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Can twins unlock brain science secrets?

Successful aging is not a passive sport. For example, genes are only about 50 percent responsible for our memory. It's believed the other half is determined by environment and behavior. Researchers at UCSD are looking for proof in the brains of twins. Rebecca Tolin has the story.

Mark Page, Twin Study of Aging Participant: "You have to remember the last word..."

Mike Page, Twin Study of Aging Participant: "Yeah, yeah, yeah."

Mark: "Oh, man!"

Mike and Mark Page have always had a close bond. The twin brothers were best friends as children. To this day one can finish the other's sentence.

Mike: "When she got down to two sentences..."

Mark: " two, then I could do it."

Mike: "That was great."

Mark: "We're very similar. I can't remember having a disagreement with him since we were young kids."

Mike: "We have a lot of similarities in thinking; we have same likes and dislikes. He's my main soul mate in that sense."

Now 52, both men have followed a similar life pattern, even getting married the same year.

Mark: "I've been married 28 years and I have 2 children."

Mike: "I'm married for 28 years to the same woman. I have a son and a daughter."

But there are distinct differences between the two. Mike works as a high school band leader. Mark a system administrator for New York City Transit. Basically, Mike is musical.

Mike: "Believe it or not, I play guitar."

Mark is scientific.

Mark: "I'm into science as a hobby."

But what makes them different genes or environment?

Researcher: "Back to work."

Scientists at UCSD are trying to find out.

Bill Kremen, Ph.D., UCSD School of Medicine: "The reason we're using twins really comes down to a question that's been something that people have been interested in for centuries. What in human beings is due to nature versus nurture?"

Bill Kremen is lead researcher for the twin study of aging. So far some 500 twin pairs have been tested in three basic areas: cognition, personality and health.

Researcher: "Turn!"

All the subjects are between 51 and 59. They don't yet show many age-related declines, but could in the near future. That's why researchers will re-test them every five years. Some pairs like the Page brothers are fraternal, sharing only 50-percent of their genes. Other twins are identical with an exact genetic match.

Kremen: "So one shares exactly double as what the other shares. And what that tells us is if identical twins are more similar on a certain characteristic than fraternal twins, that means that genes have to be important in influencing that characteristic."

Twins will help researchers solve the aging puzzle.

Kremen: "I want you to do exactly what I do now, touch the blocks I touch in the same order."

Meanwhile, Mark and Mike are grappling with a memory puzzle. They're asked to touch the unlabeled blocks in the same pattern as Kremen.

Kremen: "This time when I stop I want you to touch the blocks backwards."

Then, backwards which tests the brain's ability to re-organize information. Kremen says this spatial span exercise challenges the short-term or 'working memory'. Researchers will then use MRI scans to compare cognitive function with brain anatomy.

Kremen: "So in this case what we would be interested in seeing are changes in the frontal lobe, perhaps shrinkage in the frontal lobe, with age, related to changes in this kind of memory test. And in fact the evidence shows that the frontal lobe is an area that shows the greatest amount of shrinkage with age."

Cutting edge scans measure the mass of individual parts of the brain. If the hippocampus shrivels over time - as it does in Alzheimer's - researchers can compare how twins' environment and behavior affected change in the brain. Researchers used to think the brain was static after we're born, but they've learned the brain continues to grow new connections throughout our lives. The kind of connections depends in part on our habits, say reading a book versus watching TV.

James Brewer, M.D., Ph.D., UCSD School of Medicine: "If you're an elderly person and you're continuing to tax your mind and trying to continue to work hard at something, we have strong evidence that your brain is actually changing and adapting and actually becoming more efficient at that behavior. And that may, there is some evidence that it may be protective against Alzheimer's Disease."

Jim Brewer says there's some scientific evidence to show mental activity and social interaction may actually buffer the brain from dementia-related decline. He hopes the twin study will provide further proof. But as a neurologist, he's confident activity is good for the brain and the blood vessels that feed it.

Brewer: "What this study may provide is the ability to tell the public hey, your behavior is important for your brain health. Okay, not only do your genes determine whether you're going to have a very healthy brain, but your behavior determines it as well. So it's very important to stay very active, it's very important to avoid smoking, it's very important to avoid alcohol use."

Brewer says the brain is an efficient organ, what you abuse or don't use, you lose. When asked separately, both Mike and Mark Page observed lower priorities seem to slip away.

Mark: "I think I have selective memory. I tend to remember what is important, and things I guess that my brain doesn't think are important, I don't hold onto too long."

Mike: "I tell my friends I have a selective memory. Things I really need to remember, I remember. Things that I feel are kind of not necessary, I don't remember."

Like many of us, both long for that elusive photographic memory. How to at least retain what we have is the question that drives Dr. Kremen.

Kremen: "Obviously memory, brain function, is very important to our functioning in the world and our quality of life. And if we can learn more about what are the predictors of those things and help thereby people to age more successfully, that would be a very valuable contribution."

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