FRIDAY, Feb. 26 (HealthDay News) -- It's not a particular brain region that makes someone smart or not smart.

Nor is it the strength and speed of the connections throughout the brain or such features as total brain volume.

Instead, new research shows, it's the connections between very specific areas of the brain that determine intelligence and often, by extension, how well someone does in life.

"General intelligence actually relies on a specific network inside the brain, and this is the connections between the gray matter, or cell bodies, and the white matter, or connecting fibers between neurons," said Jan Glascher, lead author of a paper appearing in this week's issue of the Proceedings of the National Academy of Sciences. "General intelligence relies on the connection between the frontal and the parietal [situated behind the frontal] parts of the brain."

The results weren't entirely unexpected, said Keith Young, vice chairman of research in psychiatry and behavioral science at Texas A&M Health Science Center College of Medicine in Temple, but "it is confirmation of the idea that good communication between various parts of brain are very important for this generalized intelligence."

General intelligence is an abstract notion developed in 1904 that has always been somewhat controversial.

"People noticed a long time ago that, in general, people who are good test-takers did well in a lot of different subjects," explained Young. "If you're good in mathematics, you're also usually good in English. Researchers came up with this idea that this represented a kind of overall intelligence."

"General intelligence is this notion that smart people tend to be smart across all different kinds of domains," added Glascher, who is a postdoctoral fellow in the department of humanities and social sciences at the California Institute of Technology in Pasadena.

Hoping to learn more, the authors located 241 patients who had some sort of brain lesion. They then diagrammed the location of their lesions and had them take IQ tests.

"We took patients who had damaged parts of their brain, tested them on intelligence to see where they were good and where they were bad, then we correlated those scores across all the patients with the location of the brain lesions," Glascher explained. "That way, you can highlight the areas that are associated with reduced performance on these tests which, by the reverse inference, means these areas are really important for general intelligence."

"These studies infer results based on the absence of brain tissue," added Paul Sanberg, distinguished professor of neurosurgery and director of the University of South Florida Center for Aging and Brain Repair in Tampa. "It allows them to systemize and pinpoint areas important to intelligence."

Young said the findings echo what's come before. "The map they came up with was what we expected and involves areas of the cortex we thought would be involved -- the parietal and frontal cortex. They're important for language and mathematics," he said.

In an earlier study, the same team of investigators found that this brain network was also important for working memory, "the ability to hold a certain number of items [in your mind]," Glascher said. "In the past, people have associated general intelligence very strongly with enhanced working memory capacity so there's a close theoretical connection with that."

More information

Learn more about the workings of the brain at Harvard University's Whole Brain Atlas  .

THURSDAY, Feb. 25 (HealthDay News) -- U.S. hospitals throw away surgical gowns, towels and ultrasonic cutting tools after a single use, but recycling those supplies could save hundreds of millions of dollars annually and protect the environment, researchers say.

The authors of a study in the March issue of the journal Academic Medicine argue that it can be safe to reuse equipment as long as proper sterilization, recalibration and testing procedures are followed.

"No one really thinks of good hospitals as massive waste producers, but they are," Dr. Martin Makary, surgeon and associate professor of public health at the Johns Hopkins University School of Medicine and lead study author, said in a statement. "There are many things hospitals can do to decrease waste and save money that they are not currently doing."

Some items are discarded even when they haven't been used because their packages were opened and they may have been contaminated, the authors noted.

The researchers reported that the U.S. Government Accountability Office recently found that certain recycled devices aren't dangerous.

"These devices are safe, but it's a public relations challenge," Makary said. "Some people don't like the idea that they're being treated with equipment that has been used before. But these reprocessed devices are as good as new since the testing standards for reuse are impeccable and there have been no patient safety problems in our analysis."

More information

The U.S. Environmental Protection Agency has details about disposal of medical waste.

WEDNESDAY, Feb. 24 (HealthDay News) -- People who have trouble recognizing faces may be relieved to know that the problem may not be related to poor memory or eyesight, but could be in their genes, new research suggests.

