I have some doubts with relation to the difference between the number of neurons and level of neurotransmitters in men and women. Does it imply in some deficiency? Does it contribute to anything? Fabiana Leornardo, student, Sao Paulo

Fabiana Leornardo, student, Sao Paulo

According to medical researchers of the Montreal Neurological Institute (Canada) there exists a significant difference in the rate of serotonin synthesis in the brain of men and women and this difference may explain the fact that women are more prone to depressive disorders than men. Researchers have reported that severely depressed people have a lower than normal level of serotonin, as demonstrated by PET scans of their brains. Even though normal people of both sexes have approximately the same level of serotonin, its synthesis in the brain of men is 52% faster than in women. Researchers also compared the response to serotonin in the brain to emotional stress in both, men and women. The impact of stress was four times higher in women than in men.

Dr. Silvia H. Cardoso, Psychobiologist, Campinas, Brazil

Regarding the difference in the total number of neurons in the brain of men and women (men have a few more billion neurons than women) which has recently been announced in the newspapers, it seems that it has no particular meaning. Men have a larger muscular mass than women, and this, per se, would explain the difference. The primitive man, the Neanderthal, had a larger brain than Homo sapiens sapiens (Cro- Magnon), but its intelligence was actually lower. Scientists believe that the brain was larger because of its larger body size, too.

Dr. Renato Sabbatini, Director, Center for Biomedical Informatics, Campinas, Brazil