Researchers study male attention span

Men may have a new excuse the next time someone complains about their short attention span. School of Medicine Psychiatry Professor Ruben Gur has discovered that men's brains shrink in volume after age 40. Ruben and his wife Raquel, also a Psychiatry professor in the Medical School, have done extensive research on the brain's response to behavioral challenges, specifically focusing on sex differences in the aging process. Gur said the brain's main activity depends on blood flow and metabolic activity. Women have a faster blood flow rate than men, but the metabolic rates of the two sexes are close to same number. But he added that there are noticeable metabolic differences in the temporal and limbic areas of the brain. "These areas make up the emotional brain," he said. "The differences that occur in the limbic areas -- the old and the new -- seem to relate directly to sex differences." According to Gur, the old limbic area is shared with "lower organisms." He explained that it regulates through actions -- "in other words, an angry reptile will strike." "Men have higher rates of glucose breakdown in this area," he said. The new limbic area regulates through symbolic means and vocalization. Women have a higher glucose breakdown rate in this area. These metabolic differences lead to differences in performance of behavioral tasks, according to Gur. In areas such as abstraction, mental reflexivity and verbal memory, women excelled. However, men scored higher on spatial tests such as line orientation and block design. Gur explained that as men age, they show a definite deterioration in attention span, while women show little to no deterioration. When looking for an explanation for this deterioration, Gur turned to the actual volume of the brain. "The average human brain weighs about 1,200 milliliters," he explained. "When you look across the age range, male brains show a definite reduction in volume and an increase in [brain fluid]." He added that men's bodies contain three times more fluid than women. Gur said the most dramatic difference occurs in the frontal lobe, the section he calls "the big inhibitor." "It's the section of the brain that tells you when you want to do something," he said. Gur said this inhibition is important because it is necessary for attention span. "Frontal lobe damage leads to attention difficulties," he said. Gur explained that there are a number of possible reasons for this dramatic deterioration of the brain's volume. But he said the main reason deals with the decrease of blood flow as the brain ages. The rate of reduction is equal in men and women, but women have a greater reduction in glucose metabolism. According to Gur, this means that at some point during aging, women manage to adjust the metabolic function while men continue to burn glucose at the same rate they did before blood flow slowing. As the blood in the brain flows slower, the toxic waste produced during metabolic action becomes stockpiled, in turn killing brain cells and reducing volume. Gur added that studies show that when women rest, they tend to use different parts of their brains than those they use regularly during the day. Men tend to use the same parts of their brains during the day and while relaxing. "This could also be a factor in the deterioration function," he said. Gur and his wife came to the University in 1974, gaining tenure in the Medical School in the early eighties. He said the main interest of the husband-wife team is the study of brain-behavior relationships through the exploitation of functional imaging. "Working as a husband-wife team, we noticed a number of mental differences that seemed biological," Gur added. "As soon as we got windows into the brain, we started looking for sex-related differences in brain function and physiology."