Researchers have long known that women remember emotional events far better than men do, but exactly why this should be so has proved difficult to pin down. Some scientists posit that women experience life events more intensely, leading to better memory encoding, while others speculate that the neural basis of memory formation differs between the sexes. Research published online this week by the Proceedings of the National Academy of Sciences offers support to the latter model. According to the report, women use more and different brain regions than men do when experiencing or remembering intense emotional experiences, resulting in more vivid recollections.

Turhan Canli of Stanford University and colleagues connected 12 men and 12 women to a functional magnetic resonance imager (fMRI) to examine their brain activity on a moment-to-moment basis. The team then asked the participants to rate the emotional intensity of pictures ranging from neutral (such as a fire hydrant) to very negative (such as mutilated bodies). The first hypothesis--that women experience life more intensely than men do-- predicts identical brain activation patterns in the two sexes. If, on the other hand, men and women actually use different neural networks to encode memories, their resulting brain patterns should be quite different. The researchers found support for the latter, observing that the female brain activation pattern is distinct from the male pattern. Women also rated more pictures as highly emotional.

Three weeks later, the team surprised the subjects with a new test. Asked to note whether or not they remembered certain previously seen images, women recalled far more of the highly emotional pictures than did men. Furthermore, they again displayed a brain activation pattern with a greater number of stimulated areas, even when viewing pictures that both sexes had rated as equally disturbing. Both groups remembered neutral images similarly, however. "The data presented here demonstrate that men and women differ in the neural networks engaged during emotional experience and memory encoding," the authors write. "Greater overlap in brain regions sensitive to current emotion and contributing to subsequent memory," they add, "may be a neural mechanism for emotions to enhance memory more powerfully in women than in men."