so, they may change who we are.

Long-haul truckers and Air Force pilots have long popped amphetamines to ward off drowsiness. Generations of college students have swallowed over-the-counter caffeine tablets to get through all-nighters. But such stimulants provide only a temporary edge, and their effect is broad and blunt — they boost the brain by juicing the entire nervous system.

The new mind-enhancing drugs, in contrast, hold the potential for more powerful, more targeted and more lasting improvements in mental acuity. Some of the most promising have reached the stage of testing in human subjects and could become available in the next decade, brain scientists say.

A few months ago, as I trudged down the stairs of my office building, deep in my thoughts, I noticed a dark-haired woman waving to me from the window of her car. She looked vaguely familiar, but I couldn't place her. Like quite a few others, she had slipped out of my mental Rolodex. In my brain, the synaptic traces that connected us had frayed. Yet again, I had misplaced an entire human being.

''So wonderful to see you,'' she said, inquiring by name after every member of my family, including the two dogs. Apparently she was not a casual acquaintance. Fending off panic, I proceeded through a mental list: Work? School? Synagogue? I couldn't visualize her in these places. I was about to cut and run with a quick ''nice to see you, too'' when the rear window slid down, revealing a toothy grin.

''We've been to the orthodontist,'' she said. The minute I saw Sam's freckled face, the mystery was solved. Our sons were best pals in nursery school and kindergarten. I had sat in her kitchen, discussing birthday parties. I remembered her backyard dotted with Little Tikes plastic play furniture. I knew what she did for work, and the name of her Portuguese nanny.

''Lisa,'' I said, as if her identity had never eluded me, ''it's terrific to see you.''

Why, as I edge toward the end of my 40's, has so much of what I know become impossible to access on demand? Where are the thoughts that spring forth in the shower but evanesce before they can be recorded, the mental lists that shed items on the way to the supermarket? The names of books and movies, actors and authors, le mot juste, the memory of social plans agreed upon in some calendarless situation -- what have become of these?

If only that very first bite of asparagus had inspired delight, and the first taste of jelly doughnut caused a stomachache. If children's happiest food memories were baked and not fried, leafy green rather than beefy, think of the difference in what people might eat.

Now, think of what it might mean to change those memories - as an adult. Psychologists in California and Washington were studying false memories when they stumbled on a surprisingly easy target for manipulation: foods. In a study accepted for publication in the journal Social Cognition, the researchers describe how they fooled college students into thinking that as children they had become sick when eating certain foods.

The students answered questions about their early eating memories. A week later, they were presented with a bogus food history profile that embedded a single falsehood - that they had gotten sick when eating pickles or hard-boiled eggs - among real memories.

If you recall this sentence a few seconds from now, you can thank a simple network of neurons for the experience. That is the conclusions of researchers who have built a computer model that can reproduce an important aspect of short-term memory.

The key, they say, is that the neurons form a "small world" network. Small-world networks are surprisingly common. Human social networks, for example, famously connect any two people on Earth - or any actor to Kevin Bacon - in six steps or less.

Properties like this have made them the focus of much research. It turns out that regardless of the size of these networks, any two points within them are always linked by only a small number of steps.

Scientists have discovered the region of the brain responsible for the old adage, "out of sight, out of mind."

The amount of information we can remember from a visual scene is extremely limited and the source of that limit may lie in the posterior parietal cortex, a region of the brain involved in visual short-term memory, Vanderbilt psychologist René Marois and graduate student J. Jay Todd have found. Their results were published in the April 15 edition of Nature.

"Visual short-term memory is a key component of many perceptual and cognitive functions and is supported by a broad neural network, but it has a very limited storage capacity," Marois said. "Though we have the impression we are taking in a great deal of information from a visual scene, we are actually very poor at describing its contents in detail once it is gone from our sight."

The new movie “Eternal Sunshine” shows us a fictional way to erase the past, but what keeps those thoughts around in the first place? As the ScienCentral news video reports, brain researchers are beginning to unwind a new twist on maintaining memory.

