Each memory tweaks some tiny subset of the neurons in the brain (the human brain has 100 billion neurons in all), changing the way they communicate. Scientists have long known that recording a memory requires adjusting the connections between neurons. Even the most cherished ideas in a given field are open to question. вЂњOne of the things that really seduced me about science is that itвЂ™s a system you can use to test your own ideas about how things work,вЂќ Nader says. He attended college and graduate school at the University of Toronto, and in 1996 joined the New York University lab of Joseph LeDoux, a distinguished neuroscientist who studies how emotions influence memory. Many relatives also made the trip, so many that NaderвЂ™s girlfriend teases him about the вЂњsoundtrack of a thousand kissesвЂќ at large family gatherings as people bestow customary greetings. His Coptic Christian family faced persecution at the hands of Arab nationalists and fled to Canada in 1970, when he was 4 years old. It might even be possible to put the phenomenon to good use to reduce the suffering of people with post-traumatic stress disorder, who are plagued by recurring memories of events they wish they could put behind them. But if he is right, it may not be an entirely bad thing. Memories surrounding a major event like September 11 might be especially susceptible, he says, because we tend to replay them over and over in our minds and in conversation with others-with each repetition having the potential to alter them.ДЇor those of us who cherish our memories and like to think they are an accurate record of our history, the idea that memory is fundamentally malleable is more than a little disturbing.вЂ€Not all researchers believe Nader has proved that the process of remembering itself can alter memories. Nader thinks itвЂ™s likely that some types of memory, such as a flashbulb memory, are more susceptible to change than others. In fact, he says, it may be impossible for humans or any other animal to bring a memory to mind without altering it in some way. Much of his research is on rats, but he says the same basic principles apply to human memory as well. In short, Nader believes that the very act of remembering can change our memories. His ideas are unconventional within neuroscience, and they have caused researchers to reconsider some of their most basic assumptions about how memory works. Nader believes he may have an explanation for such quirks of memory.

Apparently he wasnвЂ™t alone: a 2003 study of 569 college students found that 73 percent shared this misperception. But he was surprised to learn that such footage aired for the first time the following day. He recalled seeing television footage on September 11 of the first plane hitting the north tower of the World Trade Center. Nader, now a neuroscientist at McGill University in Montreal, says his memory of the World Trade Center attack has played a few tricks on him. (Unfortunately, staggeringly terrible news seems to come out of the blue more often than staggeringly good news.) But as clear and detailed as these memories feel, psychologists find they are surprisingly inaccurate. Kennedy, say, or the explosion of the space shuttle Challenger. Most people have so-called flashbulb memories of where they were and what they were doing when something momentous happened: the assassination of President John F. But as an expert on memory, and, in particular, on the malleability of memory, he knows better than to fully trust his recollections. Like millions of people, Nader has vivid and emotional memories of the September 11, 2001, attacks and their aftermath. вЂњIt was like walking upstream in a river of sorrow,вЂќ he says. In the following days, Nader recalls, he passed through subway stations where walls were covered with notes and photographs left by people searching desperately for missing loved ones. He stood there, stunned, as they burned and fell, thinking to himself, вЂњNo way, man. Nader ran to the roof of his apartment building, where he had a view of the towers less than two miles away. He flipped the radio on while getting ready to go to work and heard the banter of the morning disc jockeys turn panicky as they related the events unfolding in Lower Manhattan. He lights a cigarette and waves his hands in the air to sketch the scene.ДЄt the time of the attack, Nader was a postdoctoral researcher at New York University. Sitting at a sidewalk cafГ© in Montreal on a sunny morning, Karim Nader recalls the day eight years earlier when two planes slammed into the twin towers of the World Trade Center.

Creating memories