Researchers may have located the area in the brain that separates the stamp collectors from the pack rats.

Stories abound of people who filled their homes with piles of old newspapers and suchlike, sometimes to a degree that limits their living space to a few square feet of room. Now, by studying patterns of brain damage in patients with an abnormal penchant for hoarding useless items, scientists may have uncovered the brain region that keeps in check the common human impulse to collect things like stamps, antiques and books.

The findings were published recently in the advanced online edition of the journal Brain.

Rodents and many other animal species show a tendency to hoard, both food and less practical items. Hamsters, for example, have been found to favor stashing glass beads over food. Certain structures deep in the brain, related to survival and present in humans as well, are believed to control hoarding behavior in animals.

But in humans, other, “higher” brain systems must also be involved, according to the authors of the new study.

“People often collect art or stamps or pretty much anything,” Dr. Steven Anderson, the study’s lead author, said in a statement. “Clearly there is some higher structure in humans that modulates the collecting drive and that’s what we think we have tapped into.”

For their study, Anderson and his colleagues at the University of Iowa College of Medicine in Iowa City took MRI brain scans of 86 people who had developed small areas of damage in the front of the brain during childhood or as adults.

While the patients all had normal intelligence and generally normal brain function, 13 were judged, on the basis of a questionnaire given to a close relative, to have a problem with “abnormal collecting.”

These men and women developed a compulsion, after the brain damage occurred, to fill their homes with useless items such as old magazines, junk mail, broken furniture and cardboard boxes. Unlike true collectors, the patients indiscriminately hoarded objects, then paid the items no attention once they got them home - yet stubbornly refused to part with them.

One man, whose wife described him as a “pack rat,” collected tools and bits of scrap metal and wire, much of which he fished from his neighbors’ garbage.

On MRI scans, Anderson and his colleagues found, all 13 of these individuals had small areas of damage in a part of the brain’s frontal lobes known as the mesial prefrontal region. There was no damage, however, to most of the deeper brain structures that are known to control hoarding in rodents and other species.

According to Anderson’s team, the findings suggest that structures in the mesial prefrontal region normally regulate the collecting “drive” that originates in the more primitive, deeper brain structures.

When there is damage to the mesial prefrontal region, as in the study patients, the result appears to be a “disinhibited hoarding drive,” the researchers write.

According to Anderson, the findings could ultimately aid in the understanding of obsessive-compulsive disorder, schizophrenia and other neurological conditions where patients sometimes show an abnormal tendency to hoard.

SOURCE: Brain advance online, Nov. 17, 2004.