The study included 164 identical twins (who share all of their genes) and 125 non-identical, same-sex twins (who share 50 percent of their genes). All of the study participants took part in a face memory test. Compared to non-identical twins, identical twins were twice as similar to each other in their ability to recognize faces, the researchers found.

The findings, published in this week's issue of the Proceedings of the National Academy of Sciences, show that shared genes, not shared family environment, are responsible for the strong similarity in identical twins.

"Face recognition is a skill that we depend on daily and considerable variability exists in the ability to recognize faces," study co-author Dr. Brad Duchaine, of the Institute of Cognitive Neuroscience at University College London in the U.K., said in a university news release. "Our results show that genetic differences are responsible for the great majority of the difference in face recognition ability between people," he explained.

"We are excited about this finding because the brain mechanisms carrying out face recognition are fairly well understood, meaning that the high heritability of face recognition could provide a good opportunity to connect genes to brain mechanism and then to behavior," he added.

Duchaine and colleagues said they also found that the genetic-related processes involved in face recognition are linked to a specific mechanism in the brain that's unrelated to other processes such as the ability to recognize words or abstract art.

More information

The U.S. National Institute of Neurological Disorders and Stroke has more about the condition that prevents people from recognizing faces, called prosopagnosia.

TUESDAY, Feb. 23 (HealthDay News) -- Although physicians still work long hours, the past decade has seen a sharp decline in the average number of hours they work each week, a new study finds.

From 1976 through 1996, the average work week of doctors remained steady, but between 1996 and 2008, the average number of hours physicians spent at work dropped nearly four hours a week -- from 54.9 to 51 hours a week.

"After being stable at around 55 hours for decades, physicians' hours have declined 7 percent in the past decade to around 51 hours a week," said the study's lead author, Douglas Staiger, professor of economics at Dartmouth College in Hanover, N.H. "This is an unprecedented decline that we haven't seen before in physicians, and you don't see it for other professions, like lawyers."

Results of the study are published in the Feb. 24 issue of the Journal of the American Medical Association.

For the study, Staiger and his colleagues reviewed data on trends in physicians' work hours from the U.S. Census Bureau from 1976 through 2008. The survey included 116,733 doctors from across the country.

Initially, the researchers suspected that rules instituted in 2003 limiting the amount of time that physician residents can work in hospitals might have been behind the drop in physician hours. Although residents did have a larger decline in hours -- 9.8 percent on average -- the drop in hours worked affected all physicians, with non-resident physicians experiencing a 5.7 percent reduction in their work week.

"The decline in hours was very broad-based. It's happening among all types of physicians -- young and old, working at a hospital or not," said Staiger.

The biggest drops in hours worked were for non-resident physicians under 45 years old and those working outside of a hospital.

The study also found that the average physician's fees dropped by 25 percent between 1995 and 2006. In areas with the lowest physician fees, the average number of hours worked was just 49 per week in 2001, according to the study.

"If you get paid less, you have less incentive to work harder," said Dr. Michael Reis, the interim chairman of the Family Medicine Department at Scott & White Healthcare in Temple, Texas. "One of the problems is that physicians put off years of earning through college, medical school and residency, and are often way behind the eight ball when they're done training. That may drive some to pick specialties that pay more for fewer hours."

Staiger said that the data wasn't broken down by specialty, so the researchers weren't able to discern if more people were entering specialties that require fewer work hours.

But, he said, the researchers do believe that financial pressures probably have something to do with the decline in work hours.

"As fees have come down, for physicians to make the same money, they have to see more patients, and that makes it less satisfying for everybody. Patients feel rushed and physicians can't spend the time they want to with patients," said Reis.

Staiger agreed that doctors probably have to spend less time with each patient. "Physicians may be fitting more into a shorter period of time," he said.

And, with an aging population that's growing, physicians may be forced to do more in less time. Although the United States has more doctors now than ever before, the reduction in work hours is equivalent to losing about 35,000 full-time doctors, according to Staiger.

"We already know there's going to be a shortage of physicians in the future, especially primary care doctors, and this is only going to multiply the problem," said Reis.

More information

For advice on choosing your doctor, visit the U.S. National Institute on Aging.