TUESDAY, Oct. 28, 2003 (HealthDayNews) -- When you remember an emotional event, your memory of it may be very accurate, but you are likely to forget the events that preceded it, researchers report.
"If an emotional event happens, you remember it better. However, this comes at a cost: The cost is that the things that precede the emotional event tend to be remembered much worse," says lead researcher Ray Dolan, a professor of neurology at University College London.
Dolan and his colleagues asked 10 volunteers to study a list of nouns. Each list contained emotionally aversive words such as "murder" or "scream." The subjects were then asked to recall the words on the list.
The researchers found the volunteers remembered the emotionally charged words much better than the other words. In addition, they had significant trouble remembering the words that came immediately before the emotionally charged words.
They also found that among women the effect of emotion-induced amnesia was twice as large as compared with men, according to their report in this week's issue of the Proceedings of the National Academy of Sciences.
To determine the neurological basis for this finding, Dolan's team repeated the test with 24 subjects who were given either propranolol, a beta blocker drug that can also reduce anxiety, or a placebo.
They also tried the test on an individual who had damage to the part of the brain called the amygdala. The amygdala is involved in producing and responding to nonverbal signs of avoidance, defensiveness and fear.
The team found that "by blocking the emotional arousal associated with these events you can reverse the process," Dolan says.
Among the subjects who received the drug and the subject with the damaged amygdala, there was no improvement in the memory of the emotionally charged words and no emotional amnesia for the words that came directly before. This indicates that both adrenergic hormones and the amygdala influence emotion-induced amnesia.
Dolan says the implication of these findings is that witnesses to emotionally charged events such as accidents or crimes may have totally incorrect memories of what led up to the event. Therefore, their accounts may be poor or unreliable.
Furthering their research, Dolan's team continues to study how mechanisms of memory can be disrupted. Their goal, Dolan says, is to determine how better memories are created.
"The findings of this study are important because they suggest that the brain mechanisms that we think are important for enhanced memory associated with emotional events are also involved in memory impairment for emotional events," says Dr. Larry Cahill, an assistant professor of neurobiology at the University of California at Irvine and author of an accompanying commentary.
"Right now it is too soon to tell if these findings will have any clinical implications, but they made lead to a better understanding of how emotion affects the mechanisms of memory," he says.
More information
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