College of LAS « Illinois

Research

Good Memories

The inevitable declines in memory that accompany aging may not be as bad as we all think. LAS researchers are discovering ways to keep memory loss at bay.

Illustration of gray matter

Dorothy DiIorio, a ’49 LAS alumna, has watched many friends and acquaintances lose contact with life as their memories fade and their ability to make new ones becomes painfully difficult. Losing a key part of what made them vital individuals was a heartbreaking sight, and one DiIorio was determined to avoid when she retired 10 years ago. That’s why she began exercising every day and staying active.

It’s a regimen that researchers in LAS confirm may hold a key for remaining mentally sharp.

We’re at our mental peak when we’re young, according to conventional wisdom; and as the years pass, it’s a slow, steady, and inevitable downhill slide. This disheartening perception, though, is not necessarily reality, say LAS researchers.

As evidence, a team led by LAS psychology professor Arthur Kramer was the first to use high-resolution magnetic resonance imaging to show anatomical differences in the brains of physically fit and less-fit, aging people. These scans showed that cardiovascular exercise preserved regions of the brain’s gray matter, the layers of tissue and support cells critically involved in learning and memory.

Kramer and U of I kinesiology professor Ed McAuley also showed that moderate exercise—something as simple as 45 minutes of walking each day—could reverse age-related brain deterioration and even increase brain volume in older adults.

“Ten years ago, you would never have expected to see this in older adults,” Kramer says.

Kramer’s work is only one piece of an extensive network of LAS research that is probing the mysteries found deep within the three-pound nerve center of the human body—the brain. In fact, the U of I has become a nerve center in its own right, known worldwide for its research on memory and aging.

Even as long ago as the 1970s, LAS researchers were dispelling long-standing myths about memory. At that time, the scientific community believed the human brain was immutable. But psychology professor William Greenough proved that the brain literally changes in response to new stimulation, opening up a whole new world for researchers. The result was the groundbreaking concept of brain function known as plasticity, or the brain’s ability to change its function and structure on the basis of new experience.

Greenough’s research, which showed that the brain is similar to a muscle that can be built up through use, has produced reforms in many fields, from early learning to neural biology. In terms of memory, his discovery of brain plasticity has led to new studies showing that people can enhance their cognition by exercising both their minds and bodies.

Memory, the sum of our experiences, is the glue that holds each individual personality together. And as longevity has increased, people, particularly aging baby boomers, have grown increasingly concerned with maintaining their mental edge.

But U of I psychology professor Paul Gold says that the decline in memory with age “isn’t as dramatic as the public believes. Benign aging is probably nothing that interferes with lifestyle. I can’t run as fast as I used to run. But I still do it, and it’s the same thing with memory.”

In creating memories, information entering the brain is transmitted by neurons, the nerve cells that make up the brain and serve as signaling units. Each neuron connects with other neurons through physical junctions called synapses. The brain contains up to 1,000 trillion synapses, storing memories in this intricate biological power grid.

It was once believed that brains do not create new neurons, but that notion has long been discredited. What’s more, brains do not lose as many neurons with age as was once thought, says psychology professor Donna Korol.

According to Korol, there is generally some shrinking of the brain with age, particularly in the frontal cortical areas, perhaps because of decreased white matter volume, less blood flow to the brain, or other factors. However, she says, “though there seems to be some reduction in volume, there is not a substantial loss of neurons, which is a bit counter to the dogma about old brains.”

Memories are divided into categories. A short-term memory, like that of the telephone number of a local pizzeria, can last only as long as needed to make the call, say 15 to 30 seconds, and then disappear. But the more frequently a customer calls that pizza restaurant, the more likely the telephone number will be remembered.

Long-term memory is further subdivided into categories—declarative memory for facts, faces, or places that have grown familiar, and procedural memory for muscle memory, like that involved in activities such as typing or riding a bicycle. Declarative and procedural memories are processed by separate areas of the four lobes that make up the cerebral cortex.

A third category of long-term memory is the so-called “flashbulb memory,” a memory associated with a traumatic event like a presidential assassination or a personal event like an engagement or a wedding.

Age-related memory change begins in people around 35 to 40, but that’s not necessarily a negative. Former LAS professor Denise Park, who is now at the University of Texas at Dallas, says her research has shown that as an individual’s ability to process information slows with age, the individual’s “knowledge base,” which is necessary for good judgment, grows through experience in life and can only come with the passage of time.

It seems the aphorism that wisdom comes with age has a scientific basis.

“That’s why we don’t have 20-year-olds running the world, even though the data clearly show that 20-year-olds are better at processing information,” Park says.

However, that optimistic view might be a tough sell to older people who experience memory changes they associate with decline.

Gold described one difficulty as “a tip-of-the-tongue problem,” a processing issue that refers to circumstances when people can’t put a name with a familiar face or provide answers to questions they should know.

Another, he says, is “rapid forgetting,” which stems from difficulty storing new information. Gold attributes “rapid forgetting” to a decline in the production of an arousal hormone that helps seal a memory in the brain. If an event is mundane, the mind is not aroused, the hormone is produced at a lower rate, and the memory is lost.

“So if nothing arouses the brain, we don’t remember as well,” Gold says.

Other hormones, such as estrogens, also play a role in memory, says Korol. Studies in rats show that as estrogen levels rise across the reproductive cycle, the number of synapses also rises; and when estrogen levels plummet, the number of synapses declines. This raises the question of what happens to learning and memory when an aging woman’s estrogen levels drop after menopause.

Korol found that while some learning strategies decline as estrogen levels drop, other learning strategies actually improve. For example, rats with low estrogen levels were better at remembering the route to food by using a “stimulus-response” strategy, in which they used either a single right or left turn. But they were worse at remembering the route to food when they used a “place strategy”—following the configuration of cues in the environment, such as the layout of posters and bookcases in the laboratory.

For rats given estrogen, the effectiveness of the learning strategies was reversed.

“The assumption is that aging leads to a decline in learning and memory,” Korol says. “But I am a believer that with age come changes in information processing. Some changes are for the better and some for the worse, similar to that seen following estrogen treatment.”

Korol also says that memory is more than just a strengthening of the synapses. Sometimes the formation of new memories calls for a weakening of synapses. She compares it to sculpture, which requires an artist to remove material to create the desired shape.

“So I don’t think forgetting is all bad,” Korol explains. “We need to forget certain information in order to form new frameworks. If you remembered everything you were exposed to, you wouldn’t be able to function.

“I like what a student of mine once wrote on a midterm exam,” she adds. “He said, ‘Old brains are not necessarily bad at remembering. They’re just good at forgetting.’”

By Jim Dey and Doug Peterson
Winter 2008