FRIDAY, June 22 (HealthDay News) -- Love and sexual desire activate different but related areas of the brain, according to a new study.

Researchers analyzed data from 20 studies that monitored brain activity in people while engaged in activities such as viewing erotic pictures or photographs of their romantic partners.

This meta-analysis led to a map of love and desire in the brain, which shows that two structures called the insula and the striatum are involved in the progression from sexual desire to love.

"No one has ever put these two together to see the patterns of activation," study co-author Jim Pfaus, professor of psychology at Concordia University in Montreal, said in a university news release. "We didn't know what to expect -- the two could have ended up being completely separate. It turns out that love and desire activate specific but related areas in the brain."

The researchers found that love and sexual desire activate different areas of the striatum. The area activated by sexual desire is the same one that is activated by pleasurable activities such as sex or food. The area activated by love is where things associated with reward or pleasure are given a value.

The area activated by love also is associated with drug addiction, the researchers said.

"Love is actually a habit that is formed from sexual desire as desire is rewarded," Pfaus explained. "It works the same way in the brain as when people become addicted to drugs."

He also noted that love activates pathways in the brain involved in monogamy and pair bonding, and added that some areas in the brain are less active when people feel love than when they feel desire.

"While sexual desire has a very specific goal, love is more abstract and complex," Pfaus said. "It's less dependent on the physical presence of someone else."

The study conclusions should be considered preliminary until published in a peer-reviewed medical journal.

More information

Your Amazing Brain has more about the science of love  .

FRIDAY, June 22 (HealthDay News) -- Young men receiving drug treatment for HIV infection are at increased risk for low bone mass, a new study suggests.

The findings indicate that these patients should exercise, take vitamin D and be closely monitored in order to reduce their future risk of bone fractures, according to the study, released online in advance of print publication in the journal Clinical Infectious Diseases.

The study included about 250 male participants, aged 14 to 25, who underwent whole-body scans to measure their bone density. Some of the men were infected with HIV, the virus that causes AIDS.

The participants with HIV had been diagnosed with the infection an average of two years earlier. The HIV-infected males had an average 5 percent to 8 percent lower bone density in the hip and 2 percent to 4 percent lower bone density in the spine than those without HIV.

Although the study uncovered an association between treatment for HIV infection and lower bone density in the study participants, it did not prove a cause-and-effect relationship.

The study, funded by the U.S. National Institute of Child Health and Human Development (NICHD), did not look at the causes of bone loss and cannot rule out the possibility that low bone mass was present before HIV infection.

The investigators noted that all the participants had several risk factors for bone loss, including tobacco and alcohol use and low intake of calcium and vitamin D, which is needed to absorb calcium.

"The young [HIV-positive] men in the study had been taking anti-HIV medications for a comparatively short time, yet they still had lower bone-mineral density than other men their age," study co-author Dr. Bill Kapogiannis, of the pediatric, adolescent and maternal AIDS branch of the NICHD, said in an institute news release.

"These findings suggest a short-term impact of HIV therapy on bone at ages when people are still growing and building bone mass," Kapogiannis added. "This raises concerns about the risk of fracture as they age."

Previous research in adults has indicated that there may be an association between the use of certain anti-HIV medications and an increased risk for bone fractures and bone loss, the study authors noted in the news release.

Doctors who care for young men with HIV should monitor these patients regularly for signs of bone thinning, which could predict a risk for fractures, the researchers said. Young men newly diagnosed with HIV also should exercise, quit smoking, limit alcohol consumption and get the proper amount of calcium and vitamin D.

More information

The New Mexico AIDS Education and Training Center outlines the side effects of anti-HIV drugs  .

THURSDAY, June 14 (HealthDay News) -- Pregnant women's immune systems do not attack their developing babies because embryo implantation in the uterus triggers a process that affects the ability of immune cells to reject foreign bodies, new research shows.

The investigators from the NYU Langone Medical Center found a key immune system pathway is turned off following implantation, so immune cells are not called in to harm a fetus. Without this process, the researchers noted, preterm labor, miscarriage or a dangerous medical condition called preeclampsia could result.

The study was published recently in the journal Science.

According to lead investigator Dr. Adrian Erlebacher, an associate professor of pathology at the medical center, the study "addresses a fundamental question . . . namely, how do the fetus and placenta, which express antigens that are disparate from the mother, avoid being rejected by the maternal immune system during pregnancy?" The answer, he explained in a center news release, "was completely unexpected at every level."

Normally, the immune system produces chemokines, which trigger immune cells to attack foreign tissues, such as occurs in the typical tissue rejection response that occurs following an organ transplant.

During pregnancy, however, women's immune cells come into contact with the foreign antigens of their developing fetus and placenta, but this rejection response does not take place. To investigate why this happens, the researchers examined the decidua, the structure that contains the fetus and placenta.

The findings showed that when a woman becomes pregnant, the genes responsible for calling immune cells are turned off inside the decidua, protecting the developing fetus. The study authors explained that an "epigenetic change," or a non-hereditary change, takes place in the DNA of the cells of the decidua that deactivates the chemokine genes. When this happens, the typical immune system response is deactivated at the site of embryo implantation.

"It turns out that the cells that typically secrete the chemoattractants to bring the T-cells [the cells that accumulate and attack tissue] to sites of inflammation are inhibited from doing so in the context of the pregnant uterus," Erlebacher said. "The decidua appears instead as a zone of relative immunological inactivity."

In addition to pregnancy, the study authors said their findings could also have implications for autoimmune diseases, organ transplantation and cancer.

"This is a very exciting finding for us because it gives a satisfying explanation for why the fetus isn't rejected during pregnancy, which is a fundamental question for the medical community with clear implications for human pregnancy," Erlebacher said. And, he added, it could lead to new methods for treating many other conditions and diseases.

More information

The U.S. National Library of Medicine has more about the immune system.

WEDNESDAY, May 16 (HealthDay News) -- Some people actually may have "gaydar," a widely used slang term for the ability to assess quickly another person's sexual orientation, a new study suggests.

Researchers asked 129 college students to look at 96 photos of young men and women and to identify them as either gay or straight. The participants were 65 percent accurate in identifying gay and straight women and 57 percent accurate in identifying gay and straight men.

Faces in photos were free of glasses or jewelry, as well as scars, facial hair and non-earlobe piercings.

When the faces were viewed upside down, the participants' accuracy slipped to 61 percent in identifying gay/straight women and 53 percent in identifying gay/straight men.

Still, that accuracy rate is higher than would be expected by chance alone, the researchers said.

The findings suggest that many people subconsciously make gay and straight distinctions, according to study author Joshua Tabak, a psychology graduate student at the University of Washington in Seattle.

"It may be similar to how we don't have to think about whether someone is a man or a woman, or black or white. This information confronts us in everyday life," he said in a university news release.

Tabak said the findings challenge the theory that if people kept their sexual orientation to themselves then discrimination against gays, lesbians and bisexuals would not exist. This type of argument is made by people who oppose anti-discrimination policies for these groups, the release noted.

It's not clear why some people have better "gaydar" than others. Tabak suggested that "people from older generations or different cultures who may not have grown up knowing they were interacting with gay people" may be less accurate in identifying gay or straight people.

The study was published online May 16 in the journal PLoS One.

More information

The American Psychiatric Association has more about sexual orientation  .