Memory with a Twist

“Memory is the fundamental glue that ties our mental life together,” says neuroscientist Eric Kandel. “The way we connect our life—our early years, our middle years, our married years, our children and grandchildren—is by being able to sit back and recall, almost in a form of time travel, what our life has been like.”

A professor at Columbia University and a senior investigator for the Howard Hughes Medical Institute, Kandel has studied how memory forms in the brain for almost 50 years. He and his post-doc student Kausik Si reported in the journal Cell, that a protein called cytoplasmic polyadenylation element binding protein, or CPEB, is a key brain chemical that enables the long-term storage of memories by preserving new nerve connections that form during learning. They discovered this mechanism by studying the brain chemistry of sea slugs.

The use of photographs by psychotherapists as memory cues for the "recovery" of patients' possible childhood sexual abuse has been called into question by a Canadian study. It found that a "staggering" two-out-of-three participants accepted a concocted false grade-school event as having really happened to them when suggestions regarding the event were supplemented with a class photo.

A 29-year-old paralegal was lying in the middle of Congress Street in downtown Boston after being run over by a bicycle messenger, and her first thought was whether her skirt was hiking up. ''Oh, why did I wear a skirt today?'' she asked herself. ''Are these people all looking at my underpants?''

Her second thought was whether she would be hit by one of the cars speeding down Congress -- she wasn't aware that other pedestrians had gathered around, some of them directing traffic away from her. And her third thought was of a different trauma, eight years earlier, when driving home one night, she was sitting at a red light and found herself confronted by an armed drug addict, who forced his way into her car, made her drive to an abandoned building and tried to rape her.

''I had a feeling that this one trauma, even though it was a smaller thing, would touch off all sorts of memories about that time I was carjacked,'' said the woman, whose name is Kathleen. She worried because getting over that carjacking was something that had taken Kathleen a long time. ''For eight months at least,'' she said, ''every night before I went to bed, I'd think about it. I wouldn't be able to sleep, so I'd get up, make myself a cup of decaf tea, watch something silly on TV to get myself out of that mood. And every morning I'd wake up feeling like I had a gun against my head.''

Would Kathleen have been better off if she had been able to wipe out the memory of the attack rather than spending months seeing a psychologist and avoiding the intersection where the carjacking occurred? The answer seems straightforward: if you can ease the agony that people like Kathleen suffer by dimming the memory of their gruesome experiences, why wouldn't you? But some bioethicists would argue that Kathleen should hold on to her nightmarish memory and work through it, using common methods like psychotherapy, cognitive behavior therapy or antidepressants. Having survived the horror is part of what makes Kathleen who she is, they say, and blunting its memory would diminish her and keep her from learning from the experience, not to mention impair her ability to testify against her assailant should the chance arise.

Researchers at the University of Pennsylvania School of Medicine have found that the neurotransmitter norepinephrine is essential in retrieving certain types of memories. This represents the first description of a molecule implicated in recalling memories as opposed to laying down new memories. Teasing apart different components of this pathway may help physicians better understand post-traumatic stress disorder (PTSD) and depression -- both of which involve alterations in memory retrieval, says lead author Steven A. Thomas, MD, PhD, Assistant Professor of Pharmacology. The findings of this research appear in the April 2 issue of Cell.

While it might not seem so the next time you go searching for your car keys, scientists at the University of Pennsylvania have shown that memories are not as fluid as current research suggests. Their findings challenge the prevailing notion on how memories are stored and remembered – or that a recalled memory could be altered or lost as it is "re-remembered."

A drug nicknamed "Viagra of the mind" that enables people to improve their memory is to be tested on humans and could be on sale within five years.

Tim Tully, a professor of genetics at Cold Spring Harbour Laboratory in New York, who developed the drug, said: "If it proves safe and effective it could ultimately be used by people who want to learn a language or a musical instrument or even in schools." The most important market, however, could be healthy people in their 40s and 50s whose memory was deteriorating.

The drug, code-named HT-0712, helps to retain information in the short-term memory. It works by activating a gene contained in every human cell. Once activated, it allows brain cells to make the connections vital for memory formation.