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Dec. 4, 2000 -- Did you take your medicine this morning? Or did you only imagine you did? The mysteries of memory, and how they are processed in the brain, extend to more serious questions about disputed memories of childhood abuse or trauma, recalled by patients seeking therapy. Were the events real, or only imagined?

In recent years, the medical community has become increasingly aware of a phenomenon known as "false memory syndrome", where through therapy, people become convinced that they were sexually abused as children. In these cases -- which occur mostly in women -- the memories of abuse, although vivid, are false, induced by suggestion in therapy. This unfortunate, yet uncommon, side effect of therapy can tear families apart, and leave therapists confused and bewildered about what to do.

Now, new laboratory research measuring brain activity during the process of recall has produced results that may help scientists understand better how the brain creates false memories. Specifically, the brain appears to record as real those events or images that have more visual detail, says Kenneth Paller, PhD, associate professor of psychology at the Neuroscience Institute and the department of psychology at Northwestern University in Chicago.

And the degree of visual detail can be measured using a test that monitors the amount of brain activity taking place in the part of the brain believed to be related to visual perception, Paller says.

Attaching electrodes to the back of the head, Paller and colleagues measured brain activity when subjects tried to recall an object which they had been shown an actual picture of, as well as objects they had not been shown a picture of, but had only been asked to visualize in their minds.

In some cases, people falsely remembered being a shown a picture of the object, when they really had not. In those cases, there was increased activity. And there was even greater activity measured during recall when a picture of the object really had been shown to them, Paller says.

What it means is that the more visual detail a memory has, the more likely it is to be remembered as real -- even if it isn't real, Paller tells WebMD. "The more visual your memory is, the more likely you are going to ascribe it to an actual event."

But Paller is cautious about extending his laboratory results to controversies surrounding "false memory syndrome". Yet he notes that previous work has shown that false memories can be induced. And his own research provides a glimpse -- through the measurement of brain activity -- of how that might be happening, he says.

"We are learning some of the mechanisms that could lead to false memories in the laboratory, and they may lead to false memories in some situations in real life, but we wouldn't want to infer that that is always the mechanism in false memories," he tells WebMD. "We don't have a way to determine whether someone has a true or false memory."

And he notes that while vividness appears to be the common feature of both false and accurately recalled images and events, the degree of vividness can vary in both cases from person to person. "Some false memories are quite vivid, and some real memories are not so vivid," Paller says.

Kathleen McDermott, PhD, research assistant professor at Washington University in St. Louis, notes that it shows true and false memories can be distinguished at the brain level. "You can sometimes pick up differences ... showing that true memories contain more perceptual details than false memories," she says. McDermott was not involved in the study.

Some would like to try to refine the method in an effort to devise a kind of lie detector test or as a way to determine the truth of allegations of childhood abuse or trauma. But McDermott says those efforts are not likely to bear fruit anytime soon.

In the meantime, the ability to distinguish between true and false memories can only be achieved on average, after testing many memories. The strategy could not be applied to determine whether individual memories are true or false, she says.

Yet McDermott says the study contributes to a growing body of evidence showing that strong conviction about the reality of a memory does not -- at least scientifically -- indicate that the memory is real. "In a courtroom, typically one of the most convincing pieces of evidence is when someone stands up and says they remember someone doing something to them, she tells WebMD. "But that compelling feeling doesn't mean it happened."

And McDermott says her own research has shown that people in certain situations can be reliably predicted to misremember something as real if induced through persistent imagining.

Daniel Schacter, PhD, chair of the department of psychology at Harvard University, says Paller's work provides a first glimpse at what is happening when the brain creates a memory.

"There is something going on in the brain at the time [a memory is created] that allows us to confuse real and imagined events," says Schacter, who reviewed Paller's study for WebMD.

Both Schacter and Paller note that much remains to be learned, including the precise regions of the brain that are involved in creating real and false memories. "We would like to know if we can use other measures of brain activity to pinpoint where things are happening," Paller says. "Perhaps that can tell us more about how false memories are created."

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