Older Brains Keep Plasticity, but there is a Problem
The consensus among brain scientists is that our brains lose flexibility, or “plasticity” as we age.
Now, a new study has found older learners retained the mental flexibility necessary for a visual perception task. The results undermine the conventional wisdom, but there is one problem.
The older learners were not as good as younger people at filtering out irrelevant information.
This suggests that learning may become harder as people age because they learn more than they need to.
“Plasticity may be kept okay, in contrast with the view of many researchers on aging who have said that the degree of plasticity of older people gets lower,” said Brown University professor Takeo Watanabe, study corresponding author. “However, we have found that the stability is problematic. Our learning and memory capability is limited. You don’t want older, existing important information that is already stored to be replaced with trivial information.”
Brain Plasticity and Stability Dilemma
Researchers are calling it the plasticity and stability dilemma.
“We think that the degree of plasticity in the cortex gets more and more limited with older people,” said Watanabe. “However, they keep the ability to learn, visually at least, by changing white matter structure.”
The study, Watanabe involved one group of 10 people 67 to 79 years old and another group of 10 people ages 19 to 30. The groups trained on a simple visual exercise over a nine day period.
Shown a quick sequence of six symbols, consisting of four letters and two numerals, the volunteers were asked to report the numerals they saw. Performance on a test at the end of training was compared to their score on a pre-test.
The results of the test were clear. Older people got better as much as younger people on the core task of identifying two numerals.
“These results indicate that older subjects as well as younger subjects showed significant amounts of task-relevant learning,” according to the authors. “No evidence was obtained that indicates that older individuals have a problem with plasticity.”
Too Much Information
The most obvious signals were the most easily filtered, suggesting that the difference between older and younger learners was an issue of attention.
So researchers had the volunteers undergo another test to determine the ability to find an applicable stimulus amid a number of distractions. Older people did markedly worse than younger ones.
This adds evidence that the attentional systems for filtering out irrelevant stimuli were indeed weaker in older learners. Significantly, the worse an older subject was at filtering out irrelevant stimuli, the more irrelevant stimuli the subject learned.
The results, Watanabe says, are not necessarily discouraging. Filtering ability could perhaps be improved with some kind of cognitive training.
“The hope is that maybe what older people need to do is to learn a skill to avoid learning what is not necessary,” he said.