FRIDAY, Sept. 23, 2005 (HealthDay News) -- Grumpy, blunt, absent-minded, cranky: It seems like there's no shortage of adjectives to describe the way some elderly people behave.
However, scientists have now found physiological reasons why you can become forgetful or, even worse, rude as you age.
Two new studies using psychological tests and functional magnetic resonance imaging (fMRI) offer a peek into the inner workings of the aging brain.
The first study, led by William von Hippel from the University of New South Wales in Australia, attempted to figure out why some older people speak out with what appears to be a complete lack of tact.
Psychological tests showed that instead of just being downright rude, many older people have lost their inhibitory ability and may not even realize they're being rude.
"The normal aging process leads to changes in the brain that have social consequences. These brain changes often do not affect intelligence, but they can affect other aspects of mental functioning, like inhibition. Thus, even older adults who are as sharp as a tack may say things that embarrass or upset us, without intending to do so," explained von Hippel, who is an associate professor of psychology.
"We all think inappropriate things, and we can't be faulted for that. Perhaps aging just leads us to say more of them, and so perhaps we shouldn't be faulted for that, either," he added.
Von Hippel's study appears in the September issue of Psychology and Aging.
The second study, led by Dr. Adam Gazzaley from the University of California, San Francisco, used fMRI to compare the recall abilities of older people and younger people. Gazzaley and his team found that rather than lose the ability to recall with age, people lose the ability to filter out irrelevant information.
"Although older people were able to focus on what was important, they were also still focusing on the irrelevant, and that was causing them to remember less well," said Gazzaley, an assistant professor of neurology and physiology.
The findings appear in Nature Neuroscience.
Both Gazzaley and von Hippel believe changes in the frontal lobes may be behind these changes in behavior and ability.
In von Hippel's study, 41 people between the ages of 18 and 25, and 39 people between the ages of 65 and 93 agreed to undergo psychological testing. During one part of the test, the researchers inserted deliberately fake questions, such as "What color are a tiger's spots?" Or, "How many animals of each type did Moses bring on the Ark?"
The study participants were forewarned that the fake questions would be a part of the test. Properly answering these questions required them to inhibit the answer they believed the tester was looking for, and point out that the question was a fake.
The study participants were also asked how likely they would be to share personal information or ask people for personal information in public situations, such as inquiring how someone's hemorrhoids were doing during a public meal.
According to von Hippel, the older participants were about 20 percent more likely to ask personal questions in public, and a small minority of older adults were twice as likely to ask personal questions in public. He said he suspects that this behavior may be caused by age-related losses in inhibitory ability.
"These data suggest that it's clearly not something all older adults do, but they also suggest that there is a sizeable percentage of older adults -- about one-third in our sample -- who are likely to do so," said von Hippel.
However, these findings don't mean that perennial foot-in-mouth disease is solely the realm of older people. Young people, he said, can -- and do -- make embarrassing blunders. Everyone is much more likely to have lapses in judgment when they're distracted, stressed or tired, von Hippel noted.
For his study of aging memory, Gazzaley and his colleagues compared 17 young adults between 19 and 30 years old to 16 people between 60 and 77 years old. All of the study participants were shown pictures of faces and pictures of nature scenes as they underwent fMRI to see which parts of their brain were active during the task.
Sometimes, they were asked to remember the faces and not the scenes, and other times they were asked to remember the opposite information.
When recalling the scenes, an area in the left brain was activated in both the young and old participants. However, when told to ignore the scenes, activity in that area of the brain was reduced in the younger participants, yet remained active for most of the older participants. That suggests that older people are less able to suppress irrelevant information, according to Gazzaley.
The good news from Gazzaley's study is that these changes weren't universal. Some older folks didn't have trouble suppressing irrelevant information.
"There was a sub-population that was able to remember and didn't have suppression deficiency. These people were able to perform like younger subjects," Gazzaley said.
That means, he added, "that somewhere in here is a clue to successful aging."
To learn more about the aging brain, read this article from the University of Southern California.