BY LISA TREI
Male and female brains are wired differently when it comes to dealing with emotion, according to new research published in the Proceedings of the National Academy of Sciences.
The findings may help explain why women remember emotional experiences more keenly than men, said John Gabrieli, an associate professor of psychology and a study co-author.
In the research study, titled "Sex differences in the neural basis of emotional memories," 12 men and 12 women were asked to look at 96 pictures and rate them on a scale from neutral to intensely negative. The images ranged from a neutral image of a book to a moderately negative picture of a graveyard to an intensely negative image of a dead person or a snake coiled to strike. As the volunteers viewed the pictures, activity in their brains was recorded by functional Magnetic Resonance Imaging (fMRI). The technique identifies which parts of the brain are active by measuring blood flow.
In a surprise follow-up test three weeks later, women outperformed men by 15 to 20 percent when it came to remembering accurately the most intensely negative photographs. Two kinds of brain activation were examined -- activation that increased for emotionally intense feelings and activation that predicted which pictures would be remembered.
As expected, Gabrieli said, both sexes reacted to negative images more intensely than to neutral ones. "Both groups turned on lots of parts of the brain for emotional feelings and for building future memories," he said. "But the big difference was that in women, they tended to be in the same place in the brain. If part of the brain turned on because something was emotionally intense, it also seemed to predict whether [the subject] would remember something later on. In men, there was very little overlap between the two activations.
"That would suggest a potential physical mechanism in the brain where women incorporate emotional experience into their memory. Because different parts of the brain turned on in men, it seems there is more separation in their brains between emotional processes and memory formation processes." In other words, he said, memory in men included less emotional information.
According to Gabrieli, researchers want to use the findings to check whether such neural mechanisms might be associated with people suffering from depression. According to statistics, twice as many women suffer from the illness as men. A risk factor for depression is rumination, or dwelling on a memory, and the study shows a possible biological basis for rumination. Gabrieli also said he wants to test children to investigate at what ages differences arise in boys and girls experiencing memory and emotion.
The lead author of the study is Turhan Canli, a former Stanford researcher and now an assistant professor of psychology at State University of New York-Stony Brook. Additional authors include Stanford's John E. Desmond, an assistant professor of radiology, and Zuo Zhao, a former staff member in the Department of Psychology.
Stanford Report, July 24, 2002