Under the Hood

Brain Plasticity Does Not Decrease With Age; Filtering Out Irrelevant Details Is The Problem

old dog
Older adults possess the ability to learn, but they do not filter out irrelevant information as well as their younger peers. Photo courtesy of Shutterstock.

You can’t teach an old dog new tricks. Turns out, they're wrong and a new study disproves this obsolete notion. Older adults, a team of Brown University researchers found, possess the ability to learn; however, they do not filter out irrelevant information as well as their younger peers. It seems we learn more than we need to as we age, and that’s a problem.

“What older people need to do is to learn a skill to avoid learning what is not necessary,” said Dr. Takeo Watanabe, the Fred M. Seed Professor at Brown and co-author of the newly published study.

For some time now, scientists have believed that as time passes our adult brains lose plasticity or the ability to reorganize neural pathways and so accommodate new information derived from our experiences. Essentially, then, plasticity is the ability of the brain to change itself based on new input. Not a simple process, plasticity consists of several different activities involving various types of brain cells, which in some cases modify themselves internally as well as externally. Because it is a complex process, the Brown research team wanted to explore what happens to plasticity with the ravages of time.

Plasticity vs. Stability

Watanabe and his co-researchers began their exploration by enlisting the help of 10 people between the ages of 67 and 79 and another group of 10 people between the ages of 19 and 30. After taking a pre-test, participants trained for eight days on a simple visual exercise, and then on the ninth day, they took a post-test. The card-based exercise consisted of four letters and two numerals set in a background of moving dots. Essentially, participants watched the symbols pass in a particular sequence and then they reported what they saw. During training, the researchers instructed the participants to observe the numerals. However, in both the pre- and post-tests the researchers also asked the volunteers to report the direction of dot movement behind the numerals.

The older people improved as much as younger people on correctly identifying the numeral sequence. “No evidence was obtained that indicates that older individuals have a problem with plasticity,” the authors noted in their published study.

When it came to discerning the direction of dot movement, older people learned that, too. Younger people, contrarily, only showed improvement on perceiving movement when it was subtle; while they recognized obvious movement, seemingly they simply ignored it as insignificant information.

This dissimilarity between old and young people suggested to the researchers a difference in attention skills. So, they subjected the volunteers to a test to measure selective attention ability. Here, the older adults did notably worse than their younger peers; they could not filter out irrelevant stimuli as well. Importantly, the poorer their ability to filter, the more irrelevant stimuli participants learned. This brain ability is what neuroscientists call stability: high stability allows your brain to sort through new stimuli and store only the important items while processing out any unimportant details.

For older adults — you, too, will be there someday (if you're lucky) — Watanabe believes this ability to filter might be improved with training. “Our learning and memory capability is limited,” Watanabe said. “You don't want older, existing important information that is already stored to be replaced with trivial information.”

Source: Watanabe T, Chang LH, Sasaki Y, Shibata K. Age-related declines of stability in visual perception learning. Current Biology. 2014.